Bio test Limnology

Role of nutrients in aquatic ecosystems

Nutrients support the growth of aquatic plants and animals.

Micronutrient vs. Macronutrient

Micronutrients are needed in small amounts (e.g., iron), while macronutrients are needed in larger amounts (e.g., nitrogen).

Nutrients tested at Green Lake

We test for phosphorus, nitrogen, and other nutrients using water samples.

Dangers of high phosphorus levels

High phosphorus can lead to algal blooms, which harm water quality and aquatic life.

Carbon cycle

The carbon cycle describes how carbon moves between the atmosphere, land, and water.

Phosphorus cycle

The phosphorus cycle shows how phosphorus moves through soil, water, and living organisms.

Nitrogen cycle

The nitrogen cycle explains how nitrogen is converted between its various chemical forms.

Purpose of alum treatment at Green Lake

Alum was used to reduce phosphorus levels and blue-green algae blooms and improve water quality

Why living things need phosphorus and nitrogen

-Nitrogen forms the basis of amino acids and proteins

-phosphorus creates the structure of DNA, cell membranes, and ATP

How nutrients become usable

Microorganisms break down nutrients into forms that plants can absorb.

Turbidity

Turbidity is the cloudiness of water caused by suspended particles.

Difference between TDS and TSS

TDS — minerals, salts, and ions that are fully dissolved and cannot be seen or filtered out easily.

TSS — tiny particles like silt, clay, or organic matter that make water look cloudy and can be filtered out.

Sources of turbidity

Soil erosion — rain or wind washes loose soil into water.

Wastewater discharge — untreated or partially treated water adds fine particles.

Urban runoff — stormwater carries dirt, debris, and pollutants from streets.

Algae blooms — rapid algae growth increases cloudiness.

Sediment disturbance — activities like dredging, boating, or animals stirring up bottom sediments.

Measuring turbidity at Green Lake

Turbidity is measured using a

secchi disk.

Trophic state

Trophic state describes the nutrient status of a lake: eutrophic (high nutrients), mesotrophic (moderate), oligotrophic (low).

Aging process of a lake

Starts clear (oligotrophic) — few nutrients, little algae.

Gets more nutrients (mesotrophic) — moderate algae and plant growth.

Becomes nutrient‑rich (eutrophic) — lots of algae, murky water.

Eventually fills in — sediments and plants accumulate until it becomes swamp‑like.

Characteristics of lake types

Oligotrophic lakes are young and clear, mesotrophic lakes are middle‑aged with medium nutrients, and eutrophic lakes are old, murky, and full of algae

Water quality and trophic state

More nutrients = higher trophic state = worse water quality.

Cultural vs. natural eutrophication

Cultural eutrophication is caused by human activities(pollution, sewage etc)

Natural eutrophication occurs over time from gradual nutrient buildup

Human impact on eutrophication

Human pollution → extra nutrients → more algae → eutrophication

Development of a Dead Zone

Extra nutrients → big algae bloom → algae die → bacteria use up oxygen → oxygen drops → fish die = dead zone.

Calculating TSI of a lake

TSI helps assess lake health based on nutrient levels and productivity.