21 years of algae blooms observed from space

Edson Silva just published his first article as part of his institutional PhD project - congratulations! Together with five other co-authors from NERSC and one from the University of Bergen (UiB), he studied the annual cycle of phytoplankton/algae blooms in the Nordic Seas by utilizing satellite data from 2000-2020.

Turquoise-coloured plankton bloom off the coast of northern Norway and Russia. Image from August 2011, during the late summer/autumn bloom in the Barents Sea. Credit: ESA, CC BY-SA 3.0 IGO (https://creativecommons.org/licenses/by-sa/3.0/igo/)

What is phytoplankton?

Phytoplankton are tiny algae living in water everywhere on Earth. They use sunlight, carbon dioxide, and nutrients present in the water to live and reproduce – they do photosynthesis, just like plants on land. Whenever these three factors line up favourably, phytoplankton numbers can explode, leading to so-called algae blooms. This happens on a regular basis throughout much of growth seasons of the year. In lakes and oceans all over the globe, we can see these blooms both on small and on large scales, because extremely high amounts of phytoplankton can visibly change the water colour. In the image on the side, you can see a phytoplankton bloom in the Barents Sea, observed in 2011 by the Envisat satellite from the European Space Agency. These blooms regularly occur in our adjacent seas: the North Sea, the Norwegian Sea, and the Barents Sea all experience various algae blooms every spring to late summer/autumn.

Why is phytoplankton important?

It might look pretty and impressive on satellite images when phytoplankton is blooming in the ocean, but aside from the aesthetic aspect, phytoplankton plays a vital role – it is the base of the marine food web! Life in the ocean depends on it. But: Not every type of phytoplankton is good either. Some can produce toxic material that harms for example fish and shellfish; even other animals in and around the water can be affected, and that includes us humans. Another factor that makes phytoplankton relevant for us might have occurred to you already: They use carbon dioxide during photosynthesis. And by doing so, they remove carbon from the atmosphere, contributing to the global carbon cycle.

Observing phytoplankton from space

Since large phytoplankton blooms can even be seen from space, using satellite data to investigate them is natural. The recent study Twenty-One Years of Phytoplankton Bloom Phenology in the Barents, Norwegian, and North Seas by Edson Silva and his NERSC/UiB co-authors François Counillon, Julien Brajard, Noel Keenlyside, Anton Korosov, Lasse Pettersson, and Annette Samuelsen focused on the seas near Norway. The aim was to describe when and where phytoplankton blooms in these areas have appeared, if changes over the observational period occurred, and how several factors affected the blooms’ initiation and evolution.

The authors made use of “ocean colour” remote sensing data from the European Space Agency covering the past 21 years. They also used ocean modelling data and other remote sensing data to investigate factors that might contribute to phytoplankton blooms in spring and late summer/autumn, such as mixed layer depth, sea surface temperature, wind speed, and suspended particulate matter.

Using a large array of data, Silva and his co-authors managed to identify trends and interannual variability of when the blooms start, when they reach highest concentration, how long they last, and how intense they are. Some key findings of this study are:

  • The initiation of summer/autumn blooms are delayed.
  • The summer/autumn blooms have intensified and last longer.
  • The authors identified key potential drivers causing the interannual variability in several regions, paving the way for potentially predicting spring blooms there!

To find out more, you can read the article.

Edson Silva’s PhD project

Silva started his 3 years institutional INSTSTIP PhD project at NERSC in the Climate Dynamics and Prediction group and the University of Bergen in November of 2020. He is being supervised by François Counillon (CDP), Julien Brajard (DA), and Noel Keenlyside (UiB/NERSC).

He is focusing on assessing the mechanisms triggering algae blooms and how to use them in climate prediction. Currently, he is directing his research to harmful algae blooms, which produce toxins that can threaten human health and negatively impact the fishery and aquaculture industry.



Silva, E, Counillon, F, Brajard, J, Korosov, A, Pettersson, L, Samuelsen, A, & N Keenlyside. Twenty-One Years of Phytoplankton Bloom Phenology in the Barents, Norwegian, and North Seas. Frontiers in Marine Science 2021. 8:746327. https://doi.org/10.3389/fmars.2021.746327

This was first published at Nansen Environmental and Remote Sensing Center:

21 years of algae blooms observed from space | Nansen Environmental and Remote Sensing Center (nersc.no)