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首页> 外文期刊>Estuarine Coastal and Shelf Science >Giant kelp forests at critical light thresholds show compromised ecological resilience to environmental and biological drivers
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Giant kelp forests at critical light thresholds show compromised ecological resilience to environmental and biological drivers

机译：临界光阈值下的巨型海带森林显示出对环境和生物驱动器的生态适应力下降

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摘要

Replacement of kelp and fucoid forests by low biomass turfing communities or urchin barrens has been identified in temperate marine ecosystems worldwide. Variation in the mechanisms of decline (e.g., urchin grazing, temperature stress) and apparent driving stressors (e.g., overfishing, sedimentation, global warming) has greatly limited the development of generalized management strategies. Thresholds of urchin density and thermal tolerance for habitat-forming seaweeds are increasingly well established, yet thresholds of turbidity are rarely considered. Given the universal requirement for light in aquatic macrophytes, estimation of photosynthetically active radiation (PAR) limits may help underpin frameworks for better management of terrestrial stressors. Here I have examined spatial and temporal variability of PAR in forests of the giant kelp Macrocystis pyrifera across a gradient of exposure to land-derived sediments. Exposure to excess suspended sediments pushed PAR below critical thresholds for net sporophyte growth ( 1.0 mol m(-2) day(-1)), affecting giant kelp densities, but also impacting a range of ecological metrics including: fucoid density; laminarian density; beta diversity metrics; subcanopy composition; and urchin density. While kelps and fucoids responded to similar light thresholds, kelps appear to be vulnerable to physical disruption by sediments whereas fucoids are tolerant of physical disruption mechanisms, but vulnerable to declining light availability. Light thresholds of 1.0 mol m(-2) day(-1) may be a useful target for management of stressors affecting water clarity (e.g., sedimentation, eutrophication), with universal applicability across diverse groups of aquatic photoautotrophs.
机译：在全球温带海洋生态系统中，已经发现低生物量的草皮群落或海胆贫瘠的土地替代了海带和岩藻林。下降机制（例如野孩子放牧，温度胁迫）和明显的驱动因素（例如过度捕捞，沉积，全球变暖）的变化极大地限制了通用管理策略的发展。对于形成栖息地的海藻，海胆密度和耐热性的阈值越来越完善，但是很少考虑浊度的阈值。鉴于水生植物对光的普遍需求，对光合有效辐射（PAR）限值的估算可能有助于加强框架，以更好地管理陆地应激源。在这里，我研究了大型海藻巨噬紫ifer森林在暴露于陆源沉积物的梯度上的PAR的时空变化。暴露于过量的悬浮沉积物使PAR低于净孢子体生长的临界阈值（<1.0 mol m（-2）day（-1）），影响了巨大的海藻密度，但也影响了一系列的生态指标，包括：岩藻土密度；层流密度Beta多样性指标；亚冠组成和海胆密度。虽然海藻和岩藻糖对相似的光阈值做出响应，但海藻似乎很容易受到沉积物的物理破坏，而岩藻糖耐物理破坏机制，但易受光利用率下降的影响。 1.0 mol m（-2）day（-1）的光阈值可能是管理影响水澄清度（例如沉淀，富营养化）的应激源的有用目标，并且在不同种类的水生自养生物中具有普遍适用性。

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