Chapter 3.3, Problem 6MI

Summary Introduction

To compare:

The zones of lakes and ponds by completing the given table.

Introduction:

Major freshwater ecosystems are ponds, lakes, streams, rivers and wetlands. An inland body of standing water is called a lake or a pond. Some ponds have water for few weeks or months each year while some lakes have water for hundreds of years. Mixing of the warm and cold water from top and bottom layers of lake results in uniform temperature of water. This mixing circulates oxygen and nutrients.

Answer to Problem 6MI

Zone	Location	Example Species
Limnetic	Well- lit open water area	Plankton and many species of fish
Profundal	Deepest areas of a large lake	Limited due to cold and reduced light and oxygen
Littoral	Closest to shore	Algae, rooted and floating plants, insects, clams, fishes, amphibians, crustaceans and snails

Explanation of Solution

Lakes and ponds are divided into three zones based on the amount of sunlight that penetrate the water.

1. The area closest to the shore is called the littoral zone. The water in this zone is shallow and allows sunlight to reach the bottom. Many producers like aquatic plants and algae, live in these shallow waters. This is the area of high photosynthesis. Many consumers like frogs, turtles, worms, crustaceans, insect larvae, and fish also live here.
2. The limnetic zone is the open water area that is well lit and is dominated by plankton. Planktons are free- floating photosynthetic autotrophs that live in marine and fresh water ecosystems. Many species of fish also live here because food (planktons) is readily available.
3. The water of the profundal zone is deepest areas of a large lake. It is much colder and low in oxygen content. Very little light is able to penetrate the limnetic zone to reach this zone thereby, limiting the growth of species here.