SFS Annual Meeting

6/04/2024  |   13:30 - 13:45   |  Salon 5/6

How have states addressed algal taxonomic issues in their datasets? Diatoms and soft algae have been collected by state monitoring programs across the United States to assess the biological condition of lotic and lentic water bodies. Some of the state programs have long-term records (i.e., decades) of algal taxonomic data. Over time, changes in laboratory contractors and algal systematics have contributed to challenges in maintaining consistent datasets that can be applied to biological assessment questions. The U.S. Environmental Protection Agency provided technical assistance towards examining taxonomic issues and resolving discrepancies within state algal datasets. Improvements in data quality and transparent documentation of how datasets are modified to “harmonize” taxonomy helped restore confidence in using algal data for state assessments. This kind of data modification has been called “post-hoc harmonization,” which differs from harmonization embedded into a research plan from the beginning through upfront resources dedicated to ensuring consistent taxonomic data. Post-hoc harmonization is helpful but results in some loss of data resolution and usually cannot completely remove the variation in algal assemblage composition explained by laboratory or analyst. This presentation will focus on examples of post-hoc harmonization efforts and lessons learned that may help state programs make better use of their existing algal data and inform future collection and management of algal taxonomy to improve monitoring and assessment of biological condition in freshwaters.

Sylvia Lee (Primary Presenter/Author), U.S. Environmental Protection Agency, lee.sylvia@epa.gov;

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6/04/2024  |   13:45 - 14:00   |  Salon 5/6

Using genus-level taxonomy and traits for efficient ecological assessments of diatom condition Difficulty in diatom species identification and nomenclature can lead to major inconsistencies in taxonomic datasets. These inconsistencies may hinder the use of diatoms in large-extent bioassessments such as the U.S. Environmental Protection Agency’s (U.S. EPA) National Aquatic Resource Surveys. We addressed this problem by developing diatom multimetric indices (MMIs) of ecological condition using genus-level taxonomy and trait-based information (e.g., tube-living, motile and nitrogen-fixing diatoms) collected from the 2008-09 U.S. EPA National Rivers and Stream Assessment (NRSA). The MMIs were designed to assess ecological condition for >3,000 rivers and streams across the U.S. Genus-level, trait-based indices have the advantage over traditional species-based indices of using genus-level data which require less work-effort and expertise and therefore are more efficient to analyze. Using genus-level taxonomy also eliminates the persistent taxonomic biases introduced over vast geographic extents because genus-level identifications are less prone to taxonomic errors, thus improving the taxonomic consistency and quality of large datasets involving multiple analysts. The genus-level trait MMIs responded well to increases in multiple stressors; discriminating least-disturbed from most-disturbed sites. This new indicator could allow for the use of diatoms in future NRSA surveys. Similar genus-level MMIs are also being developed for use in the U.S. EPA’s National Wetland Condition Assessment. Our genus-based approach can be effective for large-extent assessments and facilitates including of diatoms into assessment programs that have limited monitoring resources. Disclaimer: The views expressed in this presentation are those of the authors and do not necessarily represent the views or policies of the U.S. EPA.

Luisa Riato (Primary Presenter/Author), US EPA, Office of Research and Development, Pacific Ecological Systems Division, Corvallis, OR, riato.luisa@epa.gov;

Ryan Hill (Co-Presenter/Co-Author), US Environmental Protection Agency, hill.ryan@epa.gov;

Alan Herlihy (Co-Presenter/Co-Author), Department of Fisheries, Wildlife and Conservation Sciences, Oregon State University, Corvallis, OR, alan.herlihy@oregonstate.edu;

David Peck (Co-Presenter/Co-Author), U.S EPA, Office of Research and Development, Pacific Ecological Systems Division, Corvallis, OR, peck.david@epa.gov;

Philip Kaufmann (Co-Presenter/Co-Author), U.S EPA, Office of Research and Development, Pacific Ecological Systems Division, Corvallis, OR, Kaufmann.Phil@epa.gov;

John Stoddard (Co-Presenter/Co-Author), U.S EPA, Office of Research and Development, Pacific Ecological Systems Division, Corvallis, OR, Stoddard.John@epa.gov;

Steven Paulsen (Co-Presenter/Co-Author), U.S EPA, Office of Research and Development, Pacific Ecological Systems Division, Corvallis, OR (retired), sgp.paulsen@gmail.com;

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6/04/2024  |   14:00 - 14:15   |  Salon 5/6

Diatom taxonomy uses in biological assessment In depth taxonomy of monoraphid diatoms, common for southern US and Mediterranean climate freshwater habitats was investigated. Material from current and historic diatom collections from US coastal states (Georgia, Alabama, California) and Cyprus were examined with LM and SEM where possible. Taxa selection (from genera Achnanthidium, Psammothidium, Planothidium, and Cocconeis) was based on documented high abundances (>50%) in targeted samples or routine state or federally funded bioassessment surveys. The concept of each species considered had changed over the years. Authors preferences and research objectives towards the use of sensu lato vs sensu stricto have changed also. In this research, species level identification used for indices development was reviewed and updated. This is a difficult task due to overlaps in morphological features, relatively small size, and the limited number of distinguishable morphological characteristics observed in LM. Practical approaches discussed here concern morphologically overlapping species from the genera. Taxon names, used in final reports, must be provided with authority names to differentiate concepts and approaches as those are used consistently in metrics of community abundance, species richness, evenness and composition. Using these taxonomic revisions/harmonizations ensures understanding of potential improvement of aquatic-habitats with algal bioassessment. Taxa lists also need updating in view of a possible move to molecular metagenomics bioassessment translations. To guide future researchers into placing appropriate species delineations, size ranges are provided and compared with averages within each relevant species.

Kalina Manoylov (Primary Presenter/Author), Georgia College and State University, kalina.manoylov@gcsu.edu;

Rosalina Stancheva (Co-Presenter/Co-Author), George Mason University, rchris13@gmu.edu;

Marco Cantonati (Co-Presenter/Co-Author), BIOME Lab, Department of Biological, Geological and Environmental Sciences—BiGeA, Alma Mater Studiorum, University of Bologna, Via Selmi 3, 40126 Bologna, Italy, marco.cantonati@unibo.it;

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6/04/2024  |   14:15 - 14:30   |  Salon 5/6

Genome skimming reveals cryptic speciation in a cosmopolitan diatom species We can now generate high-throughput omics data from single cells up to entire communities. Nevertheless, the widespread use of genomics for species identification in algae has been limited. Diatoms, a clade of photoautotrophic protists that dominate in aquatic environments worldwide, are particularly species rich and understudied from a genomics perspective yet play key roles in primary production and biogeochemical cycling. Diatom species are traditionally diagnosed and classified based on morphological features of the silica cell wall, where names are assigned to more-or-less morphologically similar phenotypes. However, many species are morphologically identical and too small for accurate identification. Genetic variation can then be a powerful tool to document population differentiation and identify cryptic species. We explored genetic variation within the cosmopolitan diatom Thalassiosira profunda using a genome skimming approach. This small species has a valve diameter of 2-5 µm, making it difficult to identify using light microscopy. We generated data for 9 strains identified as T. profunda based on morphology that were collected from geographically distant waters. Analyzing 64 single-copy gene markers using coalescent methods identified at least 5 species. While the 18S rDNA marker is commonly used as a barcode for high-throughput species identification, we found that 18S was identical and uninformative across T. profunda. Our results demonstrate the use of genome skimming and provide evidence that cryptic diatom species are more widespread than morphology alone would identify.

Wade Roberts (Primary Presenter/Author), University of Arkansas, wade.r.roberts@gmail.com;

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6/04/2024  |   14:30 - 14:45   |  Salon 5/6

1. DNA METABARCODING IS HIGHLY EFFICIENT FOR ASSESSING RESPONSES OF MICROBIAL EUKARYOTIC/BIOFILM ASSEMBLAGES TO MULTIPLE ENVIRONMENTAL STRESSORS High-throughput molecular techniques are fast transforming the field of bioassessment allowing for time-and labor-efficient ways of capturing information about composition of biological communities. As fish, macroinvertebrates and diatoms have been traditionally used for freshwater biomonitoring, the major efforts for developing and standardizing eDNA techniques for bioassessment purposes have also been concentrated on these three groups of organisms. DNA metabarcoding, however, opens practically endless opportunities for tracking responses of multiple taxonomic and functional groups including the meiofauna, fungi, diverse photosynthetic and heterotrophic protists and prokaryotes to environmental change. Using examples from our recent projects aimed at metabarcoding of stream, lake, and pond biofilms, we show that even low-taxonomic resolution molecular markers are powerful tools that can be currently adopted for bioassessment. The wealth of data obtained by metabarcoding is unparalleled and outweighs such shortcomings as the current lack of standardization in methods of DNA extraction, PCR, sequencing and bioinformatics processing and poor taxonomic coverage in reference databases for most microbial eukaryotes. Taxa groups that are difficult to identify morphologically, such as unicellular green algae, peronosporomycetes, naked amoebas, ciliates and fungi show strong connections with different aspects of water and habitat quality. We will discuss the tradeoffs between markers of low- and high-taxonomic resolution and suggest strategies of combining the power of molecular techniques with classic taxonomic expertise in developing bioassessment strategies.

Marina Potapova (Primary Presenter/Author), Academy of Natural Sciences of Drexel University, mp895@drexel.edu;

Laura Aycock (Co-Presenter/Co-Author), Academy of Natural Sciences of Drexel University, lla32@drexel.edu;

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