Biology 2483A Chapter 10: Ecology Chapter 10.pdf
23 Oct 2013
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Nutrient inputs had been reduced and phytoplankton abundance decreased: another comb jelly had arrived, beroe, which feeds almost exclusively on mnemiopsis. Within 2 years, mnemiopsis numbers plummeted: the mnemiopsis decline led to a rebound in zooplankton abundance and increase in native jelly sh species, there was also an increase in anchovy catches for commercial shermen. Events in the black sea ecosystem illustrate two types of causation in ecological communities: Bottom-up control increased nutrient inputs caused eutrophication and increased phytoplankton biomass, decreased oxygen, sh die-offs, etc. Top-down control top predators control the abundance of populations: over shing was also a factor in the black sea: decline of top predator sh leads to increase in plankton-eating sh, which decreases zooplankton populations, and then phytoplankton abundance increases. Population dynamics: the ways in which populations change in abundance over time: population size changes as a result of four processes: birth, death, immigration, and emigration.
