Nutrient cycling is an important service related to the provision of clean, fresh water in ecosystems (Taguchi & Nakata).The role of the nutrient cycle is to provide an appropriate balance of life’s most essential elements. There are thirteen macronutrients, the elements most necessary for plant growth. The cycle of four specific elements is considered key for fertility; carbon, nitrogen, phosphorus and sulfur (Luvalle, Dugdale, Scholes). These are also the elements most effected by human activities. Below is a simplified diagram of the nutrient cycle in an aquatic ecosystem.

Before human activities, the nutrients available in an ecosystem depended on the geomorphology of that system (Johnson, 2008). Elements were very slowly pushed upward by geological processes, towards the Earth’s crust. Through extremely slow weatherization and decomposition mineral elements would become available to plants in the soil. Through processes of decomposition, production and consumption, nutrients would be cycled through the land. Atmospheric depositions occurred through precipitation and absorption at the water’s surface (Paul & McGinley). Elements were transferred from land by wind and water erosion. Without the addition of a significant amount of nutrients from an outside source, ecosystems were able to maintain a healthy balance of nutrient through the nutrient cycle.

However, human activities, especially since the Industrial Revolution, and some would argue the Agricultural Revolution, humans have been constantly injecting additional elements into the nutrient cycle. Nitrogen levels have been dramatically increased by the use of synthetic fertilizers. The nitrogen-cycle has been altered by the addition of synthtic nitrogen from agriculture (Luvalle, et al). The emission rates have far surpassed the rate of dentrification. This has led to an accumulation of nitrogen in both soils and water-bodies. This accumulation has allowed for massive increases in agricultural productivity at the expense of ecosystem services. Namely, water quality, fisheries and recreational value of aquatic ecosystems.

The same pattern is true for phosphorus, sulfur and carbon levels. Phosphorus is the most problematic nutrient in Lake Champlain.  Excessive nutrient loads in lake ecosystems can lead to eutrophication, a situation in which high primary productivity rates lead to the depletion of oxygen in the water.  The result is equal to a dead zone, organisms begin to die from lack of oxygen (Paul & McGinley, 2007). Three of the five segments of Lake Champlain suffer from nuisance algae, caused by high levels of phosphorus, for nearly half the year. Over 90% of the phosphorus input comes from non-point sources such as agriculture and urban runoff (LCPB).

Without nutrient cycling, life as we know it would not exist. It contributes to the supply of fresh, drinkable water that all humans depend on. In this sense, the nutrient cycle in invaluable. It is vital to survival. (Ecosystems and Human Wellbeing)

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