Ricardo Gerard F, Jones Ross J, Negri Andrew P, Stocker Roman
Australian Institute of Marine Science, Townsville, 4810, Queensland, and Perth, 6009, Western Australia, Australia.
Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Perth, 6009, Western Australia, Australia.
Sci Rep. 2016 Feb 22;6:21567. doi: 10.1038/srep21567.
Spawning synchrony represents a common reproductive strategy in sessile marine organisms and for broadcast spawning corals, buoyancy of egg-sperm bundles is critical to maximise fertilisation at the ocean surface. Here we demonstrate a novel threat to coral reproduction whereby buoyant egg-sperm bundles intercept and are "ballasted" by sediment grains on their journey to the ocean surface, preventing them from reaching the ocean surface and greatly reducing egg-sperm encounter rates. Empirical observations of this mechanism are successfully captured by a mathematical model that predicts the reduction in ascent probability and egg-sperm encounters as a function of sediment load. When applied to 15 m deep reefs, the model predicts that 10% and 50% reductions in egg-sperm encounters occur at 35 mg L(-1) and 87 mg L(-1) suspended sediment concentrations, respectively, and for a 5 m deep reef a 10% reduction occurs at 106 mg L(-1). These concentrations are commonly associated with sediment plumes from dredging or natural resuspension events. The potential for sediments to sink coral gametes highlights the need to carefully manage the timing of turbidity-generating human activities near reefs during spawning periods.
产卵同步是固着海洋生物常见的繁殖策略，对于体外受精的珊瑚来说，精卵束的浮力对于在海洋表面实现最大程度的受精至关重要。在此，我们展示了一种对珊瑚繁殖的新威胁，即浮力精卵束在前往海洋表面的过程中会拦截沉积物颗粒并被其“压载”，阻止它们到达海洋表面，并大大降低精卵相遇率。一个数学模型成功捕捉到了这种机制的实证观察结果，该模型预测上升概率和精卵相遇的减少是沉积物负荷的函数。当应用于15米深的珊瑚礁时，该模型预测，在悬浮沉积物浓度分别为35毫克/升和87毫克/升时，精卵相遇率分别降低10%和50%；对于5米深的珊瑚礁，在106毫克/升时精卵相遇率降低10%。这些浓度通常与疏浚或自然再悬浮事件产生的沉积物羽流有关。沉积物使珊瑚配子下沉的可能性凸显了在产卵期谨慎管理珊瑚礁附近产生浑浊的人类活动时间的必要性。
