Water Quality & Ecosystem Health
Which organism is often used as a bioindicator of good water quality?
A. Leeches
B. Mayfly larvae
C. Mosquito larvae
D. Tubifex worms
B. Mayfly larvae
A pH value of 7 is considered:
A. Acidic
B. Basic
C. Neutral
D. Alkaline
C. Neutral ✅
Dissolved oxygen (DO) is most important for:
A. Plant photosynthesis
B. Aquatic animal respiration
C. Water clarity
D. pH balance
B. Aquatic animal respiration ✅
Which organism primarily uses nitrates and phosphates?
A. Fish
B. Bacteria
C. Algae
D. Zooplankton
C. Algae ✅
Which property measures how cloudy water is?
A. pH
B. Turbidity
C. Conductivity
D. Dissolved oxygen
B. Turbidity ✅
Nonpoint source pollution is best described as pollution that:
A. Comes from factories
B. Is discharged through pipes
C. Has no single identifiable source
D. Is illegal
C. Has no single identifiable source ✅
Which nutrient commonly causes eutrophication when present in excess?
A. Calcium
B. Sodium
C. Phosphate
D. Chloride
C. Phosphate ✅
Which process consumes dissolved oxygen?
A. Photosynthesis
B. Respiration
C. Diffusion
D. Precipitation
B. Respiration ✅
Eutrophication most often occurs in:
A. Fast-moving streams
B. Deep ocean waters
C. Nutrient-rich lakes
D. Polar regions
C. Nutrient-rich lakes ✅
What instrument is used to measure water turbidity in the field?
A. Secchi disk
B. Thermometer
C. pH probe
D. Titration kit
A. Secchi disk
Which land use is most likely to increase sediment runoff?
A. Forest
B. Wetland
C. Agriculture
D. Construction sites
D. Construction sites ✅
High nitrate levels in water are often linked to:
A. Road salt
B. Fertilizer runoff
C. Industrial cooling
D. Groundwater evaporation
B. Fertilizer runoff ✅
BOD stands for:
A. Biological Oxygen Demand
B. Baseline Oxygen Deficit
C. Bacterial Oxygen Density
D. Balanced Oxygen Distribution
A. Biological Oxygen Demand ✅
Which nutrient is usually the limiting factor in freshwater systems?
A. Nitrogen
B. Carbon
C. Phosphorus
D. Oxygen
C. Phosphorus ✅
High turbidity in water is most likely caused by:
A. Dissolved salts
B. Suspended sediments
C. High oxygen levels
D. Low temperature
B. Suspended sediments ✅
Which water quality change most directly affects fish gill function?
A. pH shifts
B. Turbidity increase
C. Dissolved oxygen decrease
D. Nutrient enrichment
C. Dissolved oxygen decrease ✅
Which form of nitrogen is most toxic to aquatic life?
A. Nitrate
B. Nitrite
C. Ammonia
D. Nitrogen gas
C. Ammonia ✅
High BOD levels usually indicate:
A. Clean water
B. Cold water
C. Organic pollution
D. High salinity
C. Organic pollution ✅
What is a common result of excessive algal growth?
A. Increased biodiversity
B. Higher pH stability
C. Oxygen depletion
D. Reduced temperature
C. Oxygen depletion ✅
Which unit is commonly used to measure conductivity?
A. NTU
B. mg/L
C. µS/cm
D. °C
C. µS/cm ✅
A healthy aquatic ecosystem typically shows:
A. High nutrients and low DO
B. Low biodiversity
C. Stable pH and high DO
D. Frequent algal blooms
C. Stable pH and high DO ✅
Which chemical parameter directly affects metal solubility in water?
A. Temperature
B. Turbidity
C. pH
D. Dissolved oxygen
C. pH ✅
A sudden drop in dissolved oxygen is most likely caused by:
A. Increased water flow
B. Algal die-off and decomposition
C. Reduced turbidity
D. Decreased nutrients
B. Algal die-off and decomposition ✅
Which human activity most contributes to cultural eutrophication?
A. Mining
B. Wastewater discharge
C. Agricultural runoff
D. Urban shading
C. Agricultural runoff ✅
An increase in water temperature generally causes dissolved oxygen to:
A. Increase
B. Stay the same
C. Decrease
D. Fluctuate unpredictably
C. Decrease ✅