Acronym NA
Category
Aquaculture
Title Kunnskapsstatus om næringssalttilførsler og eutrofiering om havbruksvirksomhet - Knowledge status about nutrient inputs and eutrophication about aquaculture activities Programme National Programme
Instrument (FP6)
Contact Type (FP7)
Strand (Interreg)
NA
Theme (FP7)
Activity Area (FP6)
Regional Area (Interreg)
Action (COST)
NA
Specific Programme (FP7)
NA
Funding source National Coordinator Kjell Maroni Coordinator email kjell.maroni@fhf.no
Coordinator institution
FHF - Norwegian Seafood Research Fund (Norway)
Institutions involved
NA
Start year 2006 End year 2006 Funding (€) € NA Website https://www.fhf.no/prosjekter/prosjektbasen/542014/ Summary The worldwide fast growing aquaculture industry has caused a growing attention and concern on the more societal aspects of the industry, among them the environmental effects of aquaculture on coastal ecosystems. This has spawned new legislation, but also research activity to support legislation, management practices, and actions taken by the industry to reduce environmental impact. As a broad fundamental perspective for management, an emerging view is that fish farms should be managed as a part of the marine ecosystem according to a principle of ―Ecosystem-based Approach to Aquaculture. There is so far no general concept of understanding and sufficient knowledge as to how potential harmful impact on open water ecosystems can be assessed and managed. Benthic impacts are better understood and managed, but there is still a general lack of standardisation and agreement on monitoring practices. The main objective of the present report is to review and evaluate the state of knowledge from the recent accumulating international literature on environmental impact of aquaculture caused by nutrient emission to coastal waters. Individual fish release nutrients as dissolved inorganic nutrients through excretion (NH4 and PO4), particulate organic nutrients (PON and POP) through defecation, and dissolved organic nutrients (DON and DOP) through resuspension from the particulate fractions. On the scale of a fish farm, there will additionally be a direct loss of Feed-N and Feed-P (uneaten feed). These different waste components will affect different parts of the marine ecosystem; feed losses and the larger faeces particles will sink and affect sediments and benthic communities whereas dissolved inorganic nutrients, dissolved organic nutrients, and small faeces particles affect the pelagic communities and state and quality of euphotic waters. The release rate of nutrient wastes from intensive aquaculture can be estimated by mass balance based on statistical information on feed use and fish production, combined with information on feed losses, contents of N and P in the feed and the fish, and assimilation efficiencies of the dominant N and P components of the feed. Such estimates are particularly robust for N when feed losses are low, feed production in the system is low, and the statistical information is adequate for the purpose. Use of P-components from higher plants in the feed introduces a major uncertainty in the assimilation efficiency of P in the fish, making estimates more uncertain. An alternative approach for estimating waste emission rates from aquaculture, although not that robust, is to estimate waste losses by dynamic metabolically based modelling of fish feeding, growth, and metabolism. An estimation of waste emission by mass balance made for salmon cage aquaculture with an overall feed conversion efficiency of 1.16 kg dry feed per kg fish produced shows that slightly less than 2/3 of N and P of the feed is released as wastes. NH4 is the main waste component of N whereas particulate P is the main component of P. Feed-N, Feed-P, DON, and DOP are all minor waste components of salmon aquaculture. The estimations agree generally well with measured published values. N and P are not toxins, but biogenic elements which are potential harmful in the marine environment only if their supply exceeds the assimilation capacity of the ecosystem. All ecosystems have an inherent capacity of persistence, and smaller changes in nutrient supply are mitigated through adaptive responses of the communities. The scientific understanding of these processes and impacts in benthic ecosystems is well developed, but this is not the case for pelagic ecosystems. We propose that the assimilation capacity of nutrients of the water column ecosystem is mediated by two main mechanisms: 1) Nutrient uptake by phytoplankton and further transfer to higher trophic levels and 2) Dilution of nutrients and organisms mediated by hydrodynamics at production sites and their surrounding, downstream water masses. Both mechanisms will be important in a general scientific scheme, which can support management of the pelagic system. Hydrodynamics is most important; high energy is paramount for large intensive fish farms. Management of pelagic impacts require monitoring on a regional scale, because the potential environmental effects will normally become expressed on a regional scale of the fish farm. Satellite imaging and 3D modelling are suitable means for monitoring and managing these effects, in addition to more classical measurements. Particulate nutrients affect the sediments and benthic ecosystems below fish farms and in the immediate surrounding area. It is quite well understood how these accumulations of nutrient wastes distribute in sediments as a consequence of fish production, bottom topography, water current velocity and water depth. Severe accumulations can cause major changes in the structure and function of benthic ecosystems locally, i.e., normally resulting in decreasing diversity of the benthic fauna and flora. The common result is highly reduced conditions due to sulphide accumulation with a shift in decomposition of organic matter from fauna mediated to microbial processes. Oxic microbial processes like nitrification are inhibited, and this may also limit denitrification due to low nitrate concentration and sulphide toxicity. The result is high ammonium and phosphate release from fish farm sediments. There are a number of methods and models to classify and assess trophic state of sediments, which can support a scientifically based monitoring and management of benthic impacts from aquaculture in coastal sites. There are an increasing number of papers published on environmental interactions of aquaculture made available in ISI Web of Science databases over the last decades. The fraction of papers treating environmental aspects of aquaculture was 16% of the total numbers of aquaculture papers for the period 1990-1999 and 20% for 2000-2006. The corresponding fraction combining aquaculture and eutrophication for 1990-1999 and 2000-2006 were 1.4 (29 papers) and 2.4% (92 papers), respectively, corresponding to about 10% of the environmental papers related to aquaculture. There are as expected far more contributions for the benthic impacts of aquaculture than for the pelagic, which still lacks a general scientific concept that can support identification and management. The report summarise more recent, important contributions for eutrophication and aquaculture in general and for benthic and pelagic impacts. Finally, the report recommends R&D actions to fill gaps of knowledge needed to meet requirements of future, international legislation.
Keywords
Fish;
Open sea aquaculture;
Cage aquaculture;
Pollution;
Environmental impact;
Marine Region
76
Not associated to marine areas
0
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