Eutrophication of Water bodies

Presented byBandhu Pd. BhandariTallinn university of Technology

Presented by

Bandhu Pd. Bhandari

Table of contents

• Introduction

• Mechanism

• Process and stages

• Causes and sources

• Main consequences

• Negative impacts

• Management

Introduction

• The word “Trophi” in Greek means food or nutrient, whereas the words “oligo”, “meso”, “eu” and “hyper” stand respectively for rare, moderate, abundant and excessive. Therefore, the words oligotrophic, mesotrophic, eutrophicand hypertrophic have been used by biologists to describe the various nutritional statuses of a marine or fresh water environment. These words are used to describe the potentially available quantitative biomass.

Trophic level and status

Classification of lakes on the basis of nutrients content

• Oligotrophic lake - low in nutrients, Productivity is low,Many species, low populations, Nice clean water.

• Mesotrophic lake - intermediate levels of nutrients,Plankton is intermediate, Some organic sediment andmoderately clear water.

• Eutrophic lake - rich in nutrients, low transparency,high plankton, less oxygen, and showing increasingsigns of water quality problems.

• Hypertrophic lake - very high nutrient concentrationswhere plant growth is determined by physical factors.Water quality problems are serious and almostcontinuous.

Eutrophication

• Eutrophication is an accelerated growth of algae on higher forms of plant life caused by the enrichment of water by nutrients, especially compounds of nitrogen and/or phosphorus and inducing an undesirable disturbance to the balance of organisms present in the water and to the quality of the water concerned.

• Human-caused, accelerated eutrophication is referred as cultural eutrophication.

Cultural Eutrophication

scenario leading to eutrophication

• The mechanisms that lead to eutrophication, i.e. to this new status of the aquatic environment, are complex and interlinked.

• The main cause of eutrophication is the large input of nutrients to a water body and the main effect is the imbalance in the food web that results in high levels of phytoplankton biomass in stratified water bodies. This can lead to algal blooms.

The process of Eutrophication

Causes of eutrophicationand supporting factors

• The enrichment of water by nutrients can be ofnatural origin but it is often dramatically increasedby human activities. This occurs almost everywherein the world.

main sources of nutrient input are: Runoff Erosion and Leaching from fertilized agricultural

areas Sewage from cities and industrial wastewaterAtmospheric deposition of nitrogen (from animal

breeding and combustion gases)Other point and non-point sources of pollutants

Causes of eutrophication

Sources of cultural Eutrophication

Main consequences of eutrophication

• Availability of oxygen: low volume of oxygen duemicrobial decomposition & respiration and all lifewill disappear.

• very specific smell of rotten eggs, originatingmainly from sulphur, will appear.

• Changes in algal population: Excessive growth ofmacroalgae, phytoplankton and cyanobacteria,algal bloom.

• Changes in zooplankton: decrease in fish andshellfish population, invertebrate etc.

Consequences cont.

• The direct consequence is an excess of oxygen consumption near the bottom of the water body.

• The ratio of nitrogen to phosphorus compounds in a water body is an important factor determining which of the two elements will be the limiting factor, and consequently which one has to be controlled in order to reduce a bloom.

• Generally, phosphorus tends to be the limiting factor for phytoplankton in fresh waters. Large marine areas frequently have nitrogen as the limiting nutrient.

Healthy system vs. Eutrophic system

Stages in EutrophicationPhytoplankton (low concentration) Phytoplankton (high concentration)

Dead fishes and crustaceans

Green filamentous algaeBottom anoxia

Anoxic waters with H2S bubbles

Epiphytes on focus

Pristine situation Start of eutrophication

Extreme eutrophication

Factors supporting the developmentof eutrophication

• Time of renewal of water

• Geological features such as the shape of the bottom of the water bodies

• Thermal stratification of stagnant water bodies (such as lakes and reservoirs)

• Temperature and light influence the development of aquatic algae

Potential negative impacts of eutrophication

• Trophic Status

• Ecological impact

• Economic impacts

• Human health impacts

• Recreational impacts

• Aesthetic impacts

negative impacts of eutrophication

Ecological impacts• Macrophyte invasions impede or prevent the

growth of other aquatic plants.• Only the more tolerant animal species can survive

due to algal bloom.• Turbidity of water increases• Release of cyanotoxins by cyanobacteria are

recognized to have caused the deaths of wild animals, farm livestock, pets, fish and birds in many countries.

• Decreased oxygen levels can have a number of secondary water quality impacts.

Cyanotoxin and Human health impacts• Cyanotoxins : Hepatotoxins (liver),

Neurotoxins (neuron), Dermatotoxins (skin)

• Affects in cells, tissues and organs

• Nervous, digestive, respiratory and cutaneoussystems

• Fatigue, headache, diarrhea, vomiting, sore throat, fever etc.

Management

• Monitoring

• prevention

Monitoring of eutrophication• To prevent the occurrence of eutrophication

• Early warning purposes to the Public health authorities

• To know the level of development of the process, and have a precise picture of the quality of the water.

• Research and multipurpose.

parameters used for monitoring purposes

• Nitrogen and phosphorus

• Suspended solids

• Dissolved oxygen

• Bacteria

• Algal or cyanobacterial biomass

• Development of short living species of macrophytes

Prevention

Identification of all nutrient sources

Catchment area of the water supply

Industrial activities, discharge practices and localization

Best agricultural practices (fertilizer contribution/plant use and localization of crops)

Nature of the soil, vegetation and the interaction between the soil and the water

Knowledge of the hydrodynamics

The way nutrients are transported, and of the vulnerability of the aquifer

Prevention cont.

• Fertilization balance for nitrogen and phosphorus

• Regular soil nutrients analysis

• Sufficient manure storage capacities

• Prevention of erosion of sloping soils

• Precise irrigation management and soil moisture control

• Reuse and recycling of water in aquaculture and agriculture.

• Thank you