Coral Larvae Research Articles

Bacterial Communities in Coral Offspring Vary Between in situ and ex situ Spawning Environments

Examining the bacterial communities of offspring is key to understanding the establishment of coral-bacteria associations. Although high sensitivity to the environment is expected, previous studies have only examined bacterial communities of coral offspring in ex situ (laboratory) environments, not in in situ (field) environments. Here, we examined and compared the effect of ex situ and in situ environments on bacterial communities of newly released offspring (eggs and larvae) and their maternal colonies in two phylogenetically distant coral species with different reproductive modes: Dipsastraea speciosa (Scleractinia; spawner) and Heliopora coerulea (Octocorallia; brooder). Our results demonstrated that the spawning environments do not affect the bacterial composition in maternal colonies, but influence that of the offspring (eggs of D. speciosa and larvae of H. coerulea). Dominant bacterial operational taxonomic units (OTUs) varied between in situ and ex situ environments in the eggs of D. speciosa. The composition of bacterial communities among larvae of H. coerulea samples was more diverse in in situ environments than in ex situ environments. This study provides the first information on in situ bacterial communities in coral eggs and larvae and highlights their sensitivities to the local environment. Future studies must take into consideration the influence of ex situ environments on bacterial communities in coral offspring.

Effects of cryopreservation on the ultrastructure of coral larvae

Effects of cryopreservation on the ultrastructure of coral larvae

Removal of macroalgae from degraded reefs enhances coral recruitment

Declining coral cover on tropical coral reefs often results in a concomitant increase in macroalgae. When proliferation of macroalgae persists outside regular seasonal growth, it can shift the ecosystem dominance away from corals into a permanently altered system. Such an altered system is unlikely to recover naturally, despite ample supply of coral larvae, as coral settlement and survival is reduced by the presence of macroalgae. Physical removal of macroalgae has been proposed to overcome this biotic barrier to recovery, although empirical evidence demonstrating the effects of removal on phase‐shifted reefs is lacking. Here, we manually removed macroalgae from twelve 25 m2 experimental plots (88.5 ± 6.2 kg wet weight per plot; 90% benthic cover decrease) on a degraded reef prior to coral mass spawning across 2 years and recorded the number of coral recruits to settlement tiles and natural substrata. Four months after each spawning event, we found a threefold increase in coral recruits to tiles in plots where macroalgae had been removed (n = 12 plots; February 2019: mean 45.9 ± 12.7 recruits per tile; February 2020: mean 53.9 ± 5.9 recruits per tile) compared to control plots where macroalgae remained (n = 12 plots; February 2019 mean: 13.6 ± 2.8 recruits per tile; February 2020 mean: 17.5 ± 3.5 recruits per tile). These results suggest that, at small scales, macroalgae removal may be a useful intervention to boost recruitment on degraded reefs. Longer‐term monitoring is needed to document if coral survivorship, growth, and subsequent reef recovery occurs.

Temperature-mediated acquisition of rare heterologous symbionts promotes survival of coral larvae under ocean warming.

Reef‐building corals form nutritional symbioses with endosymbiotic dinoflagellates (Symbiodiniaceae), a relationship that facilitates the ecological success of coral reefs. These symbionts are mostly acquired anew each generation from the environment during early life stages (“horizontal transmission”). Symbiodiniaceae species exhibit trait variation that directly impacts the health and performance of the coral host under ocean warming. Here, we test the capacity for larvae of a horizontally transmitting coral, Acropora tenuis, to establish symbioses with Symbiodiniaceae species in four genera that have varying thermal thresholds (the common symbiont genera, Cladocopium and Durusdinium, and the less common Fugacium and Gerakladium). Over a 2‐week period in January 2018, a series of both no‐choice and four‐way choice experiments were conducted at three temperatures (27, 30, and 31°C). Symbiont acquisition success and cell proliferation were measured in individual larvae. Larvae successfully acquired and maintained symbionts of all four genera in no‐choice experiments, and >80% of larvae were infected with at least three genera when offered a four‐way choice. Unexpectedly, Gerakladium symbionts increased in dominance over time, and at high temperatures outcompeted Durusdinium, which is regarded as thermally tolerant. Although Fugacium displayed the highest thermal tolerance in culture and reached similar cell densities to the other three symbionts at 31°C, it remained a background symbiont in choice experiments, suggesting host preference for other symbiont species. Larval survivorship at 1 week was highest in larvae associated with Gerakladium and Fugacium symbionts at 27 and 30°C, however at 31°C, mortality was similar for all treatments. We hypothesize that symbionts that are currently rare in corals (e.g., Gerakladium) may become more common and widespread in early life stages under climate warming. Uptake of such symbionts may function as a survival strategy in the wild, and has implications for reef restoration practices that use sexually produced coral stock.

High CO2 inhibits substratum exploration and settlement of coral larvae

Biological and physical factors affecting coral recruitment are critical in influencing the recovery of coral communities after disturbance. While ocean acidification (OA) can reduce coral settlement and the early growth of coral recruits, the impact of OA on coral larval swimming behavior is unknown. Here, we investigated the effects of elevated CO2 on the swimming behavior and settlement of coral larvae of 2 common Acropora species. Larvae were exposed to 4 CO2 partial pressure (pCO2) conditions consistent with the current Intergovernmental Panel for Climate Change predictions for the next few centuries (pCO2: 393, 853, 1485 and 3022 µatm; pH: 8.1, 7.8, 7.6 and 7.3) in 2 laboratory experiments. We found that bottom exploration, expressed as the proportion of A. cytherea and A. pulchra larvae present in the bottom part of experimental cylinders, decreased by 92 and 98%, respectively, from the ambient to highest CO2 treatment. When offered the choice to settle on the crustose coralline algae Titanoderma prototypum, a well-known positive settlement cue, the percentage of larvae that settled on the fragments declined rapidly as pCO2 increased, with no larvae settling in the highest CO2 treatment. These results suggest that OA may negatively affect coral recruitment via direct effects on larval swimming behavior, with larvae avoiding benthic probing in response to high CO2.

A Numerical Analysis on Coral Larval Networks across Reef Areas on the Northwest Coast of Okinawa Main Island, Japan

Coral bleaching has recently occurred extensively over the world’s oceans, primarily due to high water temperatures. Mesophotic corals that inhabit at depths of approximately 30–150 m are expected to survive during bleaching events and to reseed shallow water corals afterward. In particular, in Okinawa, Japan, mesophotic coral ecosystems (MCEs) have been reported to serve as a refuge to preserve genotypic diversities of bleaching-sensitive corals. Connectivity of larval populations between different habitats is a key element that determines the area to be conserved for desirable coral ecosystems. Coral larvae generally behave passively to the surrounding currents and are transported by the advective and dispersive effects of ambient ocean currents. Thus, numerical ocean circulation models enable us to quantify connectivity with detailed spatiotemporal network structures. Our aim in this study is to quantify the short-distance and vertical connectivity of coral larvae in reef areas on the northwest coast of Okinawa Main Island. For the reason that both short-distance and vertical larval transport are influenced by complex nearshore topography, a very high-resolution 3-D circulation model is required. Therefore, we developed a quadruple nested high-resolution synoptic ocean model at a lateral spatial resolution of 50 m, coupled with an offline 3-D Lagrangian particle-tracking model. After validation of the developed model, short-distance horizontal coral connectivity across reef areas on the northwest coast was successfully evaluated. Furthermore, a series of Lagrangian particle release experiments were conducted to identify the vertical coral migration and 3-D connectivity required for the preservation of MCEs. The model revealed that coral larvae released from the semi-enclosed areas tended to remain near the source area, whereas they were diffused and dispersed gradually with time. The mesophotic corals were dispersed vertically to the deeper zone below the mixed layer, while upward transport occurred to induce the mesophotic corals to emerge near the surface, under the influence of the surface mixed layer. The model results solidly indicated significant connectivity between MCEs and shallow coral ecosystems.

Hypoxia as a physiological cue and pathological stress for coral larvae.

Ocean deoxygenation events are intensifying worldwide and can rapidly drive adult corals into a state of metabolic crisis and bleaching-induced mortality, but whether coral larvae are subject to similar stress remains untested. We experimentally exposed apo-symbiotic coral larvae of Acropora selago to deoxygenation stress with subsequent reoxygenation aligned to their night-day light cycle, and followed their gene expression using RNA-Seq. After 12h of deoxygenation stress (~2mg O2 /L), coral planulae demonstrated a low expression of HIF-targeted hypoxia response genes concomitant with a significantly high expression of PHD2 (a promoter of HIFα proteasomal degradation), similar to corresponding adult corals. Despite exhibiting a consistent swimming phenotype compared to control samples, the differential gene expression observed in planulae exposed to deoxygenation-reoxygenation suggests a disruption of pathways involved in developmental regulation, mitochondrial activity, lipid metabolism, and O2 -sensitive epigenetic regulators. Importantly, we found that treated larvae exhibited a disruption in the expression of conserved HIF-targeted developmental regulators, for example, Homeobox (HOX) genes, corroborating how changes in external oxygen levels can affect animal development. We discuss how the observed deoxygenation responses may be indicative of a possible acclimation response or alternatively may imply negative latent impacts for coral larval fitness.

Unusual cohabitation: sipunculan‐associated solitary corals

Heterocyathus aequicostatus and Heteropsammia cochlea are two species of solitary Anthozoan corals endemic to the Indo-Pacific. These species live along sandy bottoms at depths equal to or greater than approximately 20 m; where present, they can be locally dense within small areas. Each of the two corals may engage in a unique form of commensalism with a sipunculan worm (Aspidosiphon sp), which moves the coral about on substrates and prevents it from becoming buried in sediment or toppled upside-down. The symbiosis begins when the coral larva settles on a small mollusk shell already inhabited by a sipunculan worm. The developing coral then grows over the shell, but leaves open an orifice so that the worm may survive and perform its commensal duties. Given that the two coral species belong to different taxonomic families, this is a possible example of convergent coevolution.

Changes in physiological performance and protein expression in the larvae of the coral Pocillopora damicornis and their symbionts in response to elevated temperature and acidification

Climate change causes ocean warming and acidification, which threaten coral reef ecosystems. Ocean warming and acidification cause bleaching and mortality, and decrease calcification in adult corals, leading to changes in the composition of coral communities; however, their interactive effects on coral larvae are not comprehensively understood. To examine the underlying molecular mechanisms of larval responses to elevated temperature and pCO2, we examined the physiological performance and protein expression profiles of Pocillopora damicornis at two temperatures (29 and 33 °C) and pCO2 levels (500 and 1000 μatm) for 5 d. Extensive physiological and proteomic changes were observed in coral larvae. The results indicated a significant decrease in net photosynthesis (PNET) and autotrophic capability (PNET/RD) of larvae exposed to elevated temperature but a marked increase in PNET and PNET/RD of larvae exposed to high pCO2 levels. Elevated temperature significantly reduced endosymbiont densities by 70% and photochemical efficiency, indicating that warming impaired host-symbiont symbiosis. Expression of photosynthesis-related proteins, the photosystem (PS) I reaction center subunits IV and XI as well as oxygen-evolving enhancer 1, was downregulated at higher temperatures in symbionts, whereas expression of the PS I iron‑sulfur center protein was increased under high pCO2 conditions. Furthermore, expression of phosphoribulokinase (involved in the Calvin cycle) and phosphoenolpyruvate carboxylase (related to the C4 pathway) was downregulated in symbionts under thermal stress; this finding suggests reduced carbon fixation at high temperatures. The abundance of carbonic anhydrase-associated proteins, which are predicted to exert biochemical roles in dissolved inorganic carbon transport in larvae, was reduced in coral host and symbionts at high temperatures. These results elucidate potential mechanisms underlying the responses of coral larvae exposed to elevated temperature and acidification and suggest an important role of symbionts in the response to warming and acidification.

Photosensitivity of the Bacterial Pigment Cycloprodigiosin Enables Settlement in Coral Larvae—Light as an Understudied Environmental Factor

The survival of coral reefs largely depends among other factors on the recruitment of a new generation of coral individuals that are more adapted to a rapidly changing climate and other anthropogenic stressors (e.g., pollution, sedimentation). Therefore, a better understanding of the coral settlement process, the molecules involved as well as crucial environmental drivers that control settlement success are needed. In this study, we identified a novel settlement inducer for the brooding scleractinian coral Leptastrea purpurea and highlight the importance of light for the settlement process. Crude extract of the red-pigmented bacterium Pseudoalteromonas rubra reliably triggered attachment and metamorphosis in L. purpurea larvae in less than 24 h. Prodigiosin (II) and the two derivatives, cycloprodigiosin (I) and 2-methyl-3-hexyl prodiginine (III) were isolated and structurally elucidated from the crude extract of P. rubra. We demonstrated that the photosensitive pigment cycloprodigiosin (I) was the responsible compound for attachment and metamorphosis in L. purpurea larvae. Under the tested light regimes (i.e., darkness, constant light and a dark-light alternation), cycloprodigiosin (I) triggered approximately 90% settlement at a concentration of 0.2 μg mL–1 under a 12 h alternating dark-light cycle, mimicking the light-flooded coral reef environment. Our findings enable for the first time a mechanistic understanding of the light-dependent larva to polyp transformation by discovering the novel bacterial settlement cue cycloprodigiosin and its photosensitivity as a determining factor for coral settlement.

Derivation of toxicity thresholds for gas condensate oils protective of tropical species using experimental and modelling approaches

Toxicity thresholds for dissolved oil applied in tropical ocean risk assessments are largely based on the sensitivities of temperate and/or freshwater species. To explore the suitability of these thresholds for tropical habitats we experimentally determined toxicity thresholds for eight tropical species for a partially weathered gas condensate, applied the target lipid model (TLM) to predict toxicity of fresh and weathered condensates and compared sensitivities of the tropical species with model predictions. The experimental condensate-specific hazard concentration (HC5) was 167 μg L−1 total aromatic hydrocarbons (TAH), with the TLM-modelled HC5 (78 μg L−1 TAH) being more conservative, supporting TLM-modelled thresholds for tropical application. Putative species-specific critical target lipid body burdens (CTLBBs) indicated that several of the species tested were among the more sensitive species in the TLM database ranging from 5.1 (coral larvae) to 97 (sponge larvae) μmol g−1 octanol and can be applied in modelling risk for tropical marine ecosystems.

Internal Wave Dynamics Over Isolated Seamount and Its Influence on Coral Larvae Dispersion

The internal wave dynamics over Rosemary Bank Seamount (RBS), North Atlantic, were investigated using the Massachusetts Institute of Technology general circulation model. The model was forced by M2-tidal body force. The model results are validated against the in-situ data collected during the 136th cruise of the RRS “James Cook” in June 2016. The observations and the modeling experiments have shown two-wave processes developed independently in the subsurface and bottom layers. Being super-critical topography for the semi-diurnal internal tides, RBS does not reveal any evidence of tidal beams. It was found that below 800-m depth, the tidal flow generates bottom trapped sub-inertial internal waves propagated around RBS. The tidal flow interacting with a cluster of volcanic origin tall bottom cones generates short-scale internal waves located in 100 m thick seasonal pycnocline. A weakly stratified layer separates the internal waves generated in two waveguides. Parameters of short-scale sub-surface internal waves are sensitive to the season stratification. It is unlikely they can be observed in the winter season from November to March when seasonal pycnocline is not formed. The deep-water coral larvae dispersion is mainly controlled by bottom trapped tidally generated internal waves in the winter season. A Lagrangian-type passive particle tracking model is used to reproduce the transport of generic deep-sea water invertebrate species.

Settlement yields in large‐scale in situ culture of Caribbean coral larvae for restoration

The dire state of coral reefs demands a rapid increase in the scale and efficiency of coral restoration methods in addition to mitigating local and global stressors. Larval propagation can provide vast numbers of coral propagules from an individual spawning event and increased genetic diversity in restored populations. The conversion of embryos collected from wild, broadcast‐spawning populations to settlers that can be outplanted to the reef is a key component of this production process. We present preliminary results on settlement yield (i.e. % embryos converted to settled polyps on outplantable substrates) following in situ mass culture in floating mesocosms (Coral Rearing In‐situ Basins, or CRIBs; 5.6 m3 volume, 5.4 m2 surface area) that can be implemented independent of land‐based facilities. Ten trials over 2 years were conducted in three locations using five Caribbean broadcast‐spawning species. Embryos were added at different stocking densities and settlement was scored 2–4 weeks after fertilization. Two trials failed, resulting in no effective settlement, but the remaining eight trials resulted in between 1% and 11% settlement yield (overall mean 5.3%) and 77–100% of substrates exposed to larvae acquired settlers (average production: 700 substrates trial−1). Parallel land‐based trials showed a similar range (<1–14%) and mean (3.6%) settlement yield over nine trials. These values are also similar to the previously published lab and field‐based trials using Pacific Acropora spp. Continued optimization of CRIB design and execution is expected to improve consistency, overall yield, and efficiency in the production of sexual propagules for restoration.

Plasticity of Porites astreoides Early Life History Stages Suggests Mesophotic Coral Ecosystems Act as Refugia in Bermuda

As the devastating impacts of global climate change and local anthropogenic stressors on shallow-water coral reefs are expected to rise, mesophotic coral ecosystems have increasingly been regarded as potential lifeboats for coral survival, providing a source of propagules to replenish shallower reefs. Yet, there is still limited knowledge of the capacity for coral larvae to adjust to light intensities that change with depth. This study elucidates the mechanisms underlying plasticity during early life stages of the coral Porites astreoides that enable survival across broad depth gradients. We examined physiological and morphological variations in larvae from shallow (8–10 m) and mesophotic (45 m) reefs in Bermuda, and evaluated differences in survival, settlement patterns and size among recruits depending on light conditions using a reciprocal ex situ transplantation experiment. Larvae released from mesophotic adults were found to have significantly lower respiration rates and were significantly larger than those derived from shallow adults, indicating higher content of energetic resources and suggesting a greater dispersal potential for mesophotic larvae compared to their shallow counterparts. Additionally, larvae released from mesophotic adults experienced higher settlement success and larger initial spat size compared to larvae from shallow adults, demonstrating a potential connection between parental origin, offspring quality, and recruitment success. Although both shallow and mesophotic larvae exhibited the capacity to survive and settle under reciprocal light conditions, all larvae had higher survival under mesophotic light conditions regardless of parental origin, suggesting that conditions experienced under low light may enable longer larval life, further extending the dispersal period. These results indicate that larvae from mesophotic Porites astreoides colonies are likely capable of reseeding shallow reefs in Bermuda, thereby supporting the Deep Reef Refugia Hypothesis.

Marine Fouling Characteristics of Biocomposites in a Coral Reef Ecosystem (Adv. Sustainable Syst. 9/2021)

Coral Reef Restoration In article number 2100089, Marco Contardi, Simone Montanoand, Athanassia Athanassiou and co-workers fabricate two biodegradable biocomposites based on starch–polydimethylsiloxane and soybean lecithin-wax-polyurethane. They are evaluated as scaffolds for the growth of oceanic organisms. Such materials placed underwater on the Maldivian lagoon for six months show biodegradation and the growth of several organisms, including coral larvae.

First evaluation of coral recruitment in Madagascar

The distribution of larvae and recruitment of scleractinians in the southwest region of Madagascar were evaluated for the first time between October 2013 and September 2014 at 3 sites. The presence of coral larvae (planulae) was monitored through weekly sampling using a plankton net and the recruitment rate evaluated by monthly sampling of the newly settled corals (<1 year stage) on recruitment tiles and by a monitoring of the recruitment of juveniles (1< Juveniles < 2 years) using the quadrat method. Planulae were present in the plankton for 9 months during the survey. The recorded mean annual density of planula varied from 0.43 ± 0.41 larvae m-3 to 3.23 ± 5.72 larvae m-3 depending on site, with a peak in larval density towards the end of November and the beginning of December. The variability in the occurrence of planula is very high and implied that the density observed in the year does not present a significant difference between the sites (pKW=0.33). The average density of total recruits was 620.13 ± 621.30 recruits m-2, 40.28 ± 50.97 recruits m-2 and 36.34 ± 33.82 recruits m-2, respectively at the sites of Nosy Tafara, Grande Vasque and Rose Garden. Seasonal distribution of coral recruitment was different between the sites. The mean annual density of newly settled recruits (< 1 month stage) was significantly higher at Nosy Tafara with 94.91±101.08 recruits m-2 compared to Grande Vasque and Rose Garden with 18.75±34.32 recruits m-2 and 11.57±18.47 recruits m-2 (pKW<0.001), respectively. The highest density of newly settled recruits was observed between October to December. Higher density of recruits was also observed in March at Nosy Tafara and in May at all three sites. Results of juvenile monitoring showed high rates (> 10 juveniles m-2) compared to other regions and the threshold, but it revealed high mortality among recruits. Coral recruitment in the southwest region of Madagascar was found to be high and could result in increased resilience of the coral reef assemblages.

Reconnecting reef recovery in a world of coral bleaching

AbstractCoral bleaching can have widespread impacts on reefs leaving many areas in need of coral recovery. While the long‐term mitigation of bleaching requires transitioning to a low carbon economy, local management has focused on approaches that seek refugia from or tolerance to bleaching stressors, reduce additional stressors, or facilitate coral recovery. Here, we describe a tactical response to coral bleaching events that seeks to identify the most important reefs for driving imminent recovery. A bleaching recovery algorithm is described that identifies those reefs that provide the most important sources of coral larvae that supply many reefs in the early stages of post‐bleaching recovery (i.e., reefs in need of coral larval supply). We describe the algorithm with a simple toy example and then apply it to the Great Barrier Reef, which has experienced three mass bleaching events in the last 5 yr. Once such reefs have been identified it makes practical sense to undertake a vulnerability assessment and if necessary reduce manageable stressors, such as outbreaks of crown‐of‐thorns starfish or anchor damage, so that critical sources of coral recovery are not depleted further. In short, algorithms like this can help managers target finite management resources, including restoration, to where they might be most effective in facilitating natural processes of recovery.

Dispersal Potential Index (DPi) As Alternative Indicator for Coral Larvae Dispersal Potential

Dispersal of coral larvae is influence by combination of multiple factors, yet comparisons are commonly displayed on two- or three-dimensional charts (i.e.: pelagic larvae duration vs. distance). Therefore, the present study implies the application of Dispersal Potential Index (DPi) based on the factors which influence the dispersal range and potential such as pelagic larvae duration (PLD), adult coral cover, current speed and depth variations. Each factor was given score from 1 to 10 based on their influence towards dispersal potential. The DPi was able to describe dispersal potential of Acropora larvae from two separated reef sites (Bidong Island and Kuantan Coastal Waters) which share common hydrodynamic pattern. It is suggested that Acroporid larvae in Kuantan coastal waters has greater dispersal potential than Bidong Island. DPi for Kuantan coastal waters was classified as intermediate dispersal range while DPi and Bidong Island was categorized as short dispersal range. This approach is arguably the first of its kind in describing the multiple factors for dispersal of coral larvae. The application of DPi is important especially for reef managers to estimate dispersal range of coral for a better marine ecosystem management.

Lipid profiling in chilled coral larvae

Coral reefs are disappearing worldwide as a result of several harmful human activities. The establishment of cryobanks can secure a future for these ecosystems. To design effective cryopreservation protocols, basic proprieties such as chilling tolerance and lipid content must be assessed. In the present study, we investigated chilling sensitivity and the effect of chilling exposure on the lipid content and composition of larvae belonging to 2 common Indo-Pacific corals: Seriatopora caliendrum and Pocillopora verrucosa. The viability of coral larvae incubated with 0.5, 1, and 2 M ethylene glycol (EG), propylene glycol (PG), dimethyl sulfoxide (Me2SO), methanol, or glycerol and kept at 5 °C for different time periods was documented. In addition, we investigated the content of cholesterol, triacylglycerol (TAG), wax ester (WE), sterol ester (SE), lysophosphatidylcholine, phosphatidylcholine, phosphatidylethanolamine, and several fatty acid (FA) classes in coral propagules incubated with 1 M PG or EG and kept at 5 °C for 6 h. Moreover, we examined seasonal changes in the aforementioned lipid classes in coral larvae. S. caliendrum incubated with 0.5 M PG or Me2SO and chilled for 2 h exhibited a viability rate of 11 ± 11%, whereas P. verrucosa exhibited a viability rate of 22 ± 14% after being chilled for 4 h. Furthermore, the results indicated that chilling exposure did not affect the content of any investigated lipid class in either species. The higher concentration of SE in P. verrucosa compared to S. caliendrum larvae may have contributed to the different cryotolerance displayed by the 2 larval species. A year-round lipid analysis of both coral larvae species revealed trends of homeoviscous adaptation and seasonal enhancement of lipid fluxes from symbionts to the host. During winter, the cholesterol/phospholipid ratio significantly increased, and P. verrucosa larvae exhibited an averagely decrease in FA chain lengths. During spring and summer, intracellular lipid content in the form of TAGs and WEs significantly increased in both species, and the average content of Symbiodiniaceae-derived FAs increased in P. verrucosa larvae. We concluded that the low cryotolerance displayed by S. caliendrum and P. verrucosa larvae is attributable to their chilling-sensitive membrane lipid profile and the high intracellular lipid content provided by their endosymbionts.

Kelangsungan Hidup Larva Planula Acropora sp dalam Pemeliharaan Terkontrol Kepadatan yang Berbeda

The survival of coral larvae as early phase of coral life is very important for their viability in environmen. This research aims to determine the survival of Acropora sp planula at different densities intensive nursery, and also to khow the critical survival time of them.. This research method was used experiment in density of larvae were held in control laboratory. The planula were rearing ini small container 200 ml of water while the lavae density were used namely 0.5; 1.0, 1.5, 2.0 larvae / ml. The results indicated that survival rate for larvae of different densities (0.5 larvae/ml; 1.0 larvae/ml; 1.5 larvae/ml; 2.0 larvae/m) did not show any significant difference (P>0.05). the highest survival rate of planula larvae was in the treatment with a density of 1.5 larvae/ml and the lowest from a density of 2.0 larvae/ml, and the most larval mortality was in the first 12 hours of rearing, due to the degree of adaptation of larvae to the rearing water medium in all treatment units, then death coral larvae decreased exponentially. This research will be very useful for efforts to restore coral reefs sexually, so as to reduce the impact of exploitation of coral seedlings which are often taken for asexual coral reef restoration as is often done throughout the world's coral reefs.