Friday, May 23, 2008

Blog #3: Giant Sea Stars

Giant sea star found 87 feet deep near Madagascar

One week into our survey and we have catalogued close to 1000 different invertebrates (mainly echinoderms, mollusks, and crustaceans) and between 350 and 400 fish species. How many are new to science remains to be determined with the help of DNA sequencing and comparison with museum specimens. Certainly some will be new records for Madagascar.

Much of the area near our base of operation on the island of Nosy Be is shallow continental shelf, with maximum depth of 120 feet though possibly some deeper areas. For the most part we have been working the shallows, areas with extensive reef coral development and rubble produced by the devastating effects of cyclones that periodically hammer the coastline. Coral rubble is a gold mine of invertebrates; it has a lot of niche space in which all kinds of animals can take cover. Although our search for undocumented species in this habitat is far from exhausted, much of what we are seeing is becoming familiar from previous dives. So today we headed out to the deeper waters for some "muck diving."

We chose at random a site in the middle of the channel separating the islands, and followed the anchor line down to the bottom. The site turned out to be a fine muddy benthos at 87 feet. My first impression of this habitat was of a barren seascape, with not much to see but mud and detritus. Certainly there is neither the explosive color nor obviously high species diversity found on coral reefs. Upon closer inspection, however (which had to wait for the dust to settle that was produced by the action of my dive buddy's fins kicking up the mud) we discover many amazing an unusual animals that thrive in this kind of habitat. Among our discoveries today were giant sea stars we have not found elsewhere, some measuring two feet at their widest.

Our Malagasy colleagues, who have been diving here for decades, admitted this was the first time even they had seen these species. Few divers and even marine biologists venture out into these less "pretty" underwater environments, but clearly those that do are rewarded with unique wildlife only observable off the beaten path.

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