Abundance Of Zooxanthellae Research Articles

The Effect of Plastic Waste Attachment on Branching Coral to Zooxanthellae Abundance in the Kelapa Dua Island Waters, Seribu Islands

HighlightLight intensity from plastic waste was positively correlated with the abundance of zooxanthellae in corals.The abundance of zooxanthellae between sack plastic and clear plastic treatment tended to be the same.The treatment of packaging plastic was treated with the lowest light intensity.The treatment of black plastic was the treatment that produced the lowest abundance of zooxanthellae. AbstractCoral growth in Indonesia was being disrupted due to the continued threat of environmental change, such as littering to the beach. This study aimed to analyze the effect of the attachment of different colored plastic waste to the rate of zooxanthellae abundance on branching corals in Kelapa Dua Island waters. Branching coral colony samples consisted of the genus Acropora and Porites with a total of 15 fragments of coral colonies at the depth of 80-90 cm were tested with a treatment of the attachment plastic wastes (control, clear plastic, plastic sack, plastic packaging, and black plastic) for four days. The zooxanthellae abundance was calculated using the APHA (American Public Health Association) formula. The results of zooxanthellae abundance on the closure treatment of branching coral samples with black plastic and control had the lowest and highest values by 4.25 x 105 cells/cm2 and 1.38 x 106 cells/cm2. The results of the linear regression test showed that there was a significant relationship between plastic waste with low light intensity and a decrease of zooxanthellae abundance in coral colonies with the equation Y of 972.78x + 653402, determination index (R2) of 0.68, and correlation index (r) of 0.83. These results indicated that the attachment of plastic waste to branching coral colonies could be a stressor on coral animals in reducing light intensity, which caused a reduction of zooxanthellae abundance as coral endosymbiont.

THE EFFECT OF TEMPERATURE ON ZOOXANTHELLAE OF ISOPORA PALIFERA AND ACROPORA HYACINTHUS FROM KARANRANG ISLAND, INDONESIA

Climate change and global warming cause massive damage to the environment. One of the major events that arethreatening the marine ecosystem is coral bleaching. Coral bleaching occurs when corals are exposed to above or belownormal temperatures. The aims of this study are to compare the resistance of Isopora palifera and Acropora hyacinthusfrom Karanrang Island to temperature stress. Four treatment temperatures (28ºC, 30ºC, 32ºC, and 34ºC) were tested toassess the role of temperature stress and bleaching to Isopora palifera and Acropora hyacinthus for 48-hours. Theabundance of zooxanthellae counted as the temperature stress variable. The results showed that there was a difference ofcoral response tothe treatment based on the time of experiment, after 48-hours experimentexposed at temperaturetreatment of 34°C the abundance of zooxanthellae from Isopora paliferawas 0,06 x105 cm-2 and the abundance ofzooxanthellae from Acropora hyacinthus is 0,18 x105cm-2. In comparison between species, Isoporapalifera taken fromKaranrang Island was more resistant to temperature stress thanAcroporahyacinthus.

Effect of temperature on two reef-building corals Pocillopora damicornis and P. verrucosa in the Red Sea

The effects of temperature on two reef building corals Pocillopora damicornis and P. verrucosa inhabiting the Obhur Creek, a small embayment on the western, Red Sea coast of Saudi Arabia, was studied from December 2009 to November 2010. The overall annual range of seawater temperature in Obhur Creek was between 24.5°C and 33°C. Zooxanthellae abundance and diversity showed seasonal variations: the number of zooxanthellae in P. damicornis was slightly higher than in P. verrucosa, and the abundance of zooxanthellae of both species was low in summer and high during winter. The respiration rate of P. verrucosa did not vary between summer and winter, suggesting compensatory acclimation. In contrast, the respiratory rate in P. damicornis was lower in winter than in summer. During the winter season the metabolic rate was higher in both species owing to the optimum seawater temperature (30°C). As a result of the abundance of zooxanthellae and the optimum seawater temperature, the growth rates of the skeletons of the two coral species were higher in winter and lower in summer. In general, the results showed that P. verrucosa is more flexible with respect to temperature than P. damicornis. The difference in zooxanthellae thermal tolerances at 35°C may be due to the algal genotypes between the two species, resulting in P. damicornis becoming bleached as the rate of metabolism exceeds the rate of photosynthesis with increasing temperature.

In-situ Effects of Eutrophication and Overfishing on Physiology and Bacterial Diversity of the Red Sea Coral Acropora hemprichii

Coral reefs of the Central Red Sea display a high degree of endemism, and are increasingly threatened by anthropogenic effects due to intense local coastal development measures. Overfishing and eutrophication are among the most significant local pressures on these reefs, but there is no information available about their potential effects on the associated microbial community. Therefore, we compared holobiont physiology and 16S-based bacterial communities of tissue and mucus of the hard coral Acropora hemprichii after 1 and 16 weeks of in-situ inorganic nutrient enrichment (via fertilizer diffusion) and/or herbivore exclusion (via caging) in an offshore reef of the Central Red Sea. Simulated eutrophication and/or overfishing treatments did not affect coral physiology with respect to coral respiration rates, chlorophyll a content, zooxanthellae abundance, or δ 15N isotopic signatures. The bacterial community of A. hemprichii was rich and uneven, and diversity increased over time in all treatments. While distinct bacterial species were identified as a consequence of eutrophication, overfishing, or both, two bacterial species that could be classified to the genus Endozoicomonas were consistently abundant and constituted two thirds of bacteria in the coral. Several nitrogen-fixing and denitrifying bacteria were found in the coral specimens that were exposed to experimentally increased nutrients. However, no particular bacterial species was consistently associated with the coral under a given treatment and the single effects of manipulated eutrophication and overfishing could not predict the combined effect. Our data underlines the importance of conducting field studies in a holobiont framework, taking both, physiological and molecular measures into account.

Facilitation of coral reef biodiversity and health by cave sponge communities

Marine caves are understudied ecosystems that are frequently associated with coral reef communities; many are tidally influenced and may host a highly diverse sponge fauna. Although each cave represents a distinct habitat likely structured by site-specific hydrographic processes, a more complete understanding of the ecology of these communities requires com parative studies. Based on a gradient of sponge cover within 5 Bahamian caves, we conducted a natural experiment in sponge-derived nutrient enrichment of nearby patch reefs. We tested the hypothesis that water exiting the cave during low tide provides a nutrient-rich resource that facilitates the diversity and health of nearby reef communities. The percent cover and diversity of corals surrounding the openings of caves were significantly higher than in similar habitats farther removed from these communities. There was a significant correlation between percent sponge cover within the caves and nitrate concentrations in seawater flowing out of the caves, and δ15N stable isotope signatures indicated enrichment of the nearby reefs by sponge-derived nitrate. Zooxanthellae abundance and total protein concentration were higher in corals from reefs near cave entrances, suggesting that those corals benefited more from cave nutrients than did corals farther from cave openings. In addition to corals, percent algal cover increased near cave entrances, but these potential competitors of corals were kept in check by increased levels of herbivory relative to sites removed from cave mouths. As global environmental changes continue to impact coral reef ecosystems, diversity ‘hot spots’, such as these marine caves, could serve as refuges and ‘seedbanks’ for nearby dwindling reef habitats.

Is the response of coral calcification to seawater acidification related to nutrient loading?

The effect of decreasing aragonite saturation state (ΩArag) of seawater (elevated pCO2) on calcification rates of Acropora muricata was studied using nubbins prepared from parent colonies located at two sites of La Saline reef (La Reunion Island, western Indian Ocean): a back-reef site (BR) affected by nutrient-enriched groundwater discharge (mainly nitrate), and a reef flat site (RF) with low terrigenous inputs. Protein and chlorophyll a content of the nubbins, as well as zooxanthellae abundance, were lower at RF than BR. Nubbins were incubated at ~27°C over 2 h under sunlight, in filtered seawater manipulated to get differing initial pCO2 (1,440–340 μatm), ΩArag (1.4–4.0), and dissolved inorganic carbon (DIC) concentrations (2,100–1,850 μmol kg−1). Increasing DIC concentrations at constant total alkalinity (AT) resulted in a decrease in ΩArag and an increase in pCO2. AT at the beginning of the incubations was kept at a natural level of 2,193 ± 6 μmol kg−1 (mean ± SD). Net photosynthesis (NP) and calcification were calculated from changes in pH and AT during the incubations. Calcification decrease in response to doubling pCO2 relative to preindustrial level was 22% for RF nubbins. When normalized to surface area of the nubbins, (1) NP and calcification were higher at BR than RF, (2) NP increased in high pCO2 treatments at BR compared to low pCO2 treatments, and (3) calcification was not related to ΩArag at BR. When normalized to NP, calcification was linearly related to ΩArag at both sites, and the slopes of the relationships were not significantly different. The increase in NP at BR in the high pCO2 treatments may have increased calcification and thus masked the negative effect of low ΩArag on calcification. Removing the effect of NP variations at BR showed that calcification declined in a similar manner with decreased ΩArag (increased pCO2) whatever the nutrient loading.

New Method for Counting Bacteria Associated with Coral Mucus

The ability to count bacteria associated with reef-building corals in a rapid, reliable, and cost-effective manner has been hindered by the viscous and highly autofluorescent nature of the coral mucus layer (CML) in which they live. We present a new method that disperses bacterial cells by trypsinization prior to 4',6-diamidino-2-phenylindole (DAPI) staining and quantification by epifluorescence microscopy. We sampled seawater and coral mucus from Porites lobata from 6 reef sites influenced by wastewater intrusion and 2 reef sites unaffected by wastewater in Hawaii. Bacterial and zooxanthella abundances and cell sizes were quantified for each sample. Bacteria were more abundant in coral mucus (ranging from 5.3 x 10(5) +/- 1.0 x 10(5) cells ml(-1) to 1.8 x 10(6) +/- 0.2 x 10(6) cells ml(-1)) than in the surrounding seawater (1.9 x 10(5) +/- 0.1 x 10(5) cells ml(-1) to 4.2 x 10(5) +/- 0.2 x 10(5) cells ml(-1)), and the mucus-associated cells were significantly smaller than their seawater counterparts at all sites (P < 0.0001). The difference in cell size between mucus- and seawater-associated bacteria decreased at wastewater-influenced sites, where simultaneously mucus bacteria were larger and seawater bacteria were smaller than those at uninfluenced sites. The abundance of zooxanthellae in mucus ranged from 1.1 x 10(5) +/- 0.1 x 10(5) cells ml(-1) to 3.4 x 10(5) +/- 0.3 x 10(5) cells ml(-1). The frequency of dividing cells (FDC) was higher in the surrounding seawater than in mucus, despite finding that a 1,000-fold-higher zooxanthella biovolume than bacterial biovolume existed in the CML. Establishment of a standardized protocol for enumeration will provide the field of coral microbial ecology with the urgently needed ability to compare observations across studies and regions.

Mechanisms of habitat segregation between corallimorpharians: photosynthetic parameters and Symbiodinium types

Corallimorpharians are evolutionarily important relatives to reef-building corals, yet lit- tle is known about their ecophysiology. We demonstrate that physiological mechanisms determine, in part, the light-dependent distributional patterns of 2 corallimorpharians, Rhodactis rhodostoma and Discosoma unguja, on coral reefs in the northern Red Sea. Field measurements of the physiological parameters related to photosynthetic activity revealed that zooxanthellae abundance, chlorophyll a concentration, maximum quantum yield (Fv/Fm), and excitation pressure of Photosytem II (Qm) varied equally for both species among 3 depths. In contrast, laboratory measurements in 3 experimental light treatments — low light (LL), medium light (ML) and high light (HL) — revealed that D. unguja was more sensitive to HL than R. rhodostoma. Genetic characterization of their endosymbiotic algae using a PCR for the internal transcribed spacer region (ITS2) of nuclear ribosomal DNA showed that both R. rhodostoma and D. unguja contain Symbiodinium ITS2-type C1 symbionts in shallow areas, but that the algal assemblage were either Type C1 or Type D1a in both species in deeper areas. In reciprocal depth, light, and temperature manipulation experiments, bleached R. rhodostoma never shuffled Symbiodinium ITS2 types, however, some R. rhodostoma in the control treatment did. In contrast, some individuals of D. unguja shuffled Symbiodinium ITS2 types both in field-reciprocal experiments and laboratory-control treatments. Both species contained UV radiation absorbing com- pounds over a wide-depth range. We concluded that the photoacclimation mechanisms of R. rhodos- toma and D. unguja were influenced by both host- and symbiont-mediated factors. We hypothesize that a low abundance of D. unguja in shallow water was due to decreased tolerance to the high irra- diance found in host factors.

Application of ammonium to enhance the growth of giant clams ( Tridacna maxima) in the land-based nursery: effects of size class, stocking density and nutrient concentration

This study investigated the effects of ammonium (NH 4 +) enrichment and stocking density on the growth of juvenile Tridacna maxima throughout the land-based nursery stage. In four sequential experiments, clams of 5, 11, 16 and 18 mm shell length (SL) were maintained at low and high stocking densities in 60-l tanks with unfiltered seawater (8 l h −1) for 25 days. Throughout this period, clams received daily spikes of dissolved ammonium sulfate at concentrations of <1 (control), 20, 35 and 50 μM NH 4 + for the three smallest size classes of clams, and <1, 35, 50 and 80 μM NH 4 + for the largest size class. Our experiments simulated the conditions used to mass-produce clams of this species during the nursery phase. All individuals used in the four experiments were from the same cohort. The growth responses of T. maxima to ammonium enrichment were dependent on the size of the clams. For clams of 5 mm SL, both increase in mean wet weight and SL were significantly lower at 35 and 50 μM NH 4 + compared to control and 20 μM NH 4 + spikes. In contrast, increases in mean wet weight and SL of giant clams of 11, 16 and 18 mm SL were all significantly greater when ammonium was added, with the greatest increases in mean weight and SL occurring at the highest ammonium levels for the two largest size classes. The abundance of zooxanthellae per clam increased in response to addition of ammonium for clams of 11, 16 and 18 mm SL, but not for individuals of 5 mm SL. Stocking density had a variable effect on changes in mean weight, shell length and abundance of zooxanthellae. Values of all variables were significantly greater at low stocking densities for clams of 11 mm SL, but only marginally significant for most variables for clams of 16 and 18 mm SL. This study shows that addition of ammonium does not enhance growth of T. maxima during the early stages of rearing clams in the land-based nursery, but that relatively high levels of ammonium should be applied in the latter part of the nursery phase. This highlights the importance of identifying changes in nutrient requirements as juvenile giant clams grow.

Effects of butyltins on the symbiotic sea anemone Aiptasia pallida (Verrill)

Tributyltin (TBT) is a widespread biocide often used in antifouling paints. Leaching of TBT and of its butyltin derivatives into the marine habitat is known to have severe consequences on aquatic life. The present study was designed to determine the impact of butyltin exposure on sea anemones Aiptasia pallida (Verrill) and their symbiotic zooxanthellae. Sea anemones exposed to a nominal TBT concentration of 50 ng·l−1 in a flow-through system of sea water for 28 days showed a decreasing concentration of zooxanthellae within their tentacles, along with an increased number of bacterial aggregates in the ectoderm. Also observed were stimulated mucus secretion, thickening of the pedal disc ectoderm and a decreased number of undischarged nematocysts. Another group of sea anemones, fed 5 mg of contaminated mussel tissue (5 ng TBT·mg−1) daily for 28 days, showed a similar decrease in zooxanthellae abundance, increased occurrence of bacterial aggregates, and lowered amount of undischarged nematocysts, but none of the other symptoms. Replenishment of the lost zooxanthellae was apparently prevented, either through control over the mitotic activity of the vegetal cells by the contaminated sea anemones or as a result of the toxic effects of butyltins. Expulsion of zooxanthellae, which appeared to favour butyltin depuration, is a common response of symbiotic cnidarians toward stressful conditions. In this case, it occurred after exposure to very low concentrations of butyltins, stressing the high toxicity of these contaminants. The concurrent increase in the number of bacterial aggregates in the ectoderm showed that they proliferate when zooxanthellae depart. This bacterial growth can be interpreted as the first observation of a microbial infection promoted by low-level exposure to chemical contamination from sea water and food. However, the exact nature of the bacteria–anemone relation and whether it could be a form of auxiliary symbiosis instead of an infection is not clear. The adverse effects of butyltins on the zooxanthellae–anemone symbiosis developed under concentrations similar to those currently measured along numerous tropical coasts, emphasizing the threat faced by shallow water species of coral reefs.

Extension rate: A primary control on the isotopic composition of West Indian (Jamaican) scleractinian reef coral skeletons

Large variations in skeletal microarchitecture, and in the carbon and oxygen isotopic composition of the skeleton, exist within single calices and over the surfaces of single colonies of various species of West Indian (Jamaican) scleractinian reef corals. Rapidly extending parts of individual colonies are depleted in both C13 and O18 regardless of the abundance of zooxanthellae in the overlying tissues. We suggest that this relationship is due to active translocation of organic compounds to sites of rapid calcification. Considerable variation in isotopic composition is found in skeletons of different specimens of the same species even when the skeletons are sampled in a consistent manner, come from the same locality and depth, and have a comparable growth history. The isotopic composition of the scleractinian skeleton is vastly more complex than has heretofore been realized.