THE USE OF BENTHIC INFAUNA TO PREDICT ESTUARINE DENITRIFICATION: ORGANISMAL AND SYSTEM SCALE ANALYSIS

Numerous studies have documented the impacts benthic fauna can have on nitrogen cycling, but it is not clear how those impacts extend to impact nitrogen transformation at the ecosystem scale. This is particularly important in estuarine systems, given their role as critical transition zones impacting the movement of nitrogen from the terrestrial to the marine environment. To investigate the role of benthic macrofauna on benthic N cycling, we combine estuarine denitrification data with large-scale benthic fauna and water quality databases to shed light on the relationships between the benthic community and estuarine nitrogen removal. This analysis showed a general positive trend between diversity/abundance and denitrification, but this relationship was not significant. However, reactive transport simulations at the scale of macroinfauna show significant relationships between sediment denitrification and bioirrigation activity. We therefore related N₂ production to the abundance of benthic macrofauna using a literature compilation of organism-scale denitrification studies. Combined with information on the reactivity of the sediment and the availability of substrate, we use information on organism density to predict estuarine denitrification at the system scale, and compare it to system scale estimates.

This model provides reasonable estimates of nitrogen removal in 11 out of 12 estuaries studied, suggesting that one can constrain changes in estuarine nitrogen removal as a response to alterations in nutrient loading or abundance of benthic macrofauna.