Long-term response of coastal macrofauna communities to de-eutrophication and sea level rise mediated habitat changes (1980s versus 2018)

Abstract

Since the last decades, previous long-term Wadden Sea studies revealed significant changes in the abundance, biomass and spatial distribution of characteristic macrofauna communities in response to environmental changes and anthropogenic stressors. In this study, we performed statistical community analysis for the East-Frisian Wadden Sea (EFWS, southern North Sea) on two reference datasets across a period with severe climatic and environmental changes (1980s-2018). Therefore, historical macrofauna data from the Quantitative Sensitivity Mapping (1980s, SENSI 1) were reanalyzed and compared with data from the Synoptic Intertidal Benthic Survey (SIBES/SENSI 3) collected in 2018. Our results revealed significant quantitative and spatial changes in the characteristic macrofauna communities between the 1980s and 2018, most likely in response to de-eutrophication and sea level rise mediated habitat changes. Since the 1980s, the total number of taxa remained relatively stable (1980s: 90, 2018: 81), but the total abundance decreased by ca. -31% and the total biomass decreased by ca. -45%, particularly in the eastern regions of the study site probably due to de-eutrophication processes. Thereby, the mean abundances/m2 of ≥ -80% (1980s-2018) in the EFWS of several dominant species decreased: e.g. the gastropod Peringia ulvae, the polychaete Lanice conchilega and the bivalve Mya arenaria. In contrast, the mean abundance/m2 of one dominant species increased by ≥ +80% (1980s-2018): the invasive bivalve Ensis leei. The mean biomass [g/m2] of three dominant species decreased by ≥ -80% (1980s-2018): P. ulvae, L. conchilega and the amphipod Corophium volutator. In contrast, the mean biomass [g/m2] of one dominant species increased by ≥ +75% (1980s-2018): the polychaete Arenicola marina. In the western part of the EFWS, not only higher abundances of A. marina, but also of L. conchilega and P. ulvae were found in 2018, caused i.a. by sea level rise mediated decreasing mud contents and sand accretion on tidal flats. At the community level, the Oligochaeta/Heteromastus community increased in spatial distribution in the western EFWS in 2018 in the vicinity of increasing mussel/oyster beds.

Temporal change in phytoplankton diversity and functional group composition

“…This suggests that P has become the main limiting nutrient in the region(Philippart et al, 2007;Kuipers and van Noort, 2008;Ly et al, 2014;Leote et al, 2016). It would be expected that a reduction in nutrient loads would result in reductions in phytoplankton biomass, but our results, in agreement with other studies(Cadée and Hegeman, 1993;De Jonge, 1997;Singer et al, 2023;van Beusekom et al, 2019), do not con rm this expectation. De Jonge (1997) suggested that the remaining high primary production in the most western Dutch Station (MARSDND) could be explained by other sources of nutrient inputs, such as from the English Channel.…”

Baseline Inventory of Benthic Macrofauna in German Marine Protected Areas (2020–2022) before Closure for Bottom-Contact Fishing

“…One example of such a recently described species is the polychaete L. ramzega [ 83 ]. Spatial expansion of warm-temperate non-native species into German waters due to water temperature rise or changes in (de-)eutrophication [ 14 , 84 , 85 ], increasing number of newly introduced species [ 86 ], and disappearance of some native taxa are among expected drivers of future changes in species compositions. After closure for bottom-contact fishing in MPAs, those drivers might superimpose on effects of vanished bottom-contact fishing, and will act alongside high natural variability and unpredictable recruitment events particularly relevant in the young and temporally less stable Baltic Sea ecosystem.…”

A cross-border mud budget for future sediment management

“…These intertidal systems are composed of sand and mud. Mud plays a crucial role creating specific habitats for benthic species [43,66,67], and contributing to the current morphological evolution of the intertidal areas [46] as well as their ability to keep pace with SLR [68]. The rate at which sand is transported towards the intertidal areas is namely largely depending on the transport capacity [21], and will become a limiting factor under conditions of accelerated SLR [32,69,70].…”