Seamounts modify water flow and create nutrient-enriched upwelling zones that support increased productivity and biodiversity. However, similar systems are largely unstudied in lakes. We hypothesized that steep reefs in deep lakes (“lakemounts”) act as seamounts. In a preliminary study, we monitored water temperature and compared fish and benthic invertebrate diversity nearshore (NS) and around a lakemount (LM) in Lake Champlain, US. In a 20-day period, the thermocline oscillated around 15 m depth. We observed two seiche events that upwelled cold water, both with 4 days duration. Temperature was positively related to NE winds (t=1.95, p=0.05) and negatively related to SSW winds (t=-5.14, p<0.001), indicating formation of a wind-driven seiche. Taxonomic richness was higher at the NS than LM site (12 vs 11 fish species, and 25 vs 20 benthic taxa, respectively). Shannon-Weiner diversity (H) and Evenness (evar) indices showed that NS benthos had higher diversity and evenness compared to the LM benthic community (H=2.2 vs 1.7; evar=0.7 vs 0.6; NS vs LM, respectively), while the fish diversity and evenness were higher in the LM (H=1.5 vs 1.8; evar 0.6 vs 0.7; NS vs LM, respectively). Salmonids were present only at the LM and insects were exclusively in the NS, while other taxonomic groups were similar between the habitats. Zooplankton samples remain to be processed. Our early results suggest the diversity of benthic invertebrates and fishes were comparable between lakemount and nearshore habitats, suggesting lakemounts may act as a biological hotspot in the offshore habitat.

Primary Presenter: Bianca Possamai, University of Vermont (biancapossamai@hotmail.com)

Authors:

Bianca Possamai, University of Vermont  (bianca.possamai@uvm.edu)

J Ellen Marsden, University of Vermont  (ellen.marsden@uvm.edu)

Jason Stockwell, University of Vermont  (jason.stockwell@uvm.edu)