Science roundup, 19th July 2010

July 19th, 2010

A quick turn-around on this occasion – with hopeful news from the Gulf of Mexico, though even if the leak has been blocked successfully, it will be a long time before the effects of this disaster have been fully understood (never mind fixed). To another man-made disaster, this time off the southwest coast of Africa. Here over-fishing in the 1960’s resulted in ecosystem collapse, and only now are there a few hopeful signs of recovery, with the arrival of some tough gobies that can cope with anoxic waters and eat jellyfish…

First though, have we got the theory of algal blooms wrong? If we have, this could have serious implications for climatic modelling!

Life at sea

Acepted theory of algal blooms wrong: Remote sensing data has been shown to contradict the accepted ‘critical depth hypothesis’ for algal bloom formation. This theory suggests that algae bloom in spring in the increased light, and as surface waters warm. Remote sensing however, shows that algae actually start their bloom in mid winter, when the water is at its coldest and darkest. The new theory being postulated to account for this observation suggests that the really important factor is zooplankton (microscopic animals) feeding rates on phytoplankton (algae). These rates drop during mid winter, as storms stir the water, diluting the total concentration of plankton by mixing productive surface waters with deeper waters, making it hard for zooplankton to find a meal. The prediction is, therefore, that more and bigger winter storms will lead to bigger algal blooms. In contrast, warmer stratified waters may result in smaller algal blooms, adn this is what is predicted by many global warming models. The unfortunate result of this would be a feedback loop that resulted in algae being able to take less carbon out of the ocean, resulting in less efficient buffering of increased carbon dioxide levels. ScienceDaily (July 16, 2010) More climate change towards the foot of this post…

Ink saves sea-hare: A number of molluscs squirt ink to deter predators, including the cuttlefish (order Sepiida – from which sepia ink is made), octopus and squid. I had not realised until spotting this article that sea hares can also squirt ink. The study is on Aplysia californica, where the ink is found to both smell and taste bad to fish (rather than offering a means of concealment). From Practical Fishkeeping, 12 July 2010. A quick check in the guides, however, indicates that the sea hares (Aplysia punctata) found in British waters can also secrete a ‘purple slime’ used for deterring fish. (Gibson, Hextall and Rogers Photographic Guide to Sea and Shore Life…, Oxford, 2001, 256-7.

How planktonic larval stages effect species distribution: This PLoS 1 article actually asks a rather more specific question of how the catfish Cathorops mapalehave diverged evolutionarily since its range was split in the early Pleistocene with the rise of the Santa Marta Massif (c.a. 0.8 MYA). Cathorops lacks a pelagic larval form, so dispersal along the coast was disrupted by this process, resulting a slow divergence of the catfish populations on either side of the massif.
Betancur-R R, Acero P. A, Duque-Caro H, Santos SR (2010) Phylogenetic and Morphologic Analyses of a Coastal Fish Reveals a Marine Biogeographic Break of Terrestrial Origin in the Southern Caribbean. PLoS ONE 5(7): e11566. doi:10.1371/journal.pone.0011566

Trashy island: Apparently the area of floating trash in the Pacific is twice the size of Texas. This report suggests recycling the trash as a luxury floating island… File under ‘speculative’. From Green.Blorge July 1st 2010

Indian seahorses to breed in captivity: The Zoological Survey of India (ZSI) is to attempt captive breeding of seahorses at their premises in Chennai. The numbers of seahorses in the Indian ocean have been greatly depleted by commercial fishing, to the extent that they are now protected species. sify News 2010-07-17 13:30:00

Fluorescent copepods: Many marine organisms exhibit fluorescence, now two of the brightest fluorescent proteins to be found to date have been identified in the copepod Pontella mimocerami. Fluorescence in these tiny marine animals can put on a great night-time display, but the workers here are more interested in the more mundane possibilities of using them as bio-genetic markers. Already several of the fluorescence mechanisms used by marine organisms have been transcribed into other plants and animals to follow the success of a gene transfer.
Hunt ME, Scherrer MP, Ferrari FD, Matz MV (2010) Very Bright Green Fluorescent Proteins from the Pontellid Copepod Pontella mimocerami. PLoS ONE 5(7): e11517. doi:10.1371/journal.pone.0011517

Marine bacterial family tree: Members of the Roseobacter clade apparently constitute between 10 and 25% of the bacterioplankton in the world’s oceans. This paper elucidates their genetic family tree. In this process the researchers identified several genes involved with B12 synthesis, as well as genes that code for the enzymes that degrade dimethylsulfoniopropionate – an important process in global climate control (see climate below).
Tang K, Huang H, Jiao N, Wu CH (2010) Phylogenomic Analysis of Marine Roseobacters. PLoS ONE 5(7): e11604. doi:10.1371/journal.pone.0011604

What will I eat today? The quandries of a mixotrophic organism: This is an entertaining description of a rather gruesome series of experiments that suggest that anemones with algal simbionts use the food that they hunt and the food they generate from sunlight in different ways. Algae use sunlight first to generate small carbon molecules, which they can then build up into more complex stuff. By contrast hunting living organisms gives you a ready supply of complex molecules to order. In mixotrophic organisms, that can do both, then the simple sugars produced by autotrophy (from sunlight and carbon dioxide) are used as a rapid energy source, whereas more complex molecules, derived from prey items, tend go to develop tissues and for growth. Deep Sea News July 15th 2010.

Oil spill

Oil spill stopped: On Thursday July 15th, after 85 days of the spill, BP succeeded in placing a cap on the Deepwater Horizon oil well. Today (Saturday 17th, 15:30hrs), the cap has completed its test phase, and there is some optimism that no more oil is leaking from the site. With this news we expect that interest in the spill will diminish in national and international press, though the process of cleaning up is likely to take many years more. I’m hopeful that we will still be able to follow this story, as it is only as we move out of the crisis phase that we are likely to be able to get together a sensible analysis of this incident. Yahoo News ca. 15:30hrs 17th July 2010 .

Exploration and exploitation

Change of scene, change of species: The coasts of southwest Africa used to be home to large shoals of sardines, until these were fished to exhaustion in the 1960’s and 70’s. This resulted in an ecosystem collapse, the sardine’s place in the ecosystem was taken over by jellyfish, and algal blooms now sink to the bottom (rather than being eaten by the sardines), where their decomposition results in anoxic waters that very little can live in. One problem is that the jellyfish are a poor food source for other animals, so they have grown fat, whilst everything else either died or moved out. Recently, however, scientists have found that the goby Sufflogobius bibarbatus is starting to move in and eat the jellyfish. In this way there is hope that these waters might slowly recover a more functional ecosystem, as the goby’s are a potential food source for larger fish and sea birds. The gobies appear to have a range of other adaptions to living in this degraded ecosystem, including the ability to live at low oxygen levels for prolonged periods, and tolerate high levels of hydrogen sulphide. Whilst the adaptive abilities of this goby are to be admired, the important lesson to be learnt here is DON’T OVER FISH. Forty years is very long time to wait for a system to show signs of recovering, and it is likely to be a lot longer before the area can support any kind of commercial fishery. ScienceDaily (July 15, 2010)

Climate related

Acidified waters in Puget Sound: Researchers report unusually low pH values (low pH = high acidity) in the deep waters of the Puget Sound, an estuary on the west coast of the USA, close to the Canadian border. They were able to attribute much of the fall in pH to increased carbon dioxide concentration, which is ultimately derived from burning fossil fuels. Scientists had to disentangle anumber of contributing factors to the rise in acidity, including decomposing vegetation in the estuary. As yet they have been unable to determine whether or not this is influencing shellfish growth rates in the sound. ScienceDaily (July 18, 2010)

Bad smell for bitter fishes: It appears that fish raised at increased carbon dioxide levels are less able to sniff out predators, and as a consequence fewer survive to maturity. The research was carried out on clown and damsel fish. Telegraph 18th July 2010.

How important is climate to the species mix? For a long time conservationists have been worried by how climate change might cut off species in environments that become increasingly hostile to them. In this paper the authors compare the relative importance of climatic variables with underlying geological conditions – altitude, bedrock etc. The work supports the idea that geology is very much more important than climatic factors. This suggests that conservation efforts should focus on geological hotspots, rather than on the preparation of migration corridors for organisms to allow them to move to more hospitable climates.
Anderson MG, Ferree CE (2010) Conserving the Stage: Climate Change and the Geophysical Underpinnings of Species Diversity. PLoS ONE 5(7): e11554. doi:10.1371/journal.pone.0011554

Warm water slows coral growth: Computed tomography (CT) scans have been used to measure the annual growth rings in corals from the Red Sea. These measurements show that the growth rate of Diploastrea heliopora has fallen by 30% over the last decade, correlating with average water temperatures that are up by 1.5°C. The results are particularly surprising and worrying because D. heliopora is a species of coral that has not shown evidence of bleaching events or other ill health in the warmer waters. CT scans offer many advantages over traditional sectioning and x-raying to get this information. Being performed on intact coral branches it is possible to map out the growth rings in 3D, and so avoid missing years. ScienceDaily (July 16, 2010)

Marine microbes sniff a change in the weather: How marine microbes hunt may impact climate. When algae die they release dimethylsulfoniopropionate, a chemical that microbes feed on directly to produce dimethyl sulphide, as well as using it to navigate towards the tasty snack. The dimethyl sulphide they produce is an important nucleatiuon factor in cloud formation, so the quantities available in the atmosphere directly influence cloud density, and how much solar radiation is trapped beneath them, or reflected back into space. ScienceDaily (July 15, 2010)

Posted in Conservation, Marine science update, Science