Lakes in the southcentral USA are warm-monomictic, many of which have become eutrophic, raising concerns about harmful algal blooms (HABs). HABs associated with prymnesiophytes and cyanobacteria have been recurrently problematic and the frequency, magnitude and duration of HABs are likely to increase with climate change. Here, we seek to better understand the drivers of inland HABs in the southcentral USA, with a particular focus on nitrogen loading. Recent advances in understanding have shown a selection for prymnesiophytes and some toxic cyanobacteria at high N:P ratios. We are sampling twenty reservoirs and their tributaries, spanning a pronounced east-west annual precipitation gradient across Texas. Samplings occur in the spring and summer of each year, and measured parameters include total microcystins, microbial community composition (using metagenomics), microbial functions (using metatranscriptomics), and several water quality parameters. Inflows and nutrient loadings are being determined using the Hydrologic and Water Quality System (HAWQS) calibrated with USGS gauge data and tributary nutrient samples. Principal component analysis reveal a positive relationship between NOx, total microcystins and cyanobacteria taxa that are known microcystin producers.  Our finding also suggest a disruption of denitrification during a bloom, providing a possible explanation of high NOx during the bloom.  Our work also shows that microcystins can be widespread in these lakes and their tributaries.

Primary Presenter: Daniel Roelke, Texas A&M University Galveston (droelke@tamu.edu)

Authors:

Daniel Roelke, Texas A&M University Galveston  (droelke@tamu.edu)

Crista Kieley, Texas A&M University Galveston  ()

Hagen Klobusnik, Texas A&M University Galveston  ()

Royoung Park, Texas A&M University Galveston  ()

Kate Campbell, Texas A&M University Galveston  ()

Jordan Walker, Texas A&M University Galveston  ()

Sierra Cagle, Texas A&M University Galveston  ()

Kevin Stroski, Baylor University  ()

Marissa Kneer, US Army Corps of Engineers  ()

Jacob Berkowitz, US Army Corps of Engineers  ()

Bryan Brooks, Baylor University  ()

Jessica Labonte, Texas A&M University Galveston  ()