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DENSITY-DEPENDENT IMPACTS OF BIOIRRIGATION BY THE BURROWING SHRIMP UPOGEBIA PUGETTENSIS ON BENTHIC FLUXES AND POREWATER SOLUTE DISTRIBUTIONS IN PACIFIC NORTHWEST ESTUARIES
Citation:
D'Andrea, A. F. DENSITY-DEPENDENT IMPACTS OF BIOIRRIGATION BY THE BURROWING SHRIMP UPOGEBIA PUGETTENSIS ON BENTHIC FLUXES AND POREWATER SOLUTE DISTRIBUTIONS IN PACIFIC NORTHWEST ESTUARIES. Presented at 2002 AGU/ASLO Ocean Sciences Meeting, Honolulu, HI, February 11-15, 2002.
Description:
Burrowing thalassinid shrimp are major ecosystem engineering species of Pacific estuaries and can structure the physical, chemical, and biotic properties of sediments. Feeding and burrow irrigation by benthic organisms can increase the remineralization rates of organic material (OM) and the interfacial solute fluxes. This study utilized a combination of benthic chambers and porewater peepers to quantify the role of Upogebia pugettensis population density on benthic fluxes and porewater solute distributions in Yaquina Bay, Oregon.
Sediment oxygen uptake was 3-7 times greater in the presence of shrimp and increased linearly with shrimp burrow density (R2 = 0.8). Similarly, the Dissolved Inorganic Nitrogen (DIN = ammonium and nitrate) flux from sediments to overlying water increased with burrow density (R2 = 0.66). At mid and high shrimp densities (55 and 130 burrows 0.25 m-2, respectively), nitrate became proportionally more important to DIN efflux from the sediments indicating a potential density-dependent increase in nitrification. U. pugettensis also affected porewater solute profiles to ~ 50 cm. The inventory of PO4 and NH4 was inversely related to burrow density with the greatest impact seen in PO4 where integrated concentrations were 8 times greater in "no shrimp" habitat compared to areas with high shrimp densities. Ammonium and phosphate porewater profiles were most affected by mid- and high densities of shrimp burrows where there was lower solute concentrations in the top 30 cm of the sediment column, presumably due to bioirrigation. In contrast, the solute profiles in the "low density" (20 burrows 0.25 m-2) and "no shrimp" areas were dominated primarily by diffusive transport.
Thus, populations of U. pugettensis have a significant impact on OM and nutrient cycling in Yaquina Bay, which implies an important role for burrowing shrimp in the biogeochemistry of Pacific Northwest estuaries.