Population dynamics and nutrition of Corophium volutator (Pallas) in the Cumberland Basin (Bay of Fundy)

Abstract

Corophium volutator (Pallas), a tube-dwelling amphipod, is the dominant macro-invertebrate in intertidal mudflats of the Bay of Fundy. Abundance and biomass were followed at two sites from May to October. In spring, the population consisted primarily of a small overwintering generation. The release of young resulted in peak densities of up to 15000 individuals·m −2 in late June/early July. Numbers and biomass then declined drastically, in part because of heavy predation by migrant shorebirds. Their departure allowed a partial recovery of the C. volutator population. C. volutator biomass or density showed either no or weak correlation with organic, protein or chlorophyll content of the sediment. Organic particles amounted to <0.1% of mud dry wt, suggesting that over 90% of the organic content of mud is in solution, or concentrated at particle/water interfaces. Both Spartina and diatoms contributed at most 1% to the gut content of Corophium. Bacterial numbers declined from anterior to posterior part of the gut by ≈60%. The maximum contribution of identifiable food items to the nutrition of Corophium has been estimated at 46.5% ( Spartina, 3.8%; diatoms, 11.4%; bacteria, 31.3%); the average is below 4%. Immunofluorescence and a complement fixation assay were used to identify gut contents further but neither was completely satisfactory. There is some indication, however, that in addition to organic matter associated with mud, seaweed-derived material may play a minor role in the nutrition of Corophium.