Data_Sheet_1_Species-Specific Trait Responses of Three Tropical Seagrasses to Multiple Stressors: The Case of Increasing Temperature and Nutrient Enrichment.docx

Seagrass meadows are declining globally. The decrease of seagrass area is influenced by the simultaneous occurrence of many factors at the local and global scale, including nutrient enrichment and climate change. This study aims to find out how increasing temperature and nutrient enrichment affect the morphological, biochemical and physiological responses of three coexisting tropical species, Thalassia hemprichii, Cymodocea serrulata and Halophila stipulacea. To achieve these aims, a 1-month experiment under laboratory conditions combining two temperature (maximum ambient temperature and current average temperature) and two nutrient (high and low N and P concentrations) treatments was conducted. The results showed that the seagrasses were differentially affected by all treatments depending on their life-history strategies. Under higher temperature treatments, C. serrulata showed photo-acclimation strategies, while T. hemprichii showed decreased photo-physiological performance. In contrast, T. hemprichii was resistant to nutrient over-enrichment, showing enhanced nutrient content and physiological changes, but C. serrulata suffered BG nutrient loss. The limited response of H. stipulacea to nutrient enrichment or high temperature suggests that this seagrass is a tolerant species that may have a dormancy state with lower photosynthetic performance and smaller-size individuals. Interaction between both factors was limited and generally showed antagonistic effects only on morphological and biochemical traits, but not on physiological traits. These results highlight the different effects and strategies co-inhabiting seagrasses have in response to environmental changes, showing winners and losers of a climate change scenario that may eventually cause biodiversity loss. Trait responses to these stressors could potentially make the seagrasses weaker to cope with following events, due to BG biomass or nutrient loss. This is of importance as biodiversity loss in tropical seagrass ecosystems could change the overall effectiveness of ecosystem functions and services provided by the seagrass meadows.

全球范围内，海草床正呈现出衰退趋势。海草面积的减少受到多种因素的综合影响，这些因素包括局部和全球尺度上的营养盐富集以及气候变化。本研究旨在探究温度升高和营养盐富集如何影响三种共存的亚热带物种——Thalassia hemprichii、Cymodocea serrulata和Halophila stipulacea——的形态、生化及生理响应。为实现这一目标，本研究在实验室条件下进行了一个为期一个月的实验，实验结合了两种温度处理（最高环境温度和当前平均温度）及两种营养盐处理（高浓度和低浓度氮磷）。结果显示，海草对各种处理的响应存在差异，这取决于其生命周期策略。在高温处理下，C. serrulata表现出光适应策略，而T. hemprichii则显示出光合生理性能的下降。相反，T. hemprichii对营养盐过度富集具有抗性，显示出增强的营养含量和生理变化，但C. serrulata则遭受了背景营养盐的损失。H. stipulacea对营养盐富集或高温的有限响应表明，这种海草是一种耐受性物种，可能存在休眠状态，具有较低的光合性能和较小的个体尺寸。这两个因素的相互作用有限，并且通常仅在形态和生化特性上表现出拮抗效应，而不会影响生理特性。这些结果表明，共栖海草对环境变化的响应存在差异，展示了气候变化情景下的赢家和输家，这可能导致生物多样性的丧失。对这些胁迫的响应特征可能会使海草在面对后续事件时变得更为脆弱，这是由于背景生物量或营养盐的损失。这对于热带海草生态系统中的生物多样性丧失可能改变海草床提供的整体生态系统功能和服务的有效性具有重要意义。