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SFS Annual Meeting

Wednesday, June 5, 2024
10:30 - 12:00

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C01 Algae

10:30 - 10:45 | Salon 5/6 | ALGAL NUTRIENT LIMITATION AND SENSITIVITY IN AGRICULTURAL WATERSHEDS OF THE U.S.

6/05/2024  |   10:30 - 10:45   |  Salon 5/6

ALGAL NUTRIENT LIMITATION AND SENSITIVITY IN AGRICULTURAL WATERSHEDS OF THE U.S. Agriculture has increased eutrophication and algal blooms in freshwater systems in much of the United States. To help address this, USDA established the Long-term Agroecosystem Research Network to compile information that will help address future agricultural challenges that will require balancing production and environmental health. From June to October 2023, 11 agricultural sub-watersheds from 9 states within the Mississippi River, Ohio River, Suwannee River, Lake Erie, and Chesapeake Bay drainage basins were sampled for surface water-column algae. Using laboratory nutrient bioassays, algal nutrient limitation and sensitivity was assessed. Nutrient limitation occurred in 95-100% of sub-watersheds in the Mississippi River Basin, Suwannee River Basin, and Lake Erie. Only 50-60% of sub-watersheds were nutrient limited in Chesapeake Bay and the Ohio River Basin, respectively. Algal nutrient sensitivity as concentration-response curve half-maximum effects concentrations (EC50s) indicated wide ranges in intra- and inter-basin sensitivities. Nitrate EC50s ranged from 21-550 µg/L and were frequently (82%) <200 µg/L. Phosphate EC50s ranged from 4-159 µg/L and were frequently (74%) <50 µg/L. Understanding algal nutrient limitation and sensitivity can help provide clearer goals for agricultural watershed conservation strategies as tools to better manage non-point source nutrients in agricultural sub-watersheds.

Richard Lizotte (Primary Presenter/Author), USDA-ARS, Richard.Lizotte@usda.gov;

Claire Baffaut (Co-Presenter/Co-Author), USDA-ARS, claire.baffaut.usda.gov;

Laura Johnson (Co-Presenter/Co-Author), Heidelberg University, ljohnson@heidelberg.edu;

Robert Malone (Co-Presenter/Co-Author), USDA-ARS, rob.malone@usda.gov;

Oliva Pisani (Co-Presenter/Co-Author), USDA-ARS, oliva.pisani@usda.gov;

Peter Smiley, Jr. (Co-Presenter/Co-Author), USDA-ARS, rocky.smiley@usda.gov;

Mark Williams (Co-Presenter/Co-Author), USDA-ARS, mark.williams2@ars.usda.gov;

Cathleen Hapeman (Co-Presenter/Co-Author), USDA-ARS, cathleen.hapeman.usda.gov;

Greg McCarty (Co-Presenter/Co-Author), USDA-ARS, Greg.McCarty.usda.gov;

Anthony Buda (Co-Presenter/Co-Author), USDA-ARS, anthony.buda@usda.gov;

10:45 - 11:00 | Salon 5/6 | COMBINING ASSESSMENTS OF PERIPHYTON STRUCTURE AND FUNCTION TO DETECT SUBTLE ANTHROPOGENIC IMPACTS TO HEADWATER STREAMS IN THE UPPER DELAWARE BASIN, USA

6/05/2024  |   10:45 - 11:00   |  Salon 5/6

Combining assessments of periphyton structure and function to detect subtle anthropogenic impacts to headwater streams in the upper Delaware Basin, USA Headwater streams are vital to the health and resiliency of entire watersheds; thus, understanding how human activities impair the structure and function of these vulnerable ecosystems is essential. We combined structural and functional measures of stream periphyton in 46 headwater streams throughout the upper Delaware River Basin, USA, to determine which measures were most helpful in detecting subtle anthropogenic impacts. Stepwise Redundancy analyses run independently with structural and functional variables identified local photosynthetically active radiation and total phosphorus as the most influential environmental variables. Algal biomass and productivity under different light and nutrient concentrations likely drove many subsequent patterns in periphyton structure and function. Generalized additive models indicated possible thresholds with increasing light for algal biomass, bacterial biomass, gross primary productivity, and patterns in carbon-acquiring enzymes. These thresholds were likely driven by algae shifting from light to phosphorus limitation and bacteria shifting from terrestrially derived recalcitrant dissolved organic substrates to more labile algal-derived substrates. Overall, structural and functional measures of stream periphyton were complementary for understanding the mechanisms underlying the impacts of specific stressors and together gave a more complete picture of ecological conditions within each stream and how human activities have influenced the health of these systems.

Steven Rier (Primary Presenter/Author), Commonwealth University of Pennsylvania, srier@commonwealthu.edu;

Braeden Gonzales (Co-Presenter/Co-Author), Commonwealth University of Pennsylvania , braedengonzales98@gmail.com;

Mariena Hurley (Co-Presenter/Co-Author), Academy of Natural Sciences of Drexel University, mkh96@drexel.edu;

Tanya Dapkey (Co-Presenter/Co-Author), Academy of Natural Sciences, thd45@drexel.edu;

Hanna Martin (Co-Presenter/Co-Author), Commonwealth University of Pennsylvania , hem94662@huskies.bloomu.edu;

Stefanie Kroll (Co-Presenter/Co-Author), Riverways Collaboration of CultureTrust Greater Philadelphia, stef.a.kroll@gmail.com;

11:00 - 11:15 | Salon 5/6 | SEASONALLY MEDIATED CHANGES IN AQUATIC PRIMARY PRODUCTION IN A HIGHLY FLOW-REGULATED REACH OF THE COLORADO RIVER BELOW GLEN CANYON DAM

6/05/2024  |   11:00 - 11:15   |  Salon 5/6

SEASONALLY MEDIATED CHANGES IN AQUATIC PRIMARY PRODUCTION IN A HIGHLY FLOW-REGULATED REACH OF THE COLORADO RIVER BELOW GLEN CANYON DAM Since the early 1990’s there has been a dramatic shift in flow regime and a corresponding shift in macrophytes and substrata in the Colorado River downstream from Glen Canyon Dam following stabilization of water releases. Reduced daily flows have coincided with an increase in macrophyte species diversity and a corresponding decrease in the previously dominant epiphyte host, Cladophora glomerata. Epiphytic algae remain the major food base, although it was not known how these major physical changes have altered algal production and nutritional content for grazing invertebrates. We deployed colonization bricks monthly at three paired north- and south-exposure sites along a 21 km transect from Lees Ferry to Glen Canyon Dam in April 2021 - January 2022. We assessed effects of reduced flow variation and light availability on epiphytic algal productivity and nutrient stoichiometry. We recorded strong seasonal shifts in production; chlorophyll-a was higher in spring than summer, peaking in May along with near Redfield C:P content (120:1), followed by a 12-fold production decrease in June and a sharp decline in P content (C:P = 681:1). Low production and algal phosphorus continued throughout summer, fall, and winter. Locations with south-facing exposures exhibited higher chlorophyll-a levels in late summer (south: 678.2 ug/m2 > north: 183.8 ug/m2), while north-facing exposures had greater chlorophyll-a production in early spring (north: 2610.9 ug/m2 > south: 1218.1 ug/m2). Our data suggest a complex interaction between discharge, light availability, and season on aquatic primary production and nutrient stoichiometry at the bottom of deep, shaded canyon.

Madelaine Wrey (Primary Presenter/Author), Fordham University , mwrey@fordham.edu;

John Wehr (Co-Presenter/Co-Author), Louis Calder Center - Fordham University, wehr@fordham.edu;

Lawrence Stevens (Co-Presenter/Co-Author), Spring Stewardship Institute, larry@springstewardship.org;

11:15 - 11:30 | Salon 5/6 | SUCCESSIONAL CHANGES IN COMPOSITION, RELATIVE ABUNDANCE, AND RELATIVE GROWTH RATES OF PROKARYOTIC FUNCTIONAL GROUPS IN A RIVERINE ALGAL MICROBIOME

6/05/2024  |   11:15 - 11:30   |  Salon 5/6

Successional changes in composition, relative abundance, and relative growth rates of prokaryotic functional groups in a riverine algal microbiome The green alga Cladophora glomerata is home to microorganisms that perform important element cycling functions for aquatic ecosystems. Cladophora and its epiphytes dominate summer biomass in the Eel River. With summer baseflow recession, Cladophora changes from green in the early summer, to yellow and then red as epiphyte loads increase and taxonomic composition of the assemblage shifts. Although the community has been characterized in some sites we know little about the prokaryotic organisms, and nothing about their process rates. We used quantitative stable isotope probing (qSIP) incubations during three Cladophora successional stages to measure both changes in abundance and in growth rates of bacteria and archaea. We matched 16s rRNA amplicon sequences to metabolic functional groups using the Silva and KEGG databases. At all stages we identified organisms that participate in important redox reactions. From green to red, bacteria that perform both oxidation and reduction reactions of Fe, S, and N increased in relative abundance, and tended to have higher than average growth rates. In general, relative abundances and growth rates were decoupled, so low abundance species and functional groups may have disproportionate effects on ecosystem processes. For instance, Fe oxidizer relative abundance increased between stages while their relative growth rates decreased, meaning that relative abundance alone would be a poor indicator for this process. If we are to use ‘omics as an insight into microbial contributions to ecosystem activity, we need not only relative abundance, but also growth rates to fully understand the importance of key taxa.

Raina Fitzpatrick (Primary Presenter/Author), Northern Arizona University, rmf273@nau.edu;

Jane Marks (Co-Presenter/Co-Author), Northern Arizona University, jane.marks@nau.edu;

Bruce Hungate (Co-Presenter/Co-Author), Northern Arizona University, bruce.hungate@nau.edu;

Mary Power (Co-Presenter/Co-Author), University of California, Berkeley, mepower@berkeley.edu;

Ty Samo (Co-Presenter/Co-Author), Lawrence Livermore National Lab, samo1@llnl.gov;

Michaela Hayer (Co-Presenter/Co-Author), Northern Arizona University, michaela.hayer@nau.edu;

Peter Weber (Co-Presenter/Co-Author), Lawrence Livermore National Lab, weber21@llnl.gov;

Megan Foley (Co-Presenter/Co-Author), Northern Arizona University, mmf289@nau.edu;

11:30 - 11:45 | Salon 5/6 | POTENTIAL LIVE FEEDS FOR LARVAL FISH CULTURE IN ETHIOPIA

6/05/2024  |   11:30 - 11:45   |  Salon 5/6

POTENTIAL LIVE FEEDS FOR LARVAL FISH CULTURE IN ETHIOPIA The artificial propagation of commercially important fish species in Ethiopia is constrained by high mortality rate at the early stage of larval rearing and a subsequent poor growth performance during later stages. This is mainly due to absence of live feeds suited to the requirements of the larvae of the species. Although not organized, several studies have indicated that microalgae, copepods, cladocerans and rotifers are the dominant inhabitants in several water bodies that are the precursors in the larviculture of commercially important finfishes in the world. However, apart from studying the abundance and diversity of these important planktonic organisms, efforts made to culture any of them for use in the larviculture of commercially important fish species in Ethiopia is minimal. This may be due to the lack of comprehensive and organized information on the distribution and abundance of these important species in the context of their potential in aquaculture of live feeds in Ethiopia. The objective of this review is therefore to compile the available information on the abundance and distribution of the major potential live feed organisms in the Ethiopian water bodies with a special emphasis on freshwater live feed organisms currently used in larviculture of commercially important freshwater finfishes. In line with this, four potential live feeds (i.e. microalgae, rotifers, copepods and cladocerans) were included in the review. It is hoped that the review will provide baseline information for future research in the culture of economically important larval live feeds.

Solomon Melaku (Primary Presenter/Author), Addis Ababa University, solomon.melaku@aau.edu.et;

Abebe Getahun (Co-Presenter/Co-Author), Addis Ababa University, abebe.getahun@aau.edu.et;

Seyoum Mengistou (Co-Presenter/Co-Author), Addis Ababa University, seyoumeng@gmail.com;

Akewake Geremew (Co-Presenter/Co-Author), Addis Ababa University, Akewake.geremew@aau.edu.et;

Amha Belay (Co-Presenter/Co-Author), Algae4all.com, abelay@algae4all.com;