Hammerschmidt, C. R., Dept. of Earth & Environmental, Dayton, OH, USA, chad.hammerschmidt@wright.edu
Fitzgerald, W. F., Dept. of Marine Sciences, University of Connecticut, Groton, CT, USA, william.fitzgerald@uconn.edu

SEDIMENT-WATER EXCHANGE OF METHYLMERCURY IN NEW YORK HARBOR DETERMINED FROM SHIPBOARD BENTHIC FLUX CHAMBERS

Benthic mobilization is an important pathway by which organisms are exposed to monomethylmercury (MMHg) produced in sediments. We have developed shipboard benthic flux chambers (SBFCs) to measure MMHg effluxes from intact sediment cores, and used this method at locations in NY Harbor under summer and winter conditions. Fluxes determined with the SBFCs were compared with diffusional effluxes estimated from gradients of dissolved MMHg in the same sediments (SBFC:diffusional flux ratio). SBFC:diffusional flux ratios ranged from 0.9 to 1.4 in August and 2.3-4.3 in February. SBFC:diffusional flux ratios were correlated positively with dissolved oxygen (DO) in bottom waters, suggesting that MMHg mobilization is largely diffusional when DO is less than about 80% saturation and enhanced at greater levels. This is consistent with the observed positive relationship between macrofauna abundance and DO. Thus, benthic MMHg mobilization fluxes, which are enhanced relative to diffusion when DO in bottom waters is near saturation, may be linked to increased abundance and/or activity of infauna that irrigate sediment. Improving oxygen conditions, therefore, could increase sediment-water effluxes of MMHg in NY Harbor and comparable coastal marine systems.

Poster presentation

Presentation is given by student: No
Session #:187
Date: 03-03-2008
Time: 17:30 - 19:30