Recent initiatives have established cabled ocean observatories from the subtidal zone down to abyssal depths, including sites in the North Pacific (Ocean Networks Canada, U.S. Ocean Observatories Initiative, DONET-Japan, MACHO-Taiwan), the Arctic (Ocean Networks Canada), the Atlantic (EMSO-Açores), the northwestern Mediterranean (EMSO-OBSEA) and in coral reef habitats (OCTOPUS-Okinawa; QIMOS-Australia). Cabled observatories enable real-time, continuous monitoring of seawater properties and ocean currents, and biological features that can be detected using video and still cameras and hydrophones. These integrated sensor systems provide opportunities for long-term observations of biodiversity change, in relation to environmental variables. The planned, multi-decadal lifetimes of cabled observatories should allow seasonal and inter-annual variability to be ‘filtered’ from longer term trends that could be related to ocean change. International organizations such as the Group on Earth Observations’ Biodiversity Observation Network (GEO-BON) and the European Multidisciplinary Seafloor and water-column Observations (EMSO) network are developing monitoring programs and suites of ‘Essential Biodiversity Variables’ that are intended to establish a standardized, global framework for detecting biodiversity change, based on scientific principles. This presentation will consider how some of these essential variables can be monitored continuously, using current cabled observatory technologies, with the aim of encouraging the development of a coordinated international program. We will use examples from the VENUS, NEPTUNE and Arctic observatories operated by Ocean Networks Canada, the EMSO OBSEA and Açores test sites, and the OCTOPUS coral reef observatory, to illustrate how underwater cameras and sensors can be used to quantify seasonal shifts in community composition, responses to rapid changes in oceanographic conditions, and ecosystem service activities such as seafloor bioturbation. Ultimately, observatory technologies could become valuable tools for managing human impacts on marine ecosystems, through the provision of baseline information and the detection of acute and long-term ecosystem responses to disturbance.