Slurry
produced by intensive pig farming can be a serious pollutant. As well as the
high nutrient content, organic matter in the slurry causes a high biochemical
oxygen demand.
Eutrophication
is a natural process that can be greatly accelerated by human influence.
The nutrient
status of the broads increases. This
is caused naturally by input of sediment and plant
and animal material.
The change is from oligotrophic
through mesotrophic
to eutrophic
conditions.
Accelerated
eutrophication is
caused by:
- increased use
of fertilizers
- effluent
from intensive
farming units
- nutrients
from
soil erosion
-
nutrients from
bank erosion
Eutrophication leads to
a decrease in species
diversity
Eutrophication
is the increase in nutrient status. Normally nitrate and phosphate ions increase.
This has an effect on the biotic environment.
The
nitrate levels vary. Eutrophic water in the dykes sampled at Carlton marshes
contained up to 25mg/l nitrate whereas the oligotrophic dykes contained no nitrate.
A typical level for the mesotrophic waters was 5 mg/l.
Oligotrophic
lakes have low nutrient status. Species diversity is high but population sizes
and productivity are low. Oligotrophic lakes tend to be found in upland, acidic
environments. Some of the dykes at Carlton marshes are oligotrophic, they are
supplied with water that has percolated through peat. The water is acidic. Bladderwort
is found in these dykes. It traps insects in its bladders and obtains nutrients
from them.
Mesotrophic
waters have a relatively stable ecosystem. Management of the Broads aims to
create mesotrophic conditions.
Eutrophic
waters have high nutrient levels. Species diversity is low and population sizes
are high. Organisms are adapted to live in water that has low oxygen levels.
Inorganic
fertilizers contain nitrate, phosphate and potassium as well as other trace
elements. They can be leached easily from the soil and can be a major contributor
to eutrophication.
The
light peaty soils are easily moved by the wind. Removal of hedges in order for
bigger machinery to be used has added considerably to soil erosion. Eroded soil
ends up in the watercourses and adds to the nutrient levels.
The
Broads are popular tourist areas. Large numbers of pleasure craft use the Broads.
Excessive speed causes the banks to erode. Speed limits of 3 - 5 mph are enforced
in order to keep this to a minimum.
Sometimes
referred to as Hypertrophication. It is a problem on the Broads, human impact
is causing accelerated hypertrophication leading to deoxygenation of the water
and death of fish.