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Holding Your Breath for Hypoxia Assessment Tools? Evaluating Benthic IBI’s in the Northern Gulf of Mexico
Citation:
Paul, J., B. Jarvis, AND J. Nestlerode. Holding Your Breath for Hypoxia Assessment Tools? Evaluating Benthic IBI’s in the Northern Gulf of Mexico. Gulf of Mexico Conference (GoMCon), Baton Rouge, LA, April 25 - 28, 2022.
Impact/Purpose:
We present an evaluation of estuarine benthic ecological condition indicators along a transect of Pensacola Bay estuary spanning a salinity gradient and across sites known to experience density stratification and seasonal hypoxia in the bottom layer. This presentation should be of interest to scientists and managers from across the Gulf of Mexico region concerned with monitoring and managment of estuarine habitats as it may inform the future use and application of various taxonomic-based benthic indicator tools for describing ecosystem condition.
Description:
Seasonal hypoxia is a primary concern for coastal ecosystems and applying the appropriate benthic index to assess local impacts is important. Thus, our objectives were to evaluate indices, comparing their sensitivity to detecting impacts of oxygen stress on habitat condition: AMBI (AZTI marine biotic index), M-AMBI (multivariate AMBI), GOM-IBI (Gulf of Mexico-IBI), and SB-IBI (sensitive Beck’s index). Index sensitivity was evaluated with linear mixed models followed by likelihood ratio tests for DO, and comparing AIC values. A transect with eight stations was established in the Pensacola Bay system (Florida) across the salinity gradient between the river and Gulf. We sampled monthly May to November in 2016 and 2017 for water, sediment, and macrobenthos. We observed near-bottom hypoxia at every station and was most pronounced near the middle of the salinity gradient. Generally, index scores trended toward better habitat condition with increasing salinity, with the lowest scores observed near the river. M-AMBI was the most sensitive to changes in dissolved oxygen (p<<0.001) with the lowest AIC value (-178) followed by AMBI (p<0.01, AIC=88.3), SB-IBI (p=0.03, AIC=334) and GoM-IBI (p=0.77, AIC=497.5). These results are a step toward validating the use of these tools in a Gulf coast estuary.
