Preparing aquatic research for an extreme future: call for improved definitions and responsive, multidisciplinary approaches

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Aoki, L. R., Brisbin, M. M., Hounshell, A. G., Kincaid, D. W., Larson, E., Sansom, B. J., Shogren, A. J., Smith, R. S., & Sullivan-Stack, J. Preparing aquatic research for an extreme future: call for improved definitions and responsive, multidisciplinary approaches. Bioscience, 72(6), (2022): 508-520, https://doi.org/10.1093/biosci/biac020.Extreme events have increased in frequency globally, with a simultaneous surge in scientific interest about their ecological responses, particularly in sensitive freshwater, coastal, and marine ecosystems. We synthesized observational studies of extreme events in these aquatic ecosystems, finding that many studies do not use consistent definitions of extreme events. Furthermore, many studies do not capture ecological responses across the full spatial scale of the events. In contrast, sampling often extends across longer temporal scales than the event itself, highlighting the usefulness of long-term monitoring. Many ecological studies of extreme events measure biological responses but exclude chemical and physical responses, underscoring the need for integrative and multidisciplinary approaches. To advance extreme event research, we suggest prioritizing pre- and postevent data collection, including leveraging long-term monitoring; making intersite and cross-scale comparisons; adopting novel empirical and statistical approaches; and developing funding streams to support flexible and responsive data collection

How Low Can You Go?: Widespread Challenges in Measuring Low Stream Discharge and a Path Forward

Low flows pose unique challenges for accurately quantifying streamflow. Current field methods are not optimized to measure these conditions, which in turn, limits research and management. In this essay, we argue that the lack of methods for measuring low streamflow is a fundamental challenge that must be addressed to ensure sustainable water management now and into the future, particularly as climate change shifts more streams to increasingly frequent low flows. We demonstrate the pervasive challenge of measuring low flows, present a decision support tool (DST) for navigating best practices in measuring low flows, and highlight important method developmental needs

The Transport, Retention, and Fate of Novel Materials in Flowing Waters

Historically, stream ecology was formed on the basis of measuring how much organic matter rivers move downstream, and the “processing continuum” as this organic material is alternatively deposited, processed, and further transported. A significant amount of material is continuously exported from headwater streams, and via advection can be moved long distances downstream prior to processing. Along the way, these materials exchange rapidly between the water column and streambed, migrating downstream in alternating deposition and resuspension events called saltation, and are influenced by complexity in the physical and biologically template of stream structure. A new focus in ecology is understanding how “novel materials” are transported, retained, and persist in stream and river ecosystems. Despite many potential controls over material transport in streams and rivers, we often treat the transport of these materials as a homogenous process in the environment because we lack empirical observations addressing the complexity inherent in natural systems. Therefore, the overarching objective of my dissertation is to improve understanding of the transport, retention, and persistence of two novel materials that are actively transported by flowing waters using a combination of empirical and modeling approaches, spanning lab to watershed experimental scales. More specifically, I investigate the dynamics and transport of two novel materials: environmental DNA (eDNA) and a genetically modified protein (Cry1Ab)

Growing Up in SFS: Instars Participation From Mentees to Mentors

Mentoring Program encourages undergraduates from under-represented groups to pursue post-graduate degrees and careers in freshwater science. The program aims to provide a professional network among participants that includes mentorship by established professionals and graduate students, exposure to disciplinary approaches in science, and guidance in pursuing graduate education and careers in aquatic science. Participation in the Instars program as both mentees and mentors has facilitated our development as young professionals in the field of freshwater science. Our presentation will describe our initial society involvement as Instars fellows (2013). We are currently pursuing graduate degrees in freshwater science and have returned to society meetings in subsequent years as Instars Graduate Mentors (2014, 2015). Key themes in our presentation will include discussion of the benefits of mentoring for career development; the importance of developing networking skills, encouraging guidance, and participation in experiential activities for undergraduates; and the advantages of a peer-mentoring system for leadership development

Uncertainty in streamflow measurements significantly impacts estimates of downstream nitrate export

Across watershed science, two key variables emerge–streamflow and solute concentration–which serve as the basis for efforts ranging from basic watershed biogeochemistry research to policy decisions surrounding watershed management. However, we rarely account for how error in discharge (Q) impacts estimates of downstream nutrient loading. Here, we examined the impact of uncertainty in streamflow measurements on estimates of downstream nitrate export using publicly available data from the U.S. Geological Survey (USGS). We characterized how uncertainty in stage-discharge relationships impacts annual flux estimates across 70 USGS gages. Our results indicate the interquartile range of relative error in Q was 33% across these USGS sites. We documented a wide range in mean error in annual nitrate loads; some sites were underestimated (−105%), while predicted loads at other sites vastly overestimated (500%). Overall, any error in estimating Q leads to significant unpredictability of annual nutrient loads, which are often used as critical success benchmarks for governmental nutrient reduction strategies. Moreover, error in annual nitrate loads (as mass, kg) increases with mean Q; thus, as high flows become more unpredictable and intense under future climate change, error in estimates of downstream nutrient loading may also increase. Together, this indicates that error in Q may drastically influence our measures of water quality success and decrease our ability to accurately quantify progress towards algal bloom and ‘dead zone’ reduction

Ichawaynochaway Creek Data 1993-2022

Water chemistry data from the Ichawaynochaway Creek drainage.    On each sampling date, we collected 3 1-L samples and transported them to the lab on ice. We used unfiltered, room temperature subsamples to determine alkalinity with a Mettler DL12 titrator (Mettler-Toledo Inc., Columbus, Ohio). We filtered additional subsamples through a Gelman A/E, GFF, 0.7-μm nominal pore size to determine water chemistry according to standard procedures (see Battle and Golladay 2001). We measured dissolved organic carbon (DOC) with a Shimadzu TOC-5050 analyzer (Shimadzu Scientific Instruments, Kyoto, Japan). We determined NH4-N, NOx-N (NO3-N + NO2-N), and soluble reactive phosphorus (SRP) with a Lachat Quikchem 8000 flow-injection auto-analyzer using colorimetric methods (Lachat Instruments, Milwaukee, MN). We determined dissolved inorganic nitrogen (DIN) concentrations by summing the concentrations of NH4–N and NOX–N. Here, we report dissolved the dissolved molar ratios of C:N (i.e., DOC:DIN), C:P (i.e., DOC:SRP), and N:P (i.e., DIN:SRP).</p

Microplastic deposition velocity in streams follows patterns for naturally occurring allochthonous particles

Abstract Accumulation of plastic litter is accelerating worldwide. Rivers are a source of microplastic (i.e., particles <5 mm) to oceans, but few measurements of microplastic retention in rivers exist. We adapted spiraling metrics used to measure particulate organic matter transport to quantify microplastic deposition using an outdoor experimental stream. We conducted replicated pulse releases of three common microplastics: polypropylene pellets, polystyrene fragments, and acrylic fibers, repeating measurements using particles with and without biofilms. Depositional velocity (vdep; mm/s) patterns followed expectations based on density and biofilm ‘stickiness’, where vdep was highest for fragments, intermediate for fibers, and lowest for pellets, with biofilm colonization generally increasing vdep. Comparing microplastic vdep to values for natural particles (e.g., fine and coarse particulate organic matter) showed that particle diameter was positively related to vdep and negatively related to the ratio of vdep to settling velocity (i.e., sinking rate in standing water). Thus, microplastic vdep in rivers can be quantified with the same methods and follows the same patterns as natural particles. These data are the first measurements of microplastic deposition in rivers, and directly inform models of microplastic transport at the landscape scale, making a key contribution to research on the global ecology of plastic waste

Water Flow and Biofilm Cover Influence Environmental DNA Detection in Recirculating Streams

The increasing use of environmental DNA (eDNA) for determination of species presence in aquatic ecosystems is an invaluable technique for both ecology as a field and for the management of aquatic ecosystems. We examined the degradation dynamics of fish eDNA using an experimental array of recirculating streams, also using a “nested” primer assay to estimate degradation among eDNA fragment sizes. We introduced eDNA into streams with a range of water velocities (0.1–0.8 m s–1) and substrate biofilm coverage (0–100%) and monitored eDNA concentrations over time (∼10 d) to assess how biophysical conditions influence eDNA persistence. We found that the presence of biofilm significantly increased initial decay rates relative to previous studies conducted in nonflowing microcosms, suggesting important differences in detection and persistence in lentic vs lotic systems. Lastly, by using a nested primer assay that targeted different size eDNA fragments, we found that fragment size altered both the estimated rate constant coefficients, as well as eDNA detectability over time. Larger fragments (\u3e600 bp) were quickly degraded, while shorter fragments (\u3c100 \u3ebp) remained detectable for the entirety of the experiment. When using eDNA as a stream monitoring tool, understanding environmental factors controlling eDNA degradation will be critical for optimizing eDNA sampling strategies

Transport and instream removal of the Cry1Ab protein from genetically engineered maize is mediated by biofilms in experimental streams.

The majority of maize planted in the US is genetically-engineered to express insecticidal properties, including Cry1Ab protein, which is designed to resist the European maize borer (Ostrinia nubilalis). After crop harvest, these proteins can be leached into adjacent streams from crop detritus left on fields. The environmental fate of Cry1Ab proteins in aquatic habitats is not well known. From June-November, we performed monthly short-term additions of leached Cry1Ab into four experimental streams with varying benthic substrate to estimate Cry1Ab transport and removal. At the start of the experiments, when rocks were bare, we found no evidence of Cry1Ab removal from the water column, but uptake steadily increased as biofilm colonized the stream substrate. Overall, Cry1Ab uptake was strongly predicted by measures of biofilm accumulation, including algal chlorophyll a and percent cover of filamentous algae. Average Cry1Ab uptake velocity (vf = 0.059 ± 0.009 mm s-1) was comparable to previously reported uptake of labile dissolved organic carbon (DOC; mean vf = 0.04 ± 0.008 mm s-1). Although Cry1Ab has been shown to rapidly degrade in stream water, benthic biofilms may decrease the distance proteins are transported in lotic systems. These results emphasize that once the Cry1Ab protein is leached, subsequent detection and transport through agricultural waterways is dependent on the structure and biology of receiving stream ecosystems

Estimating fish alpha- and beta-diversity along a small stream with environmental DNA metabarcoding

Environmental DNA (eDNA) metabarcoding has been increasingly applied to biodiversity surveys in stream ecosystems. In stream networks, the accuracy of eDNA-based biodiversity assessment depends on whether the upstream eDNA influx affects downstream detection. Biodiversity assessment in low-discharge streams should be less influenced by eDNA transport than in high-discharge streams. We estimated α- and β-diversity of the fish community from eDNA samples collected in a small Michigan (USA) stream from its headwaters to its confluence with a larger river. We found that α-diversity increased from upstream to downstream and, as predicted, we found a significant positive correlation between β-diversity and physical distance (stream length) between locations indicating species turnover along the longitudinal stream gradient. Sample replicates and different genetic markers showed similar species composition, supporting the consistency of the eDNA metabarcoding approach to estimate α- and β-diversity of fishes in low-discharge streams.ISSN:2534-970