Branching Coral Stylophora Pistillata Research Articles

Coral bleaching due to cold stress on a central Red Sea reef flat.

Ocean warming is leading to more frequent coral bleaching events. However, cold stress can also induce bleaching in corals. Here, we report observations of a boreal winter bleaching event in January 2020 in the central Red Sea, mainly within a population of the branching coral Stylophora pistillata on an offshore reef flat. Sea surface temperatures (SSTs) rarely fall below 24°C in this region, but data loggers deployed on several nearby reef flats recorded overnight seawater temperatures as low as 18°C just 3 days before the observations. The low temperatures coincided with an extremely low tide and cool air temperatures, likely resulting in the aerial exposure of the corals during the night time low‐tide event. The risk of aerial exposure is rare in winter months, as the Red Sea exhibits seasonal fluctuations in sea level with winter values typically 0.3–0.4 m higher than in summer. These observations are notable for a region typically characterized as a high‐temperature sea, and highlight the need for long‐term monitoring programs as this rare event may have gone unnoticed.

Elevated temperatures reduce the resilience of the Red Sea branching coral stylophora pistillata to copper pollution.

Copper (Cu) is a common marine pollutant of coastal environments and can cause severe impacts on coral organisms. To date, only a few studies assessed the effects of Cu contamination in combination with elevated seawater temperatures on corals. Furthermore, experiments focusing on coral recovery during a depuration phase, and under thermal stress, are lacking. The present study investigated the physiological response of the common and thermally tolerant scleractinian coral Stylophora pistillata from the northern Red Sea to Cu contamination (2.5, 5 or 10µg L-1) in combination with thermal stress (5°C above local ambient temperatures (26°C)) for 23 days, and assessed the impact of elevated temperatures on its ability to recover from such pollution during a one-week depuration period. Variation in coral photo-physiological biomarkers including antioxidant defense capacity, were dose, time and temperature-dependent, and revealed additive effects of elevated temperatures. Successful recovery was achieved in ambient temperature only and was mediated by antioxidant defenses. Elevation of temperature altered the recovery dynamics during depuration, causing reduced Cu bioaccumulation and photosynthetic yield. The present study provides novel information on the effects of elevated temperature on the resilience (resistance and recovery processes) of a scleractinian coral exposed to a common marine pollutant. Our findings suggest that ocean warming may alter the resilience strategies of corals when exposed to local pollution, an impact that might have long-term consequences on the chances of survival of reefs in increasingly populated and warming coastal environments.

Spatial distribution of conspecific genotypes within chimeras of the branching coral Stylophora pistillata

Chimerism is a coalescence of conspecific genotypes. Although common in nature, fundamental knowledge, such as the spatial distribution of the genotypes within chimeras, is lacking. Hence, we investigated the spatial distribution of conspecific genotypes within the brooding coral Stylophora pistillata, a common species throughout the Indo-Pacific and Red Sea. From eight gravid colonies, we collected planula larvae that settled in aggregates, forming 2–3 partner chimeras. Coral chimeras grew in situ for up to 25 months. Nine chimeras (8 kin, 1 non-related genotypes) were sectioned into 7–17 fragments (6–26 polyps/fragment), and genotyped using eight microsatellite loci. The discrimination power of each microsatellite-locus was evaluated with 330 ‘artificial chimeras,’ made by mixing DNA from three different S. pistillata genotypes in pairwise combinations. In 68% of ‘artificial chimeras,’ the second genotype was detected if it constituted 5–30% of the chimera. Analyses of S. pistillata chimeras revealed that: (a) chimerism is a long-term state; (b) conspecifics were intermixed (not separate from one another); (c) disproportionate distribution of the conspecifics occurred; (d) cryptic chimerism (chimerism not detected via a given microsatellite) existed, alluding to the underestimation of chimerism in nature. Mixed chimerism may affect ecological/physiological outcomes for a chimera, especially in clonal organisms, and challenges the concept of individuality, affecting our understanding of the unit of selection.

Morphometric and allometric rules of polyp's landscape in regular and chimeric coral colonies of the branching species Stylophora pistillata.

Most studies on architectural rules in corals have focused on the branch and the colony level, unveiling a variety of allometric rules. Working on the branching coral Stylophora pistillata, here we further extend the astogenic directives of this species at the polyp level, to reveal allometric and morphometric rules dictating polyps' arrangement. We identified a basic morphometric landscape as a six-polyp circlet developed around a founder polyp, with established distances between polyps (six equilateral triangles), reflecting a strong genetic-based background vs high plasticity on the population level. Testing these rules in regular and chimeric S. pistillata colonies, we revealed similar morphometric/allometric rules developed via a single astogenic pathway. In regular colonies, this pathway was driven by the presence/absence of intra-circlet budding polyps, while in chimeras, by the distances between the two founder polyps. In addition, we identified the intra-circlet budding as the origin of first branching, if BPC distances are kept <1.09 ± 0.25 mm. The emerged allometric/morphometric rules indicate the existence of a positional information paradigm for polyps' landscape distribution, where each polyp creates its own positional field of morphogen gradients through six inductive sites, thus forming six positional fields for the development of the archetypal "six-polyp crown".

Recovery assessment of the branching coral Stylophora pistillata following copper contamination and depuration

Most contemporary coral reefs live under both global (e.g. warming and acidification) and local (e.g. overfishing, pollution) stressors, which may synergistically undermine their resilience to thermal bleaching and diseases. While heavy metal toxicity in reefs has been well characterized, information on corals recovery from acute contamination is lacking. We studied for 42 days the ability of the coral Stylophora pistillata from the Gulf of Aqaba (northern Red Sea) to recover from a short (3 days) and prolonged (14 days) copper (Cu) contamination (1 μg L−1), after 11 (‘Exp3/D11’) and 28 (‘Exp14/D28’) days of depuration, respectively. Cu caused a decrease in chlorophyll content after 3 days, and in net photosynthesis (Pn) after 14 and 42 days. ‘Exp14/D28’ showed successful recovery based on Pn and relative electron transport rate, as opposed to ‘Exp3/D11’. Results suggest the depuration time may be of greater importance than the exposure period to recover from such contamination.

Rapid Recruitment of Symbiotic Algae into Developing Scleractinian Coral Tissues

While the early acquisition of Symbiodiniaceae algae into coral host tissues has been extensively studied, the dynamics of the migration of algal cells into rapidly expanding coral tissues still lacks a systematic study. This work examined two Red Sea branching coral species, Pocillopora damicornis and Stylophora pistillata, as they were growing and expanding their tissue laterally on glass slides (January–June, 2014; 450 assays; five colonies/species). We measured lateral tissue expansion rates and intratissue dinoflagellate migration rates. Tissue growth rates significantly differed between the two species (with Stylophora faster than Pocillopora), but not between genotypes within a species. Using a “flow-through coral chamber” under the microscope, the migration of dinoflagellates towards the peripheral edges of the expanding coral tissue was quantified. On a five-day timescale, the density of the endosymbiotic dinoflagellate cells, presenting within a 90 µm region of expanding coral tissue (outer edge), increased by a factor of 23.6 for Pocillopora (from 1.2 × 104 cells cm‒² to 2.4 × 105 cells cm‒²) and by a factor of 6.8 for Stylophora (from 3.6 × 104 cells cm‒² to 2.4 × 105 cells cm‒²). The infection rates were fast (5.2 × 104 and 4.1 × 104 algal cells day-1 cm‒², respectively), further providing evidence of an as yet unknown pathway of algal movement within coral host tissues.

Copper enrichment reduces thermal tolerance of the highly resistant Red Sea coral Stylophora pistillata

Corals in the Gulf of Aqaba (GoA) in the northern Red Sea show high thermal tolerance. The GoA has therefore been suggested as a coral reef refuge from climate change. However, as a narrow body of water with high residence time and a rapidly growing population, the GoA is prone to anthropogenic stressors, heavy metal pollution being one such stressor. In the present study, the branching coral Stylophora pistillata, extensively studied for its high resistance to elevated seawater temperature in the GoA, was exposed to combinations of thermal treatments (ambient (21–23 °C), + 4 °C and + 8 °C above ambient) and ecologically relevant copper (Cu) concentrations (ambient and + 1 µg L−1 above ambient concentration). Significant interactions were found between elevated temperature and Cu enrichment effects on coral physiology, mainly affecting processes associated with photosynthesis. Contrasting responses were recorded at 72 h and 2 weeks from start of the exposure to Cu enrichment. Cu enrichment caused a decrease in Fv/Fm, maximum rETR, and net photosynthesis in ambient temperature after Cu exposure of 72 h, while at the second sampling point only (2 weeks), a decrease was also recorded at + 4 and + 8 °C. Superoxide dismutase activity was higher in Cu-enriched conditions, suggesting that corals were responding to oxidative stress. Thus, a higher input of Cu in the GoA may be energetically costly and might result in decreased resistance of corals to thermal stress under warming scenarios.

Light enhanced calcification in Stylophora pistillata: effects of glucose, glycerol and oxygen.

Zooxanthellate corals have long been known to calcify faster in the light than in the dark, however the mechanism underlying this process has been uncertain. Here we tested the effects of oxygen under controlled pCO2 conditions and fixed carbon sources on calcification in zooxanthellate and bleached microcolonies of the branching coral Stylophora pistillata. In zooxanthellate microcolonies, oxygen increased dark calcification rates to levels comparable to those measured in the light. However in bleached microcolonies oxygen alone did not enhance calcification, but when combined with a fixed carbon source (glucose or glycerol), calcification increased. Respiration rates increased in response to oxygen with greater increases when oxygen is combined with fixed carbon. ATP content was largely unaffected by treatments, with the exception of glycerol which decreased ATP levels.

Flow inside a coral colony measured using magnetic resonance velocimetry

The velocity field within scale models of branching coral Stylophora pistillata colonies was measured using magnetic resonance velocimetry (MRV). The models were based on digital representations of real coral skeletons derived using X‐ray computed tomography (CT) and constructed using rapid‐prototype manufacturing. Two morphologies of S. pistillata from the Red Sea grown in different flow regimes were used. To simplify visualization of the data, velocities were parsed into a series of spherical shells, giving the velocity distributions as functions of distance from coral center for both morphologies. The low‐flow morphology distributed flow velocity relatively evenly throughout the interior. In contrast, the high‐flow morphology showed a wider range of velocities with regions of flow channeling and flow stagnation.

Geographic divergence in the relationship between Paragobiodon echinocephalus and its obligate coral host

The redhead goby Paragobiodon echinocephalus lives exclusively within the branching coral Stylophora pistillata. While in the Great Barrier Reef fish occupation rate of large coral is higher than that of small coral, an opposite pattern exists in the northern Red Sea. It is suggested that this pattern is caused by a limitation on the adult body size of fish in the northern Red Sea.

Alleviating impacts of anthropogenic activities by traditional conservation measures: can a small reef reserve be sustainedly managed?

Zoning schemes that are becoming an important management tool in large marine reserves, are difficult to implement in small reef areas. At the 3.4 km long reef of Eilat (Red Sea), a small (ca. 350 m of coastline) enclosure strategy has been enforced since 1992, while the remaining reef was left open to intense human activities. Here we have investigated for 2.5 y three populations of the branching coral Stylophora pistillata (3605 colonies) in a locality within the enclosed area (site NR) and in two areas open to the public, by tossing random quadrats at the shallow lagoonar zone (0.5–1.5 m depth). In the two open sites we found significantly higher levels of colony breakage (14–34% vs. 4–9% in the enclosed site), lower partial mortality levels of colonies (in the first 1.5 y; 7–9% vs. 23–30% at NR), higher recruitment (up to 3.0 vs. up to 0.9 colonies/m 2), 50% reduction in coral life span (10 vs. 20 y) and an estimated extinction period of 9–10 y for new cohorts as compared to >20 y in the enclosed site. Average colony size and maximal colony size were about half in the open sites. Live coverage fluctuated widely in all sites but was 3 times higher in the enclosed area (1.0–3.0% vs. 0.3–1.1%). Log-transformed size frequency distributions revealed, at the open sites, a shift from small towards medium-size classes and at the enclosed site, a shift from larger to medium size classes. We conclude that the enclosure of a limited core zone, although improved some ecological parameters, was not sufficient to compensate for stress imposed by anthropogenic activities. It is suggested to employ active restoration approaches, such as the “gardening concept”, as supplementary management tools.

Effects of particulate matter released by a fish farm (Eilat, Red Sea) on survival and growth of Stylophora pistillata coral nubbins

This field study aims to determine whether increased levels of organically enriched particulate matter released by net pen fish farms (Eilat, Red Sea) would affect the growth of nubbins taken from the branching coral Stylophora pistillata. We followed the survival and growth of 1322 nubbins pruned from five colonies that were transplanted at a depth of 6 m in the vicinity of the fish cages and in a reference site, in front of the Interuniversity Institute (IUI). Nubbins were attached on U-shaped PVC plates in three orientations (up, vertical and down positions). After 50 days, survival was high in both localities and no difference was recorded between the spatial orientations. At the fish farm, however, burial of the nubbin’s lateral growths and partial coverage of nubbins by settled particulate matter resulted in significant reduction of the lateral growth rates of nubbins settled in the up position as compared to the reference site. On the other hand, faster growth rates were recorded in the vertical set of nubbins at the fish farm when compared with the IUI site. These results strengthen the conclusion that physical effects, rather than nutrient enrichment, may constitute the main cause of stress for minute coral fragments (resembling coral recruits) growing near the vicinity of a fish farm.

Molecular Characterization of the First Heat Shock Protein 70 from a Reef Coral

The branching coral Stylophora pistillata, one of the most abundant hermatypic corals along the coasts of the Red Sea, has been used for many years as a model species for coral biological studies. Here we characterize the first coral heat shock protein 70 gene (SP-HSP70), cloned from S. pistillata, to be used as a tool for studying coral stress response. The cloning was carried out by a combination of PCR methods using heterologous, degenerate HSP70-based primers, followed by plaque-lift screening of a genomic library. The sequenced clone (5212 bp), contains a complete 1953 bp, intronless open reading frame, and 5′ and 3′ flanking regions of 1,935 and 1,324 bp, respectively. TATA, CAAT, and ATF boxes as well as 11 putative heat shock elements were identified in the SP-HSP70 5′ flanking region. A polyadenylation site was identified in the 3′ flanking region. SP-HSP70 protein sequence resembles the cytosolic/nuclear HSP70 cluster. RT-PCR studies confirmed SP-HSP70 mRNA expression in corals grown within their normal physiological conditions. Furthermore, SP-HSP70 has been shown to belong to the coral genome and not to its symbiotic algae one, as revealed by SP-HSP70 PCR amplification, using purified algal and coral DNA templates.

Effects on growth and reproduction of the coral Stylophora pistillata by the mutualistic damselfish Dascyllus marginatus

Although coral dwelling fishes are common on coral reefs, the nature of their effect on the host corals is poorly understood. The present study, conducted in the Gulf of Eilat (Red Sea) between July 1989 and August 1990, demonstrated that the branching coral Stylophora pistillata (Esper) benefits, in two components of coral fitness, from the presence of the damselfish Dascyllus marginatus (Ruppell), an obligate coral dweller. The growth rate of damselfish-inhabited corals was significantly higher than that of corals without damselfish. This was observed, using two growth assessment methods, in long-term (>7 mo) comparisons between: (1) corals where the damselfish were experimentally removed versus corals with unaltered fish groups; and (2) naturally inhabited versus non-inhabited corals. The presence of damselfish did not affect the coral's specific (per surface area) reproductive output, whether it was assessed by the number of female gonads per polyp or by the number of planulae released cm-2 surface area d-1. However, the more rapid increase in branch size in damselfish-inhabited corals resulted in an apparent increase in the total reproductive output, with age, in growing corals. These findings demonstrate that the association between the damselfish D. marginatus and its host coral, S. pistillata, is mutualistic.

Extreme Diel Fluctuations of Oxygen in Diffusive Boundary Layers Surrounding Stony Corals.

The diffusive boundary layers surrounding sessile marine organisms have been implicated in controlling an organism's metabolism and growth. We studied boundary layers surrounding hermatypic corals by monitoring oxygen concentrations on a submillimetric scale. Oxygen concentration within the boundary layers varied from supersaturation during the day to anoxia at night, although the ambient water composition remained constant. Detailed mapping and oxygen measurements revealed diel oxygen fluctuations from supersaturation (373% air saturation) in the light to complete oxygen depletion at darkness in the massive coral Favia favus. Exposure to a 5-cm/s current reduced the boundary layer thickness from 2.44 mm to 1.90 mm, allowing more rapid oxygen exchange across the diffusive boundary layer. Similar patterns were found in the branching coral Stylophora pistillata. In massive corals, the thickness of the diffusive boundary layer was negatively correlated with the size of the polyp. We suggest that the distribution of corals in areas of differential turbulence is related to the thickness of the diffusive boundary layers surrounding them.

Size‐assortative Monogamy and Paternal Egg Care in a Coral Goby Paragobiodon echinocephalus

AbstractParagobiodon echinocephalus (Pisces; Gobiidae) inhabits the branching coral Stylophora pistillata. Only the largest two fish bred in a coral irrespective of group size, which was larger in larger corals. Breeding pairs consisted of a male and female of similar body size. Eggs were spawned on the coral branch and guarded by the male parent for about 4 days until hatching. Successive spawning occurred usually one day after hatching. The reproductive success of a pair, measured as the number of newly hatched larvae, was positively correlated with the body size of the male as well as the female. That is, not only female fecundity but also male ability of egg guarding were limited by body size almost equally. This should promote size‐assortative monogamy in the goby.

Senescence and dying signals in a reef building coral

Decreases in two physiological processes (reproduction and growth) have been shown to precede the advent of colony death in the branching coralStylophora pistillata. These diminutions were sometimes detectable even 6 months and more before any first visible sign of tissue mortality was observed.

Short-term fate of photosynthetic products in a hermatypic coral

The short-term fate of photosynthetic products within the tissues of the branching coral Stylophora pistillata (Esper) was studied at Eilat, Red Sea. Colonies of S. pistillata were labelled in situ with NaH 14CO 3 for 24 h and were periodically sampled after 4, 24, 48 h and 1 month. Amounts of 14C products were measured in the upper parts of the branches (up to 2.5 cm below the tips). Branches were divided into different fragments: branch-tips, mid-branches, and bases. All fragments below a branch-tip contain significantly more 14C products than the tip (the upper 0.5 cm), while no significant differences were recorded between all the other fragments. The rate of decrease in 14C materials was followed in 11 colonies. No significant loss was recorded in the first 24 h after incubation. After 48 h, a significant reduction was found only in one colony. After one month all experimental colonies showed a significant reduction in 14C materials. The retention rate in 14C materials in tips and bases within the same colony is approximately equal. This and the result that no gradual increase of 14C products in the tissue of the tips is recorded, exclude the possibility of significant translocation of 14C materials from bases to tips during the first month after incubation. It is suggested that the marked loss of photosynthetic products (up to 80%) is the result of a combination of several processes such as production of mucus, larval release, tissue growth, and metabolic requirements.