Monday, May 26, 2008

Blog #4: More Muck Diving

Cruising along the muddy bottom we occasionally see isolated soft corals or sponges rising up from the benthos (bottom dwelling flora and fauna). In the absence of reef and rock, these animals provide the living space for many other smaller creatures. We sampled a hollow-stemmed gorgonian coral only eight inches tall that yielded over 100 individual crustaceans and represented at least seven species.

This is one of these gorgonians:

And this is a sampling of the crustaceans recovered from a single pink individual:

And what of the sea cucumbers from these deeper murky waters? We saw only two during our dive, but one was an encouraging find. It was Holothuria scabra, one of the two or three most heavily exploited and high-value species occurring in Madagascar (shown below). The typical price in Singapore for this species in 2003 was between US$40-56 USD/kilo dried, but it would not be unusual to get over $100/kilo in other markets.

Sea cucumbers have been heavily fished for centuries as part of a multi-million dollar food trade, with China as the principal center of consumption. Not surprisingly, many of the large sea cucumbers are rarer in Nosy Be than would be expected to occur naturally. Certainly this reflects how heavy they have been exploited, and unfortunately around the tropics this is the norm rather than the exception. The deeper murky waters where we found this animal are more inaccessible to fishermen, and the best hope for many of these highly sought after species may be their ability to thrive in habitats farthest from their reach.

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.

Monday, May 19, 2008

Blog #2: Six-Foot Sea Cucumbers

I am taking a rare and short break from intensive ocean biodiversity sampling to write this entry. My base of operation is the National Oceanographic Research Center in Nosy Be, an island off the northwest coast of Madagascar. I am here with a team of marine scientists--Dutch, French, American, and Malagasy--who are engaged in an underwater assessment of coastal marine life in this part of the world. The project (BIOTAS) has the goal of characterizing the region's biodiversity (land and sea), and examining the natural processes that have led to the geographic distribution patterns among multiple groups of organisms in
the southwest Indian Ocean.

The above photo shows the center's lab space as you approach from the water. Inside this building is where our group works well into the night processing all the material collected during dives.

Among the researchers here are experts in fishes and invertebrates. I am part of the invertebrate team, and am studying the sea cucumber fauna together with Dr. Gustav Paulay and Francois Michonneau of the Florida Museum of Natural History. Sea cucumbers are echinoderms, a group of animals that includes starfish, sea urchins, brittle stars, and feather stars. There are "sea cukes" that indeed have the dimensions of a cucumber you might slice into a salad, though body length among this group of animals ranges from a few millimeters to over 9 feet, and some can weigh over 10 pounds. They are found from shallow shores to abyssal seas, and are probably the least well studied of all large and conspicuous marine animals. Roughly 1600 species are described, though many more remain to be discovered.

One fascinating characteristic of sea cucumbers is best seen under a microscope. Unlike starfish and sea urchins that construct large continuous skeletons observable on many a beach walk, sea cucumbers instead have thousands of tiny skeletal pieces or "ossicles" embedded mainly in their body wall. These ossicles take on ornate shapes as indicated by the descriptive names used for the various types: buttons, tables, rosettes, rods, etc.

During the first few days of our expedition, we have seen many synaptid sea cucumbers, such as the one photographed above (Synapta maculata). These long and slender cucumbers have a body wall about as thin as tissue paper, and a diameter about equal to that of a stick of pepperoni. Colors can vary from bright pinkish-orange to greenish brown with dark bands. We saw animals on this trip that were up to six feet long!

If you touch one, the point of contact adheres to your body like glue. This is not caused by any chemical adhesive, but the mechanical action of the animal's ossicles which are shaped like boat anchors. It is these anchors, occurring in the thousands along the surface of the body wall, that cause your hand or wetsuit to become stuck to the animal. (A quick flick of the hand will release you!)

Friday, May 9, 2008

Blog #1: A Three-Week Expedition is Underway

This weekend a team of researchers are taking off for Nosy Be, Madagascar. The northwest corner of the island has been identified as a biodiversity hot spot for both terrestrial and coastal marine biodiversity. The area is home to high numbers of unique forms of life and is under high environmental threat.

I will be among the researchers accompanying Dr. Gustav Paulay of the Florida Museum of Natural History on this mission. I will work with Dr. Paulay to collect samples of sea cucumbers and other species for biodiversity characterization at the organismal and genetic scales. Our contribution is part of a larger land-sea biodiversity assessment of the southwest Indian Ocean, coordinated by two researchers at the University of Reunion.

The broader study (BIOTAS) is seeking to not only characterize biodiversity in this part of the world but also to examine the natural organisms. The study will lead to greater understanding of how evolutionary processes shape species assemblage in the region and between its islands, and help identify conservation priorities.

My day to day routine will consist of diving, collecting and documenting species. I will be updating this blog from a satellite phone during the course of the expedition, and I look forward to sharing my observations on the invertebrate species we find.