Friday, 19 July 2013

Post survey pictures


If you have been looking in on this blog and have noticed a lack of new information over the last few weeks, I can but apologise. I have been away for a wee holiday followed by an intense period of surveys for this and other studies which are taking place within the remit our summer laboratory crew.

Also time consuming is the fact the during the biodiversity surveys within Galway bay I usually bring back a bucket of species, usually algae/seaweeds, which I haven't being able to identify in the field. The next 1 to 3 days can include periods of searching through indentification guides and squinting into microscope lenses in order to make a positive identification of all the species.

Speaking of species, the strange greyish-purple monster that featured in the last post to this is actually a very small critter called Anurida maritima, (it has no common name that I know of )its about 3mm long and lives on the surface of the water in groups. It's an arthropod of the class, Collembola.

One of the features of collembolans is that they aggregate into groups and exude a chemical signal so that they can home in on each other if they get separated. They have a hydrophobic "skin" which allows them to float on water and if they get separated from the group because of a wave you can watch them re-amalgamate like the liquid metal terminator in Terminator 3. They are scavengers, feeding on dead marine animals such as limpets and periwinkles.

Coincidentally, Anurida maritima was one of the handful of animals that we found in our artificial rock pools during the first official survey that we carried out 1 month after their construction.

During the survey we found common shore crab, dog whelk and periwinkles within the pools

Common shore crab ( Carcinus maenas)
 You might think that the shore crab in the picture opposite probably simply got stranded in the pool when the tide retreated however, due to the rough texture of the pool sides, crabs of this size are easily able to exit the pools so in all probability its presence in the pool is by choice.

Common periwinkle ( Littorina littorea )

Dog whelk ( Nucella lapillis )

Mud attaching to the pool sides

The crab, periwinkle and dog whelk are transient occupants of the pools and whilst they are a welcome sight, fixed organisms such as seaweeds are of greater interest at this time.

Being a fixed source of food and shelter, seaweeds allow for the colonisation of bare spaces by other organisms however they require a bit of time to become attached and even more time to become evident to the observer in the field.

It is possible that microscopic seaweed spores are contained within the light covering of mud that has attached to the pool sides which can be seen in the second picture below.

That said, seaweeds don't root into mud like terrestrial plants root into earth, they simply land randomly as a spore on a suitable substrate and stick.

They then obtain their nutrition from compounds such as carbon dioxide and nitrates contained within the seawater which they absorb through their outer layer, it's akin to swimming in a bath of your dinner and absorbing your food through your skin, yum!

Of course, being plants, seaweeds use sunlight energy to create carbohydrates from which to build their bodies and so grow to create more carbohydrate and so grow more, and so on and so on.

This is a very simplified version but you get the picture I'm sure.

However if there is any nutrition to be found in this mud it could be used by bacteria or other microscopic organisms to grow and expand their numbers. In time these will form a biofilm upon which animals such as limpets can feed.

If you are on the causeway and you look closely at the concrete of the sheds you should see a series of small fan-shaped marks which have been left when limpets move over the concrete and scrape the baterial biofilm off for food.

I'll see if I can get a good picture of the marks today during my visit so you can know what to look for.

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