The Oceans

Basics

Worksheet 3

1. Phytoplankton

Dimethyl sulphide is a climatically important gas which is produced by phytoplankton. 

What are phytoplankton?

2. Positive climate feedback loop

Describe a positive climate feedback loop involving methane and eutrophication.

3. Oceanic source of nitrous oxide  and climate

How is the oceanic source of nitrous oxide likely to be affected by climate change and how, in turn, does nitrous oxide affect stratospheric ozone levels?

4. Ocean color

Because phytoplankton contain chlorophyll, phytoplankton are the most important in determining the colour of the ocean. High concentrations of phytoplankton gives more chlorophyll which in turn makes the ocean look green.

Color code scale for chlorophyll concentration (mg/m³)

Below you see two satellite images of the world oceans from space. The images are made from satellite instruments sensitive to concentrations of chlorophyll. The different colors in the ocean represent the concentrations of phytoplankton. In this way you can look at plant life in the oceans. 

Use the scale above to determine the chlorophyll concentration in various areas of the Earth in the images below.

Ocean color during summer (June-August 1998) in the Northern Hemisphere. Photo: NASA

North Atlantic phytoplankton bloom. Photo: NASA

Authors: Ellen K. Henriksen and Camilla Schreiner - University of Oslo - Norway. Scientific reviewer: Lucinda Spokes - Environmental Sciences, University of East Anglia, Norwich - U.K. Last update: 2004-03-27.