Freshwater Stream

Introduction Date : 14/9/2005 Site location : Chuen Lung Time : 1:00 p.m to 3:00 p.m Weather condition : Sunny and Dry Water transparency : Fairly Clear Smell : No Special Smell Floating matters: Plastic bags, tin cans, glass bottles, decayed leaves

Stream Features Gradient along the transect Distance (m) Water depth(cm)

26.9 Bottom 30.5 Above surface Temperature ( degree Celsius ) 3875 Bottom 4125 Above surface Light intensity ( Lux ) Other features

Chemical oxygen demand (mg/l) Chemical factors Ammonium content(transparency) Phosphate content(ppm) pH Total dissolved solids (ppm) Total suspended solids (mg/l) Dissolved oxygen (mg/l)

Paramestorition hongkongensis ( 香港瘰螈 )  Large, brownish newt  Under with red blotches  A predator of various invertabrates  Commonest in stream from September to March, when breeding take place  Most of the time spent on land

Pseudogastromyzon myersi ( 麥氏擬腹吸鰍 )  Strongly flattened fish  Mouth on the underside of the head  Dorsal fin yellow with red border  Food: grazes algae any oyanobacteria ( 藻青菌 )

Ptilomera tigrina ( 水黽 )  Long-legged bugs with raptorial front limbs and a slender beak.  Live in the most rapid part of riffles, especially numerous around the base of waterfalls  Strong jumpers that easily avoid capture

Euphaea decorate ( 豆娘若蟲 )  Found under stones  Have gills along the sides of abdomen  Colour: Dark grey to black  Development takes one year

Euphaea decorate ( 豆娘 )  Males have a black band across the hindwings  Females have more yellow stripes on the body and lack the wing band  Common found between April and October

Heptageniidae ( 蜉蝣若蟲 )  Tends to remain clinging to stones picked out of the water  Distinctly flattened with oral heads and plate-like gills

Brotia hainanesis ( 海南蜷螺 )  Streamlined shell reduces impact of water current  Hard shell protects against predator  Operculum( 厴能 ) protects against predator  Found in fast running water and clean water

Marcrobrachium hainanense ( 海南沿蝦 )  Large chelate walking leg or defence against enemies  Found in slow running water and clean water

Conclusion Different animals have different features in order to adapt the environment. As the light intensity is relatively low, there are only small number of plants. There are many microhabitats along the transect line, e.g under stones. More animals can be found in slow running water. It is extremely important for us to protect the environment.

Cheung Lai Wan Lau Suk Yan Law Hoi Ling Lau Tsz Leung Leung Ka Man