Underwater Fluorescence

It has been three months since the last blog post so high time for an update. I have not been out much as the weather has been grim. In fact, the photos in this post are one year old! I bought a blue LED light for fluorescence photography which has been gaining popularity in recent years. Many organisms and fluoresce (i.e. absorb light and emit it at a longer wavelength), although the function of this is generally not well-understood (perhaps in some cases it might not even have a function and just be a byproduct). Coral reefs can especially be spectacularly fluorescent but the cold waters of the UK harbour a variety of fluorescent organisms too, most notably anemones and corals, see here for great marine fluorescence photos from Scotland by James Lynott. Anyway, I bought my light and a yellow barrier filter (which serves to let the emitted fluorescent light through but not the blue light) to be held in front of the camera housing, as well as a headset barrier filter from a very knowledgable German chap here; his site contains a lot useful information for those interested in the background and applications of this type of photography (see also here, here and here). The photography is very tricky: the ISO needs to be bumped up in the dark which results in a lot of noise. The dark also requires long shutterspeeds which results in shaky images. A large aperture for more light is best, but since the subjects are usually small this results in suboptimal depth of field.  I have only been out twice last January, and only whilst rockpooling (I have not done a single nightdive or nightsnorkel in Cornwall and I am not overly tempted to do so!). The very shallow rockpools high up at Castle Beach in Falmouth reveal some fluorescent animals, including hermit crabs but I focused on anemones. Snakelocks are big and very fluorescent (the green ones, the grey variety is not, although it does emit red light via its symbionts) but not common high up the shore. Hardly visible normally due to their small size and inconspicous colours, red-speckled anemones, daisy anemones and gem anemones become apparent using a blue light (in fact, this method is use to study tiny coral recruits in the tropics). The top photo shows two green gem anemones Aulactinia verrucosa (with red and purple coralline algae in the background). The anemones are very small (2 cm max) and I used my CMC-1 wetlens on my Canon G16. The other two photos show Daisy anemones Cereus pedunculatus. I only later noticed the tiny anemone babies (this is a livebearing species). I hope when the rain and wind disappear and the evenings still start early to go out again and post some more photos. Also, I have bought both a new camera and a new aquarium so I have plenty more to post about!

a tiny rock pool part II

img_5088I recently sat down at a very small rock pool high up on the shore on Castle Beach in Falmouth. Just sitting down and concentrating on one square meter for a bit is essential to discover small organisms (see also this old post). If you want to end up with some half-decent photo’s, it is essential to go back several times to the same spot too, so that is what I did. The pools in this spot are very shallow, too shallow to stick your head in and look through the view finder, and often too shallow to even get the camera submerged. Biological diversity this high up the shore is relatively low. Common in these pools are periwinkles, flat top shells and thick top shells, beadlet anemones, prawns and shore crabs, as well as Serrated wrack and a diversity of small red seaweed species.img_6053Along with Shanny’s, juvenile Montagu’s blennies Coryphoblennius galerita are very common here (larger individuals must move to deeper pools lower on the shore). I only saw fish between 1.5 and 2.5 cm, tricky to photograph, I need a macro lens! Looking more closely, this tiny pool harboured snakelocks anemones alongside the beadlets, as well as a tiny Gem anemone Aulactinia verrucosa. img_6532img_6146img_6076-copy-copyimg_6642