Paul Read

Management of environmental impacts of marine aquaculture in Europe

Abstract There are large differences between countries in the rate of growth and development of marine aquaculture, and also in the sophistication and complexity of its regulation, control and monitoring procedures. The potentially deleterious impacts of aquaculture are widely documented in the literature [J. Appl. Ichthyol. 17 (2001) 181; Fernandes, T.F., Eleftheriou, A., Ackefors, H., Eleftheriou, M., Ervik, A., Sanchez-Mata, A., Scanlon, T., White, P., Cochrane, S., Pearson, T.H., Miller, K.L., Read, P.A., 2002. The Management of the Environmental Impacts of Aquaculture. Scottish Executive, Aberdeen, UK, 88 pp.]. It is widely accepted that such impacts would be minimised or negated by the adoption of appropriate culturing procedures and environmental safeguards including regulatory, control and monitoring procedures [Nature Conservancy Council (NCC), 1989. Fish Farming and the Safeguard of the Natural Marine Environment of Scotland. Nature Conservancy Council, Peterborough, England, 136 pp.; Codling, I.D., Doughty, R., Henderson, A., Naismith, I., 1995. Strategies for Monitoring Sediments and Fauna Around Cage Fish Farms. Marlow, UK: Scotland and Northern Ireland Forum for Environmental Research (SNIFFER), Report No. SR 4018, 78 pp.; GESAMP (IMO/FAO/UNESCO-IOC/WMO/WHO/IAEA/UN/UNEP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection), 1996. Monitoring the ecological effects of coastal aquaculture wastes. Scientific aspects of marine environmental protection. Rome, Italy: Rep. Stud. GESAMP No. 57, 38 pp.; GESAMP (IMO/FAO/UNESCO-IOC/WMO/WHO/IAEA/UN/UNEP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection), 2001. Planning and management for sustainable coastal aquaculture development. Rome, Italy: Rep. Stud. GESAMP No. 68, 90 pp.]. It is essential that such safeguards are formulated from the best available science and technology and from the best available experience and expertise. In this context, there are lessons to be learned from the strategy and regulatory framework for the regulation, control and monitoring of environmental impacts of marine aquaculture within the European Union (EU). This paper identifies some of the main issues relevant to the management of environmental impacts of marine aquaculture; reviews EU and international policy and regulations in this context and provides one example of a strategy for the management of the environmental impacts of marine aquaculture by reference to the marine aquaculture industry in Scotland. In conclusion, it examines a number of current, key environmental concerns pertaining to the impact and regulation of marine aquaculture, which whilst being the subject of divergent views, are pivotal to the development of the industry. Recommendations for systems, procedures and research to address these concerns are identified. The paper is primarily concerned with marine finfish culture, although brief reference is made to shellfish culture. The control of diseases of finfish and shellfish is outside the scope of the paper, although brief consideration is given to current concerns relating to sea lice (predominantly Lepeophtheirus salmonis) infestations in salmonids.

Effects of macroalgal mats on intertidal sandflats: an experimental study.

The growth of green macroalgal mats is becoming increasingly common in many marine intertidal habitats. While the ecological effects of such growth has previously been experimentally investigated on mudflats, such experiments have rarely been performed on intertidal sandflats. This study investigated the ecological effects of macroalgal cover on a moderately exposed intertidal sandflat, Drum Sands, Firth of Forth, Scotland. Artificially implanted Enteromorpha prolifera (Müller) caused marked changes in the macrobenthos, together with significant changes in all the measured sediment variables. After 6 weeks, the weed significantly increased the macrofaunal diversity. The numbers of Pygospio elegans (Claparède) were significantly reduced under weed mats, while those of Capitella capitata (Fabricius), oligochaetes and gammarids increased. Percent water, organics and silt/clay contents, medium phi and sorting coefficient significantly increased in the sediments under weed mats which also became significantly more reduced between 1 and 8 cm depth. After 20 weeks, a macrofaunal community numerically dominated by C. capitata, with a significantly reduced diversity, was present under weed mats, while sediment variables were no longer significantly different from controls. The negative effect of E. prolifera on P. elegans was mainly due to larval filtering, suggesting that weed is likely to have detrimental effects on population maintenance of most species which rely on planktonic larval recruitment. These results are broadly similar to those obtained from algal manipulation experiments performed in much more sheltered, muddier environments. We suggest that a predictable deterioration in environmental quality results from the growth of macroalgal mats in soft-bottom habitats. However, the longer term effects of such algal growth are less predictable and depend upon the spatial distributions of the most abundant infaunal species and the spatial heterogeneity of weed mat establishment.

The nutrient assimilative capacity of maerl as a substrate in constructed wetland systems for waste treatment

This study evaluated the performance of maerl (calcified seaweed) as a substrate for artificial wetland waste treatment systems. Pilot scale artificial wetlands were set up in the laboratory; three planted with Phragmites australis and three unplanted, and fed with a synthetic sewage solution. The effluent from the tanks was monitored over a period of 9 weeks for chemical oxygen demand, total nitrogen, total phosphorus, ammonium-N, total oxidised nitrogen, soluble reactive phosphorus, dissolved oxygen, pH and temperature. The data were analysed using repeated measures ANOVA to look for significant differences between treatments, and within treatments, over time. A batch incubation experiment was also carried out to ascertain the maximum adsorption capacity of maerl for phosphorus. Results obtained were compared with those in the literature for other substrates. Variability within and between treatments was high, but it was found that maerl effectively removed total phosphorus (98%). Nitrogen removal was less effective, with the tanks producing ammonium-N. The low nitrogen removal shown in the tanks was a factor of the short duration of the experiment; but ammonification did decrease in the planted tanks over time. Performance at removing nitrogen was normal when compared with figures in the literature, but phosphorus removal by maerl was considerably higher than gravel bed wetlands, and comparable with the very best figures given for artificial wetlands based on novel substrates such as shales and slags. This trial showed that maerl has great potential as a constructed wetland substrate, due to its high phosphorus-adsorbing capacity.

Toxicity of sewage sludge to marine organisms: A review

Abstract Results of laboratory, mesocosm, and field studies on the toxicity of sewage sludge to marine organisms are summarised. The 24 taxa tested included adults, juveniles, larvae, embryos, sperm and algal zoospores. These toxicity studies are discussed in relation to sewage sludge dispersion and dilution, and observed effects in the field. The 96 h LC50 averages for sewage sludges ranged from 20% wet volume of sludge in seawater for polychaetes (Malacoceros fuliginosus and Scolelepis squamata) to 0·0003% for shrimp larvae (Crangon crangon). One third of the tests reviewed found minimum toxic concentrations of less than or equal to 0·1%. The cause of toxicity cannot be attributed to any single component, but contaminants from industrial wastes can be a significant factor. There is no indication of any build up of toxicity in the studies. Components of sewage can be utilised by phytoplankton, zooplankton, detrivorous invertebrates, and ingested by fish. Bioaccumulation of contaminants can occur through the diet. In general, dilution after dumping at sea is less than 0·1% (1 in 1000) within 30 min and 0·01% within 1 h. Based on these figures, acute toxicity is unlikely to occur at ecologically significant or detectable levels at dump sites. However, at some dump sites chronic effects due to organic enrichment are evident as changes in the species richness, relative abundance, and biomass of macroinvertebrate species.