Behind every marine animal is a food chain that draws energy from the same source - phytoplankton and zooplankton. These are the ocean's simplest organisms, and they rely entirely on the nutrients, sunlight and physical conditions of the ocean for their survival. "This is probably the one place in the food web where the physics and the biology come closest together," said Dr. Ted Cooney, professor emeritus at University of Alaska Fairbanks.
The sub-arctic marine community of PWS is dominated by large phytoplankton called diatoms in the winter and early spring, and is taken over by a community of zooplankton called copepods in the summer. This seasonal change is thought to be created mainly by changes in light and heat throughout the year. In the winter when heat and light are low, diatoms and other phytoplankton spend their time in the nutrient-rich waters that float up from the bottom, sustained by the phosphates, nitrates and silicon that fell there the summer before. In the summer, a warm layer of water keeps the cooler nutrient-rich waters from rising to the top. Phytoplankton start to convert the energy from the sun, and this jump in productivity encourages copepods and other zooplankton to feed on the phytoplankton and grow in numbers.
These seasonal changes in microorganisms have been studied in PWS for over 30 years. However, even at this stage in the food chain scientists admit to having major holes in understanding the way life interacts with its surroundings. "We don't know how primary productivity is reacting to changes in the ocean, but we're pretty sure it does," Cooney said. The seasonal collections that have been done for so many years have taught scientists a lot, but still leave something to be desired. According to Cooney, science lacks information that would lead to an understanding of how these communities of microorganisms change on a daily, yearly or even decadal basis.
The PWSOS will deploy a series of fluorometers on oceanographic moorings. This real-time data collection should give scientists a clearer picture of the movements of phytoplankton. Acoustic surveys will be used to track the movement of zooplankton as they travel up and down in the water column or through the Sound. These data combined will help scientists infer how much biomass is transferred between the Gulf of Alaska and the Sound through Hinchinbook Entrance and Montague Strait, and how that transfer changes as the years and decades pass. Scientists will be able to detect regime shifts, patterns in dominance, or geographic moves that may follow cycles. Once scientists know how the ocean affects movement and changes in populations of microorganisms, they can determine how the microorganisms cause changes in large animal populations in the food chain.
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