Posts Tagged 'temperature'

Reduced growth with increased quotas of particulate organic and inorganic carbon in the coccolithophore Emiliania huxleyi under future ocean climate change conditions

Effects of ocean acidification and warming on marine primary producers can be modulated by other environmental factors, such as levels of nutrients and light. Here, we investigated the interactive effects of five oceanic environmental drivers (CO2, temperature, light, dissolved inorganic nitrogen and phosphate) on growth rate, particulate organic (POC) and inorganic (PIC) carbon quotas of the cosmopolitan coccolithophore Emiliania huxleyi. Population growth rate increased with increasing temperature (16 to 20 °C) and light intensities (60 to 240 μmol photons m−2  s−1), but decreased with elevated pCO2 concentrations (370 to 960 μatm) and reduced availability of nitrate (24.3 to 7.8 μmol L−1) and phosphate (1.5 to 0.5 μmol L−1). POC quotas were predominantly enhanced by combined effects of increased pCO2 and decreased availability of phosphate. PIC quotas increased with decreased availability of nitrate and phosphate. Our results show that concurrent changes in nutrient concentrations and pCO2 levels predominantly affected growth, photosynthetic carbon fixation and calcification of E. huxleyi, and imply that plastic responses to progressive ocean acidification, warming and decreasing availability of nitrate and phosphate reduce population growth rate while increasing cellular quotas of particulate organic and inorganic carbon of E. huxleyi, ultimately affecting coccolithophore-related ecological and biogeochemical processes.

Continue reading ‘Reduced growth with increased quotas of particulate organic and inorganic carbon in the coccolithophore Emiliania huxleyi under future ocean climate change conditions’

Regional and species level responses of Scleractinian corals under global change within the Caribbean Sea

Human-induced global change has caused rapid increases in ocean temperature (warming) and declines in seawater pH (acidification), and are expected to have negative impacts on tropical reef-building corals globally. Abnormally high seawater temperatures disrupt the symbiosis between corals and their algal endosymbiont in a process known as ‘coral bleaching.’ During such bleaching events, calcification rates decline and physiological processes deteriorate. Additionally, corals rely heavily on elevated seawater pH in order to support and maintain production of their calcium carbonate skeletons. Together, changes in ocean temperatures and seawater pH pose serious threats to coral reefs, foundational ecosystems that provide habitat for countless essential fisheries, while also acting as natural buffers from storms and providing major economic support for tropical coastal communities. Identifying how these global scale stressors impact Caribbean coral reefs is critical in understanding community composition and coral abundance on future reefs. This dissertation employs an interdisciplinary suite of techniques to assess the impacts of ocean acidification and warming on the growth and physiology of Caribbean corals to improve understandings of the responses of coral under projected global change, and provide a framework for similar future studies. Through the use of a meta-analysis (Chapter 1), I identified trends in coral calcification throughout the Greater Caribbean Sea in response to experimental ocean acidification and warming, and performed quantitative assessment of experimental design effects on coral calcification rates. I then conducted a 93- day simulated ocean acidification and warming mesocosm experiment to identify growth (Chapter 2, 4) and physiological (Chapter 3) responses of several species of common Caribbean corals. The results from this work highlight the diversity of responses of Caribbean corals to projected global change at individual and species levels, as well as between the coral host and algal endosymbiont. Overall, the variation in growth and physiological responses of these important Caribbean coral species under ocean acidification and warming is critical in predicting the future ‘winners’ and ‘losers’ of Caribbean reefs as global change unfolds.

Continue reading ‘Regional and species level responses of Scleractinian corals under global change within the Caribbean Sea’

Plasticity of adult coralline algae to prolonged increased temperature and pCO2 exposure but reduced survival in their first generation

Crustose coralline algae (CCA) are vital to coral reefs worldwide, providing structural integrity and inducing the settlement of important invertebrate larvae. CCA are known to be impacted by changes in their environment, both during early development and adulthood. However, long-term studies on either life history stage are lacking in the literature, therefore not allowing time to explore the acclimatory or potential adaptive responses of CCA to future global change scenarios. Here, we exposed a widely distributed, slow growing, species of CCA, Sporolithon cf. durum, to elevated temperature and pCO2 for five months and their first set of offspring (F1) for eleven weeks. Survival, reproductive output, and metabolic rate were measured in adult S. cf. durum, and survival and growth were measured in the F1 generation. Adult S. cf. durum experienced 0% mortality across treatments and reduced their O2 production after five months exposure to global stressors, indicating a possible expression of plasticity. In contrast, the combined stressors of elevated temperature and pCO2 resulted in 50% higher mortality and 61% lower growth on germlings. On the other hand, under the independent elevated pCO2 treatment, germling growth was higher than all other treatments. These results show the robustness and plasticity of S. cf. durum adults, indicating the potential for them to acclimate to increased temperature and pCO2. However, the germlings of this species are highly sensitive to global stressors and this could negatively impact this species in future oceans, and ultimately the structure and stability of coral reefs.

Continue reading ‘Plasticity of adult coralline algae to prolonged increased temperature and pCO2 exposure but reduced survival in their first generation’

Acclimation history modulates effect size of calcareous algae (Halimeda opuntia) to herbicide exposure under future climate scenarios


•Calcifying algae were exposed to herbicide and future climate scenarios combined.

•Half of the algae were given long acclimation to future climate-change conditions.

•Experimental effects were exaggerated for algae that were not acclimated.

•Still, herbicide effects on acclimated algae stronger in future climate conditions

•Results show the need of climate-adjusted thresholds for water quality guidelines.


Tropical marine habitat-builders such as calcifying green algae can be susceptible to climate change (warming and acidification). This study evaluated the cumulative effects of ocean warming (OW), ocean acidification (OA) and the herbicide diuron on the calcifying green algae Halimeda opuntia. We also assessed the influence of acclimation history to experimental climate change conditions on physiological responses. H. opuntia were exposed for 15 days to orthogonal combinations of three climate scenarios [ambient (28 °C, pCO2 = 378 ppm), 2050 (29 °C, pCO2 = 567 ppm) and 2100 (30 °C, pCO2 = 721 ppm)] and to six diuron concentrations (up to 29 μg L−1). Half of the H. opuntia had been acclimated for eight months to the climate scenarios in a mesocosm approach, while the remaining half were not pre-acclimated, as is current practice in most experiments. Climate effects on quantum yield (ΔF/Fm′), photosynthesis and calcification in future climate scenarios were significantly stronger (by −24, −46 and +26%, respectively) in non-acclimated algae, suggesting experimental bias may exaggerate effects in organisms not appropriately acclimated to future-climate conditions. Thus, full analysis was done on acclimated plants only. Interactive effects of future climate scenarios and diuron were observed for ΔF/Fm′, while the detrimental effects of climate and diuron on net photosynthesis and total antioxidant capacity (TAC) were additive. Calcification-related enzymes were negatively affected only by diuron, with inhibition of Ca-ATPase and upregulation of carbonic anhydrase. The combined and consistent physiological and biochemical evidence of negative impacts (across six indicators) of both herbicide and future-climate conditions on the health of H. opuntia highlights the need to address both climate change and water quality. Guideline values for contaminants may also need to be lowered considering ‘climate adjusted thresholds’. Importantly, this study highlights the value of applying substantial future climate acclimation periods in experimental studies to avoid exaggerated organism responses to OW and OA.

Continue reading ‘Acclimation history modulates effect size of calcareous algae (Halimeda opuntia) to herbicide exposure under future climate scenarios’

The influence of plastic pollution and ocean change on detrital decomposition


•The combined effects of plastic pollution, ocean warming, and acidification on macrophyte decomposition were tested.

•High quantities of plastic slowed the decomposition of seagrass and kelp.

•Ocean warming increased the decomposition rates of seagrass and kelp.

•Ocean acidification did not significantly influence macrophyte decomposition.

•Reducing plastic pollution and CO2 emissions is likely the best approach for preserving detritus-based ecosystem processes.


Plastic pollution and ocean change have mostly been assessed separately, missing potential interactions that either enhance or reduce future impacts on ecosystem processes. Here, we used manipulative experiments with outdoor mesocosms to test hypotheses about the interactive effects of plastic pollution, ocean warming and acidification on macrophyte detrital decomposition. These experiments focused on detritus from kelp, Ecklonia radiata, and eelgrass, Zostera muelleri, and included crossed treatments of (i) no, low and high plastic pollution, (ii) current/future ocean temperatures, and (iii) ambient/future ocean partial pressure of carbon dioxide (pCO2). High levels of plastic pollution significantly reduced the decomposition rate of kelp and eelgrass by approximately 27% and 36% in comparison to controls respectively. Plastic pollution also significantly slowed the nitrogen liberation from seagrass and kelp detritus. Higher seawater temperatures significantly increased the decomposition rate of kelp and eelgrass by 12% and 5% over current conditions, respectively. Higher seawater temperatures were also found to reduce the nitrogen liberation in eelgrass. In contrast, ocean acidification did not significantly influence the rate of macrophyte decomposition or nutrient liberation. Overall, our results show how detrital processes might respond to increasing plastic pollution and ocean temperatures, which has implications for detrital-driven secondary productivity, nutrient dynamics and carbon cycling.

Continue reading ‘The influence of plastic pollution and ocean change on detrital decomposition’

Interactive effects of pH and temperature on native and alien mussels from the west coast of South Africa

Global warming and ocean acidification influence marine calcifying organisms, particularly those with external shells. Among these, mussels may compensate for environmental changes by phenotypic plasticity, but this may entail trade-offs between shell deposition, growth and reproduction. We assessed main and interactive effects of pH and temperature on four mussel species on the west coast of South Africa (33°48′ S, 18°27′ E) in October 2012 by comparing shell dissolution, shell growth, shell breaking force and condition index of two native species, the ribbed mussel Aulacomya atra and the black mussel Choromytilus meridionalis, and two aliens, the Mediterranean mussel Mytilus galloprovincialis and the bisexual mussel Semimytilus algosus. Live mussels and dead shells were exposed for 42 days to seawater of pH 7.5 or 8.0, at 14 °C or 20 °C. Low pH, high temperature and their combination increased shell dissolution of the two aliens but their growth rates and condition indices remained unchanged. Aulacomya atra also experienced greater shell dissolution at a low pH and high temperature, but grew faster in low-pH treatments. For C. meridionalis, shell dissolution was unaffected by pH or temperature; it also grew faster in low-pH treatments, but had a lower condition index in the higher temperature treatment. Shell strength was not determined by thickness alone. In most respects, all four species proved to be robust to short-term reduction of pH and elevation of temperature, but the native species compensated for greater shell dissolution at low pH by increasing growth rate, whereas the aliens did not, so their invasive success cannot be ascribed to benefits accruing from climate change.

Continue reading ‘Interactive effects of pH and temperature on native and alien mussels from the west coast of South Africa’

Antagonistic interactions and clutch-dependent sensitivity induce variable responses to ocean acidification and warming in squid (Doryteuthis pealeii) embryos and paralarvae

Ocean acidification (OA) and warming seas are significant concerns for coastal systems and species. The Atlantic longfin squid, Doryteuthis pealeii, a core component of the Northwest Atlantic trophic web, has demonstrated impacts, such as reduced growth and delayed development, under high chronic exposure to acidification (2200 ppm), but the combined effects of OA and warming have not been explored in this species. In this study, D. pealeii egg capsules were reared under a combination of several acidification levels (400, 2200, and 3500 ppm) and temperatures (20 and 27°C). Hatchlings were measured for a range of metrics [dorsal mantle length (DML), yolk sac volume (YV), malformation, and hatching success] in three trials over the 2016 breeding season (May – October). Although notable resistance to stressors was seen, highlighting variability within and between clutches, reduced DML and malformation of the embryos occurred at the highest OA exposure. Surprisingly, increased temperatures did not appear to exacerbate OA impacts, although responses were variable. Time to hatching, which increased with acidification, decreased much more drastically under warming and, further, decreased or removed delays caused by acidification. Hatching success, while variable by clutch, showed consistent patterns of greater late stage loss of embryos under acidification and greater early stage loss under warming, highlighting the potential difference in timing between these stressors for this system, i.e., that acidification stress builds up and causes impacts over time within the egg capsule as the embryos grow and respire. High OA-exposed hatchlings from the warmer conditions often showed reduced impacts compared to those reared in ambient temperatures. This may be due to the increased developmental rate and subsequently reduced OA exposure time of embryos in the higher temperature treatment. These results indicate a substantive potential plasticity to multiple stressors during the embryonic development of this species of squid, but do not predict how this species would fare under these future ocean scenarios.

Continue reading ‘Antagonistic interactions and clutch-dependent sensitivity induce variable responses to ocean acidification and warming in squid (Doryteuthis pealeii) embryos and paralarvae’

Ocean warming increases availability of crustacean prey via riskier behavior

Marine prey and predators will respond to future climate through physiological and behavioral adjustments. However, our understanding of how such direct effects may shift the outcome of predator–prey interactions is still limited. Here, we investigate the effects of ocean warming and acidification on foraging behavior and biomass of a common prey (shrimps, Palaemon spp.) tested in large mesocosms harboring natural resources and habitats. Acidification did not alter foraging behavior in prey. Under warming, however, prey showed riskier behavior by foraging more actively and for longer time periods, even in the presence of a live predator. No effects of longer-term exposure to climate stressors were detected on prey biomass. Our findings suggest that ocean warming may increase the availability of some prey to predators via a behavioral pathway (i.e., increased risk-taking by prey), likely by elevating metabolic demand of prey species.

Continue reading ‘Ocean warming increases availability of crustacean prey via riskier behavior’

Spatial risk assessment of global change impacts on Swedish seagrass ecosystems

Improved knowledge on the risk in ecologically important habitats on a regional scale from multiple stressors is critical for managing functioning and resilient ecosystems. This risk assessment aimed to identify seagrass ecosystems in southern Sweden that will be exposed to a high degree of change from multiple global change stressors in mid- and end-of-century climate change conditions. Risk scores were calculated from the expected overlap of three stressors: sea surface temperature increases, ocean acidification and wind driven turbid conditions. Three high-risk regions were identified as areas likely to be exposed to a particularly high level of pressure from the global stressors by the end of the century. In these areas it can be expected that there will be a large degree of stressor change from the current conditions. Given the ecological importance of seagrass meadows for maintaining high biodiversity and a range of other ecosystem services, these risk zones should be given high priority for incorporation into management strategies, which can attempt to reduce controllable stressors in order to mitigate the consequences of some of the impending pressures and manage for maintained ecosystem resilience.

Continue reading ‘Spatial risk assessment of global change impacts on Swedish seagrass ecosystems’

Effects of irradiance, temperature, nutrients, and pCO2 on the growth and biochemical composition of cultivated Ulva fenestrata

Ulva fenestrata is an economically and ecologically important green algal species with a large potential in seaweed aquaculture due to its high productivity, wide environmental tolerance, as well as interesting functional and nutritional properties. Here, we performed a series of manipulative cultivation experiments in order to investigate the effects of irradiance (50, 100, and 160 μmol photons m−2 s−1), temperature (13 and 18 °C), nitrate (< 5, 150, and 500 μM), phosphate (< 1 and 50 μM), and pCO2 (200, 400, and 2500 ppm) on the relative growth rate and biochemical composition (fatty acid, protein, phenolic, ash, and biochar content) in indoor tank cultivation of Swedish U. fenestrata. High irradiance and low temperature were optimal for the growth of this northern hemisphere U. fenestrata strain, but addition of nutrients or changes in pCO2 levels were not necessary to increase growth. Low irradiance resulted in the highest fatty acid, protein, and phenolic content, while low temperature had a negative effect on the fatty acid content but a positive effect on the protein content. Addition of nutrients (especially nitrate) increased the fatty acid, protein, and phenolic content. High nitrate levels decreased the total ash content of the seaweeds. The char content of the seaweeds did not change in response to any of the manipulated factors, and the only significant effect of changes in pCO2 was a negative relationship with phenolic content. We conclude that the optimal cultivation conditions for Swedish U. fenestrata are dependent on the desired biomass traits (biomass yield or biochemical composition).

Continue reading ‘Effects of irradiance, temperature, nutrients, and pCO2 on the growth and biochemical composition of cultivated Ulva fenestrata’

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Ocean acidification in the IPCC AR5 WG II

OUP book