Quantifying Variability in Four U.S. Streams Using a Long-Term Dataset: Patterns in Biotic Endpoints.

Effective water resources assessment and management requires quantitative information on the variability of ambient and biological conditions in aquatic communities. Although it is understood that natural systems are variable, robust estimates of long-term variation in community-based structure and function metrics are rare in U.S. waters. We used a multi-year, seasonally sampled dataset from multiple sites (n = 5-6) in four streams (Codorus Creek, PA; Leaf River, MS; McKenzie and Willamette Rivers, OR) to examine spatial and temporal variation in periphyton chlorophyll a, and fish and macroinvertebrate metrics commonly used in bioassessment programs. Within-site variation of macroinvertebrate metrics and benthic chlorophyll a concentration showed coefficient of variation ranging from 16 to 136%. Scale-specific variability patterns (stream-wide, season, site, and site-season patterns) in standardized biotic endpoints showed that within-site variability patterns extended across sites with variability greatest in chlorophyll a and lowest in Hilsenhoff's Biotic Index. Across streams, variance components models showed that variance attributed to the interaction of space and time and sample variance accounted for the majority of variation in macroinvertebrate metrics and chlorophyll a, while most variation in fish metrics was attributed to sample variance. Clear temporal patterns in measured endpoints were rare and not specific to any one stream or assemblage, while apparent shifts in metric variability related to point source discharges were seen only in McKenzie River macroinvertebrate metrics in the fall. Results from this study demonstrate the need to consider and understand spatial, seasonal, and longer term variability in the development of bioassessment programs and subsequent decisions.

Deriving Human Health and Aquatic Life Water Quality Criteria in the United States for Bioaccumulative Substances: A Historical Review and Future Perspective.

Methods used to derive water quality regulations for persistent, bioaccumulative, and toxic substances (PBTs) in the United States have evolved substantially over the past 50 yr, leveraging current understandings and assumptions about the nature and magnitude of partitioning and accumulation of substances in water, sediments, and organisms. In the United States and across the world, environmental regulations continue to evolve into more refined water quality criteria protective of aquatic life and human health. The present review provides historical context on the establishment of aquatic life and human health water quality criteria in the United States by compiling information from regulatory agencies and peer-reviewed literature on methods used to characterize and quantify bioaccumulation of substances in aquatic organisms and humans. Primary data needs and assumptions for various methods, as well as their application in setting criteria by the US Environmental Protection Agency over the past half century, are highlighted. Our review offers an important retrospective on the data and methods used to derive water quality criteria for PBTs and provides commentary on the future of US criteria development. Environ Toxicol Chem 2021;40:2394-2405. © 2021 SETAC.

Patterns of macroinvertebrate assemblages in a long-term watershed-scale study to address the effects of pulp and paper mill discharges in four US receiving streams.

Changes in macroinvertebrate communities exposed to pulp and paper mill effluent (PPME) have been seen in mesocosm and short-term field studies. However, long-term patterns of macroinvertebrates in PPME receiving streams have not been examined. We conducted a study of 4 PPME receiving streams (Codorus Creek, PA; the Leaf River, MS; and the McKenzie and Willamette rivers, OR) over 9 y to assess temporal patterns in macroinvertebrate community structure and metrics related to PPME discharge. Study streams represented different ecoregions, warm-/cold-water systems, gradients of PPME concentration (<1%-33%), and mill process types. Bray-Curtis similarity and nonmetric multidimensional scaling showed significant community differences across sites in Codorus Creek, but differences were related to stream temperature patterns and not PPME. In the other study streams, seasonal community differences across years were greater than differences across sites. General linear models were used to examine spatial and temporal variation in macroinvertebrate metric response (% dominant taxa, density, richness, Hilsenhoff Biotic Index [HBI], Simpson's Index, and ash-free dry mass). Mean HBI scores indicated that the macroinvertebrate community reflected fair to very good water quality conditions, with water quality typically classified as "good" at most sites. Significant site differences in macroinvertebrate metric response were uncommon in the Leaf, McKenzie, and Willamette rivers but were seen in all metrics in Codorus Creek, where metric response was spatially variable. In the McKenzie River, there was an increase in mean HBI scores at sites downstream of the mill relative to 1 of the 2 upstream sites. However, significant differences were seen only between 1 upstream and downstream site, and HBI scores at all downstream sites consistently reflected "good" water quality. Significant annual differences in metric response were typical in all rivers. Water quality (pH, conductivity, total nitrogen) and habitat (velocity, depth, substrate composition) variables explained community structure patterns in the Leaf and McKenzie rivers, but macroinvertebrate-environment relationships were weak in the other 2 streams. The results of this study indicate that macroinvertebrate community structure is temporally variable and reiterate the importance of long-term studies for accurate determination of the effects of point sources such as PPME on receiving systems.

Patterns of fish community structure in a long-term watershed-scale study to address the aquatic ecosystem effects of pulp and paper mill discharges in four US receiving streams.

Physiological changes have been seen in individual fish exposed to pulp and paper mill effluent (PPME), but it is unclear whether community-level changes are seen in fish in PPME receiving waters. We conducted a study of 4 PPME receiving streams (Codorus Creek, PA, USA), the Leaf River (Forrest and Perry Counties, MS, USA), and the McKenzie and Willamette rivers (Lane County, OR, USA) over 9 y to assess temporal patterns in the type and relative abundance of fish species and measures of community structure and function related to PPME discharge. We used boat and backpack electrofishing to sample large- and small-bodied fish from the McKenzie and Willamette rivers, boat electrofishing to sample large-bodied fish from the Leaf River, and backpack electrofishing to sample the entire fish community from Codorus Creek. Study streams represented different ecoregions, warm- and coldwater systems, gradients of PPME concentration (<1%-33%), and mill process types. Bray-Curtis similarity and nonmetric multidimensional scaling showed high variation in fish communities across sites, seasons, and years. Significant site differences in fish communities were seen in most streams and community types, but distinct separation of sites was seen only in Codorus Creek and unrelated to PPME discharge. No seasonal differences were seen in fish community structure in any stream, with only weak annual patterns in large-bodied fish in the Leaf River and small-bodied fish in the McKenzie River. General linear models were used to examine spatial and temporal variation in fish metric response (abundance, species richness, Simpson's diversity, % dominant species, standing crop, % DELT, % intolerant, % omnivore, % piscivore). Significant site differences in metric response were largely limited to Codorus Creek and unrelated to PPME. Significant reductions of % dominant taxa of small-bodied fish and % large-bodied piscivores were also observed downstream of the PPME discharge on the McKenzie River relative to upstream sites. Seasonal changes in fish metric response were rare, and changes with year were variable. The relationship between fish community structure and water quality variables (pH, color, conductivity, total phosphorus, total nitrogen) was weak in all streams for all community types. The results of this study show that PPME exposure has little effect on fish communities in these streams and aid in addressing management strategies. The high spatial and temporal variability reiterate the importance of long-term studies to elucidate patterns in receiving waters.

A long-term, multitrophic level study to assess pulp and paper mill effluent effects on aquatic communities in four US receiving waters: characteristics of the study streams, sample sites, mills, and mill effluents.

Watershed characteristics, study streams, sample sites, mills, and mill effluents are provided for 4 streams included in a long-term study to assess potential effects of pulp and paper mill effluents on US receiving waters. The study streams are Codorus Creek (Pennsylvania, USA), Leaf River (Mississippi, USA) and McKenzie and Willamette rivers (Oregon, USA) and were chosen to represent a blend of mill process types, effluent concentrations, and coldwater/warmwater stream systems. The described effluent quality, water quality, and habitat data sets encompass the initial 7 to 8 y of a study anticipated to continue >10 y and provide a backdrop to a series of articles describing periphyton, macroinvertebrate, and fish community properties in these same streams. The mean in-stream waste concentration (IWC) for these 4 effluent discharges was 32.4%, 2.0%, 0.5%, and 0.2% v/v for Codorus Creek and Leaf, McKenzie, and Willamette rivers, respectively, as compared with a median of 0.4% for US mills. Effluent quality measurements included Selenastrum capricornutum, Ceriodaphnia dubia, and Pimephales promelas chronic bioassays as sanctioned by the US Environmental Protection Agency for estimating effluent effects on receiving-water aquatic communities. Based on mean bioassay inhibition concentration for a 25% effect and on mean IWC, a margin of safety against adverse biological effects of 2, 25, 137, and 150 times was indicated for Codorus Creek and Leaf, McKenzie, and Willamette rivers, respectively. Habitat and water quality assessment was carried out over a gradient of sample sites above and below the effluent discharge to determine nonmill-related conditions that might interfere with interpretation of effluent effects. Noneffluent related localized differences in conditions for some parameters, including current velocity (McKenzie River), and surface incident photosynthetically active radiation (Codorus Creek and Willamette River) occurred at the sample stations immediately upstream or downstream of the effluent discharge. In addition, broader watershed differences were evident on Codorus Creek, where a relatively rich riparian corridor and stream structure occurred upstream in contrast to areas of canopy and stream-structure loss in the downstream urban area. The mill effluent discharges contributed to increases in receiving-water color and conductivity, although upstream tributaries contributed additional conductivity to Codorus Creek and color to the Leaf River. The McKenzie River provided the only example of a nutrient increase immediately downstream of a mill discharge. This increase in total nitrogen (0.11 vs 0.16 mg/L) could not, however, be differentiated with respect to whether it was of mill effluent or tributary stream origin. Tributary streams were potentially important total nitrogen contributors on Codorus Creek and the Willamette River. As an integrated study, the effluent quality and physical/chemical watershed descriptions provided here represent 1 component of the broader study addressing potential point-source effluent effects within the context of the larger watershed and a multiyear timescale. The absence of effluent-related in-stream chemical/physical responses, other than increases in conductivity and color, and a considerable bioassay-based margin of safety, provides for a working hypothesis that there will be no effluent-related biological population/community responses from these 4 mill discharges. This hypothesis, as it relates to periphyton, macroinvertebrate, and fish communities, will be addressed in other articles in this series.