Autonomous platforms that support low-power sensors represent one approach to expanding ocean observing. This paper describes a unique autonomous platform designed to deliver long-term sensor measurements from the benthic boundary layer at low cost. The platform, called a Benthic Observer (BeOb), is powered by energy harvested with a benthic microbial fuel cell (BMFC), and it uses an acoustic modem to both store and transmit data organized in daily reports of hourly measurements. A BeOb equipped with sensors to measure dissolved oxygen, temperature, and conductivity ~1 m above the seabed has been active for over 14 months on the Oregon slope at a location within the core of the oxygen minimum zone. During this observation period, the system’s battery reserves have been kept fully charged by the BMFC. A 90-day time series of sensor data are compared to simultaneous high-frequency measurements at a neighboring Ocean Observatories Initiative cabled Benthic Experiment Package to examine the expected quality and confidence levels for seasonal or annual means of continued measurements. An ocean observing system incorporating arrays of BMFC-powered platforms transmitting to central gateway modems is proposed for future ocean-property monitoring programs. Such arrays may be especially helpful for tracking expansions of ocean oxygen minimum zones.
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