Long-term biological effects of coastal hypoxia in Corpus Christi Bay, Texas, USA

Abstract

Hypoxia (low oxygen conditions) occurs in the southeastern region of Corpus Christi Bay, Texas, U.S.A. every summer. Previously, it was found that there were direct effects on macrobenthic infauna (i.e., reduced biomass, abundance and diversity), and even though invertebrates were found primarily in the surface sediments of the hypoxic area, there was no significant indication of indirect effects (i.e., increased predation pressure). The purpose of the current study is to identify long-term effects (14–19 years) of hypoxia by comparing the dynamics of communities of infauna collected by sediment cores and epifauna collected from trawls in and out of the hypoxic zone in Corpus Christi Bay. The benthic infaunal community is distinctly degraded in the hypoxic zone in terms of long-term average abundance, biomass, and diversity. The loss is primarily from the surface — rather than deep-dwelling infauna. The epibenthic community of fish and mobile invertebrates has a higher long-term average abundance in the hypoxic area, but lower diversity. Although epifaunal diversity was lower in the hypoxic area for both infauna and epifauna, the long-term dynamics are different because species accumulation over time was similar between the two sites for epifauna, but very low for infauna in the hypoxic area. The hypoxic community is a subset of the normoxic community for both infauna and epifauna, indicating that stress is affecting taxa intolerant of low oxygen conditions.