Monthly variations in calix growth, polyp tissue, and density banding of the Mediterranean scleractinian Cladocora caespitosa (L.)

Monthly skeletal growth of the scleractinian, temperate coral Cladocora caespitosa (L.) from the Ligurian Sea (NW Mediterranean) was analysed for a period of 1 year and compared with seawater parameters. Measurements on corallite sections and on X-ray images showed that the formation of the high-density (HD) band and two dissepiments are favoured by fall–winter conditions, characterised by high quantities of rain, rough seas, and cold seawater. In summer, when the low-density (LD) band is formed, the corallites stretch upward and form one new dissepiment and one deep calix, where the polyps recede almost completely in August. These findings confirmed the adaptation of the temperate coral to winter environmental conditions, characterised by low irradiance and high availability of nutrients and food particles resuspended from bottom sediments. On the contrary, the high seawater temperature, irradiance, and ammonia contents stressed the coral in August and, when they persist in September, may cause the onset of mortality events.     

Fossil analogues of present-day Cladocora caespitosa coral banks: Sedimentary setting, dwelling community, and taphonomy (Late Pliocene, W Mediterranean)

 Cladocora caespitosa is a common zooxanthellate, ahermatypic, constructional scleractinian coral in shallow waters of the present-day Mediterranean. Extensive coral banks in Upper Pliocene shallow marine deposits of the Almería-Níjar Basin (SE Spain) contain the same species. These banks occur on debris-flow conglomerates deposited in a fan delta, or on bioclastic accumulations interpreted as storm deposits. Direct relationships of coral beds with coastal facies indicate that C. caespitosa colonized shallow settings near the paleocoast, probably not deeper than 20–30 m. Low turbulence allowed corals to colonize substrates, which remained stable for long periods. Activity of organisms in the coral community, storms, and detritic discharges from the fan delta were the most significant mechanisms disturbing the coral development. The hard substrata provided by coral banks promoted colonization by cemented and epibyssate organisms. Coral banks marked maximum flooding surfaces at the end of transgressive systems tracks. They were suddenly buried by sediment input into the basin. Taphonomic signatures measured on components of the coral bank communities indicate a low turbulence environment, probably a bay. The low hydraulic energy further inhibited post-burial reworking, thus promoting the in situ preservation of a great part of the organisms inhabiting the bioconstructions. Accepted: 2 December 1997     

Development of microsatellite markers as a molecular tool for conservation studies of the Mediterranean reef builder coral Cladocora caespitosa (Anthozoa, Scleractinia)

Cladocora caespitosa is a reef-building zooxanthellate scleractinian coral in the Mediterranean Sea. Mortality events have recurrently affected this species during the last decade. Thus, knowledge of its genetic structure, population diversity, and connectivity is needed to accomplish suitable conservation plans. In order to obtain a better understanding of the population genetics of this species, 13 highly variable microsatellites markers were developed from a naturally bleached colony. The developed primers failed to amplify zooxanthella DNA, isolated from C. caespitosa, verifying that these markers were of the coral and not algal symbiont origin. The degree of polymorphism of these loci was tested on tissue samples from 28 colonies. The allele number for each loci ranged from 2 to 13 (mean N(a) = 5.4), with an average observed heterozygosity of 0.42 (H(e) = 0.43) and all loci were in Hardy-Weinberg equilibrium. These new markers should be useful in future conservation genetic studies and will help to improve the resolution of the individual identification within this coral species. Primers were also tested in Oculina patagonica, with successful amplifications of several loci.     

The ecology of the Mediterranean stony coral Cladocora caespitosa (Linnaeus, 1767) in the Gulf of Trieste (northern Adriatic Sea): a 30-year long story

Cladocora caespitosa is an endemic coral of the Mediterranean Sea and an important carbonate bioconstructor that adds 3D complexity to the habitat, thus increasing marine biodiversity. Despite its important role in the ecosystem, the real status of the population along most of the Mediterranean coastline is still poorly investigated and very little is known about the resilience of the species. Using non-destructive visual surveys, colonies of C. caespitosa were investigated by SCUBA diving in 2013 and 2015 at seven sites of the northern Adriatic Sea (southern part of the Gulf of Trieste). Data about colony size, index of sphericity and corallite diameter were collected. Almost all biometrical parameters differed significantly among sampling sites, showing low occurrence of the larger size classes compared to the abundance of small-sized colonies. This pattern of distribution is typical of long-lived organisms. The positively skewed colony size distribution could be due to both a high mortality rate of small colonies unable to reach larger size classes, and to a high fragmentation rate of colonies, related to a strong hydrodynamic forces. The northern Adriatic population of C. caespitosa has previously been investigated by Schiller, who reported size and abundance data of colonies from one site, at a depth range of 2–5?m. We compared these data with our findings from the same sampling site, adding new information about the ecology of C. caespitosa. After a 30-year period, the comparison shows a change in the size distribution of colonies, with a decrease of the small class and an increase of the medium class of colonies. In view of these conclusions, further assessments are required in order to evaluate the trend of the northernmost C. caespitosa population in the Mediterranean Sea.     

The impact of seawater temperature on coral growth parameters of the colonial coral Cladocora caespitosa (Anthozoa, Scleractinia) in the eastern Adriatic Sea

The scleractinian coral Cladocora caespitosa deserves a special place among the major carbonate bioconstructors of the Mediterranean Sea. Annual coral skeleton growth, coral calcification, and skeleton density of the colonial coral C. caespitosa taken from 25 locations in the eastern Adriatic Sea were analyzed and compared with annual sea surface temperatures (SST). The growth rates of the coral C. caespitosa from the 25 stations in the Adriatic Sea ranged from 1.92 to 4.19?mm per year, with higher growth rates of the investigated corallites in the southern part of the Adriatic Sea. These growth rates are similar to those measured in other areas of the Mediterranean Sea. The correlation between coral growth and sea temperatures in the Adriatic Sea is seen as follows: An X-radiograph analysis of coral growth in C. caespitosa colonies that are over 60?years old showed that higher growth rates of this coral coincided with a warmer period in the Mediterranean Sea. A positive significant correlation exists between corallite growth rates and SST and coral calcification and SST. A negative correlation exists between coral density and SST. Coral growth rates also showed a correlation with higher eutrophication caused by nearby fish farms, along with a greater depth of the investigated colonies and high bottom currents.     

Reproduction of an early-flowering Mediterranean mountain narrow endemic (Armeria caespitosa) in a contracting mountain island

Reproduction at population lower edges is important for plant species persistence, especially in populations on contracting high-mountain islands. In this context, the ability of plants to reproduce in different microhabitats seems to be important to guarantee seed production in stressful environments, such as Mediterranean high mountains. We hypothesised that the warmer and drier conditions at the lower edge would be deleterious for the reproduction of Armeria caespitosa, an early-flowering plant. In addition, reproductive plasticity along this mountain gradient may also be microhabitat-dependent. We studied factors affecting the reproductive success of A. caespitosa , an endemic of the Spanish Sistema Central. We considered a complex set of predictors, including phenology, plant size and environmental factors at different scales using generalised estimating equations and generalised linear models. Microhabitat, together with the position in the altitudinal gradient and inter-annual variability affected the reproduction of A. caespitosa . In addition, individuals with longer flowering periods (duration of flowering) had significantly lower fruit set and a higher number of unviable seeds; delayed flowering peaks favoured the production of both viable and unviable fruits. Microhabitat variability over an altitudinal range is relevant for the reproduction of A. caespitosa, and is more important at the lower edge of the altitudinal range, where the species faces the most adverse conditions. In addition, the ability to reproduce in different microhabitats might increase the chances of the species to cope with environmental uncertainties under on-going climate warming. Finally, reproduction of this early-flowering plant is constrained by summer drought, which might shape its reproductive phenology.     

Intraspecific interactions in a scleractinian coral,Galaxea fascicularis: Induced formation of sweeper tentacles

Sweeper tentacles of Galaxea fascicularis have a different nematocyst composition than do ordinary tentacles. The sweeper tentacles contain many large microbasic b-mastigophores (MbM) instead of the microbasic p-mastigophores (MpM) which are abundant in the acrospheres of ordinary tentacles. There is, however, an intermediate type of tentacle which has both large MbM and MpM. These tentacles may represent those undergoing transformation from ordinary into sweeper tentacles or vice versa. Two polyps isolated from the same colony (syngeneic pairs), or from colonies belonging to different colour morphs (presumed allogeneic pairs), were set about 5 mm apart with tentacles touching, and then maintained for about two months in this position. Tissue fusion was observed only in syngeneic pairs. In some allogeneic combinations, one polyp of the pair was damaged or killed by the other. The dominant polyp developed many sweeper tentacles. In other allogeneic combinations, both polyps survived and no, or only a few, sweeper tentacles were formed. Tissue fusion also failed to occur in the allogeneic combinations.     

Habitat dynamics,marine reserve status,and the decline and recovery of coral reef fish communities

Severe climatic disturbance events often have major impacts on coral reef communities, generating cycles of decline and recovery, and in some extreme cases, community‐level phase shifts from coral‐ to algal‐dominated states. Benthic habitat changes directly affect reef fish communities, with low coral cover usually associated with low fish diversity and abundance. No‐take marine reserves (NTRs) are widely advocated for conserving biodiversity and enhancing the sustainability of exploited fish populations. Numerous studies have documented positive ecological and socio‐economic benefits of NTRs; however, the ability of NTRs to ameliorate the effects of acute disturbances on coral reefs has seldom been investigated. Here, we test these factors by tracking the dynamics of benthic and fish communities, including the important fishery species, coral trout (Plectropomus spp.), over 8 years in both NTRs and fished areas in the Keppel Island group, Great Barrier Reef, Australia. Two major disturbances impacted the reefs during the monitoring period, a coral bleaching event in 2006 and a freshwater flood plume in 2011. Both disturbances generated significant declines in coral cover and habitat complexity, with subsequent declines in fish abundance and diversity, and pronounced shifts in fish assemblage structure. Coral trout density also declined in response to the loss of live coral, however, the approximately 2:1 density ratio between NTRs and fished zones was maintained over time. The only post‐disturbance refuges for coral trout spawning stocks were within the NTRs that escaped the worst effects of the disturbances. Although NTRs had little discernible effect on the temporal dynamics of benthic or fish communities, it was evident that the post‐disturbance refuges for coral trout spawning stocks within some NTRs may be critically important to regional‐scale population persistence and recovery.     

Nutrient dynamics and ecosystem metabolism in the Bay of Blanes (NW Mediterranean)

The dynamics of the nutrient pools and their stoichiometry as well as their control by ecosystem metabolism (benthic and planktonic) and benthic–pelagic exchanges (sedimentation rates and sediment waterfluxes) were examined in the Mediterranean littoral (Blanes Bay, NE Spain). Dissolved organic nitrogen comprised about half of the nitrogen present in the water column and the carbon pool was dominated by the inorganic pool (95% of the carbon present in the water column). The dissolved and particulate organic pools were deficient in P relative to C and N, indicating a rapid recycling of P from organic matter. The pelagic compartment was heterotrophic, supported by significant allochthonous inputs of land material, which also contributed greatly to the sedimentary inputs (37% of total sedimenting carbon). In contrast, the benthic compartment was autotrophic, with the excess net benthic community production balancing the deficit in pelagic community production, leading to metabolic equilibrium at the station studied. Sedimentary inputs of nitrogen, phosphorus and silicon exceeded the benthic release, indicating that the benthic compartment acted as a sink for nutrients, consistent with its autotrophic nature. Carbon inputs to the benthic compartment also exceeded requirements, due to the allochthonous subsidies to the system, so that the benthic compartment stored or exported organic carbon. An erratum to this article can be found at .     

Spatio-temporal movement patterns of Diplodus vulgaris (Actinopterygii, Sparidae) in a temperate marine reserve (Lampedusa, Mediterranean Sea)

The movements of a commercially important species, Diplodus vulgaris, were assessed in a marine-protected area to test whether their spatial and temporal activity patterns differ during and outside of their spawning season. Twelve adults were caught along the north-eastern coast of a small Mediterranean island, tagged with acoustic transmitters and released within or just outside the integral reserve. Fish detected, during both the seasons showed strong fidelity for the study area before and during the spawning season and their home range did not differ between seasons. Home ranges reached an asymptote between 12 and 174 days after release. Home range estimated by kernel utilization distributions ranged from 9,876 to 89,914 m², with core areas of 946 to 7,274 m². Temporal patterns frequently showed a dominant diel rhythm with most of detections occurring at daytime, independently of season. The variability in the movement patterns of D. vulgaris was lower between seasons (i.e., during and outside the spawning season) than at smaller temporal scale (i.e., between day and night) and was largely affected by inter-individual differences. Some conclusions arising from this and previous findings are useful to orient future studies on coastal fish movement and have direct implications for MPAs design.     

Sedimentation stress in a scleractinian coral exposed to terrestrial and marine sediments with contrasting physical, organic and geochemical properties

Terrestrial runoff increases siltation and nutrient availability on coastal coral reefs worldwide. However the factors determining stress in corals when exposed to short-term sedimentation, including the interactions between sediments and nutrients, are little understood. We exposed corals to ten different sediment types at environmentally relevant concentrations (33 to 160 mg DW cm⁻²) and exposure times (12 to 60 h) in laboratory and field experiments. The sediments originated from 2 estuaries, 2 nearshore and one offshore locations and also included ground-up aragonite. For two of these sediments, three grain size fractions were used (silt < 63 μm, fine sand: 63-250 μm, medium sand: 250-500 μm). Sediments were characterised by 19 parameters grouped into “physical”, “organic and nutrient-related” and “geochemical” parameters. Changes in the photosynthetic yield of the coral Montipora peltiformis was measured by pulse-amplitude modulated chlorophyll fluorometry (PAM) as proxy for photophysiological stress from exposure, and to determine rates of recovery. Different sediments exerted greatly contrasting levels of stress in the corals. Our results show that grain size and organic and nutrient-related sediment properties are key factors determining sedimentation stress in corals after short-term exposure. Photophysiological stress was measurable after 36 h of exposure to most of the silt-sized sediments, and coral recovery was incomplete after 48 to 96 h recovery time. The four sandy sediment types caused no measurable stress at the same concentration for the same exposure time. Stress levels were strongly related to the values of organic and nutrient-related parameters in the sediment, weakly related to the physical parameters and unrelated to the geochemical parameters measured. M. peltiformis removed the sandy grain size classes more easily than the silt, and nutrient-poor sediments were removed more easily than nutrient-rich sediments. Anoxia developed on the sediment surfaces of the nutrient-rich silts, which had become slimy and smelled of hydrogen sulphide, suggesting increased bacterial activity. Our finding that silt-sized and nutrient-rich sediments can stress corals after short exposure, while sandy sediments or nutrient-poor silts affect corals to a lesser extent, will help refining predictions of sedimentation threats to coral reefs at given environmental conditions.     

Spatial and temporal patterns of scleractinian coral, soft coral, and zoanthid disease on a remote, near-pristine coral reef (Palmyra Atoll, central Pacific)

There is an urgent need for accurate baselines of coral disease prevalence across our oceans in order for sudden or unnatural changes to be recognized. Palmyra Atoll allows us to study disease dynamics under near-pristine, functionally intact conditions. We examined disease prevalence among all known species of scleractinian coral, soft coral and zoanthid (Palythoa) at a variety of coral reef habitats at Palmyra over a 2 yr period. In 2008, overall disease prevalence across the atoll was low (0.33%), but higher on the shallower backreef (0.88%) and reef terrace (0.80%) than on the deeper forereef (0.09%). Scleractinian coral disease prevalence was higher (0.30%) than were soft coral and zoanthid disease (0.03% combined). Growth anomalies (GAs) were the most commonly encountered lesions, with scleractinian species in the genera Astreopora (2.12%), Acropora (1.30%), and Montipora (0.98%) showing the highest prevalence atoll-wide. Discoloration necrosis (DN) was most prevalent in the zoanthid Palythoa tuberculosa (1.18%), although the soft coral Sinulana and Montipora also had a prevalence of 0.44 and 0.01%, respectively. Overall disease prevalence within permanently marked transects increased from 0.65% in 2008 to 0.79% in 2009. Palythoa DN contributed most to this increased prevalence, which coincided with rising temperatures during the 2009 El Ni?o. GAs on the majority of susceptible genera at Palmyra increased in number over time, and led to tissue death. Host distribution and environmental factors (e.g., temperature) appear to be important for determining spatiotemporal patterns of disease at Palmyra. More sophisticated analyses are required to tease apart the likely inter-correlated proximate drivers of disease occurrence on remote, near-pristine reefs.     

Complementary (secondary) metabolites in an octocoral competing with a scleractinian coral: effects of varying nutrient regimes

Competitive interactions between two sessile, epibenthic species were investigated on the Great Barrier Reef (GBR) in the presence and absence of added nutrients, as part of the Enrichment of Nutrients on Coral Reefs Experiment (ENCORE). Sarcophyton ehrenbergi Marenzeller (Octocorallia: Alcyonacea), an alcyonacean soft coral, and Pocillopora damicornis (Linnaeus), a scleractinian coral, were relocated and placed in contact with each other on large plastic grids on each of 12 micro-atolls within the One Tree Island (OTI) lagoon (23°30′S, 152°96′E, GBR). These micro-atolls were allocated in equal-sized groups to three enrichment treatments (addition of nitrogen, N; addition of phosphorus, P; addition of both nitrogen and phosphorus, N+P) and one control. Non-relocated (NR) and relocated colonies were also monitored as controls. After relocation and 1 year of nutrient enrichment, concentrations of a terpenoid complementary metabolite—sarcophytoxide—and wax esters were analyzed in colonies of S. ehrenbergi that had been exposed to elevated concentrations of N, P, N+P and compared with colonies on the non-nutrient-enriched control. Non-relocated control colonies from the natural environment were monitored over a period of 1 year and compared to colonies relocated to the control micro-atolls to assess handling effects. Analyses were performed on non-interacting S. ehrenbergi colonies, S. ehrenbergi colonies in experimental contact with P. damicornis colonies, and on non-interacting S. ehrenbergi colonies from the site of initial collection. Significant differences were found between sarcophytoxide levels in colonies of S. ehrenbergi in contact with P. damicornis vs. control/non-contact colonies; contact colonies had higher levels of this metabolite. Non-relocated control colonies of S. ehrenbergi exhibited significantly higher levels of sarcophytoxide than relocated control colonies. Augmentation of nutrient levels in micro-atolls significantly increased sarcophytoxide levels in S. ehrenbergi colonies relative to colonies on the control micro-atolls, although this response was not strong. Concentrations of fatty esters increased significantly through time in S. ehrenbergi colonies in their natural setting (non-relocated controls). This variability was not observed in relocated colonies in the treatment and control micro-atolls, irrespective of contact with P. damicornis. Concentrations of fatty esters in colonies of S. ehrenbergi in contact with P. damicornis were significantly lower than control/non-contact colonies, indicating that there is a cost in terms of stored energy reserves for the production of additional complementary metabolites when involved in competition for space. Augmentation of P levels in micro-atolls induced significant increases in fatty ester levels within S. ehrenbergi colonies vs. colonies in control micro-atolls, or in micro-atolls treated with added N or N+P together. These findings indicate that interspecific competition for space between a scleractinian coral and an alcyonacean soft coral and/or changes in the environmental nutrient regime can influence concentrations of complementary/secondary metabolites in the alcyonacean coral and the organism's stored energy reserves.     

Two new copepod genera (Poecilostomatoida) associated with the scleractinian coral Psammocora in New Caledonia

The anchimolgid copepod Paraclamocus hiulcus gen. n., sp. n., associated with the coral Psammocora togianensis near Nouméa, New Caledonia, is remarkable for the form of its mandible, with the inner margin broadly and deeply incised. The rhynchomolgid copepod Numboa porosa gen. n., sp. n., associated with Psammocora contigua , has a much flattened, discoidal prosome with many small surficial pores and lacks leg 4 and the endopod of leg 3. More than 200 species of copepods are associated with New Caledonian invertebrates, 80 of them with Scleractinia.     

Extraordinary aggressive behavior from the giant coral reef fish, Bolbometopon muricatum, in a remote marine reserve

Human impacts to terrestrial and marine communities are widespread and typically begin with the local extirpation of large-bodied animals. In the marine environment, few pristine areas relatively free of human impact remain to provide baselines of ecosystem function and goals for restoration efforts. Recent comparisons of remote and/or protected coral reefs versus impacted sites suggest remote systems are dominated by apex predators, yet in these systems the ecological role of non-predatory, large-bodied, highly vulnerable species such as the giant bumphead parrotfish (Bolbometopon muricatum) has received less attention. Overfishing of Bolbometopon has lead to precipitous declines in population density and avoidance of humans throughout its range, contributing to its status as a candidate species under the U. S. Endangered Species Act and limiting opportunities to study unexploited populations. Here we show that extraordinary ecological processes, such as violent headbutting contests by the world's largest parrotfish, can be revealed by studying unexploited ecosystems, such as the coral reefs of Wake Atoll where we studied an abundant population of Bolbometopon. Bolbometopon is among the largest of coral reef fishes and is a well known, charismatic species, yet to our knowledge, no scientific documentation of ritualized headbutting exists for marine fishes. Our observations of aggressive headbutting by Bolbometopon underscore that remote locations and marine reserves, by inhibiting negative responses to human observers and by allowing the persistence of historical conditions, can provide valuable opportunities to study ecosystems in their natural state, thereby facilitating the discovery, conservation, and interpretation of a range of sometimes remarkable behavioral and ecological processes.     

Growth and demography of the solitary scleractinian coral Leptopsammia pruvoti along a sea surface temperature gradient in the Mediterranean Sea

The demographic traits of the solitary azooxanthellate scleractinian Leptopsammia pruvoti were determined in six populations on a sea surface temperature (SST) gradient along the western Italian coasts. This is the first investigation of the growth and demography characteristics of an azooxanthellate scleractinian along a natural SST gradient. Growth rate was homogeneous across all populations, which spanned 7 degrees of latitude. Population age structures differed between populations, but none of the considered demographic parameters correlated with SST, indicating possible effects of local environmental conditions. Compared to another Mediterranean solitary scleractinian, Balanophyllia europaea, zooxanthellate and whose growth, demography and calcification have been studied in the same sites, L. pruvoti seems more tolerant to temperature increase. The higher tolerance of L. pruvoti, relative to B. europaea, may rely on the absence of symbionts, and thus the lack of an inhibition of host physiological processes by the heat-stressed zooxanthellae. However, the comparison between the two species must be taken cautiously, due to the likely temperature differences between the two sampling depths. Increasing research effort on determining the effects of temperature on the poorly studied azooxanthellate scleractinians may shed light on the possible species assemblage shifts that are likely to occur during the current century as a consequence of global climatic change.     

Population structure of Gobius bucchichii, in a Mediterranean marine reserve and in an unprotected area

Gobius bucchichii , in a protected area lived longer than those outside the reserve. Our findings emphasize the cryptic role played by marine protected areas on ecosystems.