1.5 Effects of Light and Dark on
Phytoplankton Populations

Special thanks to Drs. Robin Ross and Langdon Quetin for input to this Activity.

Teacher Background

Each southern summer, increased light levels and nutrient-rich upwellings support blooms of phytoplankton-floating microscopic marine algae-which support vast numbers of krill, which in turn form the main food source for organisms further up the food chain: whales, seals, fish, squid and birds, including penguins.

Results from the first four field seasons of the LTER at Palmer station support the hypothesis that year to year changes in physical factors such as sea-ice extent and timing (when in the season the ice appears and disappears) impact all levels of the ecosystem. Phytoplankton abundances also vary greatly from year to year, and from place to place, depending on the specifics of the ice-sheet. The two seasons following winters with high ice coverage developed overall phytoplankton biomass during bloom periods five times greater than two other seasons!

Researcher Maria Vernet travels around Arthur Harbor in a Zodiac and takes water samples, as well as being part of the Duke team. (Have students go on-line to read her Biography and Journal describing her work days and the research.) She then exposes the phytoplankton she scoops up to various light conditions. In this Activity, students will simulate some Palmer LTER techniques and analyze the consequences.

Sidebar: Bill Fraser, Ornithologist


Students will investigate the effect of variations in length of day on phytoplankton growth.


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