Pelagic-benthic coupling in the Bay of Fundy

Bivalve reefs are important in pelagic-benthic coupling and, in order to assess these linkages quantitatively, it is necessary to obtain accurate maps of reef biomass and production. Presented here is a preliminary attempt to use modern surficial geological techniques, including sidescan sonar and a high resolution seismic reflection system to map the distribution of bivalve reefs in the Bay of Fundy. Acoustic techniques were groundtruthed with a 0.5-m(2) video grab. The grab jaws could be hydaulically closed from the deploying vessel on the basis of a video view of the sediment from a camera focused between the grab jaws. Sampling was limited to the upper Bay of Fundy where five geological provinces were recognized. Preliminary results show that horse mussels are limited to the harder, more stable sedimentary provinces (gravel/cobble and mottled gravel), but also to an intermediate province: sand with bioherms. The latter are raised features formed by the horse mussels on megarippled sand which are long and thin, and flow-parallel structures covered with epifauna. Although positive, the present data are insufficient to conclude whether acoustic methods can significantly improve on conventional benthic grab sampling methods to map benthic production.