Patella
The Mersey water is turbid, so insufficient light reaches the bed to support algae below mid tide level. There is a sparse growth of Fucus spiralis and Enteromorpha spp. on the upper shore which supports Littorina littorea and a very few Patella vulgata (I only found 3).The dominant organisms on hard surfaces from upper shore to the sublittoral fringe are barnacles (At LW mainly Balanus crenatus with some Elminius modestus).
This image shows L. littorea and a lonely Patella on the upper shore at New Brighton.
ONCHIDORIS BILAMELLATA
With the abundance of barnacles to eat, one might expect plenty of Nucella lapillus, but I only found 6, on a breakwater. It may be anti fouling paint in the past that depleted numbers. However, a barnacle eating species which was present in thousands laying its spawn was Onchidoris bilamellata.
February and March are the main months that is does a mass migration from deeper water to spawn, so now is the time to look for it at LW. I've never seen it in such abundance as at New Brighton on 1/2/2010. The spawn was like patches of snow, but it is not a new phenomenon, as Cuthbert Collingwood' s account of 1859 shows:
Like Collingwood, I found it and spawn also at Egremont, but not in huge amounts there as the shore has lost most of the hard substrate of his day. I haven't checked out Monks Ferry where he saw it trampled by passengers.
Tergipes tergipes
Tergipes tergipes is too small to easily detect in the field so I collected half a bucket of hydroids tangled round debris. Examination under a microscope produced nothing as the hydroid was all dead. However, at Egremont I picked up a pebble the size of a duck egg from a muddy pool because it had a fuzz of live hydroid growth on it.
Examination under the microscope revealed a white spawn packet and, nearby, a Tergipes.
Aeolidia papillosa
I picked up several anemones for identification, and was pleasantly surprised to find one "anemone" was in fact an Aeolidia papillosa, which closely resembled some colour forms of its anemone prey.
Ancula gibbosa
While looking for Tergipes tergipes under the microscope I found a tiny (2mm) specimen of Ancula gibbosa on growths scraped from an old sand bag lying at LW at New Brighton.