what are aquatic macroinvertebrates?
Aquatic macroinvertebrates are visible organisms with no backbone that spend all or most of their life in rivers, streams, lakes, and ponds (AKA water bugs!). They are a necessary part of a healthy aquatic ecosystem serving as the primary processors of organic material while also being prey to larger organisms, such as fish and other predatory macroinvertebrates.
Above: Caddisflies in cases attached to a river rock!
Certain types of macroinvertebrates require different habitat conditions. Rivers and streams, with faster flowing waters, usually have a colder temperatures and higher levels of dissolved oxygen which are ideal for stoneflies, mayflies and caddisflies. Lakes and ponds, with slower or more stagnant waters, usually have warmer temperatures and lower levels of dissolved oxygen which are tolerated by leeches, mosquitoes and midges.
Macroinvertebrates also require adequate shelter and food sources that can be provided in a diverse environment of submerged logs and woody debris, rocks and sandy substrate, riparian vegetation, decomposing leaves and other organic material that falls into the water.
the 5 c's of a healthy river
Most aquatic invertebrates will live the majority of their life time in the water and only emerge as terrestrial adults. There are two types of life cycles that an invertebrate will go through as it grows:
Complete Metamorphosis: 4 phases
Incomplete Metamorphosis: 3 phases
Anterior: Refers to the head end of the body/structure.
Lateral: Refers to the side of the body/structure.
Posterior: Refers to the tail end of the body/structure.
Dorsal: Refers to the upper or top part of the body/structure.
Ventral: Refers to the lower or bottom part of the body/structure.
Head: Usually capsule-like and contains the feeding apparatus of the organism.
Thorax: Composed three segments and the location of the legs or leg-like appendages.
Abdomen: Composed of several segments (often 8-11).
Antennae: A pair of slender movable sensory organs located on the head.
Mandibles: A pair of appendages near the mouth used to grab, cut and chomp.
Tarsal claws: Claws located at the end of the leg.
Cerci: Appendages located on posterior end of some insects.
Bioindicators are organisms that effectively indicate the condition of the environment because of their limited tolerance to environmental variability.
Factors governing aquatic insect distribution:
Sediment and substrate type
Presence of pollutants such as pesticides, acidic materials and heavy metals
We can use the presence of certain macroinvertebrates (stoneflies, mayflies and caddisflies) to help determine the likely health status of a river!
Learn more about macroinvertebrate orders - key characteristics for identification and stress tolerance levels!