Lions and sparrows
Monday | August 15, 2005
In the galley of the White Holly there is a big sheet of paper taped onto the wall. On that paper we note all the large animals we see during our dives, that is, the species that can attain sizes greater than one meter. Using a terrestrial analogy, there are very few lions in our list, and our surveys are overwhelmingly dominated by sparrows.
We now have a list for 11 days of diving in Kiritimati and Tabuaeran. The space corresponding to Kiritimati is sadly empty, with the odd manta ray, green turtle and white tip shark. In Tabuaeran we have seen these and a few more, including one gray reef shark, three nurse sharks, a few large groupers, Napoleon wrasses, and a few bumphead parrotfishes. Surprisingly, we have seen Napoleon wrasses in all of our 25 fish survey dives in Tabuaeran.
As we pointed out in previous dispatches, Tabuaeran is an improvement from Kiritimati, although these are poor statistics compared to the 20 sharks per dive that Jim Maragos saw here in 1972. Despite a small human population, the lions are already threatened.
Dead coral in Tabuaeran is covered by a pink crust of coralline algae and a small turf of red algae cropped as meticulously as the green in a golf course. This is a result of grazing by abundant small-sized surgeonfishes. These surgeonfishes form virtual squadrons swimming over the reef, diving like kamikazes over a dead table coral, scraping every square inch of it, and swimming up again searching for a new surface to attack. This continuous grazing provides ideal conditions for coral larvae to settle on the bottom and develop new colonies. The sparrows of the reef are thus facilitating its rebirth.
The question follows: what are the consequences of the loss of the large animals? The only way to answer this question is by diagnosing the state of the entire reef ecosystem in a place like Palmyra atoll, where sharks appear to be abundant, and compare it with the reefs we have visited until present.