Trophic status and population density of zooxanthellae in hermatypic corals

Leletkin, V. A.

doi:10.1007/bf02759502

Cited by 8 publications

(7 citation statements)

References 71 publications

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“…This may imply a higher energetic investment by zooxanthellae of W deep corals as increased chl-a contents are usually caused by elevated chl-a concentrations per cell and not by multiplication of zooxanthellae numbers within the host tissue. A review by Leletkin ([ 71 ]) indicates that zooxanthellae abundances should remain relatively constant within the range of nutrient concentrations and light intensities measured during our study. This is further supported by similar zooxanthellae abundances in the tissue of P. lutea investigated in this study irrespective of exposure or water depth (own unpublished data, two-tailed U-test, p >> 0.05).…”

Section: Discussionmentioning

confidence: 83%

“…water depths), mainly caused by reduced respiration under lower light levels. Nevertheless, P. lutea ’s respiration rates were similar at most sites, except at E shallow, where elevated respiration rates may reflect an enhanced metabolism, due to a high-light history ([ 71 , 73 ]). A surplus of solar energy, which cannot be used for photochemical energy conversion, is mainly dissipated as heat, but also causes reversible photodamage.…”

Section: Discussionmentioning

confidence: 99%

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Benthic Reef Primary Production in Response to Large Amplitude Internal Waves at the Similan Islands (Andaman Sea, Thailand)

et al. 2013

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Coral reefs are facing rapidly changing environments, but implications for reef ecosystem functioning and important services, such as productivity, are difficult to predict. Comparative investigations on coral reefs that are naturally exposed to differing environmental settings can provide essential information in this context. One prevalent phenomenon regularly introducing alterations in water chemistry into coral reefs are internal waves. This study therefore investigates the effect of large amplitude internal waves (LAIW) on primary productivity in coral reefs at the Similan Islands (Andaman Sea, Thailand). The LAIW-exposed west sides of the islands are subjected to sudden drops in water temperature accompanied by enhanced inorganic nutrient concentrations compared to the sheltered east. At the central island, Ko Miang, east and west reefs are only few hundred meters apart, but feature pronounced differences. On the west lower live coral cover (-38 %) coincides with higher turf algae cover (+64 %) and growth (+54 %) compared to the east side. Turf algae and the reef sand-associated microphytobenthos displayed similar chlorophyll a contents on both island sides, but under LAIW exposure, turf algae exhibited higher net photosynthesis (+23 %), whereas the microphytobenthos displayed reduced net and gross photosynthesis (-19 % and -26 %, respectively) accompanied by lower respiration (-42 %). In contrast, the predominant coral Porites lutea showed higher chlorophyll a tissues contents (+42 %) on the LAIW-exposed west in response to lower light availability and higher inorganic nutrient concentrations, but net photosynthesis was comparable for both sides. Turf algae were the major primary producers on the west side, whereas microphytobenthos dominated on the east. The overall primary production rate (comprising all main benthic primary producers) was similar on both island sides, which indicates high primary production variability under different environmental conditions.

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Section: Discussionmentioning

confidence: 83%

Section: Discussionmentioning

confidence: 99%

Benthic Reef Primary Production in Response to Large Amplitude Internal Waves at the Similan Islands (Andaman Sea, Thailand)

et al. 2013

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“…Elevated ambient inorganic nutrient concentrations enable zooxanthellae to retain significantly more fixed carbon for their own metabolism, and consequently less of it is eventually translocated (Dubinsky and Jokiel, 1994). This reduced transfer of energy-rich photosynthates creates an insufficient diurnal energy supply in the host (Leletkin, 2000), and may consequently affect organic matter (OM) exudation, as up to 40% of carbon fixed by photosynthesis is being released into surrounding reef waters, most of it presumably as coral mucus (Crossland et al, 1980). Exudation of mucus fulfils important functions for corals as well as the entire reef ecosystem.…”

Section: Introductionmentioning

confidence: 99%

Inorganic nutrient availability affects organic matter fluxes and metabolic activity in the soft coral genus Xenia

Bednarz

Naumann

Niggl

et al. 2012

Journal of Experimental Biology

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SUMMARYThe release of organic matter (OM) by scleractinian corals represents a key physiological process that importantly contributes to coral reef ecosystem functioning, and is affected by inorganic nutrient availability. Although OM fluxes have been studied for several dominant reef taxa, no information is available for soft corals, one of the major benthic groups in tropical reef environments. Thus, this study investigates OM fluxes along with other key physiological parameters (i.e. photosynthesis, respiration and chlorophyll a tissue content) in the common soft coral genus Xenia after a 4-week exposure period to elevated ammonium (N; 20.0mmoll ). Although DOC uptake significantly increased in the N treatment, POC flux was not affected. The P treatment significantly enhanced PN release as well as photosynthesis and respiration rates, suggesting that autotrophic carbon acquisition of zooxanthellae endosymbionts influences OM fluxes by the coral host. Our physiological findings confirm the significant effect of inorganic nutrient availability on OM fluxes and key metabolic processes for the soft coral Xenia, and provide the first clues on OM cycles initiated by soft corals in reef environments exposed to ambient and elevated inorganic nutrient concentrations.

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“…If phagotrophic mimicry is the main strategy employed by Symbiodinium spp., then proper functioning of photosynthesis is vital to avoid detection. The APH predicts that failure to conform to host cellular expectations will lead to detection, digestion and/or expulsion, and might explain observations of hosts digesting their own symbionts (Boschma, 1925; Titlyanov et al , 1996; Leletkin, 2000; Downs et al , 2009; Dunn & Weis, 2009). While we recognize that the dynamics of infection and recognition are complicated (Davy, Lucas & Turner, 1997; Rodriguez‐Lanetty et al , 2006), we suggest that symbiosome‐based mimicry of an active phagosome is a useful heuristic for evaluating zooxanthella symbioses.…”

Section: The Arrested Phagosome Hypothesismentioning

confidence: 99%

The magnesium inhibition and arrested phagosome hypotheses: new perspectives on the evolution and ecology of Symbiodinium symbioses

Hill

2012

Biological Reviews

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Zooxanthella symbioses are arguably the most important ecological interaction on coral reefs because they energetically subsidize the entire community, and enhance the calcification process that provides structure for all other organisms. While we have developed a detailed understanding of the diversity among and within the Symbiodinium clades, we currently lack a mechanistic explanation for which factors favoured zooxanthella invasion of the intracellular habitat in heterotrophic hosts, and for what molecular mechanisms permit residence within the cell. We propose two hypotheses that explain important evolutionary and ecological features of zooxanthella symbioses. The magnesium inhibition hypothesis (MIH) states that increases in the Mg/Ca ratio in sea water that occurred over the last 100 million years created a situation where Mg(2+) inhibited Ca(2+) transport to zooxanthellae. The MIH predicts, among other things, that the intracellular niche was invaded as a response to this abiotic stressor. The arrested phagosome hypothesis (APH) states that Symbiodinium spp. mimic host cell endosomal digestive machinery via the symbiosome to appear like digesting prey through perpetual release of zooxanthella-derived compounds. The APH represents a subtle but important distinction from previous hypotheses regarding interactions between symbiont and host at the cellular level. The APH predicts that symbionts tune rates of material release to match expectations of host cellular machinery. An outcome of the APH is that intra-host residence time becomes a vital parameter to consider. Both hypotheses shift control of the symbiosis away from the host, and instead focus attention on the niche requirements of Symbiodinium spp.

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Trophic status and population density of zooxanthellae in hermatypic corals

Cited by 8 publications

References 71 publications

Benthic Reef Primary Production in Response to Large Amplitude Internal Waves at the Similan Islands (Andaman Sea, Thailand)

Benthic Reef Primary Production in Response to Large Amplitude Internal Waves at the Similan Islands (Andaman Sea, Thailand)

Inorganic nutrient availability affects organic matter fluxes and metabolic activity in the soft coral genus Xenia

The magnesium inhibition and arrested phagosome hypotheses: new perspectives on the evolution and ecology of Symbiodinium symbioses

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