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: 2:30:00 PM

Location: La Cienega

Levin, L, A, Marine Life Research Group, Scripps Institution of Oceanography, La Jolla, USA, llevin@ucsd.edu

Diaz, R, J, Virginia Institute of Marine Science, College of William and Mary, Gloucester Pt, USA, diaz@vims.edu

MACROFAUNAL COMMUNITY RESPONSE TO HYPOXIA: A COMPARISON OF PERMANENT VERSUS EPISODIC EXPOSURE

Large areas of the bathyal seafloor within oxygen minimum zones and some fjords and basins experience permanent severe hypoxia (<0.5 ml O2 per l). Macrofaunal communities within these regions exhibit reduced (or enhanced) densities, low species richness and evenness, and high dominance by annelids. Dominant species exhibit varying lifestyles and nutritional modes. These assemblages differ from shallower communities exposed to seasonal or episodic hypoxia in having: (a) much lower oxygen tolerance thresholds, (b) morphological adaptations to maximize respiratory surface, (c) specialist rather than opportunistic lifestyles, and (d) potential to utilize chemosynthesis-based nutritional pathways. Similarities between the systems include reduced macrofaunal diversity, commonality of family level taxa such as spionid polychaetes, tubificid oligochaetes and ampeliscid amphipods. Temporal and spatial stability of dissolved oxygen concentration appears to be a primary factor regulating community structure and function in both OMZs and shallow coastal hypoxic areas. Comparisons of the two regimes should contribute to better understanding of changes to be expected as hypoxic conditions increase in spatial and temporal extent.

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Aquatic Sciences Meeting, Albuquerque 2001

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