Continuously observing marine plankton in the coastal Mid-Atlantic

A diagram of the Rutgers University Marine Field Station and the LEO-15 Observatory near Tuckerton, New Jersey

The Rutgers LEO-15 Observatory off Tuckerton, NJ, is one of the first coastal observing systems in the world. Ocean observatories or "observing-systems" are facilities with numerous instruments for making automated measurements of oceanographic properties. NOAA's Undersea Research Program's Mid-Atlantic Bight Center (MAB) at Rutgers University, one of six regional NURP Centers, established a Long-Term Ecosystem Observatory site (LEO-15) on the continental shelf in the mid-1990s with the engineering support of Woods Hole Oceanographic Institution (WHOI). LEO-15 is located on a sandy bottom in about 50 feet (15 meters) of water offshore from the Rutgers University Marine Field Station near Tuckerton, New Jersey. LEO-15 is a very dynamic area with periodic upward movement of deep water (or "upwelling") to the surface driven by southwesterly winds. Such "upwelling" is a common feature of the Mid-Atlantic coast and is partly responsible the high abundance of plankton.

A photo of a LEO-15 Node out of the water on the dock showing "guest ports" and other connections.

LEO-15 has become a major center for coastal research and has also provided important public and educational outreach to an increasingly large community (http://www.thecoolroom.org/). LEO-15 utilizes two "nodes" anchored to the bottom that are connected to the shore-based control center by cables providing power and communication. These nodes have "guest ports" for plugging in additional instruments. The observation network provides information on the temperature, salinity, and other properties of the seawater on command. During special experiments, sampling at LEO-15 uses real-time data from these nodes and an array of satellites, meteorological sensors, underwater vehicles, and other instruments.

One of the most exciting instruments to use the LEO-15 guest ports is the FlowCytobot, an instrument for observing the smallest components of the "phytoplankton" or plant plankton that are the "grass" of the sea and the basis of the marine food chain. This instrument was developed by plankton biologists Robert Olson and Heidi Sosik at the Woods Hole Oceanographic Institution. Using a laser, this instrument measures light scattering and fluorescence of microscopic plankton cells that are less than 1/10,000 of an inch in diameter.

A photo of the FlowCytobot and a diagram showing how it is anchored to the bottom and connected to the LEO-15 node. Seawater is sampled through the sample inlet at about 16 feet (5 meters) depth. An example of measurements from the FlowCytobot at LEO-15 during a 3-day period in late October 2000. Samples from a depth of 16 feet (5 meters) were analyzed by the instrument every 5 minutes. The red and green lines show the results for two different types of phytoplankton. Panels B and C show phytoplankton properties that vary regularly from day to night.

The FlowCytobot is connected to the LEO-15 observatory through a guest port, which supplies power and allows the instrument to communicate with the laboratory on shore. The instrument is anchored to the bottom by divers and samples seawater through a hose that is suspended at a depth of about 16 feet (5 meters).

The FlowCytobot can be controlled using the internet, and the results can be observed the same way. It can make continuous measurements for weeks at a time without operator attention. It is very sensitive and can detect even the smallest phytoplankton in coastal waters.

In the future, instruments like this may help us to find "red tides" or determine the effects of coastal runoff or pollution on the plankton. The information will be useful to coastal ocean managers as well as scientists. This instrument offers a new perspective on marine ecosystem monitoring, with the potential for high-resolution, continuous measurements over long time periods.