Coastal Ecosystems Section, Applied Sciences Bureau, South Florida Water Management District, 3301 Gun Club Rd., West Palm Beach, FL, 33406, USA,
Environ Manage. 2013 Oct;52(4):981-94. doi: 10.1007/s00267-013-0136-3. Epub 2013 Aug 7.
Oyster beds are disappearing worldwide through a combination of over-harvesting, diseases, and salinity alterations in the coastal zone. Sensitivity of oysters to variable discharge and salinity is particularly acute in small sub-tropical estuaries subject to regulated freshwater releases. South Florida has sub-tropical estuaries where watershed flood control sometimes results in excessive freshwater inflow to estuaries during the wet season (May-Oct) and reduced discharge and increased salinities in the dry season (Nov-Apr). The potential to reserve freshwater accumulated during the wet season could offer the capacity to regulate freshwater at different temporal scales, thus optimizing salinity conditions for estuarine biota. The goal of this study was to use simulation modeling to explore the effects of freshwater inflows and salinity on adult oyster survival in the Caloosahatchee River Estuary (CRE) in southwest Florida. Water managers derived three different freshwater inflow scenarios for the CRE based on historical and modified watershed attributes for the time period of 1965-2000. Three different salinity time series were generated from the inflow scenarios at each of three sites in the lower CRE and used to conduct nine different oyster simulations. Overall, the predicted densities of adult oysters in the upstream site were 3-4 times greater in seasons that experienced reduced freshwater inflow (e.g., increased salinity) with oyster density in the lower estuary much less influenced by the inflows. Potential storage of freshwater reduced the frequency of extreme flows in the wet season and helped to maintain minimum inflow in the dry season near the estuarine mouth. Analyses of inflows indicated that discharges ranging from 0 to 1,500 cfs could promote favorable salinities of 10-25 in the lower CRE depending on wet versus dry season climatic conditions. This range of inflows is similar to that derived in other studies of the CRE and emphasizes the value of simulation models to help prescribe freshwater releases which benefit estuarine biota.
世界各地的牡蛎养殖场正因为过度捕捞、疾病和沿海地区盐度变化等多种因素而消失。在受淡水调控释放影响的亚热带小型河口，牡蛎对流量和盐度变化的敏感性尤其强烈。南佛罗里达州有亚热带河口，流域洪水控制有时会导致河口在雨季（5 月至 10 月）过度流入淡水，而在旱季（11 月至 4 月）则减少流量并增加盐度。在雨季蓄积淡水的潜力可以提供在不同时间尺度上调节淡水的能力，从而优化河口生物群的盐度条件。本研究的目的是利用模拟模型来探讨淡水流入和盐度对佛罗里达州西南部卡拉哈奇河河口（CRE）成年牡蛎生存的影响。水管理人员根据历史和修改后的流域属性，为 1965-2000 年期间的 CRE 制定了三种不同的淡水流入情景。在 CRE 下游的三个地点，从每个流入情景中生成了三个不同的盐度时间序列，并用于进行九种不同的牡蛎模拟。总体而言，在经历淡水流入减少（例如盐度增加）的季节，上游地点的成年牡蛎预测密度要高出 3-4 倍，而下游河口的牡蛎密度受流入的影响要小得多。淡水的潜在储存减少了雨季极端流量的发生频率，并有助于在河口口附近的旱季保持最小的流入量。对流入的分析表明，根据干湿季节的气候条件，流量在 0 至 1,500 cfs 之间变化可以促进 CRE 下游地区 10-25 的有利盐度。这个流量范围与其他 CRE 研究得出的范围相似，强调了模拟模型在帮助规定有利于河口生物群的淡水释放方面的价值。
