Monterey Bay Aquarium Research Institute
CANON Initiative
Case study:
thin layers

Presented by Percy L. Donaghay and John Ryan

Thin layers are patches of plankton that range in thickness from 10 centimeters to 3 meters, yet are sufficiently intense, persistent and spatially continuous to affect critical processes and/or the performance of optical, acoustical, and chemical sensors. Thin layers can occur in coastal and open ocean environments, extend for tens of meters to more than 10 kilometers, and be intense enough to impact remote sensors.

scientific graph showing an intense 12 cm thick phytoplankton layer
Extremely intense 12 cm thick phytoplankton layer observed for 18 hours simultaneously at two sites 300 meters apart in East Sound, Washington. Image by Percy L. Donaghy.

Thin layer sampling challenges

Thin layers must be sampled at fine enough vertical scales to solve rate-controlling processes. The sampling must occur over concentration ranges that control physical, chemical, and biological responses. The sampling must occur over a long enough time in order to detect patch formation. The samples will then be used to identify biota, chemistry, and rate processes measurements.

Thin layer sampling methods

A key question is how to build and deploy systems that can meet these challenges of sampling in a variety of coastal waters.

Ship-based high resolution profiling can quantify the intensity, thickness, spatial extent, and persistence of thin layers in topographically constrained systems.

Ocean response coastal analysis system (ORCAS) concept

Researchers developed a system of autonomous bottom-up profilers that can be rapidly deployed in arrays to allow coherent assessment of changes in thin layers.

Graph of an orcas profiler array
Ocean Response Coastal Analysis System Profiler Array Graph. Image by Percy L. Donaghy

Current research challenge

  • How to use in situ techniques for biota characterization to identify plankton and the importance of growth and mortality in controlling the observed patterns.


  • Thin layers represent a critical scale for understanding the structure and dynamics of marine systems and the performance of remote and in situ sensors.
  • Arrays of autonomous moored bio-optical profilers have evolved to the point where they can be powerful tools for detecting and characterizing thin layers and increasing an understanding of the mechanisms controlling thin layer characteristics, dynamics, and impacts.
  • Airborne lidar is a potentially powerful tool for mapping the spatial extent and spatial characteristics of thin layers once the source of the backscattering signal is validated.
  • Development of advanced adaptive sampling techniques are critical for identifying biota, chemical sensing and measuring rate processes.
  • Deployment of submersible scanning flow cytometers on autonomous profilers could be used in the future to detect the presence of non-spheroid phytoplankton and quantify mortality events in situ.

Last updated: Jul. 19, 2012