Rockpools

Of course you can’t go rockpooling in Forest Row, so we had to head to the coast to see some groups of organisms that don’t occur in the Weald. Most importantly, there was a supremely low tide a week ago, so there was the opportunity to see things that rarely get uncovered by the sea.

There was a bit of a wind blowing in as Ann, Rachel and I cautiously trod over the seaweed-encrusted rocks at Birling Gap, but it wasn’t too cold. Really. Graeme Lyons had suggested we head to the lowest part of the shore we could and then follow the tide out, so barring a few distractions on the way, that is what we did.

Rockpooling at Birling Gap

The top of the shore has loads of green seaweeds, grading in to familiar browns, such as Bladder Wrack (Fucus vesiculosus), and the whole of the sandy areas right down to the lowest exposed part of the beach included the filamentous red Sand Binder (Rhodothamniella floridula). Though there are other similar-looking red filamentous seaweeds, none has the sand binding properties of this one, or are quite so widely distributed across the shore.

Picture of Sand Binder (Rhodothamniella floridula)

Magnified view of a single filament of Sand Binder (Rhodothamniella floridula)

Around the middle part of the shore the algae were a bit different and included Saw Wrack (Fucus serratus), and large mats of Pepper Dulse (Osmundea pinnatifida), which we did nibble to check its pepperiness. It is a good idea to wash off the sand first.

Unsurprisingly, molluscs abounded. The first one to attract our eyes was the Common Limpet (Patella vulgata), but we forgot to check for others as we worked our way down the shore, since Birling Gap is at the eastern edge of the range for the Black-footed Limpet (Patella depressa), and Patella pellucida has also been recorded there. Something to look for next time![1]

Periwinkles and Top-shells were also frequent, and we recorded Grey Top Shell (Gibbula cineraria), Flat Top Shell (Gibbula umbilicalis), Common Periwinkle (Littorina littorea), Rough Periwinkle (Littorina saxatilis), and the strikingly yellow Flat Periwinkle (Littorina obtusata). Another common species at Birling Gap is the invasive American Slipper Limpet (Crepidula fornicata), the shells of which are all over the top of the beach. We also found quite a few shells (though not live organisms) of the Common Oyster (Ostrea edulis). However, looking at the list of all taxa recorded at Birling Gap (including the terrestrial species) it is clear that there are many other marine molluscs that we missed.

Picture of Flat Periwinkle (Littorina obtusata)

Flat Periwinkle (Littorina obtusata)

One of the reasons I like nosing around the sea shore is because you can find groups of organisms that occur nowhere else, and which are a great reminder of the amazing diversity of life. One such group is the Cnidarians, the common examples of which were the Beadlet Anemone (Actinia equina) and the Strawberry Anemone (Actinia fragacea).

Picture of Strawberry Anemone (Actinia fragacea)

Strawberry Anemone (Actinia fragacea)

This diversity is also true of the algae. The differences between the red, green and brown seaweeds are huge, and taxonomically they are all in different groups, with the browns (Chromists/ Heterokonts) notably having four membranes around their chloroplasts, and many reds having extremely complex life cycles.[2]

Compared with the west coast of Britain, Sussex has relatively few seaweeds, though that does make it slightly easier to work out what they are. As you might expect, there are lots of common species, such as the brown Grape Pip Weed (Mastocarpus stellatus) and the red Carrageen (Chondrus crispus).

Picture of Grape Pip Weed (Mastocarpus stellatus)

Grape Pip Weed (Mastocarpus stellatus)

The closer  you get to the lowest part of the exposed shore the more interesting things turn up, even if none of them are especially rare. Many are quite beautiful, such as Plocamium cartilagineum.

Picture of Plocamium cartilagineum

Plocamium cartilagineum

You also get seaweeds growing on other seaweeds (ie epiphytes), such as this mixture of reds on the hairy brown Cladostephus spongiosus, including the broad fronds of Cryptopleura ramosa and stripy Ceramium.

Picture of epiphytes on Cladostephus spongiosus

Epiphytes on Cladostephus spongiosus

Other species of the lower shore included Hypoglossum hypoglossoides, a rather scraggy bit of Eyelash Weed (Calliblepharis ciliata), and lots of the bright green Cladophora sericea, which could be contrasted with its darker, rougher relative Cladophora rupestris elsewhere on the shore.

Picture of Hypoglossum hypoglossoides

Hypoglossum hypoglossoides

Picture of Cladophora sericea

Magnified view of Cladophora sericea

While I was picking away at the algae, Rachel and Ann were turning over rocks looking for animals, and found a couple of different fish: the common Shanny (Lipophrys pholis), and the distinctive Five-bearded Rockling (Ciliata mustela), though it was only face-on that we could readily see all the barbels, one on the lower jaw and four on the snout.

Picture of Shanny (Lipophrys pholis)

Shanny (Lipophrys pholis)

Picture of Five-bearded Rockling (Ciliata mustela)

Five-bearded Rockling (Ciliata mustela)

The crab collection turned out to be even better. Lots of Green Shore Crab (Carcinus maenas) were lurking in the pools, along with the occasional Edible Crab (Cancer pagurus).

Picture of Edible Crab (Cancer pagurus)

Edible Crab (Cancer pagurus)

Rachel then started finding the rather more fierce Velvet Swimming Crab (Necora puber), including a really big monster, which she proceeded to pick up while it demonstrated how tight a grip it can have on the nearest object.

Picture of Velvet Swimming Crab (Necora puber)

Velvet Swimming Crab (Necora puber)

The final crustacean was completely invisible against the sand: the Broad-clawed Porcelain Crab (Porcellana platycheles) was also rather small, and bore very hairy pincers, making it usefully easy to identify.

Picture of Broad-clawed Porcelain Crab (Porcellana platycheles)

Broad-clawed Porcelain Crab (Porcellana platycheles)

Not everything we found was that easy, though. The green algae pretty much always need checking under a microscope since there may be several superficially-similar species.

Picture of Ulva intestinalis

Microscopic view of Ulva intestinalis

The most tricky, though, were the red seaweeds in the genus Ceramium. They are relatively small and fine, but have stripy bands along their length and pincer-like ends to their fronds. Some may also have (very short) spines. Others can be differentiated based on the degree of stripiness, the number of bands between nodes, the extent of the curvature of the ‘pincers’, the number of periaxial cells (for which a transverse section is necessary) and various other features. All this makes for quite a challenge when trying to work out what a given species is. I’ve certainly found a couple of the spiny species at Birling Gap before (C. echionotum and C. gaditanum), though the samples from the recent visit were something different. We’re still awaiting confirmation on these, but the ones we found could be: the distinctly banded C. deslongchampsii; the regularly and distantly divided C. secundatum; and the more frequently divided C. virgatum.

Picture of Ceramium deslongchampsii

Ceramium deslongchampsii?

Even though the species mentioned above are only a portion of the total that we uncovered, there are clearly many more organisms lurking in our local(ish) marine environment that we need to discover. We’ll have to go back in the spring.

Finally, if you want to collect seaweeds and press them, this is how you do it. Remember, they will need to be kept in the dark once you’ve pressed them, otherwise they will lose all their colour.

and here are some of the results:

Picture of pressed seaweeds

[1] See the notes by Jan Light ‘A Guide to Limpet Identification for the general naturalist’ British Marine Life Study Society http://www.glaucus.org.uk/Limpets.htm

[2] There is more on seaweed diversity in the piece I wrote after going on a British Phycological Society course earlier this year: “Marine Algae in Devon.” Diversions in Natural History. 14 Mar. 2016. Web. <https://diversionsinnaturalhistory.wordpress.com/2016/03/14/marine-algae-in-devon/>.

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