River health monitoring traditionally has made use of structural measurements (water quality or taxonomic composition of aquatic organisms). We argue that a more complete assessment of river health should include functional metrics, such as rates of organic matter decomposition and ecosystem metabolism. Leaf breakdown links the characteristics of riparian vegetation with the activity of both aquatic invertebrates and microbial organisms and is affected by natural and human-induced variation in a wide range of environmental factors. Measurement of leaf breakdown is relatively simple and has modest equipment requirements. River metabolism (gross primary productivity and ecosystem respiration) measures the rates of production and use of organic C in river ecosystems as a whole, providing a direct estimate of the food base that determines life-supporting capacity. Metabolism measurements require more sophisticated equipment than do measurements of leaf breakdown, but improvements in technology have made metabolism measurements relatively easy. We review the factors that influence leaf breakdown and river metabolism and pay particular attention to the effects of human-induced environmental stressors. We also describe how measurements can be standardized and suggest criteria for interpreting functional measures in terms of river ecosystem health. Last, we consider the strengths and weaknesses of both methods as functional measures and provide recommendations for their use as biomonitoring tools.

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Organic matter breakdown and ecosystem metabolism: functional indicators for assessing river ecosystem health

Comparative Animal Physiology By Prof. David W. Bishop, Prof. Frank A. Brown Jr., Prof. Theodore L. Jahn, Prof. C. Ladd Prosser and Prof. Verner J. Wulff. Prof. C. Ladd Prosser, Editor. Pp. ix + 888. (Philadelphia and London: W. B. Saunders Co., 1950.) 63s.

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Comparative Animal Physiology

SUMMARY 1. The Lotic Intersite Nitrogen eXperiment (LINX) was a coordinated study of the relationships between North American biomes and factors governing ammonium uptake in streams. Our objective was to relate inter-biome variability of ammonium uptake to physical, chemical and biological processes. 2. Data were collected from 11 streams ranging from arctic to tropical and from desert to rainforest. Measurements at each site included physical, hydraulic and chemical characteristics, biological parameters, whole-stream metabolism and ammonium uptake. Ammonium uptake was measured by injection of 15 N-ammonium and downstream measurements of 15 N-ammonium concentration. 3. We found no general, statistically significant relationships that explained the variability in ammonium uptake among sites. However, this approach does not account for the multiple mechanisms of ammonium uptake in streams. When we estimated biological demand for inorganic nitrogen based on our measurements of in-stream metabolism, we found good correspondence between calculated nitrogen demand and measured assimilative nitrogen uptake.

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Factors affecting ammonium uptake in streams – an inter‐biome perspective

Detailed studies of stream N uptake were conducted in a prairie reach and gallery forest reach of Kings Creek on the Konza Prairie Biological Station. Nutrient uptake rates were measured with multiple short-term enrichments of NO3 2 and NH4

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N uptake as a function of concentration in streams

We measured ecosystem metabolism and organic matter transport seasonally in five streams draining catchments dominated by native forest, exotic pine plantation, grazed tussock grassland, or developed pasture. All streams are tributaries of the Taieri River in southeastern New Zealand. Whole-stream metabolism was estimated by both two-station and single-station open-channel methods, allowing comparison between these techniques. Transfer of oxygen across the stream surface was estimated using reaeration coefficients determined from three different procedures: tracer gas injections (propane), analysis of the oxygen record, and empirical velocity–depth equations. Measurements of gross primary production (GPP) and community respiration (CR) showed differences among streams that reflected method rather than ecosystem process. The ratio of GPP:CR and net ecosystem metabolism, however, showed strong concordance among methods, suggesting that bias involved in standardizing estimates to areal units may be more impo...

Effects of land use on stream metabolism and organic matter turnover

Experiments were performed to compare 14 C uptake, dissolved O2 and CO2 change, and microelectrode techniques for measuring benthic primary productivity and community metabolism at a site on the South Saskatchewan River, Saskatchewan. The highest estimates of primary productivity were obtained with O2 microelectrodes (two to four times higher than simultaneous estimates from bulk-water dissolved O2 measurements), presumably because measurements are biased toward active communities under optimal conditions for photosynthesis. In daytime experiments lasting ~1.3 and 2.4 h, estimates from 14 C uptake were higher than those measured simultaneously from dissolved O2 and CO2 change, suggesting that 14 C uptake measured gross primary production (GPP) in these short-term incubations. Differences in experimental water velocity ranging from 0.2 to >6.5 cm·s n1 had less of an effect than chlorophyll a concentration on metabolic rates in diel experiments with rocks taken from a site where velocities were from 5.6 to 7.8 cm·s n1 . There was a potential for phosphorus and possibly NH4 limitation of metabolic activity during long-term incubations. Results highlight areas in which further research is needed when using chambers to determine periphyton metabolism. Resume : Nos expOriences visaient ‡ comparer liassimilation du 14 C, les changements dans liO2 dissous et le CO2 et les techniques faisant appel ‡ des microOlectrodes pour mesurer la productivitO primaire benthique et le mOtabolisme des

An evaluation of techniques for measuring periphyton metabolism in chambers

The effect of nutrient regime on periphyton community development in large rivers was examined (sites ranged from oligotrophic to eutrophic). Patterns in diatom community structure were examined at...

Regional patterns in periphyton accrual and diatom assemblage structure in a heterogeneous nutrient landscape

In running water ecosystems, the use of community attributes to infer biological integrity is widespread. In contrast, functional variables like energy flow and elemental cycling have received considerably less attention. In this study, we quantify organic carbon spiraling in four reaches of the Middle Snake River (MSR). We calculated organic carbon (OC) turnover rates (KOC), mean velocities (VOC), and turnover lengths (SOC) by quantifying suspended and benthic pools of organic carbon and measuring metabolic rates using both open-system and chamber approaches. Ultra-fine particulate organic carbon (UPOC) dominated both transported and benthic OC in all study reaches. KOC was lowest where benthic standing stocks were greatest and KOC was elevated in summer relative to spring and fall. VOC was negatively correlated with benthic OC standing stock and greatest in spring and early summer when river discharge was highest. Turnover lengths (SOC) ranged from 11–108 km and were strongly related to temporal patterns in VOC. Comparison of the Snake River with other river systems suggests that MSR is more retentive and homogeneous than rivers of similar size in North America.

Organic carbon spiraling in an Idaho river

Assessing the historic contribution of marine-derived nutrients to Idaho streams

An energy budget provides a useful tool for examining the exchange of energy between trophic levels. In this study we examined the potential for autotrophic productivity and organic material to support higher trophic levels in three distinct geomorphic segments of the Kootenai River, USA. This approach is particularly important given that several species of fish, including the endangered Kootenai white sturgeon (Acipenser transmontanus), have been in decline since the installation of a large hydropower and flood control dam on the river. Previous research indicated that (i) the reservoir formed by Libby Dam was retaining significant quantities of nutrients and organic material and (ii) phosphorus was limiting periphyton accrual downstream from the reservoir. Thus food limitation was a likely mechanism contributing to the decline in fish populations. Net daily metabolism (NDM) was positive during only 30% of the growing seasons from 1993 to 1995 indicating that autochthonous production was rarely sufficient to support higher trophic levels. All reaches were generally exporting transported organic matter (TOM). Results of an energy budget indicated that macroinvertebrate standing crop was generally lower than that which could be sustained by the relatively short bursts of positive NDM. Estimated fish biomass was higher than that sustained by positive NDM or stored TOM at energetic conversion efficiencies (C.E.) of 10% at average and maximum estimated active metabolic rate. Autotrophic and detrital sources were generally insufficient to support the estimated fish biomass. This study combines detailed analyses of both the autotrophic and detrital energy pathways and thereby suggests a mechanistic explanation for the decline in fish abundance ultimately caused by impoundment.

Eric B. Snyder

Papers

An evaluation of techniques for measuring periphyton metabolism in chambers

Regional patterns in periphyton accrual and diatom assemblage structure in a heterogeneous nutrient landscape

Organic carbon spiraling in an Idaho river

Assessing the historic contribution of marine-derived nutrients to Idaho streams

An energy budget for the Kootenai River, Idaho (USA), with application for management of the Kootenai white sturgeon, Acipenser transmontanus