Morphometrics of seagrasses at species level, Moreton Bay, Australia determined from core samples collected in 2012-2013@en

Seagrass meadows are important marine carbon sinks, yet they are threatened and declining worldwide. Seagrass management and conservation requires adequate understanding of the physical and biological factors determining carbon content in seagrass sediments. Here, we identified key factors that influence carbon content in seagrass meadows across several environmental gradients in Moreton Bay, SE Queensland. Sampling was conducted in two regions: (1) Canopy Complexity, 98 sites on the Eastern Banks, where seagrass canopy structure and species composition varied while turbidity was consistently low; and (2) Turbidity Gradient, 11 locations across the entire bay, where turbidity varied among sampling locations. Sediment organic carbon content and seagrass structural complexity (shoot density, leaf area, and species specific characteristics) were measured from shallow sediment and seagrass biomass cores at each location, respectively. Environmental data were obtained from empirical measurements (water quality) and models (wave height). The key factors influencing carbon content in seagrass sediments were seagrass structural complexity, turbidity, water depth, and wave height. In the Canopy Complexity region, carbon content was higher for shallower sites and those with higher seagrass structural complexity. When turbidity varied along the Turbidity Gradient, carbon content was higher at sites with high turbidity. In both regions carbon content was consistently higher in sheltered areas with lower wave height. Seagrass canopy structure, water depth, turbidity, and hydrodynamic setting of seagrass meadows should therefore be considered in conservation and management strategies that aim to maximize sediment carbon content.海草床是重要的海洋碳汇，却正面临全球范围内的威胁与衰退。海草资源的管理与保护，需要充分明晰决定海草沉积物碳含量的物理与生物因子。本研究针对昆士兰州东南部莫顿湾的多类环境梯度，明确了影响海草床沉积物碳含量的关键因子。本次采样设置两个区域：(1) 冠层复杂度梯度区：东岸带共98个采样点，该区域内海草冠层结构与物种组成存在差异，但浊度始终处于较低水平；(2) 浊度梯度区：覆盖全海湾的11个采样点，各采样点间浊度存在差异。分别在各采样点通过浅层沉积物岩芯与海草生物量岩芯，测定沉积物有机碳含量与海草结构复杂度（包括枝条密度、叶面积及物种特异性特征）。环境数据则通过实地实测（水质）与模型模拟（波高）获取。影响海草沉积物碳含量的关键因子为海草结构复杂度、浊度、水深与波高。在冠层复杂度梯度区，浅水采样点及海草结构复杂度更高的点位，沉积物碳含量更高。在浊度梯度区，当浊度存在梯度变化时，高浊度点位的沉积物碳含量更高。两个区域内，波高更低的遮蔽区域，沉积物碳含量均始终处于较高水平。因此，在旨在最大化沉积物碳储量的海草床保护与管理策略中，应纳入海草冠层结构、水深、浊度及海草床水动力环境这几项关键要素。