Evaluation of the impacts and sustainability of aquaculture activities
In the context of progressive impoverishment of natural fish stocks and world-wide increasing demand for fish-associated proteins the farming of fish, shellfish and aquatic plants is among the fastest-growing segments of the food economy. In the last 40 years aquaculture has grown at an average rate of 8% per year, with an annual production of about 55*106 tons, about the 46% of all the fish consumed by humans. Extensive or semi intensive fish production is carried out mainly in lakes and shallow coastal lagoons, while intensive farming in both artificial or seminatural closed systems (e.g. pond culture) or floating cages. Bivalve farming (oysters, mussels and clams) occurs mostly in coastal areas (i.e. coastal bays and lagoons) as these ecosystems provide ease of access and exhibit high rates of primary production which sustain both high densities and rapid growth rates of molluscs. In Italy intensive and extensive land based systems are well established, while fish farms based on floating cages are spreading in coastal areas. Most of the land-based fish farms are flow-through systems (trout farming) in mountain regions or in coastal areas where the farming of high value brackish or marine species (mostly seabass, seabream and eel) take place. Extensive lagoon farming is also a traditional activity in Italy that has large areas of brackish water (called "valli"), exploited for the production of mullet, eel, seabass and seabream. Particularly developed is the cultivation of bivalve filter feeders: the coastal lagoons of the Po River Delta sustain the largest European production of the exotic Manila clam (Ruditapes philippinarum) and are one of the most important production sites of the Mediterranean mussel (Mitylus galloprovincialis).
Although this activity provides a number of benefits (food production, job creation, improvement of rural economy, etc.) its rapid development has also several environmental concerns: land or coastal areas reclamation, higher density of aquaculture installations and farmed individuals, greater use of feed resources produced outside of the immediate culture area, environmental pollution. Carnivorous fish farming activities could have a strong negative feedback on natural fish populations as a consequence of the enormous need of natural fish stocks to be converted in fish feed. Additionally land-based fish farms need a huge water demand (hundreds of litres per second), oxygen supply, food, antibiotics and electricity to sustain cultivated biomass. The enormous mass of fish stocked (up to 30/40 kg m-3) determines a rapid consumption of dissolved O2 and a considerable increase of dissolved nitrogenous compounds (mostly NH4+) due to direct fish excretion. There are several evidences of the deterioration of aquatic environments due to high loads of organic matter and nutrients exported from the plant by outflowing water as part of the not ingested food, together with fish faeces and dissolved excretes. Environmental impacts from bivalve aquaculture are generally considered less severe compared to fish farming. Filter feeders in fact do not require external inputs of feed as they harvest particulate suspended solids directly from the water column. Because of the intense filtration and biodeposition bivalve filter feeders are being proposed as a tool to control seston concentrations and to sequester nutrients which would be removed from the system when the shellfish are harvested, buried in the sediment or lost through denitrification, promoting water purification. However, bivalve farming is increasingly recognised to strongly modify nutrient dynamics and the functioning of shallow coastal ecosystems as filtration, coupled to biodeposition of faeces and pseudofaeces creates “hot spots” of organic matter enrichment in the same way as sedimentation of feeds and faeces do below fish cages.
The Laboratory of Aquatic Ecology has a 15 years old tradition in the study of the environmental effects of both molluscs and fish aquaculture. The effects of suspended mussel (Mytilus galloprovincialis) and infaunal clam cultivation (Ruditapes philippinarum) on carbon, nitrogen and phosphorus cycles, along with interaction with primary producers growth and trophic status were assessed in the Sacca di Goro (Italy) lagoon. Net daily balances of dissolved and particulate nutrients were estimated in land based flow-through (trout, seabream and seabass) and suspended cages fish farms (seabream and seabass) and the potential impact on the environments that receive effluents was analyzed. N removal efficiency in phytotreatment ponds receiving wastewaters from land-based fish farms were also studied analyzing the relative importance of bacterial denitrification and macroalgal uptake for overall N removal. Simple guidelines for optimal management strategies of phytotreatment ponds were also evaluated.
The Laboratory of Aquatic Ecology has a 15 years old tradition in the study of the environmental effects of both molluscs and fish aquaculture. The effects of suspended mussel (Mytilus galloprovincialis) and infaunal clam cultivation (Ruditapes philippinarum) on carbon, nitrogen and phosphorus cycles, along with interaction with primary producers growth and trophic status were assessed in the Sacca di Goro (Italy) lagoon. Net daily balances of dissolved and particulate nutrients were estimated in land based flow-through (trout, seabream and seabass) and suspended cages fish farms (seabream and seabass) and the potential impact on the environments that receive effluents was analyzed. N removal efficiency in phytotreatment ponds receiving wastewaters from land-based fish farms were also studied analyzing the relative importance of bacterial denitrification and macroalgal uptake for overall N removal. Simple guidelines for optimal management strategies of phytotreatment ponds were also evaluated.
References:
Nizzoli D., Welsh DT., Viaroli P. 2011. Seasonal nitrogen and phosphorus dynamics during benthic clam and suspended mussel cultivation Marine Pollution Bulletin 62, 1276–1287.
De Gaetano P., Vassallo P, Bartoli M., Nizzoli D., Doglioli A., Magaldi MG., Fabiano M. 2011. Impact of new measured Mediterranean mineralization rates on the fate of simulated aquaculture wastes. Aquaculture Research. 2011, 42: 1359-1370.
Bartoli M., Vezzulli L., Nizzoli D., Azzoni R., Porrello S., Moreno M., Fabiano M. Viaroli, P. 2009. Short-term effect of oxic to anoxic transition on benthic microbial activity and solute fluxes in organic-rich phytotreatment ponds. Hydrobiologia 629(1), 123-136.
Nizzoli D., Bartoli M., Viaroli P. 2007. Oxygen and ammonium dynamics during a farming cycle of the bivalve Tapes philippinarum. Hydrobiologia 587: 25-36.
Nizzoli D, Bartoli M., Viaroli P. 2006. Nitrogen and phosphorous budgets during a farming cycle of the manila clam Ruditapes philippinarum: a full scale experiment. Aquaculture. 261:98-108
Vezzulli L., Bartoli M., Nizzoli D., Naldi M., Fanciulli G., Viaroli P., Fabiano M. 2006 A simple tool to help decision making in infrastructure planning and management of phytotreatment ponds for the treatment of nitrogen-rich water. Water SA Vol. 32 No. 4 Disponibile On-Line http://www.wrc.org.za
Bartoli M., Nizzoli D., Longhi D., Laini A., Viaroli P. 2007. Impact of a trout farm on the water quality of an Apennine creek from daily budgets of nutrients. Chemistry and Ecology 23(1): 1-11.
Bartoli M., Nizzoli D., Naldi M., Vezzulli L., Porrello S., Lenzi M., Viaroli P. 2005. Inorganic nitrogen control in wastewater treatment ponds from a fish farm (Orbetello, Italy): Denitrification versus Ulva uptake. Marine Pollution Bulletin 50:1386-1397.
Bartoli M., Nizzoli D., Vezzulli L., Naldi M., Fanciulli G., Viaroli P., Fabiano M. 2005. Dissolved oxygen and nutrient budgets in a phytotreatment pond colonised by Ulva spp. Hydrobiologia 550: 199-209.
Nizzoli D., Welsh D.T., Bartoli M., Viaroli P. 2005. Impacts of mussel (Mytilus galloprovincialis) farming on oxygen consumption and nutrient recycling in a eutrophic coastal lagoon. Hydrobiologia 550: 183-198.
Bartoli M., Naldi M., Nizzoli D., Roubaix V., Viaroli P. 2003. Influence of clam farming on macroalgal growth: a mesocom experiment. Chemistry and Ecology 19: 147-160
Viaroli P., Bartoli M., Giordani G., Azzoni R., Nizzoli D. 2003. Short term changes of benthic fluxes during clam harvesting in a coastal lagoon (Sacca di Goro, Po River Delta). Chemistry and Ecology 19: 1-18
Melià P., Nizzoli D., Bartoli M., Naldi M., Gatto M., Viaroli P. 2003. Assessing the potential impact of clam rearing in dystrophic lagoons: an integrated oxygen balance. Chemistry and Ecology 19: 126-146.
Bartoli M., Nizzoli D., Viaroli P., Turolla E., 2001. Impact of a Tapes philippinarum farming on nutrient dynamics and benthic respiration in the Sacca di Goro. Hydrobiologia 455: 203-212.
Nizzoli D., Welsh DT., Viaroli P. 2011. Seasonal nitrogen and phosphorus dynamics during benthic clam and suspended mussel cultivation Marine Pollution Bulletin 62, 1276–1287.
De Gaetano P., Vassallo P, Bartoli M., Nizzoli D., Doglioli A., Magaldi MG., Fabiano M. 2011. Impact of new measured Mediterranean mineralization rates on the fate of simulated aquaculture wastes. Aquaculture Research. 2011, 42: 1359-1370.
Bartoli M., Vezzulli L., Nizzoli D., Azzoni R., Porrello S., Moreno M., Fabiano M. Viaroli, P. 2009. Short-term effect of oxic to anoxic transition on benthic microbial activity and solute fluxes in organic-rich phytotreatment ponds. Hydrobiologia 629(1), 123-136.
Nizzoli D., Bartoli M., Viaroli P. 2007. Oxygen and ammonium dynamics during a farming cycle of the bivalve Tapes philippinarum. Hydrobiologia 587: 25-36.
Nizzoli D, Bartoli M., Viaroli P. 2006. Nitrogen and phosphorous budgets during a farming cycle of the manila clam Ruditapes philippinarum: a full scale experiment. Aquaculture. 261:98-108
Vezzulli L., Bartoli M., Nizzoli D., Naldi M., Fanciulli G., Viaroli P., Fabiano M. 2006 A simple tool to help decision making in infrastructure planning and management of phytotreatment ponds for the treatment of nitrogen-rich water. Water SA Vol. 32 No. 4 Disponibile On-Line http://www.wrc.org.za
Bartoli M., Nizzoli D., Longhi D., Laini A., Viaroli P. 2007. Impact of a trout farm on the water quality of an Apennine creek from daily budgets of nutrients. Chemistry and Ecology 23(1): 1-11.
Bartoli M., Nizzoli D., Naldi M., Vezzulli L., Porrello S., Lenzi M., Viaroli P. 2005. Inorganic nitrogen control in wastewater treatment ponds from a fish farm (Orbetello, Italy): Denitrification versus Ulva uptake. Marine Pollution Bulletin 50:1386-1397.
Bartoli M., Nizzoli D., Vezzulli L., Naldi M., Fanciulli G., Viaroli P., Fabiano M. 2005. Dissolved oxygen and nutrient budgets in a phytotreatment pond colonised by Ulva spp. Hydrobiologia 550: 199-209.
Nizzoli D., Welsh D.T., Bartoli M., Viaroli P. 2005. Impacts of mussel (Mytilus galloprovincialis) farming on oxygen consumption and nutrient recycling in a eutrophic coastal lagoon. Hydrobiologia 550: 183-198.
Bartoli M., Naldi M., Nizzoli D., Roubaix V., Viaroli P. 2003. Influence of clam farming on macroalgal growth: a mesocom experiment. Chemistry and Ecology 19: 147-160
Viaroli P., Bartoli M., Giordani G., Azzoni R., Nizzoli D. 2003. Short term changes of benthic fluxes during clam harvesting in a coastal lagoon (Sacca di Goro, Po River Delta). Chemistry and Ecology 19: 1-18
Melià P., Nizzoli D., Bartoli M., Naldi M., Gatto M., Viaroli P. 2003. Assessing the potential impact of clam rearing in dystrophic lagoons: an integrated oxygen balance. Chemistry and Ecology 19: 126-146.
Bartoli M., Nizzoli D., Viaroli P., Turolla E., 2001. Impact of a Tapes philippinarum farming on nutrient dynamics and benthic respiration in the Sacca di Goro. Hydrobiologia 455: 203-212.