Long term bioassessment multiple stressors study in a residential California stream.

The relationship of various benthic metrics to physical habitat metrics, pyrethroids, metals and sediment parameters was evaluated for a 10 year data set in Pleasant Grove Creek (Roseville, California) using univariate linear models, stepwise multiple regressions, and canonical correlation analysis. In general, total physical habitat scores in this residential stream were considered to be marginal to suboptimal. The most dominant benthic taxa were generally considered to be tolerant of environmental stressors and the benthic communities were rated as impaired based on a benthic index. Potentially toxic sediment concentrations of cadmium, chromium, copper, nickel and zinc were reported at various sites based on a comparison with existing threshold effect levels. The sum of pyrethroid Toxics Units (TUs) indicated that 10 of 21 sites based on a sensitive Hyalella laboratory toxicity test had TUs greater than one thus suggesting toxicity at various sites. In summary, the effects of the physical habitat, as reflected by certain habitat metrics that were indicative of stream-flow, hydrology, habitat diversity, and substrate quality overshadowed any apparent effects of pyrethroids and metals on shaping resident benthic communities when all environmental variables were considered in multivariate analyses.

Bootstrap simulations to estimate relationships between Type I error, power, effect size, and appropriate sample numbers for bioassessments of aquatic ecosystems.

The Extended Bootstrap (EB) assessment approach was developed for the examination of relationships of Type I error, power, sample size (n), and effect size (ES) for statistical tests of ecological data. The EB approach was applied to univariate and multivariate statistical analyses of a large data set collected from an ongoing, multiple stressor bioassessment study of watersheds in the Central Valley, San Francisco, and Central Coast areas of California. Benthic metrics were created that either increased or decreased monotonically with stress (toxicants or metrics indicative of habitat quality). Type I errors were stable for all statistical tests that were evaluated. The relationships between n and ES displayed patterns of "diminishing returns" for all statistical tests: i.e. an increasingly larger n was required to detect decreasingly smaller ES. Nonetheless, the n's collected across the watersheds and within a selected watershed were sufficient to detect even small correlations between representative benthic metrics and potential stressors with high power. The power and robustness of a novel method using EB and previously described statistical techniques designed to address multicollinearity were shown to approach those of simpler univariate regressions. Potential applications of the EB approach for experimental design, data assessment and interpretation, and hypothesis testing are discussed.

Multivariate spatial patterns analysis of environmental variables and benthic metrics in five California waterbodies.

Multivariate spatial patterns of 38 environmental variables (habitat metrics, metals, pyrethroids and sediment characteristics) and 14 benthic metrics were determined from over a decade of sampling in five California waterbodies. Canonical discriminant analyses produced very highly significant separations of the five watersheds based on environmental variables. The discriminant analyses based on benthic metrics also produced highly significant separations, although confidence ellipses were not quite as well separated as the environmental variables. Separation of creeks made ecological sense as Pleasant Grove Creek (PGC), which appeared to have greater habitat quality also had benthic metrics indicative of less stressed benthic communities, while the Santa Maria River watershed (SM) appeared to have lower habitat quality and more toxicants in the sediments also appeared to have benthic communities indicative of stress-tolerant taxa. The benthic community health of the other three creeks (Arcade Creek [ARC], Kirker Creek [KC] and Salinas Streams [SAL]) were considered intermediate in apparent stress between PGC and SM. Overall, benthic communities were somewhat more similar between creeks than were the environmental conditions. Benthic communities have greater overlap in characteristics than would be expected from environmental conditions, perhaps due to a greater resilience since they are generally dominated by tolerant benthic taxa.

Ranking the importance of benthic metrics and environmental stressors from over a decade of bioassessment multiple stressor studies in five California waterbodies.

Comprehensive bioassessment multiple stressor field studies were conducted in five waterbodies in the Central Valley, San Francisco and Central Coast areas of California between 2006 and 2017. Samples were collected over multiple years in Pleasant Grove Creek (PGC - 8 years), Kirker Creek (KC - 2 years), Arcade Creek (ARC - 3 years), Salinas streams (SAL - 3 years) and the lower Santa Maria River watershed (SM - 3 years). In each watershed, metrics indicative of physical habitat quality and the relative health of benthic communities were collected, along with measurements of various potential toxicants in sediment (metals and pyrethroids), total organic carbon (TOC) and sediment grain size characteristics. For all waterbodies, pyrethroids have been reported at concentrations suspected to be toxic based on single-species laboratory toxicity tests. The data from all of these studies were assembled into a single data base which was analyzed by a series of univariate and multivariate statistical analyses. These analyses were designed to examine overall relationships between benthic community health and environmental quality conditions across the watersheds, as well as to address the following two key questions: (1) Which benthic metrics (response indicators) were the most important to relationships with environmental quality conditions and how do these metrics rank from most to least important? and (2) Which environmental variables (stressors) were the most important in terms of relationships to benthic metrics indicative of community health and how do the stressors rank from most to least important? Consensus ranking of 14 benthic metrics showed that stress tolerant (% Tolerant taxa, Tolerance value and Collectors/gatherers) and stress sensitive (EPT taxa and taxa richness) were the most important. The consensus ranking of 38 environmental variables from most to least important showed that habitat metrics, metals and grain size characteristics were most important for shaping benthic communities while pyrethroids were not reported to be an important stressor across the geographic scope of the watersheds.

The influence of multiple chemical and non-chemical stressors on benthic communities in a mid-west agricultural stream.

The objective of this 3-year study was to characterize benthic communities and physical habitat in an agricultural stream in the mid-west area of the United States (Big Bureau Creek, Illinois). Concurrent basic water quality parameters and seven nutrients were measured in the water column. Sediment measurements from depositional areas were conducted for bifenthrin, Total Organic Carbon, grain size, polychlorinated biphenyls (PCBs) and eight metals. All parameters were measured at 12 sites annually during the late summer for a 3-year period (2014, 2015 and 2016). Univariate regressions, stepwise multiple regressions and canonical correlation statistical analyses were used to determine the relationship between various benthic metrics (i.e., taxa richness and abundance) and all the measured parameters for the 3-year database. Benthic communities comprising 108-110 taxa were collected annually, and were generally dominated by sensitive caddisflies and mayflies. These communities were rated as good to exceptional using the Ohio Invertebrate Community Index. Physical habitat for the various sites was rated as good using the Ohio Qualitative Habitat Evaluation Index, thus suggesting that habitat is not a significant stressor that would likely impact resident benthic communities. Based on a comparison of measured in-stream total nitrogen and total phosphorus concentrations and criterion value exceedances, it appears that the in-stream nutrient concentrations could be potentially stressful to resident benthic biota. Metal concentrations were below established NOAA Threshold Effects Levels at all sites. Measured PCB concentrations were below levels of detection at all sites. Toxic units' (TUs) calculations based on using sensitive laboratory strains of Hyalella were less than 0.1 for bifenthrin, thus suggesting that bifenthrin sediment toxicity was unlikely. Thirty significant relationships reported between benthic metrics and the various environmental variables based on the 3-year database were as follows: 12 relationships with habitat metrics, 8 relationships with metals, 7 relationships with nutrients, 2 relationships with bifenthrin and 1 relationship with sediment characteristics. Relative habitat quality, habitat preferences, and ecological competition appear to be factors that shape the characteristics of the benthic communities of Big Bureau Creek, rather than stress imposed by toxicants (bifenthrin and metals), nutrients, or sediment characteristics. Complex relationships between benthic metrics and environmental variables are discussed.

The relationship of benthic community metrics to pyrethroids, metals, and sediment characteristics in Cache Slough, California.

A bioassessment multiple stressor study was conducted at 12 sites in Cache Slough, California during the Spring and Fall of 2012, 2013 and 2014. Specific study goals were to: (1) collect and identify benthic macroinvertebrates and develop a suite of benthic metrics; (2) measure total organic carbon (TOC), grain size, bulk metals, simultaneously extracted metals (SEM) and acid volatile sulfides (AVS), and 8 pyrethroids in sediment; (3) measure basic water quality parameters; and, (4) use univariate and stepwise multiple regressions and canonical correlation analysis to determine the relationship between various benthic metrics (i.e., taxa richness, abundance) and TOC, grain size, metals (bulk metals and SEM/AVS) and pyrethroids using the 3-year database. Five benthic metrics showed statistically significant relationships with environmental variables. Taxonomic Richness, a metric that decreases with stress, tended to be greater in less organic-rich, coarser sediments and the apparent relationships with toxicants such as pyrethroids or metals were diminished when these conditions are taken into account. The % Amphipod metric, which has a variable response to environmental stressors, showed a direct relationship with arsenic, an inverse relationship with chromium and an inverse relationship with % silt. The % Corbicula metric, which has a variable response to environmental stressors, was directly correlated with cypermethrin and nickel. Therefore, it appears that Corbicula tends to be associated with more contaminated sediments in Cache Slough. The metric % Collectors/Filterers & Collectors/Gatherers, a metric that increases in stressed environments, was reported to increase in sediments with higher arsenic concentrations. This relationship makes ecological sense because this metric should increase with an increase in arsenic concentrations. The benthic metric Abundance, a metric that decreases with stress, was reported to be inversely correlated with % TOC and % silt. The abundance of benthic communities increases in coarser, less organic rich sediments. In general, relatively few statistically significant relationships were observed between the various combinations of benthic metrics and environmental variables. Benthic communities in Cache Slough appear to be more closely associated with sediment characteristics and with metals concentrations than with the pyrethroid concentrations.

A ten year summary of concurrent ambient water column and sediment toxicity tests in the Chesapeake Bay watershed: 1990-1999.

The goal of this study was to identify the relative toxicity of ambient areas in the Chesapeake Bay watershed by using a suite of concurrent water column and sediment toxicity tests at seventy-five ambient stations in 20 Chesapeake Bay rivers from 1990 through 1999. Spatial and temporal variability was examined at selected locations throughout the 10 yr study. Inorganic and organic contaminants were evaluated in ambient water and sediment concurrently with water column and sediment tests to assess possible causes of toxicity although absolute causality can not be established. Multivariate statistical analysis was used to develop a multiple endpoint toxicity index (TOX-INDEX) at each station for both water column and sediment toxicity data. Water column tests from the 10 yr testing period showed that 49% of the time, some degree of toxicity was reported. The most toxic sites based on water column results were located in urbanized areas such as the Anacostia River, Elizabeth River and the Middle River. Water quality criteria for copper, lead, mercury, nickel and zinc were exceeded at one or more of these sites. Water column toxicity was also reported in localized areas of the South and Chester Rivers. Both spatial and temporal variability was reported from the suite of water column toxicity tests. Some degree of sediment toxicity was reported from 62% of the tests conducted during the ten year period. The Elizabeth River and Baltimore Harbor stations were reported as the most toxic areas based on sediment results. Sediment toxicity guidelines were exceeded for one or more of the following metals at these two locations: arsenic, cadmium, chromium, copper, lead, nickel and zinc. At the Elizabeth River stations nine of sixteen semi-volatile organics and two of seven pesticides measured exceeded the ER-M values in 1990. Ambient sediment toxicity tests in the Elizabeth River in 1996 showed reduced toxicity. Various semi-volatile organics exceeded the ER-M values at a number of Baltimore Harbor sites; pyrene and dibenzo(a,h)anthracene were particularly high at one of the stations (Northwest Harbor). Localized sediment toxicity was also reported in the Chester, James, Magothy, Rappahannock, and Potomac Rivers but the link with contaminants was not determined. Both spatial and temporal variability was less for sediment toxicity data when compared with water column toxicity data. A comparison of water column and sediment toxicity data for the various stations over the 10 yr study showed that approximately half the time agreement occurred (either both suite of tests showed toxicity or neither suite of tests showed toxicity).