RESUMO
Although intensive marine fish farming is often assumed to be eco-friendly, the associated activity can lead to chronic exposure of marine organisms to potentially toxic discharges. Moreover, despite the increasing popularity of integrated multi-trophic aquaculture (IMTA), studies of the effects of fish farm effluents are almost non-existent. In the present study, the changes in the toxic potential of effluents from five land-based marine fish farms in NW Spain subjected for different lengths of time to a biodegradation procedure (for 0, 48, 120, and 240 h) were assessed in a battery of bioassays including organisms from different trophic levels (Vibrio fischeri, Isochrysis galbana, and Paracentrotus lividus). The results of the bioassays at the different times were then considered together with farm water flow in the Potential Ecotoxic Effects Probe (PEEP) index. Despite the high volumes of effluents discharged, the generally low toxicity of the effluents hinders assessment of potentially toxic effects. However, dose-response curves and statistical analysis demonstrated the existence of toxic effects during the first five days of the biodegradation procedure, especially immediately after sampling. The proposed modification of the PEEP index better reflects the changes in toxicity over time. Graphical abstract á .
Assuntos
Organismos Aquáticos/efeitos dos fármacos , Monitoramento Ambiental/métodos , Pesqueiros , Poluentes Químicos da Água/toxicidade , Aliivibrio fischeri/efeitos dos fármacos , Animais , Aquicultura , Bioensaio , Haptófitas/efeitos dos fármacos , Paracentrotus/efeitos dos fármacos , Espanha , Testes de Toxicidade/métodosRESUMO
Methane production from marine microalgae Isochrysis galbana was assessed before and after mechanical and chemical pretreatments. Mechanical pretreatment resulted in a 61.7% increase in soluble Chemical Oxygen Demand. Different hydrolysis conditions were evaluated by varying temperature - T, sulfuric acid concentration - AC and biomass suspension concentration (measured as particulate COD - CODp) using an experimental design. The most significant interaction occurred between AC and T and the hydrolysis condition that showed the best result in the anaerobic digestion step was the condition at 40°C with addition of 0.2% (v/v) acid for 16h (9.27LCH4/kgVS). The low methane yields were attributed to inhibitory sodium concentrations for anaerobic digestion. Eliminating inhibitory sodium in the anaerobic digestion by biomass prewashing, there was a 71.5% increase in methane yield for biomass after acid hydrolysis, demonstrating the need for pretreatment and reduction in sodium concentration in the anaerobic digestion.