Surf eutrophication?

~larme Polhaion Bulletin. Vol. Ih, Nt~. 1 I. p p 425-42¢~. 1985 Printed in Great Britain

Surf Eutrophication ? At False Bay near Cape Town, South Africa, surf discolouration from blooms of the diatom Anaulis birostratus has been considered a result of sewage effluent beach discharge. Similar surf blooms are known to occur on other sand beaches around the world. Several had been considered sewage generated, but this was subsequently disproved. At the Conference on Estuarine and Coastal Pollution at Plymouth in July 1985 (Mar. Pollut. Bull., 16, 422-423), authors G. A. Eagle and H. F-K. O. Hennig proposed that there may be a variety of 'good' and 'bad' free floating algae, the latter being bloom-prone and liable to appear in high concentrations under certain conditions. They postulate that bloomprone algae tend to be slow-growing and persistent, and reach dense concentrations through being of poor food value and even toxic, hence not eaten to any great extent. (However, they have been reported by others as eaten by beach bivalves.) They may also resist bacterial decomposition. A Conference in Port Elizabeth, South Africa, in 1983 on Sandy Beaches as Ecosystems, with published Proceedings, brought together much information about these surf blooms. In view of the recent review of marine eutrophication by R. Rosenburg (Mar. Pollut. Bull., 16, 227231), it seems timely to raise the issue whether the appearance of surf blooms can legitimately be related to the concept of eutrophication. In general terms eutrophication can be taken as abnormal nutrient enrichment in a water body, associated with abnormally high primary biological production, low dissolved oxygen, and fish and shellfish kills. Commonly in shallow lakes the high production is followed by deposition and speeded lake infilling, but this is not a necessary part of eutrophication in its broadest sense. In the marine ecosystem, eutrophication is usually considered a risk only in poorly flushed shallow embayments, not on open coasts. At the 1983 Conference a variety of authors including A. McLachlan, J. Lewin, D. F. Winter, a n d others reported that the phytoplankton involved were generally species of the genera Chaetoceros, Asterionella, Aulacodiscus and Anaulus. They have been reported in professional publications from the northwest coast of the USA, the North Island of New Zealand, the south coast of South Africa, Tasmania, Brazil, Costa Rica and Panama. They appear most frequently in temperate or warm temperate regions, but the Central American reports have been supported by anecdotal accounts from Nicaragua and equatorial Zaire. I recently saw such a bloom off the west coast of Sri Lanka. Another Oddity is that R. T. Wilce and others have reported extraordinary free-living 1-15 mm diameter balls of a normally attached and world-wide filamentous brown alga Pilayella littoralis crowded into Nahant Bay, Massachusetts, and regularly occurring there each summer since before 1903. It

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appears that although the bloom organisms are usually diatoms they need not be, and that they can occur in tropical and temperate seas. The pattern of distribution and abundance of these surf blooms is as follows. They appear in patches up to tens of metres long on broad shallow surf beaches with low offshore advection speeds under onshore winds, either seasonal or persistent. Densest populations are concentrated at the off-shore rips between surf circulation cells, and are apparently maintained as dispersal bottlenecks by surface wave-driven onshore drift. The phytoplankton species float at the surface due to their ability to stabilize a surface foam consisting of small bubbles to which they attach. They are not inherently buoyant, but show daylime surfacing, hence at night are subsurface. Much of the bloom may be washed inshore and form deposits on the beach (reported up to 50 cm thick), and the cells can remain photosynthetically viable after several hours exposure, hence reactivatable by a higher tide. They generally occur in high rainfall areas, with a local nutrient source, which may be a nearby river, or recycling from the fauna within an almost closed beach or bay ecosystem. The blooms may be transient (minutes) or persistent (days), their precise position may change with surface circulation cell drift, and they may extend over kilometres of coastline or be highly localized. The blooms appear to be extreme manifestations of surf beach primary production under special conditions which tend to affect certain beaches at certain seasons, but in different ways, i.e. different species at different places. Lesser manifestations, or continuing low level surf phytoplankton production may even be the primary driving force for sand beach biological processes. The question arises then to what extent are the natural manifestations subject to nutrient limitations which waste discharges, especially sewage or treatment plant effluent, might override. In three cases examined in this context, one was considered not nutrient limited, and the other two not caused by initially suspect sewage effluent discharges, but by self-sustaining beach or bay nutrient recycling. In Nahant Bay the accumulated hundreds of tonnes of Pilayella on the beach each year required a uniform bay dissolved N concentration of only 10 ppb, just 11% of the approximately 90 ppb in the bay water. Nevertheless the phenomenon of surf discolouration occurs, and we can expect that like some naturally stinking mud flats at low tide they will on occasions be ascribed to man-made conditions. It seems reasonable that in some cases that may actually happen. What is needed at the moment is more information. I saw my Sri Lankan bloom when a tourist, and did not have the wit to take a sample and preserve it in the local arrack for identification by a friendly phytoplanktonologist, nor to check patch distribution against local sewage seepages. However, I could see that throw-net fishermen were after shoals of small fish dimpling the smooth foam surface. This editorial is a plea for pollution professionals when out on beaches for one reason or another to be more perceptive. And then to pass their notes and samples to one or other of the specialists who took part in the Port Elizabeth or Plymouth Conferences. Someone hopefully will follow up by proper investigation, with species iden425

• Marine Pollution Bulletin

tifications and primary production measures (which tend to be quite challenging in the surf habitat). For the moment it seems that most surf blooms are not driven by abnormally high nutrient loadings, and are not

Dredge Spoil Disposal Problems Although controversial topics such as the dumping of nuclear waste dominated the London Dumping Convention meeting held in September (see p. 431), harbour dredging and the disposal of spoils was a larger issue, so said the Canadian Chairman of the Meeting Mr Geoffrey Holland. Problems arise when dredged materials from ports and' harbours which are contaminated with industrial waste are dumped at sea. About 90% of the material covered by the Convention falls into this category. A report by the Permanent International Association of Navigation Congresses (PIANC) stated that contaminated dredge spoils could not always be safely disposed of on land and advocated sea dumping of any material which suffered from contamination from industries around ports. The PIANC report added that most dredging in ports is environmentally safe and does not warrant controlled dredging and special care disposal methods. The longterm solution was to control land-based industry which was putting the pollutants into the ports and channels. It was recognized that most attention should be given in areas where there was a high level of heavy metals such as mercury and cadmium and chlorinated hydrocarbons. Port authorities would have few options for their disposal and their dumping posed a difficult problem. However, PIANC believes that the technology is available to remove the dredged materials from coastal regions in "an efficient and environmentally acceptable manner" using techniques such as disposal between underwater dams, in pits by capping and by development of artificial islands.

EPA Stops Sludge Dumping in New York Bight On 1 April 1985 the US Environmental Protection Agency denied petitions to redesignate the 12 Mile Site in the New York Bight Apex for disposal of sewage sludge. This action will necessitate the use of other disposal options by nine sewage authorities in the northeastern US who had petitioned for continued use of the site. Previous litigation brought by the authorities had resulted in their use of the site under court order until EPA ruled on their petitions• EPA ordered closure of the 12 Mile Site citing that "... dumping has been a contributing factor to the overall degradation of the New York Bight'.' As evidence of this environmental degradation of the apex, EPA cited (1) elevated levels of bacteria which forced closure of the area around the site to shellfishing; (2) increased levels of toxic metals and organohalogens 426

waste driven. Surf blooms cannot be taken automatically as the beach manifestation of marine eutrophication. D E R E K EL L IS

in bottom sediments in areas near the site: (3) changes in relative abundance and diversity of marine species in areas affected by the dumping; (4) population shifts to pollution-tolerant species; and (5) disappearance of pollution-sensitive crustaceans. EPA designated a site 122 miles offshore for the disposal of sewage sludges on 4 May 1984. The Deepwater Municipal Sludge Dump Site (DMSDS--a part of the formerly-designated 106 Mile Site) was determined by the EPA to be environmentally preferable to the 12 Mile Site since (1) living resources at the offshore site are less abundant and less monetarily valuable, (2) the greater distance to shore will reduce the potential for any impacts on shorelines, beaches, and nearshore activities, and (3) the greater depths and dispersion at the offshore site will ensure that "... relatively low concentrations of contaminants and reduced environmental i m p a c t s . . ? will result from the sludge disposal. The sewage authorities and EPA have reached agreement on a gradual phase-out of the 12 Mile Site beginning in March 1986, with all sludge dumping activities to be transferred to the DMSDS by December 1987. All these authorities will require use of additional, larger ships or barges to transport their current volumes of sludge to the DMSDS.

Ocean Disposal Symposium The Sixth International Ocean Disposal Symposium will be held on 21-25 April 1986, in Pacific Grove, California. Supported by the International Maritime Organization (IMO), the World Bank, and the US National Oceanic and Atmospheric Administration, the Symposium is conducted to (1) provide a periodic forum for the exchange of ideas and information among investigators performing ocean disposal research, (2) enhance the scientific consideration of waste disposal in the marine environment, and (3) generate recommendations and guidelines for future studies of marine disposal practices. Topics that will be emphasized in the 1986 Symposium include: (1) disposal of persistent plastics and fish nets and the effects of these items on living resources and maritime transportation, (2) at-sea incineration, (3) waste disposal practices and marine pollution problems of island countries, and (4) progress and developments in International Conventions. Abstracts of 200-300 words are invited and should be submitted by 1 February 1986 to Professor Iver Duedall, Organizing Committee Chairman, Florida Institute of Technology, Department of Oceanography and Ocean Engineering, Melbourne, Florida 32901, USA.

Bathymetric Fishing Maps The National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), has been