Bermuda and the Sargasso Sea

Chapter 22

Bermuda and the Sargasso Sea Struan R. Smith⁎, Tammy Warren† ⁎

Natural History Museum, Bermuda Aquarium Museum and Zoo, Bermuda, †Department of Environment and Natural Resources, Bermuda Government, Bermuda

22.1  THE DEFINED REGION 22.1.1  Bermuda and the Sargasso Sea 22.1.1.1  Geography, Topography, Geological Description Bermuda is an isolated island in the western Sargasso Sea (Fig. 22.1) formed from volcanic activity about 110 and 33 Ma, with two adjacent shallow seamounts (Challenger and Plantagenet) and one deeper seamount (Bowditch) occurring within 25 nm of Bermuda. Several distant deep seamounts (Crescent, Siboney, George) and the Muir seamount range also occur within Bermuda’s exclusive economic zone (EEZ) (Fig. 22.2). The prevailing oceanographic conditions of the Sargasso Sea have been described recently (Lomas, Bates, Buck, & Knap, 2011a) and were broadly characterized by Knap, Connelly, and Butler (2000). The global significance of the Sargasso Sea as a net carbon sink in this era of anthropogenically forced climate change has been recognized (Lomas, Bates, Buck, & Knap, 2011b). The islands of Bermuda are formed from calcareous marine sediments, which accumulated on the submerged volcanic stump, termed the Bermuda Pedestal, from the start of the Pleistocene (~1.2 Ma, Land, Mackenzie, & Gould, 1967; Rowe, 1998). Coring studies have determined the carbonate/volcanic interface to be about 30–40 m below sea level (Reynolds & Aumento, 1974). During the four low sea level stands of the Pleistocene, the exposed sediments were blown into dunes and cemented by diagenetic processes (Land, 1970). Vegetation and soil formation, in part due to Saharan dust inputs and weathered native volcanic material (Muhs, Budahn, Prospero, Skipp, & Herwitz, 2012), further stabilized the dunes. The accumulation of a series of dunes through the Pleistocene created hills with average elevations from 30 to 50 m above sea level, with the highest point at 78 m. The main island of Bermuda lies on the SE edge of the Bermuda Pedestal. The archipelago is about 30 km long, with several protected sounds that connect to the extensive North Lagoon, which is about 20 km × 40 km in size but with a maximum depth of only 18 m (Fig. 22.3). The North Lagoon supports extensive patch reefs, constructed on Pleistocene dunes and the shallow (3–10 m) rim reef defines the edge of the lagoon. Seaward of the rim reef are extensive terrace reefs that grade from 10 m down to ~55 m, before a shelf break occurs. The south shore of Bermuda contains extensive sand beaches, interspersed with eroding cliff faces. Distinctive algal vermetid “boiler reefs” protect the beaches and shoreline in a nearly continuous band along the southern coast (Coates et al., 2013, chap. 10; Logan, 1988). Bermuda is surrounded by the Sargasso Sea and is profoundly influenced by the Gulf Stream and mesoscale eddies, which helps maintain seawater temperatures between 18°C and 29°C (McGillicuddy Jr. et al., 1999; Steinberg et al., 2001). The warm ocean ameliorates atmospheric fronts that emerge from North America (Coates et al., 2013, chap. 10), allowing a subtropical climate, which has persisted throughout the Pleistocene, as indicated by terrestrial fossil snail assemblages (Hearty & Olson, 2010). Two oceanographic time series, Hydrostation S, and the Bermuda Atlantic Time Series (BATS), have documented secular, seasonal, and decadal-scale changes in the oceans off Bermuda (Steinberg et al., 2001). Clear upward trends in seawater temperature, salinity, and aragonite saturation state are evident in the time series (Bates, 2012; Lomas et al., 2011a). A tide gauge on Bermuda has revealed a steady ~2 mm year−1 rise in sea level since the 1930s (NOAA, 2018). Bermuda’s position in the Western Atlantic has made it vulnerable to hurricane strikes and near misses (http://www. bermuda-online.org/climateweather.htm) with recent impacts from Fabian (Cat 3, 2003), Gonzalo (Cat 2, 2014), and Nichole (Cat 3, 2016). Large slow-moving storms to the distant south of Bermuda, for example, Hurricanes Irma and Maria (2017), can develop sustained high seas (3–8 m) around the island for several days. World Seas: An Environmental Evaluation. https://doi.org/10.1016/B978-0-12-805068-2.00026-7 © 2019 Elsevier Ltd. All rights reserved.

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FIG. 22.1  Bermuda and its location in the Sargasso Sea. Bermuda lies in the North Atlantic gyre, formed by the ocean currents that circulate the waters of the Atlantic Ocean.

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FIG. 22.2  Bermuda and the seamounts within the EEZ. (Courtesy of Mandy Shailer, Dept. of Environment and Natural Resources.)

22.2  NATURAL ENVIRONMENTAL VARIABLES, SEASONALITY Bermuda’s high latitudinal position (32°N) imposes strong seasonality on day length and both air and water temperatures (Coates et al., 2013, chap. 10). This variation results in highly seasonal coral growth rates (Cohen, Smith, McCartney, & van Etten, 2004), seagrass productivity (CARICOMP, 1997a; van Tussenbroek et  al., 2014), mangrove productivity (CARICOMP, 1997b) and the productivity of plankton in lagoonal waters (Bodungen, Jickells, Smith, Ward, & Hillier, 1982) and the Sargasso Sea (Steinberg et al., 2001). Rainfall is evenly spread throughout the year (~12 cm month−1). The karst carbonate rock reduces runoff to the coastal nearshore environments but groundwater, elevated in nitrate, can impact enclosed lagoons and bays (Simmons & Lyons, 1994). Bermuda is affected by broader climatic patterns such as the North Atlantic Oscillation and ENSO, and these signals are recorded in coral skeletons (Cohen et al., 2004; Crueger, Kuhnert, Patzold, & Zorita, 2006; Kuhnert, Crueger, & Patzold, 2005). But the pattern of continental fronts leaving North America has the most immediate and direct influence on local climate (air temperature and rainfall), particularly in the Fall, Winter, and Spring (Bermuda Weather Service, 2017; Jickells, Knap, Church, Galloway, & Miller, 1982). The Bermuda-Azores High predominates in the summer months, reducing the influence of North American air masses.

22.3  MAJOR COASTAL AND SHALLOW HABITATS Bermuda is surrounded by extensive coral reefs, characterized by a reduced diversity of Caribbean species and a limited number of endemic marine species (Coates et al., 2013, chap. 10; Sterrer, 1998). The shallow rim reef (3–10 m) demarcates the edge of the North Lagoon, within which a great diversity of shallow patch reefs (1–6 m) are located (Fig. 22.3; Garrett, Smith, Wilson, & Patriquin, 1971; Logan, 1988). Seaward of the rim reef is the outer terrace reef, which is very broad on the north side and slopes from 10 to 30 m over 3–5 km. The terrace reef is compressed within 2 km of the South shore boiler

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FIG. 22.3  Bermuda’s North Lagoon contains thousands of shallow patch reefs (1–5 m) and is separated from the surrounding ocean by the outer rim reef (3–10 m).The shallower terrace reefs are found from 10 to 30 m. Seaward is the mesophotic coral reef ecosystem that extends out to a ~55-m shelf break and well-developed to 300 m. Numerous MPAs were established in the 1990s, and seasonally protected areas for serranids were established initially in 1974 and then expanded in the 2000s. (Courtesy of Dr. Thad Murdoch, Bermuda Reef Ecosystem Analysis and Monitoring Project.)

reefs (Fig. 22.4). Seaward of the terrace reefs is the mesophotic coral ecosystem (MCE), which begins at 30 m, then the reef drops to 45 m and finally to ~55–60 m at the shelf break (Iliffe, Kvitek, Blasco, Blasco, & Covill, 2011). Beyond this break, the steep slope descends to ~4000 m with the MCE extending to over 300 m, due to high light penetration in the clear oceanic waters (Goodbody-Gringley, Noyes, & Smith, n.d.). Coral coverage across Bermuda’s reef zones has remained quite stable since the early 1990s (Jackson, Donovan, Cramer, & Lamb, 2014; Murdoch & Murdoch, 2016). Although coral bleaching occurs frequently in Bermuda (CARICOMP, 1997c; Cook, Logan, Ward, Luckhurst, & Berg Jr., 1990; Gleeson & Strong, 1995), there is little mortality. Coral diseases are prevalent at low levels and have not caused significant mortality (Jones, Johnson, Noyes, & Parsons, 2012; Smith et al., 2013, chap. 13; Weil & Cróquer, 2009). The MCE does have distinctive deep coral communities (Bongaerts et al., 2017; Locke, Bilewitch, & Coates, 2013, chap. 14) with abundant and diverse antipatharian communities (Wagner & Shuler, 2017). Algal biomass can be locally abundant and there are distinctive plankivorous fish communities at depth (GoodbodyGringley et al., n.d.; Pinheiro et al., 2016). The North Lagoon, Rim reef zone, and the protected inshore bays and harbors have supported extensive seagrass meadows of Thalassia testudinum, Syringodium filiforme, and Halodule spp. historically (Bodungen et al., 1982; South, 1983; Ward, 1999). However, anthropogenic impacts (declining water quality, boat moorings) and increased grazing by green sea turtles have reduced seagrass coverage and also eliminated some seagrass beds (Fourqurean, Manuel, Coates, Kenworthy, & Smith, 2010; Murdoch et al., 2007; van Tussenbroek et al., 2014; Ward, 1999). The diminutive seagrass Halophila decipiens and diverse fleshy and calcareous algae are common in the soft sediments of the deeper inshore basins and the North Lagoon (Manuel, Coates, Kenworthy, & Fourqurean, 2013).

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FIG. 22.4  Emergent algal vermetid “boiler” reefs (in top left of image) lie in a nearly continuous belt along the South Shore of Bermuda. Seaward, the terrace reefs (10–20 m) are dominated by brain corals, star corals, and soft corals. (Courtesy of Chris Burville.)

Bermuda has small coastal mangroves located in protected bays with only two tree species, Rhizophora mangle and Avicennia germinans (Thomas, 1993). Over 50% of the historic mangrove area has been lost to coastal development (Sterrer & Wingate, 1981). Rising sea level (>2 mm year−1, NOAA) has forced mangrove retreat since the late 19th century (Ellison, 1993). Today, hurricane damage reduces the seaward edge of many mangroves and limited seedling recruitment, due to higher sea level, prevents recovery (Chadderton, 2013), leading to sustained forest loss over time (Fig. 22.5). Bermuda has very limited intertidal mudflats in the inshore basins. Some of the protected harbors are deep, to 15–18 m, and quite muddy. These basins support a distinctive Oculina spp. community with a great diversity of associated bivalves and sponges (Bodungen et al., 1982; Meischner, Horst, & Kuhn, 1981).

22.4  THE SARGASSO SEA (OCEANIC ECOSYSTEMS) Bermuda is located in a truly oceanic environment, in the western part of the Sargasso Sea, and thus is in a distinctive position to experience and observe the changing ocean. Bermuda has been a nexus for ocean research since the visit of HMS Challenger in 1875 and the establishment of the Bermuda Biological Station in 1906 (later the Bermuda Institute for Ocean Sciences, BIOS). Time series oceanographic research at Bermuda began in 1952 and has expanded in diverse dimensions over time (plankton diversity, particle flux, biogeochemical cycles, atmospheric exchanges, ocean acidification), establishing Bermuda as a singular location for assessing long-term changes in the mid-Atlantic Ocean (Lomas et al., 2011a). Today, there is a clear focus on climate-related studies with compelling evidence of change in surface and mid-water temperature, salinity, and aragonite saturation state (Bates, 2012; Steinberg et al., 2001). Fascinating patterns of variation and diversity in water column microbial and plankton productivity have emerged (Carlson et al., 2004; McGillicuddy Jr. et al., 2007; Morris et al., 2005). The diverse surface, mid-water, and abyssal biological communities in the Sargasso Sea and around Bermuda have been studied episodically and summarized in a series of scientific reports by the Sargasso Sea Alliance (now the Sargasso Sea Commission; http://www.sargassoseacommission.org/publications-and-news/sargasso-sea-alliance-science-report-series/). The Commission is a broad Bermuda-led initiative for international recognition, collaboration, and conservation of the Sargasso Sea. The patterns of vertical distribution and abundance of plankton and fishes in the Sargasso Sea were summarized recently by Angel (2011). The distribution of fishes from the surface to 5000 m in the Sargasso Sea was described by Sutton, Wiebe, Madin, and Bucklin (2010), while Bucklin et al. (2010) catalogued the diversity of zooplankton, as part of a Census of Marine Life cruise in 2003. Both studies created genetic catalogues of the sampled taxa. There has been a renewed interest in studying the spawning locations of American and European eels (Anguilla spp.) in the Sargasso Sea, southwest of Bermuda (Miller et al., 2015; Miller & Hanel, 2011). These studies seek to understand more clearly the factors that may influence the survival of the leptocephali on their return journeys to rivers in Europe and North America.

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FIG. 22.5  Loss of the mangrove forest in Hungry Bay, 1898–2012. This bay lies on the South Shore of Bermuda and is frequently exposed to hurricane winds and storm surge. Coastal erosion since Hurricane Fabian (2003) has destroyed some of the protective peninsula sheltering the mangrove, making it more vulnerable to future storm damage. (Courtesy of Mandy Shailer, Dept. of Environment and Natural Resources.)

Butler, Morris, Cadwallader, and Stoner (1983) and Stoner and Greening (1984) intensively studied the Sargassum community around Bermuda from the mid-1970s to the early 1980s. A very long hiatus in Sargassum research was interrupted by a short study by Huffard, von Thun, Sherman, Sealey, and Smith Jr. (2014) that indicated significant changes in the mobile and epifaunal communities associated with Sargassum. Smith, Choyce, and Andrew (in preparation) has extended research on the Sargassum community, also finding peculiar patterns of super-abundance of some taxa and declines of formerly abundant species (Fig. 22.6). Choyce (2016) documented changes in the epifaunal and epiphytic community, compared to the 1970s, with a virtual absence of crustose coralline algae, taxa that are susceptible to ocean acidification (Kuffner, Andersson, Jokiel, & Mackenzie, 2008). The Sea Education Association (www.sea.edu) has documented the remarkable recent shift of the species characteristics of Sargassum in the Caribbean and Atlantic (Schell, Goodwin, & Siuda, 2015) with variants Sargassum natans VIII and Sargassum fluitans III, known from the 1930s (Parr, 1939), displacing S. natans I as the dominant “species” from 2015 to 2017 around Bermuda (Smith et al., in preparation). Fishes associated with Sargassum (Lapointe, West, Sutton, & Hu, 2014) have not been well documented in regard to changes over time. Smith (2014) reviewed the knowledge of the geology and biology of seamounts in the Bermuda Exclusive Economic Zone (EEZ). The isolated Crescent, Siboney, and George seamounts are unstudied. However, the Muir seamounts were mapped and the benthic community described (Adkins, 2003; Robinson et al., 2007) and contrasted to the New England seamounts and the Corner Rise seamounts. Genetic analyses of several taxa showed some affinity to the adjacent seamounts but also some distinctive haplotypes (Cho & Shank, 2010; Thoma, Pante, Brugle, & France, 2009). The demersal fish communities on the Muir seamounts were also described (Auster, Moore, Heinonen, & Watling, 2005; Canache, 2007). The Bermuda Seamount is a key way-point in the migratory paths of pelagic fishes with many arriving in Bermuda in the spring and summer months (Faiella, 2003). Several Yellowfin tuna (Thunnus albacares) were tagged and then recaptured at Bermuda after ~1 year, suggesting a seasonal migratory movement (Luckhurst, Trott, & Manuel, 2001). Luckhurst, Prince, Llopiz, Snodgrass, and Brothers (2006) showed that istiophorid billfishes are completing a spawning run near Bermuda in July. Tagging studies of Tiger sharks (Galecerdo cuvier) at Bermuda have revealed their extensive movements throughout the Atlantic over the course of the year, with a return to Bermuda each summer (Lea et al., 2015).

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Latreutes fucorum per kg or L

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(A) Gnescioceros sargassicola per kg or L 2500

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2000 1500 1000 500

/1

0 1 97

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81

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92

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(B) FIG. 22.6  Change in patterns of abundance of (A) the Sargassum shrimp (Latreutes fucorum) and (B) the Sargassum flatworm (Gnescioceros sargassicola), in dip net samples from early 1970s (Butler et al., 1983) to 2012–15 (Smith et al., in preparation). (Courtesy of Struan Smith.)

Similarly, tagging studies of two nesting sea birds on Bermuda, the Longtail tropicbird (Phaeton lepturus catesbyi), and the endemic Bermuda petrel (Pterodroma cahow) also show broad ocean-wide foraging patterns in the nonbreeding period (Madeiros, Flood, & Zufelt, 2014; Mejias, Wiersma, Wingate, & Madeiros, 2017). Additionally, the Bermuda petrel undertakes remarkably long foraging flights north and west to the Gulf Stream to support their nestlings. Bermuda has also been a well-known stopover in the northerly migration of Humpback whales (Megaptera novaeangliae) from the calving grounds in the Northern Caribbean to their feeding grounds off New England and maritime Canada (Stevenson, 2011). The Whales Bermuda project (https://www.whalesbermuda.com) has conducted an intensive surveillance of whale activity around Bermuda. This effort has expanded the catalogue of identified whales from ~150 in 2005 to ~1500 in 2017, discovered a wider temporal period of residency and the possibility of calving activity (Stevenson, Rigaux, Stringer, & Clee, 2017). Other whales observed around Bermuda, or stranded, include the Sperm whale (Physeter macrocephalus), Minke whale (Balaenoptera acutorostrata), Pilot whale (Globocephala melaena), Cuvier’s Beaked whale (Ziphius cavirostrus), and the Pygmy Sperm whale (Kogia breviceps). Most interestingly, a recent acoustic study was able to detect both Minke and Fin whales (Balaenoptera physalus physalus) around Bermuda for several months (Sirovic, Hildebrand, & Macdonald, 2016). The Common dolphin (Delphinus delphis) was reported as common around Bermuda by Sterrer (1986). More recently, Bottlenose dolphins (Tursiops truncatus) are frequently encountered along the shelf break (55 m) around Bermuda and on the offshore Challenger and Plantagenet banks (Klatsky, Wells, & Sweeney, 2007). A new effort to catalogue dolphins is progressing and may clarify the patterns of dolphin diversity near Bermuda. In 2016, the Bermuda Wild Dolphin Project deployed satellite tags on Bottlenose dolphins. Several demonstrated strong site fidelity around Bermuda and the offshore banks but one moved out of the Bermuda EEZ towards the New England seamount area (https://dolphinquest.com/ bermuda-wild-dolphin-project/). Another set a deep diving record for the species at 1008 m. Ryan et al. (2013) reported acoustic data on the occurrence of Striped dolphin (Stenella coeruleoalba) near Bermuda.

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22.5  CLIMATE CHANGE IMPACTS The clearest impact of climate change in Bermuda is the rising sea level. Ellison (1993) describes the retreat of a large mangrove forest located in Hungry Bay, a distinctive southern coastal embayment, in response to an increase in the rate of sea level rise since the late 19th century. Her dating of mangrove peat clearly shows the rate of sea level rise increasing to 14 cm per century in the early 20th century, from 5 cm per century from 1400 to 1850. A series of NOAA tide gauges in Bermuda now show a rate increase to ~20 cm per century (~2 mm year−1, NOAA). The mangrove retreat is a response to hurricane damage where recolonization is impossible due to water depth at the current mangrove forest front. The coastal map of Lt. Savage in 1898, historical photographs and a series of aerial photos, from 1941, reveals the progressive loss of mangroves, compounded by the erosion of a protective seaward peninsula that now admits destructive storm surge and reef sediments (see Fig. 22.5). Bermuda’s islands are lithified carbonate dunes, formed in the Pleistocene during high sea level stands (Hearty & Vacher, 1994). The coastal rocks are vulnerable to erosion and after Cat 3 Hurricane Fabian caused significant erosion and impacts on infrastructure in 2003, a study of the coasts was conducted to evaluate future vulnerable areas (Bermuda Government, 2004). A broad summary of climate change impacts on Bermuda was published by Glasspool (2008). Tourism contributes significantly to Bermuda’s GDP, and several aspects of tourism infrastructure are vulnerable to rising sea level and storm surge, although most hotels were built prudently at safe elevations, due to past experience. The oceanographic time series show clear increase in surface water temperature over the past 60 years and an increase in salinity, but these changes have not resulted in measurable changes in coastal ecosystems around Bermuda. Coral bleaching, induced by above normal summer water temperatures (CARICOMP, 1997c; Cook et al., 1990; Gleeson & Strong, 1995), recurs frequently, but mortality is not commonly observed. This is due in part to Bermuda’s high latitudinal position, where insolation declines through the summer and the passing of hurricanes can result in mixing that reduces surface water temperatures (Nelson, 1998). The question of the effects of ocean acidification has been directly addressed on Bermuda’s reefs. The oceanographic time series show clear changes in aragonite saturation state over time. Bates, Samuels, and Merlivat (2001) and Bates, Amat, and Andersson (2010) have examined changes in aragonite saturation state on Bermuda’s reefs and modeled the possible effects on coral and reef growth. Cohen, Jachowski, Jones, and Smith (2008) showed that coral growth rates have declined in the latter half of the 20th century. Also, juvenile coral calcification rates are reduced (de Putron, McCorkle, Cohen, & Dillon, 2011). Courtney et al. (2016) examined variation in reef calcification processes. The seasonal character of Bermuda’s reefs appears to have some buffering capacity that offsets the predicted impact of an increasing aragonite saturation state, in part because of other calcification and community respiration processes. Courtney et al. (2017) have also shown that temperature is the main driver of reef calcification processes on Bermuda’s reefs and predict that if a global reduction in CO2 emissions can be accomplished in the 21st century then Bermuda reefs might see a slight increase in net calcification, as long as the probability of crossing thermal thresholds for coral bleaching can be minimized.

22.6  HUMAN POPULATIONS AFFECTING THE AREA Bermuda is a small densely populated island with significant coastal infrastructure development that dates back to the 18th century (two ports and a naval Dockyard). An airfield was created by dredging and filling a large area of Castle Harbor in 1941–43 with significant impacts, in terms of loss of coral reefs, seagrass beds, and mangroves (Flood, Pitt, & Smith, 2005), imposing a permanent reduction of tidal water flow and an increased sedimentation regime that resulted in declines in reef health. The economy is service-oriented and dependent on international business, financial services, and tourism. A large volume of solid waste is incinerated daily, and the ash wastes solidified with concrete and disposed of as a foreshore reclamation in Castle Harbor, along with bulk metal wastes. Although hazardous waste recycling is successful in Bermuda, significant levels of trace metals and organic contaminants are present around the deposition site (Jones, 2010), which are stressors to nearby corals (Morgan, Edge, & Snell, 2005). There are three sewage outfalls that appear to have limited impacts on adjacent benthic communities (Jones et al., 2012; Webster & Smith, 2000), perhaps due to the dynamic hydrographic conditions and water depths. The bulk of sewage is disposed of in individual domestic cesspits that drain through the island’s limestone. Consequently, ground waters are enriched in nitrate (Simmons & Lyons, 1994) and deliver measurable quantities of N to the inshore waters, where fecal coliforms are detected frequently (Jones, Parsons, Watkinson, & Kendell, 2010). The more enclosed inshore bays and sounds support elevated plankton levels, with increases of del-N in seagrasses and corals (Baker, Murdoch, Conti-Jerpe, & Fogel, 2016; Bodungen et al., 1982; Fourqurean, Manuel, Coates, Kenworthy, & Boyer, 2015; Wang et al., 2015). Maritime accidents in Bermuda have diminished over time due to improved navigational aids, although cruise ship groundings have occurred recently (Norwegian Crown, 2006; Norwegian Dawn, 2015) with substantial reef damage and

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FIG. 22.7  High densities of microplastic particles, common disposable items, and many bulkier items (fishing gear, plastic bottles, boxes) are frequently deposited at the highwater tideline on South Shore beaches. Repeated beach surveys from 2010 to 2015, done after a recent high tide, found the plastic mass to range from 0.1 to 10 g m−2, and averaging ~100 pieces per m2. (From Anne Hyde, Keep Bermuda Beautiful.)

chemical contamination from the residual antifouling bottom paint (Jones, 2007). The advent of large Panamax cruise ships has required the redevelopment of port facilities, which resulted in increased sedimentation in the navigational channel that runs through the North Lagoon (Jones, 2011). A recent channel realignment to accommodate post-Panamax cruise ships required coral transplantation and sediment monitoring as mitigation (BEC, 2015; Lester, White, Mayall, & Walter, 2016). There are concerns about the arrival of marine invasive species associated with vessel traffic. Bermuda is supplied by three domestic cargo vessels on a weekly basis from ports in Florida and New Jersey. There are sporadic visits from other cargo vessels (car carriers, bulk gravel carriers, oil and gas tankers) from the Caribbean and Canada. Two to three cruise ships visit the island each week from April to November from US ports, with several transitioning from the Mediterranean and Caribbean seasonally. Similarly, there is significant private motor yacht, sport fishing, and sailing vessel traffic, primarily with the Caribbean, eastern US, and the Mediterranean. Preliminary assessment studies have detected several novel species that may have been introduced recently on vessel hulls (K. Holzer, pers. comm.). A Sargasso Sea Alliance report examined the impacts of maritime traffic on the Sargasso Sea (Roberts, 2011), which revealed the great volume and diversity of shipping activity and concomitant broad range of environmental risks (pollution, waste disposal, ship strike, ballast water discharge, etc.). Sirovic et  al. (2016) assessed acoustic noise from maritime traffic around Bermuda and concluded that there is a potential impact from increased vessel activity as the result of the Panama Canal expansion. Recent studies have also documented high levels of macro and microplastic debris in the Sargasso Sea (Eriksen et al., 2014; Siuda, 2011), and significant quantities frequently strand on Bermuda’s beaches and coastlines (Fig. 22.7).

22.7 RESOURCES Bermuda has taken strong management action to reverse declining reef fish stocks with a ban on the use of the traditional Antillean-style fish traps (Butler, Burnett-Herkes, Barnes, & Ward, 1993), the establishment of buoyed protected areas, and a seasonal closure of spawning aggregation sites (Luckhurst, 2010) (Box 22.1 Spawning aggregations). Luckhurst and O’Farrell (2013) documented the fairly quick recovery of scarid and acanthurid populations, although strong recruitment was not observed directly. An increase in the abundance of meso-reef predators (trumpetfishes) was observed following the 1990 fish pot ban (O’Farrell, Luckhurst, Box, & Mumby, 2015) (Box 22.2 Fish pots). However, Murdoch and Murdoch (2016) reported low densities of reef predators (snappers and groupers) across all reef zones in 2010–11.

BOX 22.1  Successful Serranid Spawning Aggregation Site Protection The discovery of a deep (~30 m) spawning aggregation of Black grouper (Mycteroperca bonaci) outside of two seasonally protected areas, established in the 1970s to protect spawning aggregations of the Red hind (Epinephelus guttatus), resulted in the inclusion of the site into a redesigned protected area in 2005. Another Black grouper spawning aggregation was discovered several years later but within another seasonally protected area. Several hundred fish have been observed at these locations (below), and recent acoustic telemetry data indicate that they persist at these sites for over half the year. This information led to an extension of the closure period from May to November.

(Courtesy of Chris Burville.)

BOX 22.2  Sustained Parrotfish Recovery Through Management Bermuda’s removal of nonselective “fish pots” as the primary tool for reef fish harvest in 1990 and a subsequent ban on the capture of all parrotfishes (Scaridae) in 1993, set the stage for the recovery of depleted reef fish stocks. Today, schools of scarids, such as the intermediate phase Scarus vetula, terminal phase Sparisoma viride and S. aurofrenatum, and intermediate phase S. aurofrenatum (below), are commonly seen across most reefs today. Formerly rare scarid species, such as Scarus coelestinus, Scarus coeruleus, and Scarus guacamaia, are also frequently observed on reefs and in nearshore bays.

(Courtesy of Chris Burville.)

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Reef fishing remains a significant pressure on marine resources in Bermuda with close to 200 commercial fishing vessels engaged with hook-and-line, harvesting about ~134 metric tonnes per annum of groupers, snappers, and miscellaneous reef fishes, in 2015 (Bermuda Government Statistics Dept, 2016). Recreational fishing is prevalent but unregulated, except for licensing of spearfishing and lobster diving. There are bag limits and size restrictions for some, but not all reef fishes. The prospect of licensing recreational fishers using hook-and-line has proved to be politically contentious. Many Bermudians believe that they have a right to fish, stemming from a deep cultural heritage that includes subsistence fishing, and thus they are resistant to the idea of having a license and reporting their catch. A Bermuda Government Green paper reviewed the status of fishing, fisheries, and the state of the marine environment in the late 1990s (Bermuda Government, 2000). This led to a White paper (Bermuda Government, 2005) that advocated for (1) sustainable use of marine resources though adaptive management and evidence-based decision-making, (2) economic rent fees for consumptive users, such as fishermen, (3) a Fisheries Commission to issue commercial fishing licenses and vet new fishers, (4) improved protective legislation including expanded protected areas, permitting, and environmentally friendly moorings, and (5) cross-Ministry collaborations and a Ministerial review panel to prioritize research topics and advocate for funding. Limited progress has been made on some of the proposed initiatives. A total economic valuation study of Bermuda’s reefs was conducted by Sarkis et al. (2013, chap. 15) and estimated them to be worth about US$730 million per year, with over US$400 million value for tourism, US$266 million for coastal protection, US$36 million in recreation and cultural value, and US$5 million for fisheries. The threats to Bermuda’s reefs were recently summarized by Smith et al. (2013), identifying coastal development, shipping traffic and groundings, fishing pressure, coral diseases, land-based sources of pollution, and climate change as the main concerns. The invasive lionfish (Pterois spp.) has been studied intensively and appears to have had limited impacts to date, showing a more varied diet than lionfish in the Caribbean (Eddy et al., 2016). Intensive culling and trapping may be restricting population growth, although the lionfish are widely distributed in Bermuda’s deep reefs (Andradi-Brown et al., 2016). The reduction in fishing pressure on Bermuda’s reefs after 1990 was balanced in part by increased fishing for pelagic species (primarily Wahoo and Yellowfin tuna), along the shelf break at ~55 m, and in particular, the offshore Challenger and Plantagenet (Argus) Banks, located 15 and 25 nm SW of Bermuda, respectively (Faiella, 2003; Luckhurst et al., 2001). There has also been growth in billfish tournaments, in early summer, coinciding with seasonal migration patterns (Graves, Luckhurst, & Prince, 2002; Luckhurst, 2000; Luckhurst et al., 2006). Today, pelagic species consistently constitute between 35% and 50% of the total commercial nonbait finfish catch each year, although the overall commercial pelagic catch has declined since 2011, along with the number of fishing vessel hours at sea (Bermuda Government Statistics Dept, 2013, 2016). An estimation of the recreational catch of pelagic species in the late 1990s found that these fishers caught the equivalent of 17% of the commercial catch weight but with disproportional targeting of Yellowfin tuna (Thunnus albacares), equivalent to 42% of the commercial catch (Hellin, 1999). A 2011 recreational fishing survey found that Wahoo (Acanthocybium solandri) and Yellowfin tuna were still two of the most commonly targeted species by recreational fishers, and the results of the survey suggest that total annual landings from the recreational fishery (pelagics and reef fish combined) could equal 82% of the commercial fishery landings (Pitt & Trott, 2013). The potential for offshore commercial long-line fishing, as a prospective artisanal fishery, was explored in an experimental study in the Bermuda EEZ in 2007 and found that commercial species (Swordfish and tunas) were available (Trott et al., 2010). To date, only two local fishers are licensed to use a pelagic longline and they only fish infrequently. Bermuda is currently allocated quotas and catch limits from the International Commission for the Conservation of Atlantic Tunas (ICCAT) for a number of pelagic fish species (including Bluefin tuna, Thunnus thynnus and Swordfish, Xiphias gladius), but harvest levels of these and other large pelagic species are extremely low. Currently, Bermuda has no active mariculture projects, although scallop culture has been successful (Sarkis, Couturier, & Cogswell, 2006; Sarkis, Helm, Cogswell, & Farrington, 2003; Sarkis, Helm, & Hohn, 2006) but did not achieve a ­commercial scale of development. Preliminary culture work has been conducted for a local holothurian, Isosticopus badionotus (Sarkis, 2015). Parson and Edwards (2011) reviewed the geological features of the Sargasso Sea area and the potential for extractable nonliving resources. There is no oil, gas, or mineral exploration or extraction plans for Bermuda or within her EEZ. One license was issued to explore for minerals on the slope of the Bermuda Seamount but no active work has been done since 2007. Limited geological studies in the EEZ have not found any substantive mineral or hydrocarbon resources, although ferromanganese crusts and nodules have been noted (Addy, Shipley, & Ewing, 1974) and recent rock and fossil coral samples on the Muir seamounts were heavily coated with ferromanganese crusts (Adkins, 2003).

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22.8  MANAGEMENT REGIMES Bermuda has a long history of proactive and reactive conservation legislation and policy in regard to its marine resources, dating back to the 17th century (Smith-Vaniz, Collette, & Luckhurst, 1999). Several key Acts regulate fisheries, control activities, and protected species and habitats (http://environment.bm/legislation-and-policy). They have been updated as needed because there is inherent flexibility in Bermuda’s Parliamentary system of government that can allow amendments to existing legislation without promulgation of new laws. The main reactive marine resource management act was the 1990 fish pot ban that stopped the use of a devastating tool that had depleted reef fish stocks (Butler et al., 1993). Bermuda formed the Sargasso Sea Alliance (SSA) in 2010 to assess the health and value of the Sargasso Sea (Trott, Trott, & Pitt, 2010), leading to a series of scientific volumes that summarized the different dimensions of this distinctive oceanic ecosystem, from microbes to eels to cetaceans (http://www.sargassoseacommission.org/publications-and-news/ sargasso-sea-alliance-science-report-series). This effort led to the formation of the Sargasso Sea Commission in 2014 and the promulgation of the Hamilton Declaration, which asserts nonbinding support for international collaboration to protect the Sargasso Sea. To date, Azores, Bahamas, British Virgin Islands, Canada, Cayman Islands, Monaco, United Kingdom, and United States are signatories to the Declaration, in addition to Bermuda. A contemporaneous conservation initiative, termed the Blue Halo, began in 2011 with the support of the Pew Foundation, as one of their Ocean Legacy projects. The goal was to establish a large marine protected area within the Bermuda EEZ to show leadership in the protection of the Sargasso Sea. Local environmental NGOs formed the Bermuda Alliance for the Sargasso Sea and worked to develop educational products in support of these two initiatives. After public consultation, a town hall meeting, and an opinion poll, the Bermuda Government did not proceed with the establishment of any additional protection within the EEZ but pledged to gather more data on potential economic costs and benefits of further restrictions at some future point. Some Bermudians were not convinced of the need for further protection and were concerned about possible future restriction of access to fisheries or mineral resources. The contrasting opinions of the proposed conservation measures were reviewed by Gruby et al. (2017). Although some information was available in an economic valuation report produced by the SSA (Sumaila, Vats, & Swartz, 2013) and the broader value of the Sargasso Sea ecosystem services and fisheries benefits have been outlined (Hallett, 2011; Pendleton, Krowicki, Strosser, & Hallett-Murdoch, 2015), more data, modeling and environmental impact assessments are needed. In the final preparation of the “Sargasso Sea Geographical Area of Collaboration,” defined in the Hamilton Declaration, the Bermuda Government felt obliged to remove its EEZ from the Area, due in part to a perception that there would be a diminished sovereignty of its EEZ. One of the motivating issues driving the proposals for more protection in Bermuda’s EEZ was the concern about illegal, unreported, and unregulated (IUU) fishing. A Catapult study addressed the problem by a review of satellite and vessel AIS data. Only two examples of possible illegal fishing activity were detected at the periphery of the EEZ from 2014 to 2016 (Catapult, 2016). The initial stages of a marine spatial planning exercise for the Bermuda reef platform have been executed but broad consultation on the matter has not occurred. A MARXAN planning exercise was performed for Bermuda’s reef fishes to determine possible additional marine protected areas (Yates, 2010). Bermuda is not a signatory to the Convention on Biological Diversity and is not actively pursuing the set goals for 2020. Efforts have been considered to declare parts of Bermuda’s marine environment as Other Areas of Effective Conservation Measures (OECM), but the process and affirmation of these designations are still under discussion.

22.9  SUMMARY, PROGNOSES, OR NEEDS The health of the Sargasso Sea remains a significant concern to Bermuda because of clear impacts of climate change and other human influences. Changes in the pelagic ecosystem are not well-known, apart from the broader issues of stock depletions in the Atlantic (FAO, 2016; ICCAT, 2017; Worm & Branch, 2012) and IUU fishing, and this generates concern about food security. Rising sea level and intense hurricane activity will challenge Bermuda’s coastline and some infrastructure, but the relatively high elevation of much of the inhabited parts of the island will limit these impacts somewhat. However, losses of tourism infrastructure may impact Bermuda’s economy. Bermuda’s coral reefs appear to be healthy, in part due to the high latitudinal position that has limited the impacts of coral bleaching but also partly due to many effective fisheries management measures. Reef fish stocks appear to have recovered to some degree, particularly herbivorous fishes, in response to proactive changes in fishing practices. Recreational fishing remains very loosely controlled, with no licensing or reporting, except for lobster diving and spearfishing, but there must be a significant impact on some species. Cultural heritage concerns appear to preclude robust discussion about the need for regulation of recreational hook-and-line fishing.

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Although Bermuda benefits from the presence of the scientists at BIOS, the current research effort on the local marine environment has been greatly attenuated since 2010, due to reduced government funding for research. This has limited opportunities for young scientists to gain experience and graduate degrees and this will have a long-term impact in terms of succession and knowledge transfer. The decreased amount of comprehensive and timely data will limit effective decisionmaking about our marine resources.

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546  World Seas: An Environmental Evaluation

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FURTHER READING Calder, D. R. (1998). Hydroid diversity and species composition along a gradient from shallow waters to deep sea around Bermuda. Deep-Sea Research Part I, 45, 1843–1860. Dodge, R. E., & Vaisnys, J. R. (1977). Coral populations and growth patterns: responses to sedimentation and turbidity associated with dredging. Journal of Marine Research, 35(4), 715–730.