THE XERCES SOCIETY FOR INVERTEBRATE CONSERVATION

Aquatic Invertebrates in Pacific Northwest Freshwater Wetlands
An Identification Guide and Educational Resource

The type of analysis you can do will depend on the type of study you conducted. You may be interested in investigating how the macroinvertebrate community in a single wetland changes over a period of a few years, discovering changes in community composition following restoration efforts, or comparing invertebrate communities in heavily impacted wetlands to invertebrate communities in more pristine wetlands in your watershed.

To draw conclusions about invertebrate biological integrity, you will need to have a good understanding of the invertebrate community that exists in your wetland, as well as an understanding of what the invertebrate community should be in a similar reference wetland. The Pacific Northwest currently does not have a comprehensive list of the taxa that exist in reference wetlands, nor do we have a comprehensive list of the macroinvertebrates to be expected in highly degraded wetlands. However, The Xerces Society and others are working towards gaining a better understanding of how invertebrates respond to human impairment of wetlands. We hope to find consistent invertebrate indicators, or metrics, that vary predictably between reference and highly impaired wetlands, and use those metrics develop a wetland invertebrate Index of Biological Integrity. For example, studies in other parts of the country have found that the percent Odonata (dragonflies and damselflies) of the total sample is a reliable indicator of human disturbance in wetlands..

Without these tools in the Pacific Northwest, one can still examine measures such as macroinvertebrate diversity, richness and evenness in a wetland, and compare these measures across other wetlands in your watershed.

It will be important to understand whether individual taxa from your wetland are known to be tolerant or sensitive to pollution or disturbance. Much research has been done on tolerance levels of stream invertebrates; unfortunately this information is not always directly applicable to wetlands. For example, some stream invertebrates are considered tolerant because they can withstand very low levels of dissolved oxygen. But under normal conditions, wetlands can have very low levels of dissolved oxygen at times, so even the most pristine metland may contain some taxa that are considered very tolerant in streams.

There is limited information available about the tolerance levels of wetland invertebrates, including an EPA report (outside link) that summarizes some studies done on how macroinvertebrates respond to a variety of wetland stressors. These stressors include: excess Nitrogen or Phosphorus from fertilizer runoff, chemical contaminants from heavy metals and pesticides, thermal alteration (caused by removal of vegetation or the tree canopy above the wetland), or input of warmer water, habitat fragmentation, sedimentation, salinity, turbidity, vegetation removal, and dehydration or inundation. There is also an EPA database, developed by Adamus and Gonyaw, which contains information on a variety of invertebrate responses to wetland stressors. The identify taxa portion of this CD contains some information about the tolerance of various taxa to anthropogenic stressors.