Classroom Resources Diatoms_through_the_microscope

Published on November 7th, 2013 | by Jo


Piles of Plankton

Phytoplankton, also known as micro algae, are single celled marine plants, generally microscopic in size.  They are similar to land plants in that they contain chlorophyll and require sunlight in order to live and grow.

Most phytoplankton are buoyant and float in the upper part of the ocean, where sunlight penetrates the water. Oceanic phytoplankton is the primary food source, directly or indirectly, of nearly all sea organisms.

It is believed that the amount of phytoplankton in many of our oceans has dropped by up to 40% in the last 100 years.
The NASA map below shows the distribution phytoplankton for the waters in Port Phillip bay and south to Tasmania and the surrounding ocean. It was obtained in study which took place in 1981.

tasmania_27nov81_piles of plankton

                Photo courtesy of

The colour scale goes from dark blue to a dark red. This spectrum indicates a gradation from low concentration to high concentration of phytoplankton.

a. A billion (1000 million) of litres of sea water is processed to extract all of the phytoplankton. This water  contains 10 milligrams of phytoplankton per cubic metre (a measurement near the top of the scale).What is the weight in kilograms of the phytoplankton obtained?

b. How much sea water with a concentration 9.5 milligrams per cubic metre of phytoplankton needs to be processed to obtain 10 tonnes of phytoplankton?

Question created by Chaitanya Rao, Daniel Mathews, Norman Do and Michael Evans

Feature image courtesy of U.S. National Oceanic and Atmospheric Administration[subscribe2]

Comments are closed.

Back to Top ↑