Direct and indirect effects of ocean acidification and warming on a marine plant–herbivore interaction

The impacts of climatic change on organisms depend on the interaction of multiple stressors and how these may affect the interactions among species. Consumer–prey relationships may be altered by changes to the abundance of either species, or by changes to the per capita interaction strength among species. To examine the effects of multiple stressors on a species interaction, we test the direct, interactive effects of ocean warming and lowered pH on an abundant marine herbivore (the amphipod Peramphithoe parmerong), and whether this herbivore is affected indirectly by these stressors altering the palatability of its algal food (Sargassum linearifolium). Both increased temperature and lowered pH independently reduced amphipod survival and growth, with the impacts of temperature outweighing those associated with reduced pH. Amphipods were further affected indirectly by changes to the palatability of their food source. The temperature and pH conditions in which algae were grown interacted to affect algal palatability, with acidified conditions only affecting feeding rates when algae were also grown at elevated temperatures. Feeding rates were largely unaffected by the conditions faced by the herbivore while feeding. These results indicate that, in addition to the direct effects on herbivore abundance, climatic stressors will affect the strength of plant–herbivore interactions by changes to the susceptibility of plant tissues to herbivory.

NOAA ocean acidification June teacher workshops in South Florida (stipends provided)

NOAA Coral Reef Conservation Program cordially invites teachers in the south Florida area to attend a one-day workshop on ocean acidification, introducing our new OA Data-in-the-Classroom NODE module. Teachers will learn to use real data from NOAA to teach ocean acidification and how it affects coral reefs and other marine calcifiers, using integrated scalable lesson plans associated with this module. Workshop will include demos and multimedia to use in your classroom, a background science presentation on ocean acidification, and a walk-through of the five scalable lesson plans and data exercises that are part of this Data-in-the-Classroom project. Teachers will receive $75 stipend for workshop participation and $25 stipend after follow up survey. Teachers will also receive additional educational materials on coral reefs and ocean acidification, including posters, OA teachers guide, and multimedia DVDs. Limited seating: Participants will receive confirmation email once their registration is processed.

NODC ocean acidification scientific data stewardship – data and metadata submission and documentation guidelines

The NODC Ocean Acidification Scientific Data Stewardship (OADS) team has developed ocean acidification (OA) data and metadata submission guidelines and documentation designed for optimized data discovery, transparent access, data sharing, long-term archival and scientific management of NOAA Ocean Acidification Program (OAP) funded data projects. This document addresses OA data from ships of opportunity, autonomous sensor data (e.g., moorings), gliders, research ships (e.g., discrete water samples from Niskins, CTD data, underway), laboratory and field experiments, and models. All of the NODC archived data are available via our geoportal and other interoperable NODC data services. In addition, our OADS Team is working toward developing a dedicated online OA data selection tool with enhanced search capabilities based on our rich OA metadata using ISO 19115-2.

Interactive effects of elevated temperature and CO2 levels on energy metabolism and biomineralization of marine bivalves Crassostrea virginica and Mercenaria mercenaria

The continuing increase of carbon dioxide (CO₂) levels in the atmosphere leads to increases in global temperatures and partial pressure of CO₂ (P_CO2) in surface waters, causing ocean acidification. These changes are especially pronounced in shallow coastal and estuarine waters and are expected to significantly affect marine calcifiers including bivalves that are ecosystem engineers in estuarine and coastal communities. To elucidate potential effects of higher temperatures and P_CO2 on physiology and biomineralization of marine bivalves, we exposed two bivalve species, the eastern oysters Crassostrea virginica and the hard clams Mercenaria mercenaria to different combinations of P_CO2 (~ 400 and 800 μatm) and temperatures (22 and 27 °C) for 15 weeks. Survival, bioenergetic traits (tissue levels of lipids, glycogen, glucose and high energy phosphates) and biomineralization parameters (mechanical properties of the shells and activity of carbonic anhydrase, CA) were determined in clams and oysters under different temperature and P_CO2 regimes. Our analysis showed major inter-species differences in shell mechanical traits and bioenergetics parameters. Elevated temperature led to the depletion of tissue energy reserves indicating energy deficiency in both species and resulted in higher mortality in oysters. Interestingly, while elevated P_CO2 had a small effect on the physiology and metabolism of both species, it improved survival in oysters. At the same time, a combination of high temperature and elevated P_CO2 lead to a significant decrease in shell hardness in both species, suggesting major changes in their biomineralization processes. Overall, these studies show that global climate change and ocean acidification might have complex interactive effects on physiology, metabolism and biomineralization in coastal and estuarine marine bivalves.

Paul G. Allen Ocean Challenge – updated notice

Two informational webinars have been held to date regarding the Paul G. Allen Ocean Challenge: Mitigating Acidification Impacts. Webinar recordings and registration information, answers to frequently asked questions, and submission guidelines are all available here.

To aid planning efforts for submission evaluation for this Ocean Challenge as well as planning for future projects, responses to a three-question survey are requested from the community.  Please take a moment to provide feedback by June 5, 2013 here.

Unexpected effects of ocean acidification on deep-sea organisms

About 55.5 million years ago, geologically rapid emission of a large volume of greenhouse gases at the Paleocene-Eocene boundary (PETM) led to global warming of about 5oC, severe ocean acidification, and widespread extinction of microscopic organisms living on the deep-sea floor (foraminifera).

A study of survivors of the extinction provides unique insight into the response of deep-sea calcifiers to past episodes which resemble the potential future consequences of fossil fuel CO2 emissions. The organisms, contrary to expectations from experiments, actually increased the thickness of their shells during ocean acidification, with organisms living buried within the sediment able to survive better than forms living on the sediment surface.

The research, by scientists from the University of Bristol (UK) and Yale University (USA), is reported in this week’s early edition of the Proceedings of the National Academies of Science.

Surviving rapid climate change in the deep sea during the Paleogene hyperthermals

Predicting the impact of ongoing anthropogenic CO₂ emissions on calcifying marine organisms is complex, owing to the synergy between direct changes (acidification) and indirect changes through climate change (e.g., warming, changes in ocean circulation, and deoxygenation). Laboratory experiments, particularly on longer-lived organisms, tend to be too short to reveal the potential of organisms to acclimatize, adapt, or evolve and usually do not incorporate multiple stressors. We studied two examples of rapid carbon release in the geological record, Eocene Thermal Maximum 2 (∼53.2 Ma) and the Paleocene Eocene Thermal Maximum (PETM, ∼55.5 Ma), the best analogs over the last 65 Ma for future ocean acidification related to high atmospheric CO₂ levels. We use benthic foraminifers, which suffered severe extinction during the PETM, as a model group. Using synchrotron radiation X-ray tomographic microscopy, we reconstruct the calcification response of survivor species and find, contrary to expectations, that calcification significantly increased during the PETM. In contrast, there was no significant response to the smaller Eocene Thermal Maximum 2, which was associated with a minor change in diversity only. These observations suggest that there is a response threshold for extinction and calcification response, while highlighting the utility of the geological record in helping constrain the sensitivity of biotic response to environmental change.

Coccolithophores thrive despite ocean acidification

Ocean acidification is damaging some marine species while others thrive, say scientists.

An international team studied the effect of ocean acidification on plankton in the North Sea over the past forty years, to see what impact future changes may have.

The study, published in PLoS One found that different species react in different ways to changes in their environment. As carbon dioxide emissions dissolve in seawater they lower the pH of the oceans making them more acidic and more corrosive to shells.

Physiological compensation for environmental acidification is limited in the deep-sea urchin Strongylocentrotus fragilis

Anthropogenic CO₂ is now reaching depths over 1000 m in the Eastern Pacific, overlapping the Oxygen Minimum Zone (OMZ). Deep-sea animals – particularly, calcifiers – are suspected to be especially sensitive to environmental acidification associated with global climate change. We have investigated the effects of hypercapnia and hypoxia on the deep-sea urchin Strongylocentrotus fragilis, during two long-term exposure experiments (1 month and 4 month) at three levels of reduced pH at in situ O₂ levels of approx. 10% saturation, and also to control pH at 100% O₂ saturation. During the first experiment, internal acid-base balance was investigated during a one-month exposure; results show S. fragilis has limited ability to compensate for the respiratory acidosis brought on by reduced pH, due in part to low non-bicarbonate extracellular fluid buffering capacity. During the second experiment, longer-term effects of hypercapnia and variable O₂ on locomotion, feeding, growth, and gonadosomatic index (GSI) were investigated; results show significant mortality and correlation of all measured parameters with environmental acidification at pH 6.6. Transient adverse effects on locomotion and feeding were seen at pH 7.2, without compromise of growth or GSI. Based on the expected changes in ocean pH and oxygen, results suggest extinction of S. fragilis in the eastern North Pacific is unlikely. Rather, we expect a shoaling and contraction of its bathymetric range.

CO2-driven ocean acidification reduces larval feeding efficiency and change food selectivity in the mollusk Concholepas concholepas

We present experimental data obtained from an experiment with newly hatched veliger larvae of the gastropod Concholepas concholepas exposed to three pCO₂ levels. Egg capsules were collected from two locations in northern and central Chile, and then incubated throughout their entire intra-capsular life cycle at three nominal pCO₂ levels, ∼400, 700 and 1000 ppm (i.e. corresponding to ∼8.0, 7.8 and 7.6 pH units, respectively). Hatched larvae were fed with natural food assemblages. Food availability at time zero did not vary significantly with pCO₂ level. Our results clearly showed a significant effect of elevated pCO₂ on the intensity of larval feeding, which dropped by >60%. Incubation also showed that pCO₂-driven ocean acidification (OA) may radically impact the selectivity of ingested food by C. concholepas larvae. Results also showed that larvae switched their clearance rate based on large cells, such as diatoms and dinoflagellates to tiny and highly abundant nanoflagellates and cyanobacteria as pCO₂ levels increased. Thus, this study reveals the important effect of low pH conditions on larval feeding behavior, in terms of both ingestion magnitude and selectivity. These findings support the notion that larval feeding is a key physiological process susceptible to the effects of OA.