1.5 Effects of Light and Dark on
Special thanks to Drs. Robin Ross and Langdon Quetin for input to
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
Last Update: 1/18/97
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