Ecosystem engineers and coastal sedimentary communities

沉积的海底覆盖了海洋领域的绝大部分。然而，我们对形成其生物多样性和功能的过程的理解仍然是零碎的。过去，大多数理论预测，在局部尺度上，捕食和物理因素对沉积群落的调节起着至关重要的作用。然而，随后的许多研究也表明，栖息地形成物种的建立对于塑造这些系统的多样性和功能至关重要。这些基础物种通常被称为（自生的）生态系统工程师，它们有能力创造或改变栖息地的属性，促进新的、更复杂的群落的发展。在岩石海岸、海带森林、红树林、珊瑚礁甚至盐沼系统中，生态系统工程师的作用已经得到了很好的研究。然而，在非构造的沉积底部，特别是在加拿大大西洋地区，还有许多有待探索和测试。越来越多的证据表明，生态系统工程师可能在沉积环境下的群落属性和服务中发挥关键作用，但关于他们在不同营养水平内和之间发生的物种相互作用中所起的作用，还没有足够的信息。当我们看到有能力利用、消耗或破坏当地生态系统工程师的非本地物种的持续传播时，这是相关的，并开启了有关它们之间相互作用的相关问题，最终，关于这些工程师在沉积系统中的实际作用。******这个研究项目的重点是几个杰出的生态系统工程师，他们分布在加拿大大西洋沿岸的沉积海岸线上：蓝贻贝、东部牡蛎、鳗草和岩草。该项目的主要目标是测试这些生态系统工程师对周围沉积动物的聚集和物种相互作用的影响，以及非本地物种对它们的潜在改变。通过三种主要的研究场景，本文提出了六个假设：生态系统工程师作为生态系统结构和功能的驱动者，他们作为自上而下相互作用的中介，以及他们作为本地入侵物种相互作用的中介。在大西洋地区的沉积区，特别是爱德华王子岛沿海地区，已经进行了大量的勘探工作，为提出和检验这些假设提供了基础。这项研究计划的结果将有助于我们了解生态系统工程师及其推动生物相互作用的作用。这一结果也将对群落调节、营养复杂性和海岸保护的理论产生影响。

***Sedimentary bottoms encompass a vast majority of the marine realm. Yet, our understanding of the processes that shape their biodiversity and function remains fragmentary. In the past, most theory predicted that at the local scale predation and physical factors would play a paramount role regulating sedimentary communities. However, numerous subsequent studies have also showed that the establishment of habitat-forming species is as critical to shape diversity and function in these systems. These foundation species, more generically known as (autogenic) ecosystem engineers, have the ability to create or alter the properties of a habitat, promoting the development of new, more complex communities. The role of ecosystem engineers has been well studied in rocky shores, kelp forests, mangroves, coral reefs, and even saltmarsh systems. However, in unstructured sedimentary bottoms, in particular those in Atlantic Canada, much remain to be explored and tested. Mounting evidence suggests that ecosystem engineers may play key roles on community attributes and services in sedimentary settings, but not enough information is available on their role driving the species interactions occurring within and among different trophic levels. This is relevant at a time when we witness the ongoing spread of non-indigenous species that have the ability to exploit, consume or disrupt local ecosystem engineers, and opens relevant questions about their interactions and, ultimately, about the actual role of these engineers on sedimentary systems. ******This research program focuses on several prominent ecosystem engineers present and scattered along sedimentary shorelines of Atlantic Canada: blue mussels, eastern oysters, eelgrass, and rockweeds. The main goal of this program is testing the effects of these ecosystem engineers on the assembly and species interactions of surrounding sedimentary infauna and their potential alteration by non-indigenous species. Six hypotheses are addressed by working on three main research scenarios: Ecosystem engineers as drivers of infaunal structure and function, their role as mediators of top-down interactions, and their role as mediators of native-invader species interactions. A considerable amount of exploratory work already conducted in sedimentary areas in the Atlantic region, and coastal Prince Edward Island in particular, provides the basis to propose and test each of these hypotheses. The outcome of this research program will contribute to our knowledge on ecosystem engineers and their role driving biological interactions. Such outcome will also have implications for theory on community regulation, trophic complexity, and coastal conservation.