Back to basics this week, most of the science is involved with nutrition – eating and getting eaten – with a brief interlude from diatoms who are working hard on producing toxins to ensure that anyone who does eat them regrets it! The theme is picked up again in Fisheries, here our human apetite is pushing global fish stocks to the point of no return. To start though, a little fun with a novel tunicate…

Marine science

Great floating tunicates, Batman! One to add to your collection of tunicates – Oikopleura dioica is a floating version that builds its own home-come-harvester out of jelly. The adult is planktonic, and seems to have retained most of the features we would usually associate with a juvenile (a tadpole shape with a notochord). See the link for more about its very unusual genetics, and a nice video of it in action.
Lucas Brouwers in Culturing Science, December 1, 2010

Hunting in the mist: This study follows both predator and prey about their business in Norfolk Bay, Tasmania. Using acoustic transponders attached to individuals of a Broadnose Sevengill shark (Notorynchus cepedianus) and its prey the Gummy shark (Mustelus antarcticus), researchers were able to follow where they were through several diurnal cycles with an accuracy of up to +/- 2m. The prey is seen to stick close to the bottom for most of the day, whilst the predator is more mobile in the water column, particularly at night. The data is treated statistically, as without crittercams it is not possible to correlate the animal’s movements directly to its behaviour. This leads to some fun speculation as to what exactly is going on…
Barnett A, Abrantes KG, Stevens JD, Bruce BD, Semmens JM (2010) Fine-Scale Movements of the Broadnose Sevengill Shark and Its Main Prey, the Gummy Shark. PLoS ONE 5(12): e15464. doi:10.1371/journal.pone.0015464

El Niño effects young fish: The numbers of young fish on coral reefs in the South Pacific declined dramatically after the intense El Niño event of 1997-8. This was due to the collapse in the plankton community following the sudden warming of the water that presaged the event. ScienceDaily (Dec. 2, 2010)

Green teeth: Young great white sharks (up to 3m in length) have weak jaws that reduce their killing potential. As the shark gets older the jaw is progressively mineralised, permitting it to exert greater forces on prey. ScienceDaily (Dec. 2, 2010

Foraging patterns in shearwaters: Two female Great Shearwaters (Puffinus gravis) were fitted with time and depth recorders to monitor their feeding behaviour. Most dives were less than 2m deep, but the birds could reach depths of nearly 20m during dives lasting up to 40s. Diving locations were similar to those of males of the species, which were followed with satellite tracking tags. The behaviour is compared to that recorded for other shearwater species at other locations.
Ronconi RA, Ryan PG, Ropert-Coudert Y (2010) Diving of Great Shearwaters (Puffinus gravis) in Cold and Warm Water Regions of the South Atlantic Ocean. PLoS ONE 5(11): e15508. doi:10.1371/journal.pone.0015508

Why become a poisoner? Some dinoflagelate species are notorious for producing toxins, and this paper seeks to identify why they do it. Focussing on dinoflagellates in the genus Alexandrium, that produce Paralytic Shellfish Toxins (PST), they find that some dinoflagellates do increase the amounts of PST produced in response to the presence of copepods – their main predators. The amounts of PST taken up by the copepods was measured, as well as some basic tests of the health of the surviving copepods. There is the suggestion that the production of PST is dependent not only upon the species of dinoflagellate, but also upon the species of copepod, implying some interesting co-evolutionary processes.
Wohlrab S, Iversen MH, John U (2010) A Molecular and Co-Evolutionary Context for Grazer Induced Toxin Production in Alexandrium tamarense. PLoS ONE 5(11): e15039. doi:10.1371/journal.pone.0015039

I can smell you! This paper looks at the molecular basis for the sense of smell in zebra fish. An acute sense of smell is essential for many fish species, which need to detect traces of food in a massive water body. The focus of the study is a membrane bound protein, which the authors succeed in expressing in useful quantities by bioengineering mammalian cell lines.
Leck K-J, Zhang S, Hauser CAE (2010) Study of Bioengineered Zebra Fish Olfactory Receptor 131-2: Receptor Purification and Secondary Structure Analysis. PLoS ONE 5(11): e15027. doi:10.1371/journal.pone.0015027

Bugs on the beach: We’ve known that microbial communities are important in the marine ecosystem for a long time, but we know next to nothing about the microbial ecosystem within the marine environment. This paper looks at microbial communities in the English Channel, and reveals that they change on both diurnal and seasonal cycles. Bacteria are found to be far more diverse than the archae, but that both followed roughly the same pattern, with diversity increasing in winter. The makeup of these communities were found to change very quickly – of the order of a few hours. Species show a diurnal variation, this is particularly evident in the cyanobacteria, which multiply very quickly over night, resulting in a 15 to 60 fold increase in the number of individuals depending upon the time of year.
Gilbert JA, Field D, Swift P, Thomas S, Cummings D, et al. (2010) The Taxonomic and Functional Diversity of Microbes at a Temperate Coastal Site: A ‘Multi-Omic’ Study of Seasonal and Diel Temporal Variation. PLoS ONE 5(11): e15545. doi:10.1371/journal.pone.0015545

Conservation

A case of mistaken species? Many coral species are extremely plastic, and can look very different when grown in different environments. This study looks at the classification of Hawaiian Montipora family, which has several dozen ‘species’ determined by their morphologies. The family is likely to be listed as endangered, so knowing how many species there are, and how many of each species there are is going to be vital in working out and monitoring a conservation plan. In this instance studies of the mitochondrial DNA picked out four clades, but the evidence for there being distinct species within these clades is not clear, despite considerable morphological differences between individuals. The evidence suggests either incipient speciation within the clades, or a broad span of genetic diversity within a very much smaller number of true species.
Forsman ZH, Concepcion GT, Haverkort RD, Shaw RW, Maragos JE, et al. (2010) Ecomorph or Endangered Coral? DNA and Microstructure Reveal Hawaiian Species Complexes: Montipora dilatata/flabellata/turgescens & M. patula/verrilli. PLoS ONE 5(12): e15021. doi:10.1371/journal.pone.0015021

Sharks protected: The International Commission for the Conservation of Atlantic Tunas agrees to bans on fishing for a number of endangered shark species. Atlantic bluefin tuna quotas are, however, largely unaffected. By Juliet Eilperin in the Washington Post. Sunday, November 28, 2010

Fisheries and exploitation

A world without fish: UBC researchers have analysed the expansion of the global fisheries industry between 1950 and 2005. OVer this period catches increased because the area of ocean being exploited by modern intensive fisheries practices was increased. The paper has disturbing maps showing the area of the oceans where in excess of 30% of total primary production would have to be converted into fish protein simply to sustain the reported landings. The pattern of over exploitation has now been exported over the entirety of the World’s Oceans. It is not surprising that our bankrupt fisheries policies have seen one stock after another collapse in a domino effect that is now running out of places to go.
Swartz W, Sala E, Tracey S, Watson R, Pauly D (2010) The Spatial Expansion and Ecological Footprint of Fisheries (1950 to Present). PLoS ONE 5(12): e15143. doi:10.1371/journal.pone.0015143

Pollution

Fate of the oil: Oil is still coming ashore on many Gulf Coast states, whilst depressed dissolved oxygen concentrations in the water column indicate the presence of a persistant plume of oil in deep water. Deep Sea News, December 2nd, 2010

Biofuels impact water quality: The increased amounts of nitrogen required to grow maize for biofuels in the Mississippi delta are threatening further damage to coastal gulf waters. The switch to growing maize also increases the amount of water extracted from aquifers in the region. ScienceDaily (Nov. 30, 2010)

Climate change

Sea-level stick and slip: Gloabal sea level rises following the end of the last ice-age have been found to be discontinuous, with periods of little movement (less than 1m rise per century) followed by very much faster rise (up to 2.5m per century). ScienceDaily (Dec. 1, 2010)

Coastal wetlands at threat: U.S. Geological Survey scientists conclude that coastal wetlands are more at risk from predicted sea-level rises than previously thought. ScienceDaily (Dec. 1, 2010)