Impacts of submarine groundwater discharge on benthic community composition and functional diversity on coral reefs in Mo'orea, French Polynesia from Aug 2021 to Jun 2022

Coral reefs experience numerous natural and anthropogenic environmental gradients that alter biophysical conditions and affect biodiversity. While many studies have focused on drivers of reef biodiversity using traditional diversity metrics (e.g., species richness, diversity, evenness), less is known about how environmental variability may influence functional diversity. In this study, we tested the impact of submarine groundwater discharge (SGD) on taxonomic and functional diversity metrics in Mo'orea, French Polynesia. SGD is the expulsion of terrestrial fresh or recirculated seawater into marine environments and is associated with reduced temperatures, pH, and salinity and elevated nutrient levels. Using a regression approach along the SGD gradient, we found that taxon and functional-entity richness displayed unimodal relationships to SGD parameters, primarily nitrate + nitrite and phosphate variability, with peak richness at moderate SGD for stony coral and the full benthic community. Macroalgae showed this unimodal pattern for functional-entity but not taxonomic richness. Functional community composition (presence and abundance of functional entities) increased along the gradient, while taxonomic composition showed a nonlinear relationship to SGD-related parameters. SGD is a common feature of many coastal ecosystems globally and therefore may be more important to structuring benthic functional diversity than previously thought. Further, studying community shifts through a functional-trait lens may provide important insights into the roles of community functions on ecosystem processes and stability, leading to improved management strategies. This dataset includes site identifiers and survey metadata, substrate composition, structural complexity (rugosity), seawater parameters (salinity, temperature, pH, nutrients), taxonomic and functional traits of benthic taxa (morphology, calcification strategy, trophic group), proportional cover of benthic taxa, and community-level diversity metrics.珊瑚礁面临诸多自然与人为形成的环境梯度，这些梯度会改变生物物理环境，并对生物多样性产生影响。尽管已有诸多研究借助传统多样性指标（如物种丰富度、多样性指数、均匀度）探讨珊瑚礁生物多样性的驱动因子，但对于环境变异如何影响功能多样性的认知仍较为匮乏。本研究以法属波利尼西亚的莫雷阿岛（Mo'orea）为研究区域，探讨了海底地下水排泄（submarine groundwater discharge, SGD）对分类学多样性与功能多样性指标的影响。SGD指陆地淡水或再循环海水向海洋环境的排泄过程，其通常伴随水温、pH值与盐度的降低，以及营养盐水平的升高。本研究沿SGD梯度采用回归分析方法，结果显示：分类单元丰富度与功能单元丰富度均与SGD相关参数（主要为硝酸盐+亚硝酸盐与磷酸盐的变异程度）呈单峰关系；在中度SGD条件下，石珊瑚与底栖生物全群落的丰富度达到峰值。大型藻类仅在功能单元丰富度上呈现该单峰模式，分类单元丰富度则无此规律。功能群落组成（即功能单元的存在与丰度）随SGD梯度呈上升趋势，而分类学群落组成与SGD相关参数则呈非线性关系。SGD是全球众多沿海生态系统的普遍特征，因此其对底栖生物功能多样性构建的重要性可能远超此前认知。此外，通过功能性状视角解析群落结构变化，可深入揭示群落功能在生态系统过程与稳定性中的作用，从而助力优化海洋管理策略。本数据集包含样点标识符与调查元数据、底质组成、结构复杂度（rugosity）、海水参数（盐度、温度、pH值、营养盐）、底栖生物分类单元的分类学与功能性状（形态、钙化策略、营养类群）、底栖生物分类单元的盖度占比，以及群落水平的多样性指标。