Bottom-up Effects of Clam Aquaculture

Collaborators:  Iris Anderson (VIMS) and Mark Luckenbach (VIMS)

High densities of bivalves found in aquaculture can exert ‘top-down’ control on primary production through feeding while simultaneously influencing local ‘bottom-up’ effects on production by enhancing nutrient recycling. Thus bivalves may decrease or increase localized eutrophication, depending on environmental conditions and specific culture practices.

benthicpelagiccoupling

In this study we used in situ incubations to investigate nutrient ycling and metabolism at commercial clam aquaculture sites on the eastern shore, VA.  Nutrients were over 100 times higher at the clam beds compared to the uncultivated control sites.  Macroalgae, which proliferate on the predator exclusion nets used by the industry, take up a considerable portion of the nutrients sourced from the clam sediments.  The clam beds supply nitrogen in excess of macroalgal demand, suggesting N recycling in the benthos is sufficient to support macroalgal production. As a bio-extractive practice, clam aquaculture is a net sink for nutrients. However, our data suggest clam cultivation may influence eutrophication locally by facilitating increased macroalgal production due to increased benthic nutrient recycling. Given the high capacity for macroalgae to temporarily sequester nutrients released from the clam beds, macroalgal harvest may be effective in removing unwanted nutrients from the ecosystem.

Read more:

A.E. Murphy, I.C. Anderson, and M.W. Luckenbach. 2015. Enhanced nutrient regeneration at commercial hard clam (Mercenaria mercenaria) beds and the role of macroalgae. Marine Ecology Progress Series. DOI 10.3354/meps11301