Dynamics and adaptive responses of invertebrates to suboxia in contaminated sediments of a stormwater infiltration basin

We examined the composition and adaptive responses of the aquatic fauna in the contaminated bed of a stormwater basin to understand how organisms could maintain permanent populations in such a harsh environment. Bed sediments had high concentrations of nutrients, total hydrocarbons, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and heavy metals. Oxidation of organic constituents led to almost permanent suboxic conditions that were interrupted by short oxic periods immediately after rainfall events. Only two species, the oligochaete T tubifex and the cyclopoid E. serrulatus were able to maintain permanent populations in this extreme environment. Both species preferred areas of the infiltration bed which were replenished with oxygenated inflow storm water. In the polluted biotope, when sufficient oxygen was available, T tubifex had increased both metabolic and ammonia excretion rates that could be due to a stimulated renewal of detoxification enzymes and/or metal-binding proteins. Moreover, this species exhibited several adaptations to survive temporary oxygen deprivation, including a marked reduction in metabolic rate, elevated ATP production, and an efficient anaerobic metabolism based on the coupled utilization of glycogen and aminoacids. It was also able to accumulate end-products during suboxic conditions and rapidly restore its energy stores during post-suboxic recovery.