Cultural eutrophication leads to an exhaustion of oxygen supply in the water. Cultural eutrophication leads to a rapid increase in fish diseases that are the cause of the decline in fish populations. Positive feedbacks lead to an acceleration in the rate of the forward reaction. Negative feedbacks rarely occur in living systems. In a negative feedback a low availability of the first substrate in a metabolic pathway stops the forward reaction.
Negative feedbacks generate instability in systems.
In a positive feedback the rate of the forward reaction in a metabolic pathway is reduced. An example of isostatic rebound is the rise in sea level of Hudson Bay. The last 100,000 years are called the Holocene Period. In permafrost soils only moisture is frozen. The Younger Dryas Period was a warm interstadial.