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Peyssonnelia rosa-marina Boudouresque & Denizot, 1973 (Fig. 9): an unsuspected Mediterranean rose garden It is perhaps one of the most abundant seaweeds in the Mediterranean Sea, since it thrives from the infralittoral to the widely extended and widespread coastal detritic bottoms, in the circalittoral, where it is often dominant. It is also a particularly elegant macrophyte, resembling a calcified rosebud, hence its name, Peyssonnelia rosa-marina. Like many red algae, this seaweed can live in rather low irradiance down to ca. 100 m depth; it is an important producer of carbonate sediment and is furthermore an ecosystem engineer that takes a significant part in the construction of the coralligenous beds so characteristic of the Mediterranean. Yet, it has long been confused with its sister species, Peyssonnelia polymorpha, until the 1970s. It was then very surprising to realize that such an abundant, conspicuous, and well-characterized species, both by its morphology and anatomy, had been overlooked for so long., Published as part of Boury-Esnault, Nicole, Bellan, Gerard, Bellan-Santini, Denise, Boudouresque, Charles-Francois, Chevaldonné, Pierre, Dias, Alrick, Faget, Daniel, Harmelin, Jean-Georges, Harmelin-Vivien, Mireille, Lejeusne, Christophe, Perez, Thierry, Vacelet, Jean & Verlaque, Marc, 2023, The Station Marine d'Endoume, Marseille: 150 years of natural history, pp. 213-252 in Zootaxa 5249 (2) on page 236, DOI: 10.11646/zootaxa.5249.2.3, http://zenodo.org/record/7687250, {"references":["Boudouresque, C. F. & Denizot, M. (1973) Recherches sur le genre Peyssonnelia (Rhodophycees). I. Peyssonnelia rosa-marina sp. nov. et Peyssonnelia bornetii sp. nov. Giornale Botanico Italiano, 107 (1), 17 - 27. https: // doi. org / 10.1016 / 0022 - 0981 (93) 90067 - X"]}

The Peyssonneliaceae represents the only family in the order Peyssonneliales, a clade of red encrusting algae distributed worldwide, including 136 species in eleven currently accepted genera. Delineation of genera in the Peyssonneliaceae has mostly been based on vegetative characteristics. Previous molecular phylogenies have shown that some traditionally circumscribed genera are not monophyletic and relationships among them are uncertain. We contribute to the knowledge of the evolutionary history of this clade, presenting a robust rbcL phylogeny that provides new insights on the origin and diversification of the Peyssonneliales. Based on a broad dataset and morphological analyses, we propose a revised taxonomic scheme for the Peyssonneliales resolved as monophyletic with well-supported main lineages. Our results show that Peyssonnelia is polyphyletic, and, therefore, we propose three new genera, Agissea, Olokunia, and Rhodowynnea to accommodate species currently assigned to Peyssonnelia, but distantly related to the clade with the type species of the genus. Additionally, barcoding techniques and analyzed criteria for specific delimitation supported the establishment of one new genus, Brasilophycus, and seven new species, from northeastern Brazil: Agissea amadoi, A. densissima, A. taberniforma, A. villatlantica, A. yemonjasagbae, Brasilophycus similis, and B. roseomarginatus. Our integrative taxonomic approach reveals underestimated diversity of Brazilian Peyssonneliales. Investment in broader sampling along the Brazilian coast and other tropical areas may reveal that its marine biodiversity can be expanded, enlightening our knowledge about this ecologically important group of red algae.

Detailed morphological studies and molecular analyses based on plastid-encoded rbcL gene sequences were undertaken on Peyssonnelia species, a poorly known genus from Korea. We report new records for the Korean coast, Peyssonnelia harveyana and P. rumoiana. Peyssonnelia harveyana is chiefly characterized by P. rubra-type anatomy, closely packed perithallial filaments in firm matrix, hypothallial filaments arranged in parallel rows, thalli with appressed margins, hypobasal calcification, and unicellular rhizoids. Peyssonnelia rumoiana is principally characterized by two vegetative features, hypothallial filaments arranged in a polyflabellate layer, and perithallial filaments arising from the whole upper surface of each hypothallial cell (Peyssonnelia rubra-type anatomy). Our rbcL analyses revealed that P. harveynana and P. rumoiana were placed within a clade of Peyssonnelia. We also propose the new combination, Sonderophycus cauliferus comb. nov., for previous Peyssonnelia caulifera. Phylogenetic analyses revealed that our S. cauliferus was placed within a clade of Sonderophycus.

The study aimed at contributing to the development of methods to assessing the effects of human disturbance on coralligenous reefs. The effects of the presence of a fish farm on coralligenous reefs were evaluated using the STAR (STAndaRdized coralligenous evaluation procedure) sampling procedure. An asymmetrical sampling design was used to compare the aquaculture site with two reference sites in areas unaffected by human pressure. The response of different ecological indices (ESCA, Ecological Status of Coralligenous Assemblages; ISLA, Integrated Sensitivity Level of coralligenous Assemblages; COARSE, COralligenous Assessment by Reef Scape Estimate) and descriptors (α-diversity, β-diversity and Sensitivity Level) of this kind of disturbance was compared. Results indicate that coralligenous reefs are vulnerable to aquaculture fish cages, and differences in the structure of coralligenous assemblages between the disturbed and the reference sites were mostly due to the decrease in β-diversity. On the contrary, no significant differences in the number of taxa/groups were highlighted. Encrusting Corallinales, erect Rhodophyta, Dictyotales, Fucales and Halimeda tuna were more abundant in reference sites than in disturbed site, while Peyssonnelia spp. and algal turfs had the opposite trend. Conversely, no significant differences between conditions were found in the abundance of sessile invertebrates. The study supports the suitability of the STAR approach to be employed in impact evaluation assessments, such as in monitoring programs. The present study is a first attempt to combine three different ecological indices (ESCA, ISLA and COARSE) within a unified approach, in order to assess the status of coralligenous reefs subjected to a moderate human-induced disturbance. The inconsistent response of the different indices highlights the advantage of applying different indices and descriptors to evaluate the variable human pressures on natural systems.

The geological, biological and geochemical features of a particular field of hydrothermal vents, discovered in the Panarea Volcanic Complex during a research survey carried out in 2015, are described for the first time. The site, located at 70-80 m depth off the South-western coast of the islet of Basiluzzo, was named Smoking Land for the presence of a large number of wide and high active chimneys and was characterized in terms of dissolved benthic fluxes, associated macrofauna and megafauna communities and preliminary mineralogy and geochemistry of chimney structures. On the whole field, a total of 39 chimneys, different in size and shape, were closely observed and described; 14 of them showed emission of low temperature hydrothermal fluids of marine origin characterized by acidified chemical conditions. The CTD and benthic chamber measurements highlighted that the Smoking Land is able to form a sea water bottom layer characterized by variable acidity and high DIC and trace elements concentrations; these characteristics weaken moving away from the chimney mouths. The SEM-EDS analysis of the collected solid samples revealed a chimney structure principally composed by amorphous and low crystalline Fe-oxyhydroxides of hydrothermal origins. The ROV explorations revealed a wide coverage of red algae (Peyssonnelia spp.) colonized by the green algae Flabiella petiolata and by suspension feeders, mainly sponges, but also bryozoans, and tubicolous polychaetes. Although novent-exclusive species were identified, the benthic communities found in association to the chimneys included more taxa than those observed in the surrounding no-vent rocky areas. These first findings evidence a submarine dynamic habitat where geological, chemical and biological processes are intimately connected, making the Smoking Land an important site in terms of marine heritage that should be safeguarded and protected.

The present study analysed the effect of three different benthic habitats, the maerl, Peyssonnelia red algal beds and sandy bottoms, on the condition of two nekto-benthic fish species: Serranus cabrilla and Trigloporus lastoviza. Sampling was conducted during the MEDITS 2010 and 2011 surveys around the Balearic Islands. The condition of the spawning females of both species was determined by using i) biochemical measurements of proteins and lipids in the muscle, liver and gonads, and ii) weight at length relationships based on eviscerated, liver, and gonad weights. Moreover, based on the total weight at length relationship, the mean somatic condition (SC) of the sexually inactive individuals of S. cabrilla and males of T. lastoviza was calculated. Lipid reserves were higher in the livers of S. cabrilla and T. lastoviza from the maerl beds. Additionally, S. cabrilla showed higher lipid reserves in the gonads both in the maerl and Peyssonnelia beds. The mean weights of the liver and gonads at a given individual length revealed the same pattern as the lipids, whereas the mean eviscerated weight was higher in the maerl beds but only for S. cabrilla. A positive correlation was detected between the SC and the biomass of the algal species characterizing the maerl beds for both S. cabrilla and T. lastoviza. The high habitat quality of the red algal beds off the Balearic Islands increased the condition of nekto-benthic fish. In oligotrophic areas, such as the archipelago, these “oases” could help fish to maintain healthy populations.

Ocean acidification (OA) increasingly threatens marine systems, and is especially harmful to calcifying organisms. One important question is whether OA will alter species interactions. Crustose coralline algae (CCA) provide space and chemical cues for larval settlement. CCA have shown strongly negative responses to OA in previous studies, including disruption of settlement cues to corals. In California, CCA provide cues for seven species of harvested, threatened, and endangered abalone. We exposed four common CCA genera and a crustose calcifying red algae, Peyssonnelia (collectively CCRA) from California to three pCO2 levels ranging from 419–2,013 µatm for four months. We then evaluated abalone (Haliotis rufescens) settlement under ambient conditions among the CCRA and non-algal controls that had been previously exposed to the pCO2 treatments. Abalone settlement and metamorphosis increased from 11% in the absence of CCRA to 45–69% when CCRA were present, with minor variation among CCRA genera. Though all CCRA genera reduced growth during exposure to increased pCO2, abalone settlement was unaffected by prior CCRA exposure to increased pCO2. Thus, we find no impacts of OA exposure history on CCRA provision of settlement cues. Additionally, there appears to be functional redundancy in genera of CCRA providing cues to abalone, which may further buffer OA effects.

The community structure of rhodoliths beds in the central Brazilian continental shelf was studied under the hypothesis that nongeniculate coralline algae are the major contributors of the individual rhodoliths. Samples were collected from five localities within a single area at 17–18 m depth. At each locality, rhodoliths were collected in 10 random quadrat samples along a 20-m transect. Our results show that dead cores of rhodoliths were significantly composed by nongeniculate coralline red algae rather than bryozoans, corals, or inorganic material. The live outer layers of the rhodoliths are composed mainly of 7 species of nongeniculate red coralline algae (Lithophyllum coralline, L. johansenii, L. depressum, L. stictaeformis, Neogoniolithon brassica-florida, Spongites fruticosus, and Lithothamnion muellerii) associated with other encrusting organisms such as bryozoans, sponges, corals, barnacles, and Peyssonnelia red algae. Significant differences were found in the proportion of Lithophyllum species in relation to other red coralline algae found in this study. Our results show that on the Brazilian continental shelf, the rhodolith-forming species are quite higher in size than in any other studied areas in the world. There was no difference in the proportion of live-to-dead rhodolith materials, suggesting an old bed deposit. Also, the amount of calcium carbonate material in the specimens is relevant to take in account in terms of the CO2 balance worldwide.

11 pages, 6 figures, 4 tables, 1 appendix, The bottom morphology, the surface sediments and the epibenthic community of two adjacent areas within the fishing ground traditionally known as Pesquera Rica (Balearic Islands) were characterized using multibeam echosounder, van Veen dredge and beam trawl. Red algae beds predominate in both areas, but one has been exploited by trawling since at least 90 years ago, whereas the presence of natural barriers prevents this fishing activity in the other one. Comparisons between the two areas showed a biomass reduction of 46.8 and 39.3% of dominant red algae taxonomic groups Peyssonneliaceae and Corallinophycidae, respectively, in the trawled area (TA). Similarly, both mean abundance and biomass of most groups of fauna were higher in the not trawled area (NTA). N biodiversity index showed higher mean values of algae species in NTA than in TA (7.0 and 4.9, respectively), whereas no differences were detected neither for sessile nor for mobile fauna. SIMPER analysis showed that large species of both sessile and mobile epibenthic fauna (e.g. the ascidia Polycarpa mamillaris and the echinoderm Spatangus purpureus, respectively) presented higher abundance and contribution to within area similarity in NTA than in TA. In coincidence, these are the most abundant epibenthic species in the commercial hauls from the Pesquera Rica. The relatively low fishing effort and the gears used, addressed to avoid large catches of algae allowing longer hauls, may explain the subsistence of red algae beds in the Balearic Islands trawl fishing grounds. However, the detrimental effects shown here claim for urgent management measures aiming to preserve these beds., Surveys at sea in 2009 and 2014 were carried out within the project DRAGONSAL (Caracterización del Ecosistema Bentónico de la Plataforma costera del area comprendida entre sa Dragonera, cap de ses Salines y Cala Figuera (Mallorca)), co-funded by the Instituto Español de Oceanografía and the Balearic Islands government . Analysis of the data has been done within the framework of the projects DRAGONSAL and LIFE-IP INTEMARES “Integrated, Innovative and Participatory Management for N2000 network in the Marine Environment” (LIFE15 IPE/ES/000012)

28 pages, 6 figures, 6 tables, supplementary material in https://doi.org/10.1007/s10531-011-0210-1, Menorca Channel (Balearic Islands, western Mediterranean) comprises 98,700 Ha of continental shelf. It has been proposed to include this area in the Natura 2000 network due to the wide range of species and habitats of high conservation value found here, such as Posidonia oceanica meadows and maërl and coralligenous beds. This study aimed to establish a scientific basis for managing and protecting the continental shelf bottoms in Menorca Channel. Sampling was carried out with side-scan sonar, beam trawls, box corers, a remote-operated vehicle and an underwater drop camera. The information collected was used to map the habitat distribution between 50 and 100 m depth, as well as make an inventory and describe the spatial patterns of both the specific and functional diversity. A total of 636 species was recorded in a mosaic of habitats in which Corallinacea calcareous algae and other soft red algae (Osmundaria volubilis and Peyssonnelia spp.) were the most abundant groups. Hotspots of specific and functional diversity were located in areas with high habitat heterogeneity and complexity. Protection of Menorca Channel should not only include the habitats and species in the European directives, but also the habitats that are not currently protected, such as O. volubilis and Peyssonnelia beds, due to their biogeographical and ecological interest and their contribution to the biodiversity of shelf bottoms in the Mediterranean Sea. © 2012 Springer Science+Business Media B.V., The study was financed by the Conselleria d’Agricultura i Pesca of the Government of the Balearic Islands within the Canal Project and in the framework of LIFE+ INDEMARES project: ‘‘Inventario y designación de la Red Natura 2000 en áreas marinas del Estado español’’. Sonography was carried out by Tecmarin 1990 SL and financed by the MarViva Foundation

The characteristics of Peyssonnelia capensis Montagne (Peyssonneliaceae, Rhodophyta) from Jeju Island were investigated in order to clarify the species entity and re-evaluate taxonomic position. The morphological variations of the Peyssonnelia capensis from Jeju Island were divided into two types, the thin thallus type and the thick thallus type. The thin thallus type is characterized by thin, soft, orbicular, slightly lobed thallus with entire to undulate margin, and compact rhizoids. The thick thallus type has thick and stiff thallus with sinuate margin and scattered rhizoids, and has more branches than the thin thallus type. The basal layer and the epithallium of thin thallus type are similar to those of thick thallus types in their structure. However, the hypothallial cells of the thick thallus type are longer than those of the thin thallus type. The erect filament of thick thallus type has more cells than those of the thin thallus type. Tetrasporangial nemathecia are distinctly protruded. Mature tetrasporangia of this species are divided cruciately into four spores as those of other Peyssonneliaceae. In addition to their morphological and anatomical distinctness between two types, the nucleotide sequence analyses of SSU and ITS2 region make no differences among populations from Jeju and other localities in Korea. Therefore these two morphological variation may not base on genetic variation.

Two highly colourful encrusting red algal species from deep and shallow coral reef habitats in Puerto Rico are reported. Peyssonnelia boergesenii Weber Bosse is characterized by its multicoloured appearance, polyflabellate arrangement of hypothallial cells and multicellular holdfasts. Peyssonnelia flavescens sp. nov. is variably bi- to tri-coloured, with the principal background colour bright yellow to tan. It forms large crusts, to 30 cm in diameter, which are variably thick, measuring 310–640 μm in thickness. The new species differs from other known Peyssonnelia species by cutting off elongate, 12–17 μm long, spermatangial initials that cut off seriate chains of spermatangia distally and by its production of very large tetrasporangia, to 170 μm long.

Photoinhibition of photosynthesis, defined as reversible decrease in the effective photosynthetic quantum yield, was measured in the Mediterranean red alga, Peyssonnelia squamata, using pulse amplitude modulation (PAM) chlorophyll fluorescence and oxygen production on site. This alga is adapted to very low fluence rates of solar radiation and is easily inhibited by exposure to excessive radiation. At high solar angles its photosynthetic capacity is impaired even in its natural habitat, in the protective shade of overhanging rocks. Oxygen production was maximal at 5 m depth and decreased to almost zero at the surface. When exposed at the surface oxygen production ceased within 16 min. The optimal photosynthetic quantum yield, defined as Fv/Fm, was about 0.45 in dark-adapted specimens. After 30 min of exposure to unattenuated solar radiation the (effective, Fv′/Fm′) quantum yield decreased to below 0.1. Removing solar UV (especially UV-B) significantly reduced photoinhibition: the quantum yield of a sample exposed under a UV-B cut-off filter was double that of a sample exposed to full solar radiation after 30 min exposure. Recovery from photoinhibition took several hours and was not complete after prolonged exposure (1.5 h) to direct solar radiation. The degree of photoinhibition depended on the depth at which the thalli were exposed. Recovery from photoinhibition was complete within 2 h except when the algae were exposed at the surface. When measured over the whole day, the effective photosynthetic quantum yield significantly decreased by about 25% from initially high values toward early afternoon and rose again towards evening. The data indicate that this alga is adapted to very low irradiances and is easily inhibited by excessive solar radiation; solar UV contributes substantially to the observed photoinhibition.

Coral reefs are very sensitive to environmental pollution. Coral reefs frequently get infected by various bacteria, fungi, marine algae and protozoa. The diseases include Bacterial Infections (BI), Fungal Infections (FI), Black Band Disease (BBD), Black Overgrowing Cyanophyta (BOC), Black Aggressive Band (BAB), Lethal Orange Disease (LOD), Skeleton Eroding Band (SED), PEYssonnelia (PEY), PNEophyllum (PNE) and White Syndromes (WS). Here in we have proposed a proposed model in which cold water soluble gelatin will be used to prepare Gelatin virus balls (GVB) and Liquid virus filled and sealed gelatin capsules (LVFSGC). GVB and LVFSGC will be prepared as per standard protocol in the form of paintballs and capsules. Above mentioned infecting agents of Coral reefs will be used as inoculum for production their production on the pilot scale. These produced infecting agents will be added with specific viruses of infecting agent (host-specific viruses). After the lysis of cell (naturally/artificially), lysate containg host-specific viruses will be used as infecting viruses to the Coral reef infecting agents. This lysate will be used for preparation of GVB and LVFSGC. These paintballs and capsules contain host-specific viruses can be made to release on a surface of sea water and dispersed on affected coral reefs zone naturally by Sea water current/waves. The dispersed viruses from GVB and LVFSGC will attach to their host. Ultimately, the diseasecausing agent may be killed and the coral reef infection will be removed from sea water without any harm to the environment. GVB and LVFSGC will be used for the release of viruses against disease-causing agents. The GVB and LVFSGC will systematically kill and save the coral reefs.

The study was conducted at the fringing reef of Sesoko Island (Okinawa, Japan), in the north-western Pacific. Artificial injuries were inflicted to the upper portions of colonies of the massive coral Porites lutea. The colonies were fixed to cement blocks and placed at two reef locations of different light intensity: one with moderate light (20–30% of incident photosynthetic active radiation, PAR0) and one with low light (2–5% PAR0). After six months of the treatment, all injuries were photographed. Analysis of photographs made under light and electron microscopes showed that the coral was able to recover from the injuries at both light variants. Under moderate light, some of the injuries completely healed and some injuries recovered partially. Under low light all injuries recovered partially. These partially recovered injuries were occupied by algae at dead portions of the injuries. In moderate light, coral polyps overgrew all algal settlers and were the winners in the competition for substratum. In low light, Peyssonnelia conchicola, Corallophila apiculata, Centroceras clavulatum, Anortichium tenue, and Lobophora variegata that colonized the injured areas overgrew coral polyps and were the winners in the competitive struggle for the substratum. It was shown that overgrowing is the main mechanism of coral–algal competition for substratum in light ranging from 2 to 30% PAR0. This mechanism of overgrowth of corals by algae, and the reverse, are discussed in detail.

Scorpaena notata is a small, sedentary scorpaenid species widely distributed in the Mediterranean and adjacent waters of the Atlantic. In the western Mediterranean it inhabits coastal continental shelf bottoms. In the Balearic Islands, these bottoms are characterised by the presence of the facies with red algae, including both Peyssonnelia and mäerl beds. These beds enhance the structural complexity, biodiversity and secondary production of the soft bottoms. Due to the oceanographic conditions of the Islands, the facies with red algae are especially rich in terms of biomass and algal coverage, and are widespread distributed between 40 and 90 m depth, where trawlers exploiting the continental shelf operate. The present work studies the biology of S. notata and its relationship with habitat characteristics. Special attention is focused on the aspects related to fish condition and growth as a tool to assess the importance of the facies with red algae for fish. The reproduction period of S. notata in the Balearic Islands occurs in summer and is accompanied by a decrease in hepatic condition, as it happens in the adjacent area off the Iberian Peninsula; however, in contrast with this adjacent area, this period is accompanied by a decrease in somatic condition and an increase in feeding potential, which suggests that these could be adaptations to the higher oligotrophy of the Archipelago. The standardised algal biomass (mostly Rhodophyceae) present in the bottoms positively affected the abundance, somatic condition and feeding potential of S. notata. Individuals inhabiting bottoms with the highest algal biomass showed faster growth than the entire population analysed together. Both, the structural complexity and the availability of preys in the facies with red algae are revealed as advantageous traits for the life history of fish. Taking into account the importance of individual health for the overall success of the population, the indexes studied here could be a useful tool for identifying high quality or essential fish habitats. Our results highlight the importance of the facies with red algae as oasis of high productivity where benthic fish can circumvent the general oligotrophic conditions of the Mediterranean, and the necessity of urgent management measures in order to protect them from human impacts., Sí

A deep-water community dominated by Halimeda tuna and Mesophyllum lichenoides is described from the rocky bottoms of the North-Western Mediterranean. Other sciaphilic algae such as Udotea petiolata, some Peyssonnelia species and Lithophyllum expansum are also abundant. Algal biomass ranges between 1200 and 2100 g dw m-2 while percentage coverage ranges from 180 to 400%. The variations observed in algal coverage adequately describe the seasonal pattern of the community, which is characterized by a high development of erect algae in summer months and a low development in winter. The species richness, as well as both species and pattern diversity reach a maximum in summer. Summer's maximum irradiances and the low irradiances received between November and February seem to account for the seasonal pattern described above. Community structure and environmental factors affecting the deep-water Halimeda populations from the North Western Mediterranean are compared with those found in other deep-water seaweed communities from the Mediterranean and other seas. Finally, the phytosociological affinities between these Halimeda populations and the deep-water Mediterranean associations previously described is assessed.Se describe una comunidad dominada por Halimeda tuna y Mesophyllum lichenoides en los fondos rocosos profundos del Mediterráneo Noroccidental. Dichas especies coexisten con Udotea petiolata, diversas especies de Peyssonnelia y Lithophyllum expansum, como especies más aparentes. La biomasa algal oscila entre 1200 y 2100 g ps m-2 mientras que el porcentaje de recubrimiento varía entre el 180 y el 400 %. Las variaciones encontradas en el recubrimiento algal describen adecuadamente el comportamiento estacional de la comunidad, el cual se caracteriza por un elevado desarrollo del estrato erecto durante el verano. La riqueza específica y la diversidad son también elevadas en verano. La mayor disponibilidad de luz veraniega parece explicar este comportamiento. La estructura de la comunidad y los factores ambientales a los que está sometida se comparan con los descritos en otras comunidades profundas del Mediterráneo y otros mares. Finalmente, se discute la afinidad de estas poblaciones de Halimeda con las distintas asociaciones descritas en la zona circalitoral del Mediterráneo Occidental.

In this paper the carbonate content and production, both at the species level and at the community level, is quantified in four areas of the Mallorca-Menorca shelf, northwestern Mediterranean Sea. Eight benthic communities are identified, each living at specific depth ranges and preferentially colonising either rocky or sedimented soft bottoms: (1) Photophilic algae, (2) Hemisciaphilic algae, (3) Coralligenous algal-dominated, (4) Coralligenous animal-dominated, (5) Caulerpa-Cymodocea meadows, (6) Posidonia oceanica meadows, (7) maërl and free-Peyssonelia beds, and (8) sandy bottom communities. Encrusting and maërl species of Corallinales and of the red algal genus Peyssonnelia and, to a lesser extent, the green alga Halimeda tuna, are the main carbonate producers. Most of the modern algal carbonate production in the Mallorca-Menorca shelf occurs at depths of less than 85–90 m, which is the lower limit of the coralligenous and maërl communities. Algal carbonate production in rocky areas is usually higher than that of soft bottoms, with the exception of the maërl beds in moderately deep waters (40–85 m). The highest algal carbonate production is found in coralligenous algal-dominated rocky bottoms (464.6 g m−2 year−1), photophilic algal communities (289.4 g m−2 year−1) and maërl beds (210 g m−2 year−1), while the lowest is displayed by seagrass meadows (60 to 70 g m−2 year−1) and sandy bottoms (0.5 g m−2 year−1). Nevertheless, the contribution of seagrass beds to benthic carbonate production in the Mallorca-Menorca shelf is outstanding due to the extent of the area occupied by these beds. The mean algal carbonate production rate over the upper 100 m water depth in the studied localities ranges from 90.60 to 123.89 g m−2 year−1, which correspond to the mostly sedimented Campos area and to the very rocky South Cabrera area, respectively. Overall mean carbonate production of the Mallorca-Menorca shelf is around 100 g CO3Ca m−2 year−1. These results may be viewed as a minimum estimate for total carbonate production on the Mallorca-Menorca shelf since they take into account only the phytobenthos.

Peyssonnelia bed distribution on continental shelf bottoms of the Balearic Islands (Western Mediterranean) ranges from 40 to 90 m depth. Different species of Peyssonnelia dominate these bottoms and, according to multivariate techniques, two main assemblages have been distinguished: the Peyssonnelia rosa-marina beds and the Peyssonnelia sp. beds, together with some transition samples between Peyssonnelia and maërl beds. Erect red algae are always abundant. Although average yearly irradiance reaching these beds is only 6.4-0.3% of subsurface irradiance, the species richness averages 45 species per sample (1600 cm2) and mean biomass is 2835 g dw. m-2. The high carbonate content of the living algae of these bottoms suggests that they are important contributors to the production of sediments in the Balearic continental shelf.

Peyssonnelia immersa sp. nov. is described from the British Isles and France. The species has been found intertidally on bedrock and stones and on mobile substrata in the sublittoral. It differs from all previously described species by possessing a unique combination of vegetative and reproductive characters; of particular note is the development of reproductive organs in extensive immersed sori. Terminal cruciate tetrasporangia, occasionally borne on thickened filaments, are surrounded by a complex stratified wall. Carpogonial branches, auxiliary cell branches and spermatangia are accessory in origin and develop among pigmented sterile filaments in the same sori. One or more gonimoblasts arise from the connecting filament after fusion with a series of auxiliary cells and the mature carposporophyte consists of simple or branched chains of 2–5 large carposporangia. In laboratory culture, tetraspores obtained from field material of P. immersa gave rise to crusts similar to field plants. Gametangia and immat...