Effects Of Low Oxygen Concentration On Meiofaunal Community Structure

The continental margin of the eastern Pacific harbors the single largest oxygen minimum zone (OMZ, O2< 0.5 ml l^-1) in the world. In contrast to the coastal areas that typically experience only episodic or seasonal hypoxia, continental margins intercepted by OMZs are permanently hypoxic in the deep sublittoral to bathyal benthic environment, creating strong gradients of bottom-water oxygen concentrations and organic matter input. These gradients influence both the biogeochemical properties of sediments and the structure of faunal communities, with severe reduction of macro- and megafauna abundance and diversity. However, there is evidence that meiofauna, are much less affected by low oxygen than the macrofauna. Meiofauna play a significant role in promoting the breakdown of organic matter, facilitating biomineralization and nutrient. Present knowledge of meiofaunal ecology along the EP OMZ is not commensurate with the crucial role this group plays in the benthic ecosystem regeneration, while serving as food for higher trophic levels.

By using meiofaunal samples collected during the San Diego Coastal Expedition at 6 stations across the OMZ off San Diego (~32N; 300 – 1200 m depth), we will test the hypotheses that low oxygen/high OM conditions influence meiofaunal patterns of abundance, taxonomic composition, and higher taxa diversity. The present research will provide a significant body of information on local meiofauna at the community level, and contribute to a better undersatding of the influence of hypoxia thresholds on marine biodiversity, of growing importance in the face of current OMZ expansion due to climate change.