Week 4a- Water

The MCI test requires the identification of a number of different species which may be biological quality markers.  Species may be deemed "sensitive" (their presence indicating a high level of water quality), moderately sensitive or tolerant (whose presence would be expected in most streams).

Sensitive species include:

• Caddisflies - freeliving
• Caddisflies - cased
• stoneflies (see image)
• Freshwater mussels
• Freshwater crayfish

These species are only found in highly oxygenated water, mainly due to their poorly developed gills.

Moderately sensitive species include:

• Damselflies
• Dragonflies (see image)
• Beetles
• Crustaceans

Species which are tolerant to most conditions include:

• Snails
• Maggotflies
• Mosquito larvae
• Leeches

Most of these species take their oxygen from the air rather than from the water which means that they are more tolerant to poorly oxygenated waters.