Collaborative Research: Changes in ecosystem production and benthic biodiversity following the widespread loss of an ecosystem engineer

在许多生态系统中，单一优势物种的存在可以改变环境的物理条件，改变生物多样性、养分循环和初级生产的模式。这些“生态系统工程师”的流失会对生态系统的功能产生深远的影响。沿海海带提供了一个很好的例子，说明生物的结构改变了它们栖息地的物理特征（光、营养、水运动），并支持增强生物多样性。在过去的几十年里，阿留申群岛沿海水域的海带森林遭受了大规模的减少。该项目将利用从原地底栖生物室和船上孵育到利用卫星图像进行遥感等综合技术，研究这些损失如何影响生态系统生产模式和生物多样性。研究结果将有助于了解此类事件如何影响这个生态系统和其他生态系统。该项目将支持研究生，并通过一系列视频向公众介绍阿留申生态系统。调查人员还将与圣地亚哥的一名高中教师合作，将项目发现整合到课堂活动中，他们希望有一名教师参与他们的实地项目。研究人员将提出两个高度整合的问题：1)海带森林的广泛消失如何影响整个阿留申群岛的底栖生物生产力？2)海带森林的大面积消失如何影响整个群岛的底栖生物多样性和群落结构？为了解决这些问题，研究人员将估计10个岛屿的生产力变化，他们有关于海藻群落组成的历史数据和海带冠层覆盖的估计。他们将使用放置在海带森林和海胆贫瘠地的原位底栖生物室来测量净生态系统生产力（NEP）的样点尺度模式，并使用船上孵育来检查主要大型藻类的净初级生产力（NPP）。单个物种NPP率的数据将根据它们的生物量进行缩放，并结合整个群落的现场样地底栖动物室实验来估计所访问岛屿的新生态价值。通过首先将研究地点的结果外推到整个岛屿，然后再将结果外推到整个群岛，这些估计将被扩大到计算整个群岛的NEP。他们还将通过表征整个群岛的水柱辐照度和利用辐照度与光合作用之间的物种水平关系模拟NPP来估计生产的大尺度模式。将这些数据与水柱辐照度和群落呼吸的估计相结合，就可以对整个地区的新能源经济进行建模。底栖生物的生物多样性将通过潜水员调查和船上底栖拖网进行评估。在这些活动之后，可以追溯到20世纪80年代的海带冠层的卫星遥感和研究人员自己在这些岛屿和其他岛屿上的底栖大型藻类丰度的历史数据将被用来估计整个群岛的时空变化模式。

In many ecosystems the presence of a single dominant species can modify the physical conditions of the environment and alter patterns of biodiversity, nutrient cycling, and primary production. Losses of these "ecosystem engineers" can have profound impacts to how ecosystems function. Coastal kelps provide excellent examples of organisms whose structure modifies the physical characteristics of their habitats (light, nutrients, water motion) and supports enhanced biodiversity. The kelp forests in the coastal waters of the Aleutian Archipelago have suffered large-scale declines over the past several decades. This project will examine how these losses impact patterns of ecosystem production and biodiversity using a combination of techniques ranging from in situ benthic chambers and shipboard incubations to remote sensing using satellite imagery. The results will provide an understanding of how such events may impact this and other ecosystems. This project will support graduate students and will introduce the public to the Aleutian ecosystems in a series of videos. The investigators will also work with a San Diego high school teacher to integrate project findings into classroom activities, and they expect to involve a teacher in their field program. The investigators will ask two highly integrated questions: 1) How do the widespread losses of kelp forests impact benthic productivity across the Aleutian Archipelago? 2) How do the widespread losses of kelp forests impact benthic biodiversity and community structure across the archipelago? To address these, the investigators will estimate changes to productivity at ten islands where they have historic data on seaweed community composition and estimates of kelp canopy cover. They will use in situ benthic chambers placed in both kelp forests and urchin barrens to measure plot-scale patterns of net ecosystem productivity (NEP), and shipboard incubations to examine net primary productivity (NPP) for the dominant macroalgae. Data for individual species rates of NPP will be scaled by their biomass and combined with in situ plot-scale benthic chamber experiments of whole communities to estimate NEP at the islands visited. These estimates will be scaled up to calculate NEP across the entire archipelago by first extrapolating results from the study sites to entire islands, and then across the archipelago. They will also estimate broad-scale patterns in production by characterizing water column irradiances across the archipelago and modeling NPP using species-level relationships between irradiance and photosynthesis. Coupling these with estimates of water column irradiance and community respiration will allow modeling of NEP across this region. Benthic biodiversity will be assessed using diver surveys and shipboard benthic trawls. Following these activities, satellite remote sensing of the kelp canopies dating back to the 1980s and the investigators' own historical data on benthic macroalgal abundances at these and other islands will be used to estimate the temporal and spatial patterns of change across the archipelago.