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-The calcified thallus of Peyssonneliales: A, Peyssonnelia rosa-marina Boudouresque & Denizot rhodolith from the Mediterranean sea; B, Peyssonnelia sp. crustose growth-form from Mediterranean hard substrates; C, the calcified thallus of the aragonitic Peyssonnelia Decaisne and the hypobasal calcification (arrow); D, a non calcified Peyssonnelia with rhyzoid traces across the hypobasal calcification (arrow); E, a thick rhodolith-forming Polystrata Heydrich; F, detail of Polystrata thalli; G, close-up of calcified cell-walls of Polystrata. Note spherulitic crystals; C-G, SEM photographs. Scale bars: A, B, 2 cm; C, 50 µm; D, 40 µm; E, 250 µm; F, 20 µm; G, 2 µm.
Source publication
The most important groups of modern red calcareous algae are the Mg-calcite secreting Corallinales and Sporolithales, and the aragonitic Peyssonneliales and Nemaliales. They are common on the world's shelves and are vulnerable to the global warming and the lowering of pH of sea water, caused by the ongoing increase in anthropogenic CO2. Among them,...
Contexts in source publication
Context 1
... are a diverse group of platy, orbicu- lar algae with a variable but species-specific degree of calcification (Fig. 3). Some Peyssonneliales possess only scattered calcified cells and a hypobasal, extracel- lular calcification, while a few species of Peyssonnelia Decaisne such as P. rosa-marina Boudouresque & Denizot (Mediterranean, temperate) and some genera such as Polystrata Heydrich (warm temper- ate to tropical) are fully calcified (Fig. 3) ...
Context 2
... of calcification (Fig. 3). Some Peyssonneliales possess only scattered calcified cells and a hypobasal, extracel- lular calcification, while a few species of Peyssonnelia Decaisne such as P. rosa-marina Boudouresque & Denizot (Mediterranean, temperate) and some genera such as Polystrata Heydrich (warm temper- ate to tropical) are fully calcified (Fig. 3) (Denizot 1968;James et al. 1988;Basso 1990;Ballantine et al. 2000;Kato et al. 2006). The aragonite laid down within the cell wall is organized in layers of various thickness in which crystals are either spherulites or prisms oriented normal to the cell surface (Flajs 1977;James et al. 1988) (Fig. 3G). The hypobasal calcification ...
Context 3
... temper- ate to tropical) are fully calcified (Fig. 3) (Denizot 1968;James et al. 1988;Basso 1990;Ballantine et al. 2000;Kato et al. 2006). The aragonite laid down within the cell wall is organized in layers of various thickness in which crystals are either spherulites or prisms oriented normal to the cell surface (Flajs 1977;James et al. 1988) (Fig. 3G). The hypobasal calcification appears as an aragonite crust 80-200 µm thick, projecting downward from the lower thal- lus surface and crossed by rhizoids (Fig. 3C, D). The post-mortem fate of Peyssonneliales is largely dependent on their habit and growth-form (single crust on solid substrate; layered crusts, applanate or globose forming ...
Context 4
... within the cell wall is organized in layers of various thickness in which crystals are either spherulites or prisms oriented normal to the cell surface (Flajs 1977;James et al. 1988) (Fig. 3G). The hypobasal calcification appears as an aragonite crust 80-200 µm thick, projecting downward from the lower thal- lus surface and crossed by rhizoids (Fig. 3C, D). The post-mortem fate of Peyssonneliales is largely dependent on their habit and growth-form (single crust on solid substrate; layered crusts, applanate or globose forming rhodoliths on soft substrate, foliose frameworks). However, as most of them do not form thick encrustations, they easily undergo fragmenta- tion before final burial. ...
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... They contribute significantly to the diversity of these habitats by providing substrates for the settlement of various benthic invertebrates (Daume et al., 1999;Heyward and Negri, 1999;Tebben et al., 2015;Weiss and Martindale, 2017;Duran et al., 2018). Their fundamental ecological functions include carbonate production, both in terms of bioconstructions and loose sediment (Steneck, 1986;Adey, 1998;Nelson, 2009;Basso, 2012;Littler and Littler, 2013). Habitats dominated by RCA are economically and ecologically relevant (Coletti et al., 2017;Tuya et al., 2023) and have high sensitivity to the impacts of ocean warming and acidification (McCoy and Kamenos, 2015;Cornwall et al., 2019;Marchini et al., 2019). ...
... In the ecosystemic approach, studies point out the importance of the calcareous algae like founder species, driving habitat diversity to marine organisms (AMADO-FILHO et al., 2010;BASSO, 2012;COSTA et al., 2020). Due to chemical composition and suitable porosity for economic use, some economic applications for this kind of algae are animal and human supplementation, fertilizer, soil concealer, aquarium ornamentation and water treatment (KEMPF, 1980;DIAS, 2000;CAVALCANTI, 2007). ...
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... Little Cayman Island reef macroalgae had organic d 13 were found between d 13 C and tissue %N content within phyla, although there were differences among phyla suggesting %N levels were taxon-speci c. Ochrophytes had low organic %N simultaneous with 13 C enrichment, thus this phylum may be able to optimize HCO 3 use in low N reef environments, a trait that may contribute to its dominance on tropical reefs in addition to a lack of palatability to grazers (Hay, 1997 Rhodophytes exhibited the greatest depletion in 13 C (-4.1‰ ± 0.7‰) with the exception of Peyssonneliacea (red) and Galaxaura rugosa that were more enriched in 13 C, potentially affected by their primarily aragonite structure (Basso, 2012, Kerkar, 1994 and mechanism of calci cation. Aragonite rhodophytes have been shown to be more enriched in 13 C (Swart, 1983). ...
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... Peyssonnelia spp. and Ramicrusta spp.) contain much lower proportions of calcium carbonate than CCA 28,45 and therefore substantially lower contributions to carbonate budgets. CCA coverage may also be underreported in census-based surveys due to what the observer is able to visibly detect and measure 3,46 . ...
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... Little Cayman Island reef macroalgae had organic d 13 were found between d 13 C and tissue %N content within phyla, although there were differences among phyla suggesting %N levels were taxon-speci c. Ochrophytes had low organic %N simultaneous with 13 C enrichment, thus this phylum may be able to optimize HCO 3 use in low N reef environments, a trait that may contribute to its dominance on tropical reefs in addition to a lack of palatability to grazers (Hay, 1997 Rhodophytes exhibited the greatest depletion in 13 C (-4.1‰ ± 0.7‰) with the exception of Peyssonneliacea (red) and Galaxaura rugosa that were more enriched in 13 C, potentially affected by their primarily aragonite structure (Basso, 2012, Kerkar, 1994 and mechanism of calci cation. Aragonite rhodophytes have been shown to be more enriched in 13 C (Swart, 1983). ...
Tropical macroalgae serve importance ecological roles on coral reefs but can supplant corals in phase shifts as shown worldwide. Thus, it is important to understand their fundamental photophysiology and calcification mechanisms. We examined organic d ¹³ C, organic+inorganic d ¹⁵ N, inorganic CaCO 3 d ¹³ C and d ¹⁸ O, and organic %C, %N, C:N of abundant macroalgae on Little Cayman Island (LCI) reefs across irradiance gradients (5-2,000 mmol m ⁻² s ⁻¹ ). We hypothesized macroalgae utilize greater CO 2 in low light as carbon concentration mechanisms (CCMs) for HCO 3 ⁻ uptake have higher energetic costs. We proposed that calcification mechanisms are influenced by light and Ci-use strategy in addition to taxonomy. LCI macroalgae had organic d ¹³ C values (-12‰ to -25‰) indicative of CCMs and exhibited only 1-3‰ ¹³ C depletion in irradiances <5 mmol photons m ⁻² s ⁻¹ . Ochrophyte d ¹³ C values were enriched in ¹³ C at low nitrogen indicative of efficient CCMs. Macroalgae exhibited four clusters of thalli CaCO 3 d ¹³ C that were distinctly taxon-specific. Rhodophytes exhibited the most negative inorganic d ¹³ C and d ¹⁸ O values (-4.1‰ ± 0.7‰; -3.7‰ ± 0.4‰) an indication of high calcifying space pH and rapid calcification, potentially reliant on active ion transport. Relatively higher organic C fractionation when utilizing greater CO 2 for photosynthesis was reflected in depleted thalli carbonates in species/genus with positive d ¹³ C values. Increasing ocean CO 2 is not likely to enhance dominant LCI macroalgal photosynthesis as these reef macroalgae utilize CCMs across a broad range of irradiances; however, effects on calcification may be taxon specific based on the degree of biotic control elucidated in thalli carbonate isotopes.
... Important ecological functions and ecosystem services, up to now poorly assessed, are provided by CDB (Ballesteros, 1994;Barbera et al., 2003): (i) primary production (Basso, 2012;Basso et al., 2012); (ii) key habitat and trophic resources for invertebrates and fish; (iii) breeding, spawning and nursery grounds for fish and crustaceans including species of fishery interest, sometimes close to the deep limit of the Posidonia oceanica (L.) Delile meadow (e.g., Mullidae, Sparidae, Scorpaenidae, Palinurus elephas (Fabricius, 1787)) (Harmelin and Harmelin-Vivien, 1976;Verlaque, 1990;Kamenos et al., 2004;Soykan et al., 2010); (iv) fishing ground for trawlers and artisanal fishers (Stamouli et al., 2022); (v) long term carbon sink (Basso, 2012;Basso et al., 2012;Savini et al., 2012;Burrows et al., 2014;Watanabe et al., 2020); (vi) recycling of necromass (e.g., rhizomes and dead Posidonia oceanica leaves and drift macroalgae) ; (vii) exportation and settlement of larvae towards or from adjacent ecosystems (source-sink hypothesis; Levin and Dayton, 2009). In addition, CDB host numerous protected species and other species of conservation interest (Astruch et al., 2012;Joher et al., 2015;Astruch et al., 2019): e.g., the fan shell Pinna nobilis L. 1758 (annexe II Berne convention and UICN Red list: critically endangered), the red coralline alga Lithothamnion corallioides (Annexe 5 of the HD: species of interest with regulation of its exploitation), and several Fucales (Annexe 2 of the Barcelona convention), among others. ...
... Important ecological functions and ecosystem services, up to now poorly assessed, are provided by CDB (Ballesteros, 1994;Barbera et al., 2003): (i) primary production (Basso, 2012;Basso et al., 2012); (ii) key habitat and trophic resources for invertebrates and fish; (iii) breeding, spawning and nursery grounds for fish and crustaceans including species of fishery interest, sometimes close to the deep limit of the Posidonia oceanica (L.) Delile meadow (e.g., Mullidae, Sparidae, Scorpaenidae, Palinurus elephas (Fabricius, 1787)) (Harmelin and Harmelin-Vivien, 1976;Verlaque, 1990;Kamenos et al., 2004;Soykan et al., 2010); (iv) fishing ground for trawlers and artisanal fishers (Stamouli et al., 2022); (v) long term carbon sink (Basso, 2012;Basso et al., 2012;Savini et al., 2012;Burrows et al., 2014;Watanabe et al., 2020); (vi) recycling of necromass (e.g., rhizomes and dead Posidonia oceanica leaves and drift macroalgae) ; (vii) exportation and settlement of larvae towards or from adjacent ecosystems (source-sink hypothesis; Levin and Dayton, 2009). In addition, CDB host numerous protected species and other species of conservation interest (Astruch et al., 2012;Joher et al., 2015;Astruch et al., 2019): e.g., the fan shell Pinna nobilis L. 1758 (annexe II Berne convention and UICN Red list: critically endangered), the red coralline alga Lithothamnion corallioides (Annexe 5 of the HD: species of interest with regulation of its exploitation), and several Fucales (Annexe 2 of the Barcelona convention), among others. ...
... Aguilar et al. (2009) described rhodolith beds at 140-150 m depth around the Balearic Islands. Rhodoliths play an important role in the deep benthic fixing and sequestration of organic and inorganic carbon (Basso, 2012;Basso et al., 2016). The cover (mean percentage) of living rhodoliths appears to be the easiest descriptor to assess the structure of CDB, which conditions its functioning in both the upper and the deep zones (Bosellini and Ginsburg, 1971;Basso et al., 2016). ...
Introduction
Coastal detrital bottoms (CDB) are one of the most extensive habitats of the continental shelf worldwide, in the upper levels of the circalittoral zone. Hosting a diverse community structured by sediment grain size, trophic interactions and calcified organisms, CDB exhibit important ecological functions. In the Mediterranean Sea, CDB are constituted by recent elements partly provided by adjacent infralittoral and circalittoral ecosystems. Since the 2010s, the offshore extension of many Marine Protected Areas (MPAs) has resulted in the incorporation of vast areas of CDB, raising the issue of their management. The Marine Strategy Framework Directive (MSFD) has embraced the concept of an ecosystem-based approach involving taking into account the functioning of marine habitats and their related ecosystem services. The purpose of this paper is to propose an ecosystem-based quality index (EBQI) tested on CDB from the north-western Mediterranean Sea, focusing mainly on epibenthic assemblages.
Methods
The first step has been to define a conceptual model of the CDB functioning, including the main trophic compartments and their relative weighting, then to identify appropriate assessment methods and potential descriptors. Twenty-nine sites were sampled along the coast of Provence and French Riviera (Southern France). Study sites were chosen with a view to encompassing a wide range of hydrological conditions and human pressures.
Results
Very well-preserved sites were found in Provence in areas without trawling and terrigenous inputs, while impacted and low-ES sites were located in the vicinity of urbanized areas. The cover of rhodoliths characterizes the seascape and might be an indicator of the good ES of CDB and reduced human pressure. However, the absence of rhodoliths may also be induced by natural phenomena.
Discussion
The EBQI designed for CDB proved representative and useful for a functional assessment based on epibenthic assemblages. However, some descriptors have shown their limitations and should be further explored. We highlight here the priority of establishing an index corresponding to a societal demand (e.g., European Directives, Barcelona convention) as a basis for a broad and large-scale assessment, for practical reasons. We stress the need to better apprehend the role of the macro-infauna and to extend this index over a wider geographical scale.
