Maerl Beds Research Articles

Sound production and associated behaviours of benthic invertebrates from a coastal habitat in the north-east Atlantic

Maerl beds are among the most endangered habitats in coastal temperate waters and a priority for conservation. Passive acoustics is a potential non-intrusive approach for surveying this fragile ecosystem with minor disturbances. Invertebrate sounds can be major contributors to natural coastal soundscapes but are not well studied. We conducted controlled tank-based experiments to identify sound-producing invertebrates inhabiting north-east Atlantic maerl beds and to characterise their sounds in terms of frequency features and source levels. We also determined which sound types are able to be detected above natural maerl ambient noise and suitable for in situ monitoring. Tank recording sessions of 20 abundant and potentially soniferous invertebrates from maerl beds revealed eight soniferous species and 15 different sound types. Two new sound-producing families were identified, Calyptraeidae and Majidae. Six sound types had properties consistent with detectability and identification for in situ acoustic studies: the feeding sound of sea urchins Echinus esculentus, Paracentrotus lividus and Psammechinus miliaris, snapping sound of the snapping shrimp Athanas nitescens, and feeding and other sounds of the spider crab Maja brachydactyla. Estimated detection distances ranged from a few metres for sea urchin feeding sounds up to about 40 m for A. nitescens snaps and spider crab feeding sounds. These invertebrates, particularly A. nitescens, probably make a substantial contribution to the maerl ambient noise. This invertebrate sound library sets a basis for in situ acoustic studies.

Coralline red algae (Corallinales sensu lato) in the Atlantic Iberian Peninsula: current state of knowledge.

Event Abstract Back to Event Coralline red algae (Corallinales sensu lato) in the Atlantic Iberian Peninsula: current state of knowledge. Juan Lugilde1*, Viviana Peña1 and Ignacio Bárbara1 1 University of La Coruña, Animal Biology, Vegetal Biology & Ecology, Spain Coralline red algae (Corallinales sensu lato) are characterized by having cells walls composed of calcium carbonate. They have a worldwide distribution, and occur from the intertidal to 250 m depth. Moreover, their ecological role as ecosystem engineers promote and increase local diversity such as the biogenic habitats known as maerl beds and the Mediterranean coralligenous. This group exhibits a great morphological diversity although it was traditionally grouped under two broad morphologies: (a) articulated, with fronds alternating calcified and decalcified segments and (b) non-articulated, with thallus entirely calcified. From the systematic point of view, Corallinales sensu lato currently encompasses three orders (Corallinales, Hapalidiales and Sporolithales) containing 35 genera and 600 species recorded worldwide. However, at regional scale, the diversity of coralline red algae is little known mainly because the difficulty in overcoming the morphological plasticity of external features. In order to assess the current state of knowledge of Corallinales in the Atlantic Iberian Peninsula, and compare it with adjacent Atlantic and Mediterranean areas, we reviewed information compiled from more than 250 publications, grey data and herbarium collections. Our results pointed out that the Atlantic Iberian coralline algae was scarcely studied, and it showed the lowest diversity. From 129 coralline taxa recorded, Macaronesia is the most species-rich region (71% of the total), followed by the Iberian Mediterranean (52%), the British Isles-Atlantic France (48)%, and the Atlantic Iberian Peninsula (37%). In our region, 17 species occurred commonly (> 50% of the coastline), particularly those corresponding to the genera Lithophyllum, Jania, Amphiroa, Mesophyllum and Phymatolithon. By contrast, other genera occasionally reported (Hydrolithon, Leptophytum, Lithothamnion and Pneophyllum) were probably overlooked and susceptible to appear by their presence in remaining adjacent regions. Regarding growth-form and habitat preferences of coralline red algae, our review indicated that the epilithic habit was dominant, followed by the epiphytic, epizoic and the unattached (maerl/rodoliths). Besides, sciaphilous taxa were more abundant than photophilous species. Lower intertidal and shallow subtidal habitats as well as semi-exposed shores or with current action harbor a high diversity of coralline algae, while rocky subtidal coasts are poor in species and probably overlooked. The present study confirms that the Atlantic Iberian coralline algae are scarcely studied, and further research is required, especially in those genera and habitats barely known. To overcome this gap of knowledge, we are conducting an extensive study of this group in Galicia (NW Iberian Peninsula). Apart from improving the knowledge about this group in terms of diversity and systematics updating, we aimed to develop an illustrated and descriptive flora with species descriptions, habitat, distribution information, and keys to facilitate their identification by the Atlantic Iberian scientific community. Keywords: Coralline algae, diversity, habitat, review, Atlantic Iberian, Galicia. Conference: XIX Iberian Symposium on Marine Biology Studies, Porto, Portugal, 5 Sep - 9 Sep, 2016. Presentation Type: Poster Presentation Topic: 1. ECOLOGY, BIODIVERSITY AND VULNERABLE ECOSYSTEMS Citation: Lugilde J, Peña V and Bárbara I (2016). Coralline red algae (Corallinales sensu lato) in the Atlantic Iberian Peninsula: current state of knowledge.. Front. Mar. Sci. Conference Abstract: XIX Iberian Symposium on Marine Biology Studies. doi: 10.3389/conf.FMARS.2016.05.00136 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 26 Apr 2016; Published Online: 03 Sep 2016. * Correspondence: PhD. Juan Lugilde, University of La Coruña, Animal Biology, Vegetal Biology & Ecology, La Coruña, La Coruña, 15001, Spain, juan.lugilde@udc.es Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Juan Lugilde Viviana Peña Ignacio Bárbara Google Juan Lugilde Viviana Peña Ignacio Bárbara Google Scholar Juan Lugilde Viviana Peña Ignacio Bárbara PubMed Juan Lugilde Viviana Peña Ignacio Bárbara Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Phymatolithon lusitanicumsp. nov. (Hapalidiales, Rhodophyta): The Third Most Abundant Maerl-Forming Species in the Atlantic Iberian Peninsula

Abstract Phymatolithon lusitanicum is a new maerl species described based on an integrative systematic approach including molecular (COI-5P, psbA) and morphological data obtained from recent collections, as well as comparison of type material from the morphologically and ecologically alike NE Atlantic species P. lamii and P. laevigatum. Molecular analyses including type material of P. lamii and P. laevigatum were congruent in delimiting P. lusitanicum as an independent lineage from these crustose species. The three species shared a common external morphology of multiporate asexual conceptacles, but P. lusitanicum has been detected only unattached as maerl while P. lamii and P. laevigatum are crustose. Phymatolithon lusitanicum is particularly abundant in subtidal maerl beds of the Atlantic Iberian Peninsula (Galicia and the Algarve); however it has also been detected northwards in Ireland intertidally and in Western Mediterranean Sea (Alboran Sea, Balearic Islands) down to 64 m. Phymatolithon lusitanicum ...

Benthic oxygen exchange in a live coralline algal bed and an adjacent sandy habitat: an eddy covariance study

Coralline algal (maerl) beds are widespread, slow-growing, structurally complex perennial habitats that support high biodiversity, yet are significantly understudied compared to seagrass beds or kelp forests. We present the first eddy covariance (EC) study on a live maerl bed, assessing the community benthic gross primary productivity (GPP), respiration (R), and net ecosys- tem metabolism (NEM) derived from diel EC time series collected during 5 seasonal measurement campaigns in temperate Loch Sween, Scotland. Measurements were also carried out at an adja- cent (~20 m distant) permeable sandy habitat. The O2 exchange rate was highly dynamic, driven by light availability and the ambient tidally-driven flow velocity. Linear relationships between the EC O2 fluxes and available light indicate that the benthic phototrophic communities were light - limited. Compensation irradiance (Ec) varied seasonally and was typically ~1.8-fold lower at the maerl bed compared to the sand. Substantial GPP was evident at both sites; however, the maerl bed and the sand habitat were net heterotrophic during each sampling campaign. Additional inputs of ~4 and ~7 mol m −2 yr −1 of carbon at the maerl bed and sand site, respectively, were required to sustain the benthic O2 demand. Thus, the 2 benthic habitats efficiently entrap organic carbon and are sinks of organic material in the coastal zone. Parallel deployment of 0.1 m 2 benthic chambers during nighttime revealed O2 uptake rates that varied by up to ~8-fold between repli- cate chambers (from −0.4 to −3.0 mmol O2 m −2 h −1 ; n = 4). However, despite extensive O2 flux vari- ability on meter horizontal scales, mean rates of O2 uptake as resolved in parallel by chambers and EC were typically within 20% of one another.

The first species ofSpiniphilineGosliner, 1988 (Gastropoda: Cephalaspidea) in the Atlantic Ocean, with notes on its systematic position

The Indo-Pacific genus Spiniphiline Gosliner, 1988 was erected for a rare species of Cephalaspidea characterized by an internal shell with spines. Spiniphiline kensleyi Gosliner, 1988 was until now the only known species. During the ‘Karubenthos’ expedition to the archipelago of Guadeloupe (Lesser Antilles, Caribbean Sea) coordinated by the Museum national d’Histoire naturelle, Paris, a small philinid was captured on a maerl bed. This specimen is here described as a new species of Spiniphiline—S. persei. Its occurrence in Guadeloupe is the first record of the genus in the Atlantic Ocean. The systematic position of Spiniphiline is discussed and evidence given for its inclusion in the family Philinidae s. s.

Environmental factors affecting maerl bed structure in Brittany (France)

This study used a large spatial scale approach in order to better quantify the relationships between maerl bed structure and a selection of potentially forcing physical factors. Data on maerl bed structure and morpho-sedimentary characteristics were obtained from recent oceanographic surveys using underwater video recording and grab sampling. Considering the difficulties in carrying out real-time monitoring of highly variable hydrodynamic and physicochemical factors, these were generated by three-dimensional numerical models with high spatial and temporal resolution. The BIOENV procedure indicated that variation in the percentage cover of thalli can best be explained (correlation = 0.76) by a combination of annual mean salinity, annual mean nitrate concentration and annual mean current velocity, while the variation in the proportion of living thalli can best be explained (correlation = 0.47) by a combination of depth and mud content. Linear relationships showed that the percentage cover of maerl thalli was positively correlated with nitrate concentration (R2 = 0.78, P < 0.01) and negatively correlated with salinity (R2 = 0.81, P < 0.01), suggesting a strong effect of estuarine discharge on maerl bed structure, and also negatively correlated with current velocity (R2 = 0.81, P < 0.01). When maerl beds were deeper than 10 m, the proportion of living thalli was always below 30% but when they were shallower than 10 m, it varied between 4 and 100%, and was negatively correlated with mud content (R2 = 0.53, P < 0.01). On the other hand, when mud content was below 10%, the proportion of living thalli showed a negative correlation with depth (R2 = 0.84, P < 0.01). This large spatial scale explanation of maerl bed heterogeneity provides a realistic physical characterization of these ecologically interesting benthic habitats and usable findings for their conservation and management.

Assessment of conservation value of Cap des Trois Fourches (Morocco) as a potential MPA in southern Mediterranean

The marine habitats surrounding Cap des Trois Fourches (Mediterranean coast of Morocco) was explored in the framework of the MedMPAnet Project. Ten different communities were identified in the studied area, among which it is remarkable the presence of some key conservational habitats: seagrass meadows, dark and semidark cave communities, maerl beds and corraligenous assemblages. All the data was included in a GIS program (Geographic Information System) to elaborate a cartographic map of marine communities and species distribution. All the scientific data obtained support the proposal of Cap des Trois Fourches as a marine protected area. We also provided a map of management, suggesting the stricter protection of the areas with higher conservational interest.

The seascape of demersal fish nursery areas in the North Mediterranean Sea, a first step towards the implementation of spatial planning for trawl fisheries.

The identification of nursery grounds and other essential fish habitats of exploited stocks is a key requirement for the development of spatial conservation planning aimed at reducing the adverse impact of fishing on the exploited populations and ecosystems. The reduction in juvenile mortality is particularly relevant in the Mediterranean and is considered as one of the main prerequisites for the future sustainability of trawl fisheries. The distribution of nursery areas of 11 important commercial species of demersal fish and shellfish was analysed in the European Union Mediterranean waters using time series of bottom trawl survey data with the aim of identifying the most persistent recruitment areas. A high interspecific spatial overlap between nursery areas was mainly found along the shelf break of many different sectors of the Northern Mediterranean indicating a high potential for the implementation of conservation measures. Overlap of the nursery grounds with existing spatial fisheries management measures and trawl fisheries restricted areas was also investigated. Spatial analyses revealed considerable variation depending on species and associated habitat/depth preferences with increased protection seen in coastal nurseries and minimal protection seen for deeper nurseries (e.g. Parapenaeus longirostris 6%). This is partly attributed to existing environmental policy instruments (e.g. Habitats Directive and Mediterranean Regulation EC 1967/2006) aiming at minimising impacts on coastal priority habitats such as seagrass, coralligenous and maerl beds. The new knowledge on the distribution and persistence of demersal nurseries provided in this study can support the application of spatial conservation measures, such as the designation of no-take Marine Protected Areas in EU Mediterranean waters and their inclusion in a conservation network. The establishment of no-take zones will be consistent with the objectives of the Common Fisheries Policy applying the ecosystem approach to fisheries management and with the requirements of the Marine Strategy Framework Directive to maintain or achieve seafloor integrity and good environmental status.

The ecosystem service value of living versus dead biogenic reef

Mixed maerl beds (corralline red algae) comprise dead thalli with varying amounts of live maerl fragments, but previously it was not known whether the presence of the live maerl increases the ecosystem service ‘habitat provision’ of the dead maerl for the associated epibenthos. A ‘flying array’ towed sled with high definition video was used to film transects of the epibenthos in dead maerl and mixed maerl beds in two locations to the north and south of the English Channel (Falmouth and Jersey). Mixed maerl beds supported greater number of taxa and abundance than dead beds in Falmouth, while in Jersey, mixed and dead beds supported similar number of taxa and dead beds had a greater abundance of epifauna. Scallops tended to be more abundant on mixed beds than dead beds. Tube worms were more abundant on mixed beds in Falmouth and dead beds in Jersey. An increasing percentage occurrence of live maerl thalli correlated with increasing number of taxa in Falmouth but not Jersey. It was concluded that while live thalli can increase the functional role of dead maerl beds for the epibenthos, this is dependent on location and response variable. As a result of this work, maerl habitat in SE Jersey has been protected from towed demersal fishing gear.

First record of &lt;em&gt;Caulerpa cylindracea&lt;/em&gt; (Caulerpaceae, Chlorophyta) in Andalusia (Southern Spain)

Altamirano, M., Andreakis, N., Souza-Egipsy, V., Zanolla, M. & De la Rosa, J. 2014. First record of Caulerpa cylindracea (Caulerpaceae, Chlorophyta) in Andalusia (Southern Spain). Anales Jard. Bot. Madrid 71(2): e007 Three different species of Caulerpa (Caulerpaceae, Chlorophyta) cooccur in the Mediterranean Sea: two of them are found at the centraleastern basin and are typically considered non aggressive components of the Lessepsian flora [(C. chemnitzia (Esper) J.V. Lamouroux and C. racemosa var. lamourouxii (Turner) Weber-van Bosse f. requienii (Montagne) Weber van Bosse)]; a third taxon, C. cylindracea Sonder has aggressively expanded its range since its first observation in 1990, and it is nowadays reported from nearly all the Mediterranean countries. We report a population of C. cylindracea from Almeria (Andalusia, Southern Iberian Peninsula) at −30 m depth as to be the westernmost record of the invasive variety on the Mediterranean European coast. Therefore, we made use of morphological description and molecular phylogenetics to provide a complete identification of this invasive seaweed in Southern Spain. Our findings are discussed in light of the composition of the receptor communities, such as maerl bed, edges of Posidonia oceanica (Linnaeus) Delile, and their ecology. Our results confirmed the suggested directionality of the invasive pathway to be westward to the Strait of Gibraltar, mainly supported by sea currents and vectors of anthropogenic origin.

DNA barcoding allows the accurate assessment of European maerl diversity: a Proof-of-Concept study

Two non-geniculate coralline red algae (Lithothamnion corallioides and Phymatolithon calcareum) are partially protected under the assumption that they are the main components of maerl beds in Atlantic Europe. However, what we know about the composition of maerl relies mainly on morphology-based identifications that are notoriously difficult due to a lack of diagnostic features, convergence, and widespread phenotypic plasticity. Now, this state of affairs can be improved with new alternatives that, unlike morphology, allow the unambiguous partition of a large number of rhodoliths into species regardless of their size, shape, and condition (fertile or sterile). Here, we report the first DNA barcoding assessment of the relative abundance of maerl-forming algae. The plastidial gene psbA was sequenced for 1140 rhodoliths from 15 maerl beds scattered along 2000 km from the British Isles to South Portugal; rhodoliths were randomly collected along linear transects to obtain quantitative estimates of species composition. Most (97%) of our collections belonged to three, rather than two, species that often appeared intermixed along a single transect. Lithothamnion corallioides and P. calcareum dominated in the British Isles and Brittany (NW France), but they were gradually replaced by Phymatolithon sp3 in Galicia (NW Spain) and became extremely rare in Algarve (S Portugal). Morphology (rhodolith size and shape, branch diameter, habit) varied considerably between and within beds but the three species converged to a remarkably similar habit when living in sympatry. Still, P. calcareum and L. corallioides seemed to perform best in Brittany while Phymatolithon sp3 produced the largest rhodoliths with thickest branches in Algarve. Altogether, our study shows that the replacement of species of maerl seen in northern latitudes continues to the south along the coasts of Iberia. It also serves as a proof-of-concept of the benefits of DNA barcoding for ecological and biogeographic research of these taxonomically challenging taxa.

An integrative systematic approach to species diversity and distribution in the genus Mesophyllum (Corallinales, Rhodophyta) in Atlantic and Mediterranean Europe

For the first time, a comprehensive assessment of Mesophyllum species diversity and their distribution in Atlantic Europe and the Mediterranean Sea is presented based on molecular (COI-5P, psbA) and morphological data. The distribution ranges were redefined for the four species collected in this study: M. alternans, M. expansum, M. macroblastum and M. sphaericum. Mesophyllum sphaericum, which was previously known only from a single maerl bed in Galicia (NW Spain), is reported from the Mediterranean Sea. The known range of M. expansum (Mediterranean and Macaronesia) was extended to the Atlantic Iberian Peninsula. The occurrence of M. alternans was confirmed along the Atlantic French coast south to Algarve (southern Portugal). Mesophyllum lichenoides was only recorded from the Atlantic, whereas M. macroblastum appears to be restricted to the Mediterranean Sea. A positive correlation was observed between maximum Sea Surface Temperature (SSTmax) and the depth at which M. expansum was collected, suggesting that this species may compensate for higher SST by growing in deeper habitats where the temperature is lower. The latter indicates that geographic shifts in the distribution of coastal species as a result of global warming can possibly be mitigated by changes in the depth profile at which these species occur. Mesophyllum expansum, an important builder of Mediterranean coralligenous habitats, may be a good target species to assess its response to climate change.

Spatial assessment of artisanal fisheries and their potential impact on the seabed: the Cap de Creus regional case study (northwestern Mediterranean Sea)

The northwestern Mediterranean region faces two contrasting realities: intensive fishing activity and a rising awareness among citizens of the need to protect ecologically important areas. In NE Spain, a large portion of the Cap de Creus area will be declared a Natura 2000 offshore site, establishing a large Marine Protected Area. This study examines the spatial distribution of artisanal fisheries and their potential impact on key vulnerable ecosystem components (KVECs) in the region. Data collection is based on a questionnaire-based survey in the absence of better records. An integrative map showing potential cumulative impact values for the Cap de Creus region was developed, including fishing gear pressure on selected KVECs. The most potentially impacted areas were found along the coast and on canyon margins. Results showed that different types of fishing gears converge, implying a higher impact on certain benthic communities and KVECs, with the greatest spatial coverage in coralligenous areas, Posidonia beds and maerl beds. When fishing log book and vessel monitoring system data are not available, the use of fishermen surveys linked to geographical information system tools can provide fundamental information for further implementation of effective measures for ecosystem-based management aimed at improving conservation of marine benthic ecosystems.

Paleoecology and dynamics of coralline dominated facies during a Pleistocene transgressive–regressive cycle (Capo Colonna marine terrace, Southern Italy)

The Upper Pleistocene deposits of Capo Colonna marine terrace (Calabria, southern Italy) contain a volumetrically important record of red algal facies developed during a transgressive–regressive cycle, well-expressed along a nearshore–offshore transect. This setting presents an ideal opportunity for the acquisition and interpretation of paleoecological information on coralline-dominated deposits and their response to relative sea level changes. The Capo Colonna deposits include rigid build-ups, rhodolith accumulations, and a maerl bed. The build-ups, identified as a fossil example of the present day Mediterranean coralligenous, are primarily formed by Mesophyllum alternans and, subordinately, by Lithophyllum stictaeformae, Titanoderma pustulatum and Lithothamnion sp., rarely alternating with encrusting bryozoans. Fruticose praline rhodoliths occur in a packstone bed, up to 160cm thick, 2 to 5cm in size and composed of Lithothamnion sp., Mesophyllum sp., and rare T. pustulatum. The maerl bed is about 60cm thick and laterally continuous for several tens of meters, and consists of interlocked unattached red algal branches of the species Lithothamnion corallioides, Phymatolithon sp., Lithophyllum sp., and Lithothamnion sp. The lateral distribution along the shelf profile of different red algal facies was influenced by transgressive–regressive trends. While praline rhodoliths and the maerl bed developed on mobile substrates mostly during the early highstand, respectively at intermediate and distal shelf sectors, the Mesophyllum-dominated coralligenous build-ups continued to grow for most of the regressive phase, progressively occupying all the preserved paleoshelf profile during sea level fall and resulting in a characteristic ecological vertical succession of crustose algae facies in the distal segment of the transect. Differences in substrate types determined variability in the coralligenous morphologies, with dome to mushroom shapes starting from discontinuous blocks of a basal conglomerate, and WE elongated platforms developing from a hardground and from rhodolith beds. Eventually, the development of red algal deposits became in itself the dominant control on substrate type. The red algae rich deposits of Capo Colonna marine terrace not only suggest a relationship between available substrate and geomorphological expression of the coralligenous build-ups, but also provide a framework for the paleoecological interpretation of other Neogene and Quaternary rhodalgal deposits from the Mediterranean region.

Development and multiplexing of the first microsatellite markers in a coralline red alga (Phymatolithon calcareum, Rhodophyta)

:Coralline red algae are important habitat builders in coastal waters around the world but their population genetics has been largely overlooked because of a lack of appropriate markers. Here, next generation sequencing was used to identify the first set of microsatellite loci ever developed for a coralline alga, Phymatolithon calcareum, a common builder of maerl beds, particularly in Europe. Eleven polymorphic microsatellite markers were identified, of which eight were particularly suitable for population and individual-based applications. In these, the number of alleles ranged from two to five, while expected heterozygosities varied from 0.143 to 0.803. Two multiplex polymerase chain reactions were designed and proved to successfully amplify these loci in specimens collected along the European Atlantic. The new set of markers will enable the study of population genetic diversity and connectivity patterns of these non-geniculate corallines that are especially relevant to propose conservation actions.

A multilocus species delimitation reveals a striking number of species of coralline algae forming Maerl in the OSPAR maritime area.

Maerl beds are sensitive biogenic habitats built by an accumulation of loose-lying, non-geniculate coralline algae. While these habitats are considered hot-spots of marine biodiversity, the number and distribution of maerl-forming species is uncertain because homoplasy and plasticity of morphological characters are common. As a result, species discrimination based on morphological features is notoriously challenging, making these coralline algae the ideal candidates for a DNA barcoding study. Here, mitochondrial (COI-5P DNA barcode fragment) and plastidial (psbA gene) sequence data were used in a two-step approach to delimit species in 224 collections of maerl sampled from Svalbard (78°96’N) to the Canary Islands (28°64’N) that represented 10 morphospecies from four genera and two families. First, the COI-5P dataset was analyzed with two methods based on distinct criteria (ABGD and GMYC) to delineate 16 primary species hypotheses (PSHs) arranged into four major lineages. Second, chloroplast (psbA) sequence data served to consolidate these PSHs into 13 secondary species hypotheses (SSHs) that showed biologically plausible ranges. Using several lines of evidence (e.g. morphological characters, known species distributions, sequences from type and topotype material), six SSHs were assigned to available species names that included the geographically widespread Phymatolithon calcareum, Lithothamnion corallioides, and L. glaciale; possible identities of other SSHs are discussed. Concordance between SSHs and morphospecies was minimal, highlighting the convenience of DNA barcoding for an accurate identification of maerl specimens. Our survey indicated that a majority of maerl forming species have small distribution ranges and revealed a gradual replacement of species with latitude.

Coralligenous and maërl habitats: predictive modelling to identify their spatial distributions across the Mediterranean Sea

Bioconstructions such as coralligenous outcrops and maerl beds are typical Mediterranean underwater seascapes. Fine-scale knowledge on the distribution of these sensitive habitats is crucial for their effective management and conservation. In the present study, a thorough review of existing spatial datasets showing the distribution of coralligenous and maerl habitats across the Mediterranean Sea was undertaken, highlighting current gaps in knowledge. Predictive modelling was then carried out, based on environmental predictors, to produce the first continuous maps of these two habitats across the entire basin. These predicted occurrence maps for coralligenous outcrops and maerl beds provide critical information about where the two habitats are most likely to occur. The collated occurrence data and derived distribution model outputs can help addressing the challenge of developing basin-wide spatial plans and to guide cost-effective future surveys and monitoring efforts towards areas that are presently poorly-sampled.

The diversity of seaweeds on maerl in the NE Atlantic

Maerl beds worldwide face habitat destruction (e.g. from dredging, fishing gear and fish farms), the combined pressures of ocean warming and acidification, and the spread of invasive species. Maerl beds have high conservation status in European legislation, yet their associated flora is poorly known. Here, we evaluate the known macroalgal diversity of NE Atlantic maerl beds from Svalbard to Portugal. Maerl beds occur from the low intertidal down to 51 m in the clearest waters. To date, 349 macroalgal species have been recorded on maerl in the NE Atlantic (67 % are Rhodophyta), a remarkable 30 % of the total seaweed diversity in this region. Eleven non-native species have been recorded on Atlantic European maerl beds, the most widely distributed being phases of Bonnemaisonia hamifera (“Trailliella intricata”), Asparagopsis armata (“Falkenbergia rufolanosa”), Antithamnionella spirographidis and Heterosiphonia japonica. The flora of maerl beds off Iceland and Norway is poorly known, but maerl beds off Britain, Ireland, France and Spain have been surveyed extensively and support several species that are maerl specialists (i.e. Cruoria cruoriaeformis, Cladophora rhodolithicola, Gelidiella calcicola). Our observations of G. calcicola and Gelidium maggsiae are new records for Portugal. Maerl beds in the Algarve have many of the same macroalgal species as Mediterranean maerl beds, but they are not as floristically diverse as those in Galicia because they are confined to deeper water. Our census provides a baseline that can be used to assess changes to these habitats over the coming years.

Detection of Gametophytes in the Maerl-Forming SpeciesPhymatolithon calcareum(Melobesioideae, Corallinales) Assessed by DNA Barcoding

Fertile gametangial plants of Phymatolithon calcareum, which are seldom reported in the Atlantic European coasts, were collected as encrusting, epilithic plants in a subtidal maerl bed in Brittany (France). Based on their morphological features, the plants were identified as P. calcareum. This identification was further confirmed by DNA barcodes using as a reference COI-5P sequences obtained from the neotype together with recent collections from the Atlantic European maerl beds. The reproductive structures were empty but they were regarded as mature female conceptacles. Compared to the two previous records of gametangial plants of P. calcareum for the Atlantic European waters, the uniporate conceptacles observed in this study are larger, and were collected at a different time of the year. To our knowledge, this is the first time that the occurrence of gametangial plants of P. calcareum is corroborated with molecular tools (DNA barcodes).

Non-coralline crustose algae associated with maerl beds in Portugal: a reappraisal of their diversity in the Atlantic Iberian beds

Abstract In recent years (2007–2009), the distribution and associated flora of maerl beds in southern Portugal (Algarve) were investigated by dredging and SCUBA diving (12–30 m depth). The present work provides the first data on the non-coralline crustose flora associated with maerl beds in Portugal. Peyssonnelia bornetii is a new record for Atlantic European coasts, and new records for Portugal are “Rhododiscus pulcherrimus” (sporophyte phase of Atractophora hypnoides), Contarinia peyssonneliaeformis, “Cruoria rosea” (sporophyte phase of Halarachnion ligulatum), Peyssonnelia armorica, and “Aglaozonia chilosa” (sporophyte phase of Cutleria chilosa). In addition, the records of three other species (Hildenbrandia crouaniorum, Peyssonnelia dubyi, and Peyssonnelia harveyana) completed the distribution gap between the North Iberian Peninsula and the Macaronesian region. The female and carposporangial structures of C. peyssonneliaeformis and P. bornetii are described for the first time. The diversity and species composition observed are compared with previous studies from maerl beds in the northwestern Iberian Peninsula (Galicia) and neighboring areas in the Atlantic Ocean and Mediterranean Sea. In order to facilitate and promote further studies of the crustose flora of subtidal habitats along European coasts, an identification key is provided for the 26 crustose taxa associated with maerl and gravel beds of the Atlantic coast of the Iberian Peninsula.