Periphyton biomass and ecological stoichiometry in streams within an urban to rural land-use gradient

Abstract

This study examined the effects land use on biomass and ecological stoichiometry of periphyton in 36 streams in southeastern New York State (USA). We quantified in-stream and land-use variables along a N-S land-use gradient at varying distances from New York City (NYC). Streams draining different landscapes had fundamentally different physical, chemical, and biological properties. Human population density significantly decreased (r = -0.739; P \ 0.00001), while % agricultural land significantly increased (r = 0.347; P = 0.0379) with northing. Turbidity, temperature, conductivity, and dissolved Mg, Ca, SRP, pH, DOC, and Si significantly increased in more urban locations, but NO 3 -and NH 4 ? did vary not significantly along the gradient. Periphyton biomass (as AFDM and Chl-a) in rural streams averaged one-third to one-fifth that measured in urban locations. Periphyton biomass in urban streams averaged 18.8 ± 6.0 g/m 2 AFDM and 75.6 ± 28.5 mg/m 2 Chl-a. Urban Chl-a levels ranging between 100 and 200 mg/m 2 , are comparable to quantities measured in polluted agricultural streams in other regions, but in our study area was not correlated with % agricultural land. Periphyton nutrient content also varied widely; algal C varied [20-fold (0.06-1.7 lmol/mm 2 ) while N and P content varied [6-fold among sites. Algal C, N, and P correlated negatively with distance from NYC, suggesting that periphyton in urban streams may provide greater nutrition for benthic consumers. C:N ratios averaged 7.6 among streams, with 91% very close to 7.5, a value suggested as the optimum for algal growth. In contrast, periphyton C:P ratios ranged from 122 to [700 (mean = 248, twice Redfield). Algal-P concentrations were significantly greater in urban streams, but data suggest algal growth was P-limited in most streams regardless of degree of urbanization. GIS models indicate that land-use effects did not easily fit into strict categories, but varied continuously from rural to urban conditions. We propose that the gradient approach is the most effective method to characterize the influence of land use and urbanization on periphyton and stream function.

The effect of periphyton stoichiometry and light on biological phosphorus immobilization and release in streams

“…For example, Little Wildcat Creek was initially expected to be more nutrient-rich than other streams due to the relatively dense pasture cover in its watershed and the proximity of pastures to the stream at the sampling location (Carpenter et al 1998). We expected landscape-scale controls of in-stream nutrient concentrations to create a more distinct pattern of periphyton stoichiometry across streams (Stelzer and Lamberti 2001;O'Brien and Wehr 2010). Only Mud Creek had statistically lower periphyton P than the other streams in the study, yet it recently served as a receiving stream for treated wastewater, which should lead to higher periphyton P. The Mud Creek tributary's watershed is highly urbanized, which can result in frequent flow disturbances that cause shear stress and scouring (Walsh et al 2005).…”

“…Streams and rivers not only act as conduits that transport nutrients, but also transform nutrients during their downstream transport from the continents to the ocean. Elemental ratios in periphyton can reflect the availability of nutrients in streams (Stelzer andLamberti 2001, O'Brien andWehr 2010). Several recent works have also focused on how stream nutrient enrichment and light availability can interact to influence periphyton chemical composition and stoichiometry (Fanta et al 2010, Hill et al 2011.…”

Understanding effects of global change on river ecosystems: science to support policy in a changing world

“…Direct effects on organisms are more likely transferable across ecoregions than indirect effects because of added interactive effects. The mechanistic responses to differing nutrient pollution that occur from microbes (Ziegler & Lyon, 2010) to invertebrates (Donato-Rondón et al, 2010) and fish (Miltner & Rankin, 1998;Wang et al, 2007) are similar among regions and are even expressed in the stoichiometric composition of the organisms (O'Brien & Wehr, 2010). Multiple investigations indicate direct effect of phosphorus on algal biomass is greatest when phosphorus concentrations are less than 30 lg TP l -1 (Bothwell, 1988;Dodds et al, 1997;Stevenson et al, 2008, submitted).…”

“…However, similarities in responses among river typologies are likely larger than differences, which may largely be associated with system sensitivity and magnitude of responses. Effects of urbanization and agricultural activity produce long-lasting effects in biodiversity and functioning elsewhere, from the tropical regions (Donato-Rondón et al, 2010) to flood plain rivers (Rodrigues Capítulo et al, 2010) and headwater streams (O'Brien & Wehr, 2010).…”

Assessment of the effectiveness of best management practices for streams draining agricultural landscapes using diatoms and macroinvertebrates

“…Temperature, dissolved oxygen, pH, and turbidity were measured in situ using a Hydrolab Quanta (Hach Industries, Loveland, CO). Water samples were collected for water chemistry analyses in three acid-washed 8-ml sample tubes, and filtered using a syringe filter (0.2-lm pore size), as used previously (O'Brien & Wehr, 2010). Samples were preserved with H 2 SO 4 to pH \2.0 (U.S.E.P.A., 1987) and stored cold (B4.0°C) until further analysis.…”