Benthic Macroinvertebrates Flashcards
Macroinvertebrate
Animals without backbones that are visible to the naked eye without magnification.
(Zale et al, 2012)
Why study benthic macroinvertebrates?
They are an important link in food webs and they provide information on water quality.
For example, the Hilsenhoff Biotic Index (HBI) aka the Family Biotic Index looks at the abundances of different species to create an index value which is based on each species’ tolerance to pollution. The index then identifies water quality on a scale from 0 to 10 with 0 being excellent and 10 being awful.
(ENSC 3106 Notes)
They are also critical to nutrient cycling in streams, breaking down leaves and other materials into small sizes that other organisms can use.
Benthic Macroinvertebrate
Benthic (meaning “bottom-dwelling”) macroinvertebrates are small aquatic animals without backbones and the aquatic larval stages of insects.
Some examples include dragonfly and stonefly larvae, snails, worms, and beetles.
Often found attached to rocks, vegetation, logs and sticks or burrowed into the bottom sand and sediments.
https://www.epa.gov/national-aquatic-resource-surveys/indicators-benthic-macroinvertebrates
Describe the life history of benthic macroinvertebrates.
Many of the benthic macroinvertebrates I will encounter are aquatic insects. Aquatic insects have complex life cycles and live in the water only during certain stages of development .
Aquatic insects may go through one of two kinds of development or metamorphosis: complete or incomplete metamorphosis.
https://www.in.gov/idem/riverwatch/files/volunteer_monitoring_manual_chap_5.pdf
Complete Metamorphosis
Four stages of development: egg, larva, pupa, and adult.
They lay their eggs in water. Eggs then hatch into larvae that feed and grow in the water. (These larval insects do not resemble the adult insects. Many appear wormlike.)
The fully grown larvae develop into pupae and then into adults.
The fully formed adults of some species emerge from the water and live in the habitat surrounding the stream. Others, continue to live in the stream as adults.
After mating, adults of all aquatic insect species lay eggs in the water, beginning the life-cycle all over again.
https://www.in.gov/idem/riverwatch/files/volunteer_monitoring_manual_chap_5.pdf
Incomplete Metamorphosis
Has three stages of development: eggs, nymphs and adult.
The eggs hatch into nymphs which feed and grow in the water while they develop adult structures and organs.
Nymphs often look similar in body shape to the adults.
The life cycle begins again when adults lay eggs in the water.
https://www.in.gov/idem/riverwatch/files/volunteer_monitoring_manual_chap_5.pdf
How does a reduction in habitat quality impact invertebrates?
It will change community composition.
