Functional genetic divergence in high CO2 adapted Emiliania huxleyi populations

Predicting the impacts of environmental change on marine organisms, food webs and biogeochemical cycles presently relies almost exclusively on short-term physiological studies, while the possibility of adaptive evolution is often ignored. Here we assess adaptive evolution in the coccolithophore Emiliania huxleyi, a well-established model species in biological oceanography, in response to ocean acidification. We previously demonstrated that this globally important marine phytoplankton species adapts within 500 generations to elevated CO₂. After 750 and 1000 generations no further fitness increase occurred, and we observed phenotypic convergence between replicate populations. In this study, we exposed adapted populations to two novel environments to investigate whether or not the underlying basis for high CO₂-adaptation involves functional genetic divergence, where different novel mutations become apparent via divergent pleiotropic effects. The novel environment “high light” did not reveal such genetic divergence while growth in a low salinity environment revealed strong pleiotropic effects in high CO₂ adapted populations, indicating divergent genetic bases for adaptation to high CO₂. This suggests that pleiotropy plays an important role in adaptation of natural E. huxleyi populations to ocean acidification. Our study highlights the potential mutual benefits for oceanography and evolutionary biology of using ecologically important marine phytoplankton for microbial evolution experiments.

Decline in growth of foraminifer Marginopora rossi under eutrophication and ocean acidification scenarios

The combination of global and local stressors is leading to a decline in coral reef health globally. In the case of eutrophication, increased concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) are largely attributed to local land use changes. From the global perspective, increased atmospheric CO₂ levels are not only contributing to global warming but also ocean acidification (OA). Both eutrophication and OA have serious implications for calcium carbonate production and dissolution among calcifying organisms. In particular, benthic foraminifera precipitate the most soluble form of mineral calcium carbonate (high-Mg calcite), potentially making them more sensitive to dissolution. In the present study a manipulative orthogonal two-factor experiment was conducted to test the effects of dissolved inorganic nutrients and OA on the growth, respiration and photophysiology of the large photosymbiont-bearing benthic foraminifer, Marginopora rossi. This study found the growth rate of M. rossi was inhibited by the interaction of eutrophication and acidification. The relationship between M. rossi and its photosymbionts became destabilised due to the photosymbiont’s release from nutrient limitation in the nitrate-enriched treatment, as shown by an increase in zooxanthellae cells per host surface area. Foraminifers from the OA treatments had an increased amount of Chl a per cell, suggesting a greater potential to harvest light energy, however there was no net benefit to foraminifer growth. Overall, this study demonstrates that the impacts of OA and eutrophication are dose-dependant and interactive. This research indicates an OA threshold at pH 7.6, alone or in combination with eutrophication, will lead to a decline in M. rossi calcification. The decline in foraminifera calcification associated with pollution and OA will have broad ecological implications across their ubiquitous range and suggests that without mitigation it could have serious implications for the future of coral reefs.

Competition between calcifying and noncalcifying temperate marine macroalgae under elevated CO2 levels

Since pre-industrial times, uptake of anthropogenic CO₂ by surface ocean waters has caused a documented change of 0.1 pH units. Calcifying organisms are sensitive to elevated CO₂ concentrations due to their calcium carbonate skeletons. In temperate rocky intertidal environments, calcifying and noncalcifying macroalgae make up diverse benthic photoautotrophic communities. These communities may change as calcifiers and noncalcifiers respond differently to rising CO₂ concentrations. In order to test this hypothesis, we conducted an 86 d mesocosm experiment to investigate the physiological and competitive responses of calcifying and noncalcifying temperate marine macroalgae to 385, 665, and 1486 µatm CO₂. We focused on comparing 2 abundant red algae in the Northeast Atlantic: Corallina officinalis (calcifying) and Chondrus crispus (noncalcifying). We found an interactive effect of CO₂ concentration and exposure time on growth rates of C. officinalis, and total protein and carbohydrate concentrations in both species. Photosynthetic rates did not show a strong response. Calcification in C. officinalis showed a parabolic response, while skeletal inorganic carbon decreased with increasing CO₂. Community structure changed, as Chondrus crispus cover increased in all treatments, while C. officinalis cover decreased in both elevated-CO₂ treatments. Photochemical parameters of other species are also presented. Our results suggest that CO₂ will alter the competitive strengths of calcifying and noncalcifying temperate benthic macroalgae, resulting in different community structures, unless these species are able to adapt at a rate similar to or faster than the current rate of increasing sea-surface CO₂ concentrations.

Effects of CO2 and the harmful alga Aureococcus anophagefferens on growth and survival of oyster and scallop larvae

Globally, the frequency of harmful algal blooms is increasing and CO₂ concentrations are rising. These factors represent serious challenges to a multitude of estuarine organisms as well as to efforts to restore depleted stocks of filter-feeding bivalves. In this study, we compared the responses of larval bivalves Crassostrea virginica and Argopecten irradians to the brown tide alga Aureococcus anophagefferens (250 × 10⁶ cells l⁻¹ and 1 × 10⁹ cells l⁻¹, respectively) and a gradient of CO₂ concentrations (~240, ~390, and ~850 ppm). Results indicated that A. anophagefferens and higher levels of CO₂ significantly depressed rates of survival, development, growth, and lipid synthesis of A. irradians larvae with the combination of both factors having the largest effects. C. virginica larvae were also negatively impacted by the harmful alga and elevated CO₂, but displayed a higher overall survival rate when exposed to these combined stressors. For both species, high densities of A. anophagefferens (10⁹ cells l⁻¹) elicited a stronger negative effect on larval survival than high levels of CO₂ concentrations (~850 ppm). Collectively, these results demonstrate that the concurrent occurrence of harmful algal blooms and high CO₂ concentrations will have negative consequences for bivalve populations and further demonstrate that some species of larval bivalves are more resistant to these stressors than others.

Virtual tour: Google Earth dives into ocean acidification

Monterey (global-adventures.us): Google Earth will soon offer a virtual tour around the world to explain ocean acidification and its rapid effects on marine life and humanity. The chemistry of one half of the Arctic Ocean, for example, will be changed by 2050 if Carbon Dioxide (CO2) levels continue to rise at current rates. The new feature and a new guide on ocean acidification were launched at The Ocean in a High CO2 World Symposium in Monterey, California.

“The new knowledge and multimedia guides released today open up ocean acidification so everyone can explore from their desktops what our current carbon dioxide emissions may mean to the ocean, and to us, in the very near future,” says Dan Laffoley, Marine Vice Chair of the International Union for Conservation of Nature (IUCN) World Commission on Protected Areas and Chair of Europe’s Ocean Acidification Reference User Group.

Ocean acidification leaves mollusks naked and confused

When the carbon dioxide absorbed by the oceans dissolves in seawater, carbonic acid is formed and calcium carbonate, vital for the formation of the skeletons and shells of many marine organisms, becomes scarcer.

MONTEREY, United States, Oct 1 (Tierramérica).- Climate change will ruin Chilean sea snails’ ability to sniff out and avoid their archenemy, a predatory crab, according to Chilean scientists who presented their findings at an international science symposium here.

Sea creatures in a warming world: winners and losers

MONTEREY, Calif. — The world’s oceans are getting more acidic, a phenomenon predicted to wreak havoc on most sea life. But some organisms are performing better in these caustic conditions than researchers had anticipated, raising questions about what the oceans will look like in the future.

“We know evolution can occur on relatively short ecological timescales,” said Gretchen Hofmann, a biologist at the University of California at Santa Barbara, at the Third International Symposium on the Oceans in a High CO2 World meeting last week. She added that the big remaining question is which species will survive, and which won’t be able to cope.

Changes in microbial communities associated with the sea anemone Anemonia viridis in a natural pH gradient

Ocean acidification, resulting from rising atmospheric carbon dioxide concentrations, is a pervasive stressor that can affect many marine organisms and their symbionts. Studies which examine the host physiology and microbial communities have shown a variety of responses to the ocean acidification process. Recently, several studies were conducted based on field experiments, which take place in natural CO(2) vents, exposing the host to natural environmental conditions of varying pH. This study examines the sea anemone Anemonia viridis which is found naturally along the pH gradient in Ischia, Italy, with an aim to characterize whether exposure to pH impacts the holobiont. The physiological parameters of A. viridis (Symbiodinium density, protein, and chlorophyll a+c concentration) and its microbial community were monitored. Although reduction in pH was seen to have had an impact on composition and diversity of associated microbial communities, no significant changes were observed in A. viridis physiology, and no microbial stress indicators (i.e., pathogens, antibacterial activity, etc.) were detected. In light of these results, it appears that elevated CO(2) does not have a negative influence on A. viridis that live naturally in the site. This suggests that natural long-term exposure and dynamic diverse microbial communities may contribute to the acclimation process of the host in a changing pH environment.

Impact of ocean acidification on plankton larvae as a cause of mass extinctions in ammonites and belemnites

Among the ten strong and catastrophic extinctions of ammonites and belemnites in geological history of Earth, at least eight of them (mainly for ammonites) occurred during the development of oceanic acidification events. Our analysis shows that the most vulnerable ontogenetic phase of these animals to oceanic acidification was their small and mainly planktonic paralarvae with either outer (ammonites) or inner (belemnites) calcareous shells. The thin walls of the paralarval shell with aragonite phragmocone serving to keep the neutral buoyancy might have prevented them to migrate deeper than the implosion depth (from several meters to first tens meters). Strong short-term ocean acidification events were the strongest in superficial water layers of the open ocean and shallow waters on the shelf, the very habitats of ammonitellas and paralarval belemnites, with catastrophic impact on integrity of their tiny calcareous shells. We suggest that the damage and corresponding malfunction of the fragile phragmocone to keep the neutral buoyancy was crucial during the development of ocean acidification. Disastrous short-term ocean acidification events contributed to extinctions of the calcareous plankton in Mesozoic, regardless whether they were planktonic during the entire life (e.g., coccolithophorids, foraminifers) or just during a relatively short ontogenetic phase as in ammonites and belemnites.

Predicting interactions among fishing, ocean warming, and ocean acidification in a marine system with whole-ecosystem models

An important challenge for conservation is a quantitative understanding of how multiple human stressors will interact to mitigate or exacerbate global environmental change at a community or ecosystem level. We explored the interaction effects of fishing, ocean warming, and ocean acidification over time on 60 functional groups of species in the southeastern Australian marine ecosystem. We tracked changes in relative biomass within a coupled dynamic whole-ecosystem modeling framework that included the biophysical system, human effects, socioeconomics, and management evaluation. We estimated the individual, additive, and interactive effects on the ecosystem and for five community groups (top predators, fishes, benthic invertebrates, plankton, and primary producers). We calculated the size and direction of interaction effects with an additive null model and interpreted results as synergistic (amplified stress), additive (no additional stress), or antagonistic (reduced stress). Individually, only ocean acidification had a negative effect on total biomass. Fishing and ocean warming and ocean warming with ocean acidification had an additive effect on biomass. Adding fishing to ocean warming and ocean acidification significantly changed the direction and magnitude of the interaction effect to a synergistic response on biomass. The interaction effect depended on the response level examined (ecosystem vs. community). For communities, the size, direction, and type of interaction effect varied depending on the combination of stressors. Top predator and fish biomass had a synergistic response to the interaction of all three stressors, whereas biomass of benthic invertebrates responded antagonistically. With our approach, we were able to identify the regional effects of fishing on the size and direction of the interacting effects of ocean warming and ocean acidification.