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Phenology indices and their importance for coral reef biology

By Marie-Fanny Racault and Dionysios E. Raitsos

Plymouth Marine Laboratory, U.K.

1st Prize in the LearnEO! Lesson Writing Competition 2013/14

Being the base of the marine food-web, phytoplankton provides a source of food for the larvae of many coral reef species, including fish, crustaceans and mollusks. The bloom timing (phenology), along with the intensity of phytoplankton availability is determinant for the larvae survival.

This lesson introduces phenology metrics relevant to monitor the seasonality of phytoplankton using remote sensing ocean colour data from the European Space Agency (ESA) Climate Change Initiative project (OC-CCI). It investigates the phytoplankton dynamics in major coral reefs of the Red Sea, which is one of the most saline and warm seas in the world.

Suitable for university students or continued professional development training (intermediate level).

The research that forms the basis of this lesson is published in: Racault, M.-F., et al. (2015): Phytoplankton phenology indices in coral reef ecosystems: Application to ocean-color observations in the Red Sea, Remote Sensing of Environment.

IMPORTANT NOTE: This lesson requires Bilko 3.4 from February 2013 or later, as earlier versions of the software can not open and display all data as described in the lesson.

figure from the lesson


Coral reefs are among the most biologically diverse ecosystems on Earth. They occupy less than 0.1% of the world's ocean surface, and yet they host 25% of all the marine species. Coral reefs deliver valuable and vital ecosystem services. They offer a source of food, coastal protection, and employment through fisheries, recreation, and tourism for millions of people around the world. However, coral reefs are fragile ecosystems, facing serious threats from climate change, marine acidification, destructive and unsustainable fishing practices, and water-polluting land-use activities.

The Red Sea hosts some of the most pristine coral reefs that have adapted to live in one of the most saline and warm seas in the world. In addition to being a very warm environment, the Red Sea is experiencing a particularly fast increase in temperature, which began abruptly in the mid-90s and persists until present. These unique conditions make the Red Sea an excellent laboratory for studying the effects of environmental warming on marine organisms.

Microscopic marine algae, so-called phytoplankton, provide an important source of food for coral reef ecosystems. They are grazed on by the larvae of many species, including fish, crustaceans and mollusks. The magnitude and timing of phytoplankton availability are known to play a fundamental role in the survival of larvae.

Over the past two decades, remote sensing measurements of ocean-colour have provided unique information on surface marine phytoplankton, allowing us to monitor their distribution at high temporal (1 day) and spatial (1 km) resolution. The colour of the ocean is a good indicator of the primary photosynthetic pigment found in phytoplankton, chlorophyll-a. The concentration of chlorophyll-a can vary from season to season and the study of these seasonal variations is defined as phytoplankton phenology.

Lesson Overview

This lesson uses ocean colour images from the ESA Climate Change Initiative project (OC-CCI) to quantify phytoplankton seasonality and provide metrics relevant to help understanding the functioning of coral reef ecosystem.

Learning objectives

At the end of the lesson you should be able to:

Lesson content

The lesson is divided into the following sections:

  1. ESA CCI ocean-colour images
  2. Phytoplankton in coral reef regions
  3. Phenology indices and their importance for coral reef biology

Data and tools for this lesson

Data sets supplied

Ocean-colour (chlorophyll-a content)
Phenology of phytoplankton
Bathymetry (Water depth)
Coral reefs distribution

Bilko tools

Bilko formula documents:
Colour palettes

Downloading the lesson

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