Gelatinous growth on underside of rocks in River Thames

Gelatinous growth on underside of rocks in River Thames

Observation - Gelatinous growth on underside of rocks in River Thames - UK and Ireland. Description: The tidal Thames at Richmond is normally kept at quite a high level by barriers on Richmond Lock. These haven't been in place recently, so the river has been very low at low tide. We turned over some large rocks on the river bed, and found some covered in

The tidal Thames at Richmond is normally kept at quite a high level by barriers on Richmond Lock. These haven't been in place recently, so the river has been very low at low tide. We turned over some large rocks on the river bed, and found some covered in what looked like a gelatinous resupinate lichen, firmly stuck to the rock. These were only on the underside of the rock. Photo attached of a small piece, maybe 30mm across, but there were large growths on the same rock