The Role of Light, Predation and Flow in Structuring Marine Subtidal Communities

海洋无脊椎动物群落垂直或下切岩壁往往显着不同的水平表面。 垂直的墙壁通常港口高多样性的组合固着悬浮饲养无脊椎动物，而水平表面往往占主导地位的大型藻类。 通常对这种模式的解释包括：1）阴影，这可能会减缓藻类的生长，因此有利于无脊椎动物的优势。 2)在垂直表面上缺乏干扰，特别是捕食。 3)不会在墙壁上沉积，从而使悬浮给料器免于堵塞过滤系统。 4)增加水流量的墙壁，这可能会提高幼虫招聘和食物供应悬浮馈线。 然而，这些不同的过程在塑造这种普遍存在的模式中的实际作用还有待实验测试。本项目将调查阴影，捕食和流动的相对重要性，增加垂直和水平表面之间的群落结构和组成的差异。待检验的主要预测是：1）由于光照水平降低，丰富的无脊椎动物群落在墙上发展。 这一假设将通过使用中性密度的有色丙烯酸来遮蔽水平的岩石表面和使用镜子来增加垂直表面上的光来进行测试。2）捕食限制了水平表面上无脊椎动物群落的发展。这一假设将通过两个单独的处理来检验：从实验地块中移除海胆（主要的无脊椎动物捕食者），并将所有捕食者关在笼子里。 水平表面上的水流将通过安装在底层上方的丙烯酸挡板来增加。 实验处理将在所有可能的组合中执行，以检测每个过程的相对重要性，以及过程之间的相互作用。所有工作将在缅因州南部海湾的马萨诸塞州纳汉特的一个现场进行。 无脊椎动物的固着悬浮物可以非常长寿，可能是一个多样化的海洋群落的关键栖息地改造者。 维持潮下带岩壁群落的力量还有待严格的研究。 这项研究将提供重要的洞察力，调节潮下带群落结构的过程，并使这些过程的影响，人为变化的预测。要调查的模式的一般性表明，结果可能适用于全球潮下带生境。

Marine invertebrate communities on vertical or undercut rock walls often differ dramatically from those on horizontal surfaces. Vertical walls typically harbor high-diversity assemblages of sessile suspension-feeding invertebrates, while horizontal surfaces tend to be dominated by macroalgae. Commonly invoked explanations for this pattern include: 1) Shading, which may slow algal growth and therefore favor invertebrate dominance. 2) Lack of disturbance, particularly predation, on vertical surfaces. 3) Lack of sedimentation on walls, thus freeing suspension feeders from clogged filtration systems. 4) Increased water flow on walls, which may enhance larval recruitment and food supply to suspension feeders. However, the actual roles of these different processes in shaping this ubiquitous pattern have yet to be tested experimentally.This project will investigate the relative importance of shading, predation, and flow increating differences in community structure and composition between vertical and horizontalsurfaces. The main predictions to be tested are: 1) Rich invertebrate animal communities develop on walls due to reduced light levels. This hypothesis will be tested by using neutral-density tinted acrylic to shade horizontal rock surfaces and using mirrors to augment light on vertical surfaces.2) Predation limits the development of invertebrate communities on horizontal surfaces. This hypothesis will be tested via two separate treatments: removal of sea urchins (majorinvertebrate predators) from experimental plots, and caging to exclude all predators.3) Increased water flow facilitates development of invertebrate communities. Flow over horizontal surfaces will be augmented via acrylic baffles mounted above the substratum. Experimental treatments will be executed in all possible combinations to detect the relative importance of each of the processes examined, as well as interactions among processes. All work will be conducted at a field site in Nahant, Massachusetts, in the southern Gulf of Maine. Sessile suspension feeding invertebrates can be very long-lived, and may be keystone habitat modifiers for a diverse marine community. The forces maintaining subtidal rock wall communities have yet to be rigorously examined. This study will provide important insight into the processes that regulate subtidal community structure, and enable prediction of the impact of anthropogenic changes on these processes. The generality of the pattern to be investigated suggests that results may apply to subtidal habitats globally.