A study examining tiny water fleas is helping scientists understand the global effects of environmental change on population dynamics.
Published last week in the academic journal Nature, the report uses field research, experimental data and mathematical models to follow the population of Daphnia, or water fleas, and subsequently predict ecological variability.
Roger Nisbet, a professor and vice chair of UCSB’s Ecology, Evolution & Marine Biology Dept., co-published the report with the help of William Nelson from Queen’s University in Ontario and Edward McCauley from the University of Calgary.
Nisbet said of all the possible organisms, the water flea was chosen as a test subject due to its abundance in nature.
“We chose to work on Daphnia because they are a very common type of zooplankton, very ecologically important,” Nisbet said. “Daphnia are responsible for a lot of clear water. Daphnia eat all the algae. … That’s why lakes are [seasonally] clear.”
Populations in nature tend to remain relatively stable, but occasionally show what Nisbet calls “boom and bust” situations where the population spikes and drops suddenly due to environmental factors. The spikes tend to occur when a large amount of resources are available, and the sudden declines when resources are expended before they can regenerate.
“An example of a boom would be an outbreak of insect pests. A famous example would be forest insects,” Nisbet said. “[Booms and busts] are normally associated with undesirable phenomena.”
However, while some populations exhibit “boom and bust” dynamics – particularly those inhabiting high-resource environments with access to large amounts of food – other populations do not follow this pattern. The study sought to determine why.
“The goal was to understand why many populations in nature appear to be reasonably stable,” Nisbet said. “The second goal was to understand how the food environments impacted the stability of populations.”
The study concluded the availability of food in a given environment ultimately determines population change.
“In the boom-bust population, more of the animals were developing fast, while in the model with stable behavior they developed slowly,” Nisbet said. “With lots of food, it took 10 days [for the fleas to develop]. With low food it took 30 to 40 days.”
According to Nisbet, the mathematical model he developed has the potential to forecast possible consequences of environmental change on populations. Nisbet said his study will open new doors in ecological research and permit scientists to better understand population dynamics.
“[The study] has demonstrated that you can use mathematical models in ecology to make a good projection,” Nisbet said. “Mathematical models, laboratory experiments and field studies; together they give more [detail] than any one [alone] can give.”
Nisbet is currently involved in studying the population dynamics of coral fields and the safety of nanoparticles in the environment. His study on population dynamics in relation to climate change is still in progress.