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1. The aim of the present study was to propose a biotic index (North Adriatic Mesophotic BiogEnic Reefs, NAMBER) suitable for assessing the ecological quality of the mesophotic biogenic reefs of the northern Adriatic continental shelf based on photographic sampling. 2. At each of the 20 study sites, the degree of bioconstruction (expressed as percentage cover of crustose coralline algae), the α-diversity (expressed as the mean number of taxa), and the degree of sensitivity to human disturbance and climate change (based on literature data and expert judgement) of the benthic assemblages were selected as descriptors and combined in the NAMBER index, using the best values that the three metrics can currently achieve in the studied region as a reference. 3. The study highlighted that there was large spatial heterogeneity among reefs and high variability in the ecological quality values obtained by NAMBER, ranging from bad to high. The index indicates that reefs lying furthest from the coast, under substantially lower anthropogenic pressure, have a generally higher status of environmental quality. However, a clear geographical pattern did not emerge, as reefs close together often had different ecological qualities. 4. The NAMBER index, which combines three ecological descriptors, in accordance with the requirements of the European Marine Strategy Framework Directive, represents a specific adaptation to the northern Adriatic Sea of a multimetric index previously developed for the north-western Mediterranean Sea, capitalizing on previous knowledge and research efforts. 5. This multimetric biotic index provides an effective standardized tool for monitoring programmes and environmental impact assessments in the northern Adriatic mesophotic biogenic reefs and lays the foundation for ecosystem-based management and conservation in this basin.

Restoration of foundation species in historical habitat may be difficult if adult facilitation is obligatory for survival of early life stages. 2. On intertidal Mediterranean coasts, large-scale loss of the dominant forest- forming macroalga Ericaria amentacea have prompted restoration efforts using recruits. Yet, early life stages may be more susceptible to the abiotic stress that characterizes their habitat. 3. We tested strategies to enhance resilience of lab-cultured juveniles of E. amen- tacea to environmental stress in historical habitat lacking conspecifics. Juveniles were exposed in culture to fluctuations of the dominant physical stressors, irra- diance and temperature, and then outplanted in upper and lower zones of their native intertidal range. 4. Without adult canopy, juvenile outplant survival was limited to the lower tidal range, with nearly complete mortality in the upper zone. Survival was also strongly determined by spatial clumping of recruits within the outplant sub- strate. Longer-term growth in the lower zone was enhanced by fluctuating mild stress in culture, with variable irradiance and concurrent heat pulses increas- ing post-outplant cover by 40%–60% after 4 months. Clumping also promoted growth across experimental treatments. 5. Synthesis and applications. Reliance on self-facilitation feedbacks is a common barrier to foundation species restoration in high-stress habitats. Our results sug- gest that without adult habitat amelioration, environmental stress limits recruit survival in intertidal algal forest. Yet, exposure to transient, low environmental stress in culture and outplanting of clumped individuals may confer resilience and allow successful establishment of early life stages in zones of reduced abi- otic stress, providing a source for gradual colonization of more high-stress areas.

In the present study, alginate yield and composition were investigated during the seasonal life cycle of the alien brown alga Sargassum muticum harvested from the Atlantic coast of Morocco. Alginate yield ranged from 11.14% in winter to 25.62% in spring/early summer, coinciding with maximum vegetative growth. Monthly monitoring of the alginate block structure showed that the highest mannuronate (M)/guluronate (G) ratio was recorded during the maximum development of S. muticum, before sexual maturity and during resumption of vegetative growth, giving maximum flexibility to the alga. The unusually high molar monad fractions (FG) and dyad fractions (FGG) of guluronic acid in late summer/early autumn appeared to be related to stiffness of senescent thalli. Rheological characterisation showed that the alginate of S. muticum exhibited pseudoplastic behaviour, with the highest apparent viscosities measured in late summer/early autumn when the G blocks dominated the alginate structure. This study suggests that S. muticum could be exploited as an alginophyte for commercial applications. The best harvest time is May-June, which corresponds to the highest alginate yield, maximum thallus growth, and largely completed sexual reproduction, ensuring sustainable exploitation of the species.

Canopy-forming brown algae support highly productive ecosystems whose decline has been attributed to the interplay of several anthropogenic disturbances. Climate change could have disruptive effects on the biology of these species, but the role of temperature in the development of early life stages is poorly understood. The aim of this study was to assess the response of Ericaria giacconei, a winter-reproducing Southern–Mediterranean endemic species, to thermal stress by testing five temperatures (12, 15, 18, 24, and 28°C) on adults and early stages. Chlorophyll a fluorescence of adult plants was measured at 0, 24, 72, and 120 h on nine fronds in each of the three aquaria per treatment. To assess egg release, zygote settlement, and embryo growth rate, approximately 1,200 receptacles were cultured on six Petri dishes per temperature treatment, and 10 random subsections of 2 ×2 mm were examined in three Petri dishes at 0, 20, 44, and 92 h after fertilization. Adult plants showed a plastic physiological response, and thermal stress had no significant effect on PSII efficiency. Embryos fully developed only at 12 and 15°C. Mortality increased at 18 and 24°C, and no zygotes survived at 28°C. In a scenario of further increasing temperatures, the effects of warming could affect the recruitment of E. giacconei and increase its vulnerability to further stresses. These effects on the survival of early stages, which are the bottleneck for the long-term survival of the species, should be taken into account in conservation and restoration measures to maintain canopy-forming macroalgal populations and associated biodiversity and ecosystem services.

1. The worldwide decline of marine forests, due to human impacts and climate change, emphasizes the need to develop and implement effective and sustainable solutions to restore these endangered habitats and to re-establish the services they provide. 2. In this study, the ex situ restoration of Treptacantha barbata, a Mediterranean subtidal habitat-forming species of brown seaweed, was for the first time implemented in a marine protected area in the Adriatic Sea. Two restoration efforts were performed in 2019. The first one was started in winter, after a marine heatwave that triggered early fertility, the second one in spring, when the species usually reproduces. 3. This study aimed to evaluate: 1) the disruptive effects of a thermal anomaly on the reproductive biology and performance in culture of T. barbata; and 2) the impact of the grazing pressure on juveniles after the outplanting. 4. The first cultivation was more productive than the second one, in terms of zygote release and germling growth. To mitigate the low efficiency of the second culture and to avoid prolonged highly-demanding maintenance in the mesocosms, the cultivation period was extended outdoors using a structure suspended in the water column. 5. The modular frames conceived for outplanting T. barbata proved to be effective because of their easy operability and low cost. Controlling for herbivorous fish had significant positive effects on both juvenile survival and growth. 6. The outcomes highlighted that an unpredictable climatic event and fish grazing were major threats that impaired the restoration process of T. barbata. These stressors should be considered when developing plans to implement effective large-scale restoration of canopy-forming macroalgae.

In the Mediterranean Sea, marine forests constituted by Cystoseira sensu lato (s.l.) species (Fucales, Phaeophyceae) support highly productive ecosystems, whose decline was ascribed to the interplay of several anthropogenic impacts. Recently, this decline has also been attributed to the increase of seawater temperatures and thermal anomalies, which can alter the reproductive phenology, germling growth and population viability of Cystoseira s.l. species. To manage the conservation of these communities is fundamental to evaluate how current and future foreseen warming scenarios will affect the thermal physiology of different life stages of these species. Moreover, a recognized strategy of management is the identification and protection of contemporary climatic refugia, which may safeguard the persistence of these habitat-forming species. The present research focused on Cystoseira hyblaea Giaccone, which is endemic to the Sicily Channel (Central Mediterranean Sea) and has a narrow distributional range, being only reported in Punta D’Aliga, where it was no longer found, in Cap Bon (Northern Tunisian coast) and in Portopalo di Capo Passero (Sicily, Southern Italy). This species lives in the intertidal and upper sublittoral zone on both semi-exposed and exposed rocky coasts, and its maximum vegetative and reproductive development occurs during winter. Considering the ongoing warming scenario, C. hyblaea could be severely threaten being an intertidal species and due to its cold affinity, the winter reproductive phenology and the restricted distributional range. Therefore, the aim of this study was to assess the thermal tolerance of both embryos and adults of C. hyblaea, in order to evaluate which stage might be the most vulnerable to climate change, and to foresee the possible fate and argue about the future conservation status of this species under a predicted global warming. To perform this research, egg release, zygote settlement, embryo development and adult photosynthetic efficiency were studied, on both early life stages and adults, under five temperature treatments (12, 15, 18, 24, 28 °C) in controlled mesocosms. In particular, ca. 1200 receptacles were cultivated on 6 Petri dishes per temperature treatment. At 0, 20, 44, 92 h after fertilization, 10 random subareas of 2x2 mm were examined in 3 Petri. Chlorophyll a fluorescence of adults was measured at 0, 24, 72, 120 h on 9 fronds in each of the 3 aquaria per treatment. Through the trial, it was observed that the receptacles’ release efficiency did not vary significantly among temperatures. However, the settlement efficiency of C. hyblaea increased from 12 to 18 °C and decreased at 28 °C. Indeed, the extremely low settlement efficiency was at 28 °C, due to the fact that zygotes had undergone lysis because of thermal stress. Regarding the early life stages, embryos showed a complete development only at 12 and 15 °C, while yet at 18 °C mortality increased sharply, being total at 28 °C. In particular, the highest developmental rate was observed at 15 °C (highest percentage of embryos with rhizoids already at 20 h AF), suggesting that this temperature constitutes the thermal optimum for reproduction and development of early developmental stages. On the contrary, adults of C. hyblaea showed a more plastic physiological response and thermal stress did not significantly affect photosynthetic efficiency. The present study demonstrated that adults of C. hyblaea resulted not substantially affected by heat with an expected ability to acclimatise also to elevated temperatures. Contrarily, the early developmental stages resulted strictly stenotherm, requiring a very narrow range of low temperatures for an effective recruitment and development (12-15 °C). Therefore, the recruitment could represent the most vulnerable process to the impacts of climate change in the population dynamics of C. hyblaea. Moreover, the results confirm the cold affinity of this species and suggest that the localities, in which C. hyblaea is confined, are acting as potential climatic refugia. If failure in the recruitment process is reiterated for several years, it will lead to an impoverishment of C. hyblaea populations, ultimately hindering their long-term viability in its current range. Given the fragmented and restricted range and increased frequency of extreme climatic events, C. hyblaea may undergo local extinction. Considering this perspective, the areas in which C. hyblaea manages to survive should receive a higher level of protection. Moreover, this species should be included in the IUCN Red List of Species (IUCN, 2021), being classified as a “Critically endangered” or “Rare”.

The global decline of brown algal forests along rocky coasts is causing an exceptional biodiversity loss. Regardless of conservation efforts, different techniques have been developed for large-scale restoration strategies in the Mediterranean Sea. In this study we tested ex situ pilot restoration of Gongolaria barbata (=Treptacantha barbata) for the first time in Slovenian coastal waters. Healthy apical fronds of the species were collected and the development of recruits on clay tiles was followed under laboratory conditions for 20 days. Despite the experimental difficulties experienced, especially due to the lack of antibiotics to prevent the growth of the biofilm, G. barbata recruits were outplanted in the sea on two concrete plates with 48 tiles each, protected by purpose-built cages to avoid grazing by herbivorous fish. The high survival rate of juveniles after four months in the field (89% of the tiles on the plate that was constantly protected) suggests that outplanting G. barbata is an operable approach for restoration efforts in the northern Adriatic Sea. Our first experiment in Slovenian coastal waters provides new information for the optimization of the best practices during the laboratory cultivation and addresses the early steps of restoration and introduction of young thalli in the natural environment.

International audience; Lithophyllum species in the Mediterranean Sea function as algal bioconstructors, contributing to the formation of biogenic habitats such as coralligenous concretions. In such habitats, thalli of Lithophyllum, consisting of crusts or lamellae with entire or lobed margins, have been variously referred to as either one species, L. stictiforme, or two species, L. stictiforme and L. cabiochiae, in the recent literature. We investigated species diversity and phylogenetic relationships in these algae by sequencing three markers (psbA and rbcL genes, cox2,3 spacer), in conjunction with methods for algorithmic delimitation of species (ABGD and GMYC). Mediterranean subtidal Lithophyllum belong to a well‐supported lineage, hereby called the L. stictiforme complex, which also includes two species described from the Atlantic, L. lobatum and L. searlesii. Our results indicate that the L. stictiforme complex consists of at least 13 species. Among the Mediterranean species, some are widely distributed and span most of the western and central Mediterranean, whereas others appear to be restricted to specific localities. These patterns are interpreted as possibly resulting from allopatric speciation events that took place during the Messinian Salinity Crisis and subsequent glacial periods. A partial rbcL sequence from the lectotype of L. stictiforme unambiguously indicates that this name applies to the most common subtidal Lithophyllum in the central Mediterranean. We agree with recent treatments that considered L. cabiochiae and L. stictiforme conspecific. The diversity of Lithophyllum in Mediterranean coralligenous habitats has been substantially underestimated, and future work on these and other Mediterranean corallines should use identifications based on DNA sequences.

Rhodolith beds represent a key habitat worldwide, from tropical to polar ecosystems. Despite this habitat is considered a hotspot of biodiversity, providing a suite of ecosystem goods and services, still scarce quantitative information is available thus far about rhodolith beds occurrence and ecological role, especially in the Mediterranean Sea. This study reports the composition and patterns of distribution of rhodolith assemblages found in four study areas along ca. 860 km of coast in the Central Mediterranean Sea. These rhodolith beds were studied for the first time and significant differences at all spatial scales have been highlighted, documenting the high variability of this habitat. Rhodolith species composition, morphology and distribution have been discussed considering the potential role of environmental factors in driving these patterns. The need for improving their protection is discussed to complement present conservation and management initiatives, particularly in the frame of the EU Marine Strategy Framework Directive.

Anthropogenic impacts and rapid environmental changes are causing unpredictable shifts in Mediterranean canopy‐forming brown algae, leading to their regression or loss. Thus, there is an urgent need to set standards and guidelines to optimize the restoration, in order to grant the persistence of marine forests in the future. Out‐planting represents an innovative technique for restoring Fucales, although its implementation consists of a set of delicate steps (Falace et al. 2018, De La Fuente et al. 2019), which need to be tailored to the specific requirements of the target species.Here, we report the results gathered both in the Ligurian Sea and the Gulf of Trieste during the first two years of the EU project ROCPopLife. The two sites are subject to different regimes of human impact (being the Ligurian site in a good environmental status, while the Adriatic site in an urbanized context), but both experienced abrupt and extreme climate events. In the Ligurian Sea, in July 2018 clay tiles with Cystoseira amentacea var. stricta Montagne germlings (~3 mm) were screwed to the rocky shore. After 2 months in the field, over the 40% of the tiles were covered with juveniles of ca. 8 mm. However, 6 months after the tile deployment, an unprecedented storm surge severely affected the restoration performance, leading to the loss of the 80% of the tiles. The remaining tiles hosted 3 to 6 cm‐long juveniles, which reached 6‐9 cm in length after 1 year. In the Gulf of Trieste, a heatwave of 2.65 °C in February 2019 caused a premature reproductive event in Treptacantha barbata (Stackhouse) S. Orellana & M. Sansón, so that the species was found fertile almost 3 months earlier than usual (Bevilacqua et al. 2019). This anomalous event was exploited for carrying out a restoration event, and the same procedure was carried out in May. However, the number of released zygotes was 10 times lower and the germling length after 4 weeks of culture was ¼ with respect to the previous anomalous event. Once in the field, half of the tiles from the February event were protected against herbivores; starting from the fourth week, length was significantly lower in unprotected tiles, and, after 3 months, the 36% of the unprotected tiles resulted empty because of grazing effects. Since both predictable site‐specific stressors and anomalous climatic events can severely affect the restoration actions, the challenge is now to optimize the restoration process (from the monitoring of the donor populations to that of outplants) in order to overcome the negative effects of unpredictable impacts.

Marine bioconstructions are biodiversity-rich, three-dimensional biogenic structures, regulating key ecological functions of benthic ecosystems worldwide. Tropical coral reefs are outstanding for their beauty, diversity and complexity, but analogous types of bioconstructions are also present in temperate seas. The main bioconstructions in the Mediterranean Sea are represented by coralligenous formations, vermetid reefs, deep-sea cold-water corals, Lithophyllum byssoides trottoirs, coral banks formed by the shallow-water corals Cladocora caespitosa or Astroides calycularis, and sabellariid or serpulid worm reefs. Bioconstructions change the morphological and chemicophysical features of primary substrates and create new habitats for a large variety of organisms, playing pivotal roles in ecosystem functioning. In spite of their importance, Mediterranean bioconstructions have not received the same attention that tropical coral reefs have, and the knowledge of their biology, ecology and distribution is still fragmentary. All existing data about the spatial distribution of Italian bioconstructions have been collected, together with information about their growth patterns, dynamics and connectivity. The degradation of these habitats as a consequence of anthropogenic pressures (pollution, organic enrichment, fishery, coastal development, direct physical disturbance), climate change and the spread of invasive species was also investigated. The study of bioconstructions requires a holistic approach leading to a better understanding of their ecology and the application of more insightful management and conservation measures at basin scale, within ecologically coherent units based on connectivity: the cells of ecosystem functioning.

Glyphosate, as a broad-spectrum herbicide, is frequently detected in water and several studies have investigated its effects on several freshwater aquatic organisms. Yet, only few investigations have been performed on marine macroalgae. Here, we studied both the metabolomics responses and the effect on primary production in the endemic brown algae Fucus virsoides exposed to different concentration (0, 0.5, 1.5 and 2.5 mg L−1) of a commercial glyphosate-based herbicide, namely Roundup®. Our results show that Roundup® significantly reduced quantum yield of photosynthesis (Fv/Fm) and caused alteration in the metabolomic profiles of exposed thalli compared to controls. Together with the decrease in the aromatic amino acids (phenylalanine and tyrosine), an increase in shikimate content was detected. The branched-amino acids differently varied according to levels of herbicide exposure, as well as observed for the content of choline, formate, glucose, malonate and fumarate. Our results suggest that marine primary producers could be largely affected by the agricultural land use, this asking for further studies addressing the ecosystem-level effects of glyphosate-based herbicides in coastal waters.

Structure and spatial variability of coralligenous assemblages of the Apulian continental shelf in the southern Adriatic Sea were investigated. The area consists of small coralligenous outcrops distributed between 30 and 100 m of depth on coarse detritic or muddy bottom. Photographic samples, obtained through a Remotely Operated Vehicle, were analyzed to evaluate the abundance of the main taxa or morphological groups of macroalgae and sessile invertebrates, and the deposited sediment. A multifactorial sampling design was used to compare assemblages at two depth ranges, the shallow outcrops (between 35 and 45 m) and the deep outcrops (between 60 and 70 m), and to determine the main scales of spatial variation. Assemblages were dominated by encrusting and erect sponges, encrusting and filamentous algae, scleractinians, encrusting and erect bryozoans and the Zoantharia Parazoanthus axinellae. Deep assemblages were characterized by lower alpha and beta diversity, and by the decrease or disappearance of sensitive organisms, such as coralline macroalgae, scleractinians and erect bryozoans, and by the dominance of encrusting sponges, P. axinellae and hydrozoans. Sedimentation was higher on deep outcrops and was suggested to be the main driver of differences between shallow and deep assemblages. The peculiar composition of assemblages found in the Apulian continental shelf provides evidence that these outcrops represent an uncommon coralligenous habitat.

Carpodesmia barbatula (= Cystoseira barbatula) (Fucales, Phaeophyta) is a species endemic to the Southern Mediterranean Sea, which grows in clean waters on exposed sublittoral rocky shores. Together with other species of the genus Cystoseira sensu lato, it is an ecosystem engineer that forms dense canopy forests, sustaining biodiversity, productivity and nutrient cycling in temperate rocky reefs. Human impacts and climate stressors are seriously hampering these ecosystems and actual conservation efforts appear insufficient for their preservation. Restoration actions could be a solution for the loss of these habitats, but they require the deep knowledge of the target species. In the present study, we describe egg release, zygote development and germling growth of C. barbatula, poorly known, despite its importance in the upper sublittoral seaweed flora. The aim is to improve the knowledge on the early life stages of this rare and threatened species, towards its possible future restoration.

In the Mediterranean Sea, brown algae belonging to the Cystoseira genus play a valuable role as foundation species. Due to evidences of regression/loss of the habitats of these species caused by the interplay of human and climatic disturbances, active restoration measures have been encouraged by EU regulations. In particular, nondestructive restoration techniques, which avoid the depletion of threatened species in donor populations, are strongly recommended. In the framework of the EU project ROCPOP-Life, the first ex situ outplanting experience of Cystoseira amentacea var. stricta has been implemented in the Cinque Terre Marine Protected Area (northwestern Mediterranean). A total of 400 clay tiles, hosting approximately three mm-long germlings of C. amentacea, were fixed to the rocky shore with screws: the tiles were monitored for the next 2 months by photographic sampling, and survival (presence/absence of juveniles on the tiles), cover and growth were assessed. Additional sampling was performed 6 months after tile deployment, after which an unprecedented storm surge severely affected the restoration performance. After 2 months, over 40% of the tiles were covered with Cystoseira juveniles, which reached approximately eight mm in total length. The tiles that survived the storm hosted three to six cm-long juveniles. The high cover (≥25%), assuring moisture and shading, and the appropriate size of the juveniles, to avert micro-grazing, at time of deployment were key to the survival and growth of the outplanted juveniles, increasing the potential for restoration success. Our findings show that outplanting of midlittoral canopy-forming species is a feasible approach for restoration efforts, with particular attention given to the early phases: (i) laboratory culture, (ii) transport, and (iii) juvenile densities. These results are strongly encouraging for the implementation of restoration actions for C. amentacea on a large scale, in light of EU guidelines.

Herbicides are increasingly recognised as sources of water pollution. Glyphosate-based herbicides (GBHs) are widely used because of their low cost and high effectiveness. By measuring the photosynthetic efficiency of Fucus virsoides fronds exposed to a GBH (Roundup® Power 2.0), we investigated the effect of a continuous exposure (6 days) and the potential of recovery after a short exposure (24 h). Both experiments were carried out combining GBH with and without nutrient enrichment, simulating a runoff event. A factorial experimental design allowed us to assess the potential of interactions between GBH and nutrients, which are likely to co-occur in coastal areas. Our results show deleterious effects of GBH at low concentration on F. virsoides, independently from the duration of exposure and the presence of nutrients. The use of herbicides on land might represent an underestimated threat for coastal systems, as suggested by the irreversible impact on the macroalgae Fucus virsoides observed after a short experimental exposure to a common glyphosate-based herbicide

Protocols for Macroalgae Research describes state-of-the-art approaches and applications in seaweed research. The book is comprised of 31 protocols in all and provides critical information regarding the cultivation and preservation of seaweeds, their chemical composition, as well as their cellular and molecular characterization. This type of research is critical and timely, as the last few decades have witnessed remarkable advancements in phycological research worldwide. Consideration of algal resources for food, fuel, chemicals, feed, and fertilizer has furthered the development of diverse laboratory techniques that not only advance their utilization substantially, but also provided new insights in understanding the molecular basis of their form and function. This recent progress has enabled researchers to determine and quantify various metabolites and organic macromolecules such as carbohydrates, proteins, and lipids. Protocols for Macroalgae Research thus uses macroalgae as a model organism for addressing fundamental research problems. No recent comprehensive literature of this format exists on this topic. As such, this state-of-the-art protocol text both develops and standardizes the various macroalgae approaches located within the field. It does so by featuring a wide-range of protocols from invited experts; each protocol features a brief introductory overview, an inventory of materials and reagents, and step-by-step experimental procedures, which include helpful notes offering care and cautions. This protocol book is an invaluable reference for beginning and preexisting researchers within the field of macroalgae.

Due to multiple impacts, Cystoseira forests are experiencing a significant decline, which is affecting the ecosystem services they provide. Despite conservation efforts, there is an urgent need to develop best practices and large-scale restoration strategies. To implement restoration actions, we developed an ex situ protocol for the cultivation of Cystoseira. amentacea var. stricta, aimed at reducing the time needed for laboratory culture, thus avoiding prolonged maintenance and minimizing costs. Specifically, we tested the effects of temperature, light and substratum on settlement and growth of early life stages using a factorial experiment. Temperature (20 and 24°C) and photoperiod (15L:9D) were selected to reflect the conditions experienced in the field during the reproductive period. Two light intensities (125 and 250 μmol photons m-2s-1) were selected to mimic the condition experienced in the absence of canopy (i.e. barren-higher light intensity) or in the understory (lower light intensity) during gamete release. The tested substrata were flat polished pebbles and rough clay tiles. The release of gametes and the successive survival and development of embryo and germlings were followed for two weeks. Regardless of the culture conditions, rougher tiles showed higher zygote settlement, but the substrata did not affect the successive development. Zygote mortality after one week averaged 50% and at the end of the second week, embryonic survival was higher under lower light and temperature conditions, which also determined the growth of larger embryos.

Marine bioconstructions are biodiversity-rich, three-dimensional biogenic structures, regulating key ecological functions of benthic ecosystems worldwide. Tropical coral reefs are outstanding for their beauty, diversity and complexity, but analogous types of bioconstructions are also present in temperate seas. The main bioconstructions in the Mediterranean Sea are represented by coralligenous formations, vermetid reefs, deep-sea cold-water corals, Lithophyllum byssoides trottoirs, coral banks formed by the shallow-water corals Cladocora caespitosa or Astroides calycularis, and sabellariid or serpulid worm reefs. Bioconstructions change the morphological and chemicophysical features of primary substrates and create new habitats for a large variety of organisms, playing pivotal roles in ecosystem functioning. In spite of their importance, Mediterranean bioconstructions have not received the same attention that tropical coral reefs have, and the knowledge of their biology, ecology and distribution is still fragmentary. All existing data about the spatial distribution of Italian bioconstructions have been collected, together with information about their growth patterns, dynamics and connectivity. The degradation of these habitats as a consequence of anthropogenic pressures (pollution, organic enrichment, fishery, coastal development, direct physical disturbance), climate change and the spread of invasive species was also investigated. The study of bioconstructions requires a holistic approach leading to a better understanding of their ecology and the application of more insightful management and conservation measures at basin scale, within ecologically coherent units based on connectivity: the cells of ecosystem functioning.

Coralline red algae are significant components of sea bottom and up to now considered as exclusively marine species. Here we present the first coralline alga from a freshwater environment, found in the Cetina River (Adriatic Sea watershed). The alga is fully adapted to freshwater, as attested by reproductive structures, sporelings and an inability to survive brackish conditions. Morphological and molecular phylogenetic analyses reveal the species belongs to Pneophyllum and is described as P. cetinaensis sp. nov. The marine-freshwater transition most probably occurred during the last glaciation. The brackish-water ancestor was preadapted to osmotic stress and rapid changes in water salinity and temperature. The particular characteristics of the karst Cetina River, such as hard water enriched with dissolved calcium carbonate and a pH similar to the marine environment, favoured colonization of the river by a marine species. The upstream advance and dispersal is facilitated by exceptionally pronounced zoochory by freshwater gastropods. Pneophyllum cetinaensis defies the paradigm of Corallinales as an exclusively marine group.

The protocols available for sampling and monitoring shallow subtidal rhodolith beds (RBs) are inadequate for the deep Mediterranean analogues, and need calibration in order to attain comparable results. After reviewing the present knowledge of the specificities of Mediterranean RBs, and in the framework of the ongoing international effort for their conservation, a two-step approach is suggested for their definition, identification, delimitation, description, and monitoring. Regional mapping should be improved, and RBs should be identified and delimited as those areas of the sea floor with >10% cover of live rhodoliths over a minimum surface of 500 m2, on 1:10000 scale. More detailed scales (at least 1:1000) should be used for monitoring selected RBs, in order to detect significant changes through time. Beside location and areal extent, the description of RBs should include the occurrence of macroscopic sedimentary structures of the sea floor, thickness of live cover, mean percentage cover of live thalli and surface live/dead ratio, cover of dominant morphologies of rhodoliths (simplified on a ternary diagram), and volumetrically important calcareous algal species. For the purpose of assessment of the ecological status and the evaluation of human-induced impacts, quantitative data about community composition are required. The comparative assessment of ecological status and the identification of RBs of high conservation value for special protection should consider the natural geographic and seasonal/annual variability of RBs. Copyright © 2015 John Wiley & Sons, Ltd.

Phymatolithon calcareum is a species of non-geniculate coralline red algae that commonly forms maerl beds. Tetrasporangial thalli of this species are characterized by unattached growths (rhodoliths), which develop as a branched system without a central nodule, while the attached crustose forms are uncommon and are known only from Brittany (Atlantic coasts of France). In this study we confirm with molecular data the existence of attached crustose tetrasporangial thalli and describe for the first time epilithic, fruticose tetrasporangial specimens from the Mediterranean Sea (Vis Island, Croatia). Since the identification of coralline algal species is difficult due to the high morphological plasticity of the group, molecular analyses based on the nuclear nSSU and the plastidial psbA markers were necessary to correctly identify the specimens. Our study shows that P. calcareum tetrasporangial thalli have the ability to grow both unattached and attached, and we argue this to be in relation to the environmental conditions found at different depths. This ability permits the alga to colonize different habitats of the coastal environment.

The genera Hydrolithon and Porolithon are the most discussed taxa of non-geniculate Corallinaceae, as well as the most poorly known. Anatomical observations based usually on thallus construction, number of epithallial cell layers, trichocyte arrangement, occurrence of vegetative filaments between the trichocytes, and presence/absence of cell fusions and secondary pit connections led to different interpretations mainly due to the lack of available reproductive material from type specimens. Recently molecular surveys on the phylogeny of the Corallinales supported the hypothesis of considering Hydrolithon and Porolithon as two distinct genera but, up to now, several taxonomic questions remain in part unanswered. For these reasons identification of species belonging to these genera is still very difficult and can often lead to misidentification of taxa. In this study we report the discovery of a species of the Hydrolithon group found along the coast of Vis Island, Croatia, Adriatic Sea. Samples were identified through morpho-anatomical examinations and the phylogenetic position of this species was investigated through molecular analyses based on the nuclear nSSU and the plastidial psbA markers. This finding represents the first report for the Mediterranean Sea of Hydrolithon rupestre, one of the few encrusting coralline algae reported to overgrow live corals. The species can represent a possible threat to populations of Adriatic scleractinian corals.

The distribution of the endemic brown alga Fucus virsoides was assessed along the northern Adriatic coastline. A high-resolution geographic information system database was created using visual census methods to identify the presence and abundance of algae, including the geomorphology of the substrate. Samples of F. virsoides were collected for analysis of the quantitative spatial distribution. The abundance of F. virsoides was related to several environmental variables, including the relative exposure index (REI). The results support the hypothesis that the distribution of F. virsoides in the Gulf of Trieste is influenced mainly by the stability of mediolittoral substrata, wave exposure and the vicinity of freshwater inputs. Populations of this species are widespread in the Gulf of Trieste. Many of them were found growing inside small harbours or along a boatyard, where fluctuations in salinity and nutrient concentrations are frequent. Therefore, we conclude that F. virsoides cannot be considered an ecological indicator for seawater pollution nor for climate change, since it is subjected naturally to high pollution levels and environmental variability.

Publisher Summary This chapter presents a multidisciplinary study of the major characteristics of a set of submarine rock outcrops in the Northern Adriatic Sea: the rock occurrence, embedded down to about 1 m from the seafloor in the bottom sediments; numerous gas accumulations in the proximity of the outcrops; small-scale mud volcanoes; and microbial mats around the seepage site. From the biological point of view, a total of 112 macroalgal taxa were recorded. The different number of taxa recorded at the San Pietro and Bardelli sampling sites have been related to the different distance from the coast and to water depth. The data highlights that the seabed is almost flat, locally showing the occurrence of rock outcrops, with a range of sizes, shapes, and spatial orientations. On the side-scan survey (SSS) data, they appear as high backscatter features. The seabed is mainly composed of sands. Some species that characterize these outcrops are acknowledged as important bioconstructors distinctive of the Mediterranean area. The seafloor sedimentary deposits show a gradual increase of the fine fraction from the coast toward the offshore; then a progressive increase in the coarse fraction in the central part of the study area (residual sands of the TST) is recognized. The fragile biological equilibrium of these structures, the slow-growing calcareous organisms considered as nonrenewable resources, and the dredging and bottom trawling pressure that strongly threatens the physical characteristics of the habitat, and negatively affect the associated biota, all motivate the need to protect the Trezze and their surrounding seabed.

Coralline algae are among the most common seaweeds in benthic habitats worldwide, as well as one of the most species-diverse groups. Unfortunately, they are also among the most problematic in terms of species circumscription and characterization. Their taxonomic history has been plagued by problems of cryptic diversity, phenotypic plasticity and taxonomic misinterpretations related to the importance of some morphological characters. Key tasks in current coralline taxonomy are to clarify the extent of genetic varia- tion of individual species and link type specimens with molecular phylogenetic clades. We examined three Mediterranean species of Lithophyllum (L. byssoides, L. incrustans, L. stictaeforme) using a combination of molecular markers (cox 2,3 spacer and psbA, rbc Land 18S rDNA genes). The results unraveled different scenarios for the three species. Mediterranean L. byssoides represents a well-defined entity that should be separated at species level from Atlantic populations reported under the same name. Cox 2,3 and psbA data showed an unexpectedly high variation, suggesting limited dispersal in populations of this species. Lithophyllum incrustans is the type species of the genus Lithophyllum and its characterization is therefore critically important. A partial rbc L sequence obtained from the type material allowed to bridge the gap between molecular sequences and name-bearing type. In light of this result we concluded that L. incrustans is common in subtidal habitats and may easily form rhodoliths. Intertidal crusts reported as L. incrustans both in the Mediterranean and in Atlantic Europe probably do not belong to this species. Lithophyllum stictaeforme, as currently circumscribed on morphological basis, represents a complex of cryptic species for which a taxonomic and nomenclatural reassessment is necessary. Taken together, our results indicate that the genetic diversity of Mediterranean coralline algae is probably much higher than currently believed and sequences from type specimens will be essential to unambiguously identify many species.