Take a close look into a pond. See any tiny creatures hiding under the water? Aquatic insects can reveal a lot about the water quality and ecology of a small pond. By using a pond dipper and a magnifying glass, the water gardener can discover the micro-level ecology of the pond and learn a lot about how the pond ecosystem works.
Many aquatic insects cannot live in water that is polluted. While chemical water quality tests for pH and oxygen can reveal a lot about the health of a pond, one of the first steps to a deeper understanding of water quality is to find, examine, and count aquatic invertebrates. The presence of pond animals that can only survive in clean water is a good indicator that all is well in the small pond.
Caddisflies: Masters of Camouflage
Caddisflies are amazing creatures to watch. They are one of the few silk-spinning creatures, a member of the order Trichoptera. The other silk-spinners are members of the order Lepidoptera, more commonly known as moths and butterflies.
Caddisflies create a silk sock around their bodies, to which they attach leaves, rocks, shells, needles, and sticks. They easily camouflage against the bottom of a pond or a stream. Look closely and quietly at the sticks at the bottom of the pond. When one appears to be moving steadily across the bottom, it is likely a caddisfly.
Caddisflies can only live in clean or very slightly polluted water. The water garden that is home to caddisflies may also be suitable habitat for larger creatures that are sensitive to pollution, such as frogs and salamanders.
The Whirring Dragonfly, Colorful Pond Predator
Dragonfly larvae are easy to spot. They look like miniature alligators or even dragons. Adult dragonflies are beautiful to watch and come in a myriad of colors and patterns. Watching adult dragonflies is a favorite sport of pond naturalists. While they look delicate as adults, the dragonfly larva is actually a fierce predator that can eat other aquatic insects and will even eat small fish!
These members of the Order Odonata can survive only in water that is clean or very slightly polluted. The presence of dragonfly larvae also means that there is an active population of prey animals. A strong pond food chain means that larger predator animals like fish and birds have a greater chance of surviving and thriving in the small water garden.
The Predaceous Diving Beetles, Stealth Predators
The members of the diving beetle order Dytiscidae are inch-long powerhouses.The larvae of diving beetles are known as water tigers for their predatory behavior. These larvae camouflage themselves on plants and sticks, waiting for their prey, then pounce to catch it by surprise. The dark-colored adults are noted for their ability to dive with their own air packet held next to their body.
Skim the surface of the pond with a dip net, wash it gently in a bucket, and examine the water to discover if there are diving beetles in the pond. The presence of diving beetles indicates that the pond has good water quality, since these animals can only survive in clean water.
Pond water quality does not need to be a mystery. Use a dip net and a bucket as a simple water testing kit. The animals in the pond will reveal how well the pond is doing and provide an easy first step in water quality monitoring.
Tricia Edgar - Tricia Edgar is a gardener, environmental educator, and science writer from the Pacific Northwest.
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