Search

Lithophyllum okamurae has been widely reported in the Pacific Ocean with identification based on morpho-anatomical observations. Two infraspecific taxa, L. okamurae f. okamurae and f. angulare, described from Japan, have been recorded in the temperate region of Japan. We assessed branched Lithophyllum samples morphologically referable to L. okamurae using morpho-anatomical data and DNA sequences (psbA, rbcL and partial LSU rDNA) obtained from herbarium specimens, including type material, as well as recently field-collected material in Japan. The molecular analyses showed that these ‘L. okamurae’ samples contained two species: L. okamurae and a cryptic new species which we describe as L. neo-okamurae sp. nov. Because the holotype of L. okamurae f. angulare was conspecific with original material cited in the protologue of L. okamurae, it is a heterotypic synonym of L. okamurae f. okamurae. Lithophyllum okamurae and L. neo-okamurae were morphologically similar in having warty, lumpy and fruticose thalli and in often forming rhodoliths. Lithophyllum okamurae can be morpho-anatomically distinguished from L. neo-okamurae by the thallus with tapering or plate-like protuberances (knobby protuberances in the latter) and by having smaller tetrasporangial conceptacle chambers (167–314 µm; 248–380 µm in L. neo-okamurae). Our LSU rDNA sequence data from L. okamurae f. angulare (=L. okamurae f. okamurae) was identical to that of the type of L. margaritae, which has nomenclatural priority over L. okamurae. However, considering that psbA and rbcL sequences of L. margaritae type material could not be generated in the present study, we refrain, for the moment, from proposing the taxonomic synonymy between these two taxa until the status of L. margaritae and its synonyms from the type locality (Gulf of California) are clarified.

Algal habitat-forming forests composed of fucalean brown seaweeds (Cystoseira, Ericaria, and Gongolaria) have severely declined along the Mediterranean coasts, endangering the maintenance of essential ecosystem services. Numerous factors determine the loss of these assemblages and operate at different spatial scales, which must be identified to plan conservation and restoration actions. To explore the critical stressors (natural and anthropogenic) that may cause habitat degradation, we investigated (a) the patterns of variability of fucalean forests in percentage cover (abundance) at three spatial scales (location, forest, transect) by visual estimates and or photographic sampling to identify relevant spatial scales of variation, (b) the correlation between semi-quantitative anthropogenic stressors, individually or cumulatively (MA-LUSI index), including natural stressors (confinement, sea urchin grazing), and percentage cover of functional groups (perennial, semi-perennial) at forest spatial scale. The results showed that impacts from mariculture and urbanization seem to be the main stressors affecting habitat-forming species. In particular, while mariculture, urbanization, and cumulative anthropogenic stress negatively correlated with the percentage cover of perennial fucalean species, the same stressors were positively correlated with the percentage cover of the semi-perennial Cystoseira compressa and C. compressa subsp. pustulata. Our results indicate that human impacts can determine spatial patterns in these fragmented and heterogeneous marine habitats, thus stressing the need of carefully considering scale-dependent ecological processes to support conservation and restoration.

Coralline algae are one of the most diversified groups of red algae and represent a major component of marine benthic habitats from the poles to the tropics. This group was believed to be exclusively marine until 2016, when the first freshwater coralline algae Pneophyllum cetinaensis was discovered in the Cetina River, southern Croatia. While several studies investigated the element compositions of marine coralline algal thalli, no information is yet available for the freshwater species. Using XRD, LA-ICP-MS and nano indentation, this study presents the first living low-Mg calcite coralline algae with Mg concentrations ten times lower than is common for the average marine species. Despite the lower Mg concentrations, hardness and elastic modulus (1.71 ± 1.58 GPa and 29.7 ± 18.0 GPa, respectively) are in the same range as other marine coralline algae, possibly due to other biogenic impurities. When compared to marine species, Ba/Ca values were unusually low, even though Ba concentrations are generally higher in rivers than in seawater. These low values might be linked to different physical and chemical characteristics of the Cetina River.

Over the past decades, coralline algae have increasingly been used as archives of palaeoclimate information due to their seasonal growth bands and their vast distribution from high latitudes to the tropics. Traditionally, these reconstructions have been performed mainly on high latitude species, limiting the geographical area of their potential use. Here we assess the use of temperate crustose fossil coralline algae from shallow water habitats for palaeoenvironmental reconstruction to generate records of past climate change. We determine the potential of three different species of coralline algae, Lithothamnion minervae, Lithophyllum stictaeforme and Mesophyllum philippii, with different growth patterns, as archives for pH (δ11B) and temperature (Mg/Ca) reconstruction in the Mediterranean Sea. Mg concentration is driven by temperature but modulated by growth rate, which is controlled by species‐specific and intraspecific growth patterns. L. minervae is a good temperature recorder, showing a moderate warming trend in specimens from 11.37 cal ka BP (from 14.2 ± 0.4°C to 14.9 ± 0.15°C) to today. In contrast to Mg, all genera showed consistent values of boron isotopes (δ11B) suggesting a common control on boron incorporation. The recorded δ11B in modern and fossil coralline specimens is in agreement with literature data about early Holocene pH, opening new perspectives of coralline‐based, high‐resolution pH reconstructions in deep time.

The Amphistegina Bleaching Index (ABI) was applied to three Maldivian reefs in the Rasdhoo and North Ari Atolls in 2018, during normal sea surface temperature conditions. This dataset was then compared with a 2015, pre-coral bleaching study. The results provide a context for the verification and application of the ABI in outlining the photo-inhibitory stress status of coral reefs outside of the Florida Reef Tract where it was originally developed. The sampling periods encompass different seasons and temperature regimes. The 2015 field sampling preceeded the El Niño induced, mass coral-bleaching events of 2015 and 2016. It was carried out in late April and early May, during the dry season, when temperatures exceeded 31.5 °C and photosynthetically active radiation (PAR) was high. The 2018 sampling took place near the September equinox, towards the end of the monsoon, when PAR was again high, though water temperatures were ~30 °C. Although there were slightly higher percentages of bleached Amphistegina in 2018, there were also higher percentages of juveniles, indicating either that (1) the chronic stress was insufficient to impact asexual reproduction or (2) the onset of stress was within the past few weeks; the latter hypothesis was supported by an increase in PAR and temperature coinciding with the time of sampling. From the ABI plots it is possible to distinguish between the 2015 (high data scatter), highly stressed pre-bleaching conditions with elevated photo-oxidative stress levels, and the near-baseline conditions represented by the 2018 dataset (tight data clustering). Overall, this study thus shows the potential of Amphistegina populations and the ABI in forecasting bleaching events, and contributing to the question of the resilience potential of the coral reefs as a whole. It also highlights the usefulness and suitability of the ABI, within Maldivian coral reefs, as an indicator of photo-inhibition through photo-oxidative stress that can increase susceptibilit

Rhodolith beds are priority marine benthic habitats for the European Community, because of their relevance as biodiversity hotspots and their role in the carbonate budget. The high-Mg calcite calcified thalli promote their preservation through time, resulting in their common occurrence in the fossil record, thus making rhodoliths a significant archive of past environmental and climate changes. The present temperate Mediterranean Sea is home to rhodolith-rich up to rhodolith-dominated habitats which have been targeted over the years for ecological research and management actions. Furthermore, the Mediterranean Basin hosts an important fossil legacy of rhodolith beds that formed under contrasting climatic scenarios since the Neogene. Most examples of Mediterranean rhodolith beds lay within the depth range (30-75 m), while far less is known about deeper occurrences. An outstanding rhodolith bed has been recently identified off the Egadi Archipelago (70-95 m, Central Mediterranean Sea) in the frame of the Italian Marine Strategy Framework Directive project. The rhodolith bed carpets an area >7 km2 between Marettimo and Favignana Islands (Egadi Archipelago), with a cover of live rhodoliths up to 95%. The dominant rhodolith morphotype is pralines, ellipsoidal to discoidal in shape (average size 11 mm, maximum size 31 mm) associated with biogenic gravelly-sand. They present both seafloor bedforms (megaripples and ripples) and frequent bioturbations by epifaunal and semi-infaunal sea urchins. Old algal nodules, biogenic sand/mud, or, less frequently, terrigenous particles serve as nucleus of individual rhodoliths. Living calcareous algae are Lithothamnion valens, L. cf. minervae, Phymatolithon lenormandii, and Lithothamnion spp. The latter characterize also the dead algal association close to the nucleus, with the subordinate presence of Lithophyllum sp. Benthic fauna corresponds to the circalittoral environment, with exclusive species of the Coastal Detritic biocoenosis or

[Abstract] In this review we assess the state of knowledge for the coralline algae of the Mediterranean Sea, a group of calcareous seaweeds imperfectly known and considered highly vulnerable to long-term climate change. Corallines have occurred in the Mediterranean area for ~140 My and are well-represented in the subsequent fossil record; for some species currently common the fossil documentation dates back to the Oligocene, with a major role in the sedimentary record of some areas. Some Mediterranean corallines are key ecosystem engineers that produce or consolidate biogenic habitats (e.g., coralligenous concretions, Lithophyllum byssoides rims, rims of articulated corallines, maerl/rhodolith beds). Although bioconstructions built by corallines exist virtually in every sea, in the Mediterranean they reach a particularly high spatial and bathymetric extent (coralligenous concretions alone are estimated to exceed 2,700 km2 in surface). Overall, composition, dynamics and responses to human disturbances of coralline-dominated communities have been well-studied; except for a few species, however, the biology of Mediterranean corallines is poorly known. In terms of diversity, 60 species of corallines are currently reported from the Mediterranean. This number, however, is based on morphological assessments and recent studies incorporating molecular data suggest that the correct estimate is probably much higher. The responses of Mediterranean corallines to climate change have been the subject of several recent studies that documented their tolerance/sensitivity to elevated temperatures and pCO2. These investigations have focused on a few species and should be extended to a wider taxonomic set. Phylogeography, genomics, transcriptomics, and associated microbiomes are fields in which the information for Mediterranean corallines is very limited. We suggest that future work on Mediterranean corallines should be based on a multidisciplinary perspective combining different appro

Rhodoliths are important marine carbonate producers that provide habitat for several marine organisms, and are threatened by ongoing global climate change. Meter-sized sedimentary patches rich in living rhodoliths, interspersed among corals, were discovered in the back reef of Ras Ghamila lagoon, Southern Sinai, at less than 1 m water depth. In this shallow and relatively sheltered subtropical environment, rhodoliths were found to be monospecific or oligospecific, spheroidal, 3.5 to 9.4 cm in maximum diameter, with warty/lumpy or fruticose (protuberance degree IV) growth forms, and corresponded to the unattached branches or praline type. They grew in bright light under seasonal, moderate, wind-driven water motion. The dominant rhodolith-forming species recorded were: Lithophyllum kotschyanum, Porolithon onkodes, Hydrolithon sp. and three species of Neogoniolithon: Neogoniolithon fosliei, Neogoniolithon brassica-florida, and an undescribed species noted in the text as Neogoniolithon sp. A total of 38 Alizarin-stained rhodoliths was released in the field and collected after 1 year. They showed different banding patterns (alternating long and short cells) that revealed seasonal growth, with the lowest rates occurring in winter for all species, and an additional summer growth slackening in Neogoniolithon fosliei. Lithophyllum kotschyanum presented evidence of occasional growth cessation, possibly due to temporary burial. The observed annual growth rate of rhodoliths was unrelated to their size. The mean accretion rates were 1.08 mm · year−1 in L. kotschyanum, 0.75 mm · year−1 in P. onkodes, 0.49 mm · year−1 in Hydrolithon sp., 0.85 mm mm · year−1 in N. fosliei, 0.63 mm · year−1 in N. brassica-florida and 0.57 mm · year−1 in Neogoniolithon sp. The annual mean marginal elongation rate for these taxa was respectively 8.74, 13.92, 3.59, 9.40 and 9.25 mm · year−1, with the exception of Neogoniolithon sp., for which this parameter was not recorded. Maximum marginal elongation

Based on literature, the genus Lithophyllum was represented in the whole Indian Ocean by 14 taxa, mostly in need of revision in a modern context. Molecular analyses integrated with morpho-anatomical comparisons between the recently revised type material of Lithophyllum kotschyanum Unger, and the related infraspecific taxa, lead to a resumption of L. affine, L. kaiseri, and L. subreduncum, and the description of L. socotraense sp. nov., L. yemenense sp. nov., and L. subplicatum comb. et stat. nov. Detailed accounts are provided for each species, including keys, along with information on synonymy, examined collections, distribution, habitat as well as sequence data of the 5’ end of the LSU from the type specimens. The anatomical features of the tetrasporangial conceptacle that were considered collectively diagnostic for species identification are: the mean diameter of the tetrasporangial conceptacles, the length of the pore-canal in the tetrasporangial conceptacles (with the number of cells in roof filaments), the occurrence of a depression at the top of the conceptacle roof in relation to the pore opening, and the number of cells from the floor of the tetrasporangial conceptacle chamber to the thallus surface. This study provides evidence of a previously unsuspected diversity within the Red Sea and NW Indian Ocean species of Lithophyllum.

A new scleractinian coral species, Pachyseris inattesa sp. n., is described from the Red Sea. Despite a superficial resemblance with some species in the agariciid genus Leptoseris with which it has been previously confused, P. inattesa sp. n. has micro-morphological characters typical of the genus Pachyseris. This genus, once part of the Agariciidae, is comprised of five extant species and is widely distributed throughout the tropical Indo-Pacific. It is currently incertae sedis as a result of recent molecular analysis and appears to be closely related to the Euphylliidae. A molecular phylogenetic reconstruction including P. inattesa sp. n., the genus type species P. rugosa, and P. speciosa, all present in the Red Sea, was performed using the mitochondrial intergenic spacer between COI and 16S-rRNA. The results confirm that P. inattesa sp. n. is a monophyletic lineage closely related to the other Pachyseris species examined.

The current diagnosis of the genus Lithophyllum includes absent or rare trichocyte occurrence. After examining holotype material, single trichocytes have been revealed to occur abundantly in Lithophyllum kotschyanum Unger, and in freshly collected specimens of Lithophyllum spp. from the Red Sea, Gulf of Aden and Socotra Island (Yemen). Trichocyte occurrence is not considered a diagnostic character at specific or supraspecific levels in the Lithophylloideae, and the ecological significance of trichocyte formation is discussed. The generitype species,L. incrustans Philippi, does not show trichocytes nor do many other Lithophyllum species from diverse geographic localities,but the presence of abundant trichocytes in other congeneric taxa requires emendation of the genus diagnosis. Therefore, the diagnosis of Lithophyllum is here emended by eliminating the adjective “rare” in the sentence concerning trichocyte occurrence, as follows: “Trichocytes present or absent, if present occurring singly".

A previously unexplored subfamily of coralline algae, the Lithophylloideae, was investigated as potential paleoclimatic archive. For the first time, seasonal changes in Mg/Ca, Li/Ca and Ba/Ca composition of Lithophyllum spp. from the Gulf of Aden (Balhaf, Yemen), the Arabian Sea (Socotra, Yemen), and the South of Red Sea (Kamaran, Yemen) were investigated by Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). For the first time in coralline algae, the Li/Ca composition was analyzed and showed a highly significant and positive correlation with Mg/Ca and SST. Monthly algal Mg/Ca and Li/Ca variations indicate a positive correlation with sea water temperature (SST). Although no correlation between monthly algal Ba/Ca and local (SST) was found, fluctuations in Ba/Ca indicate the influence of nutrients introduced by seasonal upwelling, and record an increase of sediment at the sampling sites. From the age model of Mg/Ca the annual algal extension rates were measured in all specimens of Lithophyllum spp., and they resulted highly variable, mainly influenced by light and occasional burial. The elementary ratio of Mg/Ca, Li/Ca and Ba/Ca, and annual extension rate were successfully used in historical reconstruction of the climate and oceanographic variability of the study area.

The Amphistegina Bleaching Index (ABI) was applied to three Maldivian reefs in the Rasdhoo and North Ari Atolls in 2018, during normal sea surface temperature conditions. This dataset was then compared with a 2015, pre-coral bleaching study. The results provide a context for the verification and application of the ABI in outlining the photo-inhibitory stress status of coral reefs outside of the Florida Reef Tract where it was originally developed. The sampling periods encompass different seasons and temperature regimes. The 2015 field sampling preceeded the El Niño induced, mass coral-bleaching events of 2015 and 2016. It was carried out in late April and early May, during the dry season, when temperatures exceeded 31.5 °C and photosynthetically active radiation (PAR) was high. The 2018 sampling took place near the September equinox, towards the end of the monsoon, when PAR was again high, though water temperatures were ~30 °C. Although there were slightly higher percentages of bleached Amphistegina in 2018, there were also higher percentages of juveniles, indicating either that (1) the chronic stress was insufficient to impact asexual reproduction or (2) the onset of stress was within the past few weeks; the latter hypothesis was supported by an increase in PAR and temperature coinciding with the time of sampling. From the ABI plots it is possible to distinguish between the 2015 (high data scatter), highly stressed pre-bleaching conditions with elevated photo-oxidative stress levels, and the near-baseline conditions represented by the 2018 dataset (tight data clustering). Overall, this study thus shows the potential of Amphistegina populations and the ABI in forecasting bleaching events, and contributing to the question of the resilience potential of the coral reefs as a whole. It also highlights the usefulness and suitability of the ABI, within Maldivian coral reefs, as an indicator of photo-inhibition through photo-oxidative stress that can increase susceptibilit