Discrimination of phytoplankton functional groups using an ocean reflectance inversion model

Area of Science:

• Marine optics
• Phytoplankton ecology
• Remote sensing

Background:

• Ocean reflectance inversion models (ORMs) link satellite-observed water color to marine inherent optical properties (IOPs) for studying phytoplankton.
• Existing ORMs often struggle to differentiate individual phytoplankton groups within a community, especially under diverse environmental conditions.

Purpose of the Study:

• To assess the capability of an ORM to distinguish between Noctiluca miliaris and diatoms in the northern Arabian Sea.
• To identify conditions where the ORM performs effectively or poorly in discriminating between these phytoplankton groups.

Main Methods:

• Synthesized IOP profiles representative of Arabian Sea bio-optical conditions.
• Generated remote-sensing reflectances using Hydrolight based on synthesized IOPs.
• Applied an ORM to estimated relative concentrations of diatoms and N. miliaris.

Main Results:

• ORM retrieval accuracy degraded when partitioning the total phytoplankton signal into subcomponents, even under ideal conditions.
• Despite biases in absolute magnitudes, the ORM successfully detected the presence or absence of N. miliaris in simulated water columns.
• Performance varied, with specific conditions identified for optimal and suboptimal ORM performance.

Conclusions:

• Caution is advised when interpreting the absolute magnitudes of ORM retrievals for specific phytoplankton groups.
• Qualitatively, ORMs offer a robust method for determining the presence or absence of species like N. miliaris.
• Further refinement of ORMs is needed for precise quantitative analysis of mixed phytoplankton communities.