The National Marine Sanctuary System manages marine areas in nearshore and open ocean waters that range in size from less than one to almost 140,000 square miles. As a result, each area has its own concerns and requirements for environmental monitoring, therefore, monitoring programs are typically tailored to the information needs of each individual site. However, ecosystem structure and function in all these areas have similarities and are influenced by common factors that interact in comparable ways. Furthermore, the human influences that affect the structure and function of these sites are similar. For these reasons, in 2001 the program began to implement System-Wide Monitoring (SWiM) which facilitates the development of effective, ecosystem-based monitoring programs that address management information needs using a design process that can be applied in a consistent way at multiple spatial scales and to multiple resource types. It identifies three primary components common among all marine ecosystems: water, habitats, and living resources.
As part of SWiM, Condition Reports have been developed for each of the marine sanctuaries as a way to summarize the condition and trends of sanctuary resources. Monitoring data is summarized throughout these reports as a way to describe the status and trends of water quality, habitat, living resources, and maritime archaeological resources.