What’s Monitored

Looking at microbiotic organisims - rock photo by Darienne Mc Namara


Macroinvertebrates Group 3: sensitive to pollution

Blackfly larvae (Order Diptera) live in all types of stream habitats.  These bowling pin-shaped organisms are found attached to substrate by their back ends.  They eat by filtering organic materials from the water with fans that can be outstretched into the water column from their mouth.

Orb snails (Order Gastropoda) live in a variety of aquatic habitats.  They eat primarily decaying plants or algae growing on rocks.  These snails obtain their oxygen through a lung that takes up about half of the space within the body cavity.  A opening to the lung is found where the mantle (lining inside the shell) and the foot (muscular or fleshy portion of snail upon which it moves) meet. The orb snails also have an additional projection from their foot called a pseudobranch that acts as a gill, offering an additional way for these snails to obtain oxygen. These snails may move to the surface to obtain oxygen for their lung, giving them the ability to live in waters without much dissolved oxygen.

Amphipods, scuds, or side swimmers (Order Amphipoda) are often found in slow-moving waters.  They are scavengers, eating primarily decaying plant and animal materials.  Since such materials would be readily available in organically polluted waters, their eating habits can help explain why amphipod populations can be large in polluted waters.


The non-red Midge Larvae is identical to the Bloodworm Midge Larvae except for the Bloodwood Midge Larvae's red color. Both the Bloodworm Midge and non-red Midge Larvae (Order Diptera) can tolerate fairly low oxygen conditions and feed on a variety of food sources.  Different types are herbivores, carnivores, omnivores, and detritivores.  Most non-red midge larvae live Non-red Midge Larvaewithin the stream for a year or less, and emerge as adults through most of the year (except in the coldest months).  There are two families of midges included in this group; they are the biting midges and the lake flies (which do not feed and therefore which do not bite).

Gilled snails (Order Gastropoda) also live in a variety of aquatic habitats and, like the orb snails, eat primarily decaying plants or algae growing on rocks.   A difference between this snail and the orb snail is that it obtains its oxygen through its gills.  These gills offer a large amount of surface area through which oxygen may be obtained.













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