LTREB, Community Ecology on Rocky Shores: Long-Term Research in the Subtidal Zone (Massachusetts, 1978 - 2003)

在北方马萨诸塞州的三个地点的Sebens岩石潮下带群落现在已经连续研究了20年。 方法包括标记样方的摄影，捕食者丰度的横断面，和物理环境的选定方面的测量。 自1978年以来，海胆（Strongylocentrotus droebachiensis）的种群密度急剧增加，而大多数鱼类的种群却减少了。 Sebens博士和同事们还记录了几种非本地物种的出现和影响;掠食性裸鳃类Tritonia plebeia和殖民地海鞘Botrylloides sp.是最成功的，对本地生物群落产生了可衡量的影响。 其他非本土海鞘（Botryllus schlosseri，Styela clava，Diplosoma sp.）在这些地点很少出现，尚未形成稳定的当地种群。Tritonia对珊瑚Alcyonium siderium的种群产生了严重影响，至今仍未恢复。 去除Alcyonium的Tritonia和海胆人口密度增加一倍（1984年至1986年期间）造成了大部分其他无脊椎动物的垂直岩石表面的下降，并增加了表面的程度占主导地位的甲壳珊瑚藻。在1978- 1988年期间，当海胆在1989年扩展到新的区域时，以海带和叶状红藻为主的水平表面减少为海胆贫瘠地（珊瑚为主）。 Botrylloides sp.在岩壁和水平面上建立了殖民地，即使是在海胆放牧激烈的地方，因此可能有阻止海胆的防御措施。海胆人口增加的协同效应，以及在十年内出现的几个非土著物种，造成了这些网站的无脊椎动物和藻类组合的重大转变。持续的高海胆密度可能有利于抗海胆的空间优势种，包括珊瑚藻、海葵（Metridium senile）、海绵（Isodictya spp.）和非本土物种，如Botrylloides sp. 这些研究（1978-1997）在北方马萨诸塞州潮下带的岩石表面产生和测试的假说，长期稳定性和短期调节的群落结构的岩石基质。以前的研究主要集中在岩壁上物种之间的相互作用，几种最常见物种的种群生物学，以及水运动对个体，种群和群落过程的影响。 本项目是长期研究的延伸：实验和相关的方法将用于解决捕食，物理效应，幼虫扩散，招募之间的相互作用，以及对群落结构的影响。这项研究的目标是：1）确定构成社区的重要的长期和短暂过程（物理的，生物的），2）确定哪些过程有强烈的直接和间接影响（如海胆捕食）对群落结构的影响，3）对补充及其对群落的影响进行定量研究，（4）将这些研究结果应用于景观中孤立亚单元上的物种共存和群落结构模型，并使用多个扩散尺度。一旦完成，将对长期数据集进行统计学检查（自相关，互相关，其他时间序列分析），以确定哪些物理过程和哪些捕食者种群与共同空间占用者覆盖率的变化最密切相关。 该项目继续进行长期研究，每年进行4-6次考察，在马萨诸塞州海岸沿着8公里的5个实地点采用摄影、录像和直接（SCUBA）取样（样方、样带）。

9811576SebensRocky subtidal communities at three sites in Northern Massachusetts have now been under continuous study for up to 20 years. Methods include photography of marked quadrats, transects of predator abundance, and measurement of selected aspects of the physical environment. Since 1978, there has been a dramatic increase in sea urchin (Strongylocentrotus droebachiensis) population density and a decrease in most fish populations. Dr. Sebens and collaboartors have also recorded the appearance and effects of several non-indigenous species; the predatory nudibranch Tritonia plebeia and the colonial ascidian Botrylloides sp. have been the most successful, and have had measurable effects on indigenous assemblages. Other non-indigenous ascidians (Botryllus schlosseri, Styela clava, Diplosoma sp.) appeared only rarely at these sites, and have not yet developed stable local populations. Tritonia had a severe impact on populations of the octocoral Alcyonium siderium, which still have not recovered. The removal of Alcyonium by Tritonia and the doubling of sea urchin population density (both during 1984-1986) caused a major decline in most other invertebrates on vertical rock surfaces, and an increase in the extent of surfaces dominated by crustose coralline algae. Horizontal surfaces dominated by kelp and foliose red algae during 1978--1988 were reduced to urchin barrens (coralline-dominated) when urchins expanded into new areas in 1989. Botrylloides sp. established colonies on rock walls and horizontal surfaces, even where urchin grazing is intense, and thus may have defenses that deter urchins. The synergistic effects of urchin population increase, and the appearance of several nonindigenous species within one decade, has caused a major shift in invertebrate and algal assemblages at these sites. Continued high urchin densities could favor urchin-resistant spatial dominants, which include coralline algae, sea anemones (Metridium senile), sponges (Isodictya spp.), and nonindigenous species such as Botrylloides sp. These studies of subtidal rock surfaces (1978-1997) in northern Massachusetts have produced and tested hypotheses concerning the long-term stability and short term regulation of community structure on rocky substrata. The previous research focused on the interactions among species on rock walls, on population biology of several of the most common species, and on the effects of water movement on individual, population, and community processes. The present project is an extension of the long-term research: an experimental and correlative approach will be used to address the interactions among predation, physical effects, larval dispersal, recruitment, and the resulting impact on community structure. The goals of the study are to: 1) identify important chronic and transient processes structuring the community (physical, biological), 2) determine which processes have strong direct and indirect effects (e.g. sea urchin predation) on community structure, 3) conduct quantitative studies of recruitment and its effects on the community, and 4) incorporate these findings into a model of species coexistence and community structure on isolated sub-units of a landscape, using multiple dispersal scales. Once complete, the long-term data set will be examined statistically (autocorrelation, cross-correlation, other time-series analyses) to determine which physical processes and which predator populations are most strongly correlated with changes in percent cover of the common space occupiers. This project continue long-term studies during 4-6 trips annually, using photographic, video, and direct (SCUBA) sampling (quadrat, transect) at five field sites along 8 km of the Massachusetts coast.