Featured Scientist: Meet Dan!

Our annual surveys would not be possible without our wonderful collaborators from around the world. We'll dedicate several future blog posts to highlight these individuals, so that you can learn more about them, their research, and the valuable contributions they make to the survey. You can find previous posts here. Today we feature Dr. Dan Otis from the University of South Florida!

My name is Dr. Dan Otis, and I work at the University of South Florida’s College of Marine Science in the Institute for Marine Remote Sensing (IMaRS). The primary focus of my work is using satellite measurements to study the color of the ocean. The color of the ocean as viewed from space can provide information about what is in the water. Three main things that I look for that change the color of the ocean are chlorophyll-a, colored dissolved organic matter (CDOM) and suspended sediments. Chlorophyll-a is a pigment that plants use to harvest light energy and carry out photosynthesis. In the ocean, this is done by algae called phytoplankton. Examining trends and patterns in the amount of chlorophyll-a in the ocean tells us where phytoplankton are most abundant and can allow us to track features in the surface waters of the ocean.

This is my third year on the USVI leg of this cruise and while I’m out here, I filter lots of water to measure phytoplankton and CDOM, and also use an instrument called a radiometer that measures the color of the ocean surface. I then compare what I see at the surface to what the satellite sees from space. This year, I have also been providing imagery from a several ocean color satellites to scientists on board, so we can see how phytoplankton is distributed in the waters of the USVI and how water movement may be affecting larval fish. Ocean color satellites generally collect one “scene” or picture of the ocean surface in a location every 1-2 days.  However, there are often clouds that get in the way, so we make composites of several daily scenes to remove clouds. The  image below is a composite of several images collected by the Visible Infrared Imaging Radiometer Suite (VIIRS) sensor during the cruise. This is called a “false-color” image where different colors represent different concentrations of chlorophyll-a, which can be interpreted using the color bar to the right of the image. The units in this case are mg/m3.

Composite image of chlorophyll-a during cruise