Macrofauna community structure and population dynamics in the Flemish bank region: Assessing long-term change in the Anthropocene

Abstract

Benthic communities in continental shelf seas are influenced by human activities, yet assessing long-term change remains impeded by the scarcity of baseline data predating the proliferation of human activities. In this study, we considered the oldest macrofauna data from Van Veen samples collected in autumn 1970–1971 in a shallow soft-sediment seabed south of the Nieuwpoort Bank in the Belgian Part of the North Sea (BPNS). Both archived data in notebooks and hitherto unprocessed samples were considered. The community structure and biodiversity of these samples were compared with samples from autumn 2016. Furthermore, we compared (bi)monthly dynamics of indicator taxa for muddy sands (Abra spp.) and fine-medium sands (Nephtys spp.) present in the area with a time series collected in 2002–2003. Our findings reveal that both habitat types became richer in macrofauna species number and diversity. The invasive species that colonized the area between sampling periods explained <1 % of observed community structure changes. Overall, most taxa had higher population densities in 2016 compared to 1970–1971. Population densities varied seasonally, peaking in August 2016, and with less distinct recruitment dynamics in 1970–1971, confirming lower overall population densities in that period, especially for Abra. We discuss these results in relation to datasets discrepancies, climate variability, and sediment fining, acknowledging limitations in sampling design and processing methods. Nevertheless, this data rescue exercise proved valuable for understanding marine ecosystem changes, highlighting the potential of ‘old’ archived data and samples from the early Anthropocene.