Characterizing spatio-temporal changes in benthic communities: Taxonomic and functional trajectories of intertidal assemblages in the bay of Saint-Brieuc (English Channel)

Using ecological trajectories to track long‐term taxonomic and functional changes in benthic shallow soft‐bottom communities (Bay of Saint‐Brieuc, English Channel)

“…The diversity of temporal dynamics suggests a complex gradient of sensitivity to organic matter enrichment and the implication of additional driving factors. Indeed, (1) discards from scallop dredging could promote opportunistic species and scavengers leading to increases in their abundances (Depestele et al, 2019), and (2) by capturing nutrients, green tides are particularly suspected to buffer the influence of nutrient enrichment on macrofauna as discussed by Ponsero & Le Mao (2011) and Sturbois et al (accepted) concerning the neighbouring intertidal area.…”

“…Pers.)] , and of Limecola balthica in the nearby intertidal mudflats of the bay of Saint‐Brieuc (Sturbois et al, accepted).…”

“…Despite bordering the National Nature Reserve of the bay of Saint‐Brieuc and partially belonging to the Natura 2000 “Baie de Saint‐Brieuc‐Est” site (FR5300066), the study area is exposed to a number of anthropogenic pressures including mussel culture, scallop dredging and eutrophication. Mussels are farmed on bouchots (wooden poles, Figure 1) in the north‐eastern part of the intertidal area, occupying 277 ha and 312 ha in 1987 and 2019, respectively (Sturbois et al, accepted) and are also farmed on ropes in the western part of the study area, around stations 81, 99 and 100. The sea bed is also exposed to long‐term scallop dredging activities as the bay of Saint‐Brieuc is characterized by the highest fishing pressure in Brittany (Appendix A‐1).…”

“…Regulation changes have led, since 2010, to the concentration of dredging, at the beginning of the fishing season, in areas colonized by the non‐indigenous slipper limpet Crepidula fornicata (Appendix A‐2). The bay also suffers from eutrophication resulting in macroalgae proliferation and cyclic green tides episodes (Charlier et al, 2007; Gravier, 2012), which notably impact fish nursery grounds (Le Luherne et al, 2016; Le Luherne et al, 2017) and influence the dynamics of some benthic populations of invertebrates of the intertidal area (Sturbois et al, accepted).…”

“…Rance estuary, (Desroy & Retière, 2004), bay of Seine (Dauvin & Desroy, 2005; Desroy et al, 2007; Bacouillard et al, 2020) or bay of Mont‐Saint‐Michel (Trigui, 2009)]. In the bay of Saint‐Brieuc (Western English Channel), the ecological state of subtidal communities defined in 1987 by Gros & Hamon (1988) has never been updated, contrasting with the monitoring strategy deployed in the adjacent intertidal area, partially protected since 1998 by a National Nature Reserve primarily devoted to the conservation of birds and, de facto , to benthic habitats (Sturbois et al, accepted). This shallow subtidal area, belonging to the “Baie de Saint‐Brieuc – Est” Natura 2000 site, supports intense fishing activities (dominated by scallop dredging) and mussel rope culture.…”