Search Results (51)

The lower Messinian Calcare di Rosignano Formation (Tuscany, Italy, 43° N) preserves one of the youngest and northernmost examples of coral reefs in the Mediterranean. The outcropping succession of the Acquabona quarry consists of four main facies, namely, in ascending stratigraphic order: (1) coral boundstone, (2) coralline algal rudstone, (3) serpulid floatstone to packstone, and (4) peloidal packstone to grainstone. The succession displays a trend toward increasingly more shallow conditions and progressively more restricted water circulation. The coral reef displays a limited coral biodiversity and a remarkable abundance of heterotrophs, similar to modern coral reefs developed at the edges of the ecological niche of symbiont-bearing colonial corals. The widespread presence of coral colonies pervasively encrusted by coralline algae and benthic foraminifera suggests that short-term environmental perturbations caused temporary shutdowns of the coral-dominated carbonate factory. Moving upwards, there are fewer corals and more highly adaptable carbonate producers like coralline algae and serpulids. This suggests that the decline of corals had been caused by the conditions in the basin becoming more stressful, up to the collapse of the coral community. The overall succession indicates that coral-dominated ecosystems located at the edges of the coral zone are very sensitive; they can be affected even by minor perturbations and easily collapse if negative conditions persist. Full article

Dalian Island, located in the northwest of Pingtan County, Fujian Province, China, has been an important junction on the Maritime Silk Road since the Tang dynasty. This study focuses on sauce-glazed ceramic ware from the Song dynasty salvaged from the waters near Dalian Island Wharf. The composition, phase attributes, and microstructures of the marine organism remains attached to the ceramic ware were analyzed using an optical microscope, scanning electron microscope, and micro-Raman spectrometer to investigate the influence of marine organisms on the degradation of the ceramic ware. Long-term abrasion by sea wave-borne debris led to the increased surface roughness and wettability of the ceramic ware, facilitating the attachment of marine organisms. Differences in surface roughness between the inner and outer walls led to varying levels of biomass. Coralline algae secreted inducers to attract the larvae of macrofoulers. The attachment of different types of marine organisms had varying effects on the degradation of the ceramic ware. Firmly attached unitary organisms could alleviate the scouring of sea wave-borne debris and hinder the intrusion of foreign pollutants, thereby playing a ‘bio-protective’ role. In contrast, the group skeletons of modular organisms could reinforce the mechanically damaged surface but failed to block the intrusion of iron rust and other pollutants, resulting in chemical alterations of the glaze. Therefore, the specific species of the attached marine organisms should be considered in subsequent conservation efforts. Full article

The high diversity and biomass of organisms associated with coral communities depend directly on the maintenance or changes in the benthic composition. Over a decade, we evaluated the spatiotemporal variation in the benthic structure and composition of an insular coral community in the Northeastern Tropical Pacific. Our results show that local conditions drive spatiotemporal differences, and benthic organisms such as sponges, crustose coralline algae, octocorals, and hydrocorals all increased in abundance (cover) in response to negative thermal anomalies caused by the 2010–2011 La Niña event. In contrast, abnormally high temperatures, such as those recorded during the 2015–2016 El Niño Southern Oscillation (ENSO) event, explain the loss of scleractinian corals and crustose coralline algae coverage, which reduced the benthic groups’ richness (BGR), diversity (H’_BG), and evenness (J’_BG), with evidence of a consequent decrease in ecosystem function recorded the following year. Our analysis also showed that sites with high habitat heterogeneity harbored higher average BRG and H’_BG values and were less affected by environmental fluctuations than sites with high live scleractinian coral cover and lower BRG and H’_BG values. Therefore, the benthic structure was impacted differently by the same perturbation, and changes in the benthic community composition affected the groups associated with the community and ecological functions. More importantly, regional stressors such as the ENSO event caused only temporary changes in the benthic community structure, demonstrating the high resilience of the community to annual and interannual stressors. Full article

Cenozoic dolomitization of reefal carbonates has been widely found on many tropical islands worldwide. However, most ages and geochemical data obtained from bulk samples prevent a clear understanding of the previous complex diagenetic processes of these island dolostones due to a lack of in situ age and fluid composition. In this study, one deep borehole penetrated Cenozoic carbonates on Meiji Island in the southern South China Sea and massive dolostones with thicknesses over 400 m were uncovered. The in situ U–Pb geochronology and elemental analysis were conducted on the lower Nanwan Formation (upper Miocene) comprising undolomitized calcite (bioclast), replacive dolomite, and dolomite cement. Strontium isotope ages and U–Pb dates show that the penecontemporaneous replacive dolomitization occurred at 11.0–8.5 Ma, close to the deposition of precursor limestone. The dolomite cement precipitated at 8.5–6.0 Ma. In situ elemental analyses indicate that the formation of replacive dolomite and dolomite cement in the Nanwan Formation was probably controlled by seawater. The higher Mg/Ca ratio and lower Mn and Sr contents in dolomite cements show that their fluid underwent more evaporation. The dolomite content is positively related to the porosity of reefal limestones in the Nanwan Formation, suggesting that primary voids play an important role in fluid transportation during following dolomitization. Coralline algae and lime mud with algal fragments are beneficial for the rapid nucleation of dolomite. This study demonstrates that in situ elemental analysis using laser ablation has great potential for identifying the source of multistage dolomitizing fluids and can help refine the existing dolomitization model of isolated atolls. Full article

Coral reef rehabilitation in the Caribbean is of major ecological and economic importance in the West Indies. Local organizations in Grenada constructed a cement pyramid artificial reef structure with rugosity (termed “The Pyramid”) and placed a number of these artificial reefs in a shallow marine area fringing two major natural reefs in the southwest coastal region of Grenada. Benthic data for two nearby natural reefs were compared to the benthic evaluation of the artificial reef pyramids. This comparison demonstrated that the artificial reef pyramids were similar in many respects to the natural reefs but were significantly different in macro- and coralline algae cover, two key indicators of reef health. This report is the first benthic evaluation of an artificial reef through comparison to natural reefs in Grenada. Full article

Assessing the effectiveness of artificial structures as a monitoring tool for benthic diversity in temperate reefs is crucial to determining their relevance in reef conservation and management. In this study, we utilized Autonomous Reef Monitoring Structures (ARMS) to evaluate sessile benthic communities that colonized ARMS units after 12 and 34 months of immersion within distinct habitats (coral-dominated and macroalgae-dominated habitats) in Jeju Island, Korea. We used two methods: image analysis of the ARMS plates and DNA metabarcoding of the ARMS units. We found significant differences in the sessile benthic community between the plate faces, installation periods, and habitats. DNA metabarcoding also revealed differences in sessile benthic diversity among habitats. Additionally, we identified the Lithophyllum genus within the crustose coralline algae community, whose dominance might trigger a transition to coral-dominated habitats in Jeju Island. We recommend integrating ARMS image analysis with DNA metabarcoding to enhance and complement studies focusing on benthic diversity. By utilizing ARMS, this study provides valuable information for understanding sessile benthic communities and biodiversity, contributing to an enhanced understanding of the responses of ecological communities to climate change. Full article

Outbreaks of crown-of-thorn starfish (COTS) have caused dramatic declines in reefs through predation on corals, but the post-bloom effects of COTS may still potentially threaten the environment and living organisms due to massive organic decomposition. This stimulation experiment showed that the decomposition of COTS debris triggered an extra mineralization process and resulted in acidifying, hypoxic, and eutrophic seawater. Consequently, the photosynthetic efficiency of coral symbionts decreased by 83%, and coral bleached after removing the stress within two days, then the coral skeleton dissolved at rates of 0.02–0.05 mg cm⁻² day⁻¹. Within two weeks, the photosynthesis and growth of benthic algae were suppressed by 27–86% and 1.5–16%, respectively. The mortality of turf algae and coralline algae indicated compromised primary productivity and limited coral recruitment, respectively. However, macroalgae, as coral competitors, became the only survivors, with increasing chlorophyll content. This study suggests a continuing decline of reefs during the collapse phase of COTS outbreaks and highlights the need for improving control strategies for the COTS population. Full article

A unique shift in benthic community composition, where scleractinian corals are replaced by coralline algae, has been observed on coral reefs in Guam in the western Pacific. Guam’s reefs have been subjected to intense fishing pressure and impaired water quality for decades. Since 2013, heat stress has emerged as an additional major threat to the island’s coral reefs. After a severe coral bleaching and mortality event in 2017, branching coralline algae of the genus Lithophyllum rapidly overgrew dead coral skeletons of the ecosystem engineer Acropora abrotanoides and have since become major components of forereef communities over a broad depth range. By now, the persistence of increased Lithophyllum cover meets the temporal criterium of phase shifts, but accurate estimates on the degree of dominance over appropriate spatial scales are lacking due to the absence of reliable baseline data. The ecological impacts of coral reef transitions towards increased coralline cover are unclear. Whereas carbonate budgets and reef growth could remain positive in the long term, the downstream effect of changes in structural complexity, (micro)habitat diversity, and benthic community composition on ecological processes and reef-associated faunal assemblages is unknown. Full article

The aim of this study was to elucidate the taxonomy of the common but overlooked epiphytic coralline algae species from shallow reefs and seagrass meadows of the Abrolhos Archipelago, Brazil. Two thin (two vegetative cells thick) epiphytic coralline species were recorded: Lithophyllum epiphyticum sp. nov. and Hydrolithon farinosum. Molecular analysis from psbA genetic marker confirmed the position of L. epiphyticum into Lithophylloideae and revealed a phylogenetic relationship with an undescribed Lithophyllum from Italy. Thin thallus (2–3 cells thick) and cells lining the pore of tetrasporangial conceptacles protruding laterally occluding the canal, either partially or totally, are its main diagnostic characteristics. Hydrolithon farinosum is herein described in detail for Brazil, and its worldwide distribution is then discussed. Full article

Coralline algal beds are comprised of biogenic calcareous formations considered a habitat of high conservation interest, hosting a high great biodiversity. To assess the status of this habitat in the Italian seas, we report results from a systematic analysis of the available scientific literature. Italian rhodolith/maerl beds are reported on 31 Italian sites mostly located around islands, shoals, banks, terraces, and gentley sloping shelves, from 9 m to 130 m water depth (with a mean depth of about 56 m). The dominant species occurring in the Italian submarine sites are Phymatolithon calcareum and Lithothamnion corallioides, with a rich associated fauna including sponges, bryozoans, hydrozoans, polichaetes, molluscs, amphipods, gastropods, echinoderms. Despite the high biodiversity characterizing the Italian rhodolith/maerl beds, only seven submarine sites hosting this sensitive habitat are part of Marine Protected Areas (MPAs). This evidence highlights the need for actions focused on the implementation of effective management and proper conservation measures to preserve such precious habitats. Protection of this habitat cannot be effectively provided without access to multidisciplinary data (e.g., geospatial, biological, geophysical, geomorphological data) capable of assessing its spatial distribution and biological characteristics over wide areas. An increased research effort to improve the production of fine-scale distribution maps and monitoring activities is therefore needed. Full article

In this paper, the physiography, geomorphological features, and sedimentary bedforms of the offshore Egadi Islands (Italy) have been illustrated and mapped through an integrated analysis of high-resolution bathymetric, seismo-acoustic, and sedimentological data. The study area is characterized by a wide, up to 25 km, continental shelf which is separated by a NNW-trending linear incision, the Marettimo Channel, along which several erosional and depositional features have been detected and mapped. Sedimentary prograding wedges were detected at water depths between 100–125 m along the shelf margin, which accumulated during the sea-level fall and lowstand stages of the last glacio-eustatic cycle (post- MIS 5.5). This study detected several slope breaks defining scarps across the continental shelf, which were interpreted as coastal cliffs that originated during the post-LGM eustatic sea-level rise. Several fields of different types of sedimentary bedforms, including 2-D and 3-D hydraulic dunes and sorted bedforms, were found across the continental shelf, providing evidence of a high hydrodynamic regime affecting the seafloor. Further on, this study recognized erosive and depositional features related to bottom currents (contourites) in the Marettimo Channel. These findings provide a better understanding of the morpho-sedimentary evolution of the Egadi Islands offshore in the latest Quaternary. Moreover, they offer essential scientific support for effectively managing the most valuable priority habitats for conservation, such as the Posidonia oceanica meadow and coralline algae bioconstructions (Coralligenous habitat). Full article

Rhodoliths are non-geniculate, free-living coralline red algae that can accumulate on the seafloor and form structurally complex benthic habitats supporting diverse communities known as rhodolith beds. We combined in situ rhodolith collections and imagery to quantify variability, over 9 months and at two sites, in the structural complexity and biodiversity of a subarctic Lithothamnion glaciale rhodolith bed. We show that the unconsolidated rhodolith framework is spatially heterogeneous, yet provides a temporally stable habitat to an abundant and highly diverse macrofauna encompassing 108 taxa dominated by brittle stars, chitons, bivalves, gastropods, polychaetes, sea urchins, and sea stars. Specific habitat components, including large bivalve shells, affect rhodolith morphology and resident macrofauna, with increasingly large, non-nucleated rhodoliths hosting higher macrofaunal density, biomass, and diversity than increasingly large, shell-nucleated rhodoliths. The present study’s fine taxonomic resolution results strongly support the notion that rhodolith beds are biodiversity hotspots. Their spatial and temporal domains provide clear quantitative evidence that rhodolith beds provide a stable framework under the main influence of biological forcing until sporadic and unusually intense physical forcing reworks it. Our findings suggest that shallow (<20 m depth) rhodolith beds are vulnerable to ongoing and predicted increases in the frequency and severity of wave storms. Full article

Porphyra corallicola was described based on a filamentous red alga inadvertently introduced into culture from a crustose coralline alga. This species is known only in its sporophyte (Conchocelis) stage, being possibly asexual and lacking the charismatic and “collectable” gametophyte stage. Consequently, little is known of its range and distribution. Taxon-targeted metabarcoding was explored as a pathway to gain insights into the vertical (intertidal versus subtidal) and biogeographical distribution of this species, as well as to assess host diversity. We also wanted to ascertain if other species occur in only the Conchocelis stage in the Canadian flora. Primers targeting a short (521 bp) region of the plastid rbcL gene in the Bangiales were used to screen DNA from 285 coralline crusts collected throughout Canada and adjacent waters. In addition to confirming the presence of P. corallicola in the Bay of Fundy, this species was recovered from coralline crusts along the coast of Nova Scotia (n = 1) and in the low Arctic (Labrador; n = 2), greatly extending its range and suggesting it is a cold-water taxon. We have confirmed its presence in both the low intertidal and subtidal (to 10 m), and its occurrence in three different coralline species, suggesting that it lacks host specificity. In total, nine genetic groups of Bangiales were uncovered in our survey, six matching entries currently in GenBank and three apparently novel genetic groups—two from the northeast Pacific and one from the low Arctic. Notable host and ecological patterns are discussed. This method, when further developed, will facilitate the study of Conchocelis stages in nature, which will greatly enhance ecological knowledge of bangialean species. Full article

Two marine halacarids, Copidognathus levicostatus n. sp. and C. vicinus Bartsch, 1997, belonging to the C. gibbus group, have been recorded based on both sexes from the microhabitat of intertidal and sublittoral rocks on the coast of South Korea. Copidognathus levicostatus n. sp. Is characterized by a combination of features, as follows: the absence of areolae with rosette pores on all dorsal and ventral plates, the presence of a short frontal process, a pair of costae with raised narrow ribs on the posterior dorsal plate, the partial fusion of the anterior epimeral plate and genitoanal plate in both sexes, and three pairs of perigenital setae in the male. The Korean specimens of C. vicinus Bartsch, 1997 agree well with the original description from Hong Kong, except for the lateral claws bearing a comb. This study provides detailed (re)descriptions of the morphological characteristics of the two Korean halacarid species, C. levicostatus n. sp. and C. vicinus, based on illustrations and scanning electron microscope photomicrographs. Additionally, we present a dichotomous key for known Copidognathus species in Korean waters, accompanied by a brief comment on their occurrence in various microhabitats, especially their habitat preferences for geniculate and non-geniculate red coralline algae. Full article

Crustose coralline algae (CCA) occur from the tropics to the poles in photic benthic environments. Here, we report on some of the world’s southernmost and coldest CCA sites in Terra Nova, Ross Sea, Antarctica at 74°41′ S. The recently described red alga Tethysphytum antarticum is investigated for its skeletal architecture, its mineralogical and geochemical composition, as well as for its taxonomic classification. A phylogenetic analysis based on molecular genetics and the sequencing of the photosystem II protein D1 (psbA) gave a perfect match with T. antarcticum. Histological sections and micro-CT-scans provide new diagnostic details for the conceptacles (the reproductive organs of the alga). X-ray diffractometry and electron-microprobe measurements yielded a clear high-Mg calcite (~8 mol%) composition of the skeletal parts. Detailed back-scattered electron imaging of polished petrographic thin sections revealed a two-layered thallus (vegetative plant tissue), comprising an organic-rich irregularly calcified basal layer with rectangular cells, overlain by the main thallus. Elemental maps show relatively increased sulphur in the basal layer, clearly tied to organic cell walls. MgCO₃ and SrCO₃ were targeted with semiquantitative elemental mappings and in an ontogenetic quantitative spot transect. Compared with temperature (−1.95 °C to +1.08 °C), the MgCO₃ (mol%) reflects this world’s coldest CCA site temperature with the lowest MgCO₃ content of 7.9 ± 1.6 mol%. The along transect variability, however, shows with ~6 mol% a larger MgCO₃ variability than expected for the 3 °C intra-annual temperature amplitude in Terra Nova Bay. This implies that in low amplitude settings the biomineralisation control on Mg/Ca ratios can outcompete its temperature sensitivity. Mark-recapture studies, next to the environmental logger station La Zecca are suggested, to perform a detailed growth rate and biomineralisation quantification. Full article