Nutrient Loading
See nitrogen runoff. Read more about nutrient loading on This is from their website:

Nutrients are substances needed for growth. In the absence of nutrients, plants will stop growing and organisms higher up in the food chain will not have enough to eat to allow survival. Nutrients fulfill different roles. Some remain in the organism temporarily, others permanently – only to become available for a next lifecycle after the organism has died. As long as organisms live and die in the same region, nutrients will be available for generation after generation.
Due to human impact, the nutrient cycle has been disrupted. Artificial nutrients (fertilizers produced by the chemical industry and phosphates used in cleaning products), along with nutrients resulting from burning fossil fuels have substantially increased the quantity of nutrients on earth. Due to the spatial difference between agricultural land and food consumption in the cities, the distribution of nutrients is also disrupted. This situation is worsened due to international food transport. Nutrients are depleted in the soil of the producing countries (making them dependent on the fertilizer industry), while they accumulate in areas where the food is consumed.
Eventually most nutrients (mainly phosphate and nitrate) end up at “the end of the line” – aquatic systems. Loading aquatic systems with nutrients causes uncontrolled growth of algae. These algal blooms degrade the quality of the underwater ecosystems and thus the quality of our dive sites.
The consequences of nutrient loading differ from one location to the other. In coastal areas, dead zones can develop. Grave examples include the seasonal dead zone in the Gulf of Mexico and the enormous permanent dead zone in the Baltic Sea. The number of such dead zones seems to double in number every 10 years. In such dead zones, no bottom life or fish can survive. Other aquatic systems can collapse to a state in which they become sort of a green pea soup in which only algae in bacteria can live. Coral reefs can be destroyed by a cover of algae, when algae and bacteria growth outpaces algae consumption.
The best way to prevent this sort of problems is to reduce the amount of nutrients flowing into aquatic systems. In developed countries waste water is largely cleaned of nutrients before it is disposed of. Still nutrient levels are rising in many locations. Run-off and atmospheric deposition are amongst the reasons for this rise. Next to prevention, curative measures are possible to some extent. Buffer zones where plants are removed on a regular basis or alterations in the food chain of a lake (bio manipulation) are examples.
The presence of nutrients can go largely undetected until it is too late. Nutrients are not visible and water probes must be analyzed to obtain data. Only with knowledge of the condition of an aquatic system, action can be taken. This program is designed to allow divers to assume an active role in the care for their favorite dive sites.
After a comprehensive course on the mechanisms behind nutrient loading and on the procedures for measurements, groups of divers adopt dive locations where water samples are taken and analyzed on a regular basis. The data are shared on this internet page and used to inform the public and local authorities on the situation and (if needed) on actions to be taken to prevent a collapse of the aquatic system. Knowledge of the mechanisms behind the problem, combined with data on the actual condition of the dive site provides a strong basis for preventive and curative action.
Read more in our information brochure or contact your local dive operation to get involved.