Mangrove expansion into temperate marshes alters habitat quality for recruiting Callinectes spp.

Abstract

Beyond direct habitat loss, climate change can alter habitat quality and availability by stimulating shifts in foundation species ranges. Tropical mangroves are proliferating at the intersection with temperate saltmarshes and continue moving poleward with unknown consequences for inhabitant marine fauna. We expected that mangrove and marsh foundation species differ in habitat quality, due at least in part to differences in their structural attributes, such that shifts from marsh to mangrove wetlands alter habitat availability for wetland inhabi -Tants. We coupled recruitment surveys and laboratory experiments to assess the influences of foundation species' structural and non-structural attributes on Callinectes spp. recruitment, preference, and survival among mangrove and marsh habitats. Re - cruitment was evident in Spartina alterniflora and Rhizophora mangle intertidal habitats but not in Avicennia germinans. In laboratory trials, S. alterniflora was preferred in the presence of predation risk and provided the highest probabilities of survival, indi - cating that settlers can distinguish among ecotone vegetation types and that their choices correspond to habitat quality. Survival probability and recruit persistence were comparatively low in mangrove habitats. The differences in habitat use, preference, and survival identified in this study suggest that mangrove expansion is diminishing wetland habitat for Callinectes spp. It also reveals that changes between habitat-forming species, and not just the loss of structure per se, can affect habitat quality, such that foundation species may not replace one another functionally where they displace each other spatially.