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Red Deer River
Transcript of Red Deer River
Hypothesized mechanism: nutrient enrichment releases constraints on the growth of primary producers, which in turn raises local carrying capacity for aquatic insect larvae, allowing higher abundances OBJECTIVE #3 Estimate the net long term movement of insects OBJECTIVE #4 Assess whether movement affects the spatial response of insects to the RDWWTP
Is it necessary to consider insect movements to adequately understand/ predict large scale abundance patterns? However, the long-term net movement of insects is virtually unknown! SAMPLING METHODS Bio Sciences Sample Processing NO3 (μg/L) Average water velocity (m/s) Distance downstream of WWTP (km) Average substrate particle size
(modified Wentworth scale) Distance downstream of WWTP (km) Distance downstream of WWTP (km) Periphyton Chl a (g/cm2) Distance downstream of WWTP (km) Distance downstream of WWTP (km) LOESS REGRESSIONS Baetis mid instar larvae (No./sample) Distance downstream of WWTP (km) Hydropsyche late instar larvae (No./sample) Distance downstream of WWTP (km) GENERALIZED LINEAR MODELS WWTP-influenced variables:
NO3 concentration, Periphyton Chl a
Habitat / hydrological variables:
Substrate size, Flow velocity
+ 2-way interaction terms Poisson or negative binomial distribution
Log link function
Backwards elimination Total insect dry weight (g/m2) Total insect dry weight (g/m2) Baetis mid instar larvae (No./sample) Hydropsyche late instar larvae (No./sample) Distance downstream of WWTP (km) Distance downstream of WWTP (km) Distance downstream of WWTP (km) STABLE ISOTOPE ANALYSIS Wastewater effluent creates a natural marking experiment REANALYZING ENVIRONMENTAL PREDICTORS OF ABUNDANCE Using gradients in isotope signatures to infer movements FAMILY ASSEMBLAGE SPATIAL STRUCTURE Similarities in communities through space can provide clues about:
the scale of internal processes, such as movement, that affect distribution and abundance
how external forces drive distribution and abundance Spatial dependence on external linear gradient "Single bump" spatial structure (Legendre and Legendre 2012) Scaling population responses to spatial environmental variability in advection-dominated systems (Anderson et al. 2005) With independent variables averaged over various lags
and/or the inclusion of a spatial variance-covariance matrix A consideration of environmental conditions in areas larger than the site of sampling improves the prediction of abundance in some cases, and doesn't decrease fit in others From previous discussions... Input from the WWTP appears to affect large scale abundance patterns Mantel correlograms: depict spatial autocorrelation structure in multivariate data NO3 Stable isotope signatures suggest that downstream movement on the scale of a few km per month is probable, yet... Large scale spatial structure in family assemblages seems to be driven by large scale gradients in environmental factors rather than internal processes such as movement A large scale downstream lag in total abundance as compared to "potential primary productivity" is not evident Because downstream movement can effectively spread the numerical response of a population downstream from the conditions it is responding to Freshwater systems are increasingly impacted by the addition of nutrient rich effluent from WWTPs The effects of these inputs cascade through river ecosystems Sampled invertebrate and periphyton at 41 sites on the Red Deer River in August, 2010
Measured various physical and chemical parameters The response of insects to wastewater effluent in the Red Deer River:
A spatial perspective Madison Kobryn Linear trends (Non-parametric spline)
cross-correlation Residuals * ** ** * * * But local-scale analysis
did a good job explaining
local abundance Future Directions Finer-scale sampling Spatial variation in trophic fractionation Different resource pools Further