Dr Ross Hill

Sinutok, S., Hill, R., Doblin, M.A. & Ralph, P.J. 2013, 'Diurnal photosynthetic response of the motile symbiotic benthic foraminiferan Marginopora vertebralis', Marine Ecology Progress Series, vol. 478, pp. 127-138.

Buxton, L.J., Takahashi, S., Hill, R. & Ralph, P.J. 2012, 'Variability in the primary site of photosynthetic damage in Symbiodinium sp. (Dinophyceae) exposed to thermal stress', Journal of Phycology, vol. 48, no. 1, pp. 117-126.
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Exposure to elevated temperature is known to cause photosynthetic inhibition in the coral symbiont Symbiodinium sp. Through the use of the artificial electron acceptor, methyl viologen, this study identified how reduced photosynthetic capacity occurs as a result of inhibition up- and/or downstream of ferredoxin in Symbiodinium sp. in hospite and in culture. Heterogeneity between coral species and symbiont clades was identified in the thermal sensitivity of photosynthesis in the symbionts of the scleractinian corals Stylophora pistillata and Pocillopora damicornis, as well as among Symbiodinium cultures of clades A, B, and C. The in hospite symbionts of S. pistillata and the cultured clade C Symbiodinium both exhibited similar patterns in that their primary site of thermal inhibition occurred downstream of ferredoxin at 32 degrees C. In contrast, the primary site of thermal inhibition occurred upstream of ferredoxin in clades A and B at 32 degrees C, while at 34 degrees C, all samples showed combined up- and downstream inhibition. Although clade C is common to both P. damicornis and S. pistillata, the manner of thermal inhibition was not consistent when observed in hospite. Results showed that there is heterogeneity in the primal site of thermal damage in Symbiodinium among coral species and symbiont clades.

Gilbert, J.A., Hill, R., Doblin, M.A. & Ralph, P.J. 2012, 'Microbial consortia increase thermal tolerance of corals', Marine Biology, vol. 159, pp. 1763-1771.
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This study examined the response of a coral holobiont to thermal stress when the bacterial community was treated with antibiotics. Colonies of Pocillopora damicornis were exposed to broad and narrow-spectrum antibiotics targeting coral-associated a and c-Proteobacteria. Corals were gradually heated from the control temperature of 26 to 31 C, and measurements were made of host, zooxanthellar and microbial condition. Antibiotics artificially reduced the abundance and activity of bacteria, but had minimal effect on zooxanthellae photosynthetic efficiency or host tissue protein content. Heated corals without antibiotics showed significant declines in FV/FM, typical of thermal stress. However, heated corals treated with antibiotics showed severe tissue loss in addition to a decline in FV/ FM. This study demonstrated that a disruption to the microbial consortium diminished the resilience of the holobiont. Corals exposed to antibiotics under control temperature did not bleach, suggesting that temperature may be an important factor influencing the activity, diversity and ecological function of the holobiont bacterial community.

Hill, R., Larkum, A., Prasil, O., Kramer, D.M., Szabo, M., Kumar, V. & Ralph, P.J. 2012, 'Light-induced dissociation of antenna complexes in the symbionts of scleractinian corals correlates with sensitivity to coral bleaching', Coral Reefs, vol. 31, pp. 963-975.
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Elevated temperatures in combination with moderate to high irradiance are known to cause bleaching events in scleractinian corals, characterised by damage to photosystem II (PSII). Photoprotective mechanisms of the symbiont can reduce the excitation pressure impinging upon PSII. In the bleaching sensitive species, Acropora millepora and Pocillopora damicornis, high light alone induced photoprotection through the xanthophyll cycle, increased content of the antioxidant carotenoid, ¯-carotene, as well as the dissociation of the light-harvesting chlorophyll complexes. The evidence is compatible with either the membrane-bound chlorophyll a-chlorophyll c 2-peridinin-protein (acpPC) complex or the peripheral peridinin-chlorophyll-protein complex, or both, disconnecting from PSII under high light. The acpPC complex potentially showed a state transition response with redistribution towards photosystem I to reduce PSII over-excitation. This apparent acpPC dissociation/reassociation was promoted by the addition of the xanthophyll cycle inhibitor, dithiothreitol, under high irradiance. Exposure to thermal stress as well as high light promoted xanthophyll de-epoxidation and increased ¯-carotene content, although it did not influence light-harvesting chlorophyll complex (LHC) dissociation, indicating light, rather than temperature, controls LHC dissociation. Photoinhibition was avoided in the bleaching tolerant species, Pavona decussata, suggesting xanthophyll cycling along with LHC dissociation may have been sufficient to prevent photodamage to PSII. Symbionts of P. decussata also displayed the greatest detachment of antenna complexes, while the more thermally sensitive species, Pocillopora damicornis and A. millepora, showed less LHC dissociation, suggesting antenna movement influences bleaching susceptibility.

Hill, R. & Scott, A. 2012, 'The influence of irradiance on the severity of thermal bleaching in sea anemones that host anemonefish', Coral Reefs, vol. 31, no. 1, pp. 273-284.
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Entacmaea quadricolor is a geographically widespread species of sea anemone that forms a three-way symbiosis with anemonefish and Symbiodinium. This species dominates the reef substrata at North Solitary Island, Australia, which is located in a region identified as a climate change hot spot. Their geographic location places these anemones under significant threat from rising ocean temperatures, although their upper thermal limit and risk of bleaching are unknown. To address this knowledge gap, anemones were exposed to one of four temperatures (23, 25, 27, or 29 degrees C) and one of two irradiance treatments (high or low light) over 6 days. At moderate temperatures (27 degrees C, 1 degrees C above summer average), anemone bleaching was characterised by symbiont expulsion, while extreme temperatures (29 degrees C) resulted in an additional loss of photosynthetic pigments from within symbionts, and in some cases, host mortality. Irradiance influenced the susceptibility to thermal stress with high light promoting the bleaching response, along with significant reductions in the effective quantum yield of anemone symbionts. The long-term loss of photosystem II photochemical efficiency within in hospite symbionts was observed during exposure to temperatures exceeding the summer average, indicating photosynthetic damage. The resident Symbiodinium, identified as clade C using 28S rRNA gene sequences, therefore represents the partner within the symbiosis that is likely to be most vulnerable to rising seawater temperatures. Results suggest that E. quadricolor is living within approximately 1 degrees C of the upper thermal maximum at the Solitary Islands, and given the predictions for rising seawater temperature on Australia's east coast, the thermal threshold at which bleaching will occur is expected to be reached and exceeded more frequently in the future.

Sinutok, S., Hill, R., Doblin, M.A., Kuhl, M. & Ralph, P.J. 2012, 'Microenvironmental changes support evidence of photosynthesis and calcification inhibition in Halimeda under ocean acidification and warming', Coral Reefs, vol. 31, pp. 1201-1213.
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The effects of elevated CO 2 and temperature on photosynthesis and calcification of two important calcifying reef algae (Halimedamacroloba and Halimeda cylindracea) were investigated with O 2 microsensors and chlorophyll a fluorometry through a combination of two pCO 2 (400 and 1,200 Áatm) and two temperature treatments (28 and 32 ¦C) equivalent to the present and predicted conditions during the 2100 austral summer. Combined exposure to pCO 2 and elevated temperature impaired calcification and photosynthesis in the two Halimeda species due to changes in the microenvironment around the algal segments and a reduction in physiological performance. There were no significant changes in controls over the 5-week experiment, but there was a 50-70 % decrease in photochemical efficiency (maximum quantum yield), a 70-80 % decrease in O 2 production and a threefold reduction in calcification rate in the elevated CO 2 and high temperature treatment. Calcification in these species is closely coupled with photosynthesis, such that a decrease in photosynthetic efficiency leads to a decrease in calcification. Although pH seems to be the main factor affecting Halimeda species, heat stress also has an impact on their photosystem II photochemical efficiency. There was a strong combined effect of elevated CO 2 and temperature in both species, where exposure to elevated CO 2 or temperature alone decreased photosynthesis and calcification, but exposure to both elevated CO 2 and temperature caused a greater decline in photosynthesis and calcification than in each stress individually. Our study shows that ocean acidification and ocean warming are drivers of calcification and photosynthesis inhibition in Halimeda. Predicted climate change scenarios for 2100 would therefore severely affect the fitness of Halimeda, which can result in a strongly reduced production of carbonate sediments on coral reefs under such changed climate conditions.

Hill, R., Brown, C.M., DeZeeuw, K., Campbell, D.A. & Ralph, P.J. 2011, 'Increased rate of D1 repair in coral symbionts during bleaching is insufficient to counter accelerated photo-inactivation', Limnology and Oceanography, vol. 56, no. 1, pp. 139-146.
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We dissect the primary photo-inactivation and the counteracting metabolic repair rates in fragments of the scleractinian coral, Pocillopora damicornis, subjected to a combined stress of a shift to elevated temperature (from 26 degrees C to 32 degrees C) and increased light (from 200 mu mol photons m(-2) s(-1) to 400 mmol photons m(-2) s(-1)) to induce bleaching. During the bleaching treatment the dinoflagellate symbionts showed a 5.5-fold acceleration in their photosystem II (PSII) repair rate constant, demonstrating that they maintain strong metabolic capacity to clear and replace photo-damaged D1 protein at the elevated temperature and light conditions. Nevertheless, the symbionts concurrently suffered a seven-fold increase in the rate constant for PSII photo-inactivation. This rapid photo-inactivation exceeded the PSII repair capacity, therefore tipping the symbionts, and by implication the symbiosis, into net photo-inhibition. Increased photo-inactivation in hospite, rather than an inhibition of PSII repair, is the principle trigger for net photo-inhibition under bleaching conditions.

Petrou, K., Hill, R., Doblin, M.A., McMinn, A., Johnson, R., Wright, S.W. & Ralph, P.J. 2011, 'Photoprotection of sea-ice microalgal communities from the east Antarctic pack ice', Journal of Phycology, vol. 47, no. 1, pp. 77-86.
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All photosynthetic organisms endeavor to balance energy supply with demand. For sea-ice diatoms, as with all marine photoautotrophs, light is the most important factor for determining growth and carbonfixation rates. Light varies from extremely low to often relatively high irradiances within the sea-ice environment, meaning that sea-ice algae require moderate physiological plasticity that is necessary for rapid light acclimation and photoprotection. This study investigated photoprotective mechanisms employed by bottom Antarctic sea-ice algae in response to relatively high irradiances to understand how they acclimate to the environmental conditions presented during early spring, as the light climate begins to intensify and snow and sea-ice thinning commences.

Sinutok, S., Hill, R., Doblin, M.A., Wuhrer, R. & Ralph, P.J. 2011, 'Warmer more acidic conditions cause decreased productivity and calcification in subtropical coral reef sediment-dwelling calcifiers', Limnology and Oceanography, vol. 56, no. 4, pp. 1200-1212.
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The effects of elevated CO(2) and temperature on photosynthesis and calcification in the calcifying algae Halimeda macroloba and Halimeda cylindracea and the symbiont-bearing benthic foraminifera Marginopora vertebralis were investigated through exposure to a combination of four temperatures (28 degrees C, 30 degrees C, 32 degrees C, and 34 degrees C) and four CO(2) levels (39, 61, 101, and 203 Pa; pH 8.1, 7.9, 7.7, and 7.4, respectively). Elevated CO(2) caused a profound decline in photosynthetic efficiency (F(V) : F(M)), calcification, and growth in all species. After five weeks at 34 degrees C under all CO(2) levels, all species died. Chlorophyll (Chl) a and b concentration in Halimeda spp. significantly decreased in 203 Pa, 32 degrees C and 34 degrees C treatments, but Chl a and Chl c(2) concentration in M. vertebralis was not affected by temperature alone, with significant declines in the 61, 101, and 203 Pa treatments at 28 degrees C. Significant decreases in F(V) : F(M) in all species were found after 5 weeks of exposure to elevated CO(2) (203 Pa in all temperature treatments) and temperature (32 degrees C and 34 degrees C in all pH treatments). The rate of oxygen production declined at 61, 101, and 203 Pa in all temperature treatments for all species. The elevated CO(2) and temperature treatments greatly reduced calcification (growth and crystal size) in M. vertebralis and, to a lesser extent, in Halimeda spp. These findings indicate that 32 degrees C and 101 Pa CO(2), are the upper limits for survival of these species on Heron Island reef, and we conclude that these species will be highly vulnerable to the predicted future climate change scenarios of elevated temperature and ocean acidification.

Petrou, K., Hill, R., Brown, C.M., Campbell, D.A., Doblin, M.A. & Ralph, P.J. 2010, 'Rapid photoprotection in sea-ice diatoms from the East Antarctic pack ice', Limnology and Oceanography, vol. 55, no. 3, pp. 1400-1407.
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Photoinhibition and D1 protein re-synthesis were investigated in bottom-dwelling sea-ice microalgal communities from the East Antarctic pack ice during early spring. Bottom-dwelling sea-ice microalgal communities were dominated by diatoms that exhibited rapid photoprotection when exposed to a range of different light levels (10 Ámol photons m-2 s-1, 50 Ámol photons m-2 s-1, 100 Ámol photons m-2 s-1, and 200 Ámol photons m-2 s-1). Photosynthetic capacity of photosystem II (PSII) dropped significantly over 3 h under 200 Ámol photons m-2 s-1, but largely recovered when placed in a low-light environment (10 Ámol photons m-2 s-1) for an additional 3 h. PSII repair rates increased with increasing irradiance, and the D1-protein pool remained steady even under high light (200 Ámol photons m-2 s-1). Sea-ice diatoms showed a low intrinsic susceptibility to photoinactivation of PSII across all the light treatments, and a strong and irradiance-dependent induction of nonphotochemical quenching, which did not depend upon chloroplast protein synthesis, was also seen. These highly plastic organisms, once thought to be adapted to shade, are in fact well equipped to withstand rapid and relatively large changes in light at low temperatures with minimal long-term effect on their photosynthetic machinery.

Wicks, L.C., Hill, R. & Davy, S.K. 2010, 'The influence of irradiance on tolerance to high and low temperature stress exhibited by Symbiodinium in the coral, Pocillopora damicornis, from the high-latitude reef of Lord Howe Island', Limnology and Oceanography, vol. 55, no. 6, pp. 2476-2486.
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The coral Pocillopora damicornis hosts genetically distinct and novel types of dinoflagellate symbionts at the high-latitude site of Lord Howe Island (LHI), yet why these novel types exist at this marginal site is unknown. In this study, it was detennined whether one of the novel Symbiodinium types at LHI is phy~iologically adapted for this high-latitude site, where water temperatures annually range from 18¦C to 26¦e. Low and high short-tenn thennal bleaching thresholds of the coral-symbiont partnership were measured as 14¦C and 30¦e. PhotochEmical sensitivity to temperature (15¦C and 29¦C) and light treatments (100% and 40% of sunlight), measured as effective_ quantum yie1d and fast induction curves, were detennined over a 72-h period. A greater effect on the photochemical reactions of LHI P. damicornis symbionts was recorded in response to a 3¦e temperature increase from annual maxima than a 3¦e temperature decrease from annual minima. Corals did not bleach when temperature was reduced to 15¦e for 72 h; in contrast, a 92% decline in photochemical efficiency was recorded in the 29¦C treatment (AF: F~ < 0.05), compared to 35% loss in the control (20¦C). For the first time, a Pulse Efficiency Analyser fluorometer was used to assess the effect of reduced temperature on symbionts, showing a reduced rate of QA reduction, further enhanced by high light levels. This type of Symbiodinium at LHI may be specialized for cooler and more variable temperatures, so contributing to the success of corals at this marginal location.

Hill, R., Ulstrup, K. & Ralph, P.J. 2009, 'Temperature Induced Changes In Thylakoid Membrane Thermostability Of Cultured, Freshly Isolated, And Expelled Zooxanthellae From Scleractinian Corals', Bulletin of Marine Science, vol. 85, no. 3, pp. 223-244.
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Coral bleaching events are characterized by a dysfunction between the cnidarian coral host and the symbiotic dinoflagellate algae, known as zooxanthellae (genus Symbiodinium). Elevated temperature and intense light induce coral bleaching, where zooxanthellae are expelled from the host tissue. The primary cellular process in zooxanthellae which leads to coral bleaching is unresolved, and here, we investigated the sensitivity of the thylakoid membrane in a Symbiodinium culture and in genetically identified freshly isolated and expelled Symbiodinium cells. The fluorescence-temperature curve technique was used to measure the critical temperature (Tc) at which irreversible damage to the thylakoid membrane occurred. The accuracy of this technique was confirmed through the collection of scanning transmission electron micrographs which demonstrated the clear relationship between Tc and thylakoid membrane degradation. Analysis of 10 coral species with a diverse range of genetically distinct Symbiodinium communities showed a decline in Tc from summer to winter. A Symbiodinium culture and fragments of Pocillopora damicornis (Linnaeus, 1758) were exposed to a series of light and temperature treatments, where Tc increased from approximately 37 -¦C to 42 -¦C upon exposure to elevated temperature. Under bleaching conditions, the thermostability of the thylakoid membrane increased within 4 hrs by 5.1 -¦C, to a temperature far above bleaching thresholds, in both freshly isolated and photosynthetically competent zooxanthellae expelled from P. damicornis under these conditions. It is demonstrated that the thermostability of the thylakoid membrane increases in cultured, freshly isolated, and expelled zooxanthellae exposed to bleaching stress, suggesting it is not the primary site of impact during coral bleaching events.

Hill, R. & Ralph, P.J. 2008, 'Dark-induced reduction of the plastoquinone pool in zooxanthellae of scleractinian corals and implications for measurements of chlorophyll a fluorescence', Symbiosis, vol. 46, pp. 45-56.
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Fluorometric measurements of maximum quantum yield (Fv/Fm) and fast induction curves (FICs) require coral samples to be dark-adapted (DA). Pathways causing dark-reduction of the plastoquinone (PQ) pool are shown here to be active in corals. Early morning sunlight and far-red light successfully increased Fv/Fm and lowered the O and J steps of FICs in corals that were darkened overnight. The thick-tissued massive coral, Cyphastrea serailia, was shown to be more prone to reduction of the PQ pool, with significant reductions in Fv/Fm occurring after 10 min of DA, and elevated J steps occurring within 200 s following a far-red flash. In thinner-tissued branching species, Pocillopora damicornis and Acropora nobilis, elevation of the J step also occurred within 200 s of DA, but a drop in Fv/Fm was only manifested after 30 min. Pre-exposure to far-red light is an effective and simple procedure to ensure determination of the true maximum quantum yield of Photosystem II (PSII) and accurate FICs which require a fully oxidised inter-system electron transport chain and open PSII reaction centres.

Hill, R. & Ralph, P.J. 2008, 'Impact of bleaching stress on the function of the oxygen evolving complex of zooxanthellae from scleractinian corals', Journal of Phycology, vol. 44, no. 2, pp. 299-310.
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Global climate change is leading to the rise of ocean temperatures and is triggering mass coral bleaching events on reefs around the world. The expulsion of the symbiotic dinoflagellate algae is believed to occur as a result of damage to the photosynthetic apparatus of these symbionts, although the specific site of initial impact is yet to be conclusively resolved. Here, the sensitivity of the oxygen evolving complex (OEC) to bleaching stress was studied as well as its natural variation between seasons. The artificial electron donor, diphenyl carbazide (DPC), was added to cultured, freshly isolated and expelled (bleaching treatments only) zooxanthellae suspensions. Chl a fluorescence and oxygen production measurements showed that upon addition of DPC, no restoration of diminished photochemical efficiency occurred under control or bleaching conditions. This result was consistent between 12h and 5d bleaching treatments on Pocilloporadamicornis, indicating that the OEC is not the primary site of damage, and that zooxanthellae expulsion from the host is a nonselective process with respect to the functioning of the OEC. Further experiments measuring fast induction curves (FICs) revealed that in both summer and winter, the temperature when OEC function was lost occurred between 7¦C and 14¦C above the sea surface temperature. FIC and oxygen production measurements of P. damicornis during exposure to bleaching stress demonstrated that the thermotolerance of the OEC increased above the temperature of the bleaching treatment over a 4h period. This finding indicates that the OEC has the capacity to acclimate between seasons and remains functional at temperatures well above bleaching thresholds.

Ulstrup, K.E., Hill, R., van Oppen, M.J., Larkum, A. & Ralph, P.J. 2008, 'Seasonal variation in the photo-physiology of homogeneous and heterogeneous Symbiodinium consortia in two scleractinian corals', Marine Ecology Progress Series, vol. 361, pp. 139-150.
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Seasonal variation in the composition of the algal endosymbiont community and photophysiology was determined in the corals Pocillopora damicornis,w hich show high local fidelity to one symbiont type (Symbiodinium C1) and Acropora valida, with a mixed Symbiodinium synbiont community, compromising members of both clades A and C. The relative abundances of Symbiodinium types varied overtime. A significant decline in symbiont densities in both coral species during the summer of 2005 coincided with a NOAA 'hotspot' warning for Heron Island. This also coincided with a relayiove increase in the presence and dominance of clade A in A. valida particularl in sun-adapted surfaces.

Hill, R. & Ralph, P.J. 2007, 'Post-bleaching viability of expelled zooxanthellae from the scleractinian coral Pocillopora damicornis', Marine Ecology Progress Series, vol. 352, pp. 137-144.
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Coral bleaching events have been linked to elevated seawater temperatures in combination with intense light and can be characterised by the loss of symbionts (zooxanthellae, genus Symbiodinium) from the host tissue, as well as a reduction in photosynthetic pigments in these zooxanthellae. The long-term (days) viability of expelled zooxanthellae in the water column from the scleractiman coral Pocillopora damicornis was explored in this study through measurements of photosynthetic health and morphological condition. After initial expulsion, zooxanthellae were found to be photosynthetically competent and structurally intact. However, within 6 to 12 h following this time, photosystem II photochemical efficiency dramatically declined in these cells and photosynthetic damage was gradually manifested in the loss of structural integrity of the cell. The time of expulsion during bleaching exposure, as well as ambient water temperature, greatly influenced survivorship. Expelled zooxanthellae were collected at 4 different time intervals (0-6, 6-12, 12-24 and 24-36 h) following the onset of exposure to bleaching conditions (32 degrees C and 400 mu mol photons m(-2) s(-1)) and then maintained at 28, 30 or 32 degrees C and 100 mu mol photons m(-2) s(-1) for up to 96 h. Those cells expelled within the first 6 h of bleaching and held at 28 degrees C (lagoon temperature) had the greatest longevity, although even in this treatment, long-term photosynthetic viability was restricted to 5 d in the water column. This suggests that unless expelled zooxanthellae inhabit other environments of coral reefs (such as sediments) which may be more favourable for survival, their capacity for persistence in the environment is extremely limited.

Scanes, P., Coade, G., Doherty, M. & Hill, R. 2007, 'Evaluation of the utility of water quality based indicators of estuarine condition in NSW, Australia', Estuarine, Coastal And Shelf Science, vol. 74, no. 1-2, pp. 306-319.
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Environmental indicators must have a predictable relationship with stressors to be of value in ecological assessments. We evaluated the information provided by commonly implemented monitoring indictaors as a means of assessing of the level of ecological impact experienced by coastal lagoons in NSW, Australia. Existing data for environemtal variables in coastal lagoons were correlated with independent estimates of catchment disturbance.

Hill, R. & Ralph, P.J. 2006, 'Photosystem II Heterogeneity of in hospite Zooxanthellae in Scleractinian Corals Exposed to Bleaching Conditions', Photochemistry and Photobiology, vol. 82, no. 6, pp. 1577-1585.
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Increased ocean temperatures are thought to be triggering mass coral bleaching events around the world. The intracellular symbiotic zooxanthellae (genus Symbiodinium) are expelled from the coral host, which is believed to be a response to photosynthetic damage within these symbionts. Several sites of impact have been proposed, and here we probe the functional heterogeneity of Photosystem II (PSII) in three coral species exposed to bleaching conditions. As length of exposure to bleaching conditions (32 degrees C and 350 mu mol photons m(-2) s(-1)) increased, the Q(A)(-) reoxidation kinetics showed a rise in the proportion of inactive PSII centers (PSIIX), where Q(B) was unable to accept electrons. PSIIX contributed up to 20% of the total PSII centers in Pocillopora damicornis, 35% in Acropora nobilis and 14% in Cyphastrea serailia. Changes in F-V/F-M and amplitude of the J step along fast induction curves were found to be highly dependent upon the proportion of PSIIx centers within the total pool of PSII reaction centers. Determination of PSII antenna size revealed that under control conditions in the three coral species up to 60% of PSII centers were lacking peripheral light-harvesting complexes (PSII beta). In P. damicornis, the proportion of PSII beta increased under bleaching conditions and this could be a photoprotective mechanism in response to excess light. The rapid increases in PSIIX and PSII beta observed in these corals under bleaching conditions indicates these physiological processes are involved in the initial photochemical damage to zooxanthellae.

Hill, R. & Ralph, P.J. 2005, 'Diel and seasonal changes in fluorescence rise kinetics of three scleractinian corals', Functional Plant Biology, vol. 32, no. 6, pp. 549-559.
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The effect of diel oscillations in light on the photosynthetic response of three coral species during summer and winter was studied. Fast induction curves revealed detailed information on primary photochemistry as well as redox states of electron accepto

Hill, R., Frankart, C. & Ralph, P.J. 2005, 'Impact of bleaching conditions on the components of non-photochemical quenching in the zooxanthellae of a coral', Journal Of Experimental Marine Biology And Ecology, vol. 322, no. 1, pp. 83-92.
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Mass coral bleaching events are a worldwide phenomenon, which generally occur during periods of elevated sea surface temperature and intense sunlight. These conditions result in a decline in photochemical efficiency of symbiotic microalgae (zooxanthellae

Ulstrup, K.E., Hill, R. & Ralph, P.J. 2005, 'Photosynthetic impact of hypoxia on in hospite zooxanthellae in the scleractinian coral Pocillopora damicornis', Marine Ecology-Progress Series, vol. 286, pp. 125-132.
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Shallow water coral reefs may experience hypoxia under conditions of calm weather doldrums. Anaerobic responses of endosymbionts (i.e. zooxanthellae) within Pocillopora damicornis coral colonies were tested using both slow and fast chlorophyll a fluoresc

Hill, R., Larkum, A., Frankart, C., Kuehl, M. & Ralph, P.J. 2004, 'Loss of functional Photosystem II reaction centres in zooxanthellae of corals exposed to bleaching conditions: using fluorescence rise kinetics', Photosynthesis Research, vol. 82, pp. 59-72.
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Hill, R., Schreiber, U., Gademann, R., Larkum, A., Kuehl, M. & Ralph, P.J. 2004, 'Spatial heterogeneity of photosynthesis and the effect of temperature-induced bleaching condition in three species of corals', Marine Biology, vol. 144, pp. 633-640.
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Major, R., Pyke, G., Christy, M., Gowing, G., Hill, R. 1994, 'Can Nest Predation Explain The Timing Of The Breeding-Season And The Pattern Of Nest Dispersion Of New-Holland Honeyeaters', OIKOS, vol. 69, no. 3, pp. 364-372.
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We tested the following two predictions of the hypotheses that predation rate may select for nest spacing and winter breeding in New Holland honeyeaters: (a) the level of nest predation should be lower during the breeding season than outside it, and (b)