Aquaculture farms are an integral part of the coastal marine ecosystem and associated food web dynamics. Bivalves grown on coastal farms filter feed ambient seston and in turn contribute biodeposits that are recycled back into the existing food web. Little is known about how the presence of these aquaculture farms alters the food web structure and trophic level interactions of coastal ecosystems. We hypothesized that the food web organization and energy flow of fouling benthic organisms (e.g., mussels, skeleton shrimp, amphipods, tunicates, small crabs, etc.) will differ on surfaces associated with suspended, bivalve farms that are protected by nets from diving ducks vs. those on other surfaces such as docks, pilings, or buoys away from farms. Food web structure and energy flow will be quantified by using stable isotope analysis (δ13C and δ15N) and biodiversity indices.
Preliminary investigation of sediments collected directly under the bivalve farm and from 90m to 900m away from the farm revealed dark anoxic ooze under the farm, unlike sediment collected away from the farm. However, a t-test revealed that there was no statistical difference in the δ13C or δ15N values of the sediment on farms or away from farm locations (p-value = 0.7553 & 0.9675, respectively). Mackerel are at least a full trophic level above zooplankton with more than 3.4 ‰ separation in δ15N and most likely have a different carbon source than zooplankton with about 2.0 ‰ separation in δ13C. In summer 2017 we will sample additional bivalve farms as well as locations away from the farms. This research will provide a beginning step to better understand how coastal food webs support bivalve aquaculture and what role farms have in structuring coastal food webs.