http://www.commondreams.org/headline/2011/06/15-8

Published on Wednesday, June 15, 2011

by Doyle Rice

The “Dead Zone” in the Gulf of Mexico – a region of oxygen-depleted water off the Louisiana and Texas coasts that is harmful to sea life and the commercial fishing industry – is predicted to be the largest ever recorded this year, federal scientists announced Tuesday.

The majority of land in the Mississippi’s watershed is farm land (in green). Each spring, as farmers fertilize their land in preparation for crop season, rain washes fertilizer off the land and into streams, rivers, and then the Gulf of Mexico. This leads to a Dead Zone in the Gulf. (NOAA)

The majority of land in the Mississippi’s watershed is farm land (in green). Each spring, as farmers fertilize their land in preparation for crop season, rain washes fertilizer off the land and into streams, rivers, and then the Gulf of Mexico. This leads to a Dead Zone in the Gulf. (NOAA) The unusually large size of the zone is due to the extreme flooding of the Mississippi River this spring.

The Dead Zone occurs when there is not enough oxygen in the water to support marine life. Also known as “hypoxia,” it is created by nutrient runoff, mostly from over-application of fertilizer on agricultural fields. It flows into streams, then rivers and eventually the Gulf.

Forty-one percent of the contiguous USA drains into the Mississippi River and then out to the Gulf of Mexico. The majority of the land in Mississippi’s watershed is farm land.

Excess nutrients such as nitrogen can spur the growth of algae, and when the algae die, their decay consumes oxygen faster than it can be brought down from the surface, according to NOAA. As a result, fish, shrimp and crabs can suffocate, threatening the region’s commercial fishing industry.

Scientists say the area could measure between 8,500 and 9,421 square miles, or an area about the size of New Hampshire. If it does reach those levels, it would be the largest since mapping of the Gulf Dead Zone began in 1985.

The largest Dead Zone on record occurred in 2002 and encompassed more than 8,400 square miles. On average, the Dead Zone size is estimated to be 6,000 square miles.

http://www.commondreams.org/headline/2011/06/13-5

Published on Monday, June 13, 2011 by The Guardian/UK

by Tracy McVeigh

Global warming has long been blamed for the huge rise in the world’s jellyfish population. But new research suggests that they, in turn, may be worsening the problem by producing more carbon than the oceans can cope with.

Dr Carol Turley, a scientist at Plymouth University’s Marine Laboratory, said the research highlighted the growing problem of ocean acidification, the so-called “evil twin” of global warming. (Image: wiki commons) Research led by Rob Condon of the Virginia Institute of Marine Science in the US focuses on the effect that the increasing numbers of jellyfish are having on marine bateria, which play an important role by recycling nutrients created by decaying organisms back into the food web. The study, published in the journal Proceedings of the National Academy of Sciences, finds that while bacteria are capable of absorbing the constituent carbon, nitrogen, phosphorus and other chemicals given off by most fish when they die, they cannot do the same with jellyfish. The invertebrates, populating the seas in ever-increasing numbers, break down into biomass with especially high levels of carbon, which the bacteria cannot absorb well. Instead of using it to grow, the bacteria breathe it out as carbon dioxide. This means more of the gas is released into the atmosphere.

Dr Carol Turley, a scientist at Plymouth University’s Marine Laboratory, said the research highlighted the growing problem of ocean acidification, the so-called “evil twin” of global warming. “Oceans have been taking up 25% of the carbon dioxide that man has produced over the last 200 years, so it’s been acting as a buffer for climate change. When you add more carbon dioxide to sea water it becomes more acidic. And already that is happening at a rate that hasn’t occurred in 600 million years.”

The acidification of the oceans is already predicted to have such a corrosive effect that unprotected shellfish will dissolve by the middle of the century.”

Condon’s research also found that the spike in jellyfish numbers is also turning the marine food cycle on its head. The creatures devour huge quantities of plankton, thus depriving small fish of the food they need. “This restricts the transfer of energy up the food chain because jellyfish are not readily consumed by other predators,” said Condon.

The increase in the jellyfish population has been attributed to factors including climate change, over-fishing and the runoff of agricultural fertilisers. The rise in sea temperature and the elimination of predators such as sharks and tuna has made conditions ideal, and “blooms” – when populations explode in great swarms, sparking regular panics on beaches around the world– are being reported in ever-increasing size and frequency. Last year scientists at the University of British Columbia found that global warming was causing 2,000 different jellyfish species to appear earlier each year and expanding their number.

The proliferation of jellyfish has caused problems for seaside power and desalination plants in Japan, the Middle East and Africa. The blooms are also perilous to swimmers; the effects of a jellyfish sting range across the species from painless to tingling to agony and death.

The link to the original article is http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1122.html

by Katharina E. Fabricius, Chris Langdon, Sven Uthicke, Craig Humphrey, Sam Noonan, Glenn De’ath, Remy Okazaki, Nancy Muehllehner, Martin S. Glas & Janice M. Lough

Reference: Fabricius KE, Langdon C, Uthicke S, Humphrey C, Noonan S, De’ath G, Okazaki R, Muehllehner N, Glas M, Lough JM (2011) Losers and winners in coral reefs acclimatized to elevated carbon dioxide concentrations. Nature Climate Change 1: 165-169

Published online 29 May 2011

Experiments have shown that ocean acidification due to rising atmospheric carbon dioxide concentrations has deleterious effects on the performance of many marine organisms1, 2, 3, 4. However, few empirical or modelling studies have addressed the long-term consequences of ocean acidification for marine ecosystems5, 6, 7. Here we show that as pH declines from 8.1 to 7.8 (the change expected if atmospheric carbon dioxide concentrations increase from 390 to 750 ppm, consistent with some scenarios for the end of this century) some organisms benefit, but many more lose out. We investigated coral reefs, seagrasses and sediments that are acclimatized to low pH at three cool and shallow volcanic carbon dioxide seeps in Papua New Guinea. At reduced pH, we observed reductions in coral diversity, recruitment and abundances of structurally complex framework builders, and shifts in competitive interactions between taxa. However, coral cover remained constant between pH 8.1 and ~7.8, because massive Porites corals established dominance over structural corals, despite low rates of calcification. Reef development ceased below pH 7.7. Our empirical data from this unique field setting confirm model predictions that ocean acidification, together with temperature stress, will probably lead to severely reduced diversity, structural complexity and resilience of Indo-Pacific coral reefs within this century.

Affiliations

Australian Institute of Marine Science, PMB 3, Townsville, Queensland 4810, Australia
Katharina E. Fabricius,
Sven Uthicke,
Craig Humphrey,
Sam Noonan,
Glenn De’ath &
Janice M. Lough
University of Miami Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Florida 33149, USA
Chris Langdon,
Remy Okazaki &
Nancy Muehllehner
Max-Planck Institute for Marine Microbiology, Department of Biogeochemistry, Celsiusstr. 1, 28395 Bremen, Germany
Martin S. Glas

Contributions

All authors were involved with either fieldwork or data analyses. K.E.F. initiated and designed the study and wrote the manuscript, with contributions from all others. C.L. and R.O. analysed the seawater chemistry, C.H., S.N., K.E.F. and J.M.L. collected and analysed the Porites data, C.L. the in situ coral growth data, K.E.F. and S.N. the reef community data, S.U. the sediments and foraminifera, N.M. and S.U. the seagrass and epibiont data, and G.D. and K.E.F. conducted the statistical analyses.
Competing financial interests

The authors declare no competing financial interests.

Correspondence to: Katharina E. Fabricius

http://data.iucn.org/dbtw-wpd/edocs/Bios-Eco-Mar-Cor-027.pdf

by Kaufman L, Sandin S, Sala E, Obura D, Rohwer F, and Tschirky T (2011)
Coral Health Index (CHI): measuring coral community health.
Science and Knowledge Division, Conservation International, Arlington, VA, USA.

There is a new tool for assessing coral healthwhich has just been released by Conservation International (CI) and is available for download free on an IUCN website (International Union for the Conservation of Nature). I find it very easy to read and understand, and this appears to me to have widespread potential for applicability and use around the world to get a much better idea of how our reefs are doing. I can’t wait to try it out on reefs near me and see how they rate (I have a guess, but still it will be fascinating to see). Cheers, Doug Fenner

Special thanks to Doug Fenner, coral-list

http://www.bbc.co.uk/news/science-environment-13605113#story_continues_1

31 May 2011 Last updated at 19:47 ET

By Richard Black Environment correspondent, BBC News

Clownfish, the spectacular tropical species featured in the movie Finding Nemo, appear to lose their hearing in water slightly more acidic than normal.

At levels of acidity that may be common by the end of the century, the fish did not respond to the sounds of predators.

The oceans are becoming more acidic because they absorb much of the CO2 that humanity puts into the atmosphere.

Scientists write in the journal Biology Letters that failing to move away from danger would hurt the fish’s survival.

“Avoiding coral reefs during the day is very typical behaviour of fish in open water,” said research leader Steve Simpson from the School of Biological Sciences at the UK’s Bristol University.

“They do this by monitoring the sounds of animals on the reef, most of which are predators to something just a centimetre in length.

“But sounds are also important for mate detection, pack hunting, foraging – so if any or all of those capacities are gone, you’d have a very lost fish,” he told BBC News.

Previous research has shown that fish also lose their capacity to scent danger in slightly more acidic seawater.
Experimental chamber The fish were put in a “choice chamber” that allowed them to swim away, or not, on hearing the noise

The team raised baby clownfish in tanks containing water at different levels of acidity.

One resembled the seawater of today, with the atmosphere containing about 390 parts per million (ppm) of carbon dioxide.

The other tanks were set at levels that could be reached later this century – 600, 700 and 900 ppm.

The more CO2 there is in the atmosphere, the more the oceans absorb – and the more they absorb, the more acidic the water becomes.

In this experiment, the fish could decide whether to swim towards or away from an underwater loudspeaker replaying the sounds of predators recorded on a reef, with shrimps and fish that would take a small clownfish.

In water with today’s levels of CO2, the fish spent three-quarters of the time at the opposite end of the tube from the loudspeaker.

But at higher concentrations, they showed no preference. This suggests they could not hear, could not decipher or did not act on the warning signals.

“The reef has been described as ‘a wall of mouths’ waiting to receive the clownfish,” said Dr Simpson.
Continue reading the main story
ACIDIFYING OCEANS
Ocean pH levels (Image: BBC)

The oceans are thought to have absorbed about half of the extra CO2 put into the atmosphere in the industrial age
This has lowered its pH by 0.1
pH is the measure of acidity and alkalinity
Liquids lie between pH 0 (very acidic) and pH 14 (very alkaline); 7 is neutral
Seawater is mildly alkaline with a “natural” pH of about 8.2
The IPCC forecasts that ocean pH will fall by “between 0.14 and 0.35 units over the 21st Century, adding to the present decrease of 0.1 units since pre-industrial times”

“What we have done here is put today’s fish in tomorrow’s environment, and the effects are potentially devastating.”

If it takes several decades for the oceans to reach these more acidic levels, there is a chance, the team says, that fish could adapt.

Whether that can happen is one of the outstanding questions from this research. Another is whether other species are similarly affected.

A third question is why the fish are affected by these slight changes in acidity.

There appears to be no physical damage to their ears; the team suggests there could be some effect on nerves, or maybe they are stressed by the higher acidity and do not behave as they otherwise would.

Further experiments are in train that may answer those questions.

Concern about ocean acidification has arisen considerably more recently than alarm over global warming; but already there is ample evidence that it could bring significant changes to ocean life.

The organisms most directly affected appear to be corals and those that make shells, such as snails.

Just this weekend, another team of researchers published findings from a “natural laboratory” in the seas off Papua New Guinea, where carbon dioxide bubbles into the water from the slopes of a dormant volcano.

This local acidity is too much for most corals; instead, an alternative ecosystem based on seagrasses thrives.

With carbon emissions continuing to rise, researchers predicted most reefs around the world would be in serious trouble before the end of the century.
More on This Story
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Fish ‘at risk’ in acidified ocean 21 NOVEMBER 2009, SCI/TECH
Bubbling sea signals coral threat 29 MAY 2011, SCIENCE & ENVIRONMENT
Coral reefs heading into crisis 23 FEBRUARY 2011, SCIENCE & ENVIRONMENT
Recipe for rescuing our reefs 05 NOVEMBER 2008, SCI/TECH

Special thanks to Doug Fenner, Coral-list.