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Ocean life support dwindling

Phytoplankton, which are responsible for half of the world's primary production and are the basis of all marine ecosystems, have been declining for more than 100 years, perhaps the result of rising sea temperatures, according to a study published in this week's Nature -- a cause for concern about the health of the Earth's oceans. A number of marine diatom cells, animportant group of phytoplankton in the oceans.Image: Harry Taylor,courtesy of Nikon Small world"It is troubling," said marine scien

By | July 28, 2010

Phytoplankton, which are responsible for half of the world's primary production and are the basis of all marine ecosystems, have been declining for more than 100 years, perhaps the result of rising sea temperatures, according to a study published in this week's Nature -- a cause for concern about the health of the Earth's oceans.
A number of marine diatom cells, an
important group of phytoplankton in the oceans.

Image: Harry Taylor,
courtesy of Nikon Small world
"It is troubling," said marine scientist linkurl:David Siegel;http://www.geog.ucsb.edu/people/faculty/david-siegel.html of the University of California, Santa Barbara, who was not involved in the research. With data dating back to the late 1800s, "this paper finds a long-term trend that's huge," he said. "The phytoplankton community has undoubtedly been changing." Phytoplankton productivity lies at the base of the marine food web, supporting all ocean life and contributing to global geochemical processes, including the carbon cycle. Through photosynthetic activities, phytoplankton reduce atmospheric carbon dioxide. Satellite data from the last few decades has suggested that phytoplankton might be on the decline. To determine whether these apparent declines are indicative of a longer-term trend, marine biologist linkurl:Boris Worm;http://wormlab.biology.dal.ca/ of Dalhousie University in Canada and his colleagues turned to data from a variety of sources, including direct measurements of chlorophyll levels, a pigment found in all phytoplankton, and Secchi disk data. Secchi disks are a simple yet fundamental tool in oceanography, and are used to measure water transparency, which can serve as a proxy for phytoplankton abundance. Compiling and standardizing these data, dating back to 1899, the researchers found a consistent and significant decline in phytoplankton in eight of the world's 10 oceans -- an estimated 1 percent per year globally. The decline was strongly correlated with the rising surface sea temperatures. "One percent per year is a huge number," said Siegel, who wrote an accompanying News and Views article. The impacts of such a decline are significant, agreed aquatic microbiologist linkurl:Hugo Sarmento;http://www.icm.csic.es/bio/projects/icmicrobis/fitxes/Personal_webs/Sarmento/ of the Institute of Marine Sciences in Barcelona, Spain, who did not participate in the study. "The balance in the ocean is based on photosynthesis of phytoplankton and respiration of the bacteria, so the balance of the CO2 [and] oxygen in the water [might shift]." This could be bad news for ocean acidification, which will increase with higher CO2 levels, as well as the rising levels of atmospheric CO2, he said. "[If] the water [becomes] saturated with CO2, the sea could stop being a receptor of CO2 from the atmosphere and actually become an emission source, [which] could actually increase the effects of climate change." One caveat, Worm noted, is that the measures of water transparency and chlorophyll levels are merely proxies for phytoplankton abundance. "We can confidently say that phytoplankton has declined over the last 100 years," he said, "but the exact magnitude of the decline and what this means for ocean life, we need to do more work on." If phytoplankton is indeed declining at the estimated 1 percent per year, "it would be a very concerning aspect of global change in the ocean."
Harry Taylor, Nikon Small World, National Library of Australia, NASA Earth Observatory Collection, Jack Polanen, Oceans Below underwater production & training.
Another paper co-authored by Worm, also published online today in Nature, points to another disturbing trend occurring among marine life -- a shift in biodiversity as a result of temperature. While this study did not look at changes in biodiversity over time, it found a highly significant relationship between species richness and temperature across the world's marine habitats, suggesting that as the oceans warm, "there will be a reorganization of biodiversity in response to changing temperatures," said co-author linkurl:Derek Tittensor,;http://www.mathstat.dal.ca/%7Ederekt/research.html a marine ecologist at Dalhousie University. Furthermore, the trend was found across all organisms the researchers looked at, from corals to whales. "[It] is really quite remarkable that [the trend was] so consistent," Worm said. "I think what it means is the ocean of the future will look different." D.G. Boyce, et al., "Global phytoplankton decline over the past century," Nature, 466:591-5, 2010. D.P. Tittensor, et al., "Global patterns and predictors of marine biodiversity across taxa," Nature, DOI:10.1038, 2010. Editor's note: The video was added to this article on July 29, 2010.
**__Related stories:__***linkurl:Oil spill is boon to bacteria;http://www.the-scientist.com/blog/display/57448/
[25th May 2010]*linkurl:A microbe's surprising defense;http://www.the-scientist.com/blog/display/55060/
[29th September 2008]*linkurl:Ocean global warming tool sinks;http://www.the-scientist.com/blog/display/54303/
[14th February 2008]

Comments

Avatar of: anonymous poster

anonymous poster

Posts: 1

July 28, 2010

One percent per year for over 100 years would mean that they are all gone if one is using simple math.\n\nUnless people can do the compound calculation in their heads, a cumulative number might be more informative.
Avatar of: anonymous poster

anonymous poster

Posts: 15

July 28, 2010

The solution may be as simple as engineering phyoplankton as one has engineered bacteria. If phytoplankton can be cultured in large scale bioreactors, they could be used to "seed" the oceans with an invigorated supply of these beneficial organisms. So get to it you molecular biologists and cell biologists and stop all the unneccesary duplicated research effort to sustain your careers, grants and publication base. Do something beneficial that all human kind find laudable.
Avatar of: Alex Tolley

Alex Tolley

Posts: 2

July 28, 2010

Suggesting it is due to rising temperatures is premature. This is using two different pieces of data, the first time series in, I trust, the same oceans, the second a comparison across different temperature regimes.\n\nIn the first case, since temperatures are rising over the whole study, temperature is just a coincident variable. There are other variables, for example, pollutants that might be the cause. In the second case, it is not clear that higher surface temperatures are not found in areas of different characteristics. For example, Antarctic waters are cold but associated with deep water upwelling of nutrients, whilst tropical waters are relatively nutrient poor.\n\nThis article does not indicate how or whether these variables have been accounted for.\n\n
Avatar of: Ted Howard

Ted Howard

Posts: 2

July 28, 2010

The compound math is 37% after 100 years of 1% per annum reduction.\n\nMany of the premises don't make much sense to me.\nTemperature is likely to be one factor, yet temperature varies considerably on geological and evolutionary timescales, as does sea level, and just about everything else.\n\nEvolution is constantly reaching new equilibria in response to the many changes that happen, and all of those equilibria are dynamic rather than static, and some with very long period oscillations.\n\nI would be looking for rate limiting trace element concentrations. ALl processes have a single rate limiting step in any particular set of circumstances (environmental variables). These may (will) vary from set to set of environmental variables, and it strikes me that humanity extracting billions of tonnes of top level predators (tuna, sharks, and all the other species we take) must be having a wide range of impacts.\n\nSome of those impacts are likely to be on nutrient levels, particularly in central oceans where the tunas now swim in vastly reduced numbers (and therefore carry far less nutrient between systems).\n\nI don't know what those numbers are, but as an ex commercial fisherman of 17 years experience, and a trained marine ecologist, I would love to see some real research on those numbers.\n\nI suspect, that if we insert appropriate levels of trace nutrients at appropriate locations, we would see vastly increased productivity.\n\nI also suspect that the use of management (and market) tools such as minimum legal size are altering the genetic composition of many target species, and breeding for smaller slower growing fish.\n\nAlso need to factor in reduced insolation due to jet aircraft contrails and a host of other things, giving a very complex situation indeed.\nA very complex situation.
Avatar of: anonymous poster

anonymous poster

Posts: 3

July 29, 2010

I recall recently seeing some research which suggests whales may be a critical element in the phytoplankton decline. \n\nThose that feed on krill and such are at a position in the food web where they are getting a lot of bioconcentrated iron in their diet. It gets excreted in their feces, which has the effect of slowly releasing it back into the ocean where iron is a limiting factor for phytoplankton growth, if I recall the report correctly. Less whale-poop, less plankton.\n\nThe decline in whale populations may correlate with the decline in phtoplankton levels. This doesn't rule out temperature as a factor, but it's worth factoring in to the research to see how significant an oceanic whale-poop deficit might be.
Avatar of: Mervyn Vogt

Mervyn Vogt

Posts: 4

July 29, 2010

The attribution solely to temperature gives me some concern. There are other factors which are in operation. I would draw attention to the fact that 100 years ago, in 1910, we had the first of the big oil spills. In 1968 we had the first supertanker, the Torrey Canyon go down in the North Sea, at that time a world leading oxygen expert, the late LLoyd Berkner warned that it would only take a few major ocean disasters at the wrong place and the wrong time to precipitate a massive decline in diatoms and other marine life which could cause a serious problem for world oxygen levels.\nMervyn K. Vogt

July 29, 2010

..apart from the natural forms of increasing the temperature, I wonder about the contribution of artificial forms: for egs: deep-water submarines-sonic waves et cetera..\nsuresh radhakrishnan.
Avatar of: Brian Jones

Brian Jones

Posts: 5

July 30, 2010

One of the problems is that plankton does not exist in isolation. Over the last 100 years a massive tonnage of protein (and energy) has been removed from the system through fishing. But conversely the continual harvest of fish (especially planktivorous fish such as anchovies and pilchards) does not indicate that ocean productivity has fallen 50% over the last 50 years. We have records for their production going back over 500 years, its very cyclical but does not support a decline. Good story, bad science.
Avatar of: anonymous poster

anonymous poster

Posts: 3

July 30, 2010

Here's links to a couple of articles:\n\nhttp://wattsupwiththat.com/2010/06/16/whale-poop-fights-global-warming/\n\nhttp://www3.interscience.wiley.com/journal/123336520/abstract?CRETRY=1&SRETRY=0
Avatar of: David Hill

David Hill

Posts: 41

July 31, 2010

The quantity of photosynthetic nannoplankton also has to be taken into account. These are not as easy to assay as phytoplankton, but the bacteria may be far more important to primary production. The diversity of bacteria in the ocean has only been studied recently, through the collection of DNA sequences, as these organisms have been difficult to collect, culture, and characterize.
Avatar of: anonymous poster

anonymous poster

Posts: 20

August 2, 2010

I'm not sure if there is a lipid component to plankton, but for fish, the dispersants probably act like detergents, removing the protective mucus on the scales and gills. Thus if the fish are not killed by the oil, they might be by the dispersant. Seems we're adding a rock to a hard place.

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