Corallina Elongata Research Articles

Using catenas for GIS-based mapping of NW Mediterranean littoral habitats

Studies aimed at describing habitats and mapping their distributions are pivotal to implementing management plans and to effectively guide conservation measures. We developed a novel approach of data collection and entry (CAT-LIT) to establish a detailed cartography of the littoral habitats found along the Catalan coast (Spain). Field data were recorded using coded, two-digit hierarchical lists (e.g. Aa, Ab, etc.) of horizons found at each point along the coast, called catenas. The horizons were either dominated by species (on the rocky bottoms) or sediment types (on the beaches) and corresponded to LPRE, EUNIS and CORINE habitats. Catenas were transferred into a database and calculations about the extent of bottom types, habitats, and catenas themselves along the coast were carried out with GIS tools. In addition, habitat link richness was calculated and represented using network analysis programs. The application of CAT-LIT to the Catalan coast showed that the habitats dominated by the lichen Verrucaria amphibia and the flattened barnacle Euraphia depressa and those dominated by the barnacle Chthamalus spp. were almost ubiquitous. Those dominated by the red alga Corallina elongata, the mussel Mytilus galloprovincialis and the red alga Rissoella verruculosa were also common. Because of the frequency of their connections, those habitats formed a huge hub of links in the networks. By using catenas, the habitats can be viewed using GIS based programs keeping the catena as the main informational and ecological unit. The catenas allow maximum compactness when vertically distributed habitats are to be shown on a 2D map. The complete cartography and dataset on the spatial distribution of the littoral habitats from Catalonia is valuable for coastal management and conservation to study changes in the habitat distribution and relate such changes to anthropogenic pressures. Furthermore, the CAT-LIT can be easily adapted to shores of other seas and oceans to obtain accurate cartographies of the spatially-reduced and highly vulnerable littoral habitats.

Long-term changes in sublittoral macroalgal assemblages related to water quality improvement

Abstract Sampling of sublittoral macroalgal assemblages was carried out in 1982 and 1999 along the coast of Catalonia (Northwestern Mediterranean, Spain) in order to study long-term changes in species composition. Ordination analysis revealed significant differences in species composition and abundance between the two study periods. The number of stations with indicators of eutrophication, such as species of Chaetomorpha, Cladophora, and Ulva, decreased from 1982 to 1999. This decrease was not balanced by an increase in species typical of pristine environments, such as large perennial brown algae (in particular, Cystoseira mediterranea), but rather by an increase of stress-resistant species such as Corallina elongata. The observed shifts seem to be driven by the decrease in nutrient loadings in the water column, resulting from the progressive implementation of sewage treatment management in the study region since the mid-1970s.

Responses of cyclic phosphorylation of MAPK-like proteins in intertidal macroalgae after environmental stress

The presence and activation of MAPK-like proteins in intertidal macroalgae is described in the current study. Two MAPK-like proteins of 40 and 42kDa in size similar to p38 and JNK, of mammalian cells have been identified in six representative species of intertidal macroalgae from the Strait of Gibraltar (Southern Spain), namely in the chlorophytes Ulva rigida and Chaetomorpha aerea, the rhodophytes Corallina elongata and Jania rubens, and the phaeophytes Dictyota dichotoma and Dilophus spiralis. Phosphorylation of MAPK-like proteins was studied during semi-tidal cycles. Analysis of p38-like and JNK-like MAPKs in macroalgae protein extracts was carried out by using specific antibodies against the phosphorylated forms of both MAPKs. Protein blot analysis of samples collected from 2009 to 2011 in natural growing sites on days when either low or high tide occurred at midday, indicated that MAPK-like proteins in all species were highly phosphorylated in response to desiccation imposed by low tide or high irradiance. Phosphorylation of p38-like MAPK always preceded that of JNK-like MAPK. In addition, phosphorylation of MAPKs was fastest in rhodophytes, followed by chlorophytes and then finally phaeophytes. In the first group, phosphorylation was mostly dependent on desiccation, whereas both high irradiance and desiccation were responsible for p38-like and JNK-like phosphorylation in chlorophytes. In phaeophytes, high irradiance was mostly responsible for MAPK-like activation.

Effects of ocean acidification and diet on thickness and carbonate elemental composition of the test of juvenile sea urchins

Continuous anthropogenic CO2 emissions to the atmosphere and uptake by the oceans will cause a reduction of seawater pH and saturation state (Ω) of CaCO3 minerals from which marine calcifiers build their shells and skeletons. Sea urchins use the most soluble form of calcium carbonate, high-magnesium calcite, to build their skeleton, spines and grazing apparatus. In order to highlight the effects of increased pCO2 on the test thickness and carbonate elemental composition of juvenile sea urchins and potential differences in their responses linked to the diet, we performed a laboratory experiment on juvenile Paracentrotus lividus, grazing on calcifying (Corallina elongata) and non-calcifying (Cystoseira amentacea, Dictyota dichotoma) macroalgae, under different pH (corresponding to pCO2 values of 390, 550, 750 and 1000 μatm). Results highlighted the importance of the diet in determining sea urchin size irrespectively of the pCO2 level, and the relevance of macroalgal diet in modulating urchin Mg/Ca ratio. The present study provides relevant clues both in terms of the mechanism of mineral incorporation and in terms of bottom-up processes (algal diet) affecting top-down ones (fish predation) in rocky subtidal communities.

Physiological responses of three temperate coralline algae from contrasting habitats to near-future ocean acidification

Coralline algae are major calcifiers of significant ecological importance in marine habitats but are among the most sensitive calcifying organisms to ocean acidification. The elevated pCO2 effects were examined in three coralline algal species living in contrasting habitats from intertidal to subtidal zones on the north-western coast of Brittany, France: (i) Corallina elongata, a branched alga found in tidal rock pools, (ii) Lithophyllum incrustans, a crustose coralline alga from the low intertidal zone, and (iii) Lithothamnion corallioides (maerl), a free-living form inhabiting the subtidal zone. Metabolic rates were assessed on specimens grown for one month at varying pCO2: 380 (current pCO2), 550, 750 and 1000μatm (elevated pCO2). There was no pCO2 effect on gross production in C. elongata and L. incrustans but L. incrustans respiration strongly increased with elevated pCO2. L. corallioides gross production slightly increased at 1000μatm, while respiration remained unaffected. Calcification rates decreased with pCO2 in L. incrustans (both in the light and dark) and L. corallioides (only in the light), while C. elongata calcification was unaffected. This was consistent with the lower skeletal mMg/Ca ratio of C. elongata (0.17) relative to the two other species (0.20). L. incrustans had a higher occurrence of bleaching that increased with increasing pCO2. pCO2 could indirectly impact this coralline species physiology making them more sensitive to other stresses such as diseases or pathogens. These results underlined that the physiological response of coralline algae to near-future ocean acidification is species-specific and that species experiencing naturally strong pH variations were not necessarily more resistant to elevated pCO2 than species from more stable environment.

Cascading Effects of Ocean Acidification in a Rocky Subtidal Community

Temperate marine rocky habitats may be alternatively characterized by well vegetated macroalgal assemblages or barren grounds, as a consequence of direct and indirect human impacts (e.g. overfishing) and grazing pressure by herbivorous organisms. In future scenarios of ocean acidification, calcifying organisms are expected to be less competitive: among these two key elements of the rocky subtidal food web, coralline algae and sea urchins. In order to highlight how the effects of increased pCO2 on individual calcifying species will be exacerbated by interactions with other trophic levels, we performed an experiment simultaneously testing ocean acidification effects on primary producers (calcifying and non-calcifying algae) and their grazers (sea urchins). Artificial communities, composed by juveniles of the sea urchin Paracentrotus lividus and calcifying (Corallina elongata) and non-calcifying (Cystoseira amentacea var stricta, Dictyota dichotoma) macroalgae, were subjected to pCO2 levels of 390, 550, 750 and 1000 µatm in the laboratory. Our study highlighted a direct pCO2 effect on coralline algae and on sea urchin defense from predation (test robustness). There was no direct effect on the non-calcifying macroalgae. More interestingly, we highlighted diet-mediated effects on test robustness and on the Aristotle's lantern size. In a future scenario of ocean acidification a decrease of sea urchins' density is expected, due to lower defense from predation, as a direct consequence of pH decrease, and to a reduced availability of calcifying macroalgae, important component of urchins' diet. The effects of ocean acidification may therefore be contrasting on well vegetated macroalgal assemblages and barren grounds: in the absence of other human impacts, a decrease of biodiversity can be predicted in vegetated macroalgal assemblages, whereas a lower density of sea urchin could help the recovery of shallow subtidal rocky areas affected by overfishing from barren grounds to assemblages dominated by fleshy macroalgae.

Epitypification and Redescription ofCorallina officinalisL., the Type of the Genus, andC. elongataEllisetSolander (Corallinales, Rhodophyta)

Corallina L. is the type genus of the subfamily Corallinoideae (Aresch.) Foslie and Corallina officinalis L. is the type species of the genus. This name has been applied worldwide, particularly in temperate waters. An attempt to obtain sequence data from the lectotype specimen was not successful. In order to establish a species concept for C. officinalis based on molecular sequence data as well as morphology, an epitype was selected from Devon, England within the vague type locality ‘in O [Oceano] Europaeo’, and from which mitochondrial (cox1) and plastid (rbcL) data were obtained. A second species, Corallina elongata Ellis et Solander (type locality Cornwall, England), was shown previously to include at least two species based on DNA sequences. The lectotype of C. elongata is an illustration and therefore an epitype was selected to provide molecular sequence data, using the same markers as for C. officinalis. These molecular sequences for C. officinalis and C. elongata are compared with those of a third, recently described species from Great Britain, Corallina caespitosa R.H. Walker, J. Brodie et L.M. Irvine: these data provide an example for studying Corallina species taxonomy and diversity in other parts of the world. The implications of this work are discussed in relation to concepts of species distribution.

A Molecular Phylogenetic Study of the Tribe Corallineae (Corallinales, Rhodophyta) with an Assessment of Genus-Level Taxonomic Features and Descriptions of Novel Genera.

A multigene phylogeny using COI-5P (mitochondrial cytochrome c oxidase subunit 1), psbA (PSII reaction center protein D1), and EF2 (elongation factor 2) sequence data for members of the tribe Corallineae was constructed to assess generic boundaries. We determined that traditional reliance on conceptacle position as an indicator of generic affinities in the Corallineae is not supported and taxonomic changes are required. We found that species currently assigned to Pseudolithophyllum muricatum resolved within the Corallineae in all analyses. This is the first record of crustose members in the subfamily Corallinoideae. Further-more, the genus Serraticardia was polyphyletic; we propose to synonomize Serraticardia with Corallina, transfer the type species S.maxima to Corallina (C.maxima (Yendo) comb. nov.), and describe the new genus Johansenia for S.macmillanii (J.macmillanii (Yendo) comb. nov.). Our molecular data also indicate that species in the genus Marginisporum have evolutionary affinities among species of Corallina and these genera should also be synonymized. This necessitates the combinations C.aberrans (Yendo) comb. nov. for M.aberrans (Yendo) Johansen & Chihara, C.crassissima (Yendo) comb. nov. for M.crassissimum (Yendo) Ganesan, and C.declinata (Yendo) comb. nov. for M.declinata (Yendo) Ganesan. Corallina elongata was divergent from all other members of Corallina and is transferred to a new genus, Ellisolandia (E.elongata (J. Ellis & Solander) comb. nov). In addition, COI-5P and internal transcribed spacer (ITS) data combined with morphological characters were used to establish that rather than the four Corallina species recognized in Canada, there are nine.

Benthic assemblages and temperature effects on Paracentrotus lividus and Arbacia lixula larvae and settlement

Recruitment is a principal controlling factor in population dynamics of marine species. In marine invertebrates with a planktonic larval stage, such as echinoids, recruitment is assured by larval supply, settlement and juvenile survival. Larval supply and juvenile survival are affected by a wide range of factors, including temperature, presence of predators, quality and quantity of food. Echinoid larval settlement is mainly conditioned by the finding of a suitable substrate to metamorphose. The sea urchins Arbacia lixula and Paracentrotus lividus are considered key species of the Mediterranean infralittoral rocky shores. At high densities, the grazing activity of both species can produce and maintain barren grounds, a particular habitat condition characterized by extremely low cover values of erect algae with high presence of naked substrates and encrusting corallinales, poor in biodiversity and ecosystem functions. We tested the role of different settlement substrates on the metamorphosis competent larvae of the two species. Furthermore, from our larval rearing trails we were able to identify strong temperature effects on larval development of the two species. P. lividus and A. lixula larvae have been reared at 18°C but for the second species it was necessary to use higher temperatures (22°C) to perform settlement experiments, as in the 18°C set all larvae died in the first week. Both species larvae have been fed Cricosphaera elongata. Metamorphosis of competent larvae has been induced using different substrates: naked stones, Lithophyllum incrustans, Stypocaulon scoparium, Corallina elongata, turf forming algae and Posidonia oceanica. For each species, two larval batches were used for settlement experiments; for each larval batch two replicates/substrates were set up. No differences in the rate of metamorphosis on any of the tested substrates were observed for P. lividus, while A. lixula showed to prefer naked stones and encrusting coralline algae Considering that A. lixula population growth may trigger barren extension on rocky shores, this may lead to a positive feedback between barren extension and A. lixula population density. Furthermore, our results suggest that the predicted rise in seawater temperature may favor A. lixula larval survival and inhibit P. lividus. Combining information on temperature tolerance with other sources of information for these species in the Mediterranean, it is possible to develop a conceptual model of the interaction between the two species and the alternative state of their habitats.

Vertical distribution and seasonality of peracarid crustaceans associated with intertidal macroalgae

Spatial patterns and seasonal fluctuations of intertidal peracarids from Tarifa Island, Strait of Gibraltar, were studied over a two-year period (December 2005–December 2007). A total of 25,749 individuals were collected, comprising 46 species. Amphipods were best represented in the total number of species (32) and individuals (89% of numerical abundance) followed by isopods (12 species and 11% abundance) and tanaids (2 species and 1%). The highest number of species was registered in intermediate levels (1–1.5 m) dominated by Corallina elongata, although the highest abundances of peracarids were associated to seaweeds of lower levels (0–1 m) such as Gelidium corneum, Osmundea pinnatifida, Valonia utricularis and a turf of Caulacanthus ustulatus. The most abundant peracarids, Hyale stebbingi, H. schmidti, H. perieri, Stenothoe monoculoides, Caprella penantis, C. grandimana, Dynamene edwardsii and Ischyromene lacazei, were present throughout the whole year during 2006 and 2007. The highest peracarid densities were measured in April–August coinciding with the highest development of seaweeds, just before the maximum values of water temperature measured at the end of summer. Multivariate analyses confirmed a clear zonation of algae and associated peracarids in a vertical gradient, which was maintained stable during the two-year study. Several physical and biological factors may regulate such patterns of peracarid abundance and future experimental studies are necessary to explore the importance of factors such as competition, predation or weather conditions.

Spatial patterns and seasonal fluctuations of intertidal macroalgal assemblages from Tarifa Island, southern Spain: relationship with associated Crustacea

The dominant intertidal algal species from Tarifa Island, Strait of Gibraltar, together with the associated peracarid crustacean community, were studied over a two-year period (December 2005–December 2007). Gelidium corneum and Gymnogongrus patens were dominant at the lower levels, close to the subtidal. Valonia utricularis, Osmundea pinnatifida, a turf of Caulacanthus ustulatus and Gelidium spp., Corallina elongata and Jania rubens were distributed in intermediate levels, while Ulva rigida, Chaetomorpha aerea and Fucus spiralis were collected from upper levels. The main intertidal seaweeds of Tarifa Island showed a perennial behaviour, but maximum values of biomass were registered during late spring and beginning of summer for most of species while the highest seawater temperatures were measured in late summer and beginning of autumn. Corallina elongata and Jania rubens, the dominant species which shared a niche at platforms of intermediate levels, showed an opposite behaviour, probably to avoid competence: C. elongata showed higher biomass in April–June and lower values in August–October–December, while biomass of J. rubens was higher in December–February and lower in April–August. Associated crustaceans, including mainly amphipods (gammarids and caprellids) were also present throughout the whole year with similar seasonality to seaweeds. However, crustacean density in the intertidal was not only influenced by distribution of algae as substrate, but also by external factors, such as hydrodynamism, oxygen, weather conditions, competition or predation. The present study constitutes the first baseline study dealing with seasonal fluctuations of algae and associated crustaceans in a protected area of the Strait of Gibraltar, an important biogeographical zone between Europe and Africa and the Mediterranean and Atlantic.

Distribution patterns of the peracarid crustaceans associated with the alga Corallina elongata along the intertidal rocky shores of the Iberian Peninsula

Spatial patterns of intertidal peracarids, associated with the alga Corallina elongata, were studied along the whole Iberian Peninsula. A total of 28,215 specimens were collected, comprising 78 different species (57 amphipods, 16 isopods, 4 tanaids and 1 cumacean), most of them with Atlantic-Mediterranean distribution (60%) and only 9% of Mediterranean endemics. Gammarids were dominant in abundance and number of species, representing more than 70% of the total peracarids. The most common species collected during the present study were the caprellid Caprella penantis, the gammarids Hyale schmidti, Hyale stebbingi, Jassa cf. falcata and Stenothoe monoculoides, the isopod Ischyromene lacazei and the tanaid Tanais dulongii. Caprellids and tanaidaceans presented their highest populations in the stations of the Strait of Gibraltar, whereas isopods were more abundant in Atlantic stations. Univariate analyses did not reflected differences in number of species, abundance and Shannon-Weaver diversity between Mediterranean and Atlantic. However, cluster analyses and Whittaker index, as measure of s-diversity, showed a different species composition between Mediterranean and Atlantic and a replacement of species along the coast, especially at the Strait of Gibraltar. The turnover mainly affected species of the same genera, probably related with sympatric speciation. CCA and BIO-ENV analyses showed high correlations between environmental measures (especially conductivity) and peracarid distribution. Mediterranean species tolerated higher values of conductivity and temperature, while Atlantic species were associated with stations characterized by higher oxygen concentrations.

Caprellids (Crustacea: Amphipoda) associated with the intertidal alga Corallina elongata along the Iberian Peninsula

Abundance patterns of intertidal caprellids associated with the alga Corallina elongata were studied along the Iberian Peninsula. Nineteen stations were selected. The Mediterranean coast showed higher seawater temperature and conductivity and lower dissolved oxygen and turbidity than the Atlantic coast. Cover of C. elongata was negatively correlated with seawater temperature and decreased towards the Mediterranean sites. Number of caprellid species and abundances were higher in stations in the Strait of Gibraltar, probably related with the currents' dynamic around this area. In general, caprellids associated with C. elongata were more abundant along the Mediterranean than along the Atlantic, in spite of the lower algal cover in Mediterranean stations. Caprella hirsuta and C. liparotensis were restricted to the Mediterranean coast whereas C. penantis was only found in the Atlantic and the Strait of Gibraltar. Although C. grandimana has been reported along the Mediterranean, its presence on Corallina elongata was restricted to the Strait of Gibraltar. Oppositely, Caprella liparotensis, which usually inhabits Atlantic and Mediterranean intertidal ecosystems, was only present in the Mediterranean and did not coexist with C. penantis along the Atlantic. Probably, competence process among C. grandimana, C. hirsuta, C. liparotensis and C. penantis are regulating the distribution patterns on the intertidal alga Corallina elongata. On the other hand, canonical correspondence analysis showed a clear preference of Caprella penantis at sites with high oxygen concentrations, whereas C. hirsuta was mainly influenced by higher temperature and conductivity.

Metal concentration and structural changes in Corallina elongata (Corallinales, Rhodophyta) from hydrothermal vents

Shallow-water hydrothermal activity is widely present at Azores archipelago. Organisms in such environments present great potential as sentinels of the effects derived from chronically exposure to increased temperature, metal concentrations and reduced pH. This study aimed to evaluate metal concentration in Corallina elongata collected at locations exposed and not exposed to shallow-water hydrothermal activity and evaluate changes in its calcareous structure. Elemental concentration was determined and morphometric analysis was performed by scanning electron microscopy. Thicker cell walls and a bleached appearance were observed on C. elongata specimens from the hydrothermally active location, as well as increased concentrations of elements associated to volcanic activity.This study reports on metal accumulation and morphometric changes in the calcareous structure of C. elongata from a hydrothermally active location, adding new data for further research on such habitats and communities, providing an insight on how coralline algae might be affected by ocean acidification.

Carotenoid composition in Rhodophyta: insights into xanthophyll regulation in Corallina elongata

Macroalgae possess several photoprotection mechanisms, including xanthophyll cycles. Among these cycles, the VAZ (violaxanthin–anteraxanthin–zeaxanthin) cycle controls the interconversion of epoxidated xanthophyll (V) to de-epoxidated forms anteraxanthin and zeaxanthin. This conversion modulates the amount of excess energy that it is dissipated as heat. Presence of functional xanthophyll cycles in Rhodophyta is controversial. In this work we investigated the presence of xanthophyll cycles in red algae. Carotenoid composition of 13 red macroalgae collected in northern Spain was studied by HPLC. This screening showed that carotenoid composition is a conservative trade in rhodophytes, with very few exceptions to the general pattern formed by β-carotene and one to three xanthophylls: anteraxanthin, zeaxanthin or lutein. Corallina elongata and Jania rubens were the only algae containing anteraxanthin as the main xanthophyll. The first species was selected to study whether any truncated xanthophyll cycle between anteraxanthin and zeaxanthin could operate under photoinhibitory conditions. Upon illumination, xanthophyll composition remained stable, without any short-term light-induced de-epoxidation of anteraxanthin to zeaxanthin. However, an inverse relation between both xanthophylls was found. In addition, a seasonal trend of changes in anteraxanthin and zeaxanthin was observed when pigment composition was studied in field samples over the course of a year. We concluded that these variations were more likely due to differential rates of synthesis and degradation of xanthophylls than to the operation of a xanthophyll cycle. The great amount of anteraxanthin in C. elongata may play an structural stability role on light-harvesting complexes.

BIODIVERSITY OF CORALLINE ALGAE IN THE NORTHEASTERN ATLANTIC INCLUDING CORALLINA CAESPITOSA SP. NOV. (CORALLINOIDEAE, RHODOPHYTA)(1).

The Corallinoideae (Corallinaceae) is represented in the northeastern Atlantic by Corallina officinalis L.; Corallina elongata J. Ellis et Sol.; Haliptilon squamatum (L.) H. W. Johans., L. M. Irvine et A. M. Webster; and Jania rubens (L.) J. V. Lamour. The delimitation of these geniculate coralline red algae is based primarily on morphological characters. Molecular analysis based on cox1 and 18S rRNA gene phylogenies supported the division of the Corallinoideae into the tribes Janieae and Corallineae. Within the Janieae, a sequence difference of 46-48 bp (8.6%-8.9%) between specimens of H.squamatum and J.rubens in the cox1 phylogeny leads us to conclude that they are congeneric. J. rubens var. rubens and J.rubens var. corniculata (L.) Yendo clustered together in both phylogenies, suggesting that for those genes, there was no genetic basis for the morphological variation. Within the Corallineae, it appears that in some regions, the name C.elongata has been misapplied. C.officinalis samples formed two clusters that differed by 45-54 bp (8.4%-10.0%), indicating species-level divergence, and morphological differences were sufficient to define two species. One of these clusters was consistent with the morphology of the type specimen of C.officinalis (LINN 1293.9). The other species cluster is therefore described here as Corallina caespitosa sp. nov. This study has demonstrated that there is a clear need for a revision of the genus Corallina to determine the extent of "pseudocryptic" diversity in this group of red algae.

Ecological monitoring of intertidal phytobenthic communities of the Basque Coast (N. Spain) following the Prestige oil spill

Following the Prestige oil spill, six-monthly samplings (spring and autumn) of intertidal macroalgal assemblages were carried out from 2004 to 2006 in twelve locations along the Basque coast. Macroalgal species appeared to be little modified, but species richness, diversity, and algal cover were significantly lower in the first year of the study, so it cannot be ruled out that the arrival of oil on the Basque coast might have had a damaging effect on intertidal communities. On the other hand, no significant differences were detected between locations slightly and moderately affected by oil in any of the structural parameters considered. By contrast, significant differences were detected between locations within each oiling level that indicate that other natural environmental factors play a greater role in the differences between locations than the oiling level. Likewise, significant differences were detected between areas within each location which were not consistent with time, indicating that communities are highly heterogeneous in species richness, diversity and algal cover at the scale of tens of meters. The dominant Corallina elongata and most of the accompanying species did not show significant year-on-year differences in terms of cover. Also, there were no differences between the two oiling levels. Analyses revealed a high spatial variability at the scale of kilometers (locations) and tens of meters (areas) for most of the taxa. The results obtained provide detailed quantitative data on intertidal phytobenthic assemblages of the Basque coast at different spatial and temporal scales that were hitherto unavailable for the region.

Hard coastal-defence structures as habitats for native and exotic rocky-bottom species

The use of hard coastal-defence structures, like breakwaters and seawalls, is rapidly increasing to prevent coastal erosion. We compared low-shore assemblages between wave-protected and wave-exposed habitats on breakwaters along a sandy shore of Tuscany (North-Western Mediterranean). Assemblages were generally characterized by a low diversity of taxa, with space monopolized by Mytilus galloprovincialis and Corallina elongata on the seaward side of breakwaters and by filamentous algae on the landward side. Assemblages in wave-protected habitats were characterized by greater temporal stability than those in exposed habitats and supported non-indigenous macroalgae such as Caulerpa racemosa and Codium fragile ssp. tomentosoides. Hence, the introduction of hard coastal-defence structures in otherwise soft-bottom dominated areas, attracting native and exotic rocky-bottom species, should be of great concern for the conservation of marine biodiversity at local and regional scales and for the management of biological invasions.

Loss of fucoid algae along a gradient of urbanisation, and structure of benthic assemblages

Canopy-forming macroalgae of the genus Cystoseira are being lost in several areas of the Mediterranean Sea. Cystoseira amentacea var. stricta and C. compressa are common species in the Ligurian Sea; they are distributed in patches, but their abundance and distribution is locally vari- able. We investigated changes in relative cover, biomass and morphology of Cystoseira amentacea var. stricta and C. compressa with increasing urbanisation, and effects of the presence or absence of Cystoseira species on the composition and structure of understorey assemblages. C. amentacea var. stricta habitats were lost close to urban areas, while C. compressa slightly increased. The morpholog- ical characteristics of these 2 species were very variable in space and time, and did not vary with urbanisation. Assemblages lacking canopy differed markedly from Cystoseira-dominated assem- blages, particularly assemblages dominated by Corallina elongata, the species most responsive to changes in habitat structure and urbanisation, which forms dense turfs in urban habitats lacking canopies. Marked species-specific differences between the assemblages dominated by the 2 Cysto- seira species were detected. C. amentacea var. stricta is a key species maintaining habitat complex- ity and species diversity in Mediterranean rocky shores and we recommend additional conservation actions, such as habitat restoration by transplantation of this endangered species.

Coastal and estuarine habitat mapping, using LIDAR height and intensity and multi-spectral imagery

The airborne laser scanning LIDAR (LIght Detection And Ranging) provides high-resolution Digital Terrain Models (DTM) that have been applied recently to the characterization, quantification and monitoring of coastal environments. This study assesses the contribution of LIDAR altimetry and intensity data, topographically-derived features (slope and aspect), and multi-spectral imagery (three visible and a near-infrared band), to map coastal habitats in the Bidasoa estuary and its adjacent coastal area (Basque Country, northern Spain). The performance of high-resolution data sources was individually and jointly tested, with the maximum likelihood algorithm classifier in a rocky shore and a wetland zone; thus, including some of the most extended Cantabrian Sea littoral habitats, within the Bay of Biscay. The results show that reliability of coastal habitat classification was more enhanced with LIDAR-based DTM, compared with the other data sources: slope, aspect, intensity or near-infrared band. The addition of the DTM, to the three visible bands, produced gains of between 10% and 27% in the agreement measures, between the mapped and validation data (i.e. mean producer's and user's accuracy) for the two test sites. Raw LIDAR intensity images are only of limited value here, since they appeared heterogeneous and speckled. However, the enhanced Lee smoothing filter, applied to the LIDAR intensity, improved the overall accuracy measurements of the habitat classification, especially in the wetland zone; here, there were gains up to 7.9% in mean producer's and 11.6% in mean user's accuracy. This suggests that LIDAR can be useful for habitat mapping, when few data sources are available. The synergy between the LIDAR data, with multi-spectral bands, produced high accurate classifications (mean producer's accuracy: 92% for the 16 rocky habitats and 88% for the 11 wetland habitats). Fusion of the data enabled discrimination of intertidal communities, such as Corallina elongata, barnacles ( Chthamalus spp.), and stands of Spartina alterniflora and Phragmites australis, which presented misclassification when conventional visible bands were used alone. All of these results were corroborated by the kappa coefficient of agreement. The high classification accuracy found here, selecting data sources, highlights the value of integrating LIDAR data with multi-spectral imagery for habitat mapping in the intertidal complex fringe.