This is a general session covering topics in Plankton Ecology.
Lead Organizer: Kerri Finlay, University of Regina (kerri.finlay@uregina.ca)
Co-organizers:
Beatrix Beisner, University of Quebec at Montreal (beisner.beatrix@uqam.ca)
Angela Strecker, Western Washington University (angela.strecker@wwu.edu)
Presentations
04:00 PM
INTERACTIVE EFFECTS OF TEMPERATURE, NITROGEN FORM, AND N:P STOICHIOMETRY ON THE ELEMENTAL COMPOSITION AND ECO-PHYSIOLOGY OF MICROCYSTIS (7777)
Primary Presenter: Nicole Wagner, Oakland University (nicolegouldingwagner@gmail.com)
Cyanobacteria blooms are increasing in frequency, intensity, and duration globally. Major drivers of cyanobacterial bloom formation include the concentration of nitrogen (N) and phosphorus (P), the N:P stoichiometry, temperature, water column stability, and light. Although the drivers of bloom formation are known, predicting bloom formation, size, and cyanotoxin potential remains elusive. One potential research area that has received little attention is how the elemental composition changes beyond carbon, N, and P, particularly with different N forms and across temperature gradients that may provide insights into bloom formation and expansion. Here, we examined how temperature, nitrogen form, and supply N:P affect the ionome (i.e., elemental composition beyond carbon, N, and P) and eco-physiological traits of Microcystis aeruginosa (LE3). We grew quadruplicates consisting of nitrate or urea as the N-form, at a N:P of 2, 16, 30, and 50, and across a four-temperature gradient ranging from 20 to 32 degrees Celsius and measured the volume corrected, cell quotas, and biovolume of the ionome, and chlorophyll a. We found numerous two-way and three-way interactions among the N:P supply, N-form, and temperature. The ionomic composition was affected by N:P supply, N-form, and temperature. Overall, our results highlight the interconnectedness of the ionomic composition within and among N:P supply and N-form and, when incorporated into a predictive framework, may be better at predicting bloom size and toxin potential.
04:15 PM
ECOLOGY AND TOXICITY OF CYANOBACTERIA HARMFUL ALGAL BLOOMS IN MINNESOTA LAKES (8043)
Primary Presenter: Leah Schleppenbach, Natural Resources Research Institute (egan0133@d.umn.edu)
Though cyanobacteria are a natural component of phytoplankton communities, increased monitoring continues to convey the importance of understanding physical, chemical, and biological drivers of toxigenic genera. Cyanobacteria harmful algal blooms (cHABs) continue to cause concerns related to human and ecological health despite mitigation efforts. To better understand cHAB ecology and toxicity, we sampled six Minnesota lakes, part of the MN Sentinel Lakes Program, with varying latitudes, land uses, mixing types, and trophic states to determine lake-specific drivers of cyanobacteria phenology. A multidisciplinary approach was taken by integrating traditional microscopy techniques, metagenomic analyses, and nutrient quantification (including nitrogen fixation rates) to determine genera abundance and toxin production capabilities. Sampling surveys occurred from May through October 2020 and 2021. Cyanobacteria genera were ubiquitous among sample lakes, including northern, oligotrophic systems; and regular, nuisance blooms occurred in a southern, eutrophic lake, Peltier. Lakes showed divergent nutrient deficiency statuses (nitrogen vs phosphorus limited or balanced growth), variability in nitrogen fixation rates and microcystin concentrations, and strain-specific toxin production capabilities. We will present a comprehensive overview of the project’s findings and the implications of understanding the importance of cHAB community composition and strain-specific adaptations on toxin production capabilities across varying lake systems.
04:30 PM
ASSESSING BLOOM CONDITIONS ALONG A NORTH-SOUTH TRANSECT IN WESTERN LAKE ERIE DURING 2021-2023 (7970)
Primary Presenter: Jasmine Mancuso, Cooperative Institute for Great Lakes Research (mancusoj@umich.edu)
Following improvement of the harmful algal bloom impairment in the 1970s, Lake Erie began experiencing re-eutrophication in the 1990s. Western Lake Erie (WLE) is subject to high nutrient inputs from the Maumee River and large, nutrient-poor discharge from the Detroit River. Our study explores how water quality and the phytoplankton community changed along a transect extending from the Detroit River mouth to near the Maumee River mouth. We sampled monthly May-October in 2021-2023 evenly spaced along the transect. In 2021, water quality parameters varied more spatially than monthly, particularly in August-October. During 2022, there was spatial and monthly variation, but water further along the transect was more variable temporally. In the later months of both years, chlorophyll, particulate organic carbon and nitrogen, total phosphorus, and suspended solids increased and ammonia decreased along the transect. In situ instrument-collected data revealed an increase in temperature and specific conductivity and more rapidly diminishing PAR with depth along the transect. FluoroProbe data revealed a continued presence of diatoms throughout 2021 with relatively low cyanobacteria concentrations in August-October, while 2022 saw a more typical succession of algal composition for WLE. These data echo differences between the two bloom years, which was more widespread but less concentrated in 2021 than 2022, possibly explained by precipitation patterns. Dynamics associated with the 2023 bloom will also be discussed to help elucidate spatial-temporal patterns of bloom conditions in WLE.
04:45 PM
Assessing the use of critical flow velocity thresholds for preventing persistent thermal stratification and suppressing cyanobacterial blooms (8207)
Primary Presenter: Donald Davis, University of Technology, Sydney (donald.c.davis@student.uts.edu.au)
Toxic cyanobacterial harmful algal blooms (cHABs) are a major worldwide issue in freshwater environments, exacerbated by climate change with rising water temperatures and prolonged and intensified periods of thermal stratification. The Barwon-Darling River in Australia, a dryland river with unpredictable rainfall and highly variable flow regime, often experiences persistent thermal stratification when hotter periods coincide with low discharge, commonly resulting in cHABs. Here we assess a previously proposed management strategy that involves maintaining flows above a critical velocity threshold (0.03-0.05 m/s) to prevent or disrupt stratification and cHABs with a 20-year analysis of Dolichospermum cell counts and river discharge from 6 weir pools on the Barwon-Darling River. Acoustic doppler current profiling was used to find the relationship between discharge and velocity at each site. A negative relationship between flow and cell counts was found and quantile regression estimates show Dolichospermum blooms >15,000 cells/ml can likely be suppressed when a flow velocity of 0.052 m/s (96th quantile, 95% CI: 0.034, 0.104) is maintained. The data also show that blooms frequently occurred below this threshold. Water column temperature measurements between 2020 and 2023 showed that persistent stratification (>1 degree for 7 days) was absent at velocities exceeding 0.05 m/s with a maximum antecedent flow of 0.05 m/s in the prior 7 days. These findings support the use of river flow thresholds for cHAB management and should be applicable to other rivers with similar climates.
05:00 PM
High variability in community structure and activity among individual colonies of Trichodesmium sp. (8219)
Primary Presenter: Mina Bizic, Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) (mina.bizic@igb-berlin.de)
Trichodesmium spp. are globally important marine bloom-forming, nitrogen-fixing, filamentous cyanobacteria. Trichodesmium often forms colonies of several hundred filaments that are colonized by bacteria from the surrounding water. Studies of Trichodesmium blooms often apply classical and molecular tools on bulk water samples with high concentrations of colonies. Following recent studies by us and others that revealed variability in communities colonizing particulate organic matter in aquatic systems, we investigated the heterogeneity in community composition and transcriptional activity of 70 Trichodesmium colonies collected during an autumn bloom in the Gulf of Eilat (Aqaba), Red Sea, Israel. Using combined single-colony metagenomics and metatranscriptomics, we could show that colonies consist of three main strains of Trichodesmium closely related to Trichodesmium thiebautii with T. erythraeum occasionally present as well. The ratio between the strains varied between the different colonies. The associated microbial community varied, with over 70 % dissimilarity between colonies and no specific pattern. Network analysis revealed that aside from a core community of cyanobacteria, almost no other Bacteria, Archaea, and eukaryotic microorganisms, were part of a stable core community. The activity of Trichodesmium in individual colonies was assessed by the change in reads mapped to annotated genes when normalized to the housekeeping gene rpoB considering that gene copy number per genome remains fixed and variability is mostly driven by changes in expression. While housekeeping genes showed little variability in expression, functional genes involved in nitrogen fixation, phosphorus uptake, iron uptake, as well as photosynthesis, were variable between colonies. These results match data from different physiological assays conducted on individual colonies, revealing that despite thriving in the same water mass, different colonies experience a diverse microenvironment. Their localized response to this variability cannot be deconvoluted from bulk analyses, highlighting the need to complement bulk studies with the analysis of individual colonies. Furthermore, comparing the expression of over 900 genes, revealed the three strains exhibit distinct profiles, suggesting they may occupy slightly different niches, and thus, rather than competing, contribute to the overall successful survival of the species under varying environmental conditions.
05:15 PM
Long-term study of phytoplankton dynamics in a supply reservoir reveals signs of trophic state shift linked to hydrodynamic changes associated with flow management and extreme events. (8206)
Primary Presenter: Huy Luong, University of Technology Sydney (Huy.A.Luong@student.uts.edu.au)
Over a decade of monitoring data (2009-2022) from Prospect Reservoir, a critical water supply for Sydney, was analysed to identify how hydrodynamics, influenced by flow management and inflow quality, impacts water quality and phytoplankton. Phytoplankton biovolume increased after a prolonged drawdown and subsequent refill event, mainly driven by dinoflagellates, and corresponded to increases in TP and water temperature. Following severe bushfires in 2019/2020 and subsequent heavy flooding, increased nutrient loading from connected reservoirs shifted phytoplankton functional group communities towards meso-eutrophic groups. This transition correlated with elevated nutrient levels and chlorophyll-a (Chl-a), and reduced Secchi depth and dissolved oxygen, providing evidence of eutrophication. Q index indicated good water quality post-bushfire, contrasting with a eutrophic status assessment using Chl-a. Our findings highlight the importance of analysing long-term datasets encompassing varied hydroclimatological conditions for a deeper understanding of reservoir behaviour. A comprehensive approach to water quality assessment is recommended, combining functional group classification, Q index and Chl-a measurements for effective reservoir health assessment. This research provides novel insights into the effects of disturbances such as bushfires, on water quality and phytoplankton dynamics in an underrepresented geographic region, offering valuable knowledge for managing water resources amidst growing climate variability.
CS26A - Plankton Ecology
Description
Time: 4:00 PM
Date: 4/6/2024
Room: Meeting Room MN