





Formation of Coral Reef Atolls

Biodiversity of Hotsarihie

As a result of his five year trip aboard the HMS Beagle, Charles Darwin proposed an explanation for the formation of coral reef atolls. He suggested that atolls are formed when corals grow around and ring oceanic volcanic islands. Over tens of thousands of years as the volcano sinks into the ocean, outer corals which continue to grow upwards to the level of the sea form a barrier reef while the inner reef falls behind creating a lagoon. Hotsarihie (which in the local language means Reef of the Giant Clams) is one such atoll. Helen Island is threatened with global warming and rising sea levels. The island itself is the uppermost part of a large sand dune that is shifting each year.Hotsarihie is incredibly rich in biodiversity. Female hawksbill and green sea turtles lay their eggs in the sand on Helen Island making the island a globally significant turtle nesting site. A variety of birds also live on the island including White-headed and Crested terns. Blue footed boobies also nest on the many large ships that have become wrecked on the atoll. Unfortunately this rich biodiversity attracts many poachers. To combat this illegal activity the government of Palau has a permanent marine ranger station on the island that is staffed at all times.1. Introduce yourself to one of the island’s rangers, find out the following information and submit it to me in an email (not in the log below):

a. How do they assist with the survival of sea turtles that nest on the island?



and



b. In what direction and by how much per year is the island itself shifting?

1. Upload a photo of yourself standing in front of the “Welcome to Helen Island ” sign.and2. Upload a photo of one of the following:

a. any of the numerous birds that nest on the island



or



b. any of the giant clams that one can see while diving in the area.

All logs without the required information sent to me by email will be deleted to comply with the EarthCaching requirements.