Heterosternuta sulphuria (Coloptera: Dytiscidae) Occurence in the Sulphur Springs Headwater System and in Buffalo National River Tributaries (Arkansas, USA): Current Distribution, Habitat Conditions, and Biomonitoring Framework

Heterosternuta sulphuria is an endemic aquatic species of concern in Arkansas, with a priority score of 80 out of 100 and a conservation rank of S1and G1. A need of the Arkansas Wildlife Action Plan (AWAP) was to obtain baseline information on distribution and population status of H. sulphuria. Here, we report new H. sulphuria records for 39 sites across 10 counties in the Ozark Highlands and Boston Mountain ecoregions and a determined habitat type of shallow margins and small bedrock pools of perennial streams and spring seeps. Few habitat patches were observed per site because detection was typically rapid and (unconfirmed) field identifications were possible because of the unique coloration of the pronotum, therefore only a small portion of the total available habitat was surveyed. We conclude that from our surveys and information gathered from other sources that in Arkansas H. sulphuria is probably ubiquitous among permanently wet aquatic habitats (primarily in upland headwater systems) throughout the Ozark Highlands and Boston Mountain ecoregions. Based on the number of occurrences, we recommend a downgrade of conservation status to S3 or S4. While some locations provide protection for current H. sulphuria populations (e.g., Buffalo National River, Hobbs State Park – Conservation Area, Sherfield Cave effluent stream, and USFS Richland Creek Wilderness), populations on unprotected lands in urban and agricultural settings probably have a much greater risk of population decline. A final determination of conservation status should consider several factors including dispersal capacity, population sizes, and genetic differentiation among populations. Furthermore, determining if existing H. sulphuria populations are isolated subpopulations or an interacting metapopulation and the habitat area required for population persistence are key for developing effective conservation actions. Monitoring existing populations should involve revisiting current H. sulphuria sites, and this is especially important for potentially fragmented populations in unprotected streams. Bioassessment programs could benefit from monitoring these easily observed populations that might positively relate to the overall physical and biological integrity of permanent Ozark streams and riparian corridors

Frequency Distributions of Median Nutrient and Chlorophyll Concentrations across the Red River Basin, 1996-2006

Acquisition and compilation of water quality data for a ten year time period (1996 – 2006) from 589 stream and river stations was conducted to support nutrient criteria development for the multi–state Red River Basin shared by Arkansas, Louisiana, New Mexico, Oklahoma and Texas, USA. Twenty–three water quality parameters were collected from five data sources (USGS, ADEQ, LDEQ, OCC, OWRB, and TCEQ) and an additional 13 parameters were acquired from at least one source. Data for the primary biological parameter of interest, chlorophyll a, was sparse and available from only two sources. Following compilation of data, medians were calculated for the ten year period and median distributions (min, 10th, 25th, 50th, 75th, 90th percentiles and max) were presented for several different spatial scales including state specific data, HUC8 designated watersheds, and various ecoregions. Across this basin, median values for total nitrogen (TN), total phosphorus (TP), and sestonic chlorophyll–a (chl–a) ranged from \u3c0.02 to 20.2 mg L⁻¹, \u3c0.01 to 6.66 mg L⁻¹, and 0.10 to 26 µg L⁻¹, respectively. Overall, the 25th percentiles of median TN data specific to the Red River Basin were generally similar to the USEPA recommended eco–region nutrient criteria. Whereas, median TP and chl–a data specific to the Red River Basin showed 25th percentiles greater than the USEPA recommended criteria. The unique location of the Red River Basin in the south–central USA places it near the boundaries of several aggregate eco–regions; therefore, the development of eco–region nutrient criteria likely requires using data specific to the Red River Basin, as shown in these analyses. This study provided basin–specific distribution of medians as the first step supporting states in developing nutrient criteria to protect designated uses in the multi–jurisdictional Red River Basin and in potentially reducing nutrient export from the Red River Basin to the Gulf of Mexico

Bioassessment of Four Karst Springs at Hobbs State Park – Conservation Area with a Focus on Diving Beetle (Dytiscidae: Hydroporinae) Species of Concern

Four springs were surveyed at Hobbs State Park-Conservation Area to provide an initial bioassessment and to determine occurrences of two endemic predaceous diving beetles of concern, Heterosternuta sulphuria and Sanfilippodytes sp. Habitat in the four spring runs were dominated by bedrock and gravel substrate with heavy accumulations of leaf litter. Thirty-three taxa representing 11 orders were collected from the four springs. Non-insect taxa included Oligochaeta, Physidae, and Isopoda, and predominant insect orders included Ephemeroptera, Coleoptera, Diptera, and Trichoptera. The total number of taxa across springs ranged from seven to 19, with total abundances ranging from 39 to 86 individuals. No individual taxon occurred across all four springs. Percent tolerant organisms and the Hilsenhoff Biotic Index showed that spring communities were dominated by taxa tolerant to organic pollution, likely because of low flows and heavy accumulations of leaves. Predators were the dominant functional group followed by shredders. The endemic, predaceous diving beetle Heterosternuta sulphuria was collected from two springs and Sanfilippodytes sp. was collected from three springs. One spring contained the largest number of Sanfilippodytes sp. individuals recorded among all other aquatic habitats surveyed to date. Findings highlight the importance of spring systems at Hobbs State Park Conservation Area for endemic-species conservation, while information on the invertebrate community provides a baseline for future monitoring and comparison

Sestonic Chlorophyll-a and Nutrient Relationships Across the Red River Basin, USA

The Red River is a trans‐boundary, multi‐jurisdictional basin, where water‐quality standards often change at the state lines. The state agencies with USEPA Region VI focused resources to organize water‐quality data from within this basin and have it statistically analyzed to evaluate the relationships between nutrients and sestonic chlorophyll‐a (chl‐a). There were 152 sites within the Red River Basin that had nutrient and sestonic chl‐a data, and these sites were narrowed down to 132 when a minimum number of observations was required. Sestonic chl‐a levels increased with increasing nutrient concentrations; these significant regressions were used to predict nutrient concentrations at 10 µg chl‐a L⁻¹. Total nitrogen (TN) and phosphorus (TP) concentrations (at 10 µg chl‐a L⁻¹ ) varied across the Red River Basin and its eco‐regions from 0.10‐0.22 mg TP L⁻¹ and 0.75‐2.11 mg TN L⁻¹ . Nutrient thresholds were also observed with sestonic chl‐a at 0.14 mg TP L⁻¹ and 0.74 mg TN L⁻¹ using categorical and regression tree analysis (CART). CART analysis also revealed that hierarchical structure was important when attempting to predict sestonic chl‐a from TN, TP and conductivity. The ranges of TN and TP concentrations that resulted in chl‐a concentrations which exceeded 10 µg chl‐a L⁻¹ were similar in magnitude to the threshold in TN and TP that resulted in increased sestonic chl‐a. This corroborating evidence provides useful guidance to the states with jurisdiction within the Red River Basin for establishing nutrient criteria, which might be similar when the Red River and its tributaries cross political boundaries

Phosphorus Mitigation to Control River Eutrophication: Murky Waters, Inconvenient Truths, and “Postnormal” Science

This commentary examines an "inconvenient truth" that phosphorus (P)-based nutrient mitigation, long regarded as the key tool in eutrophication management, in many cases has not yet yielded the desired reductions in water quality and nuisance algal growth in rivers and their associated downstream ecosystems. We examine why the water quality and aquatic ecology have not recovered, in some case aft er two decades or more of reduced P inputs, including (i) legacies of past land-use management, (ii) decoupling of algal growth responses to river P loading in eutrophically impaired rivers; and (iii) recovery trajectories, which may be nonlinear and characterized by thresholds and alternative stable states. It is possible that baselines have shifted and that some disturbed river environments may never return to predisturbance conditions or may require P reductions below those that originally triggered ecological degradation. We discuss the practical implications of setting P-based nutrient criteria to protect and improve river water quality and ecology, drawing on a case study from the Red River Basin in the United States. We conclude that the challenges facing nutrient management and eutrophication control bear the hallmarks of "postnormal" science, where uncertainties are large, management intervention is urgently required, and decision stakes are high. We argue a case for a more holistic approach to eutrophication management that includes more sophisticated regime-based nutrient criteria and considers other nutrient and pollutant controls and river restoration (e.g., physical habitat and functional food web interactions) to promote more resilient water quality and ecosystem functioning along the land-freshwater continuum

Fig. 2 in Descriptions of the Second and Third Instars of Heterosternuta sulphuria(Matta and Wolfe) (Coleoptera: Dytiscidae: Hydroporinae), with A Key For Identification of the Known Larvae of Heterosternuta Strand

Fig. 2. Heterosternuta sulphuria, third instar, last abdominal segment and urogomphus, dorsal aspect. Scale bar = 0.1 mm.Published as part of <i>Alarie, Yves & Longing, Scott D., 2010, Descriptions of the Second and Third Instars of Heterosternuta sulphuria(Matta and Wolfe) (Coleoptera: Dytiscidae: Hydroporinae), with A Key For Identification of the Known Larvae of Heterosternuta Strand, pp. 85-90 in The Coleopterists Bulletin 64 (1)</i> on page 86, DOI: 10.1649/0010-065x-64.1.85, <a href="http://zenodo.org/record/10102063">http://zenodo.org/record/10102063</a&gt

Flight Capacity and Response to Habitat Drying of Endemic Diving Beetles (Coleoptera: Dytiscidae) in Arkansas (USA)

The ability to colonize new habitat is essential for wild populations affected by disturbance or other forms of habitat change. For aquatic insects in small streams, overland flight is an important strategy for dispersal when barriers to in-stream migration exist and when populations are isolated in upland habitats. Two Ozark-endemic water beetles (Heterosternuta sulphuria and Heterosternuta phoebeae) have shown little overlap in distributions, with the former frequently occurring in small upland watersheds and the latter occurring in aquatic habitats farther downstream in larger watersheds. Because H. sulphuria has been associated with perennial aquatic habitats, we hypothesized that H. sulphuria individuals could exhibit low capacity for flight, thereby affecting population distributions over time. Laboratory flight observations showed that zero individuals of H. sulphuria flew (n = 67), whereas 17 of 76 individuals of H. phoebeae were observed to fly. Stream habitat drying experiments provided further evidence of the weak capacity for flight and overland migration of H. sulphuria, with low probabilities of survivorship in microhabitats exposed to drying. Weak flight capacity and apparent intolerance to habitat drying have important implications for the evolutionary history and conservation of H. sulphuria in small Ozark streams exposed to variable flow regimes and stream margins vulnerable to disturbances