Wellies, Mud, Algae, Crabs and A Seal Named Rodrigo!

Today, (well sorta yesterday now) me and my girlfriend decided to take a day out as she had a day off from doing uni work. So we went to Hilbre Islands in West Kirby, which is a lovely scenic area of the Wirral, just over the water from Liverpool.

Hilbre islands are an archipelago consisting of three small islands at the mouth of the of the River Dee. It is an area of natural beauty and interest, the islands play an important role in the ecosystem as there is quite an extreme tidal system (as can be seen below).

(Left: High tide, Right: Low tide)

As the rocks and sea bed is exposed for half of the time, both the flora and fauna have had to adapt to avoid desiccation (fancy science word for dehydration). I could go off on one here rambling about many different species and how they are all uniquely adapted in their own way and so on… People have literally written books on these species and how they are adapted. So I will not list all the plants and animals, but I will talk briefly about some algae I find interesting.

I know this is primarily a zoology blog, but I can’t help but mention Fucus algae when talking about desiccation preventative adaptations, when it comes to staying alive at low tide these guys really are the kings. I know there are plenty of species I could waffle on about but I will just chose my favourite species (how cool… I have a favourite species of algae…) Fucus vesiculosus, commonly known as Bladderwrack. Fucus vesiculosus has multitude of morphological adaptations that are extremely beneficial. The organism, like many algal species,  has evolved what is called a holdfast. This works as a root-like structure which connects the entire organism to the substrate or ground.

Bladderwrack has also evolved extremely flat blades that allow it to soak up as much sunlight as possible without having to sacrifice many nutrients.  making it somewhat of a specialist in surface area to volume ratio. This adaptation also aids the osmotic processes that the alga relies on for its survival as it hasn’t evolved vascular tissue like plants have.

F. vesiculosus is known for the air bladders found in pairs on its blades. My girlfriend enjoyed using the dead detached blades as an organic bubble wrap, getting endless joy from popping the air bladders. Besides keeping Hol entertained  these bladders provide buoyancy for the brown algae, keeping it afloat when the tide comes in so photosynthesis can continue at a more productive rate. The bladders are filled an oxygen rich mucus and mostly O₂.

Okay now that I’m done waffling about algae, back to zoology!

I had actually planned to go during the summer break however, I just never got around to it. The reason I’ve wanted to back to Hilbre, is to see the wild life and also its really quite a nice place to be (weather permitting). I went during my second year of uni for an optional enrichment field trip for a marine biology course. Although it was great going with uni and I did learn a lot I remember thinking it would be really cool to spend the whole day here and really have a good look at the wild life in the inter-tidal zones. To look at the life in the rock pools and see how it changed, the closer we got to the water. The change was subtle at first; the crustaceans got progressively larger, the presence of larger groups of bigger sand gobies, Pomatoschistus minitus and common gobies Pomatoschistus microps was more frequent. Additionally, the scattered remains of the bivalves that the gulls had devoured became more sparse as we approached the algae covered rocks. Sparse patches of black and brown slowly replaced the sand, and above the dull blacks and browns, specs of green appeared, as you walk closer to the water these specs become fields until its lost to the waves.

Being the big kids that we are, we went rock pooling. Trudging through the mud in our newly bought wellies, gently turning over rocks and smiling like fools when we saw a bunch of crabs scurry for cover. Making sure to put the rocks back as we found them, so not to upset the rock pools inhibitors any more than we needed to. Disappointingly, I wasn’t able to find a large velvet swimmer crab, Necora puber, (see below) although I was able to find a young one which very impressive colouration. I don’t know why but I do have a liking for these evil eyed, bad-tempered little guys. I think it may be the effort that these guys put in to really try to get you if you manage to annoy one.

Another reason me and Hol wanted to go was to see the main attractions, the seals. Hilbre Islands are a great place to see gray seals Halichoerus grypus and harbour or common seals Phoca vitulina. It was quite exciting to watch their little heads pop up out of the water, then disappear moments later, only to reappear after a minute or so either 6 foot closer to you or a good way away if it had drifted into a slip stream. We sat on a cliff face and ate some lunch watching and naming the seals.  All in all it was a great day, was good to get back into a nature/ecology setting, even if it was just a silly day out of rock pooling and looking at seals called Rodrigo.

Left: Gray seal. Right: Harbour seal