Complexity pervades biological systems at any scale: from microbes to higher organisms, from individuals to populations and from communities to ecosystems. Biodiversity and community structure are strongly influenced by the complexity of those relationships, in addition to the interplaying between multiple environmental conditions. On the other hand, complexity in microcommunities has not been solved yet. For instance, the role of substrates in shaping the diversity and structure of biofouling communities is virtually unexplored Benthic microalgae living in shallow coastal regions give a reliable contribution to the dynamics of the aquatic ecosystems, in terms of primary production, oxygenic activity, and trophic processes (Mac Intyre et al., 1996). Among benthic microalgae diatoms are reported to colonize sponges (Cerrano et al., 2004a, b), hydrozoans (Bavestrello et al., 2008; Romagnoli et al., 2006), bryozoans (Wuchter et al., 2003), crustaceans (Ikeda, 1977), bivalves (Round, 1981), and vertebrates (Round, 1981; Round et al., 1990), with a high degree of specificity for some hosts. The species composition of epibenthic diatom communities seem to be influenced by the nature of substrate and by their biogeographic distribution. On the other hand, these diatoms communities appear to be composed by a limited number of genera, that can be considered fully adapted to the epibenthic lifestyle. Moreover, ecological studies on epibenthic diatom communities based on a rigorous taxonomic approach are very rare due to the small size of such organisms. Indeed, most of the species have average size less than 20 microns with taxonomic characters not resolvable in light microscopy, so the scanning electron microscopy (SEM) results the only possible approach for a correct quantitative analysis of such floristic communities. Our study, entirely based on scanning electron microscopy (SEM) investigation of diatom communities in undisturbed conditions gave us the first data on the hidden biodiversity of diatom assemblages associated to macrophytes and different invertebrates including sea urchins, gastropods, crustaceans and bivalves along Omani coasts in terms of functional classes and species composition. Preliminary results demostrated that all invertebrates and macroalgae collected along the Batinah coastal areas of Oman hosted benthic diatom communities which in both the case constituted the major element of their epibenthic microalgal flora. Significant differences in terms of cell density, specie composition and communities structure were observed between the diatom communities of invertebrates and macroalgae which appear quite similar within sampling locations analyzed . More in detail, cell densities of macroalgae diatom communities resulted more than one ten times higher than those of invertebrates with mean values approximately ranging 1000-4000 cell/mm2 in the former versus 100 - 400 cell/mm2 in the latter. Noteworthy is that the specie composition of macroalgae diatom communities was characterized by the complete dominance of adnate genus Cocconeis (represented by four species). Claim and gastropod diatom communities seem to be dominated still by the adnate genera Amphora and Cocconeis with a higher contribution of the former in claim and of the latter in gastropods respectively. Corals and sea urchins seem able to actively contrast diatom settlement by means of self-excreted mucilaginous matrices that trap the individual cells. Nevertheless, some genera of motile (Mastogloia, Navicula, Diploneis Nitzschia and Pleurosigma) and erect (Achnanthes, Licmophora) diatoms manage to colonize this complex and dynamic habitat.

First survey of epibenthic diatom communities on marine invertebrates from Omani coasts

M. De Stefano
Writing – Original Draft Preparation
;
2019

Abstract

Complexity pervades biological systems at any scale: from microbes to higher organisms, from individuals to populations and from communities to ecosystems. Biodiversity and community structure are strongly influenced by the complexity of those relationships, in addition to the interplaying between multiple environmental conditions. On the other hand, complexity in microcommunities has not been solved yet. For instance, the role of substrates in shaping the diversity and structure of biofouling communities is virtually unexplored Benthic microalgae living in shallow coastal regions give a reliable contribution to the dynamics of the aquatic ecosystems, in terms of primary production, oxygenic activity, and trophic processes (Mac Intyre et al., 1996). Among benthic microalgae diatoms are reported to colonize sponges (Cerrano et al., 2004a, b), hydrozoans (Bavestrello et al., 2008; Romagnoli et al., 2006), bryozoans (Wuchter et al., 2003), crustaceans (Ikeda, 1977), bivalves (Round, 1981), and vertebrates (Round, 1981; Round et al., 1990), with a high degree of specificity for some hosts. The species composition of epibenthic diatom communities seem to be influenced by the nature of substrate and by their biogeographic distribution. On the other hand, these diatoms communities appear to be composed by a limited number of genera, that can be considered fully adapted to the epibenthic lifestyle. Moreover, ecological studies on epibenthic diatom communities based on a rigorous taxonomic approach are very rare due to the small size of such organisms. Indeed, most of the species have average size less than 20 microns with taxonomic characters not resolvable in light microscopy, so the scanning electron microscopy (SEM) results the only possible approach for a correct quantitative analysis of such floristic communities. Our study, entirely based on scanning electron microscopy (SEM) investigation of diatom communities in undisturbed conditions gave us the first data on the hidden biodiversity of diatom assemblages associated to macrophytes and different invertebrates including sea urchins, gastropods, crustaceans and bivalves along Omani coasts in terms of functional classes and species composition. Preliminary results demostrated that all invertebrates and macroalgae collected along the Batinah coastal areas of Oman hosted benthic diatom communities which in both the case constituted the major element of their epibenthic microalgal flora. Significant differences in terms of cell density, specie composition and communities structure were observed between the diatom communities of invertebrates and macroalgae which appear quite similar within sampling locations analyzed . More in detail, cell densities of macroalgae diatom communities resulted more than one ten times higher than those of invertebrates with mean values approximately ranging 1000-4000 cell/mm2 in the former versus 100 - 400 cell/mm2 in the latter. Noteworthy is that the specie composition of macroalgae diatom communities was characterized by the complete dominance of adnate genus Cocconeis (represented by four species). Claim and gastropod diatom communities seem to be dominated still by the adnate genera Amphora and Cocconeis with a higher contribution of the former in claim and of the latter in gastropods respectively. Corals and sea urchins seem able to actively contrast diatom settlement by means of self-excreted mucilaginous matrices that trap the individual cells. Nevertheless, some genera of motile (Mastogloia, Navicula, Diploneis Nitzschia and Pleurosigma) and erect (Achnanthes, Licmophora) diatoms manage to colonize this complex and dynamic habitat.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11591/424565
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