Department of Biology, Georgia Southern University, Statesboro, GA, USA.
Department of Geology and Geography, Georgia Southern University, Statesboro, GA, USA.
Mar Environ Res. 2021 Aug;170:105440. doi: 10.1016/j.marenvres.2021.105440. Epub 2021 Jul 28.
Reef-building eastern oysters, Crassostrea virginica, provide many ecosystem services, including production of valuable commercial products, formation of complex habitats, improved water quality and shoreline protection. Despite this, oyster populations have experienced dramatic declines throughout their range, spawning massive investment in management and restoration. Restoration efforts typically consider several well-studied metrics that normally influence oyster success; however, one potential factor that has not received much prior attention is submarine groundwater discharge (SGD). We conducted a series of field surveys and field experiments to explore the relationship between SGD and oysters in a marsh-lined tidal creek in Georgia, USA. SGD was mapped across multiple time points using a natural radon tracer (radon-222), and fluxes were paired with discrete measurements of oyster density, condition, size, recruitment and growth at multiple locations along the creek. Variation in oyster metrics was best explained by a combination of SGD, pH, and DO, which displayed a high degree of multicollinearity. We found an overall negative, nonlinear relationship between oyster density and groundwater flux. Interestingly, juvenile and adult condition and growth were not negatively impacted by groundwater. Rather, our results suggest that the likely mechanism for the density-flux relationship was interruption of the larval recruitment, which was also negatively related to flux. We hypothesize that larval interruption is due to the low dissolved oxygen and pH conditions of the groundwater at high flux sites. Overall, the interaction between SGD and oysters appears complex, and may be affected by other variables. This study provides evidence of a potential negative effect of a previously understudied natural phenomena on oyster demographics, and we suggest that SGD be considered in future management efforts.
造礁东方牡蛎（Crassostrea virginica）提供了许多生态系统服务，包括生产有价值的商业产品、形成复杂的栖息地、改善水质和保护海岸线。尽管如此，牡蛎种群在其分布范围内经历了急剧下降，这促使人们大量投资于管理和恢复。恢复工作通常考虑几个经过充分研究的指标，这些指标通常会影响牡蛎的成功；然而，一个潜在的因素尚未得到太多关注，那就是地下水排泄（SGD）。我们在美国佐治亚州的一条滨海潮汐溪进行了一系列实地调查和现场实验，以探索 SGD 与牡蛎之间的关系。使用天然氡示踪剂（氡-222）在多个时间点绘制了 SGD 图，并将通量与牡蛎密度、状况、大小、在溪流沿线多个位置的繁殖和生长的离散测量值进行了配对。牡蛎指标的变化最好用 SGD、pH 和 DO 的组合来解释，它们表现出高度的多重共线性。我们发现牡蛎密度与地下水通量之间存在总体上的负非线性关系。有趣的是，幼体和成年牡蛎的状况和生长不受地下水的负面影响。相反，我们的结果表明，密度-通量关系的可能机制是幼虫繁殖的中断，这也与通量呈负相关。我们假设，幼虫中断是由于高通量点的地下水溶解氧和 pH 值条件较低所致。总的来说，SGD 和牡蛎之间的相互作用似乎很复杂，并且可能受到其他变量的影响。本研究提供了先前研究较少的自然现象对牡蛎种群动态可能产生负面影响的证据，我们建议在未来的管理工作中考虑 SGD。
