On Board the OSV BOLD: Sediment Sampling in Paradise

For more than a month, EPA’s Ocean Survey Vessel (OSV) Bold is studying the health of the waters around Puerto Rico and the U.S. Virgin Islands. EPA scientists and non-scientists will blog about their research and what it’s like to live and work at sea.

About the author: Doug Pabst is the chief scientist for the OSV BOLD’s Puerto Rico voyage. He leads the dredging, sediments and oceans team in EPA Region 2, comprising New Jersey, New York, Puerto Rico and the U.S. Virgin Islands.

Feb. 17, 2009 – 8:00 pm (Day 9)

We left Ponce at 6 a.m. and conducted more bongo net tows several miles offshore of Guayanilla, Puerto Rico. After the tows we proceeded west towards La Parguera to conduct sediment sampling operations.

La Parguera is a small fishing village in the town of Lajas on the southwest coast of Puerto Rico. The waters off La Parguera consist of small coral encrusted islands topped with mangroves. It is also home to Phosphorescent Bay, where at night the water will glow brilliantly when disturbed. This is caused by a small organism (a dinoflagellate) that lives in abundance in the area and glows when subjected to movement, similar to a firefly. This place is like paradise, with its natural beauty and picturesque tropical settings. I can see why some license plates here bear the slogan “Island of Enchantment”

We decided to anchor the OSV BOLD and use our smaller rigid hull inflatable boats (RHIBS) to conduct the sediment sampling. The OSV BOLD will serve as our platform to process and store the sediment samples. We dropped anchor at approximately 1 p.m.

image of round, flat sieve with grainy sediment in the bottomWe broke up into three teams. Two teams sampled in the RHIBS and one team stayed on board the OSV BOLD to process the sediment samples collected by the other teams. We will analyze the sediment samples of sand, silt and clay for grain size, total organic carbon (TOC), and benthic community analyses (organisms that live at the bottom of the ocean). The grain size and TOC samples are placed into a refrigerator and will be shipped to our lab for analysis. The benthic community samples are placed into a sieve, small round pan with a 0.02 inch (0.5 mm) screen on the bottom.

four specimen jars with pink water and sediment in bottomThe remaining material is gently scooped into a plastic container. The contents are preserved and stained, which allows for easier identification of any organisms. We then wrap electrical tape around the lids to further prevent leakage of the preservative. Our results will be utilized to help better protect and preserve the coral reefs and their associated ecosystems.

We ended the day with additional bongo net tows for marine debris off of Cabo Rojo. We’re schedule to do more bongo net tows at 6 a.m. and arrive at Mayaguez around noon. We will be in Mayaguez the rest of the day on the 18th and open to the public for tours from 8:30 a.m. until 4:30 p.m. on the 19th.