Source-sink Dynamics Affect on Trophic Cascades

By Group A33:Rachel ConfortoThomas FontanaJason MaliaDomingo UcedaMartin Yeh

http://wwf.panda.org/what_we_do/where_we_work/baltic/?uNewsID=199972 http://www.maretarium.fi/mare/kala_uk.php?id=203

Source Sink Dynamics Theoretical model that ecologists use. Model accounts for the fact that

habitats are not perfectly designed for a specific organism. “source” - high quality spots of the

habitat that allows the population size to increase

"sink” - low quality spots of the habitat that on its own would not be able to support the population.

Trophic Cascades Occurs as a result of the food chain and

predation. Introduction or removal of a part of the

chain can alter the whole cascade. Can alter both the abundance and the

habits of the organisms at different trophic levels.

When a predator limits its prey's population, the system is under top down control.

Humans can affect Trophic Cascades through removal of predators

Case Overview Favorable breeding conditions and low rates of  fishing in

the late 1970’s  led to over abundance of the species Cod in the Baltic Main Basin.

“Spillover effect” or migration of Cod into the Gulf of Riga.

In the mid 1980’s over-fishing in the Baltic Main Basin decreased abundance in the source habitat of Cod.

The Cod retracted back into Main Basin from the Gulf of Riga sink habitat.

Case Overview

Data was collected analyzing the source-sink dynamics between the Baltic Main Basin and Gulf of Riga.

Trophic cascades caused by top-down effects

Led to fluctuations in biomass & population size of herring and zooplankton in Gulf of Riga.

 

 

 

 

Discussion Migration and disappearance of cod

paralleled by decrease and increase in the population size of herring.

Variation in herring population inversely reflected in zooplankton populations.

Variations were observed in phytoplankton populations.

Conclusion

Humans can have a dramatic impact on ecosystems via human exploitation of organisms/resources.

Key species role in ecosystems and how the flow of organisms across systems affects food-web dynamics.

Literature Cited Freeman, Scott. Biological Science, 4th ed.; Benjamin

Cummings, 2011: pg 1083-87.

Casini, Michele et al. "Predator transitory spillover induces trophic cascades in ecological sinks." PNAS vol. 109 no. 21 (2012): pg 8185-89.

Fox, Jeremy W. "Testing The Mechanisms By Which Source-Sink Dynamics Alter Competitive Outcomes In A Model System." American Naturalist 170.3 (2007): 396-408.