Coral reefs are some of the most beautiful geological and ecological formations this planet has to offer. Corals are formed by small animals. Each coral animal is like a little bag. The opening on top is the mouth. Tentacles around the mouth carry stinging nematocysts, which paralyse the small animals eaten by the corals. Milne Bay has an extremely high reef coral diversity and has been named the largest expanse of relatively pristine coral reefs in the central Indo-Pacific. It is an Eldorado for divers and fishermen.
However, corals are in danger! When corals are stressed by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae living in their tissues, causing them to turn completely white.
The more technical definition of "coral reef" includes an additional geological requirement that the reef organisms produce enough calcium carbonate to build the physical reef structure. The coral reef community lives only on the surface veneer of the reef, on top of already existing skeletal material left behind by previous reef-builders. Many processes act to break down the skeletal material and reef as soon it is laid down by organisms. These include mechanical processes such as waves and currents, and a wide array of biological processes (e.g., bioerosion). Some of the best known bioeroders are large organisms such as parrotfish and sponges, but much of the bioerosion occurs at the microscopic scale by organisms such as algae and fungi. A coral reef is produced only if the coral reef community produces more calcium carbonate than is removed. Indeed, some coral reef communities grow too slowly to build a reef.
The geomorphology of reefs largely reflects two main variables: relative sea level rise and the nature of the underlying substrate. Reefs are commonly classified according to three main reef types: fringing reefs, barrier reefs, patch reefs and atolls.
- Fringing reefs grow near the coastline around islands and continents. They are separated from the shore by narrow, shallow lagoons. Fringing reefs are the most common type of reef that we see.
- Barrier reefs also parallel the coastline but are separated by deeper, wider lagoons. At their shallowest point they can reach the water’s surface forming a “barrier” to navigation.
- Atolls are rings of coral that create protected lagoons and are usually located in the middle of the sea. Atolls usually form when islands surrounded by fringing reefs sink into the sea or the sea level rises around them (these islands are often the tops of underwater volcanoes). The fringing reefs continue to grow and eventually form circles with lagoons inside.
- Platform or patch reefs are small, isolated reefs that grow up from the open bottom of the island platform or continental shelf. They usually occur between fringing reefs and barrier reefs. They vary greatly in size, and they rarely reach the surface of the water.
The above has been adapted from wikipedia.org, eoearth.org & coral.org
To log this cache please answer the following questions:
1) What kind of reef is at the given coordinates. Do you think you can find all reef types in Milne Bay if you look long enough?
2) Coral bleaching is a global issue and some reefs are more affected than others. Has there been any coral bleaching here? Which of the above factors for bleaching would be the most likely cause for bleaching here if there was to be any?
I would be happy if you log with over and/or underwater photos. But it is not a requirement! I am also curious how and why you happened to visit Milne Bay province.
Beware! This is a remote area! You can reach the coral reefs by boat only. You can organize diving, snorkeling or fishing trips from the hotel in Alotau or the nearby resort. You may also be able to arrange private transport in Alotau from one of the fisherman. If you happen to only pass one of the nearby reefs I consider that a find as a guided trip may not pass the exact spot marked in the listing. Please add those coordinates to your log.