A recent study has shown that using divers and snorkellers is not a good way to count fish. Wile the study is based on coral reef populations, it is pretty well known that while some fish will hang around, and may even be attracted to divers, most disappear as soon as they are aware of your presence…

If we were daft enough to try and work out a population census of the fish we had in British waters by using diver surveys alone, we would have a heavy over-reporting of wrasse (territorial, so come over to ‘look you over’ if you enter their patch) and dragonets (which are interested in looking through recently disturbed patches of sediment – such as those where an ungainly diver has landed – for food items)!

The importance of this work is that it does emphasise the need for a range of reporting and monitoring techniques. What divers are very good for is reporting the types of environments that they find underwater (biotopes – which are stable regions of interdependent organisms), perhaps even more importantly, we can appreciate them, and want to protect them along with their dependent fish (whether or not we see them!).

Above right: Photograph of a Ballan Wrasse, taken at Cathedral Rock, St Abbs.

Reference: Faculty of 1000: Biology and Medicine (2009, July 21). Overfishing And Evolution: Fish Fear Their Census-takers. ScienceDaily. Retrieved July 21, 2009, from Science Daily

It is vital to be able to reproduce measurements of the physical and chemical properties of seawater, and many years ago this was done using ‘Copenhagen standard seawater’. This was a sample of seawater carefully adjusted to match the standard parameters for the major dissolved ions. Back in those days the primary means of comparing seawater from one area to another was a standard titration of the chloride content, and each laboratory would carefully calibrate their titration against the Copenhagen standard to ensure reproducibility (in practice, usually scientists would perpare a large number of secondary standards from the Copenhagen standard for this purpose, to reduce cost).

This titration measured chlorinity, which was empirically related to the salinity of the seawater, but by only measuring one ion, the relationship was not very accurate or dependable under all circumstances. In the 1960-70’s titrimetry was gradually replaced by conductivity measurements, this was a measurement that was influenced by all of the ions present in the seawater sample, and as importantly, was a lot easier and quicker to perform. The Copenhagen standard seawater continued, however, to be used for standardising the conductivity measurement, though this was strictly designed for the earlier chlorinity procedure. Today we are placing every more reliance on the accuracy of our measurements of the thermodynamic properties of seawater. We now need very much greater precision and accuracy to follow tiny changes in surface seawater compositions, which reflect how the water responds to changes in temperature.

As a consequence a new standard has just been introduced. This uses the concept of ‘Absolute Salinity’, and should help researchers correct for experimental artefacts estimated to contribute up to 1°C differences in current sea-surface models.

Ref: CSIRO Australia (2009, July 20). Science Adopts A New Definition Of Seawater. ScienceDaily.
Retrieved July 20, 2009, from www.sciencedaily.com

Current climate models offer our best guess at the effects of increasing carbon dioxide levels on global temperatures. The current best guess is that 2°C rise will be OK, and we might get away with doubling the geological average for carbon dioxide concentration in the atmosphere (anthropogenic inputs have so far increased carbon dioxide concentrations by 33%). The problem has been that all of the models are just that – the only experiment is the one we’re living in, and we’d all be happier if we didn’t visit the worst case scenario with this world…

Only there is experimental data to be found in the geological record… Recently scientists investigating oceanic cores have followed an increase of 70% in carbon dioxide concentration that occured in the Palaeocene-Eocene thermal maximum, 55 million years ago. Unfortunately for our current models, this increase in carbon dioxide levels appears was associated with a global average temperature increase of 7°C – twice what our current best guess models are predicting.

More details: Rice University news release (via Science Daily)

The MARINE CONSERVATION SOCIETY runs the biggest annual clean up and beach litter survey in the UK. During the 2008 event 374 beaches all around the UK were cleaned and surveyed, sadly only 12 of all those beaches surveyed were in the North West England Region, (Solway to the Mersey). We would like to see a significant increase in that number in our region, therefore we asking for your help.
Could you and half a dozen friends spare a couple of hours during the weekend 19/20th. September 2009 to clean and complete a simple survey of litter over a short length of your local or favourite beach? In addition to providing valuable information in the battle against marine litter you would also be helping to save & protect our wonderful marine wildlife.

If you can help or would like more information, please contact the following:-

MCS Litter Team. T/phone. 01989567807
E.mail: beachwatch@mcsuk.org
Online. www.mcsuk.org

For local information please contact:- Ron Crosby, Tel. 01282 817776

As the bicentenary of Darwin’s birth, it was very fitting that at least one of our talks this year should feature him, but given the amount of coverage on radio and television already, would the talk bring anything new to light? In the event, by focussing on how his voyage on the Beagle influenced Charles Darwin, Keith Muscott opened a treasure chest of insights into the man and the age that made both the discovery and the dissemination of evolutionary theory possible.

What none of us in the audience had realised at the start of the talk was quite how intellectually challenging the small admiralty survey brigs were in the period following the Napoleonic war. They were crewed by young men with ambition (at peace, there was no other hope for advancement in the navy) and very considerable learning. Navigation at the time was a mathematically demanding occupation, this was a period where mechanical calculators (never mind computers) where unknown, and these vessels produced surveys that remained the standards over large parts of the world until the mid 20th century using nothing more complicated that dead reconning and mechanical chronometers! Where officers on sailing ships were expected to be excellent draftsmen – because there were no cameras, so drawings were the only way of bringing back representations of the far off places and people they visited.

Given this background, we were rather less surprised to find out that most of the officers from the Beagle went on to lives of very considerable distinction…

Barry

Tiny single celled plants called phytoplankton support the food chain of the world’s oceans. By locking up carbon dioxide during photosynthesis, they are also recognised as a vital component buffering the earth’s atmosphere from burning fossil fuels.

The numbers of phytoplankton are limited by the availability of sunlight and nutrients. Above 50°N in the Atlantic it had been assumed that winter turnover of water masses replenished the nutrient supply, and that the limiting factor for phytoplankton growth was a combination of grazing, and lack of silicates (a vital micro-nutrient for diatoms, pictured). Recently, however, experimental evidence, gathered by scientists at the University of Southampton, indicates that it is lack of iron, another important micro-nutrient, that is limiting the growth of phytoplankton.

Experiments elsewhere, aimed at increasing the amounts of carbon dioxide removed from the atmosphere, have tried to boost phytoplankton production by artificially adding more iron to water bodies.

From Science Daily

Seagrass is a general term for the only important ‘higher’ plants found in the sea. Unlike algae (seaweeds) they prefer to colonise sandy bottoms, where they are important for stabilising the sediment, and help provide a habitat for a diverse range of wildlife. Whilst seagrass is an important habitat defining species, is is not nearly as competent underwater as the algae, and, in particular, it appears to suffer greatly in turbid (cloudy) water. As a consequence it does not tollerate any coastal development that kicks up silt or increases pollution.

Anecdotal evidence suggests that seagrass meadows in the UK are recovering since the 1930’s when large areas were wiped out by disease. Globally, however, the situation appears to be less good. Scientists from the University of Maryland have just published a report emphasising the relationship between coastal development and increased population pressure in this region around the worl, and its effect o nthis important habitat.

Further reading:
UK Biodiversity action plan for seagrass beds
Loss of Coastal Seagrass Habitat Accelerating Globally (University Maryland report)

Above right: Zostera sp., photographed in Loch Linnh by the author

Barry

The oceanic gyres are areas of water at the heart of the major oceans. They are a long way from land, so receive little sediment. Estimates of sedimentation rate for the South Pacific Gyre, the largest of these bodies of water, are for less than 10 cm of sediment to accumulate in each million years…

The gyres are bordered by strong boundary currents, but are themeselves almost entirely still. As a consequence, there is very little nutrient influx, the water above is clear, but the sediment contains very little life. Rhode Island Scientists are speculating that the levels of nutrients may be so low that life in the deepest sediments may be reliant on hydrogen produced by water being split by the radioactive decay of minerals in the sediments!

More information:
University of Rhode Island press release (via Science Daily Deadlines)
Image of the five main oceanic gyres modified from NOAA via Wikipedia (full article and original image)

For contributors, the MCS blog has just been updated, hope you like the changes to the edit facilities!
Barry

Every year we get news of toxic algal blooms killing fish or making water unsafe to bathe in or drink from, but why do algae produce these toxic blooms? The easy answer is that they kill off predators, so the algae survive. Effectively, the toxin is there as a defence against predation. The problem with this theory is that micro-algae have to divert a lot of energy to produce toxins, so in most scenarios the toxic algae would be out-competed by species that did not go to the trouble!

Recently scientists have uncovered a more aggressive reason for toxin expression by algae, and one that gets round this problem. In the new theory the toxin is actually expressed against other algae in the water. Once killed, these dead phytoplankton leak nutrients back into the water that can be used to help fuel a toxic bloom.

From Science Daily Headlines