Mnemiopsis

Mnemiopsis (comb jelly) are species of jellyfish native to the Atlantic Coast that became an invasive species released into the Black Sea. At the time, the Black Sea was already facing problems due to increased inputs of nutrients. This process is called eutrophication, an increase in the nutrient content of an ecosystem. Mnemiopsis is a carnivore that feeds primarily on zooplankton. Mnemiopsis increased rapidly causing populations of zooplankton to decrease, phytoplankton to increase, oxygen concentrations to decrease, and fish to rapidly decrease. This is an example of how populations change. Populations can change from birth, death, immigration, and emigration. Population dynamics and fluctuations are how populations change in abundance overtime, and may rise and fall about the mean. In 1989, the population of comb jelly had reached the highest levels, causing a massive drop in populations of other species. This was an example of population outbreak which occurs 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).