U.S. Environmental Protection Agency
EPA Science Advisory Board
Background Information

Document NameEffect of hypoxia/anoxia on the supply and settlement of benthic invertebrate larvae.
Document AuthorPowers, S. P.
Harper, Jr., D.E.
Rabalais, N.N.
Short DescriptionPp 185-210 in N. N. Rabalais and R. E. Turner (eds.), Coastal Hypoxia: Consequences for Living Resources and Ecosystems. Coastal and Estuarine Studies 58, American Geophysical Union, Washington, D.C.
CategorySubgroup 1: Characterization of the Cause(s) of Hypoxia
Publication Year2001

Abstract: Recovery of benthic animals following large-scale disturbances is primarily a function of larval recruitment. Given the large number of recent studies that have demonstrated the potential importance of larval supply of meroplanktonic larvae is affted by such disturbances is critical in developing a complete understanding of the dynamics of benthic communities. During the summer of 1994 and 1995, we measured the flux of meroplanktonic larvae and holoplankton at three positions in the water column during both stratification and low oxygen events, and during periods when the water column was mixed. We found that benthic polychaete larvae were distributed throughout the water column and that this pattern did not appear to change in response to low oxygen. We found evidence, however, that at least one polychaete species, Parapriono pinnata, delayed settlement and remained in the water column until oxygen values returned to a level above 2.0 mg 1-1. Barnacle cyprid larvae and many holoplanktonic species were present in reduced densities below the pycnocline when oxygen concentrations were low. We intpreted the differences in response to plankton to low oxygen conditions to be related to differences in the vertical swimming abilities of these organisms or physiological tolerances to hypoxia and anoxia. Overall, species composition and relative abundance of organisms in the sediment reflected patterns of pelagic larval abundance. These results demonstrate that the supply of meroplanktonic larvae appears to determine the recovery population and that the response of plakton to low oxygen waters varies among taxa.