Ciguatera Environmental Monitoring Methodology

Objectives of this tutorial

This tutorial provides a set of tools and advices useful for the implementation of a environmental surveillance of microalgae associated with ciguatera poisoning.

Assembly, deployment and collection of window-screen devices (or artificial substrates)

Window screens (WSs) are cheap, simple-in-design and easy-to-use passive sampling devices for benthic dinoflagellate cells.
These videos detail how to assemble, deploy and collect WS devices in the field :

Macroalgal samplings (natural substrates of dinoflagellates associated with ciguatera)

This video details how to sample macroalgae 

Processing and preserving window-screen and macroalgal samples  

The videos below detail the methods of processing and fixing window screens and macro-algae samples, depending on the nature of the analyzes for which they are intended. 

Identification and enumeration of dinoflagellate cells using light microscopy  

MATERIAL CHECK LIST

  • 1 inverted microscope equipped with x10, x20, x40, x100 objectives and a digital camera
  • 1“Sedgewick Rafter Cell” type counting chamber (if not available, use glass slides and cover glass)
  • Micropipette (P1000) and adapted tips
  • 1 manual counter

SAMPLE OBSERVATION PROCEDURE

  1. Invert the tube containing the sample several times to properly resuspend the cells.
  2. Place the equivalent of 1 ml of sample in the counting chamber using the micropipette.
  3. Observe the sample under the microscope.
  4. Count the cells by scrolling the counting chamber from right to left and from top to bottom in order to scan the entire field.
  5. Identify the different species present using the course on the identification of benthic microalgae associated with ciguatera (see below).
  6. Perform at least 3 counts/sample to determine an average cell density.

 NB: if you do not have a Rafter cell, the observation of the samples can be carried out between slides and coverslips, on aliquots of 100 µl of sample.

Introduction course to benthic harmful algal bloom (bHAB) species

Module 1

Brief overview of HABs, adverse effects and causative species. General introduction to dinoflagellate taxonomy and taxonomic principles


Module 2

General introduction to bHAB species with focus on species occurring in the South Pacific: Gambierdiscus


Module 3

Introduction to Ostreopsis and Coolia genera


Module 4

Introduction to Prorocentrum and unarmored dinoflagellates (Amphidinium)


Assessing dinoflagellate cell abundance in samples

Estimate cell number in macroalgal samples

Download excel spreadsheet with corresponding formulas

Estimate cell number in window-screen samples

Download excel spreadsheet with corresponding formulas

Learn more about Benthic dinoflagellate sampling methods

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