Coralline algae, pink and purple, feathery or encrusting, are a conspicuous part of the local rock pools. When viewed close up, even the crusts are not boring, as they reveal little stalks and holes forming reproductive structures. The above species could be Common pale paint weed Lithophyllum incrustans or Common purple paint weed Phytamoliton purpureum; it is hard to tell species apart and there are likely more species than the few described on websites or in books. In the third photo, the thinner crusts are probably Phymatolithon lenormandii. Only when looking at close-up photos it becomes apparent that juvenile limpets (Patella spp) and White tortoise shell limpets Tectura virginea are very common.
Coralline algae are desirable in tropical reef aquariums, as they cover the brownish live rock in pretty colors. There are even special supplements for sale to promote their growth. They need low phosphates and sufficent calcium (as well as magnesium) to grow well, just as hard corals do. Good light helps, although there are also species that thrive under low light. I have a bit of coralline algae in my tank, but only in spots with high flow, so that seems important too. It might be a nice experiment to take a small tank, with a good light source and a decent pump (with rowaphos to keep phosphates down), and add some coralline algae-covered rocks to see what happens. Doing frequent 100% water changes will replenish calcium and magnesium, and not adding animals and food will keep nutrient levels minimal. With some interesting rock formations, it could develop into something pretty.
The species Titanoderma pustulatum grows on other seaweeds, such as Irish moss Chondrus crispus on the photo above. Pink plates Mesophyllum lichenoides are coralline algae that are very common on the mid- and lower shore here in Falmouth. They look a bit like a miniature version of Montipora corals. At the moment, some individuals are covered in knobbly reproductive structures housing spores. Pink plates grows epiphytically on Common coral weed Corallina officinalis, the species that makes up the bulk of the coralline algae in the rock pools (see second photo of this post, on the right). Slender-beaded coral weed Jania rubens is also quite common at the moment. Corallina and Jania can be seen growing side by side in the second-last photo. Jania here grows epiphytically on Hairy sand weed Cladostephus spongiosus (this species is normally fuzzy but in winter the branches are bare and slender). I hope to go diving soon and take more photos of the most ‘spectacular’ coralline algae: maerl.
Tag Archives: Mesophyllum lichenoides
a tiny rock pool
Last weekend I went down to Gylly Beach in Falmouth for a bit of rock pooling. However, the tide was not very low (especially with the inshore wind) and the weather was crap. Moreover, I could not find anything that I had not seen many times before; although rock pool life is very biodiverse, there have started to be dimishing returns when looking for non-microscopic organisms. Clambering over yet another rock, I decided to stop and play around with my Canon Powershot instead. I focused on a tiny pool (around two by four feet) completely covered in corraline algae. 
It does not look like much but taking the time for a carefully look was really rewarding. It is tricky to take photographs without being able to see the viewfinder though. My strategy has been to just take loads of pictures and hope some of them work out. The miniature underwater landscape was really beautiful. Pink plates Mesophyllum lichenoides made up the largest proportion of corraline algae (some bearing ‘reproductive conceptacles’). Another species is Corallina officinalis or Common coral weed (third photo). I had some Corallina growing in my aquarium at some point, but it grew very slowly and has now disappeared. Being able to create the right conditions for coralline algae to thrive in a coldwater aquarium would be fantastic, but I have not seen any evidence of anyone being able to cover their aquarium in them yet. (I have tried ‘planting’ Corallina and although it looked very nice at first (fifth pic), these seaweeds quickly died off, turning orange and then white (second pic).)
Some other seaweed species were present as well; Irish moss and Harpoonweed (not pictured), False eyelash weed Calliblepharis jubata occurred in multiple patches, Rhodophyllis divaricata?, an Osmundea species and Red grape weed Gastroclonium ovatum. There were also a few brown seaweeds, the characteristic Thong (or Spaghetti) weed Himanthalia elongata buttons and the invasive (and pervasive) Wireweed Sargassum muticum.
I did not spot too many animals, although I am sure there is an enormous hidden diversity present among the seaweeds. I noticed a red-white Dahlia anemone Urticina felina as well as some patches of a colonial brown tunicate. I’d like to go back soon and take some more pictures, with my Canon powershot or with my GoPro. I have an SLR as well that I have not been using lately as my iPhone is such a good camera and hassle-free. SLR underwater housings are really expensive, but I recently discovered that there are quite cheap waterproof SLR bags available which might be an option to try to take higher quality photos (in rock pools, I would not go diving or snorkeling with them). It would be very cool to try to make panorama pictures of rock pools, especially when taking one each month in the same spot to capture seasonality. More seaweed photos, Canon powershot or otherwise, to follow soon!
rock pooling from the comfort of my home
It was too cold and windy to spend a lot of time on the beach, so I took a closer look at my seaweed catch back home. I was amazed at the diversity of organisms growing amidst the weeds. A lot of them are easily overlooked when rock pooling as you need some time (and preferably a comfortable seat) to find them. Below Bushy rainbow wrack with epiphytic False eyelash weed and Pink plates Mesophyllum lichenoides (I will not give the Latin names of species described in preceding posts for brevity). Some bright green sea lettuce Ulva, a grey topshell Gibbula cineraria, a snakelocks anemone Anemonia viridis and in the middle a bright orange colony of the tunicate Botrylloides leachi: 
I found many large Breadcrumb sponges Halichondria panicea but the picture I took did not turn out to be in focus. I do not know what the organism below is, perhaps a bryozoan (please feel free to comment!). 
I am not sure what this is either! 
Dog whelk Nucella lapillus eggs (I now also notice a tiny brittle star in the middle): 
Egg cases of the thick-lipped dog whelk Hinia incrassata: 
A small snakelocks anemone; interestingly enough all of these were the green variant (with purple tips) and there were none of the pinkish ones. I have read some interesting notes about aggressive behaviors between the two types, something to look into for a future post. 
A Marbled Crenella Modiolarca tumida, a tiny bivalve typical of seaweed holdfasts: 
A tiny White tortoiseshell limpet Tectura virginea: 
I saw something creeping out of the seaweeds on the floor out of the corner of my eye: a small Long-legged spider crab Macropodia rostrata. This species adorns itself with seaweeds for camouflage: 
An Bollenessor 