Invertebrates are the planet's biggest source of biodiversity and can be found on every level of the food chain and in every ecosystem on the planet. They perform vital roles in their environments and help regulate important biological processes. Invertebrates are an immense food supply to other invertebrates as well as vertebrates; acting as the primary food source for amphibians, birds, fish, mammals and reptiles. Plants depend on insects to help cross-pollinate and produce viable fruits and seeds.

Benthic invertebrates are commonly used in water quality monitoring as they are easy and inexpensive to collect and are relatively long-lived in the system (1+ year). Certain invertebrates are sensitive to environmental changes because they cannot easily escape degrading conditions. In general, the absence of invertebrate species that are sensitive to degrading conditions may indicate poor water quality whereas their presence would indicate good water quality.  Species that are more tolerant of the water conditions often have less competition when water quality is poor, allowing them to reproduce in higher densities.

During the waterfowl breeding season, invertebrates play a critical role in the diet of female ducks. In winter, waterfowl hen’s diet consists of seeds and plant material but slowly shifts to a spring diet of mainly invertebrates. Invertebrate preference varies by waterfowl species, but in general snails, crustaceans, and insects are important invertebrate groups for reproducing ducks. During the laying period, many species of hens will rely on snail shells for calcium for egg production. Early-nesting species such as northern pintail and mallard consume early-emerging midge larvae in addition to earthworms, which are often the most available food in ephemeral wetlands. The diving ducks consume free swimming amphipods or larger insects such as caddis fly and dragonfly larvae that tend to occur in deeper water. The northern shoveler and gadwall are dependent on crustaceans that swim in the water and forage on algae and fine organic matter. At Humboldt Bay National Wildlife Refuge we use the presence of these invertebrates to determine the effectiveness of wetland and water management strategies.