Aquatic Sciences Meeting, Albuquerque 2001

SS35 Biological and Ecological Responses to Low Oxygen in Constant and Fluctuating Environments (Spatial and Temporal Connections)

Date: Thursday, February 15, 2001, Time: 2:45:00 PM

Location: La Cienega

Rabalais, N, N, Louisiana Universities Marine Consortium, Chauvin, LA 70344, USA, nrabalais@lumcon.edu

WHAT ARE THE EFFECTS OF SEASONALLY SEVERE HYPOXIA ON CONTINENTAL SHELF BENTHOS AND IMPLICATIONS TO FISHERIES?

Severe hypoxia occurs over broad areas of the Louisiana shelf most summers, coincident with habitat of commercially important species. Significant decreases in species richness, abundance and biomass of benthic organisms occur under severe hypoxia/anoxia. Effects at episodically-hypoxic sites are less severe or negligible, but masked by high variability consistent with pulses of biological productivity on a river-influenced shelf. Short-lived hypoxic episodes may not lessen habitat value for fisheries species in other systems and in fact may facilitate predation upon benthos. As oxygen concentration falls on the Louisiana shelf, fish move away from the area before the benthos are stressed, in contrast to other areas. If the duration or severity of hypoxia worsens, community composition and trophic interactions are likely to shift and affect energy transfer. Areas on the periphery of severe hypoxia and spring recruitment in hypoxic areas are characterized by opportunistic species. While biomass may be periodically high or turnover of opportunists may provide suitable prey, the overall productivity of the benthic system, transfer to other trophic levels, and secondary production, including fisheries, in general are not known.

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Aquatic Sciences Meeting, Albuquerque 2001

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