Marine ecosystems are changing rapidly in response to natural processes, human activities, and climate change. These drivers of change have become subject of increasingly intense focus from both research and management perspectives. There are some important scientific questions that need to be addressed with regard natural vs human-induced change including 1) the qualitative character of the ecosystem responses (“what changes?”), 2) their amplitudes (“by how much?”), and 3) their timing and spatial and temporal scales (“when and where are rates of change most profound?”). Phytoplankton are excellent indicators of marine ecosystem change. They are ecologically and biogeochemically important and relevant indicators, since they conduct a large share of system-scale primary production and hence carbon cycling, and they are highly sensitive to a suite of environmental stressors. There is much accumulated evidence that diverse ocean regions undergo strong and sometimes abrupt changes in phytoplankton composition, and productivity at roughly decadal intervals (i.e. regime shifts). This variability is associated with corresponding changes in atmospheric, hydrologic, chemical, and higher trophic-level biological processes and state variables.

SCOR Working Group 137 will focus on coastal ecosystems (estuaries, fjords, bays, sounds, open waters of the continental shelf, etc.) where perturbations from terrestrial, atmospheric, oceanic sources and human activities converge to cause changes that ramify across local and global scales. Human pressure on coastal regions and continental margins is increasing with expanding urbanization and the conflicting demands of tourism, agriculture and aquaculture, water diversions, wind parks and other developments.