Just like trees, corals accumulate rings as they grow. This is a cross-section of a deep sea coral, glowing purple under ultraviolet light.
Just like trees, coral growth changes based on temperature, light and nutrient availability — and these fluctuations are reflected in their growth rings. Scientists can use these cross-sections to study past ocean climate!
Photomegatron Maps Coral Reefs
Traditionally, marine scientists would gather data on corals by photographing and measuring a one square meter area or quadrat. That method gives consistent data on a coral area over time, but it’s also a very small area … so scientists are trying out new methods like this one. It’s affectionately called the PHOTOMEGATRON. It’s two Nikon SLR’s, mounted in a protective frame with lasers.
A researchers swims it over the reef as the cameras record coral cover. The images are assembled later to create a comprehensive map that includes larger coral formations that would be missed in the quadrat system.
What an excellent question Anon. I have on myself. Where were you diving when you saw this?
You are right in thinking that they are part of the natural reef community - they drive coral reef biodiversity and drive ecological succession, preventing the fastest growing species from dominating.
The population density of COTs that constitutes an outbreak is still debated. Populations of 140/ha to 1000/ha have been reported as outbreaks, whilst populations of 100/ha are reported as low.
The cause of outbreaks is still deliberated, but we do know it’s multi-faceted. Populations bloom and crash naturally, but this is definitely exaserbated by the harvesting of it’s natural predators the Triton Shell (Charonia tritonis) and Harlequin Shrimp (Hymenocera picta) which are two of the few natural predators able to cope with their venomous spines.
Fish feeding is though to have an impact - full of bread (or whatever) they no longer eat their natural foods, which for some species include COT larvae.
COT larvae feed on unicellular flagellates - phytoplankton - so the more plankton in the water e.g. near coastal run off of nutrients, the higher the change of a population bloom.
COT collection dives have been common in the past. Physically collecting individuals off the reef and killing them on land. It’s hard not to react when you see the immense damage they can cause on a reef in just days. However, some say that rough handling of pregnant individuals cause them to release their eggs into the water. Whether they are fertilized or not, we don’t know. Plus, untrained divers may damage coral and other marine life in the collection process.
Injecting individuals with sodium bisulphate is becoming more common and is thought to be a more effective mechanism - it being fatal for COTs but not to the surrounding environment.
I couldn’t tell you the perfect solution to the problem, but I can tell you that the venom hurts like a bitch. For a few days anyway.
Read more COT posts:
What kind of tourist, comes to another country [in this case Philippines] and carves a patriotic message on a piece of coral? It is disrespectful on SO many levels.
People should be made aware that corals are animals! Not only are they living, but they are an essential resource for that country, peoples lives depend on the productivity of coral reefs.
It makes me sad that this level of ignorance exists in this world.
Yes, I’m a marine biologist, but currently, by trade, I’m into all tropical biology. Rainforests, Mangroves, the Inter-tidal zone. So let’s have a bit of a wonder through them shall we?
Not to mention, all ecosystems are linked. Things that affect the Rainforest trickle down through the mangroves, over the seashore and into the sea. So it’s all relevant really!