Effects of inundation duration on southeastern Louisiana oyster reefs

Danielle A Marshall,Megan K La Peyre,Keith Walters

doi:10.1017/exp.2020.35

Danielle A Marshall, Megan K La Peyre + Show 1 more

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https://doi.org/10.1017/exp.2020.35

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Abstract

AbstractUnderstanding the effects of predicted rising sea levels, combined with changes in precipitation and freshwater inflow on key estuarine ecosystem engineers such as the eastern oyster would provide critical information to inform restoration design and predictive models. Using oyster ladders with shell bags placed at three heights to capture a range of inundation levels, oyster growth of naturally recruited spat was monitored over the course of 6 months. Oyster numbers and shell heights were consistently highest in bottom and mid bags experiencing greater than 50% inundation (mid: 63 ± 7%; bottom: 95 ± 3%). Identifying thresholds for optimal oyster growth and survival to enhance restoration engineering would require finer scale evaluation of inundation levels.

Highlights

Oyster reef restoration is increasingly used as a tool to ameliorate the negative effects of overharvesting and habitat degradation (Blomberg et al, 2018)
The threshold between a successful or failed restoration may be a matter of centimeters (Fodrie et al, 2014) with increased inundation time often resulting in biological stressors, and reduced inundation time resulting in increased abiotic stressors
Oysters recruited in the bags continuously through the study, with increased spat observed in the August and October samplings (Figure 3, Supplementary Table S1)

Summary

Introduction

Oyster reef restoration is increasingly used as a tool to ameliorate the negative effects of overharvesting and habitat degradation (Blomberg et al, 2018). In Louisiana, eastern oyster (Crassostrea virginica) reefs provide extensive habitat (La Peyre et al, 2019), and support a valuable industry (NOAA, 2020). These oyster populations thrive in Louisiana’s estuaries, and exist both inter- and sub-tidally, but restoration projects struggle to identify inundation thresholds for designed reefs. With changing sea levels and variation in reef elevations, understanding how inundation time might affect oyster growth, survival and reef sustainability is critical (Ridge et al, 2015; Solomon et al, 2014). The threshold between a successful or failed restoration may be a matter of centimeters (Fodrie et al, 2014) with increased inundation time often resulting in biological stressors (i.e., increased predation and biofouling), and reduced inundation time resulting in increased abiotic stressors (i.e., desiccation; Bishop & Peterson, 2006)

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Discussion

Conclusion