Climate change will affect the distribution and diversity of marine organisms

Climate change will force marine organisms towards the poles, but would they be safe there? 

Human activities such as emissions from the use of fossil fuels, rampant urbanisation, deforestation, and modern agricultural practices, are all altering the earth’s climate in an unprecedented scale. Climate change not only occurs in the land, but also in water bodies. Studies have indicated that since the 1950s, the amount of heat stored in the ocean (ocean heat) has increased considerably. Besides, ocean temperatures have increased throughout the world since the advent of the twentieth century, with the past three decades recording the highest temperatures since the measurements began.

 A major consequence of increase in ocean temperatures is the corresponding decrease in dissolved oxygen levels. This phenomenon is predicted to significantly disturb marine ecosystems. Recent research by a group of American and German scientists revealed the consequences of oceanic climate change on a range of fish and crustacean species in the North Atlantic with different levels of tolerance towards heat and oxygen levels. The researchers'  climate models predict substantial warming and deoxygenation throughout most of the upper ocean by the end of this century which in turn will affect the distribution  of marine  creatures. Their studies reveal that warming of water and oxygen depletion would force the organisms to migrate towards the pole due to deficiency of the original native waters to sustain their energy requirements. The scientists predict that even the waters towards the pole would have reduced oxygen levels, meaning the survival of the migrants could be precarious even there. Furthermore, this movement could alter the ecosystems in the polar waters due to many factors including competition from the migrants which may alter species ecologies.

References

http://www.sciencemag.org/content/348/6239/1132.abstract

Deutsch C, Ferrel A, Seibel B, Pörtner HO, & Huey RB (2015). Ecophysiology. Climate change tightens a metabolic constraint on marine habitats. Science (New York, N.Y.), 348 (6239), 1132-5 PMID: 26045435

Addendum: Plastiki

Plastiki’s epic voyage, which commenced on March 20th at San Francisco, concluded at Sydney Harbour on 26th July 2010. As mentioned in my post, the journey has highlighted the plastic problem (as exemplified by the Great Pacific Garbage Patch) and the increasing pollution of the ocean.

Where did the oil go?

The recent oil spill in the Gulf of Mexico released, as we have all seen on tv, a lot of oil. Quite how much is a "lot" is a bit of a guess, but roughly 4.9 million barrels, or 784 million litres*. What actually happened to this oil was reviewed recently in an article in Science (Kerr 2010). Only about 0.1% was recovered from beaches and marshes (that´s still an awful lot of oil!). About 17% was siphoned away at the well head, 5% burned off at the surface, and only 3% skimmed off by booms, despite a lot of effort and money spent. And the other 75%? It's, er, disappeared.

So where did this oil go? Some evaporated, but with luck most of it was eaten.

Oil is energy, that's why we use it in our cars and power stations. And energy means food. There are actually quite a few bacteria that digest and breakdown crude oil, and these are massively important in the recovery of the ocean from disasters like this. They work as a consortium, each concentrating on a particular fraction of the oil, and as one hydrocarbon is degraded to another, other bacteria take over. The first, and so in many ways the most important, are Alcanivorax species (Vila et al 2010). These are found in tiny quantities in unpolluted waters, but their numbers rocket when in the presence of linear and branched alkanes, common in crude oil. In fact they are so specialised for this type of hydrocarbon that without long chain alkenes they grow very poorly, but by then their job is done. Now other species such as Roseovarius and Marinobacter take over.

This breakdown was helped by the massive release of chemical dispersants at the oil head, 1.1 million gallons (Kintisch 2010). These are similar to the detergent in your kitchen, breaking down lumps of oil into tiny droplets, which are "dispersed" and can be attacked much more efficiently by bacteria. This was very controversial, as dispersants are pretty toxic and an immense quantity was involved. Still, it seemed to work, and much of the oil was broken down into 1-10 micrometer droplets. In fact, it started to raise fears that it was working TOO well, a microbial explosion depriving the ocean floor of oxygen and creating a huge dead zone. But this seems not to have happened, and in fact so far the prognosis is good.

We´re not out of the woods yet, the oil could yet turn up in unwanted places, and chemical damage by detergents might yet, for instance, devastate the local tuna population. But there have been lessons learnt for next time - and there will be a next time.

Kerr RA (2010). Gulf Oil Spill. A lot of oil on the loose, not so much to be found. Science (New York, N.Y.), 329 (5993), 734-5 PMID: 20705818
http://www.sciencemag.org/cgi/content/full/sci;329/5993/734?maxtoshow=&hits=10&RESULTFORMAT=&fulltext=oil+biodegradation&searchid=1&FIRSTINDEX=0&sortspec=date&resourcetype=HWCIT

Kintisch E (2010). Gulf Oil Spill. An audacious decision in crisis gets cautious praise. Science (New York, N.Y.), 329 (5993), 735-6 PMID: 20705819
http://www.sciencemag.org/cgi/content/full/329/5993/735

Vila, J., Nieto, J., Mertens, J., Springael, D., & Grifoll, M. (2010). Microbial community structure of a heavy fuel oil-degrading marine consortium: linking microbial dynamics with polycyclic aromatic hydrocarbon utilization FEMS Microbiology Ecology DOI: 10.1111/j.1574-6941.2010.00902.x

* the oil "barrel" is actually based on a type of old English wine barrel or "teirce" holding 35 gallons.

Sunlight on the sea

In this last week the Brazilian cities of Sao Paulo and Recife have experienced records levels of UV exposure. While a UV index of 6-7 is ¨high risk", and "very high risk" is 8-10, Sao Paulo was scorched with an index of 14.

As the sun burns us it also beats down on the ocean surface and the algae that live there. What happens next is the subject of the CLAW hypothesis, which proposes a negative feedback loop, as follows.....

Dimethylsulphide produced by phytoplankton is oxidised by bacteria to produce a sulphate aerosol on the sea surface which is a major source of cloud condensation nuclei. So more clouds, less photosynthesis and a feedback loop.

That´s fine, but of course the real world is much more complicated than that. For instance, solar radiation is a double edged sword. There is increased photosynthesis, and temperature for growth, but what of UV? UV-B damages DNA in the bacteria required for DMS oxidation, killing them. It also harms the phytoplankton, who respond by producing anti-oxidants, including DMS. Together these factors increase considerably the amount of DMS in the ocean, so oceanic [DMS] and levels of UV are linked through the year. But DMS in the atmosphere and the surface waters is attacked by UV, leading to it´s photo destruction.

So what happens when UV increases beyond previous levels? Does the extra production of DMS still lead to more cloud cover, a negative feedback? Or does UV kill off the oxidising bacteria and cause photodestruction in the atmosphere, leading to less cloud clover, and in turn, more UV exposure - a positive feedback loop? Oceanic acidification, as described previously by Ruth, changes water chemistry and inhibits phytoplankton growth, and so complicates matters still further.

The processes mentioned here take place on such a massive scale that they affect deeply the world climate. They are incredibly complex, and rely on a interlinked series of feedback loops. What happens when feedback is disrupted has yet to be seen.

For more detail see;

Miles, CJ, Bell, TG, Lenton, TM 2009. Testing the relationship between the solar radiation dose and surface DMS concentrations using ub situ data. Biogeosciences, 6, 1927-1934.

Miles, C., Bell, T., & Lenton, T. (2009). Testing the relationship between the solar radiation dose and surface DMS concentrations using in situ data Biogeosciences, 6 (9), 1927-1934 DOI: 10.5194/bg-6-1927-2009