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Data from: Ecological effects of habitat complexity vary with intertidal elevation: Implications for seawall eco-engineering

Vozzo, Maria1; Bishop, Melanie2; Dafforn, Katherine2; Mayer Pinto, Mariana3

Published Apr 22, 2025 on Dryad. https://doi.org/10.5061/dryad.9p8cz8wtr

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Apr 22, 2025 version files 605.76 KB

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Abstract

Coastal urbanisation is replacing natural shoreline habitats with built structures, such as seawalls. Built structures often lack complex habitat features that provide protective and cool microhabitats for biodiversity. We conducted field experiments to assess whether the addition (or eco-engineering) of complex habitat panels to seawalls influenced benthic community assemblages across the intertidal range, at panel and site scales. We expected: (i) effects of habitat complexity to vary with tidal elevation, reflecting spatial variation in the identity and magnitude of stressors from which habitat complexity provides protection; (ii) positive effects of complexity on functional groups of organisms with exposed soft tissues that make them prone to desiccation and predation, and especially on the high shore where temperature and desiccation is greatest, and (iii) increases in the upper vertical limit of key taxa inhabiting eco-engineered seawalls to match reference reefs, and exceed control seawalls, depending on the type of habitat complexity provided. Effects of habitat complexity increased with tidal emersion and varied by functional group. In the mid- and high-intertidal, across which temperatures increased, complex panels supported over two times the abundance of key taxa than flat control panels. In the low-intertidal, brown algae were more abundant on flat than complex panels, whereas mobile invertebrates with exoskeletons responded positively to complexity in the high-intertidal, and mobile soft-bodied invertebrates were only found in complex habitats of the mid-intertidal. Cool microhabitats (pools, shaded depressions) of complex habitat panels were important in supporting key taxa and functional groups at higher intertidal elevations than on flat surfaces, and that, often, matched natural rocky shores.

Synthesis and applications: Our results demonstrate that the addition of habitat complexity through eco-engineering can promote key functional groups of algae and invertebrates on seawalls, but effects vary across tidal elevation gradients and with the type of complexity provided. Consequently, to achieve desired outcomes, eco-engineering interventions must be applied with knowledge of key limiting factors to target taxa, and of spatial variation in these limiting factors across small-scale gradients such as intertidal elevation, as well as sites.