Species Diversity of Brachyuran Crabs Around Helgoland - An Overview

Biodiversity surveys are a crucial measure of ecosystem health and necessary to detect changes in populations and habitats. This study aims to provide insight into community patterns of marine invertebrates. Given their high abundance and ecological significance, Brachyuran crabs were selected as a model group to document population dynamics and reflect the current status of biodiversity loss in the North Sea. We collected specimens from two sites- the intertidal zone and the Helgoland Trench Region (HTR). As anticipated, species composition in open-water habitats differed greatly from the intertidal zone. On the rocky shore, the native Carcinus maenas dominated over the invasive Hemigrapsus sanguineus, whereas Polybius depurator replaced Polybius holsatus as the most prevalent species within the HTR. Additionally, a pronounced male-biased sex ratio was observed, likely as a result of behavioral dimorphism, leading to increased male activity in the subtidal.