A submersible imaging‐in‐flow instrument to analyze nano‐and microplankton: Imaging FlowCytobot

TLDR

Detailed, sustained observations of plankton interactions between physical and biological factors are essential for understanding species composition. The authors developed a submersible flow cytometer with imaging capability and a 5 mL/20 min sampling rate to characterize nano‑ and microplankton. The Imaging FlowCytobot images individual cells, samples 5 mL every 20 min, operates unattended for months, and transmits data to shore. Imaging FlowCytobot was successfully tested for two months, is now deployed alongside FlowCytobot, and together they enable continuous long‑term monitoring of plankton community structure across a wide size range.

Abstract

A fundamental understanding of the interaction between physical and biological factors that regulate plankton species composition requires, first of all, detailed and sustained observations. Only now is it becoming possible to acquire these types of observations, as we develop and deploy instruments that can continuously monitor individual organisms in the ocean. Our research group can measure and count the smallest phytoplankton cells using a submersible flow cytometer (FlowCytobot), in which optical properties of individual suspended cells are recorded as they pass through a focused laser beam. However, FlowCytobot cannot efficiently sample or identify the much larger cells (10 to >100 µm) that often dominate the plankton in coastal waters. Because these larger cells often have recognizable morphologies, we have developed a second submersible flow cytometer, with imaging capability and increased water sampling rate (typically, 5 mL seawater analyzed every 20 min), to characterize these nano‐ and microplankton. Like the original, Imaging FlowCytobot can operate unattended for months at a time; it obtains power from and communicates with a shore laboratory, so we can monitor results and modify sampling procedures when needed. Imaging FlowCytobot was successfully tested for 2 months in Woods Hole Harbor and is presently deployed alongside FlowCytobot at the Martha's Vineyard Coastal Observatory. These combined approaches will allow continuous long‐term observations of plankton community structure over a wide range of cell sizes and types, and help to elucidate the processes and interactions that control the life cycles of individual species.