Chemical Sensor Group

Kenneth S. Johnson, Principal Investigator

The vastness of the ocean presents a daunting challenge for scientists: How can we interpret trends in ocean ecosystems when the measurements we make are few and far between? In the open sea, most scientists have historically relied on ships to transport them perhaps no more than once a year to locations where they spend only a short time capturing a snapshot of ocean conditions that prevail below the sea surface. In the coastal zone, where conditions may change hourly, most sampling is done no more frequently than once a month. Far offshore, processes that drive ecosystem structure and function often work on a seasonal time scale. Closer to the coast, similar processes operate much more rapidly. The problems this presents lead to a singular conclusion that all ocean scientists agree on: the ocean is grossly undersampled!

Current records of fundamental ocean properties such as oxygen, pH, nutrients, or chlorophyll describe a range of ocean states. However, the sample-to-sample variability observed in ocean time series may not necessarily reflect actual trends at any given location and time because so few measurements are collected for extended periods and in rapid succession. Furthermore, the limited sampling provides little scientific insight into the processes that actually underlie the snapshot observations.

Developing new tools and techniques to overcome these challenges is a major driver of Ken Johnson’s Chemical Sensor Group activities. Application of this approach in Elkhorn Slough, near MBARI in Central California, highlights some of the advances in understanding when sampling resolution is more closely matched to environmental processes. Opportunities for deploying analogous sensor suites in the vast expanse of the Southern Ocean provide another perspective on how we can address the fundamental problem of “being there”.

Apex profiling float

The ISUS nitrate sensor is integrated into the body of a Webb Research Apex profiling float that is of the type used in the Argo array.


Ben Davis

Research Technician

Former Lab Members

  • Thomas P Chapin (former postdoctoral fellow/now USGS)
  • Zanna Chase (former Postdoctoral Fellow/now at University of Tasmania)
  • Steve Fitzwater (former Research Technician/deceased)
  • Patrick Gibson (former Postdoctoral Fellow)
  • Todd Martz (former Postdoctoral Fellow/now at Scripps Institution of Oceanography)
  • Joe Needoba (former Postdoctoral Fellow/now at Oregon Health and Science University)


Upper-ocean systems
Acoustical ocean ecology
Acoustic instruments
Acoustic fingerprinting
Acoustic community ecology
Acoustics in the news
Biological oceanography
Global modes of sea surface temperature
Krill hotspots in the California Current
Nitrate supply estimates in upwelling systems
Chemical sensors
Chemical data
Land/Ocean Biogeochemical Observatory in Elkhorn Slough
Listing of floats
SOCCOM float visualization
Periodic table of elements in the ocean
Biogeochemical-Argo Report
Profiling float
Interdisciplinary field experiments
Ecogenomic Sensing
Genomic sensors
Field experiments
Harmful algal blooms (HABs)
Water quality
Environmental Sample Processor (ESP)
ESP Web Portal
In the news
Ocean observing system
Midwater research
Midwater ecology
Deep-sea squids and octopuses
Food web dynamics
Midwater time series
Respiration studies
Zooplankton biodiversity
Seafloor processes
Revealing the secrets of Sur Ridge
Exploring Sur Ridge’s coral gardens
Life at Sur Ridge
Mapping Sur Ridge
Biology and ecology
Effects of humans
Ocean acidification, warming, deoxygenation
Lost shipping container study
Effects of upwelling
Faunal patterns
Previous research
Technology development
High-CO2 / low-pH ocean
Benthic respirometer system
Climate change in extreme environments
Station M: A long-term observatory on the abyssal seafloor
Station M long-term time series
Monitoring instrumentation suite
Sargasso Sea research
Antarctic research
Geological changes
Arctic Shelf Edge
Continental Margins and Canyon Dynamics
Coordinated Canyon Experiment
CCE instruments
CCE repeat mapping data
Monterey Canyon: A Grand Canyon beneath the waves
Submarine volcanoes
Mid-ocean ridges
Magmatic processes
Volcanic processes
Explosive eruptions
Hydrothermal systems
Back arc spreading ridges
Near-ridge seamounts
Continental margin seamounts
Non-hot-spot linear chains
Eclectic seamounts topics
Margin processes
Hydrates and seeps
California borderland
Hot spot research
Hot-spot plumes
Magmatic processes
Volcanic processes
Explosive eruptions
Volcanic hazards
Hydrothermal systems
Flexural arch
Coral reefs
ReefGrow software
Eclectic topics
Submarine volcanism cruises
Volcanoes resources
Areas of study
Bioluminescence: Living light in the deep sea
Microscopic biology research
Open ocean biology research
Seafloor biology research
Automated chemical sensors
Methane in the seafloor
Volcanoes and seamounts
Hydrothermal vents
Methane in the seafloor
Submarine canyons
Earthquakes and landslides
Ocean acidification
Physical oceanography and climate change
Ocean circulation and algal blooms
Ocean cycles and climate change
Past research
Molecular ecology
Molecular systematics
SIMZ Project
Bone-eating worms
Gene flow and dispersal
Molecular-ecology expeditions
Ocean chemistry of greenhouse gases
Emerging science of a high CO2/low pH ocean