03185nas a2200229 4500008004100000245013000041210006900171300001300240490000700253520244800260653001802708653001602726653001902742653002202761653002102783653001802804100002202822700001802844700001802862700001602880856005902896 2009 eng d00aThresholds in macroinvertebrate biodiversity and stoichiometry across water-quality gradients in Central Plains (USA) streams0 aThresholds in macroinvertebrate biodiversity and stoichiometry a a855 -8680 v283 a

N and P often limit primary and secondary production in ecosystems, but they also can cause eutrophication and negatively influence sensitive species above a certain level or threshold point. Aquatic biodiversity can have negative threshold relationships with water-quality variables at large scales, but the specific mechanism(s) driving these threshold relationships are not well established. We hypothesized that resource quality (i.e., C:P) might partly drive primary consumer (grazer and detritivore) richness thresholds by altering competitive interactions among species with differing resource demands, but might have less influence on predator richness. We estimated total N (TN), total P (TP), and turbidity thresholds for macroinvertebrate richness across trophic levels and feeding groups in Central Plains (USA) streams. We also determined if mean taxon body C:P of groups with diversity losses were negatively related to TP, a pattern that would suggest that eutrophic communities were dominated by a few species with high dietary P demands. Primary consumers were more sensitive to TN and TP (threshold mean  =  1.0 mg N/L and 0.06 mg P/L) than secondary consumers (threshold mean  =  0.09 mg P/L), a result supporting the resource quality hypothesis. Turbidity reduced richness regardless of feeding mode (threshold mean  =  4.7 NTU), a result suggesting that turbidity and nutrient thresholds were driven by different factors. The TP-richness threshold could be driven partially by changes in food quality because the mean body C:P of shredding and collector-gathering taxa declined as TP increased (threshold mean  =  0.07 and 0.75 mg P/L, respectively). Mean scraper C:P was not related to TP, a result indicating other factors might be responsible for the scraper richness threshold. Our results suggest that changes in resource quality could contribute to large-scale losses in biodiversity in nutrient-enriched lotic ecosystems. Within shredder and collector-gatherer macroinvertebrate feeding groups, P-rich food might allow faster growing taxa with high body P demands to out-compete slower growing taxa adapted to lower quality food resources. This pattern suggests that biotic integrity is directly linked to nutrients in streams and that toxicity, low dissolved O2, and increased turbidity might not be the only mechanisms leading to reductions in diversity as nutrient concentrations increase.

10abioassessment10abreakpoints10aeutrophication10anutrient criteria10aSpecies richness10awater quality1 aEvans-White, M.A.1 aDodds, W., K.1 aHuggins, D.G.1 aBaker, D.S. uhttps://www.journals.uchicago.edu/doi/10.1899/08-113.102269nas a2200205 4500008004100000245005300041210005300094300001300147490000700160520164700167653003501814653002201849653003001871653001901901653001801920653002501938100001801963700001601981856006601997 2008 eng d00aHeadwater influences on downstream water quality0 aHeadwater influences on downstream water quality a367 -3770 v413 a

We investigated the influence of riparian and whole watershed land use as a function of stream size on surface water chemistry and assessed regional variation in these relationships. Sixty-eight watersheds in four level III U.S. EPA ecoregions in eastern Kansas were selected as study sites. Riparian land cover and watershed land use were quantified for the entire watershed, and by Strahler order. Multiple regression analyses using riparian land cover classifications as independent variables explained among-site variation in water chemistry parameters, particularly total nitrogen (41%), nitrate (61%), and total phosphorus (63%) concentrations. Whole watershed land use explained slightly less variance, but riparian and whole watershed land use were so tightly correlated that it was difficult to separate their effects. Water chemistry parameters sampled in downstream reaches were most closely correlated with riparian land cover adjacent to the smallest (first-order) streams of watersheds or land use in the entire watershed, with riparian zones immediately upstream of sampling sites offering less explanatory power as stream size increased. Interestingly, headwater effects were evident even at times when these small streams were unlikely to be flowing. Relationships were similar among ecoregions, indicating that land use characteristics were most responsible for water quality variation among watersheds. These findings suggest that nonpoint pollution control strategies should consider the influence of small upland streams and protection of downstream riparian zones alone is not sufficient to protect water quality.

10ageographic information systems10aHeadwater streams10aNonpoint source pollution10aRiparian zones10awater quality10aWatershed management1 aDodds, W., K.1 aOakes, R.M. uhttps://link.springer.com/article/10.1007%2Fs00267-007-9033-y02561nas a2200193 4500008004100000245009700041210006900138300001300207490000700220520190300227653001302130653001502143653002202158653001302180653001802193100001802211700001602229856012202245 2006 eng d00aControls on nutrients across a prairie stream watershed: Land use and riparian cover effects0 aControls on nutrients across a prairie stream watershed Land use a636 -6460 v373 aNutrient inputs generally are increased by human-induced land use changes and can lead to eutrophication and impairment of surface waters. Understanding the scale at which land use influences nutrient loading is necessary for the development of management practices and policies that improve water quality. The authors assessed the relationships between land use and stream nutrients in a prairie watershed dominated by intermittent stream flow in the first-order higher elevation reaches. Total nitrogen, nitrate, and phosphorus concentrations were greater in tributaries occupying the lower portions of the watershed, closely mirroring the increased density of row crop agriculture from headwaters to lower-elevation alluvial areas. Land cover classified at three spatial scales in each sub-basin above sampling sites (riparian in the entire catchment, catchment land cover, and riparian across the 2 km upstream) was highly correlated with variation in both total nitrogen (r2 = 53%, 52%, and 49%, respectively) and nitrate (r2 = 69%, 65%, and 56%, respectively) concentrations among sites. However, phosphorus concentrations were not significantly associated with riparian or catchment land cover classes at any spatial scale. Separating land use from riparian cover in the entire watershed was difficult, but riparian cover was most closely correlated with in-stream nutrient concentrations. By controlling for land cover, a significant correlation of riparian cover for the 2 km above the sampling site with in-stream nutrient concentrations could be established. Surprisingly, land use in the entire watershed, including small intermittent streams, had a large influence on average downstream water quality although the headwater streams were not flowing for a substantial portion of the year. This suggests that nutrient criteria may not be met only by managing permanently flowing streams.10anitrogen10aPhosphorus10aPrairie watershed10aRiparian10awater quality1 aDodds, W., K.1 aOakes, R.M. uhttp://knz.lternet.edu/content/controls-nutrients-across-prairie-stream-watershed-land-use-and-riparian-cover-effects02309nas a2200253 4500008004100000245010500041210006900146300001300215490000700228520150300235653001501738653001301753653001401766653001101780653002301791653001401814653001801828100001801846700001701864700001701881700001601898700001901914856012201933 2004 eng d00aQuality and quantity of suspended particles in rivers: Continent-scale patterns in the United States0 aQuality and quantity of suspended particles in rivers Continents a355 -3670 v333 aSuspended solids or sediments can be pollutants in rivers, but they are also an important component of lotic food webs. Suspended sediment data for rivers were obtained from a United States–wide water quality database for 622 stations. Data for particulate nitrogen, suspended carbon, discharge, watershed area, land use, and population were also used. Stations were classified by United States Environmental Protection Agency ecoregions to assess relationships between terrestrial habitats and the quality and quantity of total suspended solids (TSS). Results indicate that nephelometric determinations of mean turbidity can be used to estimate mean suspended sediment values to within an order of magnitude (r2 = 0.89). Water quality is often considered impaired above 80 mg TSS L−1, and 35% of the stations examined during this study had mean values exceeding this level. Forested systems had substantially lower TSS and somewhat higher carbon-to-nitrogen ratios of suspended materials. The correlation between TSS and discharge was moderately well described by an exponential relationship, with the power of the exponent indicating potential acute sediment events in rivers. Mean sediment values and power of the exponent varied significantly with ecoregion, but TSS values were also influenced by land use practices and geomorphological characteristics. Results confirm that, based on current water quality standards, excessive suspended solids impair numerous rivers in the United States.10aEcoregions10aLand use10apollution10aSeston10aSuspended sediment10aTurbidity10awater quality1 aDodds, W., K.1 aGido, K., B.1 aWhiles, M.R.1 aFritz, K.M.1 aMatthews, W.J. uhttp://knz.lternet.edu/content/quality-and-quantity-suspended-particles-rivers-continent-scale-patterns-united-states02206nas a2200217 4500008004100000245008900041210006900130300001300199490000700212520150300219653001901722653001501741653002201756653001501778653001401793653001501807653002301822653001801845100001801863856010701881 2003 eng d00aThe role of periphyton in phosphorus retention in shallow freshwater aquatic systems0 arole of periphyton in phosphorus retention in shallow freshwater a830 -8490 v393 a

Eutrophication caused by phosphorus (P) leads to water quality problems in aquatic systems, particularly freshwaters, worldwide. Processing of nutrients in shallow habitats removes P from water naturally and periphyton influences P removal from the water column in flowing waters and wetlands. Periphyton plays several roles in removing P from the water column, including P uptake and deposition, filtering particulate P from the water, and attenuating flow, which decreases advective transport of particulate and dissolved P from sediments. Furthermore, periphyton photosynthesis locally increases pH by up to 1 unit, which can lead to increased precipitation of calcium phosphate, concurrent deposition of carbonate-phosphate complexes, and long-term burial of P. Actively photosynthesizing periphyton can cause super-saturated O2 concentrations near the sediment surface encouraging deposition of metal phosphates. However, anoxia associated with periphyton respiration at night may offset this effect. Linking the small-scale functional role of periphyton to ecosystem-level P retention will require more detailed studies in a variety of ecosystems or large mesocosms. A case study from the Everglades illustrates the importance of considering the role of periphyton in P removal from wetlands. In general, periphyton tends to increase P retention and deposition. In pilot-scale constructed periphyton-dominated wetlands in South Florida, about half of the inflowing total P was removed.

10aeutrophication10amicroalgae10amicrophytobenthos10aperiphyton10aphosphate10aPhosphorus10atertiary treatment10awater quality1 aDodds, W., K. uhttp://knz.lternet.edu/content/role-periphyton-phosphorus-retention-shallow-freshwater-aquatic-systems