Flashcards in Monitoring Ecosystems Deck (14)
what are macro-invertebrates
Macro-invertebrates are insects and other animals without a backbone that can be seen without magnification. They live at the bottom of most water bodies. Although some of these animals spend their entire lives in water, many of them grow to be terrestrial insects that are familiar to most people.
why scientists use macro-invertebrates
Scientists use macro inverts to learn more about a system, they are used as indicators of water condition because:
- easy to collect
- many, called sensitive, cannot survive changes in stream conditions such as environmental stressors. Other organisms (tolerant) can survive with changes in conditions.
- many stay in a small area most of their lives.
- diversity of macros in a sample informs whether ecosystem can support populations of amphibians, birds, and other wildlife species.
examples of environmental stressors
introduction of pollution, high levels of sediments, increased water temperatures or low dissolved oxygen
macros = excellent for
determining the health of a wetland. Lots of sensitive organisms would imply there is little to no pollution present, where as a high population of tolerant and few sensitive would indicate pollution.
sweep nets through water in vigorous jabbing motion, this will dislodge any macro-invertebrates from the vegetation, and they will be collected in the net.
1- contents are placed into tray containing water (from the environment) with screen on top. Macro move through the screen to get away from the light, the screen catches any other substances (leaf litter) that may be have been collected.
2- Macro-invertebrates are then collected using tweezers or a pipette, specimens are then placed into individual jars containing water from their habitat.
3- the individual species are recorded, the number is counted and recorded.
Organisms will be collected for 30mins or until 150 organisms are collected, these steps are repeated.
used in small flowing stream. Baskets approached down stream. Basket filled with rocks is left at base for several days where it grows or debris, which attracts macros.
rock baskets method
- while preparing to pick up the basket, aquatic net should be placed (without disturbing basket) downstream. This is so while basket is being carefully picked up into net any escaping organisms/debris will be collected.
- content of basket and net washings are emptied and cleaned into sieve basket, rocks are hand washed and inspected, then returned to basket. then follows general method.
Rock filled cone samplers
used in deep, non wadeable rivers having sufficient flow to have an eroded mineral based bottom. Cone shaped wire filled with substrate material (rocks) and closed by means of an inverted weighted funnel.
they are marked in the water with buoys, the cone and funnel have to be collected quickly and smoothly from bottom and emptied directly into sieve bucket or tub. Same as others for rest.
sampling known volumes of water
samples of water of a known volume are taken and the number of macros in that sample are counted and observed. this is repeated multiple times to obtain an average and can be used to estimate the population size and diversity of the entire water body.