Ocean acidification

The oceans are becoming more acidic because of the rapid release of carbon dioxide (CO₂) caused by anthropogenic (human) activities, such as burning of fossil fuels. So far, the oceans have taken up around 30% of all anthropogenic CO₂ released to the atmosphere. The continuous increase of CO₂ has a substantial effect on ocean chemistry because CO₂ reacts with water and carbonate molecules. This process, called ‘ocean acidification,’ lowers pH, and calcium carbonate becomes less available. This is a problem for calcifying organisms, such as corals and molluscs, that use calcium carbonate as the main building blocks of their exoskeleton.

In particular, organisms that build their shells from a type of calcium carbonate known as ‘aragonite’ are in trouble because aragonite is extremely soluble in sea water. Sea butterflies, tiny, swimming sea snails, build their shells of aragonite. Therefore, they are also known as ‘the canaries of the coalmine’ because they are expected to be amongst the first organisms to be affected by ocean acidification.

Team will assess vulnerability of aquaculture and restoration efforts in Chesapeake Bay

The excess carbon dioxide responsible for global warming also increases the acidity of seawater, challenging the growth and survival of oysters and other shellfish. A team led by researchers at William & Mary’s Virginia Institute of Marine Science is now helping oyster growers and restoration specialists better manage their future responses to acidification in the Chesapeake Bay.

The team, funded by the NOAA Ocean Acidification Program, is led by VIMS researchers Marjy Friedrichs and Emily Rivest, along with David Wrathall of Oregon State University. Other team members include Mark Brush, Pierre St-Laurent, and Karen Hudson of VIMS, Aaron Bever of Anchor QEA, and Bruce Vogt of NOAA’s Chesapeake Bay Office. The team calls their project STAR, for Shellfish Thresholds and Aquaculture Resilience.

“Coastal acidification and its associated co-stressors present a serious and credible threat to the success of both oyster aquaculture and oyster restoration in the Bay,” says Friedrichs. The co-stressors include nutrient pollution, warmer Bay waters, and pulses of freshwater from rainstorms made more intense by global atmospheric changes. Previous research has shown these factors can intensify the negative impacts caused by ocean acidification alone.

Rising ocean temperatures and ocean acidification could have negative cumulative effects that slow the growth of tropical coral reefs, according to a UCLA-led study published in early January.

The study examined the growth of two types of tropical corals – commonly known as cauliflower coral and hood coral – at different water temperatures and acidities. At a lower temperature, the corals were able to compensate for the acidification and continue building their skeletons. But at a higher temperature, the corals grew much slower.

In order for coral reefs to survive despite constant degradation by waves and human activity, individual reef-building corals must be able to efficiently build their skeletons through a process called calcification, said Maxence Guillermic, a UCLA postdoctoral researcher and lead author of the study. The coral must maintain the correct internal carbonate conditions to allow the skeletal building material, calcium carbonate, to precipitate, he added.

Researchers from the University of Tsukuba find that in the presence of ocean acidification, feedback loops keep degraded turf algal states stabilized, inhibiting the recruitment of coral and other algae.

Tsukuba, Japan—It’s tough out there in the sea, as the widespread loss of complex marine communities is testament to. Researchers from Japan have discovered that ocean acidification favors degraded turf algal systems over corals and other algae, thanks to the help of feedback loops.

In a study published this month in Communications Biology, researchers from the University of Tsukuba have revealed that ocean acidification and feedback loops stabilize degraded turf algal systems, limiting the recruitment of coral and other algae.

A NCCOS and NOAA Ocean Acidification Program sponsored study investigated how physical properties such as winds, tides, and currents impact estuarine acidification and carbonate chemistry in the Chesapeake Bay estuary, a complex and little studied undertaking. A coupled hydrodynamic-carbonate chemistry model was used to understand the wind-driven variability in the estuarine carbonate system. Large temporal pH fluctuations and low pH events were documented that could negatively impact acidification-sensitive species such as oysters.

A major challenge in the study of estuarine acidification is the strong temporal and spatial variability of carbonate chemistry resulting from a wide array of physical forces such as winds, tides and river flows. Most studies of estuarine carbonate system dynamics have been limited to the along-channel direction, while lateral pH dynamics (e.g., channel to shore) has received less attention.

Addressing the growing problem of ocean acidification in New England waters before it severely damages the region’s crucial shellfish industry is the focus of an important report by a commission of Massachusetts legislators, state environmental agencies, marine research and conservation organizations, and shellfish industry leaders. Woods Hole Oceanographic Institution (WHOI) is a part of the 18-member Massachusetts Special Legislative Commission on Ocean Acidification and helped co-author the 84-page report released today.

Under increasing global warming, tropical fish are escaping warmer seas by extending their habitat ranges towards more temperate waters.

But a new study from the University of Adelaide, published in Nature Climate Change, shows that the ocean acidification predicted under continuing high CO₂ emissions may make cooler, temperate waters less welcoming.

“Every summer hundreds of tropical fish species extend their range to cooler and temperate regions as the waters of their natural habitat become a little too warm for comfort,” says lead author Ericka Coni, Ph.D. student in the University’s School of Biological Sciences. “For at least two decades, Australian temperate reefs have been receiving new guests from the tropics.

A team of researchers from the University of Maine Darling Marine Center in Walpole, Bigelow Laboratory for Ocean Sciences in East Boothbay and Maine Department of Marine Resources in West Boothbay Harbor recently published their research on the effects of ocean warming and acidification on gene expression in the earliest life stages of the American lobster.

The work was published in the scientific journal Ecology and Evolution with collaborators from the University of Prince Edward Island and Dalhousie University in Canada.

Leading the study was recent UMaine graduate student Maura Niemisto, who received her master’s degree in marine science. Co-authors on the journal article were her advisers Richard Wahle, research professor in UMaine’s School of Marine Sciences and director of the Lobster Institute, and David Fields, senior research scientist at Bigelow Laboratory for Ocean Sciences. 

World-leading experts in ocean acidification and warming monitored the effect differing ocean acidification had on different forms of algae

Making meaningful reductions in CO² emissions could help marine life damaged by increasingly acidified oceans to recover, according to new research.

An international team of scientists – world-leading experts in ocean acidification and warming from the University of Plymouth and the Shimoda Marine Research Center at the University of Tsukuba – placed a series of artificial tiles on the ocean floor off the coast of Japan.

Research from the University of Adelaide has found that some species of fish will have higher reproductive capacity because of larger sex organs, under the more acidic oceans of the future.

Published in PLOS Biology, the researchers say that far from the negative effects expected under the elevated CO₂  levels in our oceans predicted for the end of the century, these fish capitalise on changes to the underwater ecosystems to produce more sperm and eggs. They also look after them better, enhancing the chances of reproductive success.

“The warming oceans absorb about one-third of the additional CO₂ being released into the atmosphere from carbon emissions, causing the oceans to acidify,” says lead author Professor Ivan Nagelkerken from the University’s Environment Institute and Southern Seas Ecology Laboratories.

“We know that many species are negatively affected in their behaviour and physiology by ocean acidification. But we found that in this species of temperate fish – the common triplefin – both males and females had larger gonads under conditions of ocean acidification. This meant increased egg and sperm production and therefore more offspring.”