Miller, D. C. University of Delaware,

On the sandflat at Cape Henlopen, DE, submarine groundwater discharge creates persistent patches of lowered pore water salinity that are characterized by sharp vertical and lateral gradients. Seasonal coring for macrofauna confirmed the apparent relationship between low salinity patches and the infaunal dominant, the obligate deposit-feeding, spionid polychaete Marenzelleria viridis. Marenzelleria patches are dense assemblages (several thousand per square meter) and differ markedly from the nearby, more diverse, lower abundance benthic community. Size-frequency analysis of the worms suggests that the springtime recruitment of this species coincides with the seasonally greatest extent of low salinity patches. Nutrient analysis of lowered salinity pore waters reveals the enhanced nutrient signal of groundwater discharge. Elevated ammonium, however, suggests the occurrence of chemical transformations more analogous to estuarine interstitial waters than direct groundwater discharge. Increased sediment diatom productivity and consumption by the deposit-feeding macrofauna may be indirect means by which geochemistry drives local patch primary productivity, trophic relationships and community composition. While the ecological, biogeochemical and microbiological processes responsible are not resolved, it is clear that macrobenthic population dynamics and pore water nutrient chemistry at this and other seepage sites must be viewed in the context of groundwater flux.
Day: Thursday, Feb. 4
Time: 09:30 - 09:45am
Location: Hilton of Santa Fe
Code: SS30FR0930S