In marine science this issue, most of our articles relate to how phisico-chemical environment influences the distribution of species. I particularly liked the way the bio-geographical history of the North Atlantic has been revealed through the mDNA of the rough periwinkle. Conservation issues cover cetaceans, coral and cod. Our first article in fisheries raises some questions about the sustainability of invertebrate fisheries. Finally, new estimates suggest that ocean currents (rather than biological activity) are more important in removing carbon from surface waters in the North Atlantic.

Marine science

Survivor! The rough periwinkle (Littorina saxatilis) is common on coasts throughout the Northwest Atlantic region. It is ecologically adaptable, living on cliffs, rocky shorelines and on seaweed, and comes with a multitude of morphological differences. This study of the periwinkle’s mitochondrial DNA (cytochrome b) begins to be reveal the complex climatic and temporal background to this diversity. The DNA evidence identifies five groups broadly centred on populations in Nova Scotia, New England, Faroes, Northwest Europe, UK and Spain. The cause of the diversity is the ice ages, during which water temperatures were cool enough for populations to become established as far south as the Canary Islands and Southern Mediterranean, where outlying populations still persist. Further north, ice isolated populations of Littorina in small, safe enclaves. These formed founder populations that re-colonised the shorelines about them as the ice receded.
Panova M, Blakeslee AMH, Miller AW, Mäkinen T, Ruiz GM, et al. (2011) Glacial History of the North Atlantic Marine Snail, Littorina saxatilis, Inferred from Distribution of Mitochondrial DNA Lineages. PLoS ONE 6(3): e17511. doi:10.1371/journal.pone.0017511

Aquatic bacterial communities: This study looks at how bacterial communities change in the tropics in response to the physico-chemical environment. The highest density of bacteria is seen in low-salinity water in mangroves (with 1,360,000 cells per mL). There are also many more species in fresh waters, though many of these only have a small population, so the Shannon Index for marine and fresh water bacterial communities are pretty similar. In contrast to earlier understanding, it is now clear that very few, if any, bacterial species range across both marine and fresh-water habitats, which appear completely distinct. The paper discusses parameters, such as the chemical composition of the waters, that might influence the size and diversity of the bacterial communities observed.
Silveira CB, Vieira RP, Cardoso AM, Paranhos R, Albano RM, et al. (2011) Influence of Salinity on Bacterioplankton Communities from the Brazilian Rain Forest to the Coastal Atlantic Ocean. PLoS ONE 6(3): e17789. doi:10.1371/journal.pone.0017789

Squishing shrimps: The shrimp Palaemonetes varians that usually lives in shallow brackish waters is capable of surviving at pressures equivalent to a depth of 3km. For this species at least, depth is not a barrier to colonisation, and closely related species are found colonising deep-sea vents. ScienceDaily (Mar. 10, 2011)

Segregated by depth: Temperature depth profiles for Icelandic cod indicates that there are two populations subtly segregated by the choice of depth that they spawn at.
Grabowski TB, Thorsteinsson V, McAdam BJ, Marteinsdóttir G (2011) Evidence of Segregated Spawning in a Single Marine Fish Stock: Sympatric Divergence of Ecotypes in Icelandic Cod? PLoS ONE 6(3): e17528. doi:10.1371/journal.pone.0017528

Conservation

Whale wintering ground: Acoustic recorders have been used to track the songs of male humpback whales, and found that their wintering grounds now extend over the entire Hawaiian archipelago. The range is thought to have been increasing steadily over the last three decades, as the population recovers. ScienceDaily (Mar. 9, 2011)

Dolphins exposed to algal toxins: DNA studies show that dolphins (Tursiops truncatus) living off the Florida coast are exposed to algal toxins derived from common bloom events in the region. Elevated levels of toxins, determined by the concentration of domoic acid in the dolphin’s faeces, correlate with elevated levels of white blood cells in the dolphins.
Twiner MJ, Fire S, Schwacke L, Davidson L, Wang Z, et al. (2011) Concurrent Exposure of Bottlenose Dolphins (Tursiops truncatus) to Multiple Algal Toxins in Sarasota Bay, Florida, USA. PLoS ONE 6(3): e17394. doi:10.1371/journal.pone.0017394

Coral changes on the Great Barrier Reef: A review of changes to coral coverage on the GBR over a period of 15 years, revealing the impact of stresses such as storm damage, disease, the crown-of-thorns and bleaching events, and how the reef have subsequently recovered. The pattern of coral development over the area of the reef is very complex, but the authors could see no net decline in coral coverage over the study period. The study will form a baseline against which future changes can be measured.
Osborne K, Dolman AM, Burgess SC, Johns KA (2011) Disturbance and the Dynamics of Coral Cover on the Great Barrier Reef (1995–2009). PLoS ONE 6(3): e17516. doi:10.1371/journal.pone.0017516

Herbivores keep coral healthy: Seaweed eating fishes such as parrotfish and surgeonfish are essential to prevent corals from being over-grown, but they are very picky about what they eat. Once the seaweed has grown sufficiently, it becomes tough and less attractive to the fish, which prefer to graze new-growth, and so do not mow older seaweed back. This means that once established beyond a certain level, seaweed will experience run-away growth, killing the underlying coral. The work emphasises the important in maintaining a healthy population of fish on reef ecosystems. ScienceDaily (Mar. 11, 2011)

Cod go over the top: Like WWI infantrymen, cod (Gadus morhua) larvae run a gauntlet of predators, and very few are ever actually recruited into the adult population. This research shows that a number of factors come into play, but the number of larvae released is possibly less important than the timing of their release. Ideally larvae need to be released when they have a ready source of zooplankton in the spring bloom, but late in theis period the number of predators is high, favouring earlier release, even if food availability is not optimal. Other factors are light, temperature and visibility, with cloudy waters making it harder for the larvae to spot and catch zooplankton.
Kristiansen T, Drinkwater KF, Lough RG, Sundby S (2011) Recruitment Variability in North Atlantic Cod and Match-Mismatch Dynamics. PLoS ONE 6(3): e17456. doi:10.1371/journal.pone.0017456

Fisheries and exploitation

The rise and fall of the spineless fish: As stocks of vertebrate fishes are depleted, and increasingly regulated, fisheries focussed on other marine organisms (prawns and shellfish for examples) are expanding rapidly, and becoming increasingly globalised. The total catch of invertebrate species (one of the few quantitative parameters available) is related to many factors, but it is showing evidence of over-exploitation and collapse in some stocks. The effect of the fisheries on marine ecosystems is un-quantified, but the use of benthic trawls and dredges for prawn fisheries (approximately 50% of total invertebrate fisheries effort) results in indiscriminate damage to benthic communities. The effect of the bulk removal of many invertebrate species at specific trophic levels in the food chain is broadly unknown, however the tonnage of filter feeders and detritivors removed is sufficient that it may impact water quality, at least at a local level, until stocks recover.
Anderson SC, Mills Flemming J, Watson R, Lotze HK (2011) Rapid Global Expansion of Invertebrate Fisheries: Trends, Drivers, and Ecosystem Effects. PLoS ONE 6(3): e14735. doi:10.1371/journal.pone.0014735

Body building tunicate: Sea squirts (tunicates) are one of the very few animals that use cellulose in a structural role – using it to build their protective tunics. Scientists at Manchester have found that fibres spun from tunicate cellulose is good for aligning muscle cells, and may be useful for growing muscle for tissue replacement therapy. ScienceDaily (Mar. 12, 2011)

Vessicle vaccine: A vaccine to the bacterium Edwardsiella tarda, which causes deaths of both fresh and salt water fishes, is being developed based on the outer membrane of the bacterium, which carries 74 proteins that might prime the immune system of a treated fish.
Park SB, Jang HB, Nho SW, Cha IS, Hikima J-i, et al. (2011) Outer Membrane Vesicles as a Candidate Vaccine against Edwardsiellosis. PLoS ONE 6(3): e17629. doi:10.1371/journal.pone.0017629

Cleaner fish farms: Model salmon farms in Denmark show how the envoronmental impact of fish farming can be reduced. The high-tech farms recycle 95% of their water, reducing the volume abstracted from rivers. The farms are reported to also be able to rear sea-fish. ScienceDaily (Mar. 9, 2011)

Gene regulation in fish: Every organ in your body carries the same genetic information, which you inherited from your parents. To carry out different roles, each tissue only permits some of the genetic code to be active. In this study the pattern of RNA activity in the food fish Asian Seabass (Lates calcarifer) is revealed. There hasn’t been much study on gene regulation in fish to date, so this is quite novel work, and a functional analysis of what it all means is still to be undertaken.
Xia JH, He XP, Bai ZY, Yue GH (2011) Identification and Characterization of 63 MicroRNAs in the Asian Seabass Lates calcarifer. PLoS ONE 6(3): e17537. doi:10.1371/journal.pone.0017537

Pollution

Driving wedges between marine communities: Human activity discharges large amounts of effluent into coastal waters every day, including heavy metals, hydrocarbons and excess nutrients. It has now been found that the presence of pollutants in the water discourages settlement of many marine species, and can act as a barrier between coastal marine communities. ScienceDaily (Mar. 10, 2011)

Climate change

Pumping carbon into the deeps: The world’s oceans capture about 30% of man-made carbon dioxide, and are the most important component of the atmospheric buffering system that holds climate change in check. There are two mechanisms by which carbon, trapped initially as carbon dioxide from the atmosphere, is transferred from surface waters into the deep waters of the oceans. The first is through biological activity, which converts the carbon dioxide into larger organic molecules, which either swim or settle out of the surface water. The second is through currents – the large scale physical movement of water driven by temperature differences, salinity and gravity. The work referred to here suggests that in the North Atlantic, physical currents are 100 times more significant than biological systems. ScienceDaily (Mar. 9, 2011)

Going up… 475 gigatons of ice are being lost by the Greenland and Antarctic ice sheets every year, on average. This is enough to cause a 1.3 mm increase in sea-level each year. ScienceDaily (Mar. 8, 2011)

Cold, warmer, warmer… We’re claiming a unique victory for this column, as more Americans believe in ‘climate change’ (74%) than in ‘global warming’ (68%). ScienceDaily (Mar. 8, 2011)

Synchrotron to probe sea-ice: The delicate microstructure of sea-ice from cores is to be probed with synchrotron radiation to give more information about the conditions under which it formed, and provide more information about its properties. ScienceDaily (Mar. 10, 2011)