Predicted levels of future ocean acidification and temperature rise could alter community structure and biodiversity in marine benthic communities

A mesocosm experiment was conducted to quantify the effects of reduced pH and elevated temperature on an intact marine invertebrate community. Standardised faunal communities, collected from the extreme low intertidal zone using artificial substrate units, were exposed to one of eight nominal treatments (four pH levels: 8.0, 7.7, 7.3 and 6.7, crossed with two temperature levels: 12 and 16°C). After 60 days exposure communities showed significant changes in structure and lower diversity in response to reduced pH. The response to temperature was more complex. At higher pH levels (8.0 and 7.7) elevated temperature treatments contained higher species abundances and diversity than the lower temperature treatments. In contrast, at lower pH levels (7.3 and 6.7), elevated temperature treatments had lower species abundances and diversity than lower temperature treatments. The species losses responsible for these changes in community structure and diversity were not randomly distributed across the different phyla examined. Molluscs showed the greatest reduction in abundance and diversity in response to low pH and elevated temperature, whilst annelid abundance and diversity was mostly unaffected by low pH and was higher at the elevated temperature. The arthropod response was between these two extremes with moderately reduced abundance and diversity at low pH and elevated temperature. Nematode abundance increased in response to low pH and elevated temperature, probably due to the reduction of ecological constraints, such as predation and competition, caused by a decrease in macrofaunal abundance. This community-based mesocosm study supports previous suggestions, based on observations of direct physiological impacts, that ocean acidification induced changes in marine biodiversity will be driven by differential vulnerability within and between different taxonomical groups. This study also illustrates the importance of considering indirect effects that occur within multispecies assemblages when attempting to predict the consequences of ocean acidification and global warming on marine communities.

Will variation among genetic individuals influence species responses to global climate change?

Increased anthropogenic CO2 emissions in the last two centuries have lead to rising sea surface temperature and falling ocean pH, and it is predicted that current global trends will worsen over the next few decades. There is limited understanding of how genetic variation among individuals will influence the responses of populations and species to these changes. A microcosm system was set up to study the effects of predicted temperature and CO2 levels on the bryozoan Celleporella hyalina. In this marine species, colonies grow by the addition of male, female and feeding modular individuals (zooids) and can be physically subdivided to produce a clone of genetically identical colonies. We studied colony growth rate (the addition of zooids), reproductive investment (the ratio of sexual to feeding zooids) and sex ratio (male to female zooids) in four genetically distinct clonal lines. There was a significant effect of clone on growth rate, reproductive investment and sex ratio, with clones showing contrasting responses to the various temperature and pH combinations. Overall, decreasing pH and increasing temperature caused reduction of growth, and eventual cessation of growth was often observed at the highest temperature, especially during the latter half of the 15-day trials. Reproductive investment increased with increasing temperature and decreasing pH, varying more widely with temperature at the lowest pH. The increased production of males, a general stress response of the bryozoan, was seen upon exposure to reduced pH, but was not expressed at the highest temperature tested, presumably due to the frequent cessation of growth. Further to the significant effect of pH on the measured whole-colony parameters, observation by scanning electron microscopy revealed surface pitting of the calcified exoskeleton in colonies that were exposed to increased acidity. Studying ecologically relevant processes of growth and reproduction, we demonstrate the existence of relevant levels of variation among genetic individuals which may enable future adaptation via non-mutational natural selection to falling pH and rising temperature.

Lawsuit seeks protections for 82 corals facing extinction; Global warming, ocean acidification top threats

The Center for Biological Diversity filed a notice of its intent to sue the National Marine Fisheries Service Tuesday for the agency’s failure to protect 82 imperiled coral species under the Endangered Species Act. These corals, all of which occur in U.S. waters ranging from Florida and Hawaii to U.S. territories in the Caribbean and Pacific, face numerous dangers, but global warming and ocean acidification are the overarching threats to their survival.

In 2009, the Center petitioned to protect 83 corals under the Act; the government found that listing might be warranted for all except one species. However, the government has failed to meet its deadline to determine whether listing is warranted and propose rules to protect these beleaguered corals. Tuesday’s 60-day notice is a prerequisite to filing suit.

“Time is of the essence to protect coral reefs, the world’s most endangered ecosystems,” said Miyoko Sakashita, oceans director at the Center. “Within a few decades, global warming and ocean acidification threaten to completely unravel magnificent coral reefs that took millions of years to build.”

Ocean acidification: ‘We’re down but not out’

Marine experts issued a rallying call on the first day of the SeaWeb’s International Seafood Summit 2011 in Vancouver, British Columbia, urging the global seafood industry and all other ocean stakeholders to avoid a defeatist attitude with ocean acidification and to instead pile pressure on scientists to provide solid data and advice on the potentially catastrophic problem, which could then be used to create concrete solutions.

Ocean acidification occurs when CO2 reacts with seawater to produce an acid; the faster the increase of CO2 in the atmosphere, the faster the acidification of the ocean.

Recent studies suggest the current uptake of CO2 by the surface waters of the ocean, and the resulting rate of ocean acidification, is about 100 times quicker than at the end of the last glacial 20,000 years ago, which was the last significant rise of CO2.

Super science postdoctoral fellowships available at the Australian Institute of Marine Science

The Australian Institute of Marine Science (AIMS) is the leading national organisation researching tropical marine ecosystems. The Institute has world-class laboratory facilities, two modern research vessels and extensive technical support. Facilities are being enhanced with $55M of capital funds from the Australian Government. This will include a state-of-the-art experimental ocean simulator in an extensive seawater precinct to support innovative research into coral spawning, water quality and climate change.

As part of the Australian Government’s Super Science Initiative (Marine and Climate), AIMS has received competitive funding from the Australian Research Council to support three exceptional early-career researchers. Successful applicants will conduct original research within a Project entitled ?A Changing Climate on the Great Barrier Reef: Present and Future Implications?, with a focus on the following topics: