Populations

Mnemiopsis were jellyfish released into the Black Sea while the Black Sea was already facing problems due to increased inputs of nutrients. Eutrophication is an increase in the nutrient content of an ecosystem. Mnemiopsis increased rapidly causing zooplankton to decrease, phytoplankton to increase, oxygen concentrations to decrease, fish to decrease. Populations can change from birth, death, immigration, and emigration. Population dynamics are how populations change in abundance overtime. Population fluctuations are how the population changes in size, abundance, and numbers. Populations rise and fall about the mean. Population outbreak is when populations are exploding in numbers. Population cycles are alternating periods of high and low abundance occur after constant intervals of time. They may be caused by Internal factors (hormones or behavioral changes) or external factors (weather, food, predators).