Littoral benthic macroinvertebrates in Sierra Nevada lakes and reservoirs: Patterns of biodiversity, habitat relationships and indications of condition

Background/Question/Methods Benthic macroinvertebrate assemblages have proven useful in their ability to indicate stream condition and it is suggested they have strong potential as indicators of lake condition. As lentic systems are recognized as sentinels of global climate change, it becomes imperative to understand and monitor the littoral invertebrate contribution to ecosystem dynamics, especially those of high-elevation, oligotrophic montane lakes and reservoirs. To begin to address these needs, assessments of littoral benthic macroinvertebrates were conducted in lakes and reservoirs of the central Sierra Nevada ecoregion. Semi-quantitative D-net sampling was habitat-stratified focusing on gravel and cobble substrates. Assemblage data were analyzed with measures of ecological condition and human activity across scales (mesohabitat, riparian, lake, and catchment). Results/Conclusions Preliminary analysis reveals significant differences between benthic macroinvertebrate assemblages in lakes and reservoirs. Non-metric multidimensional scaling indicates correlations between benthic macroinvertebrate assemblages and a priori classification of human activity and, in this case, opposing gradients of longitude and in-lake recreational activity. Patterns in variation of benthic macroinvertebrate assemblages were found to correlate strongest with the broad-scale morphological classification of lake type. Based on the lake's geologic origin, lake type could serve as an umbrella measure for a suite of finer-scaled ecological conditions and human activities when prioritizing lakes for limited biomonitoring resources. Results from subsequent sampling focused on intralake habitat and diversity thresholds will be also presented along with suggestions for biomonitoring methodology of high-elevation lakes.