Effects of Temperature and Salinity on Coral Bleaching in Laboratory

Coral bleaching occurs when cell density or the concentration of photosynthetic pigments of the endosymbionts, zooxanthellae are decreased. This incident may possibly be caused by some environmental stresses, especially under conditions of elevated temperature, decrease in water salinity, or a combination of these factors. To determine the role of temperature and salinity on zooxanthellae and coral bleaching this study was conducted in aquariums under laboratory conditions on cauliflower coral Pocillopora damicornis. The samples were collected from three sites around Samaesan Island, Chonburi, Thailand. Three sets of experiments were conducted at three levels of temperature: room temperature 27 (control), 30, and 33 oC respectively. At each temperature level, three levels of salinities; 10, 20 and 30 (control) psu were tested as well. Coral bleaching percentage and zooxanthellae density in the water column were observed every 6 hours during the period of 72 hours. The results showed that when coral exposed to the highest temperature (33 oC) under the lowest salinity (10 psu), 50-90% bleaching was found and higher symbiont densities in the water column were detected. These results suggested that the combination of the high temperature and low salinity had synergistic effects on coral bleaching and zooxanthellae.

Individual and Interactive Effects of Ocean Warming and Acidification on Adult Favites colemani

Tropical coral reefs are threatened by local-scale stressors that are exacerbated by global ocean warming and acidification from the post-industrial increase of atmospheric CO2 levels. Despite their observed decline in the past four decades, little is known on how Philippine coral reefs will respond to ocean warming and acidification. This study explored individual and synergistic effects of present-day (pH 8.0, 28°C) and near-future (pH 7.7, 32°C) scenarios of ocean temperature and pH on the adult Favites colemani, a common massive reef-building coral in Bolinao-Anda, Philippines. Changes in seawater temperature drive the physiological responses of F. colemani, whereas changes in pH create an additive effect on survival, growth, and photosynthetic efficiency. Under near-future scenarios, F. colemani showed sustained photosynthetic competency despite the decline in growth rate and zooxanthellae density. F. colemani exhibited specificity with the Cladocopium clade C3u. This coral experienced lower growth rates but survived projected near-future ocean warming and acidification scenarios. Its pH-thermal stress threshold is possibly a consequence of acclimation and adaptation to local environmental conditions and past bleaching events. This research highlights the importance of examining the susceptibility and resilience of Philippine corals to climate-driven stressors for future conservation and restoration efforts in the changing ocean.

Physiological responses of scleractinian corals in marginal habitat

Polapa FS, Werorilangi S, Ali SM, Jompa J. 2021. Physiological responses of scleractinian corals in marginal habitat. Biodiversitas 22: 4011-4018. This study aims to analyze physiological differences in corals in marginal habitats. Under different conditions, the production/respiration (P/R) ratio and photobiology of various coral genera were compared. Samples were taken from three coral reef zones representing typical reef habitats and from the mangrove ecosystem as a marginal habitat. Surveys revealed two coral genera surviving in extreme conditions (marginal habitat). The P/R ratio measurements indicated that corals living in the mangrove ecosystem tend to be heterotrophic. This was supported by observations of colonies with tentacles extended from the corallites. Furthermore, Porites living in the mangrove habitat consume more O2 directly than saving it for other purposes, such as growth. The genus Dipsastraea exhibited elevated zooxanthellae density in the mangrove ecosystem, whereas Porites exhibited similar densities in both ecosystems.

Improper Diving Behavior Affects Physiological Responses of Acropora hyacinthus and Porites cylindrica

Human activities beyond ecosystem capacity have resulted in serious effects on corals worldwide. Nowadays, many studies have focused on the influence of diving activities on coral communities, while the knowledge of physiological changes under corresponding environmental stresses remains largely undetermined. In the study, we aimed to investigate the physiological effects of touching, ammonia nitrogen enrichment (5 μmol⋅L–1), and sediment cover (particle size of less than 0.3 mm), which simulated improper self-contained underwater breathing apparatus (SCUBA) diving behaviors, on Acropora hyacinthus and Porites cylindrica in Wuzhizhou Island, the South China Sea. For A. hyacinthus, continuous touching caused the tentacles to shrink and secrete mucus, which consumed energy and dissolved oxygen. The skeletal growth rate was decreased by 72% compared with the control group. There was a rapid decline of Fv/Fm and alpha under the dual impacts of high ammonia nitrogen and touching, while the Chl a concentration and tissue biomass were decreased by 36 and 28% compared with touching alone, respectively. High ammonia nitrogen and touching increased the concentrations of lipid and protein. Nevertheless, zooxanthellae density was increased by 23% to relieve the effects of a lower concentration of Chl a in a high nutrient environment. Constant touching and sediment cover in diving areas with elevated ammonia content affected the photosynthesis and respiration of corals, and a significant decrease was observed for lipid, zooxanthellae density, and Chl a concentration. Coral bleaching occurred on day 7. For P. cylindrica, the decreasing magnitude of Fv/Fm and alpha under different stresses in the subsequent phase was less compared with A. hyacinthus. The contents of carbohydrate and protein under continuous touching were decreased by 7 and 15% compared with the control group, respectively, causing negative growth. Under the dual influences of high ammonia nitrogen and continuous touching, all energy reserves were significantly lower. Repeated touching and sediment cover in diving areas containing high ammonia content increased the concentrations of lipid and protein compared with the touching and high nutrient treatment group likely because that Porites associated with C15 zooxanthella increased heterotrophic feeding to compensate for restricted symbiodiniaceae photosynthesis. Additionally, P. cylindrica produced mucus to aid the removal of sediment, so that corals didn’t obviously bleach during the experiment. Collectively, P. cylindrica was more resistant to diving activities than A. hyacinthus which only relies on photoautotrophy. To ensure the sustainable development of coral reef dive tourism, it is necessary to strengthen the supervision of diving behaviors, rotate the diving areas, and conduct regular assessments on the coral status.

Impact of ocean warming and ocean acidification on asexual reproduction and statolith formation of the symbiotic jellyfish Cotylorhiza tuberculata

Ocean acidification and warming are challenging marine organisms and ecosystems around the world. The synergetic effects of these two climate change stressors on jellyfish remain still understudied. Here, we examine the independent and combined effects of these two environmental variables on polyp population dynamics of the Mediterranean jellyfish Cotylorhiza tuberculata. An experiment was conducted to examine asexual reproduction by budding and strobilation considering current and ca. 2100 winter (Trial 1, 36 days) and summer (Trial 2, 36 days) conditions under the RCP8.5 (IPCC 2013). In Trial 1, a temperature of 18°C and two pH levels (current: 7.9 and, reduced: 7.7) were tested. Trial 2 considered two temperature levels 24°C and 30°C, under current and reduced acidification conditions (8.0 and 7.7, respectively). Ephyrae size and statolith formation of released ephyrae from polyps exposed to summer temperatures under both acidification treatment was also analyzed. Zooxanthellae density inside the polyps throughout the experiment was measured. C. tuberculata polyps could cope with the conditions mimicked in all experimental treatments and no significant effect of pH, temperature, or the combination of both variables on the abundance of polyps was observed. At 18°C, strobilation was reduced under high PCO2 conditions. Under summer treatments (24°C and 30°C), percentage strobilation was very low and several released ephyrae suffered malformations and reduced size, as a consequence of reduced pH and elevated temperatures, separately. The number of statoliths was not affected by pH or temperature, however, bigger statoliths were formed at elevated temperatures (30°C). Finally, zooxanthellae density was not affected by experimental conditions, even if, the duration of the experiment significantly affected symbiont concentration. Our results show that even though polyps of C. tuberculata would thrive the future worst scenario predicted for the Mediterranean Sea, their capacity to undergo a proper strobilation and to produce healthy ephyrae will be more vulnerable to climate induced environmental conditions, thereby affecting medusae recruitment and, therefore, population dynamics of the species.

Kondisi Terumbu Karang Di Kepulauan Seribu Dalam Kaitan Dengan Gradasi Kualitas Perairan

The increasing of Jakarta land activies caused eutrophication, so that it changes species composition and decreasing of number of species. The sea within the high of eutrophication has correlation with the high growth of alga, depletion of oxygen and change of coral species composition. These researchs was done at coral reef ecosystem of Lancang Island, Pari Island and Payung Island, whereas there are part of Seribu Island Cluster. The aims of research was evaluating of nutrient enrichment effect to morphology and functional of coral reef condition. Morphology figures are showed by basic cover, whereas functional aspects are evaluated by zooxanthellae density. The results are showed that the high eutrophication is significantly correlated with main land of Java Island distance. The increasing of nutrient enrichment is significantly to change profile of coral reef and zooxanthellae densities.

HUBUNGAN KANDUNGAN NITRAT DENGAN DENSITAS ZOOXANTHELLAE PADA BEBERAPA JENIS KARANG DI REEF FLAT PULAU PARI KEPULAUAN SERIBU JAKARTA

ABSTRAKPulau Pari merupakan salah satu pulau yang berada di tengah-tengah gugusan. Terumbu karang merupakan ekosistem pesisir yang memiliki produktivitas tinggi. Nitrat merupakan nutrien sebagai salah satu faktor penentu terpeliharanya produktivitas perairan, maka penelitian ini akan mempelajari dukungan nitrat di dalam polip karang dan pengaruhnya terhadap keberadaan zooxanthellae. Tujuan dari penelitian ini adalah untuk mengetahui keberagaman jenis karang, faktor lingkungan yang mempengaruhi karang, kandungan nitrat dan densitas zooxanthellae pada beberapa jenis karang di reef flat Pulau Pari Kepulauan Seribu Jakarta. Penelitian ini dilaksanakan pada bulan Maret-April 2016 dengan metode deskriptif. Hasil penelitian yang diperoleh jenis karang yang dominan adalah Acropora sp., Porites sp., dan Montipora sp., dengan penutupan karang hidup di stasiun I (dermaga) 36,4% kategori sedang, stasiun II (pemukiman penduduk) 22,4% kategori buruk dan stasiun III (jauh dari aktivitas penduduk) 67,2% kategori baik. Koefisien determinasi R2 antara nitrat dengan densitas zooxanthellae pada masing-masing jenis karang dominan memiliki nilai R² yang berbeda yaitu karang Acropora palifera diperoleh R²= 0.787 dapat diartikan bahwa variabel bebas X memiliki pengaruh kontribusi sebesar 78,7% terhadap variabel Y 21,3%, pada jenis karang Acropora divaricata diperoleh R²= 0.989 memiliki pengaruh kontribusi sebesar 98,9% terhadap variabel Y 1,1% dan jenis karang Porites cylindrica R²= 0.955 memiliki pengaruh kontribusi sebesar 95,5% terhadap variabel Y 4,5% lainnya dipegaruhi faktor lain diluar variabel X dari hasil tersebut menunjukkan bahwa nilai R² diatas 0,5 yang berarti semakin erat hubungan antara variabel X dan Y. Semakin tinggi kandungan nitrat di dalam polip karang, maka semakin tinggi pula densitas zooxanthellae yang dikandungnya. Kata kunci: Beberapa Jenis Karang; Nitrat; Densitas Zooxanthellae; Pulau Pari ABSTRACT Pari Island is one island in the middle of the Thousand Islands cluster. Nitrate is a nutrient as a determining factor for the preservation of marine productivity, nutrients becomes an important factor. The problem is, whether the support is derived from the availability of nitrate in the water or in the coral polyps. Related to the above, this research will study the nitrate support in coral polyps and their effects on the presence of zooxanthellae. The purpose of this study is to determine the diversity of coral species, environmental factors affecting the coral, nitrate content and the density of zooxanthellae in some types of coral on the Pari Island Reef Flat in Thousand Islands Jakarta. This study was conducted in March to April 2016, with descriptive method. The results obtained are the the dominant coral species Acropora sp., Porites sp., and Montipora sp., With live coral cover in the station I (pier) of 36,4% medium category, station II (residential) of 22.4% poor category and station III (away from the population activity) of 67,2% good category.The coefficient of R2 determination between nitrate with a density of zooxanthellae in each the dominant coral species have different values R² is Acropora palifera obtained R²= 0.787 means that the independent variable X has the effect of a contribution of 78,7% to 21,3% Y variables, the coral species Acropora divaricata obtained R²= 0.989 has the effect of a contribution for 98,9% to 1,1% Y variables and coral species Porites cylindrica R²= 0.955 has the effect of a contribution of 95,5% to other variable Y 4,5% influenced other than the variable X of the results showed that the value of R² above 0,5 which means that the closer the relationship between the variables X and Y. the higher the nitrate content in coral polyps, the higher the density of zooxanthellae contains. Keywords: Types of Corals; Nitrate; Zooxanthellae Density; Pari Island

Densitas Simbion Alga Zooxanthellae pada Anemon Laut Stichodactyla gigantea Alam dan Hasil Reproduksi Aseksual

The aims of this research were to discover the density of algae symbiont of zooxanthellae in the giant carpet anemone (Stichodactyla gigantea) from the nature and the asexual reproduction by longitudinal body fragmentation technique. The research was conducted from October 2007 to July 2008, in The Hatchery of University of Hasanuddin Marine Station in Barrang Lompo Island for seed production and coral reefs area of Barrang Lompo Island for the implementation of culture. The series of study was started with parental collection and acclimatization of anemones, fragmentation of the body, culturing anemones in the coral reefs area and collection of algae zooxanthellae which is conducted every two months. The results of this study indicated the difference of zooxanthellae density from nature and asexual reproduction anemones. The highest density of zooxanthellae algae found in the non fragmented or nature population (AA) (10.84 x 106 cell/cm2), followed by the anemone which was resulted from 2 parts body fragmentation (AF2) (10.24 x 106 cells/cm2), and the anemone which was resulted from 4 parts body fragmentation (AF4) (9.17 x 106 cell/cm2 ). Whereas, between the good coral (KB) and bad coral (KR) not significant.