Eutrophication of lakes. Some lakes also demonstrate the reverse process (meiotrophication), becoming less nutrient rich with time. The main difference between natural and anthropogenic eutrophication is that the natural process is very slow, occurring on geological time scales. Eutrophication is a common phenomenon in coastal waters. In contrast to freshwater systems, nitrogen is more commonly the key limiting nutrient of marine waters; thus, nitrogen levels have greater importance to understanding eutrophication problems in salt water. Estuaries tend to be naturally eutrophic because land-derived nutrients are concentrated where run-off enters a confined channel. Upwelling in coastal systems also promotes increased productivity by
Natural foods the term if the food does not contain added color, artificial flavors, or synthetic substances." Furthermore, the FDA has not developed any rules or regulations on the defining features of what qualifies a product as "natural." The FDA does reference a definition of "natural" in their informal policy (Ref. 53) that defines "natural" as "nothing artificial or synthetic (including colors regardless of source) is included in, or has been added to, the product that would not normally be expected to be there." The Food, Drug, and Cosmetic Act prohibits labeling that is false or misleading. The USDA's Agricultural Marketing Service