Trip reports

Underwater Pembrokeshire.

Friday, 14 October 2011

On Friday October 14th, Dorothy Witcomb took the group to places we had never been before - underwater Pembrokeshire. Dorothy is not only a PhD, trained biologist but also an underwater photographer of note. This subject coincided nicely with the RSPB's campaign for the protection of the marine environment. No there weren't any birds but without this watery environment there would be no auks, no gannets, no seals and no fish and chips!
Dorothy took us on a graduated journey from the seashore to 30 metres down. As you go into deeper water the light loses colour - first we lose red, then in order yellow, green and lastly blue.
Most of the photos we saw were in St. Brides Haven. Gut weed lives on the shore and uses red light to photosynthesise. A proliferation of this plant means marine problems. At 2 metres red light has gone and we get wrack - channelled and bladder. At high water bladder wrack floats in long streamers to get sunlight.
At West Dale we saw rocks so covered in barnacles we couldn't see the original colour. The barnacle is a shrimp-like animal which comes out at high water and kicks it's food into it's mouth. The bright red periwinkle and sea anemones.
Below the low tide level lies a kelp forest. Kelp is a cold water plant and Pembrokeshire is the southern end of it's range. Grey seal were there. Kelp is "deciduous". It hold it's fronds and the food store therein overwinter, sheds them in spring and then grows new ones. We saw sea squirts and various crabs - spider, hermit and edible.
As we went deeper we encountered sea urchins. These graze on young kelp. In California, sea otters which eat sea urchins were killed for their fur. Sea urchins proliferated, kelp vanished and all the animals which fed and sheltered there were lost. The same happened in Newfoundland when cod was over-fished. Sea urchins may be used for sushi.
Deeper again at 20 metres were the echinoderms. Common starfish, "bloody henry", cushion star, brittle starfish and huge groups of feather stars.
Then at 30 metres with no light there are no plants. Filter feeding sponges such as the boring sponge were shown as were fish such as the orange cuckoo wrasse. Finally we saw various soft corals - dead man's fingers, sea ferns and sunset corals.
Finally instead of a sunset Dorithy left us with images of jewel anemones. These are a cross between corals and anemones. These were thumbnail sized creatures in a myriad of glowing colours
This was an evening of great entertainment and considerable education and thoroughly enjoyed by all there.