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Understanding of non-geniculate coralline algal (NGCA) diversity, prevalence, and distribution in the tropical western North Atlantic is currently limited by reliance on morphological and anatomical features that are inadequate for species identifications. Reef surveys from two study sites, the Florida Keys (Florida, USA) and Roatán (Honduras), provided prevalence data for the main benthic organisms as well as relative abundance for NGCA genera. NGCA collected during these surveys and from additional sites and depths were identified using DNA sequences from two plastid genes, psbA and rbcL, and two nuclear genes, SSU and LSU, and supported by morphological and anatomical descriptions. Bayesian and Maximum Likelihood phylogenetic analyses, along with species delimitation and genetic distance methods, resolved 11 genera within two orders. Within the Corallinales, the genera Dawsoniolithon, Porolithon and Spongites each had one species, Harveylithon and Lithophyllum had two, Titanoderma three, Hydrolithon four, Neogoniolithon eight, and an unknown genus within the subfamily Neogoniolithoideae had 11 putative species. Within the Hapalidiales, the genera Phymatolithon and Roseolithon each had one species. This study reinforces the inability of morphological and anatomical features to distinguish NGCA species in the tropical western North Atlantic, resulting in substantial underestimations of species richness and diversity. [ABSTRACT FROM AUTHOR]

Understanding how coral reefs respond to disturbances is fundamental to assessing their resistance and resilience, particularly in the context of climate change. Due to the escalating frequency and intensity of coral bleaching events, it is essential to evaluate spatio-temporal responses of coral reef communities to disentangle the mechanisms underlying ecological changes. Here, we used benthic data collected from 59 reefs in the Red Sea over five years (2014–2019), a period that encompasses the 2015/2016 mass bleaching event. Reefs were located within three different geographic regions with different environmental settings: north (Duba; Al Wajh), central (Jeddah; Thuwal), and south (Al Lith; Farasan Banks; Farasan Islands). Coral community responses were region-specific, with communities in the south being more promptly affected than those in the northern and central regions, with hard and soft coral cover dropping drastically in several reefs from around > 40% to < 5% two years after bleaching. Coral bleaching effects were particularly evident in the decrease of cover in branching corals. Overall, we documented a shift towards a dominance of macroalgae, turf algae, and crustose coralline algae (CCA). Using remote sensing data, we analyzed sea surface temperature (SST) regimes at the study sites to infer potential drivers of changes in benthic composition. Both SST and Degree Heating Weeks (DHW) only partially aligned with the responses of benthic communities, highlighting the need for more accurate predictors of coral bleaching in the Red Sea. In times of intense coastal development along Saudi Arabia's Red Sea coast, our study provides crucial baseline information on developments in coral reef community composition, as well as to guide decision-making, namely restoration efforts. [ABSTRACT FROM AUTHOR]

The disappearance of canopy-forming algae in coastal habitats exposes crustose coralline algae (CCA) to varying light conditions during the transition from foliose macroalgal habitats to barren ground by physical, chemical, or biological interaction. We hypothesized that the sudden increase in light intensity, resulting from the absence of canopy-forming algae, leads to photodamage in CCA related to inhibition of growth. To test this, a 4-week indoor incubation experiment was conducted under different light intensities (20-, 60-, 120-, and 250-μmol photons m−2 s−1). Results revealed that CCA can acclimate to limited light environments, with the efficiency of PSII significantly reduced at higher light levels. Photoprotective mechanisms were activated under persistent stress, leading to a reduction in encrusting area and CCA bleaching. This suggests that CCA coexist with canopy-forming algae in environments with sufficient light exposure, benefiting from the shade provided. However, if directly exposed to light due to the disappearance of canopy-forming algae, CCA faces extreme light stress and potential disappearance. [ABSTRACT FROM AUTHOR]

Tropical carbonate systems are valuable archives of paleoenvironments, as the carbonate growth is intimately affected by water depth and climatic conditions. Geochemical data from the Burdigalian interval in IODP Site U1468 in the Maldives, northern Indian Ocean, were integrated with sedimentological and paleontological data for a more detailed reconstruction of depositional history. Generally, the Sr/Ca values of slope sediments record highstand progradation in both sequence unit and whole Burdigalian interval, while the absence of higher Sr/Ca ratio close to the sequence boundary during the early Burdigalian could be related to the erosion of deeper-water sediments due to the activity of bottom current. From 20.5 to 19.1 Ma and from 17.9 to 17.2 Ma, nutrient level and productivity were moderately elevated due to the terrigenous input by the intensified South Asian Proto-Monsoon, which also helped cause more reducing conditions in the distal slope. Moreover, increased nutrient level facilitated the growths of calcareous algae and sponges, while it was not favorable for coral development. The elevated nutrient level, higher sea level, and monsoon-induced current contributed to the backstepping of the outer margin during the late Burdigalian. Our study shows an example on how a tropical carbonate platform evolved in response to the interplay of sea-level and paleoclimatic conditions. Findings are expected to be applicable to other tropical carbonate platforms. [ABSTRACT FROM AUTHOR]

The composition of coral-reef sediments is highly variable across space and time, and differences in the life histories of the dominant calcifying organisms on reefs contribute to the heterogeneity of reef sediments. Previous studies have suggested that variations in coral-reef bioerosion can influence spatial and temporal variations of sedimentary assemblages: elevated erosion rates of dead coral skeletons can trigger a pulse of coral-derived sediments and cause a shift in the dominance of sedimentary grains from coralline algae, such as Halimeda, to coral. We assessed the variability of the sedimentary composition and bioerosion rates of reefs at different spatial scales to determine the association between these two variables. We surveyed the benthic assemblages on reefs exhibiting different ecological states and collected samples of the associated sediments. We calculated the carbonate budget for each site and compared their variability at different hierarchical levels to the variability of their respective sedimentary assemblages. At the scale of sites (1–10 km), Halimeda cover was a significant predictor of the relative abundance of Halimeda grains. Both the relative abundance of coral grains and reef bioerosion rates varied significantly at the scale of locality (tens to hundreds of km), with high abundances of coral grains in the sediments coinciding with high rates of bioerosion. The main drivers of bioerosion at our localities were parrotfish assemblages dominated by large size classes of excavating species such as Sparisoma viride. Reef sediments may reflect the gross degree of bioerosion pressure that reefs experience, and historical changes in bioerosion rates could potentially be assessed by examining the sediments across temporal scales. [ABSTRACT FROM AUTHOR]

Benthic organisms typically possess a planktonic propagule stage in the form of larvae or spores, which enables them to spread over large distances before settlement, and promotes tight pelago-benthic coupling. However, factors driving dispersal and epibenthos recruitment in shallow hard-bottom Arctic communities are poorly known. We therefore conducted a year-round in situ colonization experiment in Isfjorden (Svalbard), and found out that variation in early-stage epibenthic assemblages was explained by the combination of: abiotic (45.9%) and biotic variables (23.9%), and their interactions (30.2%). The upward-facing experimental plates were dominated by coralline algae, and this is the first study showing that at high latitudes coralline algae Lithothamnion sp. settle in high numbers on available substrates during the polar night in winter. The downward-facing plates, which had much less exposure to light, contained more diverse organisms, with a predominance of polychaetas and bryozoans. However, in summer, the barnacle Semibalanus balanoides outcompeted all the other recruits, as a result of massive occurrence of meroplanktonic Cirripedia larvae, triggered by the phytoplankton bloom. In conclusion, the rate and success of epibenthic settlements were dependent mostly on light availability and temperature, suggesting that larval settlement will be impacted by global warming with some taxa benefitting, while others losing. [ABSTRACT FROM AUTHOR]

Although ~ 20% of global carbonate production occurs on extra-tropical carbonate depositional systems, our understanding of these environments still lags behind that of tropical ones. The Maltese shelf in the central Mediterranean offers an opportunity to study in situ facies distribution and the factors controlling it in a light-dominated setting. The investigated region of the Maltese shelf visually exhibits three main depositional environments: seagrass meadows, sand flats and rhodolith and maerl beds. While visually distinctive, the grain composition of the sediments does not provide a clear differentiation of the three environments but rather a gradient. This gradient is marked by increasing grain size with water depth, a transition from green to red calcareous algae and an increase in the fraction of low magnesium calcite of total carboantes. While some of these features can be explained by changes in light availability, other factors are also in play. Baffling by seafloor vegetation and currents, storms and internal waves inducing sediment reworking appear to play important roles in governing the sediment texture and composition across the Maltese shelf. The role of seagrass meadows in regulating production and accumulation rates of carbonates appears to be of greater importance in Mediterranean C-type carbonate factories than in southern Atlantic ones and this could be an important marker to identify them in the geological record. [ABSTRACT FROM AUTHOR]

The taxonomic composition, structure, and distribution patterns of the macrobenthos associated with Corallium rubrum were studied along the coast of Taranto (Ionian Sea), together with the main features of their red coral population. Underwater video transects were performed by professional divers at three sites in correspondence with coralligenous formations at depths from 50 to 65 m. The results revealed a patchy distribution of red coral, with colonies predominantly located in cavities on sub-vertical cliffs and large boulders. Biometric analysis indicated that young colonies predominated at all sites, while older colonies were lacking, likely because of illegal harvesting. The lower density values were recorded at S1, while S2 and S3 presented higher values. A total of 76 taxa were recorded. S1, the shallowest site, showed a prevalence of calcareous algae, while S2 and S3 showed a greater abundance of filter-feeding invertebrates (Porifera and Cnidaria) with the highest presence of Porifera at S3. The results emphasize the heterogeneity of the macrobenthos together with the high vulnerability of the red coral population, highlighting the necessity of site-specific conservation strategies to contribute to the conservation and management of benthic ecosystems in the northern Ionian Sea. [ABSTRACT FROM AUTHOR]

Neogoniolithon is a widespread genus of non‐geniculate coralline algae in the Mediterranean Sea. Three vaguely differentiated species have been reported in the region. This study examined the diversity of Neogoniolithon in the Mediterranean by inferring phylogenies using psbA and COI‐5P markers, applying delimitation algorithms and comparing morpho‐anatomies of putative species. In contrast to previous reports, 13 species were delimited from the Mediterranean in two distant clades. Initial observations suggested that tetrasporangial conceptacle size might be used to separate the two clades. Only three species showed fruticose morphologies. Further morpho‐anatomical differentiation was difficult. One species included Mediterranean, Pacific and Atlantic samples, while three other species occurred in the Mediterranean and the Canary Islands. The global tree revealed that most species were geographically restricted. Crypticity in multiple lineages implied a much higher diversity than currently reported, even lacking samples from the eastern Mediterranean. Only sequence data can be used to identify these cryptic lineages. High endemism emphasizes the importance of conservation of coralline algal bioconstructions to prevent extinctions. The presence of cryptic diversity also invites a reassessment of the knowledge on species distributions that are important in conservation planning and management. [ABSTRACT FROM AUTHOR]

Algae mostly occur either as unicellular (microalgae) or multicellular (macroalgae) species, both being uninucleate. There are important exceptions, however, as some unicellular algae are multinucleate and macroscopic, some of which inhabit tropical seas and contribute to biocalcification and coral reef robustness. The evolutionary mechanisms and ecological significance of multinucleation and associated traits (e.g., rapid wound healing) are poorly understood. Here, we report the genome of Halimeda opuntia, a giant multinucleate unicellular chlorophyte characterized by interutricular calcification. We achieve a high-quality genome assembly that shows segregation into four subgenomes, with evidence for polyploidization concomitant with historical sea level and climate changes. We further find myosin VIII missing in H. opuntia and three other unicellular multinucleate chlorophytes, suggesting a potential mechanism that may underpin multinucleation. Genome analysis provides clues about how the unicellular alga could survive fragmentation and regenerate, as well as potential signatures for extracellular calcification and the coupling of calcification with photosynthesis. In addition, proteomic alkalinity shifts were found to potentially confer plasticity of H. opuntia to ocean acidification (OA). Our study provides crucial genetic information necessary for understanding multinucleation, cell regeneration, plasticity to OA, and different modes of calcification in algae and other organisms, which has important implications in reef conservation and bioengineering. [ABSTRACT FROM AUTHOR]

ABSTRACT Coastal algal reef ecosystems, which are formed by the skeletal carbonate of crustose coralline algae (CCA), provide vital habitats for a diverse range of marine organisms and serve as valuable archives of long‐term environmental data. Despite the importance of these reef ecosystems, there is currently a lack of available information regarding the accretion rates of CCA in subtropical intertidal zones in the Taoyuan algal reef. We measured the vertical accretion and horizontal growth of CCA cultured in two aquaculture tanks over a 9‐month period. The vertical accretion and horizontal growth rate of CCA was approximately 0.29–0.43 and 5.5 μm·day−1 (the extrapolated annual value is equivalent to 0.11–0.16 and 2.0 mm·year−1, respectively). Newly colonized CCA had faster horizontal growth of approximately 110 μm·day−1 (equivalent to 40.2 mm·year−1). These results highlight the slow and gradual process of algal reef ecosystem formation in the subtropical intertidal zones. The CCA had a faster lateral growth rate as seen in the newly settled CCA. These findings contribute to our understanding of the overall growth dynamics of CCA. [ABSTRACT FROM AUTHOR]

ABSTRACT Rhodolith beds are diverse and globally distributed habitats. Nonetheless, the role of rhodoliths in structuring the associated species community through a hierarchy of positive interactions is yet to be recognised. In this review, we provide evidence that rhodoliths can function as foundation species of multi‐level facilitation cascades and, hence, are fundamental for the persistence of hierarchically structured communities within coastal oceans. Rhodoliths generate facilitation cascades by buffering physical stress, reducing consumer pressure and enhancing resource availability. Due to large variations in their shape, size and density, a single rhodolith bed can support multiple taxonomically distant and architecturally distinct habitat‐forming species, such as primary producers, sponges or bivalves, thus encompassing a broad range of functional traits and providing a wealth of secondary microhabitat and food resources. In addition, rhodoliths are often mobile, and thus can redistribute associated species, potentially expanding the distribution of species with short‐distance dispersal abilities. Key knowledge gaps we have identified include: the experimental assessment of the role of rhodoliths as basal facilitators; the length and temporal stability of facilitation cascades; variations in species interactions within cascades across environmental gradients; and the role of rhodolith beds as climate refugia. Addressing these research priorities will allow the development of evidence‐based policy decisions and elevate rhodolith beds within marine conservation strategies. [ABSTRACT FROM AUTHOR]

Two sediment sections are investigated at Cape Arkhangelos, island of Rhodes, where Pleistocene marine sediments crop out in horsts and grabens of a Mesozoic basement. There, hemipelagic sediments characterized by upper bathyal communities are atypically mixed with much shallower faunal components because they were deposited close to rugged coastal landforms. Biostratigraphic analyses show that the sections were deposited between 1.8 and 0.9 Ma, and between 1.8 and 1.6 Ma, respectively. By combining the planktonic/benthic foraminiferal ratio with 31 bathymetric indicators chosen among extant species of benthic foraminifera, mollusks, and bryozoans, we show that relative sea-level fluctuations can be reconstructed in these atypical settings despite the proximity of steep slopes that favored transportation of allochthonous fauna. The shallow-water components (including gravels and calcareous algae) were transported downslope by the combined action of gravity, currents, and tectonic disturbance that promoted drowning (with a maximum flooding recorded at ca. 1.7 Ma) and then uplift of fault-bounded paleovalleys that formed during the Early Pleistocene. Abrupt facies changes and age differences between sections have been triggered by the irregular paleotopography of the Mesozoic basement, which fostered differential depositional settings, with outer to middle neritic deposits above the horsts and upper bathyal deposits in paleovalleys. [ABSTRACT FROM AUTHOR]

The deployment of engineered substrates seeded with newly settled corals is a technique being developed to increase the numbers of juvenile corals on reefs with the goal of improving reef resilience in response to climate warming. Using a hierarchical sampling design, we explored the spatial scales at which seeded coral (spat) survival and growth varied in situ and investigated the environmental drivers of seeded spat success in the southern inshore Great Barrier Reef. After 10 months, variation in spat survival and size was greatest at the smallest spatial scale (1–2 m) (27 and 11% of variation, respectively), indicating the scale at which the main drivers of post‐settlement survival and growth are occurring. Crustose coralline algae (CCA) cover on seeding units prior to deployment was a significant driver of short‐ and long‐term spat survival (22% of variation). Survival of Acropora millepora and A. muricata spat did not differ according to benthic community variation. Increasing cover of branching Acropora corals was correlated with decreased survival and the size of Montipora aequituberculata spat, although CCA cover on plugs remained the most influential factor determining survival. Interspecific variation in spat survival and size and higher survival and size in the side‐facing orientation of the seeding units suggest natural variation in response to the seeding method, warranting further experiments to refine species selection and deployment methods prior to upscaling. High within‐site variation in seeded spat survival and size highlights the need for future studies of ecological factors driving post‐settlement mortality at fine spatial scales. [ABSTRACT FROM AUTHOR]

This study examines the importance of both macroalgal heterogeneity and specific macroalgal species or morphotypes to nursery provision for juvenile sparids (Diplodus capensis and Sarpa salpa) in a shallow (< 2 m), sheltered rocky cove in warm-temperate Algoa Bay, South Africa. The rocky cove is comprised of a mosaic of two main benthic habitats; canopy-forming Plocamium corallorhiza beds on rocky outcrops and flat reef dominated by low growing red algae morphotypes. We assessed macroalgal communities and the trophic ecology (stomach contents and isotopes), abundance and size structure of D. capensis and S. salpa in the two different benthic habitats and the resources/food associated with the dominant macroalgae species/morphotypes. We found high densities of S. salpa and D. capensis, in both high profile reef (rocky outcrops) and low profile (flat) reef. Within this habitat mosaic resources (epiphytes and macroinvertebrates) were more abundant in the non-canopy forming low growing macroalgae (Laurencia spp. and coralline turf algae) and these algae were also assimilated in the diets of both sparids. The high abundance of both juvenile S. salpa and D. capensis in high profile and low profile reef, suggests that within this mosaic of habitats these species may be using canopy-forming algae in the high profile reef for shelter and non-canopy forming algae in both the high and low profile reef for food. This shows that macroalgal habitats comprising several morphotypes have the potential to support higher juvenile diversity and abundance through both food provision and shelter. [ABSTRACT FROM AUTHOR]

Papaya (Carica papaya L.) is a widely cultivated and consumed fruit. When forming papaya seedlings, the combination of the ideal substrate to obtain quality seedlings is essential. The objective of this study was to evaluate the effect of a combination of substrates formulated with coconut fiber and doses of calcareous algae on the initial growth of papaya seedlings (Carica papaya L.). The experimental design was completely randomized in a 3 × 5 factorial arrangement, with five replications. The treatments consisted of the following substrate formulations: full coconut fiber + Gypsum; coconut fiber powder + NPK (15-10-10); coconut fiber powder + Gypsum; and doses of calcareous algae (0, 15, 30, 45 and 60 mg dm−3) applied as cover. The plant height, stem diameter, leaf area, number of leaves, shoot dry mass, root length and dry mass, and relative chlorophyll content (Chlorophyll A and Chlorophyll B) at 40 days of application of calcareous algae were evaluated. Substrates formulated with coconut fiber powder plus gypsum associated with calcareous algae doses are a great alternative in the production of papaya seedlings, stimulating plant height, stem diameter, number of leaves, and root dry mass. [ABSTRACT FROM AUTHOR]

Rhodolith beds are one of the major marine coastal ecosystems. Knowing the spatial distribution, environmental characteristics and composition is not only scientifically pertinent but also crucial to allow comparisons in case of changes due to local and global anthropogenic pressures. With slow algal growth rates, high associated diversity and potential importance as nursery grounds, rhodolith beds are present along the Brazilian coast of the Southwest Atlantic Ocean. This study provides an updated map of shallow and mesophotic rhodolith distribution after a systematic literature review. The prevailing oceanographic conditions along most parts of the Brazilian coast render the environment suitable for the developing rhodolith beds (a total of 68 taxa in this review), with 63 taxa along the East Brazilian Shelf, seven taxa for the North Brazilian Shelf and 10 taxa in the South Brazilian Shelf. According to composition, shallow and mesophotic communities were more similar in each large marine ecosystem than among them. In addition to gaps in terms of distribution, there are uncertainties about the taxonomic composition of the rhodoliths, associated fauna and flora and oceanographic and geological characteristics of the bottoms, which call attention to the importance of further studies, mainly in the mesophotic. This review provides a more precise distribution of these habitats along the Brazilian coast of the Southwest Atlantic Ocean. It contributes to a more detailed taxonomic composition of calcareous algae in an extremely relevant marine ecosystem, which is crucial for many species, including the endemic kelp, Laminaria abyssalis. [ABSTRACT FROM AUTHOR]

Up to 85% of shellfish reefs have been lost worldwide, resulting in declining ecosystem services, and increasing restoration demand. However, more information regarding the conditions which maximise oyster settlement and growth is required to optimise restoration. We deployed oyster settlement tiles at 21 intertidal sites throughout Moreton Bay, Australia; a region where > 96% of rock oyster reefs are lost and demand for restoration is high. We quantified effects of variables describing the spatial (from GIS), local habitat (using quadrats and water quality measures), and oyster predator (using underwater videography) characteristics of sites on oyster density and size on tiles. Oyster density was highest at sites with intermediate predator abundance and temperature, highest nearby invertebrate cover, and low and high values of turbidity and nearby rock and algae cover. Conversely, oyster size was highest at sites with intermediate predator density, higher fish species richness and turbidity, and lowest temperatures. Together, this showed that optimal restoration requires sites with 22 to 23 °C average water temperatures, between 10 and 15 oyster predators, and either low (< 2 NTU) or high (> 6 NTU) turbidity levels. Notably, we observed multiple peaks for several variables, suggesting the potential presence of multiple cryptic oyster species on settlement tiles. We found that oysters shared preferred environmental conditions with polychaetes, coralline algae, and tunicates, and were more prevalent and abundant at sites with lower turf algae, barnacle, and mussel cover. Identifying environmental variables influencing oyster population distribution, settlement, and growth can guide the selection and approach of oyster restoration sites. [ABSTRACT FROM AUTHOR]

Simple Summary: Rumen buffers are included in ruminant diets to prevent the accumulation of excess acid in the rumen, which can lead to animal health issues and production losses. Laboratory methods to compare different rumen buffers are useful to select the optimal buffer for inclusion in ruminant diets. The influence of key method parameters such as buffer material, threshold pH and test duration are reported. The area under the titration curve was identified as the most sensitive measure of buffer performance. Current laboratory methods to assess the efficacy of rumen buffers do not correlate very well with actual rumen measurements. A new method to model an acidotic rumen provided results that were better related to in vivo data. The inclusion of rumen buffers in ruminant feeds has gained widespread adoption for the prevention of rumen acidosis, thereby avoiding the negative production and health consequences of low rumen pH and resulting in improved feed efficiency. Benchmarking and quality controlling the performance of rumen buffer materials is of significant interest to feed mills and end-user producers. The aim of this study was to evaluate, develop and optimise a laboratory protocol to consistently and robustly evaluate rumen buffering materials in order to predict their in vivo efficacy. Three different methods were evaluated for determining the buffering potential of carbonate buffer materials: (a) 2 and 8 h static pH, (b) 8 h fixed HCl acid load addition and (c) 3 h acidotic diet simulation using acetic acid. Buffer material, threshold pH, test duration and interactions between all three variables were significant (p < 0.001) in evaluating the performance of the buffer materials. The acidotic diet simulation was found to provide a different ranking of materials to the 8 h fixed HCl acid load methodology. The results highlight the importance of method selection and test parameters for accurately evaluating the potential efficacy of rumen buffer materials. [ABSTRACT FROM AUTHOR]

ABSTRACT The first record of the kelp species Phyllariopsis brevipes in the Campania Region (Tyrrhenian Sea, South Italy) is here reported. The species has been observed in October 2021 in four sites along Sorrento Peninsula and Capri Island coast during scuba diving surveys. P. brevipes grew on living thalli of crustose coralline algae from 32 up to 55 m depth, occasionally forming dense aggregations with a maximum cover of about 0.2 m2. The DNA barcoding analysis on the basis of the cox1 gene supported the identification, with 98.36% of similarity between the sample collected in this study (NCBI accession number: PP622796) and a sequence obtained from a specimen from Provence, Mediterranean France (NCBI accession number: GQ368264). The study area can be considered a stepping stone for the species dispersion. The occurrence of P. brevipes can be related to upwelling and good water quality and the monitoring of its health status might be a sentinel of environmental changes. [ABSTRACT FROM AUTHOR]

The Triassic carbonate deposits are widely distributed in North Dobrogea (SE Romania) mainly within the Tulcea Nappe. Within this structural unit, the carbonate facies reveals an eastward-westward transition from shallow-water to basin facies. The shallow-water limestones were studied in three areas (Murighiol-Dealul Duna, Dunavăţu de Sus and Enisala) in order to identify and describe the algal fl ora. In this paper we describe the assemblage of dasycladalean green algae. Thirteen species were identifi ed, out of which nine are also known from other parts of the Alpine-Carpathian or Dinaric areas (Macroporella alpina, Poncetella hexaster, Neophysoporella lotharingica, Ardeiporella cf. karrerioidea, Poikiloporella duplicata, Probolocuspis cf. hydrae, Salpingoporella sturi, S. cf. triasica and Clypeina besici). Three species are new (Pseudodiplopora ioanaletitiae n. sp., Julpiaella baltresi n. sp. and Acicularia claudiopolitana n. sp.) and one species (Ioanella dobrogiaca) was already the subject of a previous work. This is the richest assemblage of calcareous dasycladalean algae described so far from the Triassic of Dobrogea. In addition, the Clypeina besici-Poikiloporella duplicata association is also important for age constraints because it is characteristic for the Carnian stage. [ABSTRACT FROM AUTHOR]

Innovation in limpet production requires knowledge of the optimal qualities and limitations of the culture vessels. Two limpet species from Madeira fishery, Patella aspera and P. ordinaria, were used to evaluate the influence of culture vessel shape (microtubes, test tubes, centrifuge tubes, specimen cups, disposable cups, vials, flasks and beakers), composition (polypropylene and glass), volume (1.5 ml to 1.5 L) and stocking density on oocyte incubation and larval culture through nine assays. Moreover, three assays evaluated the use of microtubes and the isolation of trochophores, instead of pediveligers, for eventual settlement induction. The results showed effective hatching in most culture vessels regardless of composition or volume, except when the shape of the bottom caused oocyte clustering. Larval culture was not influenced by any variable under scrutiny (shape, composition, volume or rearing density). Microtubes were useful for settlement, while the placement of trochophores in the settling vessels, instead of pediveligers, proved inefficient and even led to failed cultures. The best settlement was obtained when the pediveligers were isolated from the water column of the beakers and transferred to clean vessels with renewed water and coralline algae as substrate. The current findings could be extrapolated to other marine invertebrates that share similar life stage requirements. [ABSTRACT FROM AUTHOR]

Sexual propagation of corals is a promising strategy for coral restoration, but one of the main challenges is the high mortality of coral spat due to competitive interactions with macroalgae during the early life history stages. Optimising the properties of settlement substrates such as material types and surface roughness has the potential to improve the survival of spat by limiting the recruitment and growth of macroalgae. In this study, we assessed the effects of modifying surface roughness across three different tile materials (alumina-based ceramic, calcium carbonate (CaCO3), and concrete) on the settlement success and post-settlement survivorship of Acropora kenti coral larvae in six mesocosm tanks, each with different established macroalgal communities. The macroalgal community compositions on the tiles were significantly different among material types, but not surface roughness, although the type and abundance of macroalgal species were heavily influenced by the established tank communities. Increasing surface roughness did not affect larval settlement success or spat survivorship. Substantially higher larval settlement density was found on concrete tiles (1.92 ± 0.10 larvae cm−2), but spat survival was the highest on CaCO3 tiles (73.4 ± 4.2% survived). Very strong competitive interactions were observed between spat and macroalgae, with overgrowth by the crustose coralline alga Crustaphytum sp. and the brown alga Lobophora sp. being the primary cause of spat mortality. Overall, when taking into account both settlement and survival rates, concrete was the best performing among the tile types tested here. [ABSTRACT FROM AUTHOR]

Algal ridges are protective features for coral reefs that form through the accretion and encrustation of reef rubble and debris by crustose coralline algae (CCA) and processes of diagenetic cementation. Carbonate precipitation and dissolution dynamics on and within algal ridge frameworks are poorly understood. We studied the surface and subsurface geochemistry of the algal ridge framework at One Tree Island, Australia. Measurable quantities of hydrogen sulphide were detected in most porewater samples collected from bores, indicating a largely anoxic ridge framework. Total alkalinity (TA) and pH measurements indicate that the precipitation of carbonate minerals within the interior of the ridge framework occurs under largely anoxic conditions and is likely to be driven by TA changes associated with sulphate-reducing bacteria. Modelling of porewater hydrogen sulphide concentrations in combination with TA and dissolved inorganic carbon (DIC) indicates anoxic respiration processes produce alkalinity within the algal ridge framework. However, significantly more TA is removed via the precipitation of mineral carbonate, resulting in porewater TA concentrations falling below the open seawater values. The precipitation of mineral carbonate also lowers interstitial water pH, such that pH changes are not solely from organic carbon diagenesis. The simultaneous precipitation and dissolution of carbonate minerals within the algal ridge framework are key to forming and cementing algal ridges, which are important physical protective features for coral reefs. [ABSTRACT FROM AUTHOR]

Mesophotic Coral Ecosystems (MCEs) represent unique ecological habitats that range from 30 to 150 m deep, harbouring phylogenetically distinct species and offering refuge for many taxa during times of environmental stress. Yet owing to inaccessibility of ecosystems at these depths, most MCEs remain unexplored, with quantifications of ecological communities in these habitats lacking across many regions. Here, using open- and closed-circuit technical diving, we quantified benthic and fish community composition at four mesophotic reef sites (45 m depth) in Grand Cayman. We show significant differences in benthic community composition over a small spatial scale driven by disparate coverage of sponges, crustose coralline algae, and sand/rubble, yet consistent patterns of macroalgal dominance representing >50% coverage at each site and low hard coral cover at an average of 2.4%. Reef fish species richness, biomass, and density was consistent across sites, however the relative contribution of individual species to community composition differed significantly. Macrocarnivores were found to be the dominant contributors to biomass, with invertivores the most speciose, and omnivores and planktivores at the highest densities, consistent with previous descriptions of mesophotic fish assemblages in other regions. Similarly, the low hard coral cover and high macroalgae and sponge cover of the benthic communities also appear ecologically similar to several described mesophotic reefs yet is not uniform across the Caribbean. The ecological organisation of Grand Cayman's MCEs may result from a variety of factors such as isolation from other major land masses, geology, local geography, and anthropogenic activity at both the local and global scale and highlight the importance of continued exploration and documentation of MCE communities. [ABSTRACT FROM AUTHOR]

SUMMARY: Lithophyllum is a cosmopolitan coralline algal genus with 12 species currently recognized in Japan based on modern morpho‐anatomical taxonomic concepts primarily characterized by having uniporate tetrasporangial and bisporangial conceptacles, the presence of secondary pit‐connections between cells of adjacent filaments and a dimerous thallus construction with a single basal layer of predominantly non‐palisade cells. In the present study, we describe Lithophyllum nagaokaense sp. nov. based on a combination of molecular and morpho‐anatomical data of specimens from the temperate waters of Japan. The new species forms both attached epilithic thalli and free‐living rhodoliths. Phylogenetic analyses of psbA, rbcL and COI markers resolved L. nagaokaense as an independent species. Morpho‐anatomically, L. nagaokaense resembles Lithophyllum johansenii, originally described from Australia, but distinguished from the latter by the absence of enlarged angular cells occluding pore canals of tetrasporangial conceptacle chambers. Lithophyllum nagaokaense shared a fruticose morphology with Lithophyllum kaiseri, Lithophyllum kuroshioense, Lithophyllum neo‐okamurae, Lithophyllum okamurae, and Lithophyllum pygmaeum from Japan. Of these, L. nagaokaense is the most similar to L. neo‐okamurae in having attached and free‐living thalli with encrusting and warty to lumpy growth forms bearing knobby protuberances that are dichotomously branched or anastomosing. The new species is distinct from other Japanese fruticose species collectively by five tetrasporangial conceptacle chamber characters and the absence of trichocytes. A taxonomic key for identifying Japanese fruticose species is provided. This is the fifth Lithophyllum species and the third rhodolith‐forming species verified by DNA sequencing to be found in Japan. [ABSTRACT FROM AUTHOR]

Coral reefs off the coast of the Republic of Sudan are still considered to be among the most pristine reefs in the central Red Sea. The complex coastal fringing reefs, offshore banks, and shoals of Dungonab Bay in the north and Sanganeb atoll situated further to the south, about 23 km off the Sudanese mainland coast, were inscribed on the UNESCO World Heritage List in 2016. Due to their remote location and limited access, monitoring of the status of the reefs has been sporadic. Here, we present the results of a repeated large area photomosaic survey (5 m × 5 m plots) on the Sanganeb atoll, first established and surveyed in 1980, and revisited in 1991 and most recently in 2019. The 2019 survey recovered and reinstated the four original monitoring plots. Evaluation of photographic and video records from one photomosaic plot on the seaward slope of the atoll revealed general continuity of the overall community structure and composition over 39 years. Individual colonies of Echinopora gemmacea and Lobophyllia erythraea were recorded in the exact same positions as in the 1980 and 1991 plots. The genera Acropora and Pocillopora remain dominant, although in altered proportions. Shifts in composition were detected at the species level (e.g., increase in Pocillopora verrucosa, Stylophora pistillata, Acropora hemprichii, Dipsastraea pallida, and Echinopora gemmacea, decrease in Acropora cytherea and A. superba), in addition to changes in the extent of uncolonized substrate (e.g., increase from 43.9% in 1980 to 52.2% in 2019), and other scleractinian, hydrozoan, and soft coral living cover. While the temporal resolution only includes three sampling events over 39 years (1980, 1991, 2019), this study presents one of the longest time series of benthic community surveys available for the entire Red Sea. A semi-quantitative estimate of vertical reef growth in the studied test plot indicates a reduction in net accretion rates of more than 80%, from 2.27 to 2.72 cm/yr between 1980 and 1991 to 0.28–0.42 cm/yr between 1991 and 2019. We carefully conclude that the changes observed in the coral community in the plot in 2019 (Acropora–Pocillopora shift, increase in Montipora and calcareous algae) are representative of impacts at the community level, including rising sea surface temperatures and recent bleaching events. [ABSTRACT FROM AUTHOR]

Specimens attributed to the genus Lithophyllum were collected during multiple surveys conducted along the Brazilian coast. These specimens were studied using DNA sequences from three molecular markers (COI5P, psbA, rbcL) and comparative morphoanatomical analyses. This approach revealed eight distinct, well-supported lineages: two currently known species, Lithophyllum atlanticum and L. kaiseri; four new species, L. brasiliense sp. nov., L. pseudomargaritae sp. nov., L. solis sp. nov. and L. tomitae sp. nov.; and two additional lineages that remain unresolved as the available data were incongruent or insufficient. Lithophyllum pseudomargaritae was morpho-anatomically similar but distantly related to sequences from the type locality of specimens morphologically identified as L. margaritae. This study confirms the occurrence of cryptic/pseudocryptic coralline diversity in the Brazilian flora. [ABSTRACT FROM AUTHOR]

Marine heatwaves (MHWs) caused by anthropogenic climate change are becoming a key driver of change at the ecosystem level. Thermal conditions experienced by marine organisms across their distribution, particularly towards the equator, are likely to approach their physiological limits, resulting in extensive mortality and subsequent changes at the population level. Populations at the margins of their species' distribution are thought to be more sensitive to climate-induced environmental pressures than central populations, but our understanding of variability in fitness-related physiological traits in trailing versus leading-edge populations is limited. In a laboratory simulation study, we tested whether two leading (Iceland) and two trailing (Spain) peripheral populations of the intertidal macroalga Corallina officinalis display different levels of maximum potential quantum efficiency (Fv/Fm) resilience to current and future winter MHWs scenarios. Our study revealed that ongoing and future local winter MHWs will not negatively affect leading-edge populations of C. officinalis, which exhibited stable photosynthetic efficiency throughout the study. Trailing edge populations showed a positive though non-significant trend in photosynthetic efficiency throughout winter MHWs exposure. Poleward and equatorward populations did not produce significantly different results, with winter MHWs having no negative affect on Fv/Fm of either population. Additionally, we found no long-term regional or population-level influence of a winter MHWs on this species' photosynthetic efficiency. Thus, we found no statistically significant difference in thermal stress responses between leading and trailing populations. Nonetheless, C. officinalis showed a trend towards higher stress responses in southern than northern populations. Because responses rest on a variety of local population traits, they are difficult to predict based solely on thermal pressures. [ABSTRACT FROM AUTHOR]

Several studies have inferred the ecological significance regarding the morphometrics of Aristotle's lantern and the mechanical properties of magnesium in echinoid teeth. This study attempts to combine these aspects, connecting them to the trophic habits of three native and an invasive echinoid in the Eastern Mediterranean Sea. Spatiotemporal data from the central and southern Aegean Sea were obtained, regarding the relative size of lanterns and demi‐pyramids of Arbacia lixula, Paracentrotus lividus, Sphaerechinus granularis, and the invasive echinoid Diadema setosum and the Mg/Ca ratios of four zones on the tooth cross‐section. Since environmental factors affect the examined factors, data for temperature, salinity, and concentration of chlorophyll‐a were included in a principal component analysis. A. lixula and P. lividus presented intraspecific differences in the relative size of the lantern and demi‐pyramid, while S. granularis and D. setosum exhibited variation in the elongation index. Differences in the Mg/Ca ratios were observed for all species although in different zones. Temperature appears to be related to all Mg/Ca zones except for the stone part, while the elongation index showed an inverse trend to all other morphometric parameters. The results of the PCA for the four species on the spatiotemporal level exhibited a distinction of individuals with season but not species, except for A. lixula, an omnivore with a carnivorous tendency, which was clearly separated from the herbivorous species. Using hierarchical clustering on the principal components it was evident that the three native species occupy different clusters, but when D. setosum was added, it shared the same cluster with S. granularis. This might infer similar feeding preferences, specifically for coralline algae, which might lead to a swift in the ecological equilibrium in regions, where D. setosum is found, either by affecting habitat type, or by restricting the distribution of S. granularis as was previously observed with Diadema africanum. [ABSTRACT FROM AUTHOR]

Whilst the importance of foundation species for biodiversity conservation has been largely acknowledged (e.g., coral and bivalve reefs, seagrass, kelp and rhodolith beds), the role of their associated species as secondary habitat engineers has just begun to be appreciated. Here, we evaluated whether secondary engineering of rhodolith beds by the sand tilefish Malacanthus plumieri influences the composition and β-diversity of benthic macroinvertebrates and reef fish assemblages. Our findings indicate that, by selecting, relocating, and rearranging rhodoliths into mounds, M. plumieri creates a distinctive habitat for macroinvertebrates and fishes. M. plumieri mounds increase fish abundance by 57% in rhodolith beds, with an 82% species turnover rate between mounds and non-mounded areas. In contrast, the macroinvertebrates in M. plumieri mounds are largely a subset of the species from non-mounded areas, with an 86% species nestedness rate. Despite decreasing the abundance of macroinvertebrates in the mounds by half, M. plumieri increases the heterogeneity and structural complexity of rhodolith beds, affecting the composition of associated fish assemblage at a larger spatial scale. Our results suggest that, by increasing the structural complexity of rhodolith beds and shaping their associated biodiversity, the abundance of M. plumieri mounds could be a useful proxy to define priority areas for conservation across the South Atlantic rhodolith beds, especially in the light of ongoing impacts related to offshore oil exploitation, overfishing and carbonate mining. [ABSTRACT FROM AUTHOR]

Zooxanthellate corals are Iran's most abundant macrofossils in the Oligocene-early Miocene Qom Formation deposits in the NE margin of the Tethyan Seaway. Yet, basic knowledge about the diversity of these organisms and their paleoecology is still scarce. In this paper late Rupelian-Chattian coral data from three exposed sections in the northwestern Jazmurian Lake, SE Iran, as the southeasternmost outcrops of the Qom Formation, are analyzed in terms of diversity and paleoecology. The coralline red algae and larger benthic foraminiferal assemblages associated with the corals have also been used to infer the paleoenvironmental and paleoecological conditions. The following coral genera were recognized: Leptoria, Caulastraea, Hydnophora, Astreopora, Plesiastraea, Thegioastraea, Porites, Goniopora, Platycoenia, Acropora, Tarbellastraea, Favites, Heliastraea, Stylocoenia, Ceratotrochus. The high abundance of z-corals, larger benthic foraminifera (LBF), and coralline red algae demonstrate that the deposition took place in tropical-subtropical warm waters mainly within the euphotic to the mesophotic zones. The presence of various coral fabrics including pillarstone, domestone, and rudstone allowed to infer high to moderate hydrodynamic energy in the studied sections. As well, given the interactions among corals, filter-feeders, green and red algae, bioeroders, and the surrounding environment, it seems that oligotrophic to slightly mesotrophic conditions also had prevailed in the studied area. [ABSTRACT FROM AUTHOR]

Interactions such as mutualism and facilitation are common in ecosystems established by foundation species; however, their outcomes vary and show conditionality. In a Mexican Caribbean Bay, a seagrass-coralline algae (rhodoliths) mutualism protects the seagrass Thalassia testudinum from green turtle overgrazing. We postulate that the state of the seagrass meadow in this bay depends on the strengths of the interactions among seagrasses, green turtles, and coralline algae. Spatio-temporal changes through satellite imagery showed rhodolith bed developed rapidly from 2009 (undetected) to 2016 (bed of 6934 m2). Typically, such rapid expansion of the rhodoliths does not occur in seagrass meadows. An in situ growth experiment of coralline algae showed that a combination of reduction in light and wave movement (usual in dense seagrass meadows) significantly reduced their growth rates. In the rhodolith beds, the growth rates of the coralline algae Neogoniolithon sp. and Amphiroa sp. were high at 9.5 mm and 15.5 mm per growth tip y−1, respectively. In a second experiment, we found lower mortality in coralline algae within a rhodolith bed compared to algae placed outside the bed, likely explained by the reduced resuspension that we found in a third experiment, and this positive feedback may explain the high population increase in the rhodoliths, once established when the turtles grazed down the seagrass canopy. Therefore, the grazing-protection mutualism between seagrasses and coralline algae is thus conditional and came into existence under a co-occurrence of intensive grazing pressure and rapid population growth of coralline algae facilitated by positive feedback from increased growth and reduced sediment resuspension by the dense rhodolith bed. [ABSTRACT FROM AUTHOR]

Crustose coralline algae (CCA) are a highly diverse group of habitat‐forming, calcifying red macroalgae (Rhodophyta) with unique adaptations to diverse irradiance regimes. A distinctive CCA phenotype adaptation, which allows them to maximize photosynthetic performance in low light, is their content of a specific group of light‐harvesting pigments called phycobilins. In this study, we assessed the potential of noninvasive hyperspectral imaging (HSI) in the visible spectrum (400–800 nm) to describe the phenotypic variability in phycobilin content of an Antarctic coralline, Tethysphytum antarcticum (Hapalidiales), from two distinct locations. We validated our measurements with pigment extractions and spectrophotometry analysis, in addition to DNA barcoding using the psbA marker. Targeted spectral indices were developed and correlated with phycobilin content using linear mixed models (R2 = 0.64–0.7). Once applied to the HSI, the models revealed the distinct phycoerythrin spatial distribution in the two site‐specific CCA phenotypes, with thin and thick crusts, respectively. This study advances the capabilities of hyperspectral imaging as a tool to quantitatively study CCA pigmentation in relation to their phenotypic plasticity, which can be applied in laboratory studies and potentially in situ surveys using underwater hyperspectral imaging systems. [ABSTRACT FROM AUTHOR]

Phymatolithon acervatum is an encrusting, non-geniculate coralline alga from South Africa. While morpho-anatomical details of the species are well documented, no genetic analyses have been performed on P. acervatum. Here, we analyzed rbcL and psbA gene sequences, and they showed that two species were passing under the name Phymatolithon acervatum in South Africa. A partial rbcL sequence from the lectotype of Lithothamnion acervatum, basionym of P. acervatum, showed to which species the specific epithet applies, and furthermore that both species belong in Phymatolithopsis. We transfer Phymatolithon acervatum to Phymatolithopsis, as Phymatolithopsis acervata comb. nov., and propose Phymatolithopsis roseola sp. nov. These species overlap in morpho-anatomy, habitat and distribution and can only be distinguished based on DNA sequences. Previous misinterpretations of conceptacle development are corrected for species of Phymatolithopsis. The main character used to define the family Mesophyllumaceae is shown to have arisen several times in independent lineages in the order Hapalidiales. At present, only one family, Hapalidiaceae, thus merits recognition in the Hapalidiales. [ABSTRACT FROM AUTHOR]

The ecological importance of rhodolith beds stems from their role as structurally complex three-dimensional habitat formed by free-living red calcareous algae. Their structural singularity is due to the great variety of complex and branching morphologies exhibited by rhodoliths that create interstitial spaces and increase their surface area. This increases the ecological niches for cryptofauna and provide refuge for a high number of organisms, which is why rhodolith beds are considered biodiversity hotspots. In this work, we studied a rhodolith bed located in the Menorca Channel, formed by several species of red calcareous algae that exhibit a great variety of morphologies and form an extensive and heterogeneous habitat. This study explored the morphological diversity of the rhodolith bed, comparing the 'Core Habitat' (within the center of the bed with the highest densities of rhodoliths) with the boundaries or 'Adjacent Habitat' where rhodolith density was lower. Our results show that all rhodolith growth forms (branched, pralines and boxwork) in the Core Habitat had higher interstitial space and were larger than the ones from adjacent zones. Moreover, we explored the three-dimensional techniques to study the morphological characteristics that have historically been studied in two dimensions. This study contributes to the knowledge of morphological diversity in well-preserved rhodolith beds from continental shelves in the western Mediterranean Sea and reinforces the use of three-dimensional measurements, specifically the interstitial space of branched rhodoliths, to provide more accurate data on habitat complexity. [ABSTRACT FROM AUTHOR]

• First record of Miocene large-sized vertebrate coprolites from the western India. • Geochemical analyses confirm phosphatic character of ichnofossils. • Biotic inclusions confirm omnivorous diet of the chelonian producer. • Overall data suggest coprolites were deposited in coastal marine settings. In this paper, we provide the first data on large (cm-sized) coprolites (represented by three morphotypes) comprising a rare occurrence of eight specimens from a total of three vertebrate-bearing horizons identified within the Early Miocene (Aquitanian) Khari Nadi Formation and Middle Miocene (Burdigalian-Langhian) Chassra Formation, Kutch Basin, western India. The geochemical data confirm the phosphatic character of the investigated ichnofossils. The dominance of partly digested bone matter and presence of plant remains in all the three coprolite morphotypes reflects the omnivorous diet of the producers, which were most likely chelonians. The occurrence of an inclusion (in a coprolite specimen recorded in this study) showcasing an ultrastructure similar to mammalian dental enamel is a rarity in Neogene coprolite records. Additional biotic inclusions observed in the investigated coprolites include ostracods (assigned to genera Paractinocythereis, Hermanites, and Propontocypris); large planispiral benthic foraminifera including the genus Quinqueloculina ; uniserial and biserial benthic foraminifera belonging to genus Textularia ; marine calcareous algae genus Actinoporella ; chrysophytes (resting spores or cysts of planktonic algae); sponge spicules (represented by the morphotypes Acanthoxea and Strongyle); freshwater diatom genus Aulacoseira ; unidentified fungal remains; and phytoliths. Taken together, the biotic and abiotic (e.g., pyrite) inclusions, geochemical data and associated microbiota suggest that these ichnofossils were deposited in a dominantly coastal marine (intertidal) setting linked to a lacustrine/palustrine environment. [ABSTRACT FROM AUTHOR]

Macroalgae populations are influenced by various factors that define their spatial and temporal distribution in different habitats and regions. In Mexico, studies addressing the abundance and diversity of macroalgae communities related to environmental factors are scarce. The objective is to determine the spatio-temporal variation of the structure of the community of seaweeds in Xpicob and Villamar, Campeche, during three climatic seasons. Sampling took place during each season using transects and quadrants; additionally, the type of substrate, water temperature, transparency, depth, salinity, and dissolved oxygen, were recorded. The total richness was 74 taxa, corresponding to three classes: Phaeophyceae (3), Florideophyceae (36), and Ulvophyceae (35). Filamentous algae dominate in species richness in the intertidal zone at low depths, while fleshy and calcareous algae predominate in number and biomass in the subtidal zone at higher depths (60–200 cm). Twenty-eight species were common to both sites; meanwhile, 46 taxa were exclusive of specific sites, including 13 found exclusively in Xpicob and 33 in Villamar. The most favorable climatic season for the macroalgae located in Xpicob was the winter rain. For the macroalgae community in Villamar, the most favorable climatic season was the dry. These differences are likely attributed to the predominant environmental and physicochemical characteristics of each site. [ABSTRACT FROM AUTHOR]

Background and Aims Maerl-associated communities have received considerable attention due to their uniqueness, biodiversity and functional importance. Although the impacts of human activities are well documented for maerl-associated macrofauna, the spatio-temporal variations of macroalgae have comparatively been neglected, and the drivers that influence their dynamics are poorly known. We investigate the links between maerl-associated macroalgal communities, anthropogenic pressures and environmental conditions, and hypothesize that sites under human pressure would exhibit different dynamics when compared to reference sites. Methods To better understand community variation through space and time, four subtidal maerl beds under different pressures were consistently monitored over one year in the bay of Brest, Brittany, France. Both macroalgae community monitoring and environmental data were acquired through field sampling and available models. Key Results Higher macroalgal biomass was observed within eutrophic sites, especially in summer (more than ten times higher than in the Unimpacted site), caused by free-living forms of opportunistic red macroalgae. The Dredged site also exhibited distinct macroalgal communities during summer from the Unimpacted site. Nutrient concentrations and seasonality proved to be key factors affecting the macroalgal community composition, although dredging and its effects on granulometry also had a strong influence. Over the long term, fewer than half of the species identified during historical surveys were found, indicating major temporal changes. Conclusions Human pressures have strong impacts on maerl-associated macroalgal communities. Nutrient concentrations and dredging pressure appear as the main anthropogenic factors shaping maerl-associated macroalgal communities. Additionally, our results suggest historical changes in maerl-associated macroalgal communities over 25 years in response to changes in local human pressure management. This study suggests that maerl-associated macroalgal communities could be used as indicators of anthropogenically driven changes in this habitat. [ABSTRACT FROM AUTHOR]

Coral reef ecosystems are declining and may not recover under future climate scenarios without intervention. Seeding reefs with corals bred in aquaculture is a promising restoration intervention; however, early coral recruits (spat) are vulnerable to overgrowth by benthic algae and maximizing their survival is essential for the feasibility of large-scale breeding operations. This study investigated the optimal light quality and intensity for spat survival and growth in the presence of algal communities typically used in coral aquaculture to induce larval settlement, but which might also outcompete spat and reduce survival during the grow-out period. Spat were exposed to two light spectra (blue and a full spectrum) at four light intensities (5–160 µmol m−2 s−1) over 12-week post-settlement. Survival was reduced under the highest intensity by nearly 40% compared to the lowest intensity. Light spectrum only affected survival at 60 µmol m−2 s−1—where survival was higher under blue compared to full spectrum light. Light treatments did not affect final spat size but spat were 33% smaller at the highest light intensity in weeks 6 and 8 due to overgrowth by crustose coralline algae (CCA), which was most abundant under these conditions. Low light intensity, on the other hand, favored green and brown algae, potentially due to their respective physiologies or less competition from crustose coralline algae. These results indicate that low light intensity presents several advantages for maintaining spat in coral aquaculture, including maximizing survival without significantly affecting growth, as well as minimizing husbandry and operating expenses. [ABSTRACT FROM AUTHOR]

Intraspecific and habitat-mediated responses to chemical cues play key roles in structuring populations of marine species. We investigated the behaviour of herbivorous-stage juvenile crown-of-thorns sea stars (COTS; Acanthaster sp.) in flow-through choice chambers to determine if chemical cues from their habitat influence movement and their transition to become coral predators. Juveniles at the diet transition stage were exposed to cues from their nursery habitat (coral rubble-crustose coralline algae (CCA)), live coral and adult COTS to determine if waterborne cues influence movement. In response to CCA and coral as sole cues, juveniles moved towards the cue source and when these cues were presented in combination, they exhibited a preference for coral. Juveniles moved away from adult COTS cues. Exposure to food cues (coral, CCA) in the presence of adult cues resulted in variable responses. Our results suggest a feedback mechanism whereby juvenile behaviour is mediated by adult chemical cues. Cues from the adult population may deter juveniles from the switch to corallivory. As outbreaks wane, juveniles released from competition may serve as a proximate source of outbreaks, supporting the juveniles-in-waiting hypothesis. The accumulation of juveniles within the reef infrastructure is an underappreciated potential source of COTS outbreaks that devastate coral reefs. [ABSTRACT FROM AUTHOR]

Marine habitat-forming species create structurally complex habitats that host macroinvertebrate communities characterized by remarkable abundance and species richness. These habitat-forming species also play a fundamental role in creating favourable environmental conditions that promote biodiversity. The deployment of artificial structures is becoming a common practice to help offset habitat loss although with mixed results. This study investigated the suitability of artificial flexible turfs mimicking the articulated coralline algae (mimics) as habitat providers and the effect of ocean acidification (OA) on early stage ecological communities associated to flexible mimics and with the mature community associated to Ellisolandia elongata natural turfs. The mimics proved to be a suitable habitat for early stage communities. During the OA mesocosms experiment, the two substrates have been treated and analysed separately due to the difference between the two communities. For early stage ecological communities associated with the mimics, the lack of a biologically active substrate does not exacerbate the effect of OA. In fact, no significant differences were found between treatments in crustaceans, molluscs and polychaetes diversity and abundance associated with the mimics. In mature communities associated with natural turfs, buffering capability of E. elongata is supporting different taxonomic groups, except for molluscs, greatly susceptible to OA. [ABSTRACT FROM AUTHOR]

A new calcareous alga is described from the Norian limestones of Lime Peak, Yukon, Canada. The algae-bearing limestoneswere formed in a low-energy environment below the storm wave base, as indicated by the abundance of carbonate mud. Clypeina? pamelareidae n. sp. usually appears in the form of separate laterals scattered in the sediment. The laterals are pyriform, with the tip slightly curved upwards. Sometimes they are arranged around a non-calcified axial cavity. The lack of calcification of the connection between themain axis and the laterals led to the detachment and scattering of the latter in the sediment. The shape of the laterals and their arrangement are reminiscent of the genus Clypeina (Michelin). Still, the lack of completely preserved specimens leads us to attribute itwith uncertainty to this genus. Almost certainly, the alga in question is individualised as a new distinct species, basically different from other Mesozoic or Cenozoic species of the genus, as well as from the only species of Clypeina known from the Triassic (Clypeina besici Pantić). [ABSTRACT FROM AUTHOR]

Ocean acidification (OA) is predicted to cause profound shifts in many marine ecosystems by impairing the ability of calcareous taxa to calcify and grow and by influencing the physiology of many others. In both calcifying and non-calcifying taxa, ocean acidification could further impair the ability of marine life to regulate internal pH and thus metabolic function and/or behaviour. Identifying tipping points at which these effects will occur for different taxa due to the direct impacts of ocean acidification on organism physiology is difficult because they have not adequately been determined for most taxa nor for ecosystems at higher levels. This is due to the presence of both resistant and sensitive species within most taxa. However, calcifying taxa such as coralline algae, corals, molluscs, and sea urchins appear to be most sensitive to ocean acidification. Conversely, non-calcareous seaweeds, seagrasses, diatoms, cephalopods, and fish tend to be more resistant or even benefit from the direct effects of ocean acidification, though the effects of ocean acidification are more subtle for these taxa. While physiological tipping points of the effects of ocean acidification either do not exist or are not well defined, their direct effects on organism physiology will have flow-on indirect effects. These indirect effects will cause ecological tipping points in the future through changes in competition, herbivory, and predation. Evidence for indirect effects and ecological change is mostly taken from benthic ecosystems in warm temperate–tropical locations in situ that have elevated CO 2. Species abundances at these locations indicate a shift away from calcifying taxa and towards non-calcareous taxa at high-CO 2 concentrations. For example, lower abundance of corals and coralline algae and higher covers of non-calcareous macroalgae, often turfing species, are often found at elevated CO 2. However, there are some locations where only minor changes or no detectable changes occur. Where ecological tipping points do occur, it is usually at locations with naturally elevated mean p CO 2 concentrations of 500 µ atm or more, which also corresponds to just under that concentration where the direct physiological impacts of ocean acidification are detectable in the most sensitive taxa in laboratory research (coralline algae and corals). Collectively, the available data support the concern that ocean acidification will most likely cause ecological change in the near future in most benthic marine ecosystems, with tipping points in some ecosystems as low as 500 µ atm p CO 2. However, further research is required to more adequately quantify and model the extent of these impacts in order to accurately project future marine ecosystem tipping points under ocean acidification. [ABSTRACT FROM AUTHOR]

The crustose coralline alga Lithophyllum stictiforme is an important reef builder, forming coralligenous concretions in the Mediterranean Sea. This algal species complex is composed of eight cryptic species (or clades). The objective of our study was to compare light-dependent physiological processes within and between the two most abundant cryptic species (C1 and C4) of L. stictiforme from the Bay of Marseille (France). Physiological rates of respiration, photosynthesis and calcification were measured using incubation chambers under various irradiance levels and in the dark during the summer period. We compared the physiology of the C1 and C4 cryptic species of L. stictiforme among three algal groups: C1 (the most common in the Marseille area) from 28 m depth, C4 from the same site and depth, and C1 from a deeper site at 45 m depth. We found both interspecific (between C1 and C4) and intraspecific (within C1) physiological differences. Photosynthetic parameters showed acclimation to light (or depth) with higher values of initial slope of photosynthetic light response curve (α) and lower values of saturating irradiance (Ek) and compensating irradiance (Ec) for C1 from 45 m than for C1 and C4 from 28 m depth. At the shallower depth, significant physiological differences were observed between C1 and C4 with a higher value of maximum rate of gross photosynthesis (Pg max) in C4, suggesting better ability to grow under high irradiance. Light and dark calcification rates differed only between C4 from 28 m and C1 from 45 m depth, being intermediate in C1 from 28 m depth. On a 24 h basis, diel net calcification rates were significantly higher in specimens from the shallower waters than from the deeper waters. Physiological differences suggest physiological plasticity within the regionally dominant cryptic species C1 and species-specific physiological traits between the cryptic species C1 and C4. Photosynthesis and calcification rates differ among Lithophyllum stictiforme cryptic species. The regionally dominant cryptic species exhibits light-dependent physiological plasticity. Physiological differences occur between cryptic species found in similar environments. [ABSTRACT FROM AUTHOR]

Rhodoliths built by crustose coralline algae (CCA) are ecosystem engineers of global importance. In the Arctic photic zone, their three‐dimensional growth emulates the habitat complexity of coral reefs but with a far slower growth rate, growing at micrometers per year rather than millimeters. While climate change is known to exert various impacts on the CCA's calcite skeleton, including geochemical and structural alterations, field observations of net growth over decade‐long timescales are lacking. Here, we use a temporally explicit model to show that rising ocean temperatures over nearly 100 years were associated with reduced rhodolith growth at different depths in the Arctic. Over the past 90 years, the median growth rate was 85 μm year−1 but each °C increase in summer seawater temperature decreased growth by a mean of 8.9 μm (95% confidence intervals = 1.32–16.60 μm °C−1, p <.05). The decrease was expressed for rhodolith occurrences in 11 and 27 m water depth but not at 46 m, also having the shortest time series (1991–2015). Although increasing temperatures can spur plant growth, we suggest anthropogenic climate change has either exceeded the population thermal optimum for these CCA, or synergistic effects of warming, ocean acidification, and/or increasing turbidity impair rhodolith growth. Rhodoliths built by calcitic CCA are important habitat providers worldwide, so decreased growth would lead to yet another facet of anthropogenic habitat loss. [ABSTRACT FROM AUTHOR]

Photoautotrophic marine ecosystems can lock up organic carbon in their biomass and the associated organic sediments they trap over millennia and are thus regarded as blue carbon ecosystems. Because of the ability of marine ecosystems to lock up organic carbon for millennia, blue carbon is receiving much attention within the United Nations' 2030 Agenda for Sustainable Development as a nature‐based solution (NBS) to climate change, but classically still focuses on seagrass meadows, mangrove forests, and tidal marshes. However, other coastal ecosystems could also be important for blue carbon storage, but remain largely neglected in both carbon cycling budgets and NBS strategic planning. Using a meta‐analysis of 253 research publications, we identify other coastal ecosystems—including mud flats, fjords, coralline algal (rhodolith) beds, and some components or coral reef systems—with a strong capacity to act as blue carbon sinks in certain situations. Features that promote blue carbon burial within these 'non‐classical' blue carbon ecosystems included: (1) balancing of carbon release by calcification via carbon uptake at the individual and ecosystem levels; (2) high rates of allochthonous organic carbon supply because of high particle trapping capacity; (3) high rates of carbon preservation and low remineralization rates; and (4) location in depositional environments. Some of these features are context‐dependent, meaning that these ecosystems were blue carbon sinks in some locations, but not others. Therefore, we provide a universal framework that can evaluate the likelihood of a given ecosystem to behave as a blue carbon sink for a given context. Overall, this paper seeks to encourage consideration of non‐classical blue carbon ecosystems within NBS strategies, allowing more complete blue carbon accounting. [ABSTRACT FROM AUTHOR]

This article discusses the importance of public engagement and citizen science in marine conservation efforts, specifically focusing on maerl, a type of coralline algae habitat found in Scotland. The article highlights various citizen science initiatives in the UK, such as Project Seagrass and Seasearch, which have contributed valuable data to inform conservation and management initiatives. It also discusses the establishment of protected areas, known as Special Areas of Conservation (SAC) and Marine Protected Areas (MPAs), to safeguard maerl habitats. The article emphasizes the role of community engagement and citizen science in increasing knowledge, monitoring habitats, reporting illegal activities, and promoting public awareness and engagement in maerl conservation. [Extracted from the article]

Aim of study: Marine climatic transition zones are boundary areas of major climate zones, here the boundary between the subtropical and temperate zones. They present areas containing high abundance of organisms living at the limit of their physiological tolerance. These marginal populations are particularly sensitive to changes in their environment. As such, marine climatic transition zones are excellent natural playgrounds for climate change-related hypothesis testing, especially with respect to marine habitat response to ocean warming. The marginal biogenic habitats around Jeju Island, South Korea, which lies within the temperate transition zone, have gradually changed from macroalgal-dominated to hard coral-dominated habitats. Understanding the specific abiotic environmental factors that influence the distribution of the marginal populations in temperate transition zones (i.e., species at their occurrence limit) is crucial to predicting and managing temperate zone habitat changes caused by climate change. This study aims to identify the specific abiotic environmental factors that contribute to explaining the current spatial distribution of the declining temperate and expanding subtropical foundation species in Jeju waters. Methods: Coverage and composition of sessile benthic communities were determined by photo-quadrat analysis at two depths (10 m and 15 m) at three sites along the island's south, east, and north coasts in May and November 2022. Divergences in community composition between sites were characterized in light of ten quantitative environmental parameters. Results: Our results show that sessile foundation communities vary significantly at different sites around the island. While the south is defined by high-latitude hard corals, predominately Alveopora japonica, the east is defined by the temperate canopy-forming macroalga Ecklonia cava, and the north is characterized by coralline algae. Winter sea surface temperature, water transparency, nutrient concentration, and water movement were statistically the most impactful environmental factors determining which foundation species constitute each distinct benthic community. Conclusion: This study provides valuable baseline information on the impacts of abiotic environmental factors on marine sessile communities in a temperate transition zone. [ABSTRACT FROM AUTHOR]

Ocean alkalinity enhancement (OAE), one of the marine carbon dioxide removal strategies, is gaining importance in its role towards alleviating the consequences of climate change as well as mitigating against ocean acidification (OA). OAE is based on adding alkalinity to open-ocean and coastal marine systems through a variety of different approaches, which raises carbonate chemistry parameters (such as pH, total alkalinity, aragonite saturation state), and enhances the uptake of carbon dioxide (CO2) from the atmosphere. There are large uncertainties in both short- and long-term outcomes related to potential environmental impacts, which would ultimately decide on the success of OAE as a climate strategy. This paper represents a meta-analyses effort, leveraging on the OA studies, data, observed patterns and generalizable responses. We propose a conceptual framework of categorized responses that are predicted under OAE implementation. The synthesis was done using raw experimental OA data based on 96 collected studies, capturing the responses of eleven biological groups (coralline algae, corals, dinoflagellates, mollusks, gastropods, pteropods, coccolithophores, annelids, crustacean, echinoderms, and foraminifera), using regression analyses to predict biological responses and thresholds to NaOH or Na2CO3 concentrations. Predicted responses were categorized into six different categories (linear positive and negative, threshold positive and negative, parabolic and neutral) to delineate species- and group-specific responders: 40 % of species are predicted to respond positively (N=38), 20 % of species negatively (N=20), and 40 % (N=38) were found to demonstrate a neutral response upon alkalinity addition. For negatively impacted species, biological thresholds corresponding to 10 to 500 µmol/kg NaOH addition were found, occurring at much lower values than previously expected. Such lower threshold values represent realistic conditions related to OAE field deployments but contrast with the conditions where current OAE lab experiments are conducted. We thus explicitly emphasize the importance of including much lower additions of alkalinity in experimental trials to realistically evaluate in situ biological responses. Due to practicality and high correlation with Ωar, we propose using the TA:DIC ratio as a helpful proxy to explore regional applications and biological response to OAE. The ultimate goal of the study is to provide a framework that can serve as a tool for predicting biological responses and thresholds to delineate OAE risks, guide and prioritize future OAE biological research and regional OAE monitoring efforts. With 60 % of species showing non-neutral response, a precautionary approach for OAE implementation is warranted, identifying the conditions where potential negative ecological outcomes could happen, which is key for scaling up while also avoiding potential risks. [ABSTRACT FROM AUTHOR]