Makah Water Quality

Macroinvertebrates

    Streams, rivers, wetlands and lakes are home for many small animals called macroinvertebrates. These animals generally include insects, crustaceans, molluscs, arachnids and annelids. The term macroinvertebrate describes those animals that have no backbone and can be seen with the naked eye. Some aquatic macroinvertebrates can be quite large, such as freshwater crayfish, however, most are very small. Invertebrates that are retained on a 0.25mm mesh net are generally termed macroinvertebrates. These animals live in the water for all or part of their lives, so their survival is related to the water quality. They are significant within the foodchain as larger animals such as fish and birds rely on them as a food source. Macroinvertebrates are sensitive to different chemical and physical conditions. If there is a change in the water quality, perhaps because of a pollutant entering the water, or a change in the flow downstream of a dam, then the macroinvertebrate community may also change. Therefore, the richness of macroinvertebrate community composition in a waterbody can be used to provide an estimate of waterbody health. Macroinvertebrate communities vary across the State and different waterbodies often have their own characteristic communities. As many of the waterbodies in Western Australia are not permanent, animals are tolerant to a wide variety of environmental conditions. Most have a phase within their life cycle to escape extreme conditions. Once familiar with the taxa in your local area, you can use them as an additional way of monitoring the waterbody you are studying.

Life cycle

    The most common types of aquatic macroinvertebrates are insects. As insects grow from an egg to an adult they change their body shape or metamorphoses. Insects show both complete and incomplete metamorphosis. Incomplete metamorphosis involves the egg hatching into a nymph. At every moulting the nymph looks more and more like the adult form. Complete metamorphosis involves the egg hatching into a larva, which is very different to the adult. The final larval stage involves the animal developing into a pupa, which is very different from the larva. From this stage the animal then develops into an adult. For most, the aquatic juvenile stage occupies by far the major proportion of the life cycle and is largely a feeding machine, leaving for the adult only a brief reproductive role. Some dragonfly larvae take three years to mature

What do macroinvertebrates eat? 

    Macroinvertebrates are an important part of the aquatic food chain and can be characterised by what the animal feeds on and how it acquires it. The categories are referred to as functional feeding groups and help describe the role each macroinvertebrate plays in an aquatic system.
Shredders feed on organic material, such as leaves and woody material, and help to convert this matter into finer particles. They require vegetation growing along a waterbody, so that plant material falls into the water, and slow flowing water so that the plant material is not swept away. Such animals include amphipods, isopods, freshwater crayfish (marron, gilgies, koonacs) and some caddisfly larvae Collectors/Filter feeders feed on fine organic particles that has been produced by shredders, microorganisms and by physical processes. Such animals include mayfly nymph, mussels, water fleas, some fly larvae and worms. Scrapers graze algae and other organic matter that is attached to rocks and plants. Such animals include snails, limpets and mayfly larvae. Predators feed on live prey and are found where smaller collectors and shredders exist. Such animals include dragonfly and damselfly larvae, adult beetles and beetle larvae, some midge larvae and some stonefly larvae.

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