We were enticed into the calm, sheltered blue waters of Lady Bay (Mull of Galloway) on Saturday (29th September 2009), only to find that conditions were pretty much un-diveable, with lots of suspended silt giving a visibility of about 10cm! You could see which way was up, and that was about it…

Having got wet, however, I decided to try and get some samples for microscopy, and got a rather nice sample of sea mat on a laminarian. Sea mat is an ectoproct, a colonial animal that is commonly found forming white reflective sheets on kelp fronds, look closer and you’ll see that the sheet is formed of lots of tiny cell-like structures, but that is about as much information as you’ll get with the naked eye.

Under the microscope, however, we can see that each cell is an individual animal – the colony being formed by numerous clones living tightly packed together. When feeding, each animal extends a cone of tentacles, which are quickly retracted if it is disturbed.

Above right: Two micrographs of Mambranipora membranacea (L): Top showing extended feeding arms of the lophophore. Bottom, showing the growing edge of the animal, on Laminaria sp.

Barry

The sea is a mysterious place to those of us who only get to visit it for as long as our canned air lasts. In our short dives we often spot things which are puzzling or unexplained. One of the things we’d speculated about on more than one occasion was why sea urchins wear hats.

It is quite a common phenomenon to see them with bits of kelp stuck to their tops – and quite firmly held in place too! – We’d guessed that they might be camouflage, but the truth is a little more prosaic…

Kelp and other seaweeds are not terribly palatable, even to grazing animals such as the urchins. Once the fronds have been broken up, however, then they start to die, and are colonised by bacteria and fungi. As the fronds decompose the amount of protein increases, and they actually become more nutritious. Also, the defensive chemicals (such as phenols) that seaweeds use to deter grazing while they are alive start to disperse, so they become less toxic. As a consequence, it pays an urchin to hold onto a stash of seaweed fragments as a light snack, or possibly even to mature them a little for better eating later.

The urchin’s hat is, therefore, its equivalent of a lunchbox!

Thanks to Little et al. The Biology of Rocky Shores 2nd Ed. publisher OUP, 2009, p105-106 for the enlightenment! Also thanks to Rob for the photo.

It was not the most promising of days – a small group of walkers for the MCS joined over 500 walkers for Galloway’s Society for the Blind in heavy rain at Arnside on Saturday morning (15th August 2009). The forecast was for brighter weather later – so we hoped that would be the worst of it, and looked forward to arriving at a sunny at Kents Bank!

The great column of walkers set off on time, but soon snaked out over a mile. We gathered for a sandwich, and to let everyone catch up, just before walking out onto the sands proper at Far Arnside. Everyone had just about dried out from the earlier rain when we arrived at the Kent’s channel. Due to the numbers we crossed the channel in two waves – this prevents people following too closely after each other, which can result in the sand liquefying under the last people to cross. Those of us in the second wave watched with some trepidation as the waves broke over the waists of some of those crossing. Just as the second wave started to cross, the rain came down again, so we were soaked from the top and the bottom simultaneously! The water lever was deeper than anyone we spoke to could remember on a walk before, and rumour was that there had been some debate between the guides about turning back. In the event we all made it across safely – though soggily!

Finally, the better weather that had been promised arrived, and we were only a little damp by the time we reached Kents Bank, and finished drying in the sun in the Albion’s beer garden on our return to Arnside.

Thanks to everyone who took part in this years Cross Bay walk, all proceeds go to MCS’ Seas Fit For Life campaigns. Thanks also to Cedric Robinson, the Queen’s Guide, and to his very helpful team of assistants on the sand.

Studies on beach sands around Lake Michigan and Lake Superior in the USA have shown that beach sands are an important refuge for E. coli, and concentrations of the bacteria in the sand may be many times greater than that in the water, and persist for considerable periods of time. Scientists estimate that between 10 and 30 people per thousand are in danger of stomach upsets if they eat after playing in the sand without cleaning their hands – simply rinsing reduces the danger dramatically, though scrubbing with soap is best.

Frustratingly these studies refer to fresh water lakes, and it is not clear whether or not the same might be true of sea-water bathing beaches. Still, it is clearly advisable to follow your mother’s advice and always wash your hands before eating!

References
United States Geological Survey (2009, August 12). What Science Says About Beach Sand And Stomach Aches. ScienceDaily. Retrieved August 13, 2009.
American Chemical Society (2007, May 29). Beach Sand May Harbor Disease-causing E. Coli Bacteria. ScienceDaily. Retrieved August 13, 2009.

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