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The emergence of Cochlodinium along the California Coast (USA)
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Harmful Algae 7 (2008) 337–346 www.elsevier.com/locate/hal
The emergence of Cochlodinium along the California Coast (USA) Casey C. Curtiss a,*, Gregg W. Langlois b, Lilian B. Busse c, Fernanda Mazzillo a,c, Mary W. Silver a,d a Department of Ocean Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA California Department of Health Services, Environmental Management Branch, 850 Marina Bay Parkway, Richmond, CA 94804, USA c Integrative Oceanography Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA d Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA 95039, USA b
Received 27 October 2006; received in revised form 4 April 2007
Abstract A sudden and nearly synchronous emergence of the red tide forming dinoflagellate Cochlodinium along more than 800 km of California coastline was initially observed in late summer 2004. Thereafter high cell concentrations have been detected on an annual basis. Here, we present quantitative and semi-quantitative data indicating that Cochlodinium was uncommon in the phytoplankton community in California prior to 2004 and is now persisting as a more regular component and one that seasonally can cause red tides. The quantitative portion of this study was primarily conducted in Monterey Bay, where cell densities reached at least 6 104 cells L1 during the initial outbreak. A semi-quantitative comparison of California coastal counties by the California Department of Health Services (CDHS) was also made: of the 15 counties surveyed (most with multiple sites per county), cells were detected only from Los Angeles County in the south to San Mateo County in the central region (seven counties), but not in the northern part of the state (six counties). Two counties in the central region of the state, San Luis Obispo and Santa Cruz, displayed intense and frequent periods of elevated Cochlodinium cell abundances. Although not observed in the state-wide CDHS survey, we occasionally found cells in San Diego County with densities up to 2.7 104 cells L1. Though these colonial dinoflagellates have been recognized in California for over 80 years, with several ‘‘blooms’’ recorded prior to 2004, the species’ geographic range and abundance in recent years suggest significant shifts in the nearshore phytoplankton community of this region of the eastern Pacific. # 2007 Elsevier B.V. All rights reserved. Keywords: California Coast; Cochlodinium; Dinoflagellate; Monterey Bay; Red tide
1. Introduction Harmful bloom events caused by the athecate, chainforming dinoflagellate Cochlodinium have been increasing in frequency in coastal waters around the world’s oceans. Much of the attention has been focused in regions of the western Pacific including Korea, Japan and, to a lesser extent, China (Yuki and Yoshimatsu, 1989; Qi et al., 1993; Kim, 1998; Lee et al., 2001; Cho and Costas, 2004; Lee, 2006; Matsuoka et al., 2006), which have experienced substantial economic losses as a result of this organism’s deleterious effects on fish stocks (Onoue and Nozawa, 1989; Yuki and Yoshimatsu, 1989; Kim, 1999; Whyte et al., 2001a,b). To date, no toxic mechanisms have been confirmed. Blooms of this dinoflagellate have also been noted
* Corresponding author. Tel.: +1 831 459 2948; fax: +1 831 459 4882. E-mail address: [email protected] (C.C. Curtiss). 1568-9883/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.hal.2007.12.012
along the coast of the eastern Pacific (Costa Rica, Mexico) and the Caribbean (Puerto Rico) (Margalef, 1961; Morales-Blake et al., 2001; Ga´rate-Liza´rraga et al., 2004; Lara, 2004; VargasMontero et al., 2004). There have been occasional reports of Cochlodinium on the California Coast and discolored surface water caused by this organism was noted in 1964 (Holmes et al., 1967). This report presents new data on Cochlodinium and its apparently rapid emergence along the California coastline, where it appears to have become a common component of the phytoplankton. We also assemble a variety of records that indicate Cochlodinium was not seen with any regularity along the state’s coastline until 2004. The lack of data on the organism along the California Coast may be a result of its infrequency in the past, may reflect the potential difficulty of recognizing older, preserved specimens, or it may also indicate that cells in this genus, especially in low numbers, could be confused with other chain-forming dinoflagellates, particularly Alexandrium
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species, much better known in the region. In this paper, we use the designation ‘‘Cochlodinium’’ for the organisms: the designation of the photosynthetic species of Cochlodinium in California is not entirely clear, but some specimens from Monterey Bay, and possibly elsewhere on the western N. American coastline, belong to the newly described C. fulvescens (Iwataki et al., 2007) (see Iwataki et al., this issue). 2. Materials and methods This report on Cochlodinium along the coast of California, USA was assembled from multiple data sources available to the authors from several ongoing coastal studies. The main research objectives of all investigators involved differ to some extent; hence, these groups used different sampling schedules, covered various temporal and spatial scales, and performed phytoplankton analyses that were either quantitative or semiquantitative. Researchers from the University of California, Santa Cruz (UCSC) were focused on the Monterey Bay area, whereas the Scripps Institution of Oceanography (SIO) group concentrated on the San Diego Region, and the California Department of Health Services (CDHS) project encompassed the entire coastline from the California/Oregon Border (Del Norte County) to the California/Mexico Border (San Diego County) (Fig. 1). 2.1. Monterey Bay sampling, 2004–2005 Water samples for quantitative measures of cell abundance were collected by the UCSC group from January 2004 to February 2005 at the Santa Cruz Wharf (SCW) and from January 2004 to December 2004 at the offshore Monterey Bay Aquarium Research Institute (MBARI) M1 mooring site, approximately 20 km offshore of Moss Landing and over 1000 m water depth (Fig. 1). Sampling was performed once to several times per week
at the SCW site, depending on whether blooms were present, while the M1 site was sampled once weekly, ship access permitting. Water samples at both sites were collected by surface bucket, which provided sub-samples for cell enumeration. At SCW, surface seawater samples were collected and sub-sampled for salinity analysis and cell counts. Water temperature was measured with a digital thermometer immediately upon collection. Additionally, a net tow (35 mm mesh) sample was obtained by hauling the net five times from 3 m depth to the surface. Net tow material was examined in the laboratory using a dissecting microscope (Olympus SZH Stereozoom) to characterize the planktonic community and a record kept of species observed in each sample. Water for salinity analysis (conductivity) was prepared by filtering200 mL through a 25 mm Whatman GF/F filter and tested using a portable salinometer (Guildline Portasal mod. 8410). Aliquots of 100 mL were preserved in 4% formaldehyde for cell enumeration. Water samples were collected at the M1 station (R/V Pt Lobos; MBARI) and then transported to UCSC, where aliquots were either fixed (see above) or examined live to characterize the dominant netplankton. Temperature and salinity data for M1 water samples were obtained from MBARI’s on-line database (http://mbari.org/). Cell abundance for samples collected both at SCW and M1 was quantified using the Utermo¨hl method (Utermo¨hl, 1958). Initially, a 50 mL aliquot of preserved water samples was settled for a minimum of 24 h prior to examination. For samples found to contain dense populations of Cochlodinium, 10 mL aliquots were settled and individual cells of Cochlodinium were then counted on an inverted microscope (Olympus IMT-2). 2.2. Archival samples from Monterey Bay, 2001–2006 To assess the possible occurrence of Cochlodinium in Monterey Bay during likely bloom periods in additional years, fixed (4% formaldehyde) samples were observed from net tow
Fig. 1. (a) Map of Monterey Bay, California, showing locations where field samples were collected (M1 and Santa Cruz Wharf); (b) Coastal counties of California showing the geographical regions (shaded) with reported Cochlodinium since the initial 2004 outbreak.
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material obtained at SCW from June 2001–September 2006 using light microscopy. A semi-quantitative analysis of cell abundance in these net collections was made using a ranking system of visually estimated biovolumes: ND (non-detect) – no cells; Present – 1–9%; Common – 10–49%; Abundant – >50%. 2.3. California sampling by county: the CDHS data set Phytoplankton net tow samples (100 mL) were collected in 15 California coastal counties from Del Norte County in the north to San Diego County in the south by a volunteer monitoring network managed by the CDHS Marine Biotoxin Monitoring Program. Collections were made at one or more sites in each county and all samples were analyzed by CDHS. Sampling frequency varied by site and typically ranged from weekly to bimonthly. Plankton tows, conducted primarily from nearshore locations (piers, docks) and, to a lesser extent, from boats, were collected using a 1 m long, 25 cm diameter, 20 mmmesh net and the total tow effort (tow distance) noted. The sampling effort was standardized to vertical tows of 3–10 m depth and entailed multiple vertical retrievals of the net (typically 3–5). Material was preserved using approx. 1% formalin (final concentration) and immediately shipped to CDHS for analysis. All samples were settled prior to observation by phase contrast microscopy (Zeiss Axiskop 2+ or Leitz Ortholux) and examined to describe phytoplankton species assemblages. All genera identified were recorded and an estimate of percent composition generated. In addition, a volumetric estimate of the settled cell mass was recorded, excluding any contribution from detrital matter. Because sampling effort and settled cell mass varied between samples and sampling sites, an attempt was made to normalize the percentage composition data for each species by calculating a Relative Abundance Index (RAI). The RAI, devised by CDHS (Langlois, 2004), is based on estimates of (a) overall biomass of cells in the net tow as determined by settled cell volume; (b) the percent composition by biovolume of each genus (in that volume of phytoplankton material); and (c) the sampling effort as determined by the total tow length: RAI ¼
ða bÞ c
The RAI provides a means of normalizing qualitative data to yield a semi-quantitative measure of the biovolume for a given genus of net plankton. This technique standardizes the effects of filtering different volumes of water (i.e., tow length) and the relative contribution of various genera in samples taken along the California coastline. 2.4. San Diego County sampling Surface water samples were collected from 1992 through 2000 by personnel from Scripps Institution of Oceanography (SIO, La Jolla, CA) at their pier using a Niskin bottle. Samples were fixed in 4% formaldehyde, archived, and evaluated at a later date (2002–2003). From October 2003 through July 2006, samples were obtained at the SIO pier by surface bucket and
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vertical net tows (20 mm mesh) between approximately 3 m and the surface. Between October 2003 and October 2005, only semi-quantitative observations from the archived net tow samples were conducted using a ranking system similar to that outlined above (i.e., present, common, dominant). Beginning in October 2005 through July 2006, phytoplankton community composition was determined and quantitative cell counts (Utermo¨hl method) performed as described above. 3. Results 3.1. Cochlodinium in Monterey Bay Cochlodinium (Fig. 2a, d and e) occurred frequently in Monterey Bay both as single cells and in colonies typically of 2–4 cells (Fig. 2e), but occasionally in chains up to eight cells long (Fig. 2a). The cells, usually deep gold-brown when viewed by light microscopy, caused the water to appear muddy brown to reddish when abundant. Chloroplasts were granular and appeared to be distributed around the cell periphery (Fig. 2f). Individual cells (Fig. 2) ranged from approx. 25–50 mm in length and 20–40 mm in width and were typically spherical to slightly ellipsoid (compressed dorso-ventrally). The cells swam about vigorously in freshly collected field samples and no temporary cysts were observed when examined at higher power. The locomotion was characterized by smooth, looping spirals with a minor wobble associated with the forward motion. The cells were sheathed in irregular, mucus-like material at the surface, which sometimes tended to disintegrate after storage in formaldehyde (Fig. 2d) thus making them less readily distinguishable in samples stored for extended periods, especially if the observer was not familiar with the organism. In our study, samples up to at least 10 years of age contained recognizable Cochlodinium cells, but there was clearly some degradation that could result in underestimates of cell abundance. When viewed under low magnification, Cochlodinium could be confused with cells of Alexandrium catenella (Fig. 2b and c). Both are chain-forming dinoflagellates of similar size, but there are several distinguishing characteristics. Cochlodinium is athecate and encased in an extracellular matrix of mucilage, which is apparent under light microscopy. The cells are spherical to slightly ellipsoid. In contrast, A. catenella is thecate, displaying very noticeable thecal plates and a distinct cingulum. While Cochlodinium also exhibits a cingulum, it is typically much less apparent. The cells of A. catenella are also anterior-posteriorly compressed as compared to those of Cochlodinium, which are dorso-ventrally compressed. The quantitative part of the study in Monterey Bay at SCW (Fig. 3a) and the offshore M1 site (Fig. 3b) was focused on the time period between the major appearance of Cochlodinium in summer 2004 until February 2005 and December 2004, respectively. Samples also were examined for the interval between January 2004 and early June 2004, when no cells were detected at either of these sites. Cochlodinium was first observed at the M1 site (24 June 2004) and subsequently at the SCW site (6 July 2004). Over the duration of the 2004 bloom, maximal cell densities at M1 reached 3.3 104 cells L1 (4
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Fig. 2. Photomicrographs of Cochlodinium and Alexandrium catenella collected from Santa Cruz Wharf (SCW) and Scripps Institute of Oceanography (SIO) pier. (a) Eight cell chain of freshly preserved Cochlodinium (SCW); (b) eight cell chain of preserved A. catenella (SCW). Note similar morphology to Cochlodinium; (c) Four cell chain of A. catenella (SCW). Note pronounced theca and cingulum; (d) Cochlodinium after extended period of preservation in 10% formaldehyde solution (SCW). Note disintegration of the cells; (e) doublet (two cell chain) of Cochlodinium sp. from live sample (SCW); (f) chloroplasts visible under fluorescent microscopy (SCW); (g) four-cell chain of preserved Cochlodinium from SIO Pier. Scale bars = 40 mm.
November 2004) and 6.0 104 cells L1 at SCW (21 September 2004). These may be underestimates, as some cells become difficult to identify when preserved (see above). The offshore M1 mooring site generally had lower cell densities and cells were less frequently observed there than at SCW. Cochlodinium persisted beyond the sampling period at both sites, as described below. When Cochlodinium was present, and especially when abundant, vacuum filtration was slowed and the volume collected was limited due presumably to the presence of colloidal materials associated with the cells. The temperature and salinity conditions from summer 2004 through January 2005 during which Cochlodinium were found are shown in Fig. 3a and b, along with the conditions when ‘‘blooms’’ (here defined as > 104 cells L1) occurred. During the blooms, temperatures were at or above 14 8C and salinities
between 33 and 34 psu, though several substantial events occurred at salinities as low as 32 psu at SCW (27 July 2004, 30 July 2004). All events of > 3 104 cells L1 were found at temperatures above 14 8C; nonetheless, significant cell numbers (>1.5 104 L1) were observed down to 12.8 8C at both sites and cells were detected at temperatures as low as 11.2 8C (SCW, 28 December 2004). Further, qualitative observations at both SCW and M1 demonstrated Cochlodinium’s presence subsequently from July 2006 through October 2006, sometimes dominating the net phytoplankton (Table 1). Archived samples (2001–2003) were examined to determine whether cells had been present in net tows from SCW before the major 2004 Cochlodinium event (Table 1). No cells were observed in samples obtained during summer and fall, when oceanographic conditions would be expected to favor the
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Fig. 3. Temporal variations of Cochlodinium cell abundance, temperature (8C), and salinity (psu) for (a) Santa Cruz Wharf (SCW) and (b) offshore M1 mooring site (operated by Monterey Bay Aquarium Research Institute) for 2004–2006.
presence of Cochlodinium. This finding is supported by ongoing records produced by both the UCSC group and CDHS that document phytoplankton assemblages from live water samples. 3.2. Cochlodinium from Del Norte to San Diego County: the CDHS data set During the sampling period (January 2004–July 2006), phytoplankton assemblages were evaluated from each of the Table 1 Cochlodinium during optimal bloom period from 2001 through 2006 using archived net tow material collected from the Santa Cruz Municipal Wharf and the offshore M1 site, Monterey Bay Year
June
July
August
September
October
November
2001 2002 2003 2004 2005 2006
ND ND ND ND P ND
ND ND ND A C P
ND ND ND A P A
ND ND ND P C P
ND ND ND A C A
ND ND ND A P n/a
ND, not detected; P, present; C, common; A, abundant.
coastal counties in California (>3,250 individual samples, 168 unique sampling sites). Counties where Cochlodinium was observed are shown in Fig. 4a and b. The six northerly counties (Del Norte to San Francisco) and San Diego County in the south, though heavily sampled, and the less frequently sampled Orange County, also in the south, showed no evidence of Cochlodinium from net tows obtained over this time period (data not shown). The appearance of substantial numbers of Cochlodinium in Monterey Bay during summer 2004 coincided with its appearance over a very large extent of central and southern California during approximately the same time period (Fig. 5). Outbreaks occurred in late summer to early fall of 2004 and Cochlodinium populations persisted through much of the winter and then declined. Records from the subsequent year (2005) were similar, with high cell abundances observed during essentially the same time in summer and fall. San Mateo County, the most northerly site at which Cochlodinium were found, had the fewest observations, though they did occur here during the widespread coastal blooms of both 2004 and 2005. Cochlodinium populations were most frequently observed in Santa Cruz (SC) and San Luis Obispo (SLO) counties over the study period; however, these two
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Fig. 4. Cochlodinium distribution for (a) Central Coast region and (b) southern California region by county (CDHS data). Coastal counties that experienced no observable cells are omitted. Symbols are same as for Fig. 5.
counties were also the most frequently sampled. Both counties clearly displayed peak bloom periods in the late summer (July and August, 2004), which persisted through much of the winter. Populations in Monterey (situated between SC and SLO counties) and Santa Barbara (directly south of SLO) counties also had increased cell abundance during the late summer–early fall (August and September) of 2004 and 2005, but were less dense than those in SLO and SC counties. Cochlodinium was also found in Ventura County (winter 2005 through summer 2006), but data were not collected during the 2004 event. No
Cochlodinium cells were noted in Los Angeles County until spring (March) of 2005. The dinoflagellate occurred again in summer (June) and during late fall (November) of 2005, and continued through the winter at this location. 3.3. Cochlodinium in San Diego County At the time of the initial emergence of Cochlodinium along the central and southern California Coast in 2004, cells were observed on only one occasion from the SIO pier (11 November
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4. Discussion 4.1. Historical record of Cochlodinium along the California Coast, prior to 2004
Fig. 5. Cochlodinium distribution along California coastline (Del Norte – San Diego). All coastal counties were surveyed. Percent composition and RAI are for net plankton-sized phytoplankton (see text for details).
Fig. 6. Observed Cochlodinium at Scripps Institution of Oceanography (SIO) pier during a period of elevated cell densities January 2006–July 2006.
2004; L. Busse, pers. obs.). Cells were not detected again until October 2005 when Cochlodinium was found in net tow samples at low concentrations. Elevated concentrations were detected on 23 January 2006 (7.8 103 cells L1), coinciding with the initial stages of a red tide event that persisted through May 2006 (Fig. 6). During this event, Cochlodinium cooccurred with Prorocentrum micans, Akashiwo sanguinea, and an unidentified Gymnodinium sp. Maximal cell densities of Cochlodinium reached 2.7 104 cells L1 (20 March 2006) and salinity ranged between 33 and 34 psu during the time of elevated cell numbers. Temperature dropped below 14 8C on 13 March 2006 and was lowest (12.7 8C) at the peak of the bloom (20 March 2006). Cells collected from the SIO pier (Fig. 2g) exhibited morphology similar to cells observed in Monterey Bay (Fig. 2a). Archived samples from 1992 through 2000 showed that Cochlodinium were occasionally present but generally below 5 103 cells L1. However, on two occasions, elevated densities of Cochlodinium were noted at SIO pier – in 1994 (6.6 104 cells L1 on 22 April 1994) and in 1998 (6.3 104 cells L1 on 23 April 1998).
The emergence of Cochlodinium as a common bloomforming organism in regions along the California coastline appears to be a recent phenomenon. However, taxonomic uncertainties about the organism have made historical analysis difficult. This genus does not appear to have received much attention since early analyses of California species of the genus by Kofoid and Swezy (1921) showing that Cochlodinium occurred off San Diego. A later report by Holmes et al. (1967) documented a red tide in La Jolla Bay, San Diego in May 1964, with the causative organism being a Cochlodinium species. In our survey of material dating back to the 1990s, we found that Cochlodinium was occasionally present, mostly at low abundance, at the SIO pier in La Jolla between 1992 and 2000. Reports of Cochlodinium north of San Diego have been few prior to the 2004 event reported here. There also were earlier indications of Cochlodinium along the Central Coast, where a 1996 red tide was observed in San Luis Obispo County and portions of Monterey Bay (G. Langlois, pers. obs.). The CDHS Phytoplankton Monitoring Program first detected a bloom of what was later identified as Cochlodinium at Seacliff Pier, Aptos (north central Monterey Bay) on 2 October 1996. This red-brownish bloom appeared monospecific, containing chains of 2–4 cells and coinciding with fouling of the sampling net and mass mortalities of mussels on pier pilings (J. Baltan, Moss Landing Marine Laboratories (MLML), pers. comm.). This red tide event was also noted in other regions of Monterey Bay – at SCW (in the north) and at Monterey Commercial Wharf 2 (in the south) by 22 October 1996, and persisted through mid-November at these sites. A similar event co-occurred along the San Luis Obispo County (220 km south of Monterey) coast throughout this period (G. Langlois, pers. obs.). Unarmored, chain-forming dinoflagellates that sometimes degraded upon preservation in formalin were noted by CDHS program staff and volunteers. A videotape of the live cells was sent to the U.S. Food and Drug Administration’s Office of Seafood, and these cells were identified as a Cochlodinium species (S. Hall, FDA CFSAN, pers. comm.). These sporadic reports of Cochlodinium in the state suggest that background populations of Cochlodinium have long been present, but are only now dominating when conditions that promote their growth exist in coastal waters, especially in the central California coastal regime. The recent description of a new species in California – at least in Monterey Bay – may indicate the need for a taxonomic revision of the group (see Iwataki et al., this issue). 4.2. Occurrence of Cochlodinium in Monterey Bay, 2004– 2006 The first indications of elevated levels of Cochlodinium in Monterey Bay were observed at the offshore M1 mooring
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site located near the center of the bay in late June 2004 (Fig. 3b). Shortly thereafter (2 weeks) small numbers of cells were observed at the nearshore SCW site (Fig. 3a) and by mid July, a large red-brown discoloration of the water, which we will call a ‘‘red tide,’’ had swept through the bay. Upon initial inspection, the cells dominating this event were mistaken for a more commonly observed local dinoflagellate, Alexandrium catenella; however, multiple researchers (G. Langlois, pers. obs.; C. Tomas, U. North Carolina at Wilmington, pers. comm.) subsequently identified these cells as a Cochlodinium species, an isolate of which has since been described as Cochlodinium fulvescens (Iwataki et al., this issue) (Fig. 2a, d, and e). During peak bloom periods, water samples became difficult to filter, due to the presence of a substance(s) that appeared to increase the water’s viscosity (M. Silver, pers. obs.). Throughout the period of high cell densities (6.3 104 cells L1), salinities ranged from 32 to 34 psu and relatively warm temperatures were recorded at the surface (typically above 14 8C) (Fig. 3a and b). These conditions not only appeared to promote the growth of Cochlodinium, but also supported a dinoflagellate-dominated community. After the organism’s appearance in summer 2004, it continued to be abundant, at least occasionally, up until August–September of 2006 (Table 1, this study; Kudela et al., this issue). Cochlodinium was regularly observed co-occurring with Akashiwo sanguinea, Alexandrium catenella, and Ceratium spp., and the frequent presence of this dinoflagellate-dominated community contrasts with the typically diatom-dominated community prior to 2004 (M. Silver, pers. obs.). This shift possibly indicates a change in coastal conditions that now promotes a dinoflagellate-dominated community in Monterey Bay. 4.3. Occurrence of Cochlodinium along the California Coast, 2004–2006 Further investigation into the geographic extent of the event in 2004 revealed coastal counties throughout much of the state experienced elevated levels of Cochlodinium nearly simultaneously. From San Mateo, the most northerly affected county, to San Diego, the southern-most county in California, representing over 800 km of coastline, moderate to high cell abundances were detected. Since 2004 Cochlodinium appears to have persisted along much of this same coastline (Fig. 4a and b); however, during this time Cochlodinium has not been detected from San Francisco northward to Del Norte, at the California-Oregon border. Although the 2004 bloom extended over much of the California coastline, highest densities and most frequent appearances of Cochlodinium were noted in the region referred to as the Central Coast, and particularly Santa Cruz and San Luis Obispo counties (Fig. 4a). The majority of the samples collected from Santa Cruz County and San Luis Obispo County were collected at SCW and at the California Polytechnic Institution pier in Avila Beach, respectively, with both sites being located within embayments and frequently monitored.
Mortalities of various marine organisms have been associated with high densities of various Cochlodinium species worldwide (Onoue and Nozawa, 1989; Yuki and Yoshimatsu, 1989; Guzma´n, 1990; Kim, 1998; Kim, 1999; Kim et al., 2002; Ga´rate-Liza´rraga et al., 2000; Whyte et al., 2001a,b). A number of mussel mortalities were observed in the present study when Cochlodinium levels were high. For example, during the initial Monterey Bay bloom bagged mussels suspended from SCW by the CDHS shellfish monitoring program experienced mass die-offs, with large numbers of putrid, empty, or gaping shells noted on 19 September 2004, 13 October 2004, 1 December 2004, and 9 February 2005 (C. Curtiss, pers. obs.). Phytoplankton samples were difficult to filter, due to clogging by viscous, but transparent, materials in the water. Notably, during other periods of high cell densities no such mortality events were recorded. In San Luis Obispo, during some periods of high Cochlodinium densities, some stock populations of seed oysters experienced up to 90% mortality during periods of water discoloration (D. Alden, Tomales Bay Oyster Company, pers. comm.). The precise mechanism by which this dinoflagellate may cause these harmful effects is still unresolved, but researchers have suggested that the production of polysaccharides (mucus) and reactive oxygen species (O2 and H2O2) by some Cochlodinium species may result in asphyxia and edema, respectively (Guzman et al., 1990; Lee, 1996; Kim, 1999; Whyte et al., 2001a,b; Kim et al., 2002). The unusual abundance of Cochlodinium in the coastal regions of California may be explained by hypotheses of Smayda (2002a,b), suggesting that dinoflagellates demonstrate a high degree of habitat specialization while also maintaining several adaptive strategies. The ability to adapt to changing environmental conditions allows them to disseminate outside their traditional geographic range. Kudela et al. (this issue) proposed that, within the categories identified by Smayda, Cochlodinium falls into the ‘‘mixing-drift’’ group – typically strong-swimming chain-formers that are closely associated with frontal features, common in the California upwelling system, allowing them to take advantage of opening ecological niches in the coastal environment (e.g., Ryan et al., 2005). Further supporting this hypothesis is the apparent co-occurrence of similarly categorized dinoflagellates, including Akashiwo sanguinea, Alexandrium catenella, and Ceratium spp., which were commonly found in high abundance during the 2004 Cochlodinium bloom. Moreover, the rather sudden appearance of abundant Cochlodinium along the California Coast in 2004 and its apparent persistence since then may be analogous to the situation in Korean coastal waters, where background concentrations of this organism were likely present for years before it became a dominant bloom-former over the last 25 years (Cho, 2001; Kim et al., 2004). 5. Conclusion Cochlodinium is an organism of growing concern on a global scale, yet we know relatively little about its overall distribution
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and possible increase in coastal waters. In California, this dinoflagellate appears to have been only an occasional member of the coastal community prior to 2004, but since that time it has become prominent along much of the state’s coastline. It has occasionally been a major contributor to red tides and its presence has coincided with deaths of shellfish stocks in some cases. Cell concentrations have reached at least 6.3 104 cells L1 in central California and, in 2004, populations of this dinoflagellate appeared almost simultaneously along more than 800 km of California coastline. Cochlodinium has persisted since that time and been present in red tides, possibly suggesting a shift in coastal water conditions along this region of the US west coast. Acknowledgements Funding for the study was provided by NOAA (Grants NA16OC2936, NA04NOS4780239) and the University of California Office of the President (03-T-CEQI-07-0062) to M. Silver. We would also like to thank the following agencies for support: National Science Foundation (OCE-0095178), the University of California Coastal Environmental Quality Initiative (03 T CEQI 07 0062) and NOAA/Southern California Coastal Ocean Observing System (NA17RJ231). We also thank our reviewers for their helpful comments, Dr. Greg Doucette for the opportunity to participate, Melissa Carter (Scripps Institution of Oceanography [SIO]) for help on the project, Dr. Elizabeth Venrick (SIO) for editorial comments, Susan Coale (UCSC) for help with photography, the crew of the RV/Pt. Lobos, and the CDHS Phytoplankton Monitoring Program volunteers, whose dedication and effort has improved our understanding of the coastal phytoplankton community.[SS] References Cho, E.S., 2001. A comparative study of the harmful dinoflagellates Cochlodinium polykrikoides and Gyrodinium impudicum using transmission electron microscopy, fatty acid composition, carotenoid content, DNA quantification and gene sequences. Bot. Mar. 44, 57–66. Cho, E., Costas, E., 2004. Rapid monitoring for the potentially ichthyotoxic dinoflagellate Cochlodinium polykrikoides in Korean coastal waters using fluorescent probe tools. J. Plankton. Res. 26, 175–180. Ga´rate-Liza´rraga, I., Bustillos-Guzma´n, J., Morquecho, L.M., LechugaDeveze, C.H., 2000. First outbreak of Cochlodinium polykrikoides in the Gulf of California. Harmful Algae News 21, 7. Ga´rate-Liza´rraga, I., Lo´pez-Corets, J., Bustillos-Guzma´n, J., Herna´ndezSandoval, F., 2004. Blooms of Cochlodinium polykrikoides (Gymnodiniaceae) in the Gulf of California, Mexico. Rev. Biol. Trop. 52, 51–58. Guzma´n, H.M., 1990. Coral mortality associated with dinoflagellate blooms in the Eastern Pacific (Costa Rica and Panama). Mar. Ecol. Prog. Ser. 60, 299– 304. Holmes, R., William, P., Eppley, R., 1967. Red water in La Jolla Bay, 1964– 1966. Limnol. Oceanogr. 12, 503–512. Iwataki, M., Kawami, H., Matsuoka, K., 2007. Cochlodinium fulvescens sp. nov. (Gymnodiniales, Dinophyceae), a new chain-forming unarmored dinoflagellate from Asian coasts. Phycol. Res. 55, 231–239. Iwataki, M., Kawami, H., Mizushima, K., Mikulski, C.M., Doucette, G.J., Relox Jr., J.R., Anton, A., Fukuyo, Y., Matsuoka, K. Phylogenetic relationships in the harmful dinoflagellate Cochlodinium polykrikoides (Gymno-
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diniales, Dinophyceae) inferred from LSU rDNA sequences. Harmful Algae, doi:10.1016/j.hal.2007.12.003, this issue. Kim, H.G., 1998. Harmful algal blooms in Korean coastal waters focused on three fish killing dinoflagellates. In: Lee, H.G., Lee, S.G., Lee, C.K. (Eds.), Harmful Algal Blooms in Korea and China. NFRDI, Pusan, Republic of Korea, pp. 1–20. Kim, C.S., 1999. Reactive oxygen species as causative agents in the ichthyotoxicity of the red tide dinoflagellate Cochlodinium polykrikoides. J. Plankton Res. 21, 2105–2115. Kim, D.-I., Oda, T., Muramatsu, T., Kim, D., Matsuyama, Y., Honjo, T., 2002. Possible factors responsible for the toxicity of Cochlodinium polykrikoides, a red tide phytoplankton. Comparative biochemistry and physiology. Toxicol. Pharmacol. 132, 415–423. Kim, D.-I., Matsuyama, Y., Nagasoe, S., Yamaguchi, M., Yoon, Y.-H., Oshima, Y., Imada, N., Honjo, T., 2004. Effects of temperature, salinity, and irradiance on the growth of the harmful red tide dinoflagellate Cochlodinium polykrikoides Margalef (Dinophyceae). J. Plankton. Res. 26, 61–66. Kofoid, C., Swezy, O., 1921. The Free-Living Unarmored Dinoflagellata. Memoirs of the University of California 5, 342–388. Kudela, R.M, Ryan, J.P., Blakely, M.D., Lane, J.Q., Peterson, T.D. Linking the physiology and ecology of Cochlodinium to better understand harmful algal bloom events: a comparative approach. Harmful Algae, doi:10.1016/ j.hal.2007.12.016, this issue. Langlois, G. 2004. Marine Biotoxin Monitoring Program Annual Report, 2004. California Department of Health Services, pp. 44. Lara, M., 2004. Presence of Cochlodinium catenatum (Gymnodiniales: Gymnodiniaceae) in red tides of Bahia de Banderas, Mexican Pacific. Rev. Biol. Trop. 52, 35–49. Lee, J.-S., 1996. Bioactive components from red tide plankton, Cochlodinium polykrikoides. J. Korean Fish. Soc. 29, 165–173. Lee, Y., 2006. Factors affecting outbreaks of Cochlodinium polykrikoides blooms in coastal areas of Korea. Mar. Pollut. Bull. 52, 626–634. Lee, C., Kim, H., Lee, S.-G., Jung, C., Kim, H., Lim, W., 2001. Abundance of harmful algae, Cochlodinium polykrikoides, Gyrodinium impudicum and Gymnodinium catenatum in the coastal area of South Sea of Korea and their effects of temperature, salinity, irradiance and nutrient on the growth in culture. J. Korean Fish. Soc. 34, 536–544. Margalef, R., 1961. Hidrografia y fitoplancton de un area marina de la costa meridional de Puerto Rico. Inv. Pesq. Tomo 18, 76–78 in Spanish. Matsuoka, K., Iwataki, M., Kawami, H., 2006. Morphology of chain forming species of the genus Cochlodinium (Dinophyceae) found in Japanese coastal waters. In: Doucette, G.J., Lee, C.-K. (Eds.), Workshop of Recent Progress on the Research and Management of Cochlodinium Blooms. Cheju National University, Korea, pp. 3–9. Morales-Blake, A., Cavazos-Guerra, C., Hernandez-Becerril, D., 2001. Unusual HABs in Manzanillo Bay, Colima, Mexico. Harmful Algae News 22, 6. Onoue, Y., Nozawa, K., 1989. Separation of toxins from harmful red tides occurring along the coast of Kagoshima prefecture. In: Okaichi, T., Anderson, D.M., Nemoto, T. (Eds.), Red Tides: Biology, Environmental Science, and Toxicology. Elsevier Publishers, New York, pp. 371– 374. Qi, D., Huang, Y., Wang, X., 1993. Toxic dinoflagellate red tide by a Cochlodinium sp. along the coast of Fujian, China. In: Smayda, T., Shimizu, Y. (Eds.), Toxic Phytoplankton Blooms in the Sea. Elsevier Publishers BV, Amsterdam, pp. 235–238. Ryan, J., Dierssen, H., Kudela, R., Scholin, C., Johnson, K., Sullivan, J., Fischer, A., Rienecker, E., McEnaney, P., Chavez, F., 2005. Coastal ocean physics and red tides: an example from Monterey Bay, California. Oceanogr. 18, 246–255. Smayda, T., 2002a. Adaptive ecology, growth strategies, and the global bloom expansion of dinoflagellates. J. Oceanogr. 58, 281–291. Smayda, T., 2002b. Turbulence, watermass stratification and harmful algal blooms: an alternative view and frontal zones as ‘‘pelagic seed banks’’. Harmful Algae 1, 95–112. Utermo¨hl, H., 1958. Zur Vervollkommnung der quantitativen Phytoplanktonmethodik. Mitt. Int. Ver. Limnol. 9, 1–38.
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Vargas-Montero, M., Freer, E., Jimenez-Montealegre, R., Guman, J., 2004. Extensive blooms due to Cochlodinium polykrikoides: New to Costa Rica. Harmful Algae News 26, 7. Whyte, J., Haigh, N., Ginther, N., Keddy, L., 2001a. First record of blooms of Cochlodinium sp. (Gymnodiniales, Dinophyceae) causing mortality to aquacultured salmon on the west coast of Canada. Phycologia 40, 298–304.
Whyte, J., Haigh, N., Ginther, N., Keddy, L., 2001b. Influence of Cochlodinium polykrikoides blooms on aquacultured salmonids. Can. Tech. Rep. Fish. Aquat. Sci. 2386, 3–5. Yuki, K., Yoshimatsu, S., 1989. Two fish-killing species of Cochlodinium from Harima-Nada, Seto Inland Sea, Japan. In: Okaichi, T., Anderson, D.M., Nemoto, T. (Eds.), Red Tides: Biology, Environmental Science, and Toxicology. Elsevier Publishers, New York, pp. 451–454.
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The emergence of Cochlodinium along the California Coast (USA) Casey C. Curtiss a,*, Gregg W. Langlois b, Lilian B. Busse c, Fernanda Mazzillo a,c, Mary W. Silver a,d a Department of Ocean Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA California Department of Health Services, Environmental Management Branch, 850 Marina Bay Parkway, Richmond, CA 94804, USA c Integrative Oceanography Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA d Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA 95039, USA b
Received 27 October 2006; received in revised form 4 April 2007
Abstract A sudden and nearly synchronous emergence of the red tide forming dinoflagellate Cochlodinium along more than 800 km of California coastline was initially observed in late summer 2004. Thereafter high cell concentrations have been detected on an annual basis. Here, we present quantitative and semi-quantitative data indicating that Cochlodinium was uncommon in the phytoplankton community in California prior to 2004 and is now persisting as a more regular component and one that seasonally can cause red tides. The quantitative portion of this study was primarily conducted in Monterey Bay, where cell densities reached at least 6 104 cells L1 during the initial outbreak. A semi-quantitative comparison of California coastal counties by the California Department of Health Services (CDHS) was also made: of the 15 counties surveyed (most with multiple sites per county), cells were detected only from Los Angeles County in the south to San Mateo County in the central region (seven counties), but not in the northern part of the state (six counties). Two counties in the central region of the state, San Luis Obispo and Santa Cruz, displayed intense and frequent periods of elevated Cochlodinium cell abundances. Although not observed in the state-wide CDHS survey, we occasionally found cells in San Diego County with densities up to 2.7 104 cells L1. Though these colonial dinoflagellates have been recognized in California for over 80 years, with several ‘‘blooms’’ recorded prior to 2004, the species’ geographic range and abundance in recent years suggest significant shifts in the nearshore phytoplankton community of this region of the eastern Pacific. # 2007 Elsevier B.V. All rights reserved. Keywords: California Coast; Cochlodinium; Dinoflagellate; Monterey Bay; Red tide
1. Introduction Harmful bloom events caused by the athecate, chainforming dinoflagellate Cochlodinium have been increasing in frequency in coastal waters around the world’s oceans. Much of the attention has been focused in regions of the western Pacific including Korea, Japan and, to a lesser extent, China (Yuki and Yoshimatsu, 1989; Qi et al., 1993; Kim, 1998; Lee et al., 2001; Cho and Costas, 2004; Lee, 2006; Matsuoka et al., 2006), which have experienced substantial economic losses as a result of this organism’s deleterious effects on fish stocks (Onoue and Nozawa, 1989; Yuki and Yoshimatsu, 1989; Kim, 1999; Whyte et al., 2001a,b). To date, no toxic mechanisms have been confirmed. Blooms of this dinoflagellate have also been noted
* Corresponding author. Tel.: +1 831 459 2948; fax: +1 831 459 4882. E-mail address: [email protected] (C.C. Curtiss). 1568-9883/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.hal.2007.12.012
along the coast of the eastern Pacific (Costa Rica, Mexico) and the Caribbean (Puerto Rico) (Margalef, 1961; Morales-Blake et al., 2001; Ga´rate-Liza´rraga et al., 2004; Lara, 2004; VargasMontero et al., 2004). There have been occasional reports of Cochlodinium on the California Coast and discolored surface water caused by this organism was noted in 1964 (Holmes et al., 1967). This report presents new data on Cochlodinium and its apparently rapid emergence along the California coastline, where it appears to have become a common component of the phytoplankton. We also assemble a variety of records that indicate Cochlodinium was not seen with any regularity along the state’s coastline until 2004. The lack of data on the organism along the California Coast may be a result of its infrequency in the past, may reflect the potential difficulty of recognizing older, preserved specimens, or it may also indicate that cells in this genus, especially in low numbers, could be confused with other chain-forming dinoflagellates, particularly Alexandrium
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species, much better known in the region. In this paper, we use the designation ‘‘Cochlodinium’’ for the organisms: the designation of the photosynthetic species of Cochlodinium in California is not entirely clear, but some specimens from Monterey Bay, and possibly elsewhere on the western N. American coastline, belong to the newly described C. fulvescens (Iwataki et al., 2007) (see Iwataki et al., this issue). 2. Materials and methods This report on Cochlodinium along the coast of California, USA was assembled from multiple data sources available to the authors from several ongoing coastal studies. The main research objectives of all investigators involved differ to some extent; hence, these groups used different sampling schedules, covered various temporal and spatial scales, and performed phytoplankton analyses that were either quantitative or semiquantitative. Researchers from the University of California, Santa Cruz (UCSC) were focused on the Monterey Bay area, whereas the Scripps Institution of Oceanography (SIO) group concentrated on the San Diego Region, and the California Department of Health Services (CDHS) project encompassed the entire coastline from the California/Oregon Border (Del Norte County) to the California/Mexico Border (San Diego County) (Fig. 1). 2.1. Monterey Bay sampling, 2004–2005 Water samples for quantitative measures of cell abundance were collected by the UCSC group from January 2004 to February 2005 at the Santa Cruz Wharf (SCW) and from January 2004 to December 2004 at the offshore Monterey Bay Aquarium Research Institute (MBARI) M1 mooring site, approximately 20 km offshore of Moss Landing and over 1000 m water depth (Fig. 1). Sampling was performed once to several times per week
at the SCW site, depending on whether blooms were present, while the M1 site was sampled once weekly, ship access permitting. Water samples at both sites were collected by surface bucket, which provided sub-samples for cell enumeration. At SCW, surface seawater samples were collected and sub-sampled for salinity analysis and cell counts. Water temperature was measured with a digital thermometer immediately upon collection. Additionally, a net tow (35 mm mesh) sample was obtained by hauling the net five times from 3 m depth to the surface. Net tow material was examined in the laboratory using a dissecting microscope (Olympus SZH Stereozoom) to characterize the planktonic community and a record kept of species observed in each sample. Water for salinity analysis (conductivity) was prepared by filtering200 mL through a 25 mm Whatman GF/F filter and tested using a portable salinometer (Guildline Portasal mod. 8410). Aliquots of 100 mL were preserved in 4% formaldehyde for cell enumeration. Water samples were collected at the M1 station (R/V Pt Lobos; MBARI) and then transported to UCSC, where aliquots were either fixed (see above) or examined live to characterize the dominant netplankton. Temperature and salinity data for M1 water samples were obtained from MBARI’s on-line database (http://mbari.org/). Cell abundance for samples collected both at SCW and M1 was quantified using the Utermo¨hl method (Utermo¨hl, 1958). Initially, a 50 mL aliquot of preserved water samples was settled for a minimum of 24 h prior to examination. For samples found to contain dense populations of Cochlodinium, 10 mL aliquots were settled and individual cells of Cochlodinium were then counted on an inverted microscope (Olympus IMT-2). 2.2. Archival samples from Monterey Bay, 2001–2006 To assess the possible occurrence of Cochlodinium in Monterey Bay during likely bloom periods in additional years, fixed (4% formaldehyde) samples were observed from net tow
Fig. 1. (a) Map of Monterey Bay, California, showing locations where field samples were collected (M1 and Santa Cruz Wharf); (b) Coastal counties of California showing the geographical regions (shaded) with reported Cochlodinium since the initial 2004 outbreak.
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material obtained at SCW from June 2001–September 2006 using light microscopy. A semi-quantitative analysis of cell abundance in these net collections was made using a ranking system of visually estimated biovolumes: ND (non-detect) – no cells; Present – 1–9%; Common – 10–49%; Abundant – >50%. 2.3. California sampling by county: the CDHS data set Phytoplankton net tow samples (100 mL) were collected in 15 California coastal counties from Del Norte County in the north to San Diego County in the south by a volunteer monitoring network managed by the CDHS Marine Biotoxin Monitoring Program. Collections were made at one or more sites in each county and all samples were analyzed by CDHS. Sampling frequency varied by site and typically ranged from weekly to bimonthly. Plankton tows, conducted primarily from nearshore locations (piers, docks) and, to a lesser extent, from boats, were collected using a 1 m long, 25 cm diameter, 20 mmmesh net and the total tow effort (tow distance) noted. The sampling effort was standardized to vertical tows of 3–10 m depth and entailed multiple vertical retrievals of the net (typically 3–5). Material was preserved using approx. 1% formalin (final concentration) and immediately shipped to CDHS for analysis. All samples were settled prior to observation by phase contrast microscopy (Zeiss Axiskop 2+ or Leitz Ortholux) and examined to describe phytoplankton species assemblages. All genera identified were recorded and an estimate of percent composition generated. In addition, a volumetric estimate of the settled cell mass was recorded, excluding any contribution from detrital matter. Because sampling effort and settled cell mass varied between samples and sampling sites, an attempt was made to normalize the percentage composition data for each species by calculating a Relative Abundance Index (RAI). The RAI, devised by CDHS (Langlois, 2004), is based on estimates of (a) overall biomass of cells in the net tow as determined by settled cell volume; (b) the percent composition by biovolume of each genus (in that volume of phytoplankton material); and (c) the sampling effort as determined by the total tow length: RAI ¼
ða bÞ c
The RAI provides a means of normalizing qualitative data to yield a semi-quantitative measure of the biovolume for a given genus of net plankton. This technique standardizes the effects of filtering different volumes of water (i.e., tow length) and the relative contribution of various genera in samples taken along the California coastline. 2.4. San Diego County sampling Surface water samples were collected from 1992 through 2000 by personnel from Scripps Institution of Oceanography (SIO, La Jolla, CA) at their pier using a Niskin bottle. Samples were fixed in 4% formaldehyde, archived, and evaluated at a later date (2002–2003). From October 2003 through July 2006, samples were obtained at the SIO pier by surface bucket and
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vertical net tows (20 mm mesh) between approximately 3 m and the surface. Between October 2003 and October 2005, only semi-quantitative observations from the archived net tow samples were conducted using a ranking system similar to that outlined above (i.e., present, common, dominant). Beginning in October 2005 through July 2006, phytoplankton community composition was determined and quantitative cell counts (Utermo¨hl method) performed as described above. 3. Results 3.1. Cochlodinium in Monterey Bay Cochlodinium (Fig. 2a, d and e) occurred frequently in Monterey Bay both as single cells and in colonies typically of 2–4 cells (Fig. 2e), but occasionally in chains up to eight cells long (Fig. 2a). The cells, usually deep gold-brown when viewed by light microscopy, caused the water to appear muddy brown to reddish when abundant. Chloroplasts were granular and appeared to be distributed around the cell periphery (Fig. 2f). Individual cells (Fig. 2) ranged from approx. 25–50 mm in length and 20–40 mm in width and were typically spherical to slightly ellipsoid (compressed dorso-ventrally). The cells swam about vigorously in freshly collected field samples and no temporary cysts were observed when examined at higher power. The locomotion was characterized by smooth, looping spirals with a minor wobble associated with the forward motion. The cells were sheathed in irregular, mucus-like material at the surface, which sometimes tended to disintegrate after storage in formaldehyde (Fig. 2d) thus making them less readily distinguishable in samples stored for extended periods, especially if the observer was not familiar with the organism. In our study, samples up to at least 10 years of age contained recognizable Cochlodinium cells, but there was clearly some degradation that could result in underestimates of cell abundance. When viewed under low magnification, Cochlodinium could be confused with cells of Alexandrium catenella (Fig. 2b and c). Both are chain-forming dinoflagellates of similar size, but there are several distinguishing characteristics. Cochlodinium is athecate and encased in an extracellular matrix of mucilage, which is apparent under light microscopy. The cells are spherical to slightly ellipsoid. In contrast, A. catenella is thecate, displaying very noticeable thecal plates and a distinct cingulum. While Cochlodinium also exhibits a cingulum, it is typically much less apparent. The cells of A. catenella are also anterior-posteriorly compressed as compared to those of Cochlodinium, which are dorso-ventrally compressed. The quantitative part of the study in Monterey Bay at SCW (Fig. 3a) and the offshore M1 site (Fig. 3b) was focused on the time period between the major appearance of Cochlodinium in summer 2004 until February 2005 and December 2004, respectively. Samples also were examined for the interval between January 2004 and early June 2004, when no cells were detected at either of these sites. Cochlodinium was first observed at the M1 site (24 June 2004) and subsequently at the SCW site (6 July 2004). Over the duration of the 2004 bloom, maximal cell densities at M1 reached 3.3 104 cells L1 (4
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Fig. 2. Photomicrographs of Cochlodinium and Alexandrium catenella collected from Santa Cruz Wharf (SCW) and Scripps Institute of Oceanography (SIO) pier. (a) Eight cell chain of freshly preserved Cochlodinium (SCW); (b) eight cell chain of preserved A. catenella (SCW). Note similar morphology to Cochlodinium; (c) Four cell chain of A. catenella (SCW). Note pronounced theca and cingulum; (d) Cochlodinium after extended period of preservation in 10% formaldehyde solution (SCW). Note disintegration of the cells; (e) doublet (two cell chain) of Cochlodinium sp. from live sample (SCW); (f) chloroplasts visible under fluorescent microscopy (SCW); (g) four-cell chain of preserved Cochlodinium from SIO Pier. Scale bars = 40 mm.
November 2004) and 6.0 104 cells L1 at SCW (21 September 2004). These may be underestimates, as some cells become difficult to identify when preserved (see above). The offshore M1 mooring site generally had lower cell densities and cells were less frequently observed there than at SCW. Cochlodinium persisted beyond the sampling period at both sites, as described below. When Cochlodinium was present, and especially when abundant, vacuum filtration was slowed and the volume collected was limited due presumably to the presence of colloidal materials associated with the cells. The temperature and salinity conditions from summer 2004 through January 2005 during which Cochlodinium were found are shown in Fig. 3a and b, along with the conditions when ‘‘blooms’’ (here defined as > 104 cells L1) occurred. During the blooms, temperatures were at or above 14 8C and salinities
between 33 and 34 psu, though several substantial events occurred at salinities as low as 32 psu at SCW (27 July 2004, 30 July 2004). All events of > 3 104 cells L1 were found at temperatures above 14 8C; nonetheless, significant cell numbers (>1.5 104 L1) were observed down to 12.8 8C at both sites and cells were detected at temperatures as low as 11.2 8C (SCW, 28 December 2004). Further, qualitative observations at both SCW and M1 demonstrated Cochlodinium’s presence subsequently from July 2006 through October 2006, sometimes dominating the net phytoplankton (Table 1). Archived samples (2001–2003) were examined to determine whether cells had been present in net tows from SCW before the major 2004 Cochlodinium event (Table 1). No cells were observed in samples obtained during summer and fall, when oceanographic conditions would be expected to favor the
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Fig. 3. Temporal variations of Cochlodinium cell abundance, temperature (8C), and salinity (psu) for (a) Santa Cruz Wharf (SCW) and (b) offshore M1 mooring site (operated by Monterey Bay Aquarium Research Institute) for 2004–2006.
presence of Cochlodinium. This finding is supported by ongoing records produced by both the UCSC group and CDHS that document phytoplankton assemblages from live water samples. 3.2. Cochlodinium from Del Norte to San Diego County: the CDHS data set During the sampling period (January 2004–July 2006), phytoplankton assemblages were evaluated from each of the Table 1 Cochlodinium during optimal bloom period from 2001 through 2006 using archived net tow material collected from the Santa Cruz Municipal Wharf and the offshore M1 site, Monterey Bay Year
June
July
August
September
October
November
2001 2002 2003 2004 2005 2006
ND ND ND ND P ND
ND ND ND A C P
ND ND ND A P A
ND ND ND P C P
ND ND ND A C A
ND ND ND A P n/a
ND, not detected; P, present; C, common; A, abundant.
coastal counties in California (>3,250 individual samples, 168 unique sampling sites). Counties where Cochlodinium was observed are shown in Fig. 4a and b. The six northerly counties (Del Norte to San Francisco) and San Diego County in the south, though heavily sampled, and the less frequently sampled Orange County, also in the south, showed no evidence of Cochlodinium from net tows obtained over this time period (data not shown). The appearance of substantial numbers of Cochlodinium in Monterey Bay during summer 2004 coincided with its appearance over a very large extent of central and southern California during approximately the same time period (Fig. 5). Outbreaks occurred in late summer to early fall of 2004 and Cochlodinium populations persisted through much of the winter and then declined. Records from the subsequent year (2005) were similar, with high cell abundances observed during essentially the same time in summer and fall. San Mateo County, the most northerly site at which Cochlodinium were found, had the fewest observations, though they did occur here during the widespread coastal blooms of both 2004 and 2005. Cochlodinium populations were most frequently observed in Santa Cruz (SC) and San Luis Obispo (SLO) counties over the study period; however, these two
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Fig. 4. Cochlodinium distribution for (a) Central Coast region and (b) southern California region by county (CDHS data). Coastal counties that experienced no observable cells are omitted. Symbols are same as for Fig. 5.
counties were also the most frequently sampled. Both counties clearly displayed peak bloom periods in the late summer (July and August, 2004), which persisted through much of the winter. Populations in Monterey (situated between SC and SLO counties) and Santa Barbara (directly south of SLO) counties also had increased cell abundance during the late summer–early fall (August and September) of 2004 and 2005, but were less dense than those in SLO and SC counties. Cochlodinium was also found in Ventura County (winter 2005 through summer 2006), but data were not collected during the 2004 event. No
Cochlodinium cells were noted in Los Angeles County until spring (March) of 2005. The dinoflagellate occurred again in summer (June) and during late fall (November) of 2005, and continued through the winter at this location. 3.3. Cochlodinium in San Diego County At the time of the initial emergence of Cochlodinium along the central and southern California Coast in 2004, cells were observed on only one occasion from the SIO pier (11 November
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4. Discussion 4.1. Historical record of Cochlodinium along the California Coast, prior to 2004
Fig. 5. Cochlodinium distribution along California coastline (Del Norte – San Diego). All coastal counties were surveyed. Percent composition and RAI are for net plankton-sized phytoplankton (see text for details).
Fig. 6. Observed Cochlodinium at Scripps Institution of Oceanography (SIO) pier during a period of elevated cell densities January 2006–July 2006.
2004; L. Busse, pers. obs.). Cells were not detected again until October 2005 when Cochlodinium was found in net tow samples at low concentrations. Elevated concentrations were detected on 23 January 2006 (7.8 103 cells L1), coinciding with the initial stages of a red tide event that persisted through May 2006 (Fig. 6). During this event, Cochlodinium cooccurred with Prorocentrum micans, Akashiwo sanguinea, and an unidentified Gymnodinium sp. Maximal cell densities of Cochlodinium reached 2.7 104 cells L1 (20 March 2006) and salinity ranged between 33 and 34 psu during the time of elevated cell numbers. Temperature dropped below 14 8C on 13 March 2006 and was lowest (12.7 8C) at the peak of the bloom (20 March 2006). Cells collected from the SIO pier (Fig. 2g) exhibited morphology similar to cells observed in Monterey Bay (Fig. 2a). Archived samples from 1992 through 2000 showed that Cochlodinium were occasionally present but generally below 5 103 cells L1. However, on two occasions, elevated densities of Cochlodinium were noted at SIO pier – in 1994 (6.6 104 cells L1 on 22 April 1994) and in 1998 (6.3 104 cells L1 on 23 April 1998).
The emergence of Cochlodinium as a common bloomforming organism in regions along the California coastline appears to be a recent phenomenon. However, taxonomic uncertainties about the organism have made historical analysis difficult. This genus does not appear to have received much attention since early analyses of California species of the genus by Kofoid and Swezy (1921) showing that Cochlodinium occurred off San Diego. A later report by Holmes et al. (1967) documented a red tide in La Jolla Bay, San Diego in May 1964, with the causative organism being a Cochlodinium species. In our survey of material dating back to the 1990s, we found that Cochlodinium was occasionally present, mostly at low abundance, at the SIO pier in La Jolla between 1992 and 2000. Reports of Cochlodinium north of San Diego have been few prior to the 2004 event reported here. There also were earlier indications of Cochlodinium along the Central Coast, where a 1996 red tide was observed in San Luis Obispo County and portions of Monterey Bay (G. Langlois, pers. obs.). The CDHS Phytoplankton Monitoring Program first detected a bloom of what was later identified as Cochlodinium at Seacliff Pier, Aptos (north central Monterey Bay) on 2 October 1996. This red-brownish bloom appeared monospecific, containing chains of 2–4 cells and coinciding with fouling of the sampling net and mass mortalities of mussels on pier pilings (J. Baltan, Moss Landing Marine Laboratories (MLML), pers. comm.). This red tide event was also noted in other regions of Monterey Bay – at SCW (in the north) and at Monterey Commercial Wharf 2 (in the south) by 22 October 1996, and persisted through mid-November at these sites. A similar event co-occurred along the San Luis Obispo County (220 km south of Monterey) coast throughout this period (G. Langlois, pers. obs.). Unarmored, chain-forming dinoflagellates that sometimes degraded upon preservation in formalin were noted by CDHS program staff and volunteers. A videotape of the live cells was sent to the U.S. Food and Drug Administration’s Office of Seafood, and these cells were identified as a Cochlodinium species (S. Hall, FDA CFSAN, pers. comm.). These sporadic reports of Cochlodinium in the state suggest that background populations of Cochlodinium have long been present, but are only now dominating when conditions that promote their growth exist in coastal waters, especially in the central California coastal regime. The recent description of a new species in California – at least in Monterey Bay – may indicate the need for a taxonomic revision of the group (see Iwataki et al., this issue). 4.2. Occurrence of Cochlodinium in Monterey Bay, 2004– 2006 The first indications of elevated levels of Cochlodinium in Monterey Bay were observed at the offshore M1 mooring
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site located near the center of the bay in late June 2004 (Fig. 3b). Shortly thereafter (2 weeks) small numbers of cells were observed at the nearshore SCW site (Fig. 3a) and by mid July, a large red-brown discoloration of the water, which we will call a ‘‘red tide,’’ had swept through the bay. Upon initial inspection, the cells dominating this event were mistaken for a more commonly observed local dinoflagellate, Alexandrium catenella; however, multiple researchers (G. Langlois, pers. obs.; C. Tomas, U. North Carolina at Wilmington, pers. comm.) subsequently identified these cells as a Cochlodinium species, an isolate of which has since been described as Cochlodinium fulvescens (Iwataki et al., this issue) (Fig. 2a, d, and e). During peak bloom periods, water samples became difficult to filter, due to the presence of a substance(s) that appeared to increase the water’s viscosity (M. Silver, pers. obs.). Throughout the period of high cell densities (6.3 104 cells L1), salinities ranged from 32 to 34 psu and relatively warm temperatures were recorded at the surface (typically above 14 8C) (Fig. 3a and b). These conditions not only appeared to promote the growth of Cochlodinium, but also supported a dinoflagellate-dominated community. After the organism’s appearance in summer 2004, it continued to be abundant, at least occasionally, up until August–September of 2006 (Table 1, this study; Kudela et al., this issue). Cochlodinium was regularly observed co-occurring with Akashiwo sanguinea, Alexandrium catenella, and Ceratium spp., and the frequent presence of this dinoflagellate-dominated community contrasts with the typically diatom-dominated community prior to 2004 (M. Silver, pers. obs.). This shift possibly indicates a change in coastal conditions that now promotes a dinoflagellate-dominated community in Monterey Bay. 4.3. Occurrence of Cochlodinium along the California Coast, 2004–2006 Further investigation into the geographic extent of the event in 2004 revealed coastal counties throughout much of the state experienced elevated levels of Cochlodinium nearly simultaneously. From San Mateo, the most northerly affected county, to San Diego, the southern-most county in California, representing over 800 km of coastline, moderate to high cell abundances were detected. Since 2004 Cochlodinium appears to have persisted along much of this same coastline (Fig. 4a and b); however, during this time Cochlodinium has not been detected from San Francisco northward to Del Norte, at the California-Oregon border. Although the 2004 bloom extended over much of the California coastline, highest densities and most frequent appearances of Cochlodinium were noted in the region referred to as the Central Coast, and particularly Santa Cruz and San Luis Obispo counties (Fig. 4a). The majority of the samples collected from Santa Cruz County and San Luis Obispo County were collected at SCW and at the California Polytechnic Institution pier in Avila Beach, respectively, with both sites being located within embayments and frequently monitored.
Mortalities of various marine organisms have been associated with high densities of various Cochlodinium species worldwide (Onoue and Nozawa, 1989; Yuki and Yoshimatsu, 1989; Guzma´n, 1990; Kim, 1998; Kim, 1999; Kim et al., 2002; Ga´rate-Liza´rraga et al., 2000; Whyte et al., 2001a,b). A number of mussel mortalities were observed in the present study when Cochlodinium levels were high. For example, during the initial Monterey Bay bloom bagged mussels suspended from SCW by the CDHS shellfish monitoring program experienced mass die-offs, with large numbers of putrid, empty, or gaping shells noted on 19 September 2004, 13 October 2004, 1 December 2004, and 9 February 2005 (C. Curtiss, pers. obs.). Phytoplankton samples were difficult to filter, due to clogging by viscous, but transparent, materials in the water. Notably, during other periods of high cell densities no such mortality events were recorded. In San Luis Obispo, during some periods of high Cochlodinium densities, some stock populations of seed oysters experienced up to 90% mortality during periods of water discoloration (D. Alden, Tomales Bay Oyster Company, pers. comm.). The precise mechanism by which this dinoflagellate may cause these harmful effects is still unresolved, but researchers have suggested that the production of polysaccharides (mucus) and reactive oxygen species (O2 and H2O2) by some Cochlodinium species may result in asphyxia and edema, respectively (Guzman et al., 1990; Lee, 1996; Kim, 1999; Whyte et al., 2001a,b; Kim et al., 2002). The unusual abundance of Cochlodinium in the coastal regions of California may be explained by hypotheses of Smayda (2002a,b), suggesting that dinoflagellates demonstrate a high degree of habitat specialization while also maintaining several adaptive strategies. The ability to adapt to changing environmental conditions allows them to disseminate outside their traditional geographic range. Kudela et al. (this issue) proposed that, within the categories identified by Smayda, Cochlodinium falls into the ‘‘mixing-drift’’ group – typically strong-swimming chain-formers that are closely associated with frontal features, common in the California upwelling system, allowing them to take advantage of opening ecological niches in the coastal environment (e.g., Ryan et al., 2005). Further supporting this hypothesis is the apparent co-occurrence of similarly categorized dinoflagellates, including Akashiwo sanguinea, Alexandrium catenella, and Ceratium spp., which were commonly found in high abundance during the 2004 Cochlodinium bloom. Moreover, the rather sudden appearance of abundant Cochlodinium along the California Coast in 2004 and its apparent persistence since then may be analogous to the situation in Korean coastal waters, where background concentrations of this organism were likely present for years before it became a dominant bloom-former over the last 25 years (Cho, 2001; Kim et al., 2004). 5. Conclusion Cochlodinium is an organism of growing concern on a global scale, yet we know relatively little about its overall distribution
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and possible increase in coastal waters. In California, this dinoflagellate appears to have been only an occasional member of the coastal community prior to 2004, but since that time it has become prominent along much of the state’s coastline. It has occasionally been a major contributor to red tides and its presence has coincided with deaths of shellfish stocks in some cases. Cell concentrations have reached at least 6.3 104 cells L1 in central California and, in 2004, populations of this dinoflagellate appeared almost simultaneously along more than 800 km of California coastline. Cochlodinium has persisted since that time and been present in red tides, possibly suggesting a shift in coastal water conditions along this region of the US west coast. Acknowledgements Funding for the study was provided by NOAA (Grants NA16OC2936, NA04NOS4780239) and the University of California Office of the President (03-T-CEQI-07-0062) to M. Silver. We would also like to thank the following agencies for support: National Science Foundation (OCE-0095178), the University of California Coastal Environmental Quality Initiative (03 T CEQI 07 0062) and NOAA/Southern California Coastal Ocean Observing System (NA17RJ231). We also thank our reviewers for their helpful comments, Dr. Greg Doucette for the opportunity to participate, Melissa Carter (Scripps Institution of Oceanography [SIO]) for help on the project, Dr. Elizabeth Venrick (SIO) for editorial comments, Susan Coale (UCSC) for help with photography, the crew of the RV/Pt. Lobos, and the CDHS Phytoplankton Monitoring Program volunteers, whose dedication and effort has improved our understanding of the coastal phytoplankton community.[SS] References Cho, E.S., 2001. A comparative study of the harmful dinoflagellates Cochlodinium polykrikoides and Gyrodinium impudicum using transmission electron microscopy, fatty acid composition, carotenoid content, DNA quantification and gene sequences. Bot. Mar. 44, 57–66. Cho, E., Costas, E., 2004. Rapid monitoring for the potentially ichthyotoxic dinoflagellate Cochlodinium polykrikoides in Korean coastal waters using fluorescent probe tools. J. Plankton. Res. 26, 175–180. Ga´rate-Liza´rraga, I., Bustillos-Guzma´n, J., Morquecho, L.M., LechugaDeveze, C.H., 2000. First outbreak of Cochlodinium polykrikoides in the Gulf of California. Harmful Algae News 21, 7. Ga´rate-Liza´rraga, I., Lo´pez-Corets, J., Bustillos-Guzma´n, J., Herna´ndezSandoval, F., 2004. Blooms of Cochlodinium polykrikoides (Gymnodiniaceae) in the Gulf of California, Mexico. Rev. Biol. Trop. 52, 51–58. Guzma´n, H.M., 1990. Coral mortality associated with dinoflagellate blooms in the Eastern Pacific (Costa Rica and Panama). Mar. Ecol. Prog. Ser. 60, 299– 304. Holmes, R., William, P., Eppley, R., 1967. Red water in La Jolla Bay, 1964– 1966. Limnol. Oceanogr. 12, 503–512. Iwataki, M., Kawami, H., Matsuoka, K., 2007. Cochlodinium fulvescens sp. nov. (Gymnodiniales, Dinophyceae), a new chain-forming unarmored dinoflagellate from Asian coasts. Phycol. Res. 55, 231–239. Iwataki, M., Kawami, H., Mizushima, K., Mikulski, C.M., Doucette, G.J., Relox Jr., J.R., Anton, A., Fukuyo, Y., Matsuoka, K. Phylogenetic relationships in the harmful dinoflagellate Cochlodinium polykrikoides (Gymno-
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