Massive Porites Colonies Research Articles

Coexistence of nonfluorescent chromoproteins and fluorescent proteins in massive Porites spp. corals manifesting a pink pigmentation response.

Several fluorescent proteins (FPs) and chromoproteins (CPs) are present in anthozoans and play possible roles in photoprotection. Coral tissues in massive corals often display discoloration accompanied by inflammation. Incidences of the pink pigmentation response (PPR) in massive Porites, described as inflammatory pink lesions of different shapes and sizes, has recently increased worldwide. FPs are reported to be present in PPR lesions, wherein a red fluorescent protein (RFP) appears to play a role in reducing reactive oxygen species. However, to date, the biochemical characterization and possible roles of the pigments involved are poorly understood. The present study aimed to identify and characterize the proteins responsible for pink discoloration in massive Porites colonies displaying PPRs, as well as to assess the differential distribution of pigments and the antioxidant properties of pigmented areas. CPs were extracted from PPR lesions using gel-filtration chromatography and identified via genetic analysis using liquid chromatography-tandem mass spectrometry. The coexistence of CPs and RFP in coral tissues was assessed using microscopic observation. Photosynthetic antivity and hydrogen peroxide-scavenging activitiy were measured to assess coral stress conditions. The present study revealed that the same CP (plut2.m8.16902.m1) isolated from massive Porites was present in both the pink spot and patch morphologies of the PPR. CPs were also found to coexist with RFP in coral tissues that manifested a PPR, with a differential distribution (coenosarc or tip of polyps' tentacles). High hydrogen peroxide-scavenging rates were found in tissues affected by PPR. The coexistence of CPs and RFP suggests their possible differential role in coral immunity. CPs, which are specifically expressed in PPR lesions, may serve as an antioxidant in the affected coral tissue. Overall, this study provides new knowledge to our understanding of the role of CPs in coral immunity.

Deoxygenation following coral spawning and low-level thermal stress trigger mass coral mortality at Coral Bay, Ningaloo Reef

Oxygen depletion is well recognized for its role in the degradation of tropical coral reefs. Extreme acute hypoxic events that lead to localized mass mortality and the formation of ‘dead zones’ (a region where few or no organisms can survive due to a lack of oxygen) are particularly concerning as they can result in wide-ranging losses of biodiversity, ecosystem productivity and functioning, economic prosperity, and wellbeing. In March of 2022, the annual coral spawning event at Bills Bay (Coral Bay, Ningaloo Reef, Western Australia) coincided with elevated seawater temperature, calm weather conditions and a flood tide resulting in coral spawn becoming trapped in Bills Bay. Immediately after, there was a mass fish kill, which is believed to have been caused by local eutrophication resulting in severe oxygen depletion. The impact the deoxygenation and thermal stress event had on benthic communities has not yet been quantified; hence, the principal aim of this study is to document the extent of change that occurred in the benthic communities before and after the 2022 coral spawning event over a spatial gradient from the nearshore to mid-reef. Percent coral cover in the Bay decreased from 55.62 ± 2.26% in 2016–2018 and 70.44 ± 5.24% in 2021 to 1.16 ± 0.51% in 2022. Over the same period, the percent cover of turf algae increased from 27.40 ± 2.00% in 2016–2018 and 24.66 ± 6.67% in 2021 to 78.80 ± 3.06% in 2022, indicating a dramatic phase shift occurred at Bills Bay. The abundance of healthy coral colonies recorded on replicated belt transects at nine sites declined from 3452 healthy individuals in 2018 to 153 individuals in 2022 and coral generic richness decreased by 84.61%, dropping from 26 genera in 2018 to 4 genera in 2022. Previously dominant genera such as Acropora,Montipora and Echinopora, were extirpated from survey sites. Isolated colonies of massive Porites spp. and encrusting Cyphastrea sp. survived the event and understanding the mechanisms underpinning their greater survivorship is an important area of future research. Long-term monitoring is recommended to track the community recovery process and improve our understanding of the longer-term implications of this acute mortality event on the ecological, socio-economic and cultural values of Ningaloo Reef.

Hot spots of bleaching in massive Porites coral colonies

Coral bleaching events have become more frequent and severe due to ocean warming. While the large-scale impacts of bleaching events are well-known, there is growing recognition of the importance of small-scale spatial variation in bleaching and survival probability of individual coral colonies. By quantifying bleaching in 108 massive Porites colonies spread across Lizard Island, Great Barrier Reef, during the 2016 bleaching event, we investigated how hydrodynamic exposure levels and colony size contribute to local variability in bleaching prevalence and extent. Our results revealed that exposed locations were the least impacted by bleaching, while lagoonal areas exhibited the highest prevalence of bleaching and colony-level bleaching extents. Such patterns of bleaching could be due to prolonged exposure to warm water in the lagoon. These findings highlight the importance of considering location-specific factors when assessing coral health and emphasize the vulnerability of corals in lagoonal habitats to rapid and/or prolonged elevated temperatures.

Corallivory on small Porites colonies increases with coral colony size but is reduced by macroalgal associational refuge

Numerous tropical macroalgae provide associational refuge to other benthic organisms, presumably due to their physical structure and/or production of chemical metabolites. One feature determining their effectiveness as an associational refuge is likely to be the size of the organism benefitting from the refuge. Using a manipulative experiment in the back reef of Moorea, French Polynesia, we tested if the macroalga Turbinaria ornata provided an associational refuge from fish corallivores for small colonies of massive Porites spp., and how this differed with colony size (20–100 mm diameter). Tissue loss through corallivory increased with colony size but was ~ 72% less for Porites colonies associated with T. ornata versus colonies separated from this macroalga, while dense macroalgae beds on contemporary reefs negatively impact the recruitment, growth and survival of corals, small colonies of Porites appear to benefit, through reduced corallivory, by associating with the macroalga Turbinaria. This association may come at a cost (e.g., reduced growth) and should be the focus of future research.

Compounded effects of sea urchin grazing and physical disturbance on macroalgal canopies in the lagoon of Moorea, French Polynesia

Release from herbivory is a factor underpinning coral replacement by macroalgae. Once macroalgae have achieved dominance, shifts back to the coral-dominated state can be hindered by stabilizing feedbacks. Thus, restoring herbivore assemblages alone can be insufficient to trigger coral recovery. However, herbivores could control macroalgal recovery in the aftermath of physical disturbances removing macroalgae. Diadematid urchins at Moorea (French Polynesia) have collapsed in the last decade. By means of a manipulative field experiment, we tested the interactive effects of physical disturbance and increased diadematid densities on macroalgae inside the lagoon. Massive Porites colonies, referred to as ‘bommies’, were assigned to 3 different macroalgal removal treatments (removal of stipes and fronds of the canopy-forming macroalgae Turbinaria ornata and Sargassum pacificum, total removal of erect macroalgae or untouched) and exposed to 3 different urchin densities (absent, low [~0.5 ind. m-2], and intermediate [~1 ind. m-2]). After 1 yr, sea urchins had no effect on the covers of S. pacificum and T. ornata when macroalgal canopies were left untouched. Urchins could control the recovery of S. pacificum on total macroalgal removal bommies, but not that of T. ornata. However, urchins, even when at intermediate densities, did not generate major changes in the structure of benthic assemblages on experimental bommies. Our study indicates that a moderate increase in diadematid densities is unlikely to reduce the extent of macroalgal stands in Moorea back reefs unless associated with the recovery of other herbivore guilds able to remove adult macroalgae (i.e. browsers).

Reef accumulation is decoupled from recent degradation in the central and southern Red Sea

Reefs are biogenic structures that result in three-dimensional accumulations of calcium carbonate. Over geological timescales, a positive balance between the production and accumulation of calcium carbonate versus erosional and off-reef transport processes maintains positive net accretion on reefs. Yet, how ecological processes occurring over decadal timescales translate to the accumulation of geological structures is poorly understood, in part due to a lack of studies with detailed time-constrained chronologies of reef accretion over decades to centuries. Here, we combined ecological surveys of living reefs with palaeoecological reconstructions and high-precision radiometric (U-Th) age-dating of fossil reefs represented in both reef sediment cores and surficial dead in situ corals, to reconstruct the history of community composition and carbonate accumulation across the central and southern Saudi Arabian Red Sea throughout the late Holocene. We found that reefs were primarily comprised of thermally tolerant massive Porites colonies, creating a consolidated coral framework, with unconsolidated branching coral rubble accumulating among massive corals on shallow (5–8 m depth) exposed (windward), and gently sloping reef slopes. These unconsolidated reef rubble fields were formed primarily from ex situ Acropora and Pocillopora coral fragments, infilled post deposition within a sedimentary matrix. Bayesian age-depth models revealed a process of punctuated deposition of post-mortem coral fragments transported from adjacent reef environments. That a large portion of Saudi Arabian Red Sea reef slopes is driven by allochthonous deposition (transportation) has important implications for modeling carbonate budgets and reef growth. In addition, a multi-decadal lag exists between the time of death for branching in situ coral and incorporation into the unconsolidated reef rubble. This indicates that recent climate related degradation in the 21st century has not had an immediately negative effect on reef building processes affecting a large portion of the reef area in the Saudi Arabian Red Sea.

Dangerous demographics in post-bleach corals reveal boom-bust versus protracted declines

Thermal-stress events have changed the structure, biodiversity, and functioning of coral reefs. But how these disturbances affect the dynamics of individual coral colonies remains unclear. By tracking the fate of 1069 individual Acropora and massive Porites coral colonies for up to 5 years, spanning three bleaching events, we reveal striking genus-level differences in their demographic response to bleaching (mortality, growth, and recruitment). Although Acropora colonies were locally extirpated, substantial local recruitment and fast growth revealed a marked capacity for apparent recovery. By contrast, almost all massive Porites colonies survived and the majority grew in area; yet no new colonies were detected over the 5 years. Our results highlight contrasting dynamics of boom-and-bust vs. protracted declines in two major coral groups. These dangerous demographics emphasise the need for caution when documenting the susceptibility and perceived resistance or recovery of corals to disturbances.

Complex interactions with nutrients and sediment alter the effects of predation on a reef‐building coral

AbstractFramework‐building corals create the three‐dimensional structure of coral reefs and are subject to predation from fishes, echinoderms, and gastropods. Anthropogenic stressors can magnify the effects of such top‐down pressure on foundation species. The gastropodCoralliophilaviolacea(Kiener, 1836) depletes coral energy reserves via predation, potentially increasing coral susceptibility to land‐based pollution (i.e., sediment accumulation and nutrient pollution). We hypothesized that sedimentation would worsen coral mortality, while nutrient enrichment would mitigate the harmful effects of sediment and predation on coral mortality by increasing the densities of algal symbionts. To test these hypotheses, we conducted in situ surveys of the fringing reefs in Mo'orea, French Polynesia to explore the relationships among massivePoritesspp. cover,C. violaceadensities, and sediment accumulation on coral colonies across low and high nutrient sites. We also conducted a factorial field experiment to test the interactions among these stressors on coral tissue mortality, symbiont densities, and chlorophyll. MassivePoritescolonies at higher nutrient sites hadC. violaceadensities 13 times higher than at low nutrient sites but there was no difference in the amount of live tissue on coral colonies with or without snails among these sites. In our experiment, there were interactions between predation and nutrients as well as nutrients and sediment that impacted coral mortality. Sedimentation and predation byC. violaceaincreased coral tissue mortality independently by ~20%. Nutrient enrichment reduced this effect in corals under sedimentation or predation pressure by lowering coral tissue mortality by 18% and increasing algal symbiont densities by ~28%. Our results indicate that sediment does not magnify top‐down pressure on this coral, and that moderate nutrient enrichment may interact with predation in complex, unexpected ways to alter the responses of corals to top‐down pressure.

Herbivorous damselfishes expand their territories after causing white scars on Porites corals

Turf algae become the most abundant benthic group on coral reefs after mass coral bleaching. By defending feeding territories, damselfishes enhance the growth of turf algae in so-called algal farms and affect coral communities both directly and indirectly. We found several white scars (i.e., bite lesions) on massive Porites colonies around feeding territories. In this study, we examined the occurrence of white scars on corals and their function in coral–algal competition at the boundaries between algal farms of two damselfish species—the intensive farmer Stegastes nigricans, and the intermediate farmer S. lividus—and adjacent Porites corals for 3 years around Okinawa Island, Japan. White scars occurred on Porites colonies only adjacent to the territories of both damselfish species. Of the white scars on corals around S. nigricans territories, 73% of the area was covered by algae within 2 weeks, while the remaining was re-covered by Porites tissues. The coral–algal boundaries encroached further into areas of coral when the area of white scars were larger. These results suggest that both intensive and intermediate farmers bite adjacent Porites colonies causing white scars on corals, and expand their territories onto corals using algae-covered white scars as stepping stones.

Macroborer presence on corals increases with nutrient input and promotes parrotfish bioerosion

Bioerosion by reef-dwelling organisms influences net carbonate budgets on reefs worldwide. External bioeroders, such as parrotfish and sea urchins, and internal bioeroders, including sponges and lithophagid bivalves, are major contributors to bioerosion on reefs. Despite their importance, few studies have examined how environmental (e.g., nutrients) or biological drivers (e.g., the actions of other bioeroders) may influence bioeroder dynamics on reefs. For example, internal bioeroders could promote external bioerosion by weakening the coral skeletal matrix. Our study investigated: (1) whether nutrient supply influences the dynamics between internal and external bioeroders and (2) how the presence of a boring bivalve, Lithophaga spp., influences parrotfish bioerosion on massive Porites corals. We hypothesized that nutrient supply would be positively correlated with Lithophaga densities on massive Porites colonies, and that as bivalve density increased, the frequency and intensity of parrotfish bioerosion would increase. To test these hypotheses, we analyzed six time points over a 10-yr period from a time series of benthic images and nitrogen content of a dominant macroalga from the fringing reefs around Moorea, French Polynesia. We found Lithophaga densities were positively correlated with nitrogen availability. Further, massive Porites that are more infested with Lithophaga had both a higher probability of being bitten by parrotfish and a higher density of bite scars from parrotfishes. Our findings indicate that increasing nutrient availability may strengthen the relationship between internal and external bioeroders, suggesting that colonies at more eutrophic sites may experience higher bioerosion rates.

Morphology, lipid composition, and reproduction in growth anomalies of the reef-building coral Porites evermanni and Porites lobata

Growth anomalies (GAs) are protuberant masses found on many coral species; their presence may be linked to increased ocean temperatures and bleaching stress. In 2014 and 2015, Hawai‘i experienced back-to-back beaching events, after which an increased number of growth anomalies were noted on massive Porites colonies. GAs and normal tissues were sampled from 19 P. evermanni and P. lobata colonies in 2015 and from each of 15 separate P. evermanni colonies on six dates from June 2016 to August 2017, encompassing two annual reproductive cycles. Compared to normal tissue, GAs had significantly larger corallites in all dimensions in both P. evermanni and P. lobata. GAs of P. evermanni also had reduced amounts of lipid and lower functional lipid ratios across all time points. Across tissue types, lipid content was generally higher in winter (December) and spring (April) than in summer months (June/July), but was not correlated with reproductive condition. While GAs are generally non-reproductive in other corals, GA tissues in P. evermanni contained elevated numbers of oocytes in 2017. Compared to normal tissue, GAs in P. evermanni had aberrant corallite morphology and likely committed proportionally more energy to growth and less to energy storage.

Algae dictate multiple stressor effects on coral microbiomes

Most studies of stressors focus on the response of traditionally classified organisms via effects on growth, mortality or physiology; however, most species have microbial associates that may mediate the response of a host to the stressor. Additionally, species rarely experience one stressor alone, but instead are influenced by multiple, potentially interacting stressors. We evaluated how coral microbiomes responded to two biotic stressors: the vermetid gastropod, Ceraesignum maximum, and algal turfs, both of which have previously been shown to decrease coral growth, survival and photophysiology. We collected coral mucus from massive Porites colonies in the presence versus absence of both algae and vermetids and sequenced the 16S rRNA gene to characterize the coral surface microbial communities. The presence of algae increased the alpha diversity of the coral microbial community, likely by increasing the relative abundance of rare members of the community. Algae also reduced beta diversity, which we hypothesized was due to algae homogenizing the physical environment. In contrast, vermetids had only small effects on microbial communities, even though vermetids have deleterious effects on coral growth. We previously hypothesized that vermetids would exacerbate algal effects on microbes, but we failed to detect an interaction between vermetids and algae on the coral’s microbiome, except for one family, Fusobacteriaceae, which was most abundant in the presence of both stressors. We suggest that algae can affect corals through their effects on microbes, whereas vermetids primarily affect the host directly; these complementary effects may limit the extent to which stressors can interact.

Non-bleached colonies of massive Porites may attract fishes for selective grazing during mass bleaching events.

In this study we investigated the variation in grazing scar densities between bleached and non-bleached colonies of massive Porites species in Sekisei Lagoon (Okinawa, southwestern Japan) during a mass bleaching event in 2016. The grazing scar densities and bleaching susceptibility varied among neighboring colonies of massive Porites spp. However, non-bleached colonies had significantly more surface scars than bleached colonies. One explanation for these variations is that corallivorous fishes may selectively graze on non-bleached, thermally tolerant colonies. This is the first report of a relationship between grazing scars and the bleaching status of massive Porites spp. colonies during a mass bleaching event.

The effects of ocean acidification on wound repair in the coral Porites spp.

Scleractinian corals on tropical reefs are exposed to many natural and anthropogenic disturbances, and while much is known about their responses to such conditions, it is unclear whether the responses will remain the same in a future affected by climate change and ocean acidification. To evaluate how one aspect of these effects — wound repair — might be influenced by ocean acidification, small colonies of massive Porites spp. from the back reef of Moorea, French Polynesia, were damaged to simulate the effects of single bites by corallivorous fishes, and healing was measured under contrasting PCO2 regimes. Using experiments lasting 19–20d and employing superficial (2013) or deep (2014) lesions, the effects of damage were evaluated at ~400μatm (ambient) and ~1000μatm PCO2 (both at ~28.5°C) using calcification and healing as dependent variables. Damage reduced calcification of massive Porites spp. in 2013, but not in 2014, and PCO2 had no effect on area-normalized calcification or healing in both years, although biomass-normalized calcification was reduced by high PCO2 in 2014. Overall these results reveal the physiological resilience of this functional group of corals to the extent of ocean acidification expected by the end of this century, and suggest that over this period small colonies will remain capable of recovery from minor damage arising from fish corallivory.

Acropora interbranch skeleton Sr/Ca ratios: Evaluation of a potential new high‐resolution paleothermometer

The majority of coral geochemistry-based paleoclimate reconstructions in the Indo-Pacific are conducted on selectively cored colonies of massive Porites. This restriction to a single genus may make it difficult to amass the required paleoclimate data for studies that require deep reef coring techniques. Acropora, however, is a highly abundant coral genus in both modern and fossil reef systems and displays potential as a novel climate archive. Here we present a calibration study for Sr/Ca ratios recovered from interbranch skeleton in corymbose Acropora colonies from Heron Reef, southern Great Barrier Reef. Significant intercolony differences in absolute Sr/Ca ratios were normalized by producing anomaly plots of both coral geochemistry and instrumental water temperature records. Weighted linear regression of these anomalies from the lagoon and fore-reef slope provide a sensitivity of −0.05 mmol/mol °C−1, with a correlation coefficient (r2 = 0.65) comparable to those of genera currently used in paleoclimate reconstructions. Reconstructions of lagoon and reef slope mean seasonality in water temperature accurately identify the greater seasonal amplitude observed in the lagoon of Heron Reef. A longer calibration period is, however, required for reliable reconstructions of annual mean water temperatures.

Comparison of equatorial Pacific sea surface temperature variability and trends with Sr/Ca records from multiple corals

AbstractCoral Sr/Ca is widely used to reconstruct past ocean temperatures. However, some studies report different Sr/Ca‐temperature relationships for conspecifics on the same reef, with profound implications for interpretation of reconstructed temperatures. We assess whether these differences are attributable to small‐scale oceanographic variability or “vital effects” associated with coral calcification and quantify the effect of intercolony differences on temperature estimates and uncertainties. Sr/Ca records from four massive Porites colonies growing on the east and west sides of Jarvis Island, central equatorial Pacific, were compared with in situ logger temperatures spanning 2002–2012. In general, Sr/Ca captured the occurrence of interannual sea surface temperature events but their amplitude was not consistently recorded by any of the corals. No long‐term trend was identified in the instrumental data, yet Sr/Ca of one coral implied a statistically significant cooling trend while that of its neighbor implied a warming trend. Slopes of Sr/Ca‐temperature regressions from the four different colonies were within error, but offsets in mean Sr/Ca rendered the regressions statistically distinct. Assuming that these relationships represent the full range of Sr/Ca‐temperature calibrations in Jarvis Porites, we assessed how well Sr/Ca of a nonliving coral with an unknown Sr/Ca‐temperature relationship can constrain past temperatures. Our results indicate that standard error of prediction methods underestimate the actual error as we could not reliably reconstruct the amplitude or frequency of El Niño–Southern Oscillation events as large as ± 2°C. Our results underscore the importance of characterizing the full range of temperature‐Sr/Ca relationships at each study site to estimate true error.

Structure and palaeoenvironmental implications of inter-branch coenosteum-rich skeleton in corymbose Acropora species

Coral reefs provide an increasingly important archive of palaeoclimate data that can be used to constrain climate model simulations. Reconstructing past environmental conditions may also provide insights into the potential of reef systems to survive changes in the Earth’s climate. Reef-based palaeoclimate reconstructions are predominately derived from colonies of massive Porites, with the most abundant genus in the Indo-Pacific—Acropora—receiving little attention owing to their branching growth trajectories, high extension rates and secondary skeletal thickening. However, inter-branch skeleton (consisting of both coenosteum and corallites) near the bases of corymbose Acropora colonies holds significant potential as a climate archive. This region of Acropora skeleton is atypical, having simple growth trajectories with parallel corallites, approximately horizontal density banding, low apparent extension rates and a simple microstructure with limited secondary thickening. Hence, inter-branch skeleton in Acropora bears more similarities to the coralla of massive corals, such as Porites, than to traditional Acropora branches. Cyclic patterns of Sr/Ca ratios in this structure suggest that the observed density banding is annual in nature, thus opening up the potential to use abundant corymbose Acropora for palaeoclimate reconstruction.

Clustered parrotfish feeding scars trigger partial coral mortality of massive Porites colonies on the inshore Great Barrier Reef

Coral predation by parrotfishes can cause damage to coral colonies, but research into the dynamics of their feeding scars on Indo-Pacific corals is limited. We monitored feeding scars of the parrotfish Chlorurus microrhinos on massive Porites colonies at Orpheus Island (inshore Great Barrier Reef) over 4 months. Of the 30 marks monitored, 11 were single feeding scars, which all healed completely. The remaining 19 feeding marks consisted of clusters of scars. Eight began to recover, while 11 increased in size by 1,576 ± 252 % (mean ± SE). A logistic regression predicted that a single feeding scar on a Porites colony had a 97 % probability of healing; however, where more than three feeding scars were present, this dropped below 50 %. As excavating parrotfishes in the Indo-Pacific often take multiple focused bites, they may have a significant impact on the growth and mortality of massive Porites colonies at Orpheus Island.

Effects of simulated fish predation on small colonies of massive Porites spp. and Pocillopora meandrina

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 508:139-148 (2014) - DOI: https://doi.org/10.3354/meps10862 Effects of simulated fish predation on small colonies of massive Porites spp. and Pocillopora meandrina Caitlin M. Cameron1,2,*, Peter J. Edmunds1 1Department of Biology, California State University, 18111 Nordhoff Street, Northridge, California 91330-8303, USA 2Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149, USA *Corresponding author: CCameron516@gmail.com ABSTRACT: The effects of corallivory on small colonies of massive Porites spp. (<5 cm diameter) and Pocillopora meandrina (<7 cm high) were explored in situ on shallow reefs in Moorea, French Polynesia. Experiments were conducted to test the hypothesis that corals respond equally to damage caused by single bites of fishes belonging to 3 functional feeding guilds defined as excavators, scrapers, and browsers, which damage corals in different ways. While recovering from damage, massive Porites spp. grew 24 to 43% faster by weight than P. meandrina, and lesions caused by scraping and browsing healed more rapidly on P. meandrina than on massive Porites spp.; lesions caused by excavation healed more rapidly on massive Porites spp. than on P. meandrina. These results suggest that the effects of fish corallivores differ between coral taxa, with the contrasting effects potentially arising from differences in skeletal structure, corallum morphology, and mode of corallivore feeding. KEY WORDS: Scleractinia · Damage · Recovery · Fish predation · Porites · Pocillopora Full text in pdf format PreviousNextCite this article as: Cameron CM, Edmunds PJ (2014) Effects of simulated fish predation on small colonies of massive Porites spp. and Pocillopora meandrina. Mar Ecol Prog Ser 508:139-148. https://doi.org/10.3354/meps10862 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 508. Online publication date: August 04, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Discerning the timing and cause of historical mortality events in modern Porites from the Great Barrier Reef

The life history strategies of massive Porites corals make them a valuable resource not only as key providers of reef structure, but also as recorders of past environmental change. Yet recent documented evidence of an unprecedented increase in the frequency of mortality in Porites warrants investigation into the history of mortality and associated drivers. To achieve this, both an accurate chronology and an understanding of the life history strategies of Porites are necessary. Sixty-two individual Uranium–Thorium (U–Th) dates from 50 dead massive Porites colonies from the central inshore region of the Great Barrier Reef (GBR) revealed the timing of mortality to have occurred predominantly over two main periods from 1989.2±4.1 to 2001.4±4.1, and from 2006.4±1.8 to 2008.4±2.2 A.D., with a small number of colonies dating earlier. Overall, the peak ages of mortality are significantly correlated with maximum sea-surface temperature anomalies. Despite potential sampling bias, the frequency of mortality increased dramatically post-1980. These observations are similar to the results reported for the Southern South China Sea. High resolution measurements of Sr/Ca and Mg/Ca obtained from a well preserved sample that died in 1994.6±2.3 revealed that the time of death occurred at the peak of sea surface temperatures (SST) during the austral summer. In contrast, Sr/Ca and Mg/Ca analysis in two colonies dated to 2006.9±3.0 and 2008.3±2.0, suggest that both died after the austral winter. An increase in Sr/Ca ratios and the presence of low Mg-calcite cements (as determined by SEM and elemental ratio analysis) in one of the colonies was attributed to stressful conditions that may have persisted for some time prior to mortality. For both colonies, however, the timing of mortality coincides with the 4th and 6th largest flood events reported for the Burdekin River in the past 60years, implying that factors associated with terrestrial runoff may have been responsible for mortality. Our results show that a combination of U–Th and elemental ratio geochemistry can potentially be used to precisely and accurately determine the timing and season of mortality in modern massive Porites corals. For reefs where long-term monitoring data are absent, the ability to reconstruct historical events in coral communities may prove useful to reef managers by providing some baseline knowledge on disturbance history and associated drivers.