This report provides guidance to the Gulf Ecosystem Monitoring (GEM) program to help ensure that it is based on a a science plan that is robust, far-reaching, and scientifically sound. The report commends the Trustee Council for its foresight in setting aside funds to create a trust fund to provide long-term research support; it notes that the GEM program offers an unparalleled opportunity to increase understanding of how large marine ecosystems function and change over time. The report outlines elements of a sound long-term science plan, including conceptual foundation, scope and geographic focus, organizational structure, community involvement, data and information management, and synthesis, modeling, and evaluation.