Metagenomic and Isotopic Characterization of Epilimnetic and DCL Phytoplankton in Lake Superior

Session: 32. - Long-Term Monitoring: Achievements, Challenges, and Solutions

Andrew Bramburger, Natural Resources Research Institute, University of Minnesota Duluth, [email protected]
Cody Sheik, Large Lakes Observatory, University of Minnesota Duluth, [email protected]
Euan Reavie, University of Minnesota Duluth, [email protected]

Abstract

Ongoing monitoring of the phytoplankton communities of the Laurentian Great Lakes have shown marked compositional differences among the assemblages of the spring isothermal water column, the summer epilimnion (EPI), and the summer deep chlorophyll layer (DCL). However, these microscopy-based characterizations do not address the true biodiversity of the primary producer community, nor do they provide insight into the contributions of the EPI and DCL phytoplankton to higher trophic levels. During the 2016 CSMI intensive sampling year on Lake Superior, we used high-throughput genomic techniques and stable isotope (?¹³C and ? ¹⁵N) analysis to more comprehensively describe patterns of biodiversity and connectedness in the Lake Superior plankton community. Preliminary results show significant metagenomic dissimilarities among EPI and DCL assemblages, as well as between nearshore and pelagic stations and between particle-associated and free living entities (i.e. 3.0 and 0.22 µm size fractions. Stable carbon signatures exhibited dissimilarities that were consistent with those indicated by metagenomics, and reflect subtle differences in carbon isotope fractionation between eukaryotic (3.0 µm fraction) and prokaryotic (0.22 µm  fraction) algae. These results generally bolster previous findings from taxonomic surveys (2001-2015), and provide fodder for further biodiversity and trophic transfer studies.

1. Keyword
biodiversity

2. Keyword
microbiological studies

3. Keyword
phytoplankton

4. Additional Keyword
metagenomics

5. Additional Keyword
stable isotopes