Title: “Alive in the dead zone: Direct and indirect effects of hypoxia on Copepods”

Speaker: 
Dr. James J Pierson, UMCES Horn Point Laboratory

Abstract: 
The Chesapeake Bay experiences low-oxygen (hypoxic) water below the pycnocline every summer, but the direct and indirect impacts of hypoxia on plankton populations are not well understood, particularly in relation to hypoxic impact on trophic dynamics. Further, definitions of hypoxia based on volume or mass concentrations do not generally consider the effects of temperature on physiological condition of the organisms or the solubility of dissolved oxygen. We conducted a series of process studies to distinguishing the direct effects of hypoxia from food web impacts on the dominant copepod Acartia tonsa. We found enhanced predation on the copepods under hypoxic conditions; ctenophore predation peaked under warmer temperatures and more severe hypoxic conditions, and juvenile anchovy predation peaked under moderate temperatures and hypoxic conditions. Direct, sub-lethal impacts of low dissolved oxygen are likely more important to A. tonsa under severe hypoxia and anoxia. But discerning the impact of hypoxia requires consideration of temperature dependent metabolic rates and oxygen solubility as well as food-web impacts of hypoxia on top-down and bottom-up processes.

Host: Dr. Yantao Li, Ph.D.

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