14 Surface Water Eutrophication in Poland: Assessment and Prevention
323
The supply of water vegetation with nutrients, the forms of their occurrence in
water and their availability for primary produces are the most important aspects in
investigation of eutrophication development. For autotrophic photosynthesis hydrobionts the main available forms of nutrients are inorganic nitrogen and phosphorus
compounds. Many authors notice [10–12] that the increased nutrient content in
water does not always lead to equivalent increase of aquatic vegetation development,
that indicates the existence of other factors limiting the biomass production. Such
factors include: temperature, degree of insolation, hydrodynamics, composition of
dissolved substances, trophic chains and competition between organisms. The interaction of these factors sometimes leads to unpredictable effects, which complicates
the assessment of individual factors impact.
With the increase of the rate of water plants biomass production, the rate of its
decomposition increases accordingly. The balance between the process of production
and decomposition of organic matter determines the trophic status of waters [3, 5,
6, 9]. The disturbance of this balance, which is called the biotic balance, its scale
and consequences are determined mainly by climatic, morphometric, hydrological,
hydrobiological and other characteristics of water ecosystems.
In the conditions of maintaining the homeostasis of aquatic ecosystems, these
processes are self-regulating and provide the appropriate level of biological productivity and water quality in particular ecosystem. The introduction of additional
anthropogenic nutrient loads to natural water environment, under the violation of
self-regulation mechanisms threatens the stability of aquatic ecosystem. Natural
eutrophication, as a rule, does not exceeds the homeostasis limits. But if eutrophication exceeds the limits of natural self-regulation, the changes may occur in biocenosis
structures, which lead to the intensive development of blue-green algae, fish kill and
other negative results. In the case of natural eutrophication, these changes are usually
temporary and ecosystem renews itself [13–15].
One of the serious problems of anthropogenic eutrophication control is that at the
initial stages of development the negative changes in aquatic ecosystems are hardly
noticeable due to homeostatic mechanisms. Such changes are difficult to distinguish
from natural changes, such as seasonal or annual fluctuations of different abiotic and
biotic factors. It is worth noting, that “water blooms” arising as a result of anthropogenic impact on the ecosystem represent its adaptation reaction, which means
that eutrophication can be considered a new stage of ecosystem development in new
conditions. From the point of view of the impact on water ecosystems, the pollution
and eutrophication are closely related and often mutually conditioned. In many cases,
eutrophication occurs as a result of pollution, and pollution may results from eutrophication. In natural conditions, both processes usually occur together. However, in
terms of the direction and degree of impact on aquatic ecosystem functioning, these
processes are substantially different. It should be particularly emphasized, that the
most important difference lies in the fact, that contamination is caused primarily by
the discharge of harmful substances, that often reduces the biological productivity of
waters, while eutrophication, conversely, leads to the increased productivity of water
[7].
323
The supply of water vegetation with nutrients, the forms of their occurrence in
water and their availability for primary produces are the most important aspects in
investigation of eutrophication development. For autotrophic photosynthesis hydrobionts the main available forms of nutrients are inorganic nitrogen and phosphorus
compounds. Many authors notice [10–12] that the increased nutrient content in
water does not always lead to equivalent increase of aquatic vegetation development,
that indicates the existence of other factors limiting the biomass production. Such
factors include: temperature, degree of insolation, hydrodynamics, composition of
dissolved substances, trophic chains and competition between organisms. The interaction of these factors sometimes leads to unpredictable effects, which complicates
the assessment of individual factors impact.
With the increase of the rate of water plants biomass production, the rate of its
decomposition increases accordingly. The balance between the process of production
and decomposition of organic matter determines the trophic status of waters [3, 5,
6, 9]. The disturbance of this balance, which is called the biotic balance, its scale
and consequences are determined mainly by climatic, morphometric, hydrological,
hydrobiological and other characteristics of water ecosystems.
In the conditions of maintaining the homeostasis of aquatic ecosystems, these
processes are self-regulating and provide the appropriate level of biological productivity and water quality in particular ecosystem. The introduction of additional
anthropogenic nutrient loads to natural water environment, under the violation of
self-regulation mechanisms threatens the stability of aquatic ecosystem. Natural
eutrophication, as a rule, does not exceeds the homeostasis limits. But if eutrophication exceeds the limits of natural self-regulation, the changes may occur in biocenosis
structures, which lead to the intensive development of blue-green algae, fish kill and
other negative results. In the case of natural eutrophication, these changes are usually
temporary and ecosystem renews itself [13–15].
One of the serious problems of anthropogenic eutrophication control is that at the
initial stages of development the negative changes in aquatic ecosystems are hardly
noticeable due to homeostatic mechanisms. Such changes are difficult to distinguish
from natural changes, such as seasonal or annual fluctuations of different abiotic and
biotic factors. It is worth noting, that “water blooms” arising as a result of anthropogenic impact on the ecosystem represent its adaptation reaction, which means
that eutrophication can be considered a new stage of ecosystem development in new
conditions. From the point of view of the impact on water ecosystems, the pollution
and eutrophication are closely related and often mutually conditioned. In many cases,
eutrophication occurs as a result of pollution, and pollution may results from eutrophication. In natural conditions, both processes usually occur together. However, in
terms of the direction and degree of impact on aquatic ecosystem functioning, these
processes are substantially different. It should be particularly emphasized, that the
most important difference lies in the fact, that contamination is caused primarily by
the discharge of harmful substances, that often reduces the biological productivity of
waters, while eutrophication, conversely, leads to the increased productivity of water
[7].