Did you know that some corals GLOW under ultra-violet light? Well they do! And last night some of us at A Rocha Kenya set out to see the amazing phenomenon for ourselves.
Conditions were perfect for some late-night rock pooling, so we headed out to the pools we knew had a lot of coral, and armed with torches and a small UV light. We were not disappointed! The corals glowed spectacularly, and we even saw some moray eels and a Spanish Dancer nudibranch as well!
To be truly accurate, it’s not actually the coral itself that is fluorescing (giving off light), it is the zooxanthellae living IN the coral! Tiny little algae live with coral and give it its color during the day, and some re-emit light to get spectacular displays like this. The coral and the zooxanthellae rely on each other to live: essentially, the zooxanthellae provides food and the coral provides shelter. Without that relationship, we wouldn’t have beautiful coral reefs, or nighttime displays like this!
People don’t know exactly why this “glowing coral” phenomenon happens, but there are a lot of interesting theories. One theory is that the fluorescent molecules work sort of like sunscreen!
Whatever the reason, we certainly are lucky at Mwamba that all of this is right in our own back yard.
This week I stumbled across a little toby (relative of the pufferfish) which I had never seen before. It was very camouflaged against the rocks and seaweed, and even after much examination of the photos I got of it I was unable to identify which species it is (if you know please tell me!). Besides the excitement of (potentially) a new species for Watamu Marine Park, I was struck by one photo of a close up of its face how beautifully colourful and detailed it was. Pinks, blues and greens close-up, but browns and greys of seaweed from afar. A remarkable little thing.
Hi to all! I’m back in Kenya and feel I need to make up for my lack of communication by showing you not just one, but three photos of the week. Already I have been back out to sea, specifically taking photos of every different kind of coral I can in order to build a species list of corals for Watamu Marine Park. To identify corals reliably to species it’s necessary to look at the tiny detail and structures of the colonies, often looking at the individual coral animals (coralites) themselves. Below are three corals I have found with close ups of the incredible patterns and structure they exhibit, at a scale most of us would never notice.
The coralites of this Goniastrea extends their fleshy body parts during the day (most corals only do this at night) creating an impression of a miniature flower garden swaying in the waves.
The coralites on the branches of this Acropora are enclosed in small cups facing upwards to the light, their food source and growing out towards it.
Gardineroseris is covered in small grooves and valleys in a complex, but ordered pattern.
Incredible diversity on one small patch of reef in Watamu Marine Park. In this photo there at least 8 genra of coral all crowded and competing for sunlight. In the centre and bottom left there is Pocillopora, the bottom right is some encrusting Montipora, above this a small green patch of Galaxea. Along the top there is the winding lines of Platygyra on the left, next to a yellow branching Acropora, nestled next to a smooth brown Porites in the top right. In the middle there are two domed corals with circular coralites (pits) which are most probably Favites and Favia, although a closer look would be needed for these two. How and why all these corals are crowded together is difficult to know and as complex as any rainforest structure, with canopy Pocilloporas and Acroporas, which an understorey of creeping Monitpora and emergent Porites bursting through the structure to form smooth domes.
The Convict Surgeonfish (Acanthurus triostegus) is a convict in both form and behaviour. It was presumably given the name because of its distinctive pale yellow and black stripy colouration similar to that of uniforms that criminals wore in times gone by. However, these fish are also convicts because they are the raiders of the reef. Like most Surgeonfish they are herbivores, feeding on turf algae found on the reef, but unlike many reef fish they don’t maintain territories. Instead they move in large shoals, descending and overwhelming a resident fish, rapidly eating all the algae in its territory and then moving on. They may appear to the untrained eye to be an innocent shimmering of stripes zipping around the coral heads, but for reef inhabitants they are no good hooligans!
This week’s photo is the open mouth of a stunning blue Giant Clam (Tridanca maxima). These giant molluscs, related to snails, octopus and mussels, have given up traditional bivalve filter feeding on microorganisms living in the water column, but instead have developed a close relationship with their former prey. Single celled phytoplankton, a major food source for most bivalves, are resident in the clam’s flesh giving a range of striking patterns and colours, but more importantly fixing sunlight into sugar molecules through photosynthesis which the clam then feeds on. In return phytoplankton receive waste products and Carbon Dioxide from the clam which helps them grow. In addition to the corals themselves, the clam is one of many many examples of Symbiosis, or living together, seen on coral reefs where cooperation between unrelated organisms pays off and over many years ends up being a permanent new hybrid organism. It just goes to show how a little cooperation can be very useful!
Allard's Anemone Fish
The photo of this week is of a beautiful Allard’s Anemone fish nestled in its anemone home. Made famous by the film Nemo, clownfish or anemone fish are a well known coral reef inhabitant, of which we have two species in Kenya along with the Skunk Anemone fish. Their ecology of living in symbiosis with an anemone is a great example of the incredible complexity and inter-reliance of coral reef ecology, where no single species can live without the others. It is this complexity which makes reefs so vulnerable to human destruction where one influence has many ripples through the entire reef community and is the challenge of marine ecologists to understand these complex interactions.
Time has really raced the last few months for the marine team. Starting in January, Joy Smith an Oceanographer from Virginia, USA, joined me (Benjo) and together we really pushed forward with data collection on the reef. However all too quickly we’ve come to the end of this year’s field season, with weather set to get windier and the sea to get rougher from April through to September during ‘kusi’ monsoon. I’m now sitting in a coffee house in Nairobi thinking about all those wonders way down on the coast and realising that none of the magic of the reef has been lost. Below are a couple of photos from the last snorkel I did around a site we call ‘the larder’. A huge shoal of trevally completely surrounded us and beautiful sweetlips swam lazily over to figure out what these strange new creatures in their home were.
A final piece of news is that nearly all the plates we put down in December are now out of the water. I say nearly, because sadly we couldn’t find one of the plates placed in Kanani, but nevertheless recovering 35 small pieces of equipment that have been sitting on a large underwater landscape for 3 months is quite successful I feel. We did the work in collaboration with Kenya Marine and Fisheries Research Institute (KEMFRI), which not only being another great contact for future work, but was a lot of fun for the three days we were zooming around the park and pulling the plates up. Juliet from KEMFRI started helping us analyse the plates looking at the major types of organisms settling. While I could see some little corals on the plates, we need to use a microscope and Juliet’s expertise for a longer period of time to get the final results of this interesting study. The plates are stored and can be analysed at any time in the future, so all the more to look forward to for the next field season!