Cascading effects of global climate change on near shore benthic communities in the Antarctic

Metadata record for data from ASAC Project 2300See the link below for public details on this project.---- Public Summary from Project----Antarctic reefs, like their tropical counterparts, harbour a high diversity of animal life. For the first time we will determine how global warming will affect food availability to the animals which comprise the structural components of the reefs. Ultimately, we wish to predict the cascading effect through the community as one component changes.With the confirmation that sponges in Antarctic waters graze on ultraplankton there is now a global overview that sponges are the primary benthic organism that is responsible for linking the pelagic microbial food web to the benthos. Like other shallow water demosponges, sponges in Antarctica are omnivorous sponges that graze nonselectively, consuming both heterotrophic and phototrophic organisms. Retention efficiencies of ultraplankton are similar to other sponges measured using similar techniques from shallow water to the deep sea, the tropics to boreal waters. The large amounts of water processed by these benthic suspension feeders and their diet places these sponges squarely within the functional group of organisms that link the pelagic microbial food web to the benthos. The number of macroinvertebrates that have been shown to side- step the microbial loop and directly utilize the base of the microbial food web as a primary food source is ever growing and currently includes demosponges, ascidians, soft corals, and bivalves. Dense macroinvertebrate communities dominated by demosponges and corals in shallow water have been shown to remove as much as 90% of the ultraplankton from the water that passes over them. The daily fluxes of ultraplankton to these communities ranges from 9 to 1970 mg C day-1 m-2. We conservatively estimate that this single species of sponge, which comprises only a portion of the benthos, mediates a flux of 444 mg mg C day-1 m-2 from the water column, which places it in the range of shallow-water temperate and boreal systems.Furthermore, we found that physical disturbance results in changes in community structure. The subtidal rocky coasts near Casey are similar to many of the exposed rocky coasts of the world that support extensive stands of macroalgae that form a strong positive association with understorey encrusting coralline algae. Loss of canopies of algae on temperate coasts often triggers large and predictable changes to the assemblage of understorey taxa. We observed large negative effects of removing canopies of H. grandifolius on encrusting corallines growing beneath, with such effects consistent with predictions of previous research on tropical and temperate coasts. However, elevating concentrations of nutrients did not greatly reduce the magnitude of the negative effects of canopy removal. Nevertheless, our results suggest that disturbance (removal) to canopies of H. grandifolius has large consequences for those organisms associated with this widely distributed (circumpolar) species of canopy-forming algae. See the full copy of the final report (available for download from the URL given below) for more information.Also included in the download file, are five Excel spreadsheets. The spreadsheets contain the data collected from the transects, quadrats, etc (see the final report for more information). Where possible the spreadsheets have been converted to csv files.The fields in this dataset are:LocationdepthSpeciesTransectQuadratIrradiancePAR

本数据集的元数据记录来自ASAC项目2300。如需查看该项目的公开详情，请参阅下方链接。
——项目公开摘要——
与热带珊瑚礁类似，南极礁域也孕育着高度多样的动物类群。本研究首次探明全球变暖将如何影响构成礁体结构组分的动物的食物可获得性，最终目标是预测当某一组分发生变化时，整个群落将产生的级联效应。

随着南极海域海绵捕食超微浮游生物（ultraplankton）这一结论得到证实，目前已形成一项全球性认知：海绵是连接水层微生物食物网与底栖生境的核心底栖生物。与其他浅海寻常海绵（demosponges）类似，南极海域的海绵为杂食性滤食者，会无选择性地捕食异养与自养生物。经同类技术（涵盖浅海至深海、热带至寒带海域）测定，南极海绵对超微浮游生物（ultraplankton）的保留效率与其他海绵物种基本一致。这类底栖滤食生物会处理海量水体，结合其摄食习性，可明确将其归入连接水层微生物食物网与底栖生境的功能类群。

已被证实可绕过微生物食物环、直接以微生物食物网底层作为主要食物来源的大型底栖无脊椎动物（macroinvertebrates）数量正不断增加，目前已知类群包括寻常海绵（demosponges）、被囊动物（ascidians）、软珊瑚与双壳类（bivalves）。研究表明，以寻常海绵（demosponges）和珊瑚为优势类群的浅海大型底栖无脊椎动物（macroinvertebrates）群落，可将流经其生境的水体中多达90%的超微浮游生物（ultraplankton）移除。此类群落每日接收的超微浮游生物（ultraplankton）通量介于9至1970毫克碳/(日·平方米)之间。我们保守估计，仅占底栖生物群落一部分的该单一海绵物种，可介导水体中444毫克碳/(日·平方米)的通量，这一数值处于温带与寒带浅海生态系统的通量区间内。

此外，我们发现物理扰动会导致群落结构发生改变。凯西站（Casey）附近的潮下带岩质海岸，与全球诸多裸露岩质海岸类似，均分布有大面积大型藻场（macroalgae），且这些藻场与下层附生结壳珊瑚藻存在显著的正相关关系。温带海岸的藻类冠层消失后，通常会引发下层类群群落结构出现可预测的显著变化。我们观察到移除H. grandifolius冠层对其下方附生的结壳珊瑚藻产生了显著负面影响，这一结果与此前热带、温带海岸相关研究的预测相符。然而，提升营养盐浓度并未显著削弱移除冠层所带来的负面影响程度。尽管如此，我们的研究结果表明，对H. grandifolius冠层的扰动（移除操作）会对与这种广布（环南极分布）的冠层藻类相关联的生物产生重大影响。如需了解更多详情，请查阅最终报告完整版（可通过下方提供的URL下载获取）。

下载包中还包含5个Excel电子表格，其中存储了通过样带（transects）、样方（quadrats）等方式采集的相关数据（详见最终报告）。在条件允许的情况下，这些电子表格已被转换为CSV（Comma-Separated Values）文件。

本数据集包含以下字段：位置、深度、物种、样带（transects）、样方（quadrats）、光合有效辐射（PAR，Photosynthetically Active Radiation）