Tag Archives: Marine

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Acid oceans threaten billion-dollar oyster business

FOR IMMEDIATE RELEASE Scientists have identified the problem that commercial hatcheries must overcome to keep baby oysters alive in increasingly acid seas − but wild oysters are still under threat LONDON, 22 June − Bad news for American gourmets: the commercial oyster industry in the Pacific Northwest has been failing for several years, and may go on failing as increasingly acid oceans put the larvae of the bivalve Crassostrea gigas seriously at risk. The good news is that US scientists now know exactly why things are going wrong in the oyster beds, which opens up the possibility of commercial hatcheries finding ways to get round the problem. First, the facts: as carbon dioxide levels in the atmosphere rise inexorably, so the gas dissolves in water and falls as a very weak carbonic acid rain, with a subtle but measurable change in the pH values of the planet’s oceans. There have always been dissolved gases in rainwater, but as long as pH levels remain stable, the ocean’s corals and molluscs not only adapt, they subtly exploit the water chemistry to build stronger bones and shells.

Sensitive to change

Oysters seem unusually sensitive to changes in pH, but marine biologist George Waldbusser and research colleagues at Oregon State University report in Geophysical Research Letters that the failure of the oyster harvest isn’t a simple case of acid waters dissolving calcium carbonate shells. Instead, water high in dissolved carbon dioxide tends to alter the shell formation rates, the energy usage and, ultimately, the growth and survival of young oysters. Females tend to produce eggs by the million as water temperatures reach around 20°C. Once fertilised and hatched, the embryos have about two days to start building a shell. Raised carbon dioxide levels in the water impose an extra energy cost for the little shell-builders. Mature oysters can take their time and assemble calcium carbonate production more slowly, but larvae don’t have the time. Their only energy supply is the nourishment in the egg. “From the time eggs are fertilised, Pacific oyster larvae precipitate roughly 90% of their bodyweight as calcium carbonate shell within 48 hours,” Dr Waldbusser says. “They must build their first shell quickly on a limited amount of energy – and, along with the shell, comes the organ to capture external food.

Death race

“It becomes a death race of sorts. Can the oyster build its shell quickly enough to allow its feeding mechanism to develop before it runs out of energy from the egg?” Armed with this insight into oyster bed ecology, the scientists say, there are interventions that can be introduced at hatcheries that may offset some of the effects of ocean acidification. Some hatcheries have started to “buffer” the water supplies in commercial hatcheries that supply the marine and estuary oyster beds − essentially, adding antacids to incoming waters. However, what may be hopeful news for fish farmers may not be such good news for the wild oyster, which will no doubt experience more stress in its native waters as carbon dioxide levels go on rising. The research matters at one level because Pacific oyster farming is now a billion-dollar business, and at another because it exposes something of the intricate connection between sea-dwelling creatures and the chemistry of the sea. It is also a reminder that any creature faces different hazards at every stage of its life cycle. The report’s authors say: “We suggest that the predictions of winners and losers in a high CO² world may be better informed by calcium carbonate kinetics, bioenergetics, ontogeny, and life-history characteristics than by shell mineralogy alone.” − Climate News Network  

FOR IMMEDIATE RELEASE Scientists have identified the problem that commercial hatcheries must overcome to keep baby oysters alive in increasingly acid seas − but wild oysters are still under threat LONDON, 22 June − Bad news for American gourmets: the commercial oyster industry in the Pacific Northwest has been failing for several years, and may go on failing as increasingly acid oceans put the larvae of the bivalve Crassostrea gigas seriously at risk. The good news is that US scientists now know exactly why things are going wrong in the oyster beds, which opens up the possibility of commercial hatcheries finding ways to get round the problem. First, the facts: as carbon dioxide levels in the atmosphere rise inexorably, so the gas dissolves in water and falls as a very weak carbonic acid rain, with a subtle but measurable change in the pH values of the planet’s oceans. There have always been dissolved gases in rainwater, but as long as pH levels remain stable, the ocean’s corals and molluscs not only adapt, they subtly exploit the water chemistry to build stronger bones and shells.

Sensitive to change

Oysters seem unusually sensitive to changes in pH, but marine biologist George Waldbusser and research colleagues at Oregon State University report in Geophysical Research Letters that the failure of the oyster harvest isn’t a simple case of acid waters dissolving calcium carbonate shells. Instead, water high in dissolved carbon dioxide tends to alter the shell formation rates, the energy usage and, ultimately, the growth and survival of young oysters. Females tend to produce eggs by the million as water temperatures reach around 20°C. Once fertilised and hatched, the embryos have about two days to start building a shell. Raised carbon dioxide levels in the water impose an extra energy cost for the little shell-builders. Mature oysters can take their time and assemble calcium carbonate production more slowly, but larvae don’t have the time. Their only energy supply is the nourishment in the egg. “From the time eggs are fertilised, Pacific oyster larvae precipitate roughly 90% of their bodyweight as calcium carbonate shell within 48 hours,” Dr Waldbusser says. “They must build their first shell quickly on a limited amount of energy – and, along with the shell, comes the organ to capture external food.

Death race

“It becomes a death race of sorts. Can the oyster build its shell quickly enough to allow its feeding mechanism to develop before it runs out of energy from the egg?” Armed with this insight into oyster bed ecology, the scientists say, there are interventions that can be introduced at hatcheries that may offset some of the effects of ocean acidification. Some hatcheries have started to “buffer” the water supplies in commercial hatcheries that supply the marine and estuary oyster beds − essentially, adding antacids to incoming waters. However, what may be hopeful news for fish farmers may not be such good news for the wild oyster, which will no doubt experience more stress in its native waters as carbon dioxide levels go on rising. The research matters at one level because Pacific oyster farming is now a billion-dollar business, and at another because it exposes something of the intricate connection between sea-dwelling creatures and the chemistry of the sea. It is also a reminder that any creature faces different hazards at every stage of its life cycle. The report’s authors say: “We suggest that the predictions of winners and losers in a high CO² world may be better informed by calcium carbonate kinetics, bioenergetics, ontogeny, and life-history characteristics than by shell mineralogy alone.” − Climate News Network  

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Coral fights back slowly from ocean heating

EMBARGOED until 2301 GMT on Thursday 6 June The good news is that some coral can recover from periodic warming of the oceans: the bad news is it might take too long. LONDON, 6 June – Marine biologists’ worst fears seem to be confirmed: coral colonies take a long time to recover from catastrophic climate events. British and Brazilian biologists report in the Public Library of Science One – better known simply as PLoS One – that the richest habitats of the sea could also be among the most vulnerable to climate change. For more than 17 years, conservationists from Plymouth University in the UK worked with researchers from the Federal University of Bahia in Brazil to analyse the diversity and density of coral reefs and colonies off the coast of South America. Quite early in that 17 year span, there was an  El Niño event. This is a periodic eruption of unprecedented ocean temperatures: it is a natural phenomenon and seems to have happened periodically through recorded human history, distinguished by droughts and wildfires in those places that normally expect high rainfall, and floods on otherwise normally arid coasts. Rising temperatures The 1997-98 event lasted for 18 months and was considered one of the most devastating of all, with sea temperatures reaching a global record. Tropical coral reefs were affected almost everywhere; there were also devastating storms and floods in California and forest fires in Borneo. Corals are peculiarly sensitive to sea temperatures – they tend to bleach if seas get hotter – and many corals live and flourish at near the limits of their tolerance. Coral reefs are also home to an estimated 25% of all marine species, so the loss of a reef has a serious effect on marine biodiversity, as well as on the incomes of local fishermen – and local tourist operators. The British and Brazilian scientists monitored eight species of Scleractinian or stony corals and worked with the Brazilian Meteorological Office to build up a complete picture of the environmental conditions and the way these affected species behavior. Slow recovery During 1998, all the monitored corals showed increased mortality and one species disappeared completely from the reefs for at least seven years. Then, as temperatures dropped, the corals started to grow again. Recent measurements show that the coral colonies have fully recovered, and are now back to the levels recorded before 1998. That’s the good news. The bad news is that recovery took so long. “El Niño events give us an indication of how changing climate affects ecosystems as major changes within the Pacific impact the whole world,” said one of the authors, Martin Attrill of Plymouth’s Marine Institute. “If the reefs can recover quickly, it is probable they can adapt and survive the likely changes in water temperatures ahead of us. However, we found it took 13 years for the coral reef system of Brazil to recover, suggesting they may be very vulnerable to climate-related impacts.” – Climate News Network

EMBARGOED until 2301 GMT on Thursday 6 June The good news is that some coral can recover from periodic warming of the oceans: the bad news is it might take too long. LONDON, 6 June – Marine biologists’ worst fears seem to be confirmed: coral colonies take a long time to recover from catastrophic climate events. British and Brazilian biologists report in the Public Library of Science One – better known simply as PLoS One – that the richest habitats of the sea could also be among the most vulnerable to climate change. For more than 17 years, conservationists from Plymouth University in the UK worked with researchers from the Federal University of Bahia in Brazil to analyse the diversity and density of coral reefs and colonies off the coast of South America. Quite early in that 17 year span, there was an  El Niño event. This is a periodic eruption of unprecedented ocean temperatures: it is a natural phenomenon and seems to have happened periodically through recorded human history, distinguished by droughts and wildfires in those places that normally expect high rainfall, and floods on otherwise normally arid coasts. Rising temperatures The 1997-98 event lasted for 18 months and was considered one of the most devastating of all, with sea temperatures reaching a global record. Tropical coral reefs were affected almost everywhere; there were also devastating storms and floods in California and forest fires in Borneo. Corals are peculiarly sensitive to sea temperatures – they tend to bleach if seas get hotter – and many corals live and flourish at near the limits of their tolerance. Coral reefs are also home to an estimated 25% of all marine species, so the loss of a reef has a serious effect on marine biodiversity, as well as on the incomes of local fishermen – and local tourist operators. The British and Brazilian scientists monitored eight species of Scleractinian or stony corals and worked with the Brazilian Meteorological Office to build up a complete picture of the environmental conditions and the way these affected species behavior. Slow recovery During 1998, all the monitored corals showed increased mortality and one species disappeared completely from the reefs for at least seven years. Then, as temperatures dropped, the corals started to grow again. Recent measurements show that the coral colonies have fully recovered, and are now back to the levels recorded before 1998. That’s the good news. The bad news is that recovery took so long. “El Niño events give us an indication of how changing climate affects ecosystems as major changes within the Pacific impact the whole world,” said one of the authors, Martin Attrill of Plymouth’s Marine Institute. “If the reefs can recover quickly, it is probable they can adapt and survive the likely changes in water temperatures ahead of us. However, we found it took 13 years for the coral reef system of Brazil to recover, suggesting they may be very vulnerable to climate-related impacts.” – Climate News Network