The Mangatarere Ecosystem

Mangatarere Stream Ecology

The catchment area
Tararua CatchmentThe area that the Mangatarere stream drains is its catchment area, also called the watershed. Under normal conditions water always flows downhill (unless it evaporates, freezes, or is soaked up by plants) and the Mangatarere starts off as rain up in the foothills of the Tararua Ranges.

Stream water solid contents

Rainwater dissolves chemicals out of the rocks and soil that it flows over and through, as well as fine particles of the rock itself. It also carries organic matter like leaves, seeds, (for example  pollen)  bacteria, bugs, bird and animal droppings, and their urine. During a flood it can transport branches, mud, and even the rocks themselves.

The Tararua Ranges headwatersWind also blows organic and inorganic matter into the stream. Fish and some insects live in it, or use it for part of their life cycles. Birds can drop their feathers in it. Some animals drown in it,  adding their  decomposing organic matter to the water.
Transient effects like volcanic eruptions or forest fires can also temporarily add ash to the water.

 Dissolved gases
Pollution in the Mangatarere catchment Falling rain dissolves atmospheric gases from the air, like oxygen, carbon dioxide, and nitrogen. The colder the rain, the more it will dissolve. It also washes pollution out of the air - car exhaust, smokestack emissions and fossil fuel power stations are the biggest sources. Too much pollution in the air causes the phenomenon known as acid rain. Acid rain can corrode paint and worse still dissolve metals like aluminium and iron from the rocks, making stream water toxic to the fish that live in it, and anything that drinks it.   

The Riparian Corridor

The banks of a stream are called the riparian corridor. Plants and trees that depend on the stream for their water are called riparian plants. These plants and trees provide shade, food and habitats for the  animals, birds and fish that depend on the stream's ecosystem.