NOAA Teacher at Sea: Sue Zupko
NOAA Ship: Pisces
Mission: Extreme Corals 2011; explore the ocean bottom to map and study health of corals and their habitat
Geographical Area of Cruise: SE United States deep water from off Mayport, FL to St. Lucie, FL
Date: June 4, 2011
Weather Data from the Bridge
Position: 29.1° N 80.1°W
Time: 11:00 EDT
Wind Speed: calm
Visibility: 10 n.m.
Surface Water Temperature: 27.6°C
Air Temperature:27.6°C
Relative Humidity: 72%
Barometric Pressure:1018.4 mb
Water Depth: 85.81 m
Salinity: 36.55 PSU
When the strong current from the Gulf Stream stretched the tether of the ROV and broke one of the three fiber optic cables inside, it was time to come up with a new plan. What do you do in the middle of the ocean if the main gear is not functioning? Plan B. Well, Plan B was using the spare fiber optic in the tether. The spare one then broke as a result of being rubbed, most likely, by the sharp end of the original broken fiber during the next dive. Now we had to go to Plan C . Fortunately the ROV crew is experienced, and, like Boy Scouts, were prepared. They brought a spare ROV and tethers from their lab in La Jolla (pronounced La Hoya), CA just in case. The ship is running the sonar gear back and forth over the area we plan to dive tomorrow, mapping out the bottom, looking for coral mounds. This process is called “mowing the lawn” since you run the beams back and forth to get complete coverage of the bottom, and it looks like the lines on the lawn left by the mower. Think of the beam as having the shape of a flashlight’s beam shining on the floor. Another interesting feature is that the acoustic beam can also read what fish are present. It needs to have a swim bladder for the signal to bounce back. When it does, based on the sound, an experienced acoustician can read what fish the signal represents. Sharks don’t have a swim bladder like most fish do so their signals are a bit more difficult to read.
I was just up on the bridge and it seems we hit “pay dirt” (like gold miners). The captain had been explaining to me a symbol shown on the Electronic Chart Display System (ECS). It looks like a graphic math problem showing the intersection of lines, in this case one line running on a 110° angle with three lines parallel to each other intersecting it. The line in the middle is a bit longer than the other two. I asked how he knew what that symbol meant. Apparently, there is a book for everything on the bridge. He whipped out his handy-dandy book entitled, Chart No. 1. It is a key to reading nautical charts (maps). He searched for the correct page with bottom obstructions of all types and showed me that symbol and what it means. Whenever I have a question, the bridge crew whips out a book of some type to let me see the answer. It’s really interesting. The Pisces is a really modern ship with the latest electronic navigation and scientific features. The other day I asked about navigating without power. There is a book for that. Bowditch American Practical Navigator has everything you need to know about crossing the ocean without electronics. As it says on my classroom door, “Reading makes life a lot easier.” Turns out that symbol is a shipwreck.
But I digress. Back to the pay dirt (we struck gold). Laura Kracker, our geographer started getting excited. “Look at this! Look at this! Write down these coordinates.”
She went running back to the acoustics lab (where they use sound echos to map the ocean floor and the presence of fish) to mark the location along the transect (lines we’re running) because we apparently were over coral mounds. Using information gathered by others in years past as a guide, they were mowing the lawn with the sonar to find interesting habitat to study with the ROV. As the ship went back and forth along the planned transect to develop a much better map than existed, Laura would radio the bridge about any changes to the courseto pinpoint the best areas for us to study over the next couple of days.
Everyone was very excited. So, although the ROV had to be switched out, which took a lot of work, we made good use of the time on the ship. After a whole day of mapping, it’s now late at night and the map looks gorgeous. This is important work and many cruises are devoted entirely to mapping. Andy David, our lead scientist, says this acoustic mapping is useful to many people and will allow more precise coral surveys for years to come.