Coordinated Ocean Monitoring and Research Act This bill revises and reauthorizes through FY2021 the Integrated Coastal and Ocean Observation System Act of 2009. The Integrated Ocean Observing System (IOOS) is a network of federal and regional entities that provide information about the nation's coasts and oceans, as well as the Great Lakes. The National Oceanic and Atmospheric Administration (NOAA) must: (1) serve as the lead federal agency for the implementation of the IOOS, and (2) establish an IOOS Program Office to oversee daily operations and coordination of the IOOS. The bill outlines the requirements for NOAA as the lead agency. The bill establishes a process for regional associations to certify their regional coastal observing systems. The Joint Subcommittee on Ocean Science and Technology of the National Science and Technology Council must: (1) conduct an Ocean Chemistry Coastal Community Vulnerability Assessment on ocean acidification within a year and every five years thereafter; and (2) develop a plan to deploy ocean acidification sensors prioritized by the threat to coastal economies and ecosystems, gaps in data on ocean acidification, and research needs. The National Science Foundation's research on ocean acidification must include research on: (1) impacts of multiple stressors on ecosystems exhibiting hypoxia (a dead zone that is depleted of oxygen), harmful algal blooms (rapid accumulation of algae), or sediment delivery; and (2) the effects of those impacts combined with changes in ocean chemistry.