Seascapes as drivers of herbivore assemblages in coral reef ecosystems

Herbivorous fish maintain a critical ecosystem function on coral reefs by grazing algae and maintaining highly productive algal turf assemblages. Current paradigms implicate habitat complexity, predation and primary productivity as major drivers of the distribution and abundance of herbivorous fish, yet little is known about the relative contribution of these factors. Here, we compare bottom-up and top-down drivers of notional herbivore assemblages across an environmental gradient of wave exposure in the Palau archipelago. We surveyed herbivore assemblages at reef slopes (6 - 9m) across 18 sites, and quantified proxies of top-down control (predator biomass, habitat complexity) and bottom-up drivers (net primary production, nutrients) at each site. Despite substantial variability in herbivore biomass throughout the archipelago (6 to 65 g m-2), general additive models indicate that neither top-down nor bottom-up drivers significantly predicted biomass or density of herbivores among sites....

植食性鱼类通过啃食藻类、维持高生产力的藻席群落，在珊瑚礁生态系统中发挥着关键的生态系统功能。当前主流研究范式认为，栖息地复杂度、捕食作用与初级生产力是调控植食性鱼类分布与丰度的主要驱动因子，但学界对这些因子的相对贡献仍知之甚少。本研究在帕劳群岛的波浪暴露环境梯度下，对比分析植食性鱼类群落的上行控制（bottom-up）与下行控制（top-down）驱动因子。我们在18个调查位点的6-9米水深礁坡上开展了植食性鱼类群落调查，并在每个位点量化了下行控制的替代指标（捕食者生物量、栖息地复杂度）与上行控制驱动因子（净初级生产力、营养盐）。尽管整个群岛范围内的植食性鱼类生物量存在显著波动（6至65 g·m⁻²），但广义可加模型分析结果显示，无论是下行还是上行控制因子，均无法显著预测不同位点的植食性鱼类生物量与密度……