Presented by Lewis Bambury and Gordon Fletcher of the local area group, these talks on the 12 June 2013 at Capernwray Dive Centre looked at some typical dive sites in the North West of England.
Gordon introduced the topic with reference to the local geology, which was completely re-modelled by the last ice age. Offshore this leaves three dominant ecosystems – extended, shallow, muddy plains dotted with the remains of drumlins which provide a scatter of ill-sorted boulders and pebbles, plus the Lune Deeps – a U-shaped glacial valley that reaches depths in excess of 60m. The fine sediments make for difficult diving conditions, as witnessed by Lewis’ introductory slide, and a diver interested in marine life needs to acclimatise to an environment that is nearly monochrome, covered in a fine silt that lifts into an impenetrable veil with the slightest fin kick.
Above: approximate location of the Hebe at the entrance of the channel to Preston Docks.
The ecosystems, while shallow, are dominated by animal life due to the fine suspended silt that cuts off the sunlight needed by seaweed. The mud is inhabited by secretive, burrowing worms, molluscs and crustacea – species we don’t see on most popular dive sites. Where a solid substrate is provided either by a wreck, or by a boulder scatter, the species mix is dominated by hornwrack (a common find on the strand-line around the Bay), with sponges, anemones and hydroids also being abundant. Lewis’ photos showed the dramatic difference between the mud plains and the site of the Hebe, a steamship stranded on Horse Bank 11th December 1911, with the plains apparently featureless with the odd worm-cast, starfish or antenna hinting at the presence of life beneath the surface, whilst the old iron plates of the Hebe bloomed with a profusion of plumose anemones, with mussels and hydroids filling any available gap.
Lewis thanked Darwen Sub Aqua Cub (based near Blackburn) for inviting him to join them on visits to the Hebe and the Lune Deeps.
The talk was prefaced by a short introduction to our beach-clean program by Jo Kaye. The next beach cleans at Half Moon Bay are scheduled for Sunday 16th June and Saturday 21st September 2013.