Links between hydrologic modifications, flow and salinity regimes, and submerged aquatic vegetation (SAV) species composition and abundance were assessed with an empirical analysis of 33 years of monitoring data collected at nine sites in Florida’s Caloosahatchee River Estuary (CRE). Freshwater inflows to the estuary (30-day means) were often outside the previously recommended envelope of 12.74 to 79.29 m³ s⁻¹. Discharges from Lake Okeechobee through a synthetic hydrologic link were responsible for 43% of the above-envelope flows, but reduced the incidence of below-envelope flows by 30%. A salinity model and salinity stress indices developed for each SAV species indicated that the observed flows generated variable salinity conditions likely to harm both seagrasses and freshwater SAV in the estuary. Regression modeling of SAV abundance generally confirmed the flow and salinity responses expected for each species: Halodule wrightii and Thalassia testudinum in the lower estuary were both harmed by high-flow, low-salinity conditions, while Vallisneria americana in the upper estuary was decimated by low-flow, high-salinity conditions. There was a species-specific effect of the seasonal timing of high flows—T. testudinum was more negatively correlated with high flows in the dry season; H. wrightii in the wet season. The regression analyses also highlighted strong, year-to-year autocorrelations in SAV abundance, indicating reduced resilience after severe losses, particularly for V. americana. Large residual variation in some regression models suggested that factors other than salinity (e.g., optical water quality or grazing impacts) may also influence the system dynamics and should be incorporated in continuing research. This analysis suggests that use of artificial water management infrastructure to reduce extreme high and low flows to the Caloosahatchee and other estuaries could help maintain SAV health in light of intensifying climate variability and degraded watershed flow regulation capacity.

中文翻译：

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亚热带河口的淹没植被对气候变化和水文变化的响应：解释33年的变化

通过对佛罗里达州卡卢萨哈哈奇河河口（CRE）九个地点收集的33年监测数据的经验分析，评估了水文改良，流量和盐度状况以及水下水生植物（SAV）物种组成和丰度之间的联系。淡水流入河口（平均30天）通常不在先前建议的12.74至79.29 m ³  s ^-1范围内。通过合成水文联系从奥基乔比湖排放的水占上信封流量的43％，但将下信封流量的发生率降低了30％。针对每种SAV物种开发的盐度模型和盐度应力指数表明，观测到的水流产生了可变的盐度条件，可能会损害河口的海草和淡水SAV。SAV丰度的回归模型通常可以确认每种物种的流量和盐度响应：低河口的Halodule wrightii和Thalassia testudinum均受到高流量，低盐度条件的损害，而美国Vallisneria在低河口，高盐度的条件下，河口的水被大量淹没。有高的季节定时的物种特异性效应flows- T. testudinum用在干燥的季节高流量更负相关; H. wrightii在雨季。回归分析还强调了SAV丰度的逐年自相关性，表明严重损失后抵御力的下降，尤其是美洲对虾。一些回归模型中的较大残留变化表明，盐度以外的其他因素（例如光学水质或掠食影响）也可能影响系统动力学，应将其纳入继续研究中。该分析表明，鉴于气候变化加剧和流域流量调节能力下降，使用人工水管理基础设施来减少流向Caloosahatchee和其他河口的极高和极低流量可以帮助维持SAV健康。