Waiting For the Light: A Few Decades and Now Endless Possibilities with Collin Roesler

The color of the ocean varies from violet blue in the clearest subtropical oceans to emerald green in productive higher latitude waters to turbid red in coastal seas with harmful algal blooms. Most of the color variations are due to different concentrations of phytoplankton, the ocean’s single-celled photosynthesizers. In the late 1970s, NASA and a science team launched a sensor on a satellite that made use of the relationship between greenness and the concentration of the phytoplankton pigment chlorophyll. The sensor had just four channels, or colors, with which to detect the intensity of sunlight reflected out of the ocean. There were so many reasons why this mission should not have worked, but it did, opening up tremendous opportunities to study the base of the oceanic food web on the scale of ocean basins at nearly weekly time scales over a decade.
As a college student, Professor Collin Roesler discovered ocean color remote sensing, and a few years later, optical oceanography. As each new satellite mission was launched, there were incremental gains in remote sensing, but with lingering limitations. Meanwhile, technological developments were being achieved in sensors deployed from ships and on moorings, revealing the potential for what could be detected from space. Roesler’s earliest publications focused on detecting phytoplankton taxonomy and size distribution from measurements of the full spectrum of sunlight from space. Finally, nearly forty-five years after that first ocean color satellite launch, we have this capability in space. We now have endless opportunities to observe changing ocean community structure, carbon cycling, and the expansion and contraction of marine ecosystems as our climate changes.
Professor Roesler’s research examines the response of ocean ecosystems to environmental forcing. She uses optical sensors deployed on ships, moorings, and satellites to detect ecological and physiological characteristics of phytoplankton, the ocean’s single-celled photosynthetic organisms. Her work focuses on the changing composition and services of phytoplankton communities across time scales of hours to decades, spatial scales of estuaries to ocean basins, and from tropical to the polar latitudes. Her observational work in the ocean is the basis for algorithms for detecting ocean ecosystems from current and future satellite-based sensors.
William R. Kenan Jr., for whom the William R. Kenan Jr. Professor of Earth and Oceanographic Science is named, was an accomplished chemist, engineer, and agricultural scientist who devoted much of his life to philanthropy. Bowdoin, along with several other educational institutions and a multitude of community organizations, was a beneficiary of Kenan’s extraordinary generosity. The Kenan Professorships were established at Bowdoin College in 1975 with a grant from the William R. Kenan Jr. Charitable Trust.