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The health of coral reefs is threatened by simultaneous anthropogenic impacts, namely ocean acidification, ocean warming, elevated nutrients (nutrification) and sedimentation. These processes have been shown to reduce the ability of... more
The health of coral reefs is threatened by simultaneous anthropogenic impacts, namely ocean acidification, ocean warming, elevated nutrients (nutrification) and sedimentation. These processes have been shown to reduce the ability of corals to grow, but culturing experiments have previously demonstrated this response to vary across different reef environments and between different taxa. The absence of in-situ pH data, records of nutrient evolution and limited sea surface temperature (SST) measurements prior to the 1980s, has prevented the extent of either ocean acidification, nutrification or ocean warming to be quantified in Belize. Here, we have applied a multi-proxy approach (Li/Mg, Sr/Ca, Ba/Ca, δ11B, δ13C) to reconstruct these variables in corals from across the southern Mesoamerican Barrier Reef System over the last 100 years. We find that although the warming signal is spatially coherent, significant spatial variability exists in the extent of acidification and sediment input. Further investigations into the impact of such variability, and possible changes in net primary production must be conducted before we can conclude which anthropogenic stressor is responsible for the decline in forereef coral extension rates
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The health of coral reefs is threatened by simultaneous anthropogenic impacts, namely ocean acidification, ocean warming, elevated nutrients (nutrification) and sedimentation. These processes have been shown to reduce the ability of... more
The health of coral reefs is threatened by simultaneous anthropogenic impacts, namely ocean acidification, ocean warming, elevated nutrients (nutrification) and sedimentation. These processes have been shown to reduce the ability of corals to grow, but culturing experiments have previously demonstrated this response to vary across different reef environments and between different taxa. The absence of in-situ pH data, records of nutrient evolution and limited sea surface temperature (SST) measurements prior to the 1980s, has prevented the extent of either ocean acidification, nutrification or ocean warming to be quantified in Belize. Here, we have applied a multi-proxy approach (Li/Mg, Sr/Ca, Ba/Ca, δ11B, δ13C) to reconstruct these variables in corals from across the southern Mesoamerican Barrier Reef System over the last 100 years. We find that although the warming signal is spatially coherent, significant spatial variability exists in the extent of acidification and sediment input. Further investigations into the impact of such variability, and possible changes in net primary production must be conducted before we can conclude which anthropogenic stressor is responsible for the decline in forereef coral extension rates
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Anthropogenic elevation of atmospheric carbon dioxide (pCO2) is making the oceans more acidic, thereby reducing their degree of saturation with respect to calcium carbonate (CaCO3). There is mounting concern over the impact that future... more
Anthropogenic elevation of atmospheric carbon dioxide (pCO2) is making the oceans more acidic, thereby reducing their degree of saturation with respect to calcium carbonate (CaCO3). There is mounting concern over the impact that future CO2-induced reductions in the CaCO3 saturation state of seawater will have on marine organisms that construct their shells and skeletons from this mineral. Here, we present the results of 60 d laboratory experiments in which we investigated the effects of CO2-induced ocean acidification on calcification in 18 benthic marine organisms. Species were selected to span a broad taxonomic range (crustacea, cnidaria, echinoidea, rhodophyta, chlorophyta, gastropoda, bivalvia, annelida) and included organisms producing aragonite, low-Mg calcite, and high-Mg calcite forms of CaCO3. We show that 10 of the 18 species studied exhibited reduced rates of net calcification and, in some cases, net dissolution under elevated pCO2. However, in seven species, net calcification increased under the intermediate and/or highest levels of pCO2, and one species showed no response at all. These varied responses may reflect differences amongst organisms in their ability to regulate pH at the site of calcification, in the extent to which their outer shell layer is protected by an organic covering, in the solubility of their shell or skeletal mineral, and whether they utilize photosynthesis. Whatever the specific mechanism(s) involved, our results suggest that the impact of elevated atmospheric pCO2 on marine calcification is more varied than previously thought.
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Long-term, high-resolution measurements of environmental variability are sparse in the High Arctic. In the absence of such data, we turn to proxies recorded in the layered skeletons of the long-lived crustose coralline algae... more
Long-term, high-resolution measurements of environmental variability are sparse in the High Arctic. In the absence of such data, we turn to proxies recorded in the layered skeletons of the long-lived crustose coralline algae Clathromorphum compactum. Annual growth banding in this alga is dependent on several factors that include temperature, light availability, nutrients, salinity, and calcium carbonate saturation state. It has been observed that growth slows during winter as sunlight reaching the seafloor diminishes due to decreased insolation and the build-up of sea-ice, such that the relationship between sea-ice cover extent and algal growth has allowed for reconstructions of relative sea-ice variability through time. However, recent laboratory work has shown that C. compactum continue growing in complete darkness (sea-ice cover). Therefore, a more complete understanding of algal growth is necessary for the refinement of the sea-ice proxy. Here, we present the results of a ~year-...
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Seawater carbonate chemistry and carbon, oxygen and boron isotopes within Ochrosphaera neapolitana, supplement to: Liu, Yiwei; Eagle, Robert A; Aciego, Sarah M; Gilmore, Rosaleen E; Ries, Justin B (2018): A coastal coccolithophore maintains pH homeostasis and switches carbon sources in response t...more
Ocean acidification will potentially inhibit calcification by marine organisms; however, the response of the most prolific ocean calcifiers, coccolithophores, to this perturbation remains under characterized. Here we report novel chemical... more
Ocean acidification will potentially inhibit calcification by marine organisms; however, the response of the most prolific ocean calcifiers, coccolithophores, to this perturbation remains under characterized. Here we report novel chemical constraints on the response of the widespread coccolithophore species Ochrosphaera neapolitana (O. neapolitana) to changing-CO2 conditions. We cultured this algae under three pCO2-controlled seawater pH conditions (8.05, 8.22, and 8.33). Boron isotopes within the algae's extracellular calcite plates show that this species maintains a constant pH at the calcification site, regardless of CO2-induced changes in pH of the surrounding seawater. Carbon and oxygen isotopes in the algae's calcite plates and carbon isotopes in the algae's organic matter suggest that O. neapolitana utilize carbon from a single internal dissolved inorganic carbon (DIC) pool for both calcification and photosynthesis, and that a greater proportion of dissolved CO2 r...
Trophic cascades and climate change are together reshaping an iconic kelp forest ecosystem after the loss of sea otters.
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ABSTRACT
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The boron isotopic composition (δ 11 B) of limestones provides a potentially powerful tool for reconstructing seawater pH deep into the geologic past. Here, we present δ 11 B of 35 limestones spanning a ca. 9 my interval of the terminal... more
The boron isotopic composition (δ 11 B) of limestones provides a potentially powerful tool for reconstructing seawater pH deep into the geologic past. Here, we present δ 11 B of 35 limestones spanning a ca. 9 my interval of the terminal Proterozoic Nama Group (Namibia), which immediately precedes the Cambrian Radiation—the greatest diversification of metazoans in Earth history.
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Biogenic carbonate production in benthic marine ecosystems is dominated by representatives of the Echinodermata. Carbon and other major, minor, and trace elements are exported to the seabed where they accumulate or dissolve. Preserved... more
Biogenic carbonate production in benthic marine ecosystems is dominated by representatives of the Echinodermata. Carbon and other major, minor, and trace elements are exported to the seabed where they accumulate or dissolve. Preserved carbonates (Mg‐calcite) have applications in oceanography and geochemistry and are used to reconstruct various parameters of ancient seawater, such as temperature (from Mg/Ca, Sr/Ca), seawater Mg/Ca (from Mg/Ca), and pH (from B/Ca). In general, the benthos is widely ignored for its role in the global carbon cycle despite the importance of echinoderms as a carbon sink (∼0.1–0.2 Pg C/yr). Echinoderms produce their skeletons from Mg‐calcite, which is more soluble than pure calcite and, therefore, more vulnerable to ocean acidification (OA). Minor and trace elements can also destabilize the calcite lattice, increasing the mineral's solubility. Little is known about the concentration of such elements in echinoderm tests. Expanding our knowledge on echin...
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We conducted a 93-day experiment investigating the independent and combined effects of acidification (280−3300 µatm p CO 2 ) and warming (28°C and 31°C) on calcification and linear extension rates of four key Caribbean coral species (... more
We conducted a 93-day experiment investigating the independent and combined effects of acidification (280−3300 µatm p CO 2 ) and warming (28°C and 31°C) on calcification and linear extension rates of four key Caribbean coral species ( Siderastrea siderea , Pseudodiploria strigosa , Porites astreoides , Undaria tenuifolia ) from inshore and offshore reefs on the Belize Mesoamerican Barrier Reef System. All species exhibited nonlinear declines in calcification rate with increasing p CO 2 . Warming only reduced calcification in Ps. strigosa . Of the species tested, only S. siderea maintained positive calcification in the aragonite-undersaturated treatment . Temperature and p CO 2 had no effect on the linear extension of S. siderea and Po. astreoides, and natal reef environment did not impact any parameter examined. Results suggest that S. siderea is the most resilient of these corals to warming and acidification owing to its ability to maintain positive calcification in all treatments,...
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Ocean acidification is predicted to impair marine calcifiers' abilities to produce shells and skeletons. We conducted laboratory experiments investigating the impacts of CO2‐induced ocean acidification (pCO2 = 478–519, 734–835,... more
Ocean acidification is predicted to impair marine calcifiers' abilities to produce shells and skeletons. We conducted laboratory experiments investigating the impacts of CO2‐induced ocean acidification (pCO2 = 478–519, 734–835, 8,980–9,567; Ωcalcite = 7.3–5.7, 5.6–4.3, 0.6–0.7) on calcification rates of two estuarine calcifiers involved in a classic predator‐prey model system: adult Panopeus herbstii (Atlantic mud crab) and juvenile Crassostrea virginica (eastern oyster). Both oyster and crab calcification rates significantly decreased at the highest pCO2 level. Notably, however, oysters maintained positive net calcification rates in the highest pCO2 treatment that was undersaturated with respect to calcite, while mud crabs exhibited net dissolution (i.e., net loss of shell mass) in calcite‐undersaturated conditions. Secondary electron imaging of oyster shells revealed minor microstructural alterations in the moderate‐pCO2 treatment, and major microstructural and macrostructural changes (including shell dissolution, delamination of periostracum) in the high‐pCO2 treatment. These results underscore the threat that ocean acidification poses for marine organisms that produce calcium carbonate shells, illustrate the strong biological control that some marine calcifiers exert over their shell‐building process, and shows that ocean acidification differentially impacts the crab and oyster species involved in this classical predator‐prey model system.
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Global change driven by anthropogenic carbon emissions is altering ecosystems at unprecedented rates, especially coral reefs, whose symbiosis with algal symbionts is particularly vulnerable to increasing ocean temperatures and altered... more
Global change driven by anthropogenic carbon emissions is altering ecosystems at unprecedented rates, especially coral reefs, whose symbiosis with algal symbionts is particularly vulnerable to increasing ocean temperatures and altered carbonate chemistry. Here, we assess the physiological responses of three Caribbean coral (animal host + algal symbiont) species from an inshore and offshore reef environment after exposure to simulated ocean warming (28, 31°C), acidification (300–3290 μatm), and the combination of stressors for 93 days. We used multidimensional analyses to assess how a variety of coral physiological parameters respond to ocean acidification and warming. Our results demonstrate reductions in coral health inSiderastrea sidereaandPorites astreoidesin response to projected ocean acidification, while future warming elicited severe declines inPseudodiploria strigosa. OffshoreS.sidereafragments exhibited higher physiological plasticity than inshore counterparts, suggesting t...
Research Interests: Biology, Ecology, Multidisciplinary, Ocean acidification, Anthozoa, and 4 moreCoral Reef, PLoS one, Coral, and Reef
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Host‐associated microbial communities are fundamental to host physiology, yet it is unclear how these communities will respond to environmental disturbances. Here, we disentangle the environment‐linked and host‐linked effects of ocean... more
Host‐associated microbial communities are fundamental to host physiology, yet it is unclear how these communities will respond to environmental disturbances. Here, we disentangle the environment‐linked and host‐linked effects of ocean acidification on oyster‐associated microbial communities. We exposed adult oysters (Crassostrea virginica) to CO2‐induced ocean acidification (400 vs. 2800 ppm) for 80 d. We measured the oyster extrapallial fluid pH and sampled the gills for microbial analysis at six time points. We found that different subsets of microbes were linked to acidification (n = 34 amplicon sequence variants [ASVs]) and to host response (n = 20 ASVs) with little overlap (n = 8 ASVs), suggesting that some members of the oyster microbiome were more responsive to environmental conditions while others were more tightly linked to host condition. Our results provide insight into which members of the oyster microbiome may contribute to the health and resistance of their host, and w...
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Global change is threatening coral reefs, with rising temperatures leading to repeat bleaching events (dysbiosis of coral hosts and their symbiotic algae) and ocean acidification reducing net coral calcification. Although global-scale... more
Global change is threatening coral reefs, with rising temperatures leading to repeat bleaching events (dysbiosis of coral hosts and their symbiotic algae) and ocean acidification reducing net coral calcification. Although global-scale mass bleaching events are revealing fine-scale patterns of coral resistance and resilience, traits that lead to persistence under environmental stress remain elusive. Here, we conducted a 95-day controlled-laboratory experiment to investigate how duration of exposure to ocean warming (28, 31°C), acidification (pCO2 = 400–2800 μatm), and their interaction influence the physiological responses of two Caribbean reef-building coral species (Siderastrea siderea, Pseudodiploria strigosa) from two reef zones of the Belize Mesoamerican Barrier Reef System. Every 30 days, calcification rate, total host protein and carbohydrate, chlorophyll a pigment concentration, and symbiont cell density were quantified for the same coral colony to characterize acclimatory re...
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Corals are globally important calcifiers that exhibit complex responses to anthropogenic warming and acidification. Although coral calcification is supported by high seawater pH, photosynthesis by the algal symbionts of zooxanthellate... more
Corals are globally important calcifiers that exhibit complex responses to anthropogenic warming and acidification. Although coral calcification is supported by high seawater pH, photosynthesis by the algal symbionts of zooxanthellate corals can be promoted by elevated pCO2. To investigate the mechanisms underlying corals’ complex responses to global change, three species of tropical zooxanthellate corals (Stylophora pistillata, Pocillopora damicornis, and Seriatopora hystrix) and one species of asymbiotic cold-water coral (Desmophyllum pertusum, syn. Lophelia pertusa) were cultured under a range of ocean acidification and warming scenarios. Under control temperatures, all tropical species exhibited increased calcification rates in response to increasing pCO2. However, the tropical species’ response to increasing pCO2 flattened when they lost symbionts (i.e., bleached) under the high-temperature treatments—suggesting that the loss of symbionts neutralized the benefit of increased pC...
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Using as a basis the chain of cause and effect introduced in the Himalayan Environmental Degradation Theory which was postulated within the workings of the Himalayan Lowland Interaction, incidents of precipitation, soil erosion and runoff... more
Using as a basis the chain of cause and effect introduced in the Himalayan Environmental Degradation Theory which was postulated within the workings of the Himalayan Lowland Interaction, incidents of precipitation, soil erosion and runoff on small testplots were investigated in the case study project Bamti/Bhandar/Surma together with the suspended sediment delivery of a small catchment area in zones having