Doropoulos Christopher, Gómez-Lemos Luis A, Salee Kinam, McLaughlin M James, Tebben Jan, Van Koningsveld Mark, Feng Ming, Babcock Russell C
CSIRO Oceans and Atmosphere, St Lucia, Queensland, Australia.
Universidad Nacional de Colombia - Sede de La Paz - Escuela de Pregrados, La Paz, Colombia.
Ecol Appl. 2022 Apr;32(3):e2558. doi: 10.1002/eap.2558. Epub 2022 Mar 13.
Positive feedbacks driving habitat-forming species recovery and population growth are often lost as ecosystems degrade. For such systems, identifying mechanisms that limit the re-establishment of critical positive feedbacks is key to facilitating recovery. Theory predicts the primary drivers limiting system recovery shift from biological to physical as abiotic stress increases, but recent work has demonstrated that this seldom happens. We combined field and laboratory experiments to identify variation in limitations to coral recovery along an environmental stress gradient at Ningaloo Reef and Exmouth Gulf in northwest Australia. Many reefs in the region are coral depauperate due to recent cyclones and thermal stress. In general, recovery trajectories are prolonged due to limited coral recruitment. Consistent with theory, clearer water reefs under low thermal stress appear limited by biological interactions: competition with turf algae caused high mortality of newly settled corals and upright macroalgal stands drove mortality in transplanted juvenile corals. Laboratory experiments showed a positive relationship between crustose coralline algae cover and coral settlement, but only in the absence of sedimentation. Contrary to expectation, coral recovery does not appear limited by the survival or growth of recruits on turbid reefs under higher thermal stress, but to exceptionally low larval supply. Laboratory experiments showed that larval survival and settlement are unaffected by seawater quality across the study region. Rather, connectivity models predicted that many of the more turbid reefs in the Gulf are predominantly self seeded, receiving limited supply under degraded reef states. Overall, we find that the influence of oceanography can overwhelm the influences of physical and biological interactions on recovery potential at locations where environmental stressors are high, whereas populations in relatively benign physical conditions are predominantly structured by local ecological drivers. Such context-dependent information can help guide expectations and assist managers in optimizing strategies for spatial conservation planning for system recovery.
随着生态系统退化，驱动栖息地形成物种恢复和种群增长的正反馈往往会丧失。对于这类系统，识别限制关键正反馈重新建立的机制是促进恢复的关键。理论预测，随着非生物胁迫的增加，限制系统恢复的主要驱动因素会从生物因素转变为物理因素，但最近的研究表明这种情况很少发生。我们结合了野外和实验室实验，以确定澳大利亚西北部宁格鲁礁和埃克斯茅斯湾沿环境胁迫梯度珊瑚恢复的限制因素变化。由于近期的气旋和热胁迫，该地区许多珊瑚礁的珊瑚数量稀少。一般来说，由于珊瑚补充受限，恢复轨迹会延长。与理论一致，低热胁迫下水质较清澈的珊瑚礁似乎受到生物相互作用的限制：与草皮藻的竞争导致新定居珊瑚的高死亡率，直立大型海藻林导致移植的幼体珊瑚死亡。实验室实验表明，在没有沉积物的情况下，壳状珊瑚藻覆盖度与珊瑚定居之间存在正相关关系。与预期相反，在高热胁迫下，浑浊珊瑚礁上的珊瑚恢复似乎不受新招募个体的存活或生长限制，而是受幼虫供应异常低的限制。实验室实验表明，整个研究区域的幼虫存活和定居不受海水质量的影响。相反，连通性模型预测，海湾中许多较浑浊的珊瑚礁主要是自我播种，在退化的珊瑚礁状态下接收的供应有限。总体而言，我们发现，在环境压力源较高的地区，海洋学的影响可能会压倒物理和生物相互作用对恢复潜力的影响，而处于相对良性物理条件下的种群主要由当地生态驱动因素构成。这种依赖背景的信息有助于指导预期，并协助管理者优化系统恢复的空间保护规划策略。
