Spiecker Barbara J, Menge Bruce A
Department of Integrative Biology Oregon State University Corvallis Oregon USA.
Department of Biological Sciences University of New Hampshire Durham New Hampshire USA.
Ecol Evol. 2024 Mar 7;14(3):e10704. doi: 10.1002/ece3.10704. eCollection 2024 Mar.
Top-down and bottom-up factors and their interaction highlight the interdependence of resources and consumer impacts on food webs and ecosystems. Variation in the strength of upwelling-mediated ecological controls (i.e., light availability and herbivory) between early and late succession stages is less well understood from the standpoint of influencing algal functional group composition. We experimentally tested the effect of light, grazing, and disturbance on rocky intertidal turf-forming algal communities. Studies were conducted on the South Island of New Zealand at Raramai on the east coast (a persistent downwelling region) and Twelve Mile Beach on the west coast (an intermittent upwelling region). Herbivory, light availability, and algal cover were manipulated and percent cover of major macroalgal functional groups and sessile invertebrates were measured monthly from October 2017 to March 2018. By distinguishing between algal functional groups and including different starting conditions in our design, we found that the mosaic-like pattern of bare rock intermingled with diverse turf-forming algae at Twelve Mile Beach was driven by a complex array of species interactions, including grazing, predation, preemptive competition and interference competition, colonization rates, and these interactions were modulated by light availability and other environmental conditions. Raramai results contrasted with those at Twelve Mile Beach in showing stronger effects of grazing and relatively weak effects of other interactions, low colonization rates of invertebrates, and light effects limited to crustose algae. Our study highlights the potential importance of an upwelling-mediated 3-way interaction among herbivory, light availability, and preemption in structuring contrasting low rocky intertidal macroalgal communities.
自上而下和自下而上的因素及其相互作用凸显了资源与消费者对食物网和生态系统影响之间的相互依存关系。从影响藻类功能群组成的角度来看，早期和晚期演替阶段上升流介导的生态控制（即光照可用性和食草作用）强度的变化尚不太清楚。我们通过实验测试了光照、放牧和干扰对潮间带岩石上形成草皮的藻类群落的影响。研究在新西兰南岛东海岸的拉拉迈（一个持续下沉流区域）和西海岸的十二英里海滩（一个间歇性上升流区域）进行。对食草作用、光照可用性和藻类覆盖进行了调控，并在2017年10月至2018年3月期间每月测量主要大型藻类功能群和固着无脊椎动物的覆盖百分比。通过在我们的设计中区分藻类功能群并纳入不同的起始条件，我们发现十二英里海滩上裸岩与各种形成草皮的藻类交织的马赛克状模式是由一系列复杂的物种相互作用驱动的，包括放牧、捕食、抢先竞争和干扰竞争、定殖率，并且这些相互作用受到光照可用性和其他环境条件的调节。拉拉迈的结果与十二英里海滩的结果形成对比，显示出放牧的影响更强，其他相互作用的影响相对较弱，无脊椎动物的定殖率较低，并且光照影响仅限于壳状藻类。我们的研究强调了上升流介导的食草作用、光照可用性和抢先占据之间的三向相互作用在构建对比鲜明的低潮间带大型藻类群落中的潜在重要性。
