A shallow standing-water ecosystem has rooted plants from edge to edge and no deep, dark layer. What type of water body is it?

A student samples shallow water near a lake shore where cattails and other rooted plants grow. Which lake zone is being sampled?

An open, well-lit area of a lake lies away from shore and above the deep bottom water. Which zone is described?

Macroinvertebrates are collected from mud and decaying leaves on the bottom of a lake. Which zone is under study?

In a deep lake, fish occupy dark water below the depth reached by enough sunlight for photosynthesis. Which lake zone is this?

A developer drains a seasonally saturated area with water-tolerant plants to build parking lots. What aquatic ecosystem is being removed?

Freshwater from a river mixes with seawater, creating a habitat with changing salinity and tidal influence. What ecosystem is this?

A dam creates a deep body of standing water with an illuminated surface layer, darker deep water, and bottom sediments. How should it be classified?

A lake is clear and deep, has low phosphorus concentrations, and maintains high dissolved oxygen near its bottom in summer. What is its nutrient status?

Fertilizer runoff enters a lake, followed by dense algal growth and low dissolved oxygen near the bottom. How is the lake most likely classified?

Compared with a eutrophic lake, an oligotrophic lake usually has which condition?

Over thousands of years, a lake with no human nutrient inputs slowly fills with sediment and organic matter and becomes more productive. Which condition is it moving toward?

A town upgrades its wastewater treatment to remove more phosphorus before effluent reaches a eutrophic lake. Which change is most likely over time?

A lake has high biological oxygen demand after an algal bloom dies. Which explanation best connects this observation to eutrophication?

Two lakes get equal rainfall. Lake A is deep, clear, and nutrient-poor with sparse algae. Lake B is shallow and nutrient-rich with frequent blooms. Which lake more likely supports lake trout, which need cold, well-oxygenated water?

A large algal bloom collapses in a eutrophic lake that is stratified in summer. Where does dissolved oxygen usually fall the lowest?

A lake that receives excess nitrogen and phosphorus becomes more productive. Which observation would best confirm eutrophication?

A stream is cold, fast, shallow, and flows over large cobbles near its source. As it moves onto a broad plain, what change is most likely?

As a river moves from steep headwaters to a low-gradient floodplain, what usually happens to its bed material?

After a watershed is paved, rainwater reaches a nearby stream quickly instead of soaking into soil. During storms, what river change is most likely?

A city removes trees along a stream to widen a road. Which downstream water-quality change is most likely in summer?

Where along a river would a scientist most likely find the steepest gradient and fastest current?

A river slows as it reaches a lake. What is the most likely result for suspended sediment?

A wastewater discharge adds biodegradable organic matter to a river. What pattern is most likely just downstream of the outfall?

A river is channelized into a straight concrete course. Compared with a meandering reach, what is a likely effect during heavy rain?

A stream receives cool groundwater during a hot summer. Which effect is most likely where the groundwater enters?

In spring, a temperate lake's water has nearly the same temperature from surface to bottom. What does this allow?

During summer stratification in a temperate lake, which layer is warmest and closest to the surface?

What is the thermocline in a stratified lake?

Why does autumn turnover occur in many temperate lakes?