Bielmyer-Fraser, G. K., Patel, P., Capo, T., & Grosell, M. (2018). Physiological responses of corals to ocean acidification and copper exposure. Mar Pollut Bull, 133, 781–790.
Abstract: Acidification and land-based sources of pollution have been linked to widespread declines of coral cover in coastal reef ecosystems. In this study, two coral species, Acropora cervicornis and Pocillopora damicornis were exposed to increased copper at two CO2 levels for 96h. Copper accumulation and anti-oxidant enzyme activities were measured. Copper accumulation only increased in A. cervicornis zooxanthellae and corresponded with photosynthetic toxicity. Enzyme activities in both coral species were affected; however, A. cervicornis was more sensitive than P. damicornis, and zooxanthellae were more affected than animal fractions of holobionts. Generally, activities of all anti-oxidant enzymes increased, with copper exposure in corals; whereas, activities of glutathione reductase and to some degree glutathione peroxidase were observed due to increasing CO2 exposure alone. Exposure to copper in combination with higher CO2 resulted in a synergistic response in some cases. These results provide insight into mechanisms of copper and CO2 impacts in corals.
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Brachert, T. C., Reuter, M., Krüger, S., Lohmann, H., Petuch, E. J., & Klaus, J. S. (2014). A 4.2 million years record of interglacial paleoclimate from sclerochronological data of Florida carbonate platform (Early Pliocene to recent). Global and Planetary Change, 120, 54–64.
Abstract: The climate of the Pliocene and early Pleistocene was in a transient mode from generally warmer climates of the early Neogene to the maximum glaciations of the late Quaternary. Increasingly severe coolings occurred episodically in the high latitudes, whereas the low latitudes remained warm. For the last 5 million years (Ma), rather constant sea surface temperatures have been recorded in the Western Atlantic warm pool; however, direct climate data on temperature and humidity from shallow near-shore settings are lacking so far. In this study we present a synthesis of 26 new and 46 (incl. 24 recent) published sclerochronogical stable isotope records (18O/16O, 13C/12C) with a sub-annual resolution from reef corals (z-corals) and mollusks. The fossils were sampled from shallow-water carbonate deposits of the Florida carbonate platform and belong to 12 interglacial time-slices spanning collectively the period from the Early Pliocene to the recent (4.2 to 0 Ma). Although platform carbonates are believed to undergo rapid diagenetic stabilization due to the dissolution of metastable aragonite shells, we show that there is still a wealth of material to be recovered for large-scale systematic geochemical studies. We rule out significant diagenetic modifications of the stable isotope data because measured 18O/16O ratios from z-corals and mollusks converted into temperature give consistent results. Accordingly, annual mean temperatures have risen during the last 4.2 Ma from ~ 23 °C to 26 °C in open waters, given the modern seawater value of 18O/16O is valid for Neogene. However, the global water value has changed due to long-term increases in ice volume even during interglacials, equivalent with a 2.3 °C temperature rise. A net 5.3 °C temperature increase over the last 4.2 Ma is inconsistent with the deep-sea record, however, and suggestive of an overall increase of humidity effects in measured 18O/16O instead. Particularly cool temperatures have been registered at 1.9 and 2.5 Ma, but combined 18O/16O and 13C/12C data identify these as artifacts from intensified evaporation which fits the overall restricted marine aspect of the fossil fauna in these time-slices. Seasonal temperature contrasts seem to have been high within restricted settings (~ 11 °C) and small in mixed open marine units (7–8 °C). Although this finding fits the modern situation with coastal environments undergoing 14 °C seasonal change and the reef tract 7–9 °C only, circumstantial evidence suggests reconstructions to be biased by sub-annual changes in the local seawater value for 18O/16O. Since 18O/16O seasonality has increased over the last 4.2 Ma, we suggest the humidity of modern Florida to have evolved from dryer precursor climates of past interglacials, whereas temperatures in essence remained the same. This trend possibly represents the expression of the growing relevance of the Bermudas High pressure cell. Glacial climates of Florida cannot be reconstructed using our methodology as the Florida platform was emergent during sea level lowstands.
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Cacciapaglia, C., & van Woesik, R. (2015). Reef-coral refugia in a rapidly changing ocean. Glob Change Biol, .
Abstract: This study sought to identify climate-change thermal-stress refugia for reef corals in the Indian and Pacific Oceans. A species distribution modeling approach was used to identify refugia for 12 coral species that differed considerably in their local response to thermal stress. We hypothesized that the local response of coral species to thermal stress might be similarly reflected as a regional response to climate change. We assessed the contemporary geographic range of each species and determined their temperature and irradiance preferences using a k-fold algorithm to randomly select training and evaluation sites. That information was applied to downscaled outputs of global climate models to predict where each species is likely to exist by the year 2100. Our model was run with and without a 1 °C capacity to adapt to the rising ocean temperature. The results show a positive exponential relationship between the current area of habitat that coral species occupy and the predicted area of habitat that they will occupy by 2100. There was considerable decoupling between scales of response, however, and with further ocean warming some ‘winners’ at local scales will likely become ‘losers’ at regional scales. We predicted that nine of the 12 species examined will lose 24–50% of their current habitat. Most reductions are predicted to occur between the latitudes 5–15°, in both hemispheres. Yet when we modeled a 1 °C capacity to adapt, two ubiquitous species, Acropora hyacinthus and Acropora digitifera, were predicted to retain much of their current habitat. By contrast, the thermally tolerant Porites lobata is expected to increase its current distribution by 14%, particularly southward along the east and west coasts of Australia. Five areas were identified as Indian Ocean refugia, and seven areas were identified as Pacific Ocean refugia for reef corals under climate change. All 12 of these reef-coral refugia deserve high-conservation status.
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Cacciapaglia, C., & van Woesik, R. (2016). Climate-change refugia: shading reef corals by turbidity. Glob Change Biol, 22(3), 1145–1154.
Abstract: Coral reefs have recently experienced an unprecedented decline as the world's oceans continue to warm. Yet global climate models reveal a heterogeneously warming ocean, which has initiated a search for refuges, where corals may survive in the near future. We hypothesized that some turbid nearshore environments may act as climate-change refuges, shading corals from the harmful interaction between high sea-surface temperatures and high irradiance. We took a hierarchical Bayesian approach to determine the expected distribution of 12 coral species in the Indian and Pacific Oceans, between the latitudes 37°N and 37°S, under representative concentration pathway 8.5 (W m−2) by 2100. The turbid nearshore refuges identified in this study were located between latitudes 20�30°N and 15�25°S, where there was a strong coupling between turbidity and tidal fluctuations. Our model predicts that turbidity will mitigate high temperature bleaching for 9% of shallow reef habitat (to 30 m depth) � habitat that was previously considered inhospitable under ocean warming. Our model also predicted that turbidity will protect some coral species more than others from climate-change-associated thermal stress. We also identified locations where consistently high turbidity will likely reduce irradiance to <250 μmol m−2 s−1, and predict that 16% of reef-coral habitat ≤30 m will preclude coral growth and reef development. Thus, protecting the turbid nearshore refuges identified in this study, particularly in the northwestern Hawaiian Islands, the northern Philippines, the Ryukyu Islands (Japan), eastern Vietnam, western and eastern Australia, New Caledonia, the northern Red Sea, and the Arabian Gulf, should become part of a judicious global strategy for reef-coral persistence under climate change.
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Cacciapaglia, C., & van Woesik, R. (2018). Marine species distribution modelling and the effects of genetic isolation under climate change. J Biogeogr, 45(1), 154–163.
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Chutcharavan, P. M., Dutton, A., & Ellwood, M. J. (2018). Seawater 234 U/ 238 U recorded by modern and fossil corals. Geochimica et Cosmochimica Acta, 224, 1–17.
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Gouezo, M., Golbuu, Y., van Woesik, R., Rehm, L., Koshiba, S., & Doropoulos, C. (2015). Impact of two sequential super typhoons on coral reef communities in Palau. Mar. Ecol. Prog. Ser., 540, 73–85.
Abstract: Typhoons generally develop in the warm tropics, but rarely damage coral reefs between the latitudes 10 degrees N and 10 degrees S because they intensify at higher latitudes. However, climate change is forcing anomalous weather patterns, and is causing typhoons to take less predictable trajectories. For the first time in 70 yr, in December 2012, a super typhoon passed near the island of Palau, located at 7 degrees N in the western tropical Pacific Ocean. A year later, another super typhoon passed over the northern reefs of Palau. This study characterized the impacts of both typhoons on coral and fish assemblages in 3 habitats (i.e. outer reefs, patch reefs, and inner reefs) and at 2 depths (i.e. 3 and 10 m). Loss of coral cover was highest on the shallow, eastern slopes (similar to 60% coral cover). Juvenile coral densities decreased along the western reef slope and on the inner reefs, where overall coral cover scarcely decreased. These results suggested a potential stock-recruitment relationship with corals on the damaged eastern reefs. Early successional corals, particularly pocilloporids, recruited 6 mo after the second typhoon. Fish communities were generally un altered by the first typhoon, except small parrotfishes, which doubled in density along the eastern reef-slope and increased on the inner reefs following the second typhoon. In combination, these findings demonstrate high spatial variability in coral loss, overall decreases in juvenile corals, and increases in herbivorous fishes on a tropical reef system that has rarely experienced large typhoon waves.
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Lapointe, B. E., Brewton, R. A., Herren, L. W., Porter, J. W., & Hu, C. (2019). Nitrogen enrichment, altered stoichiometry, and coral reef decline at Looe Key, Florida Keys, USA: a 3-decade study. Mar Biol, 166(8).
Abstract: Increased loadings of nitrogen (N) from fertilizers, top soil, sewage, and atmospheric deposition are important drivers of eutrophication in coastal waters globally. Monitoring seawater and macroalgae can reveal long-term changes in N and phosphorus (P) availability and N:P stoichiometry that are critical to understanding the global crisis of coral reef decline. Analysis of a unique 3-decade data set for Looe Key reef, located offshore the lower Florida Keys, showed increased dissolved inorganic nitrogen (DIN), chlorophyll a, DIN:soluble reactive phosphorus (SRP) ratios, as well as higher tissue C:P and N:P ratios in macroalgae during the early 1990s. These data, combined with remote sensing and nutrient monitoring between the Everglades and Looe Key, indicated that the significant DIN enrichment between 1991 and 1995 at Looe Key coincided with increased Everglades runoff, which drains agricultural and urban areas extending north to Orlando, Florida. This resulted in increased P limitation of reef primary producers that can cause metabolic stress in stony corals. Outbreaks of stony coral disease, bleaching, and mortality between 1995 and 2000 followed DIN enrichment, algal blooms, and increased DIN:SRP ratios, suggesting that eutrophication interacted with other factors causing coral reef decline at Looe Key. Although water temperatures at Looe Key exceeded the 30.5 degrees C bleaching threshold repeatedly over the 3-decade study, the three mass bleaching events occurred only when DIN:SRP ratios increased following heavy rainfall and increased Everglades runoff. These results suggest that Everglades discharges, in conjunction with local nutrient sources, contributed to DIN enrichment, eutrophication, and increased N:P ratios at Looe Key, exacerbating P limitation, coral stress and decline. Improved management of water quality at the local and regional levels could moderate N inputs and maintain more balanced N:P stoichiometry, thereby reducing the risk of coral bleaching, disease, and mortality under the current level of temperature stress.
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Towle, E. K., Palacio-Castro, A. M., Baker, A. C., & Langdon, C. (2017). Source location and food availability determine the growth response of Orbicella faveolata to climate change stressors. Regional Studies in Marine Science, 10, 107–115.
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