Salinity is a major environmental predictor of phytoplankton species richness and composition. We hypothesize that the variation in phytoplankton richness along coastal salinity gradients is reflected in essential ecosystem functions like resource use efficiency (RUE)—the proportion of limiting resource that is converted into biomass. To test the hypothesis, we analyzed time series of phytoplankton and environmental variables from the Chesapeake Bay and the Baltic Sea. We analyzed the relationship among salinity, diversity, and RUE in bivariate and interaction association, and in structural equation model (SEM)—a form of path analysis to resolve multivariate relationships among interrelated variables. We concluded that the intrusion of marine water will lead to rapid change in species diversity on the fresh side. Despite diversity drop, individual community functions, like RUE, remain relatively resilient, reflecting functional redundancy. We propose that the salinity gradient also reflects trophic complexity, allowing stable resource use at reduced diversity.

中文翻译：

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沿海盐度连续体浮游植物群落多样性和生态系统功能的可预测变化

盐度是浮游植物物种丰富度和组成的主要环境预测因子。我们假设浮游植物丰富度沿沿海盐度梯度的变化反映在基本生态系统功能中，如资源利用效率 (RUE)——转化为生物量的限制资源的比例。为了验证该假设，我们分析了切萨皮克湾和波罗的海的浮游植物和环境变量的时间序列。我们分析了双变量和相互作用关联以及结构方程模型 (SEM) 中盐度、多样性和 RUE 之间的关系——一种用于解决相关变量之间多变量关系的路径分析形式。我们得出结论，海水入侵将导致淡水侧物种多样性的快速变化。尽管多样性下降，个别社区功能，如 RUE，保持相对弹性，反映功能冗余。我们提出盐度梯度也反映了营养的复杂性，允许在减少多样性的情况下稳定地使用资源。