Water Quality & Management Flashcards

A pond manager observes a sudden pH rise to 10.5 during afternoon hours on a clear summer day. The most likely cause is:

Answer: Intense phytoplankton photosynthesis consuming CO2

Dense phytoplankton blooms rapidly consume CO2 during peak afternoon photosynthesis, driving the carbonate equilibrium toward higher pH.

Which water quality parameter is used to calculate the un-ionized ammonia fraction from total ammonia nitrogen (TAN)?

Answer: Temperature and pH

The equilibrium between NH3 and NH4+ is governed by temperature and pH, with higher temperature and pH favoring the toxic un-ionized form.

Hypolimnetic oxygenation in a stratified reservoir is used to manage water quality by:

Answer: Adding oxygen to bottom waters without disrupting thermal stratification

Hypolimnetic oxygenators inject oxygen directly into the cold bottom layer, preventing anoxia and reducing internal phosphorus and manganese loading while preserving thermal structure.

Which metric best describes the potential of a water body to produce algal blooms based on nutrient availability?

Answer: Trophic state index (TSI) based on total phosphorus, chlorophyll-a, or Secchi depth

The Carlson Trophic State Index (TSI) quantifies eutrophication level using total phosphorus, chlorophyll-a, and Secchi depth as interrelated indicators of algal productivity.

Which NPDES permit condition specifically governs the quality of wastewater discharged from a fish hatchery into a US waterway?

Answer: Effluent Limitation Guidelines (ELGs) for aquatic animal production facilities

EPA's Effluent Limitation Guidelines for Aquatic Animal Production Facilities set technology-based discharge standards for suspended solids, BOD, and other pollutants from hatcheries.

A fisheries biologist collects water samples showing high total dissolved solids (TDS > 1,500 mg/L) in a stream receiving irrigation return flows. The primary concern for fish is:

Answer: Osmotic stress and reduced survival for freshwater-adapted species

Elevated TDS increases water osmolarity, forcing freshwater fish to expend more energy on osmoregulation and potentially causing chronic physiological stress or mortality.

Potassium permanganate (KMnO4) is used in aquaculture primarily to:

Answer: Oxidize organic matter, treat external parasites, and satisfy immediate oxygen demand

KMnO4 is a strong oxidant used to treat external bacterial and parasitic infections (e.g., Columnaris, gill flukes) and to reduce oxygen-depleting organic loads in hatcheries.