Dr. Lin Wu Delivers Faculty Lecture
November 14, 2008
The microscopic creatures in the aquatic ecosystem are often not given enough credit when it comes to the big roles they play in the environment.
Dr. Lin Wu, professor of biology and chair of the Department of Biology at Mount Union College, described some of these little organism’s key roles at the Faculty Lecture held Thursday evening at the College.
Wu opened her lecture by explaining that water seems to follow her wherever she goes. When she was a child, she had to take a boat on a river to get to school. The Huazhong Agricultural University of China, where she receiver her bachelor of science degree, is located near a large lake. When she moved overseas to attend The Ohio State University for her graduate studies, she focused on what fish eat.
She began to study plankton, which means wanderer or drifter in Greek. The kinds of plankton she studied were all less than two mm and are looked at under a microscope.
There are three major types of plankton, Wu explained. The first is microbial, which are single cell bacteria with no nucleus. This type of plankton includes cyanobacteria, which is the blue-green algae that we may often recognize as surface scum in the water.
The second type of plankton is phytoplankton or plant plankton. It is autotrophic, which means it makes its own food.
Zooplankton is the third type. Like all other animals, it consumes food from others. The most interesting of these to Wu are the cladocera, which are relatives of shrimp and lobsters. “Their reproductive strategy is very adaptive to the environment,” Wu said. Sometimes cladocera reproduce asexually to increase the population, until it gets colder. Then, eggs are made and go to the bottom of the water until the next year.
One of the major roles of plankton is that they are producers, meaning they supply oxygen to the aquatic ecosystem. “They are almost as productive as the rain forest here on land,” Wu explained using a chart.
Plankton is also the base of the aquatic food chain. Phytoplankton are eaten by zooplankton, which are eaten by fish. They also play a role in the nitrogen cycle by changing into the ammonium form that plants can use.
Microbial plankton helps in decomposition, in which they recycle matters in the system. This can cause the problem of eutrophication. This means that there is too much nutrient in the water, causing the phytoplankton to grow too fast and inhibit sunlight penetration. Much phytoplankton dies so bacteria try to decompose the phytoplankton, which uses up a lot of oxygen.
Eutophication occurred in Lake Erie in the 1960’s and 1970’s. “The process was luckily able to be reversed by getting rid of the input of nutrients,” Wu said.
Plankton have also created fossil fuels. Millions of years after they have sunk to the bottom of the sea floor, dead phytoplankton and zooplankton decompose into bacteria, creating crude oil and natural gas.
Wu has been a member of the Mount Union faculty since 1998. Each year since 1959, a member of the Mount Union College faculty is selected to give a special lecture relating interesting or important developments in his or her own field or exploring matters of general concern to the faculty.