DECEMBER 3RD, 2019
An Investigation by Hawera Christian School - Habitat Heroes:
- Sienna MacRae
- Alex Langdon
- Olivia Corrigan
- Emma Langdon
- Suzy Corrigan
Authored by: Sienna MacRae, Alex Langdon
AIM: To determine the health of the stream at Nowell’s Lakes Walkway. METHOD: A 30 m length of stream was divided into 3 sections.
UPPER SECTION: This section was open, flowing water. The stream was 30cm deep, vegetation partly shaded the stream but did not completely overhang the water. MID SECTION: This section was deep at 40cm. The water was weed covered and overgrown, but there were no big trees overhanging it. DOWN STREAM SECTION: This section was about 20-30 cm deep, but was fully enclosed with little free flowing water and was very weedy.
1) Water temperature reading: A thermometer was used to read the temperature. The thermometer was held in the water for 30 seconds before reading. Upstream 18 degrees Midstream 18 degrees Downstream 18 degrees. The weather the preceding week had been very warm. Optimal stream health should be around average of +15C.
2) This was a survey of fresh water crayfish in all three parts of the stream and bucket sample of water determining invertebrate life. The results were UPSTREAM: At this site we found multiple freshwater small and medium crayfish, around 20 backswimmers and 2 snails. MIDSTREAM: At this site we found big water spider, 15 backswimmers and a few crayfish. DOWNSTREAM: At this site we found 1 large crayfish (14 cm) and 6 backswimmers.
OTHER FACTORS: Wind drift from the nearby Fonterra factory could be blowing milk powder dust into the area and providing extra nutrients for the crayfish. One Koura we found was larger than usual size supporting this theory. Milk powder in the water could also be toxic to wild life. When the fish produce babies, the toxins may cause breeding problems and defects, and may affect the future crayfish community.
NZ CRAYFISH / KOURA NZ crayfish can be fresh water ones and salt water ones. We did our study on fresh water ones. They live in fresh water under weeds, hiding in the mud surface. They only meant to grow up to 12 cm and we found some up to 14 cm which is not normal. They are quite independent creatures, and the bigger ones can scare the smaller ones away. They eat the weeds and little backswimmers.
OUR CONCLUSION: We are concerned that the stream may not be as healthy as it could be. It seems healthy but the larger sized Koura and the warm water temperatures indicate that further in-depth study may be required to see if the stream has some pollution. We need to stop polluting our rivers, streams and seas because it affects the life of the creatures that live there – it poisons their environment and even if they survive and produce young ones, it has an effect on them. Big factories should pay attention where their vents are and monitor the air quality around them, to make sure they are not polluting the environment.