Nutrients

Under the heading of nutrients we have included fertility as the two are so closely interrelated. The nutrient section mainly deals with the classification of waters and there relevant titles, whilst fertility looks more closely at the mineral effects found within ponds.

Nutrients

Nutrients are found within the ponds from two main sources - those which are the natural by-product of the food cycle, and those which enter from an external
source. Normally the latter of the two is the most troublesome and can cause the natural cycle of the pond to be disturbed and an imbalance occur.
The volume of nutrients found within a water body are what are normally used to classify its current status. The descriptions of these are listed below.

1.Dystrophic.
The water in this form of pond is often composed of peat and is soft and acid, which can give the water a brown colour. It contains very little plant life, or any of the higher species, and presents very difficult conditions for survival of it's inhabitants.

2.Oligotrophic.
Oligotrophic ponds are those that are nutrient poor and so don't have much of a problem with algal blooms, or large plant masses. Normally the fish life tends to be Salmonids with lower populations due to the reduced amount of available food.

3.Mesotrophic.
This is the name used to define the ponds that, although at a more advanced stage than the oligotrophic, are able to sustain an increased biomass.
These can be considered neither nutrient rich or poor, and are the intermediate stage between oligotrophic and eutrophic.

4.Eutrophic.
Finally we come to the eutrophic waters. These are rich in nutrients and contain large plant masses and are prone to algal blooms. They normally also have larger populations of fish species due to the availability of food supplies.

The pond's setting can greatly effect which category the pond is likely to fall within. Those found within the high mountain ranges where peat bogs are found
tend to fall within the dystrophic group, while those in lowland areas where agriculture is prominant are often eutrophic. That is not to say that this is always the case and often the deciding factor can be outside nutrient sources.

Fertility
Fertility is an array of minerals required for the growth of plants and algae. These include nitrogen, phosphorus, potassium, iron, carbon, and several others which are also necessary, but in trace amounts. A deficiency in the array can occur, in which case the deficient mineral is said to be "limiting" since the pond may appear to be less fertile than its potential. Since most minerals are required in trace amounts and are likely to be adequate, the limiting minerals in a pond are likely to be nitrogen or phosphorus. The presence of these "majors" in sufficient amounts will most likely produce a well-vegetated pond, and a surplus will create a "eutrophic", or well-fed pond. Eutrophic ponds tend to be very productive; in surplus this creates excessive growth and will accelerate the ageing process. The activity of man in modern times has promoted excessive fertility in water that drains urban and agricultural lands. Chemical fertilizer, construction related erosion, livestock manure, and inadequately stripped sewage can enrich the water draining into a pond from distant areas. Locally, the feeding of the fish in a pond will recycle the minerals into the system.

An infertile pond would be expected to have minimal green coloration of the water caused by microscopic algae, and have a modest amount of plant growth in the water. The watershed would be expected to be well-vegetated with an undisturbed woodlands, lightly grazed grasslands, or a wetlands area that filters fertility from water migrating toward the pond.

A eutrophic pond would tend to have one or more of the following traits: green water, filamentous algae mats, excessive submersed plant growth, or a covering of floating plants such as duckweed or azolla. The production of chlorophyll, in some form, would be profuse in the absence of adverse conditions such as toxins or soil turbidity.