Ulaski Brian P, Sikes Derek S, Konar Brenda
College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, P.O. Box 757220, Fairbanks, AK, 99775-7220, USA.
University of Alaska Museum, Department of Biology & Wildlife, University of Alaska Fairbanks, 1962 Yukon Drive, Fairbanks, AK, 99775-6960, USA.
Mar Environ Res. 2023 May;187:105970. doi: 10.1016/j.marenvres.2023.105970. Epub 2023 Mar 28.
Seaweeds are foundation species across near-subtidal and intertidal zones, including when detached and free-floating and then cast ashore as wrack. Wrack is sometimes removed by humans for aesthetics or to be used as fertilizer. The study of wrack as an important habitat and resource for macroinvertebrates in high latitudes has been limited. To determine which taxa might be impacted when wrack is removed, the composition and relative abundance of macroinvertebrates were quantified monthly and compared in areas with and without wrack in Kachemak Bay, Alaska. Relationships were assessed between macroinvertebrates and wrack line (tidal height, moisture content, seaweed biomass) and beach characteristics (wave exposure, beach slope, substrate types). Approximately 47,000 animals were counted and a total of 87 taxa were identified from beach-cast wrack, drifting wrack, and bare sediment habitats. Macroinvertebrate communities within beach-cast wrack and bare sediment habitats were significantly different. Beach-cast wrack generally had more terrestrially-derived animals, especially Coleoptera and Diptera. Bare beach sediment was predominantly occupied by Enchytraeida (annelids). Macroinvertebrate communities were most strongly influenced by seaweed biomass and tidal height of the wrack line. Beach-cast wrack and bare sediments were also compared to drifting wrack in shallow, nearshore waters. Drifting wrack was different and generally occupied by more marine-derived animals, especially Amphipoda, Gastropoda, Mytilida, and Polychaeta. Ecological succession in decaying beach-cast wrack was documented, with decomposers (e.g., Amphipoda and Diptera) being early colonizers, and predators (e.g., Coleoptera and Hymenoptera) arriving later. Understanding the importance of this unique and ecologically important habitat to macroinvertebrates is essential, as removals and reductions in wrack availability could influence macroinvertebrate community structure, higher trophic level consumers, and key ecological processes on beaches. This study is the first direct investigation into seaweed wrack-associated macroinvertebrate communities in a sub-Arctic system.
海藻是近潮下带和潮间带的基础物种，包括当它们脱离附着、自由漂浮，然后作为漂积物被冲上岸时。人类有时会出于美观或用作肥料的目的清除漂积物。在高纬度地区，对作为大型无脊椎动物重要栖息地和资源的漂积物的研究一直很有限。为了确定清除漂积物时哪些分类群可能受到影响，在阿拉斯加卡切马克湾有漂积物和无漂积物的区域，每月对大型无脊椎动物的组成和相对丰度进行量化并比较。评估了大型无脊椎动物与漂积物线（潮位高度、含水量、海藻生物量）和海滩特征（波浪暴露程度、海滩坡度、基质类型）之间的关系。在海滩冲上岸的漂积物、漂流的漂积物和裸露沉积物栖息地中，共统计了约47000只动物，鉴定出了87个分类群。海滩冲上岸的漂积物栖息地和裸露沉积物栖息地中的大型无脊椎动物群落有显著差异。海滩冲上岸的漂积物通常有更多来自陆地的动物，尤其是鞘翅目和双翅目。裸露的海滩沉积物主要被线蚓科（环节动物）占据。大型无脊椎动物群落受海藻生物量和漂积物线的潮位高度影响最大。还将海滩冲上岸的漂积物和裸露沉积物与浅海近岸水域的漂流漂积物进行了比较。漂流的漂积物有所不同，通常有更多来自海洋的动物，尤其是端足目、腹足纲、贻贝目和多毛纲。记录了腐烂的海滩冲上岸漂积物中的生态演替过程，分解者（如端足目和双翅目）是早期定居者，捕食者（如鞘翅目和膜翅目）随后到达。了解这个独特且具有重要生态意义的栖息地对大型无脊椎动物的重要性至关重要，因为漂积物数量的减少可能会影响大型无脊椎动物群落结构、更高营养级的消费者以及海滩上的关键生态过程。这项研究是对亚北极系统中与海藻漂积物相关的大型无脊椎动物群落的首次直接调查。
