Lithology could affect benthic communities living below boulders

Abstract

Structure and diversity of sessile zoobenthic assemblages seem to be driven not only by chemical-physical constraints and biological interactions but also by substrate lithology and its surface features. Nevertheless, broadly distributed crustose epilithic corallines could mask the role of substrate on animal settling. To evaluate the direct influence of different rocky substrates, occurrence and coverage of several sessile species, growing on the dark (i.e. coralline-free) face of sublittoral limestone and granite boulders were compared in the Tavolara MPA (Mediterranean Sea). The analysis of photographic samples demonstrated significant differences in terms of species composition and coverage, according to lithology. Moreover, limestone boulders were widely bare, while the cover per cent was almost total on granite. The leading cause of observed patterns could be the different level of dissolution of the two types of rocks, due to their different mineral composition and textural characteristics. Limestone has previously been shown to have higher dissolution compared with granite, and consequently, a more unstable surface. Our results suggest that, in dark habitats, the absence of the crustose coralline layer allows more rock dissolution and consequent lower stability of the limestone compared with granite, which, in turn, reduces the zoobenthos colonization.

Surface Integrity Could Limit the Potential of Concrete as a Bio-Enhanced Material in the Marine Environment

“…5 B). A similar effect was registered in a recent study comparing sessile assemblages in natural limestone and granite boulders conducted in Sardinia, Mediterranean Sea (Canessa et al, 2020). In this case, limestone had a lower benthic coverage and different assemblage structure than granite, which could be explained by the lower surface stability of the former.…”

“…Substratum material influence marine assemblages, although it generally plays a secondary role in the successional patterns, composition, and diversity of benthic assemblages compared to other environmental variables, such as food and larvae abundance, hydrodynamic exposure, and substrate orientation and microtopography (Liversage et al, 2014;Coombes et al, 2015;Canessa et al, 2019Canessa et al, , 2020. Therefore, the compounding and interplay of multiple factors and environmental conditions hinder our ability to assess the role of material on marine assemblages, particularly in heterogeneous and patchy ecosystems such as rocky shores (Raffaelli and Hawkins, 2012).…”

“…As a result, most experimental studies on fouling communities in different substrates are based on early community development (e.g., Green et al, 2012;Sempere-Valverde et al, 2018, 2023b. In contrast, long-term (years to decades) studies are mostly survey-based and observational, often hampering the de-entanglement of compounding factors and covariables shaping biological assemblages (e.g., Bavestrello et al, 2000;Canessa et al, 2019Canessa et al, , 2020. Therefore, the high spatial variability in the compounding effects of substratum type and other environmental and ecological factors on benthic assemblages composition, combined with a lack of consolidated information across geographic scales (although see Aguilera et al, 2022), has limited our ability to identify common patterns and processes, leading to general recommendations and policies (Riera et al, 2018;Firth et al, 2020).…”

Basin-scale occurrence and distribution of mesophotic and upper bathyal red coral forests along the Italian coasts

“…Although red coral is found both on coralligenous accretions and primary rocks, it shows a preference for biogenic habitats. It is known that the presence of a coralline algal layer can positively or negatively drive the settling of many benthic species in both tropical and temperate environments (Harrington et al, 2004;Ritson-Williams et al, 2009, 2014Canessa et al, 2020). To date, experimental tests have shown that red coral larval settling did not show significant differences between Lithophyllum stictaeforme and bare rocks (Zelli et al, 2020); however, this approach should be applied to different crustose algae.…”

Dynamics of Stone Habitats in Coastal Waters of the Southwestern Baltic Sea (Hohwacht Bay)

“…In addition, information from shallow water environments (0-10 m water depth) is scarce since they are often influenced by strong waves impeding field surveys. Few studies concerning stone habitats in shallow waters exist, e.g., from the Mediterranean Sea in water depths between 15-20 m, where it was shown that instability of rocky substrates and their lithology can influence colonization [31]. Diverse studies on benthic community structure indicate a strong correlation between biodiversity and physical habitat structure [32][33][34][35], which can be assumed to be pronounced in the most dynamic shallow water environments.…”