Modified habitats change ecological processes affecting a non-indigenous epibiont

Abstract

Urbanisation of coastal habitats, particularly the increased numbers of pier-pilings, jetties and seawalls along shorelines, affects natural systems. Epibiota on secondary substrata (kelps, Ecklonia radiata) in man-made structures differ from those in natural habitats, but they have received considerably less attention. To understand the consequences of changes in the structure of these assemblages, it is therefore necessary to determine which ecological processes are being affected and the factors influencing them. In Sydney Harbour, kelps on pier-pilings supported greater covers of bryozoans, particularly of the non-indigenous species Membranipora membranacea, than found on natural reefs. Experimental transplants of kelps without epibiota from reefs to pilings showed that recruitment and growth of colonies of M. membranacea were much greater on pilings than on reefs. Patterns of distribution and abundance of this epibiotic bryo zoan are determined by a combination of these processes and probably influenced by differences in abiotic and biotic characteristics between habitats. Understanding how these components of habitats affect ecological processes is necessary to allow sensible prediction of the effects of modifying habitats on the ecology of organisms.

Coastal urbanisation affects microbial communities on a dominant marine holobiont

“…For instance, greater shading on pilings may directly affect kelp microbiota, which, in turn, may make the algae more susceptible to the colonisation of fouling organisms. 39 The dominant epibiont on kelp on pilings in Sydney Harbour is the non-indigenous encrusting bryozoan Membranipora membranacea 40 which recruits in much higher numbers and grows up to four times faster in this habitat than in natural reefs, and can cover over 50% of the kelp thallus. 23 , 39 Several studies have shown that larval settlement of bryozoans can be influenced by the microbiome on the surfaces onto which they settle and colonise, 30 , 56 and may thus be the mechanism behind the higher abundance of M. membranacea on kelp on pilings.…”

“… 39 The dominant epibiont on kelp on pilings in Sydney Harbour is the non-indigenous encrusting bryozoan Membranipora membranacea 40 which recruits in much higher numbers and grows up to four times faster in this habitat than in natural reefs, and can cover over 50% of the kelp thallus. 23 , 39 Several studies have shown that larval settlement of bryozoans can be influenced by the microbiome on the surfaces onto which they settle and colonise, 30 , 56 and may thus be the mechanism behind the higher abundance of M. membranacea on kelp on pilings. 23 , 39 Greater fouling can eventually lead to lower photosynthetic capacity and increased tissue loss due to increased drag, fragmentation and consumption by predators that target the fouling organisms, indirectly damaging the fouled kelp tissue.…”

“…However, kelp are negatively affected by such structures, where they experience lower light availabily and greater fouling. 24 , 39 – 41 …”

Corridors for aliens but not for natives: effects of marine urban sprawl at a regional scale

“…Indeed, ecological considerations in the design of hard marine infrastructures tend to focus on construction materials, surface texture and habitat complexity as engineering options to enhance the ecological value of these artificial substrata (Burcharth et al, 2007;Martins et al, 2010;Chapman & Underwood, 2011;Firth et al, 2013Firth et al, , 2014. The type and intensity of biotic interactions can also differ between artificial and natural habitats (Ivesa et al, 2010;Marzinelli et al, 2011Marzinelli et al, , 2012. For example, experiments in the study region have shown that levels of predation particularly large compared with those observed in natural reefs can limit the growth of native canopy forming algae on many marine infrastructure (Perkol-Finkel et al, 2012).…”

Living on the Edge: Variation in the Abundance and Demography of a Kelp Forest Epibiont

“…Several studies have documented temperature-mediated outbreaks of Membranipora in the North Atlantic, where, as an invasive species, it has led to defoliation of kelps [33][34][35]. A few studies have explored variation in Membranipora growth rates in modified habitats [42,43] and understory kelp [30]. One study looked at spatial variation in the recruitment of Membranipora in giant kelp forests [1].…”