Examining the diversity, stability and functioning of marine fish communities across a latitudinal gradient

Aim: As anthropogenic stressors on the biosphere intensify, understanding how communities respond to disturbances is critical. Biodiversity is often thought to promote the stability of communities over time and enhance ecosystem functioning. However, results have been inconsistent, and the multifaceted linkages among diversity, stability, and functioning under acute disturbances remain poorly understood. We experimentally tested the responses of marine fish communities to disturbance (i.e., acute habitat loss) across a diversity gradient spanning 35º degrees of latitude in the western Atlantic Ocean to assess the diversity-stability relationship and the interplay between diversity, stability, and fish biomass recovery (as a proxy for function) in marine fish communities.

Location: Western Atlantic Ocean (Maine, Massachusetts, North Carolina, Florida [USA], Belize, and Panama).

Time period: 2016 – 2017

Major taxa studied: Small, bottom-dwelling (‘cryptobenthic’) fishes

Results: Diversity showed a negative effect on community stability at both the regional (across docks) and local (within docks) scales. Similarly, local diversity was negatively correlated with ecosystem function. These effects are exacerbated by the habitat loss imposed via our experimental treatment.

Main conclusions: Our results suggest that habitat loss may more intensively re-shuffle diverse, tropical communities, which impacts biomass recovery, our proxy of functioning. Contrary to ecological theory, in small-bodied, benthos-associated vertebrate communities, biodiversity may neither promote stability nor functioning, suggesting that human disturbances may be particularly impactful in tropical, high-diversity ecosystems.

Methods
We experimentally tested the response of marine fish communities to disturbance across a diversity gradient on human-made dock pilings. We holistically sampled cryptobenthic fish communities, then we imposed a severe disturbance by removing all benthic epifauna. We then compared the community stability, defined as the constancy in community composition, on disturbed and undisturbed pilings after one year.

研究目的：随着生物圈面临的人为胁迫不断加剧，解析生物群落对干扰的响应机制已成为核心科学问题。长期以来，学界普遍认为生物多样性可提升群落的时间稳定性，并增强生态系统功能。然而相关研究结果始终存在分歧，且在急性干扰情境下，多样性、稳定性与生态系统功能之间的多维度关联仍未得到充分阐明。本研究通过野外控制实验，在西大西洋跨越35个纬度的多样性梯度上，探究海洋鱼类群落对（急性生境丧失）干扰的响应，以此评估生物多样性-群落稳定性关系，以及海洋鱼类群落中多样性、稳定性与以鱼体生物量恢复为功能替代指标的相互作用机制。
研究区域：西大西洋海域（涵盖美国缅因州、马萨诸塞州、北卡罗来纳州、佛罗里达州，以及伯利兹和巴拿马）。
研究时段：2016年—2017年
研究类群：小型底栖栖息（cryptobenthic）鱼类
研究结果：在区域尺度（各码头间）与局地尺度（码头内部）上，生物多样性均对群落稳定性产生负向影响。同理，局地生物多样性与生态系统功能呈负相关关系。上述效应会因本实验施加的生境丧失处理而进一步加剧。
主要结论：本研究结果表明，生境丧失可能会更强烈地重塑物种多样的热带群落，进而对作为功能替代指标的生物量恢复产生影响。与经典生态学理论相悖的是，在小型底栖关联脊椎动物群落中，生物多样性既无法提升群落稳定性，也不能促进生态系统功能，这暗示人为干扰对物种多样性较高的热带生态系统可能具有格外显著的负面影响。
研究方法
本研究在人工码头桩柱上设置多样性梯度，开展海洋鱼类群落对干扰的响应控制实验。首先对隐蔽底栖鱼类群落进行全面采样，随后通过移除所有底栖表栖生物施加重度干扰。一年后，对比受干扰与未受干扰桩柱上的群落稳定性（定义为群落组成的恒定性）。