Macrofauna abundance and sediment characteristics during R/V Senckenberg cruise west of Sylt in september 2010

The continuously influence of human impacts on the seafloor and benthic habitats demands the knowledge of clearly defined habitats to assess recent conditions and to monitor future changes. In this study, a benthic habitat dominated by sorted bedforms was mapped in 2010 using biological, sedimentological and acoustic data. This approach reveals the first interdisciplinary analysis of macrofauna communities in sorted bedforms in the German Bight. The study area covered 4 km², and was located ca. 3.5 km west of island of Sylt. Sorted bedforms formed as sinuous depressions with an east west orientation. Inside these depressions coarse sand covers the seafloor, while outside predominantly fine to medium sand was found. Based on the hydroacoustic data, two seafloor classes were identified. Acoustic class 1 was linked to coarse sand (type A) found inside these sorted bedforms, whereas acoustic class 2 was related to mainly fine to medium sands (type B). The two acoustic classes and sediment types corresponded with the macrofauna communities 1 and 2. The Aoinides paucibranchiata-Goniadella bobretzkii community on coarse sand and the Spiophanes bombyx - Magelona johnstonii community on fine sand. A transitional community 3 (Scoloplos armiger - Ophelia community), with species found in communities 1 and 2, could not be detected by hydroacoustic methods. This study showed the limits of the used acoustic methods, which were unable to detect insignificant differences in the fauna composition of sandy areas.

人类活动对海底及底栖生境（benthic habitats）的持续干扰，使得亟需对生境类型进行明确界定，以评估当前海洋环境状态并监测未来变化。本研究于2010年依托生物学、沉积学与声学数据，对以分选底形（sorted bedforms）为核心特征的底栖生境完成了制图工作，该方法首次实现了德国湾（German Bight）内分选底形生境中大型底栖动物群落（macrofauna communities）的跨学科分析。本次研究区域面积达4平方千米，位于叙尔特岛（Sylt）以西约3.5千米处。分选底形呈东西走向的蜿蜒凹陷形态，凹陷内部海底以粗砂为主要沉积物，外部则以细至中砂为主。基于水声探测数据（hydroacoustic data），研究共识别出两类海底类型：声学类型1对应分选底形内部的粗砂（A型沉积物），声学类型2则主要对应细至中砂（B型沉积物）。两类声学类型与沉积物类型分别匹配大型底栖动物群落1与群落2，其中粗砂生境对应Aoinides paucibranchiata-Goniadella bobretzkii群落，细砂生境对应Spiophanes bombyx-Magelona johnstonii群落。另有过渡群落3（Scoloplos armiger-Ophelia群落），其包含群落1与群落2的共有物种，但无法通过水声探测方法识别。本研究同时揭示了本次所用声学探测方法的局限性：其无法分辨沙质海域内动物群落组成的细微差异。