Jarvis Island: Clinching the Argument

The Hanse Explorer departed from Washington Island Tuesday evening and arrived Thursday morning at Jarvis Island. So doing it transported the researchers from heavily populated Washington to uninhabited Jarvis, from human-impacted reefs to reefs that are truly spectacular. The next few posts tell of the sharky-ness and of the importance of the reefs at Jarvis Island.

Healthy corals at Jarvis Island extend as far as the eye can see, from the reef to the abyss. Photograph by Forest Rohwer.

by Forest Rohwer, head researcher on the Microbe Team

Jarvis is about as cool as a coral reef gets. The diving is done on coral walls that plunge, literally, to the abyss. The water just off the reef is that striking deep blue of the open ocean. Everytime we get in the water, there are sharks everywhere. Schools of 50+ black jacks pass right next to us and there are thousands of anthais—those brilliant quintessential reef fish— darting up and down off the reef.

Jarvis is important to our research effort because one critisism of the first Line Islands Expedition (2005) was that local oceanographic conditions could be the cause of the observed coral decline at the inhabited islands. There are a large number of reasons why this critisism is unfounded, but the best airtight evidence is Jarvis and the other Southern Line Islands. Every one of these uninhabited coral reefs has large numbers of predators, low numbers of pathogenic microbes, and high coral cover. That is, they are most like the more northern but uninhabited Palmyra and Kingman, even though they are found over a very wide range of different oceanographic conditions. Conversely, all of the inhabited islands surveyed (Christmas, Fanning, and Washington) are characterized by an almost complete absence of sharks, more pathogenic microbes, and declining coral cover.

Sharks and corals at Jarvis Island. Photograph by Forest Rohwer.

It is pretty simple: degradation of coral reefs in the Line Islands is tightly coupled to human activities. Local oceanographic conditions do not explain the differences in reef health that we and others  have documented. Jarvis and the other uninhabited islands provide us with a unique view of how coral reefs should look and function, and what we have seen there is spectacular.