Toxicity of petroleum hydrocarbons to Brachyuran crabs: a review of deleterious effects of oil-related xenobiotics on life stages

Petroleum hydrocarbons (PH) toxicity and bioaccumulation in aquatic organisms have been investigated for almost 50 years. Continuous oil spillages necessitate a further understanding of the toxicological effects of PH on brachyuran crabs. Crabs can be exposed to PH through various routes such as the water column, sediment and diet. Numerous investigations have been dedicated to evaluating PH toxicity on different life stages of crab species, but the majority of them have focused on the blue crab Callinectes sapidus as it represents an edible and favourable seafood commodity for human consumption. The objective of the review is to critically assess studies related to PH toxicity on different life stages of 41 crab species representing 13 families across the world. Several physiological, biochemical and genetic endpoints of marine crabs were evaluated in addition to the sublethal effects of PH on crab metabolism, behaviour, moulting, growth and survival. A concise summary of PH deleterious effects on different taxonomic species of marine crabs is discussed and provides evidence that crabs can be used as indicator organisms of biomarker significance for marine pollution. Overall, larval stages appeared to be the most sensitive to the deleterious effects of PH compared with juveniles and adults. However, adult stages have received more research attention than other life stages, followed by larval stages, and juvenile stages are the least investigated stages with respect to PH toxicity. Finally, hepatopancreas and gills were the organs where greatest accumulation of PH was recorded.

Pelagic Food Web Structure in Adirondack Mountain, USA, Lakes of Varying Acidity

Pelagic food web models were constructed for 50 softwater lakes of varying acidity (pH 4.17–7.32) in the Adirondack Mountains, and relationships between food web parameters and several abiotic variables (pH, monomeric Al, dissolved organic carbon (DOC), zmax, and area) were quantified. With declining pH, pelagic food web complexity was reduced, as the number of species, links, links per species, predator generalization, and prey vulnerability all declined. The declines were less pronounced in lakes having high DOC levels. Some web parameters, including the predator/prey ratio, the portion of basal, intermediate and top species, and species redundancy, did not decline with pH but were more variable among the acid lakes. Those trends are consistent with the view that at low pH, toxicity becomes the major factor controlling community structure.