Science Wednesday: On Board the OSV Bold
Each week we write about the science behind environmental protection. Previous Science Wednesdays.
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. 13, 2009 – 8:00 pm (Day 5)
|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.|
The crew of the OSV BOLD spent today fishing with University of Puerto Rico (UPR) scientists and students. It’s not what you think; we towed bongo nets—they’re called that because the opening looks like the drums—behind the ship to collect floating marine debris (garbage, plant material, plastic, etc.) and plankton (small animals and algae).
Marine debris is a problem in oceans, coasts and watersheds throughout the world. It can result from human activities anywhere in the watershed, from an overturned trash can many miles from the ocean, or from litter left on a beach. Detergent bottles, plastic bags, cigarette butts, and discarded fishing line can become marine debris. Birds, whales, turtles, dolphins and other marine animals become injured or die by becoming entangled in debris or by confusing it with their natural food.
To collect marine debris, the bongo nets are towed through the water at the surface for 30 minutes or longer. We then retrieve the nets onboard and examine the contents. The UPR scientists also collect and preserve animals and algae in the bongo for counting and identification back in their laboratory.
Our first stop was off the north shore by Arecibo. The trade winds continued to blow hard, making our “fishing” all the more difficult. We continued west off the Rincon Lighthouse for more floatable fishing. Here we were more protected from the large ocean swells on the north coast. Several humpback whales appeared out of the water upon our arrival as if to say hi and welcome us to the west coast. Our last fishing stop of the day was off of Mayaguez. The good news, so far, is we found very little garbage. Our main catch was small jellyfish and the blue variety of a little animal called a copepod, which looks like a blue flea. We were treated to a spectacular sunset as we completed operations for the day and sailed east along the south coast towards our next mission off Jobos Bay.
Hunting for Treasure
Feb. 14, 2009 – 6:00 pm (Day 6)
The day started at 5 a.m. in the darkness off the Jobos Bay National Estuarine Research Reserve, a chain of 15 tear-shaped mangrove islets known as Cayos Caribe and the Mar Negro area in western Jobos Bay. The Cayos Caribe islets are fringed by coral reefs and sea grass beds with small beach deposits and upland area. The Mar Negro area consists of mangrove forest and complex systems of lagoons and channels interspersed with salt and mud flats.
The reserve is home to the endangered brown pelican, peregrine falcon, hawksbill sea turtle and West Indian manatee. It is commercially important for marine recreation, commercial and recreational fishing and ecotourism. The area is managed by the Puerto Rico Department of Natural and Environmental Resources and the National Oceanic and Atmospheric Administration, and our data will be provided to the two agencies to assist in their management of this important and beautiful area. Our main goal is to map of the seafloor south of the reserve.
We towed the side scan sonar, which resembles a small rocket, off the side of the ship. The side scan sonar uses sound waves to detect seafloor types (sand, mud, silt) and objects (coral, rocks, manmade debris, ship wrecks, etc.). With good images you can see sand waves and identify objects about size of a car tire. In order to produce a map of the survey area, we tow the side scan sonar in tightly spaced overlapping lines. We call this mowing the lawn because our survey pattern mimics how you’d typically mow your lawn. Sadly we didn’t find any sunken treasure, but several resident dolphins paid us a visit, which was reward enough.
We left Jobos Bay and conducted several bongo net tows looking for marine debris and marine life on our way to our next port of call in Ponce. We arrived in the Port of Ponce around 9 p.m. to transfer scientific personnel and stayed overnight.
The Midnight Watch
Feb. 17, 2009 – 12:30 am (Day 9)
It’s just after midnight and we’re 20 miles south of La Parguera conducting water column profiles, a series of scans that help create a cross-sectional view of the sea. Our crew, along with University of Puerto Rico (UPR) researchers, is sampling down to 3,280 feet (1,000 meters) every two hours and made one profile down to 8,200 feet (2,500 meters). The ship and scientific crew are working around the clock in 24 hour mode (four hours working and eight hours off).
This far out at sea, you are unable to see the lights of land, but the moon is brightly shining. However, by looking out from the opposite side of the ship, staring out into the abyss, you can’t help but be humbled by the stars and seemingly endless ocean night. You tend to get philosophical on the midnight watch. It seems like we left Ponce a week ago, but we only left at 6 a.m. yesterday and have been working out here since about 9 a.m.
Our water column profiler consists of an electronics package with many sensors that measure ocean parameters (salt content, temperature, density, depth, dissolved oxygen, and many more) as the instrument is lowered through the water column. Water sampling bottles are placed around the instrument package and allow us to collect water samples at up to 12 different depths. We’re providing ship time to UPR to allow them to collect information to better understand this area of complex ocean water layers.
There are many different layers of water in the deep ocean. Some start in the North or South Pole and slowly work their way deep below the warmer surface water of the Caribbean Sea. The surface temperature in this area starts at 81 degrees Fahrenheit, drops to 41 degrees at 3,280 feet and seems to level off at 39 degrees at 8,200 feet. Cooler water is heavier and sinks below the warmer, lighter water. In addition to using the data to protect the environment, scientists are also studying this layering of ocean water as a potential way to generate energy using the different physical properties of the water layers.
I’m off watch now and getting ready to get some sleep. We plan to tow the bongo nets later today on our return trip to Ponce. We will be transferring scientific personnel and mobilizing for our next adventure off La Parguera later today.
Editor's Note: The opinions expressed in Greenversations are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.