Effects of commercial clam aquaculture on biogeochemical cycling in shallow coastal ecosystems

Authors

Annie E. Murphy, Virginia Institute of Marine Science
Iris C. Anderson, Virginia Institute of Marine ScienceFollow
Mark W. Luckenbach, Virginia Institute of Marine ScienceFollow

Document Type

Presentation

Department/Program

Virginia Institute of Marine Science

VIMS Department/Program

Institute History (VIMS)

Publication Date

10-9-2015

Sponsorship/Conference/Institution

VIMS 75th Anniversary Alumni Research Symposium

Location

Virginia Institute of Marine Science, Gloucester Point, VA

Abstract

The bivalve aquaculture industry is expanding worldwide; sustainability requires improved understanding of its interactions with the environment. As suspension feeders, bivalves, such as clams, reduce primary production through feeding, and thus dampen eutrophication. Additionally, enhanced rates of denitrification, the microbial removal of reactive nitrogen, have been reported in bivalve sediments due to increased organic matter supply through biodeposition; another potential, yet indirect, control on eutrophication. Simultaneously, bivalves can influence local ‘bottom-up’ effects on production by enhancing nutrient regeneration through excretion and microbial mineralization of biodeposits. At clam aquaculture sediments, respiration and nutrient regeneration rates were significantly higher compared to uncultivated sediments. The enhanced nutrient recycling facilitated by clam aquaculture directly fueled macroalgal production, which proliferate on the shallow predator-exclusion nets commonly used by US aquaculturists. The effect of clams on denitrification and dissimilatory nitrate reduction to ammonium (DNRA), microbial processes that compete for nitrate, was site and season dependent; strongly influenced by nitrate concentrations relative to organic carbon availability. DNRA was favored over denitrification in environments with low nitrate (i.e. Cherrystone Inlet, VA) while denitrification increased above DNRA in high nitrate conditions (i.e. low salinity sites in Sacca di Goro, Italy). As a bioextractive practice, bivalve aquaculture is a net sink for nitrogen via harvest, however, depending on the food source (e.g. external or internal), bivalves may increase nitrogen and subsequently production on a local scale. These results highlight the need to assess both nitrogen removal and regeneration pathways associated with bivalve aquaculture to determine the overall effect on eutrophication.

Keywords

Poster, VIMS 75th Anniversary, Institute History, Alumni, Bivalves, Aquaculture

Recommended Citation

Murphy, Annie E.; Anderson, Iris C.; and Luckenbach, Mark W.. "Effects of commercial clam aquaculture on biogeochemical cycling in shallow coastal ecosystems". 10-9-2015. VIMS 75th Anniversary Alumni Research Symposium.