Red Red Algae

During a recent walk around the Llangattock area, I took in the beautiful Craig-y-Cilau Nature Reserve, which follows a Limestone escarpment that leads into a wooded area. As I walked along I enjoyed listening to Ravens and Buzzards, and on the escarpment I could make out Aspen and the rare Whitebeam which I had studied closer earlier in the year.

However, along the section where I follow a stream downhill, I noticed a bright red colouration to some of the rocks in the water, and upon closer inspection I could see it was a type of algae. The colour really stood out, so I took some photographs to study in my books later at home.

I was pleased o find that this was a species of algae called 'Hildenbrandia Rivularis. 

Hildenbrandia is a genus of thalloid red alga which comprises twenty six different species. The slow-growing, non-mineralized thalli take a crustose form.

It grows at its margins, away from the centre, and is able to quickly repair any gaps arising by regenerating from a basal layer of cells. As the plants become more mature, they become multi-layered and strongly pigmented near their centres.  Multi-layered areas may develop in the margins; these will detach and float away as gemmae to form new colonies which would explain why the group I found was also visible on other rocks close by.

Unlike most other freshwater red algae (which prefer running water), this species prefers still water, particularly shady lakes or ponds which is (exactly how I found it. This section of the stream had formed little pools under the canopy of the trees, so it seemed the growing conditions particularly along this section were ideal for this algae.

It really stood out for me, and was visible from a short distance away, and as I looked down onto it, it seems to be glowing on the rocks in the gentle running water. It was certainly a new species for me and a very eye catching algae.

Picture copyright Neville Davies