Low Dissolved Oxygen - Direct and Indirect Effects on Fisheries Species

Land use affects fish and fisheries both directly and indirectly through its affect on dissolved oxygen concentrations. In Chesapeake Bay, demonstration of populations-level effects on most finfish species has been ellusive. Clear effects on species and food web interactions in bottom-layer seasonally hypoxic waters may be compensated for and masked by a number of processes. In contrast, shallow water, diel cycling hypoxia may strongly affect disease dynamics, feeding and growth of oysters even though low oxygen lasts for only a few hours at a time and does not occur on all days. Lab experiments, field sampling and simple filtration rate models indicate that diel-cycling hypoxia increases acquisition and progression of Perkinsus marinus infections and decreases feeding and growth. Whether diel cycling hypoxia reduces success of oyster restoration, or whether oyster restoration reduces shallow-water diel cycling hypoxia may depend on the scale of restoration efforts.