Blue Ocean Institute

Aug 31st
2010

Jamaican coral reefs, part 2

In the post below I highlighted one experiment that Amber is doing to investigate the impact of coastal development on coral reefs. A second experiment involves a sponge survey, where she compares species composition (i.e. how many species, which types), sponge abundance and size patterns between an impacted location and two control or non-impacted locations. Sponges are filter feeders, meaning that they pump in and filter seawater (and food), which makes them very good animals to test for water quality on coral reefs.

Smiley sponge; sponges suck in seawater via small holes on their sides and expel the filtered water through large holes, in this case the “mouth” and two “eyes”

The sponge survey was a massive undertaking, taking 5 field trips spaced over 1½ years to do sixty 20 m2 transects. [A transect is an area that is surveyed, with its length measured using a tape]. Each transect took between 60 and 90 minutes to survey, as all sponges had to be counted and measured. Because of dive-time limitations, each diver would start from opposite ends of the transect line and work towards each other.

Amber measuring a rope sponge using a tape measure, with the information recorded on the white clip-board below her. The transect line is the thin white line lying on the seafloor behind her

Approximately 4000 sponges were measured, representing over 60 species. There is a rich diversity of sponges on Jamaican coral reefs, as there is throughout much of the Caribbean. Sponge species ranged from bright yellow to fluorescent violet, and came in many shapes and sizes ranging from encrusting species ½ inch long to massive, barrel sponges over 5 ft high.

The large barrel sponge Xestospongia muta is reasonably common, and conspicuous, on many Caribbean coral reefs; this large individual is possibly several centuries old

After 10 days the field trip was over. We collected a lot of data, which will take many months to analysis to help us determine the impact of coastal development on coral reefs. Working in Jamaica is always an incredible experience, with good diving (when weather allows), amazing sights, and friendly and helpful people. Below are some extra photos taken during our time in Jamaica.

Arrow Crab hanging out at the “mouth” of a sponge

Two Banded Coral Shrimp

Endless horizon; good seas for diving

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