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Trophic C ascades and Their E cological E ffects

This study investigates the population dynamics of cod (Gadus morhua) in the Baltic Sea, specifically the Main Basin and the Gulf of Riga. Researchers, led by Michele Casini, examine how cod acts as a keystone species, influencing the populations of herring and zooplankton through top-down control. The study highlights the concept of spillover, demonstrating how an abundance of cod in one area can significantly affect interlinked food webs and ecosystems. These findings emphasize the interconnectedness of marine species and the ecological balance crucial for sustaining biodiversity.

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Trophic C ascades and Their E cological E ffects

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  1. Trophic Cascades and Their Ecological Effects Group B20 Su Yong Han, Timothy Mettille, Jon Wroblewski, Katelyn England

  2. Background (Casini et al. 2012) • The focus of Michele Casini and other’s study is the population of cod in the Baltic Sea in Northern Europe • Difference in number of cod in Main Basin and Gulf of Riga • The cod migrate to the Gulf of Riga when there is an overabundance of cod

  3. Important Terms • Trophic Cascade (Freeman 2011) • Keystone Species (Freeman 2011) • Spill Over (Casini et al. 2012)

  4. Important terms • Top-Down Control (Freeman 2011) • Density Dependent Factors (Freeman 2011) • Density-Dependent Ideal Free-Distribution Theory (Casini et al. 2012)

  5. Procedure (Casini et al. 2012) • Michele Casini and team looked at both the Gulf of Riga and the Baltic Mason Basin for the reaction of the spilling over of cod. • They took the biomasses of herring, zooplankton, and phytoplankton in the Gulf of Riga before the introduction of cod and then again when cod was spilled over, including the biomass of the cod. • This showed how spilling over effects can intertwine two ecosystems and food webs that would usually be isolated.

  6. Data and Results This data demonstrates a chain reaction of events that occurs in the ecosystem.

  7. Data and results Shows all relationships in the area, both positive (blue arrow) and negative (red arrow)

  8. Discussion • Keystone Species (Mills et al. 1993) • A change in keystone species results in “dramatic changes result in the varieties and population densities of all the other species in the community” • The cod acts as the keystone species because it’s presence greatly affects the other species in the ecosystem

  9. Discussion • Top-Down Control (Casini et al. 2012) • The population of herring is controlled by population of cod • The population of zooplankton is controlled by the population of herring

  10. Discussion • Density-Dependent Ideal Free-Distribution Theory (Casini et al. 2012) • Because the location of the cod depends on the number of cod, this is a density dependent characteristic • As the number of cod in the main basin increase, the cod move into the GoR which is a less suitable habitat

  11. Take Home Message Competition: You can’t always get what you want.

  12. Literature Cited Casini,Michele, et al. 2012. “Predator Transitory Spillover Induces Trophic Cascades in Ecological Sinks.” Proceedings of the National Academies of Science 109 (21): 8185-8189 Freeman, Scott. Biological Science. 4th ed. San Francisco: Pearson, 2011. Print. L. Scott Mills, Michael E. Soule, and Daniel F. Doak. 1993. “The Keystone-Species Concept in Ecology and Conservation,” BioScience, 43 (4), 219.

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