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Bighorn River Aquatic Macroinvertebrate monitoring: Sampling and Analysis Plan

Sept 15, 2019

Lead Scientist

David Stagliano

study objectives

The objective of this portion of the BHRA Research Initiative is to develop a long-term data set on benthic macroinvertebrate populations and community assemblage structures along the study reach of the Bighorn River. The two principal tasks are to determine what macroinvertebrate data has been collected in the past (Literature Review and Historical Analysis) and to develop a sampling and analysis plan (SAP) that will be used going forward. The data on these biological indicators will help define spatial and temporal trends in aquatic habitat health and the way in which they are influenced by macrophyte beds, algae, aquatic invasive species, sedimentation, water quality, dissolved gases, and regulated flows.


The goal of a macroinvertebrate sampling and analysis 

plan (SAP) is to outline a procedure to collect quantitative baseline data using standardized methods and to interpret this information consistently to establish trends leading to an understanding of the overall health of the Bighorn River. We’ve identified eight Bighorn River sites (four with previous quantitative data) that will give a good representation of the spatial distribution of macroinvertebrate communities from Yellowtail Dam to the Yellowstone River confluence. With the concurrent collection of water quality data, we will be able to better understand causal relationships between the macroinvertebrate and aquatic plant communities and water quality to understand implications for the long-term health of the river.

The goal of the literature review portion is to understand the historical data that has been assembled to better inform the collection of current and future baseline data in the lower Bighorn River area, and to continue assessing this information annually to establish trends that may be causally linked to the overall health of the river. For example, five years of macroinvertebrate data had been collected by MDEQ at the Manuel Lisa FAS (2001-2005). Even in this short time frame, the health of the macroinvertebrate community, as measured by MDEQ’s Multi-metric Index (MMI), appears to have biologically declined substantially from “very healthy” in 2001 and 2002 to “impaired” in 2004 and 2005. 


Among other things, the proposed SAP will document the current status of the macroinvertebrate community at the Manuel Lisa FAS site which has not been sampled in 14 years. Did the macroinvertebrate trends seen in the historical data continue or were they altered by changing environmental conditions? 

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