Fact sheet: These things we know.
Source: The Oregon Conservation Plan.
What does a healthy pond look like?
A healthy pool of fresh water functions as a habitat for a chain of diverse species beginning with bacteria and that support plants, insects, fish, and wildlife. Fresh water pools are crucial for many at-risk species. They provide crucial breeding habitat for amphibians, freshwater mussels and other invertebrates. Water quality can be measured by cool water temperatures (less than 59 degrees), and appropriate levels of dissolved oxygen (more than 8 mg/l). In a healthy pond near the Willamette River we will see many species below, some of which are listed as indicator species by the Oregon Conservation Plan:
- Red-osier dogwood
- Pond weed.
- Sedges, rushes
- Red-legged frog
- Pond turtle
- Western painted turtle
- Yellow –legged frog
- Little willow flycatcher
- Streaked horned lark
- Yellow breasted chat
- Acorn woodpecker
- Short eared owl
- Grasshopper sparrow
- Western purple martin
- Western bluebird
- Western meadowlark
- Oregon chub
- Western Gray squirrel
What does an unhealthy pond/water body look like? What plants/animals live there?
In many locations stream flow and natural ponds have been altered by barriers (roads, dams, culverts) that can interfere with fish and wildlife migration. Channelization can restrict the natural ability of streams to meander and pool. Large, cool freshwater pools are in decline. A man made dam is particularly troublesome because it slows the natural movement of water, concentrates toxic materials, and exposes the pooled water to solar heating. These factors inhibit native plants and encourage invasive species. An invasive species does not simply coexist with native species, it dominates and eliminates native species creating a single species desert.
Often in warm pooled water algae blooms in abundance, dies, sinks under the water and is decomposed by bacteria. The bacteria use oxygen during the decomposition and the warm water becomes oxygen deficient for other aquatic life. We often see the following invasive species around unhealthy ponds:
- English Ivy
- Yellow flag iris
- Reed canary grass
- Japanese Knotweed
- Herb Robert
- Abundant algae
- Red eared slider turtles
- Snapping Turtles
- House sparrows
- Eastern Gray Squirrel
Facts about Artificial ponds
- Dams are barriers to aquatic wildlife.
- Dammed ponds heat water and reduce water quality in rivers and streams.
- Dams have a life span because of siltation.
- Siltation concentrates toxic chemicals and heat.
- Dammed ponds need to be managed to control water movement and remove invasive plants and wildlife.
- An artificial pond is not a wetland.
- Native wetland plants remove toxic chemicals and heat from the water.
- Wetlands store water in the soil for release during the dry season.
- The soil absorption of water reduces flooding in the wet season.
- Wetlands are inundated seasonally, but dry out in other seasons.
- Wetlands are often connected to rivers as riparian areas or floodplains.
- Beavers often ‘manage’ wetlands. Their dams moderate water flows and increase area for riparian plants.
- Wetlands provide habitat for bitterns, shore birds, rails and flycatchers.