The importance of water‐retaining features for biodiversity on artificial intertidal coastal defence structures

Abstract

Aim Artificial coastal defence structures are proliferating in response to rising and stormier seas. These structures provide habitat for many species but generally support lower biodiversity than natural habitats. This is primarily due to the absence of environmental heterogeneity and water-retaining features on artificial structures. We compared the epibiotic communities associated with artificial coastal defence structures and natural habitats to ask the following questions: (1) is species richness on emergent substrata greater in natural than artificial habitats and is the magnitude of this difference greater at mid than upper tidal levels; (2) is species richness greater in rock pools than emergent substrata and is the magnitude of this difference greater in artificial than natural habitats; and (3) in artificial habitats, is species richness in rock pools greater at mid than upper tidal levels?Location British Isles.Methods Standard non-destructive random sampling compared the effect of habitat type and tidal height on epibiota on natural rocky shores and artificial coastal defence structures.Results Natural emergent substrata supported greater species richness than artificial substrata. Species richness was greater at mid than upper tidal levels, particularly in artificial habitats. Rock pools supported greater species richness than emergent substrata, and this difference was more pronounced in artificial than natural habitats. Rock pools in artificial habitats supported greater species richness at mid than upper tidal levels.Main conclusions Artificial structures support lower biodiversity than natural habitats. This is primarily due to the lack of habitat heterogeneity in artificial habitats. Artificial structures can be modified to provide rock pools that promote biodiversity. The effect of rock pool creation will be more pronounced at mid than upper tidal levels. The challenge now is to establish at what tidal height the effect of pools becomes negligible and to determine the rock pool dimensions for optimum habitat enhancement.

Biodiversity surveys and stable isotope analyses reveal key differences in intertidal assemblages between tropical seawalls and rocky shores

“…Currently, a multitude of techniques to improve various physical factors of seawalls, for example topo-graphic complexity, slope angle, and elevation, have been attempted (Moreira et al 2007, Chapman & Blockley 2009, Firth et al 2013, Browne & Chapman 2014, Ido & Shimrit 2015, Martins et al 2016). Very few, however, have been targeted directly at recruiting a high abundance and diversity of native algal species (e.g.…”

Cool barnacles: Do common biogenic structures enhance or retard rates of deterioration of intertidal rocks and concrete?

“…Given that engineered structures offer novel surfaces for colonisation (Connell, 2001;Glasby and Connell, 1999;Moschella et al, 2005), organic influences on deterioration (whether negative or positive) are an important component of performance and durability to consider. At the same time, a recognition that artificial structures are often poor ecological surrogates for the natural rocky shores they may replace (e.g., Bulleri and Chapman, 2004;Gacia et al, 2007;Firth et al 2013;Firth et al 2016) is fuelling considerable international effort to develop and test ways of encouraging their colonisation. This includes structural design interventions and retrofit solutions aimed at facilitating settlement and recruitment of benthic species, to support biodiversity and maintain ecological function (e.g., Chapman and Blockley, 2009;Evans et al, 2015;Firth et al, 2014, Firth et al 2016Sella and Perkol-Finkel, 2015).…”

Rock armour for birds and their prey: ecological enhancement of coastal engineering

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