Stream Food Research Articles

Myrica esculenta: potential wild resource needs conservation priority in Indian Himalayan Region

The western Himalaya is well known for rich and diverse natural bio-resources but many valuable resources are still unutilized. In order to utilize such natural resources particularly wild edibles, it is important that resources can be harnessed efficiently to meet the requirement of local peoples for their economic development with sustainable manner. Although, wild edible bioresources have been complementing the food security to traditional societies for centuries in the Himalayan region. Unfortunately these valuable wild edibles are not given much priority by main stream societies, scientists, policy makers and food & medicine processing industries. Increased interest in harnessing the potential of wild edibles is the result of growing knowledge about these and consequently shifts in development paradigms. Now wild bioresources are being viewed as untapped or less utilized resources that could play a significant role in the development of horticulture industries, livelihood option and nutritional security. Therefore, the policy makers and agencies working in the region are need to give proper consideration to the wild edible plants for their wide in-situ production and development through due emphasis on genetic improvement, mass scale propagation and plantation and awareness on proper utilization and sustainable harvesting.

Nutrient Limitation and Uptake Rates in Streams and Rivers of the Greater Yellowstone Ecosystem

Nutrient pollution of aquatic ecosystems is a growing concern as the influence of human activities continues to increase on the landscape. Headwater streams have long been shown to process nutrients via the biofilm community growing on the bottom of streams. The growth and activity of these biofilms is often limited by the availability of nitrogen (N), phosphorus (P), or co-limited by both N and P. Although small stream nutrient dynamics are relatively well understood, comparatively little is known about larger, non-wadeable rivers. Biofilms on the river bottom are likely still nutrient limited, but there becomes an increased potential for light limitation as rivers increase in depth. In addition to biofilms on the bottom of rivers, free-living microbial communities suspended in the water column also occur in rivers and process nutrients - a component of nutrient processing largely ignored in streams. In summer 2013 we worked in streams and rivers of the Greater Yellowstone Area (GYA) to establish the nutrient limitation status of minimally-impacted rivers, as well as the role of the water column in processing nutrients as streams increase in size. For both the nutrient limitation and water column uptake studies, we are using the GYA sites in addition to systems from other regions of the US to establish what controls the various aspects of nutrient dynamics in rivers. Our results from the GYA, in addition to Midwest and Southwest US rivers, will provide water quality managers with new strategies for improving water quality downstream, and clarify mechanisms controlling nutrient retention in rivers.

Stream Nutrient Criteria for Evaluating Water Eutrophication and Biota Conditions

Copyright: © 2013 Guo M. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Water flew vividly over stones in a wadablestream, singing and winding through mountains toward east. Small fishes swam in water pools enjoying the penetrating sunlight. Several turtles were getting sun on rocks along the banks. A mother crab and a school of baby crabs ran in panic after a random stone in the stream was turned over. This was a typical scene in China before 1980. Now turtles and crabs have disappeared from most streams, and fishes become scarce. The wide use of chemical fertilizers and pesticides in China’s agriculture since the beginning of 1980s has resulted in severe contamination of the natural water system, extinguishing many sensitive aquatic organisms. Synthetic fertilizers containing 29.5 million tons of N and 6.1 million tons of P were applied to China’s cropland in 2010, as compared with the 1980 level at 9.1 million tons of N and 1.2 million tons of P [1]. It was estimated that 6.8 and 0.41 million tons of N and P, respectively, were lost in from cropland to China’s surface water and groundwater via runoff, leaching, and soil erosion in 2010 [1]. Counting other nutrient sources in the food chain (e.g., livestock, household, and food processing), in 2010 China’s freshwater system received in total 15.2 and 2.8 million tons of N and P, respectively [1].

A MODIS approach to predicting stream water quality in Wisconsin

Efforts to predict water quality often rely heavily on static landuse/land-cover (LULC) classifications derived from remote sensing imagery. However, LULC classifications are infrequently updated, and the development of regular (annual) land cover maps that accurately capture intra- and inter-annual change may be expensive in terms of data and labor costs. In addition, existing land cover products may not include classes relevant to the assessment of water quality. Conversely, data from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments are freely available, preprocessed, frequently updated, and available in a range of useful data products. Our goal was to predict water quality for streams in Wisconsin, USA using a model constructed exclusively from MODIS products. We used streamwater nitrate and dissolved phosphorus data from 2001 to 2004 from two previous studies (Robertson et al., 2006; Stanley & Maxted, 2008) to evaluate the potential for using MODIS in an empirical model to predict water quality, thereby reducing reliance on possibly dated land cover maps. Using predictors derived exclusively from MODIS data products, we successfully predicted 80% of the variation in measured nitrate concentrations. Remote sensing based models explained 51% of the variation in dissolved phosphorus concentrations. Predictions of water quality were developed on both a per-pixel and a watershed basis. The remote sensing approach offers the potential for spatially continuous estimates of stream nutrient concentrations, and complements the suite of approaches currently used to assess water quality; including periodic stream surveys models, and point-source data.

Symposium 17. Ecosystem Capacity for Sustaining Long-term Water Supplies

Symposium 17. Ecosystem Capacity for Sustaining Long-term Water Supplies

Positive effect of shredders on microbial biomass and decomposition in stream microcosms

Summary1. Animals play a major role in nutrient cycling via excretory processes. Although the positive indirect effects of grazers on periphytic algae are well understood, little is known about top‐down effects on decomposers of shredders living on leaf litter.2. Nutrient cycling by shredders in oligotrophic forest streams may be important for the microbial‐detritus compartment at very small spatial scales (i.e. within the leaf packs in which shredders feed). We hypothesised that insect excretion may cause local nutrient enrichment, so that microorganism growth on leaves is stimulated.3. We first tested the effect of increasing concentration of ammonium (+10, +20 and +40 μg NH4+ L−1) on fungal and bacterial biomass on leaf litter in a laboratory experiment. Then we performed two experiments to test the effect of the presence and feeding activity of shredder larvae. We used two species belonging to the trichopteran family Sericostomatidae: the Palaearctic Sericostoma vittatum and the Neotropical Myothrichia murina, to test the effect of these shredders on fungal and bacterial biomass and decomposition on leaves of Quercus robur and Nothofagus pumilio, respectively. All experiments were run in water with low ammonium concentrations (2.4 ± 0.34 to 14.47 ± 0.95 μg NH4+ L−1).4. After 5 days of incubation, NH4 concentrations were reduced to near‐ambient streamwater concentrations in all treatments with leaves. Fungal biomass was positively affected by increased ammonium concentration. On the other hand, bacteria abundance was similar in all treatments, both in terms of abundance (bacteria cells mg−1 leaf DW) and biomass. However, there was a tendency towards larger mean cell size in treatments with 20 μg NH4 L−1.5. In the experiment with S. vittatum, fungal biomass in the treatment with insects was more than twice that in the control after 15 days. Bacteria were not detected in treatments with insects, where hyphae were abundant, but they were abundant in treatments without larvae. In the decomposition experiment run with M. murina, leaf‐mass loss was significantly higher in treatments with larvae than in controls.6. Our hypothesis of a positive effect of shredders on fungal biomass and decomposition was demonstrated. Insect excretion caused ammonium concentration to increase in the microcosms, contributing to microbial N uptake in leaf substrata, which resulted in structural and functional changes in community attributes. The positive effect of detritivores on microbes has been mostly neglected in stream nutrient‐cycling models; our findings suggest that this phenomenon may be of greater importance than expected in stream nutrient budgets.

Linkages Between Riparian Characteristics, Ungulate Grazing, and Geomorphology and Nutrient Cycling in Montane Grassland Streams

Abstract Catchment characteristics and disturbances control the conditions and processes found in stream ecosystems. We examined nutrient cycling linkages between riparian soils and adjacent streams and the impacts of the removal of ungulate grazing on these ecosystems and processes at six grazing exclosure sites in the Valles Caldera National Preserve, NM, USA. The exclusion of native and domestic ungulate grazers for 3 yr significantly increased the riparian aboveground biomass of standing vegetation (273 ± 155 in grazed vs. 400 ± 178 g . m -2 in exclosures) and litter (58 ± 75 in grazed vs. 110 ± 76 g . m -2 in exclosures) ( P = 0.003 and 0.006, respectively). Except for an increase in total soil phosphorous (P) at three of the six sites, soil nutrient values were minimally affected by grazing after five growing seasons. Within the six sites studied, no connection was found between 0–15-cm depth soils, which were P-limited based on stoichiometric ratios, and stream nutrient availability or limitation, which were nitrogen limited. Stream geomorphology was not significantly altered by 5 yr of grazing exclusion. The elimination of grazing suppressed instream nutrient processing with significantly longer NH 4 uptake lengths ( P = 0.003). These results suggest the exclusion of ungulate grazing impacts terrestrial characteristics (increased standing vegetative biomass) that are linked to ecosystem services provided by adjacent aquatic ecosystems (reduced N-uptake). Management plans should carefully balance the positive effect of grazing on stream nutrient processing and retention reported here with the well-documented grazing-related loss of other ecosystem services such as decreased fish and aquatic invertebrate habitat and effects on water-quality parameters such as turbidity and water temperature.

Elevated Nitrogen and Phosphorus Concentrations in Urbanizing Southwest Washington Streams

In southwest Washington, rapid population growth and associated land use change have resulted in elevated stream nutrient concentrations. To evaluate the extent and nature of human alterations to stream nutrient concentrations in this region, we compiled four water years of total phosphorus (TP) and dissolved inorganic nitrogen (DIN) data from two long-term monitoring programs. We also quantified watershed characteristics likely to affect aquatic nutrient loading, and tested for correlations between these characteristics and stream nutrient concentrations. Average nutrient concentrations in study streams were significantly elevated relative to EPA recommended nutrient criteria in all sites for DIN and in nine out of 14 sites for TP. Of the watershed characteristics investigated, percent “impervious” ( ) and percent “forested” (-) were the best predictors of TP concentration (R2 = 0.41 and 0.64, respectively, and — indicate the slope of the regression). Percent “developed” ( ) and percent “forest and woody wetland” (-) were the best predictors of DIN concentration (R2 = 0.75 and 0.73, respectively). In urban streams, the mean dry season DIN concentration was significantly higher than the mean wet season DIN concentration, but this pattern was reversed in less urban watersheds. Urban streams also had significantly higher DIN than non-urban streams. The strong relationship between DIN and “developed land” suggests that as southwest Washington's population continues to grow, targeted N management will become increasingly important. The strong negative relationship between “forest and woody wetland” and both TP and DIN concentration suggests that this land use type is particularly important in reducing stream nutrient loading.

Fish-mediated nutrient cycling and benthic microbial processes: can consumers influence stream nutrient cycling at multiple spatial scales?

Fish-mediated nutrient recycling influences nutrient dynamics in stream ecosystems, but its consequences for smaller-scale microbial processes in benthic habitats are not well understood. We quantified the effect of nutrient recycling by the grazing fish, Campostoma anomalum, on downstream periphyton in 12 flow-through stream mesocosms. We compared periphyton nutrient ratios and algal biomass (as chlorophyll a [chl a]) between tiles upstream and downstream of enclosures with and without fish to measure nutrient-cycling effects in streams with low (11) and high (177) surface-water dissolved N∶P molar ratios. No upstream–downstream changes in periphyton nutrient ratios were observed in low N∶P streams with or without fish. In high N∶P streams, periphyton C∶N decreased and C∶P and N∶P increased on tiles downstream of enclosures. In high N∶P streams, downstream changes in periphyton nutrient ratios were greater in streams with than without fish, and chl a significantly increased downstream of enclosures with fish. We linked nutrient-recycling effects to downstream microbial processes by comparing bacterial biomass production (BBP), photosynthesis (PS) rates, and the degree of coupling between the 2 processes on tiles downstream of enclosures. We estimated the degree of coupled production between algae and bacteria downstream of enclosures as the covariance between PS and BBP among replicates within each stream (COVPS–BBP). In high N∶P streams, areal BBP and PS rates and COVPS–BBP were higher downstream of enclosures with fish. Chl a and COVPS–BBP declined with increasing periphyton C∶N content, resulting in a positive relationship between COVPS–BBP and algal biomass across all treatments. Our results indicate that grazing fish alter stream ecosystem N and P dynamics through consumer-mediated recycling pathways, but downstream responses depend on background nutrient regimes. Fish-mediated changes in nutrient dynamics and algal biomass influence reliance of heterotrophs and autotrophs on nutrients recycled within periphyton communities to support benthic production.

Quantifying Salmon‐Derived Nutrient Loads from the Mortality of Hatchery‐Origin Juvenile Chinook Salmon in the Snake River Basin

AbstractHatchery supplementation of anadromous salmon is extensive across the Pacific Northwest region with millions of juvenile salmon stocked annually. The influence of hatchery‐origin fish as prey items in recipient ecosystems has been explored, but influences of these fish on broader stream nutrient dynamics has not been well‐studied. Salmon‐derived nutrients (SDN) associated with the mortality of adult anadromous salmon provide key subsidies to freshwater habitats. While a number of studies have estimated current and historic SDN loading from returning wild salmon, SDN contributions from the mortality of hatchery‐origin juveniles (many of which die in the stream prior to emigration) remains largely unknown. We conducted a mass balance analysis of SDN input and export via hatchery activities (stocking and broodstock collection) in the Snake River watershed. Using Chinook salmon Oncorhynchus tshawytscha as a model species, we accounted for yearly SDN input (via hatchery‐origin juvenile fish mortality) and export (via broodstock collections and presmolt growth) over 6 years (2002–2007) in the portion of the Snake River upstream from Lower Granite Dam accessible to anadromous fish. In the year with highest smolt mortality (2003), hatchery‐origin smolt mortality provided a net input of SDN equivalent to approximately 8,100 returning adults. In the year with lowest smolt mortality (2004), hatchery activities collectively yielded a net loss of nutrients. Although the mass of SDN from hatchery‐origin smolts may be presented in adult equivalencies, functional influences of SDN from hatchery smolt mortality are likely to differ. Salmon‐derived nutrients from hatcheries enter food webs through largely piscivorous pathways whereas SDN from adult carcasses enter food webs through multiple pathways at multiple trophic levels. The SDN from hatchery‐origin smolts probably influence different components of the food web more than do adult carcasses and have the potential to more directly affect predator populations.

Hydrological extremes modulate nutrient dynamics in mediterranean climate streams across different spatial scales

Hydrology is a key factor in the terrestrial landscape that connects upland and riparian ecosystems to streams. Hydrological connectivity through the catchment and along the stream network influences not only the timing and the magnitude of terrestrial inputs to stream ecosystems, but also regulates stream metabolism and biogeochemical cycling. In mediterranean climate regions (med-regions), there is a marked seasonal alternation of dry and wet periods, and streams experience a wide range of hydrological conditions from floods to droughts. Moreover, nutrient dynamics in med-streams are highly variable within the year and between years compared to temperate streams. In this review, we explore how seasonal changes in hydrological connectivity and hydrological extremes affect nutrient cycling and transport at different spatial scales in med-catchments. We show that during the dry period, the stream network contracts more severely in med-catchments than in temperate catchments. During the contraction phase, upland-stream disconnection decreases nutrient supply from terrestrial ecosystems, while stream fragmentation increases the spatial variation of stream nutrient concentrations. Moreover, the precipitation regime typical of med-regions (with irregular distribution of precipitation and episodic large rainfall events) decreases the ability of terrestrial and aquatic biota to retain nutrients and favours nutrient export to downstream ecosystems. Altogether, this hydrological setting confers to med-streams a characteristic temporal pattern in stream nutrient dynamics that is analogous to a particular biogeochemical heartbeat with higher amplitude, variation and unpredictability than that observed in temperate streams.

The invasion of the freshwater diatom Didymosphenia geminata in Patagonia: prospects, strategies, and implications for biosecurity of invasive microorganisms in continental waters

AbstractThe diatom Didymosphenia geminata, which forms nuisance blooms in low nutrient streams worldwide, was documented as an aggressive invader in South America in 2010 from the Futaleufú basin (43.2°S), in Chilean and Argentinean Patagonia. Within 1 year it was confirmed from 20 rivers distributed over 800 km. Driven by perceived economic impacts to tourism and recreation, a strong response ensued, with education, monitoring and nascent biosecurity efforts based on similar measures in New Zealand. Considering the difficulty in containment (potential range on New Zealand's South Island was occupied by D. geminata within 3 years), the much larger potential range, and limited resources or previous experience in managing invaders in continental waters in South America, it is unlikely that current biosecurity measures will produce significant results. Lacking a coordinated strategic approach or conservation priorities, existing efforts may divert resources from alternatives with greater potential for success, while potentially feeding the public perception that the problem is being addressed. We propose a conservation strategy based on best available but incomplete information on habitat requirements, and a conceptual model of invasion vectors to identify defensible conservation zones (islands and hydrographically isolated areas) with greater potential for being maintained invasion‐free.

Stream water quality in intensive cereal cropping catchments with regulated nutrient management

Regulating farm nutrient management is a European Union policy approach to meet water quality targets. In two intensively cropped catchments (9km2 and 11km2) in Ireland, high resolution monitoring was undertaken over two years to investigate interactions between the regulations and nutrients in streams. In a catchment with predominantly well-drained soils (Arable A) farmed for spring barley, high phosphorus (P) concentrations and turbidity during peak river flows indicated high connectivity of nutrient sources with streams. High baseflow volumes, however, maintained mean stream P concentrations below the environmental quality standard (EQS). Total oxidised nitrogen (TON) concentrations decreased during storms and baseflow concentrations remained relatively stable and below drinking water standards. In a contrasting catchment on moderate to poorly drained soils (Arable B) farmed for winter wheat, dairy and beef, the EQS for P was never met. High baseflow P concentrations during summer were attributed largely to loss of dilution in low discharge rates. Spatial surveys of water quality indicated baseflow P concentrations were influenced by persistent point sources. Baseflow TON concentrations were lower during summer than winter and this was attributed to seasonal disconnection and attenuation of N sources. Average annual streamflow total P loads were higher from Arable B (0.72kgha-1) than from Arable A (0.27kgha-1) whereas TON loads were higher from Arable A (28kgha-1) than from Arable B (17kgha-1). Suspended sediment losses, after a first approximation, were less than 0.18tha-1yr-1. The upper quartile of stream discharge dominated annual loads of P, TON and suspended sediments. Of most concern were stream P concentrations in Arable B and potentially P and N loads from both catchments given both catchments contribute to eutrophic coastal waters. Compliance with farm nutrient management regulations should mitigate persistent agricultural point sources but will not affect non-agricultural point source influences on stream P concentrations. Under current regulations, decreased N surplus at source and subsequent depletion of nitrate from vadose and groundwater stores may decrease TON loads over time.

Importance ofTerrestrialArthropods asSubsidies inLowlandNeotropicalRainForestStreamEcosystems

AbstractThe importance of terrestrial arthropods has been documented in temperate stream ecosystems, but little is known about the magnitude of these inputs in tropical streams. Terrestrial arthropods falling from the canopy of tropical forests may be an important subsidy to tropical stream food webs and could also represent an important flux of nitrogen (N) and phosphorus (P) in nutrient‐poor headwater streams. We quantified input rates of terrestrial insects in eight streams draining lowland tropical wet forest inCostaRica. In two focal headwater streams, we also measured capture efficiency by the fish assemblage and quantified terrestrially derivedN‐ andP‐excretion relative to stream nutrient uptake rates. Average input rates of terrestrial insects ranged from 5 to 41 mg dry mass/m2/d, exceeding previous measurements of aquatic invertebrate secondary production in these study streams, and were relatively consistent year‐round, in contrast to values reported in temperate streams. Terrestrial insects accounted for half of the diet of the dominant fish species,Priapicthys annectens. Although terrestrially derived fish excretion was found to be a small flux relative to measured nutrient uptake rates in the focal streams, the efficient capture and processing of terrestrial arthropods by fish made these nutrients available to the local stream ecosystem. This aquatic‐terrestrial linkage is likely being decoupled by deforestation in many tropical regions, with largely unknown but potentially important ecological consequences.

Cycling of two carbon substrates of contrasting lability by heterotrophic biofilms across a nutrient gradient of headwater streams

Anthropogenic impacts can significantly alter stream nutrient and dissolved organic carbon (DOC) delivery and composition. Nutrient and DOC cycling in headwater streams, however, are linked via a variety of complex feedbacks that are, in part, influenced by DOC composition emphasizing the need to investigate coupled nutrient–DOC interactions. This study assessed differential incorporation and mineralization of 13C labeled glucose and vanillin by heterotrophic microbes within epilithic biofilm communities in four temperate headwater streams spanning a 100-fold range in total dissolved nitrogen and soluble reactive phosphorous concentrations. The substrates were traced via 13C analyses of DOC, dissolved inorganic carbon, bulk biofilm, and individual biofilm phospholipid fatty acids (PLFA) to assess total incorporation of the substrates and the distribution of substrate use within the heterotrophic community. Results indicate greater nutrient uptake by high nutrient streams with glucose additions relative to vanillin additions and support the hypothesis that nutrient retention in high nutrient streams is hampered by a lack of labile C sources. Vanillin-derived C uptake was only detectable in PLFA from the highest nutrient stream and was dominated by eukaryotic organisms, likely including fungi. This suggests biofilms in high nutrient streams are better adapted to access relatively slow turnover substrates perhaps due to their composition and overall structure. PLFA-based glucose use efficiencies were greatest in the lowest nutrient stream supporting the hypothesis that labile DOC sources are used more efficiently by heterotrophs in less impacted streams, while biofilms of high nutrient streams are better adapted to utilizing a wider array of DOC sources. This adaption is likely a result of exposure to the lower quality DOC pools in high-nutrient streams resulting from high DOC uptake supported, in part, by fast turnover autochthonous sources of DOC. Nutrient retention in nutrient-rich streams, however, is still likely limited by readily bioavailable DOC leading to lower nutrient retention and downstream nutrient enrichment.

Estimating reference nutrient criteria for Maryland ecoregions

Management of stream nutrients is becoming increasingly important in order to protect both water quality and aquatic resources throughout the USA. Using an extensive water quality database from the long-term Maryland Biological Stream Survey (MBSS), we describe nutrient relationships to landscape characteristics as total nitrogen (TN) and total phosphorus (TP) of small-order, non-tidal streams in USEPA L2 and L3 ecoregions in Maryland and by MBSS stream order at the L2 and L3 ecoregion levels. To protect stream ecosystem integrity, preliminary reference nutrient estimates (TN and TP) as percentiles (25th of all stream reaches and 75th of stream reference reaches) for the six Maryland L3 ecoregions are: Blue Ridge TN 0.29 and 0.64mg/L, TP 0.0065 and 0.0090mg/L; Central Appalachians TN 0.40 and 1.0mg/L, TP 0.0060 and 0.015mg/L; Middle Atlantic Coastal Plains TN 0.93 and 2.5mg/L, TP 0.094 and 0.065mg/L; Northern Piedmont TN 1.6 and 1.8mg/L, TP 0.010 and 0.015mg/L; Ridge and Valley TN 0.40 and 0.98mg/L, TP 0.0063 and 0.012mg/L; and Southeastern Plains TN 0.33 and 0.82mg/L, TP 0.016 and 0.042mg/L. High levels of both TN and TP are present in many streams found in non-tidal watersheds associated with all Maryland ecoregions, but are especially elevated in the Northern Piedmont and Middle Atlantic Coastal Plain ecoregions, with the latter second-order streams (average TN > 2.9mg/L) significantly higher than all other ecoregion-order combinations. Across all six ecoregions, mean nutrient loading for both TN and TP was generally equivalent in first-order streams to nutrient concentrations seen in both second- and third-order streams, indicating a definite need to increase efforts in preventing nutrients from entering first-order streams. Small-order stream nutrient levels are the drivers for subsequent TN and TP inputs into the upper freshwater tidal reaches of the Chesapeake Bay, resulting in a potential risk for altered estuarine ecosystems.

Temporal variability in the diversity and composition of stream bacterioplankton communities

Bacterioplankton in freshwater streams play a critical role in stream nutrient cycling. Despite their ecological importance, the temporal variability in the structure of stream bacterioplankton communities remains understudied. We investigated the composition and temporal variability of stream bacterial communities and the influence of physicochemical parameters on these communities. We used barcoded pyrosequencing to survey bacterial communities in 107 streamwater samples collected from four locations in the Colorado Rocky Mountains from September 2008 to November 2009. The four sampled locations harboured distinct communities yet, at each sampling location, there was pronounced temporal variability in both community composition and alpha diversity levels. These temporal shifts in bacterioplankton community structure were not seasonal; rather, their diversity and composition appeared to be driven by intermittent changes in various streamwater biogeochemical conditions. Bacterial communities varied independently of time, as indicated by the observation that communities in samples collected close together in time were no more similar than those collected months apart. The temporal turnover in community composition was higher than observed in most previously studied microbial, plant or animal communities, highlighting the importance of stochastic processes and disturbance events in structuring these communities over time. Detailed temporal sampling is important if the objective is to monitor microbial community dynamics in pulsed ecosystems like streams.

Aquatic and terrestrial organic matter in the diet of stream consumers: implications for mercury bioaccumulation

The relative contribution of aquatic vs. terrestrial organic matter to the diet of consumers in fluvial environments and its effects on bioaccumulation of contaminants such as mercury (Hg) remain poorly understood. We used stable isotopes of carbon and nitrogen in a gradient approach (consumer isotope ratio vs. periphyton isotope ratio) across temperate streams that range in their pH to assess consumer reliance on aquatic (periphyton) vs. terrestrial (riparian vegetation) organic matter, and whether Hg concentrations in fish and their prey were related to these energy sources. Taxa varied in their use of the two sources, with grazing mayflies (Heptageniidae), predatory stoneflies (Perlidae), one species of water strider (Metrobates hesperius), and the fish blacknose dace (Rhinichthys atratulus) showing strong connections to aquatic sources, while Aquarius remigis water striders and brook trout (Salvelinus fontinalis) showed a weak link to in-stream production. The aquatic food source for consumers, periphyton, had higher Hg concentrations in low-pH waters, and pH was a much better predictor of Hg in predatory invertebrates that relied mainly on this food source vs. those that used terrestrial C. These findings suggest that stream biota relying mainly on dietary inputs from the riparian zone will be partially insulated from the effects of water chemistry on Hg availability. This has implications for the development of a whole-system understanding of nutrient and material cycling in streams, the choice of taxa in contaminant monitoring studies, and in understanding the fate of Hg in stream food webs.

Freshwater algal cultivation with animal waste for nutrient removal and biomass production

Abstract Excess nutrients, particularly nitrogen and phosphorus remaining in anaerobically digested liquid manure (AD) effluent, have major impacts on the environment if disposed of inappropriately. Algal cultivation, with the advantage of a faster uptake of nutrients in effluent streams, represents one of the best processes for the removal of excessive nutrients. Meanwhile, algae have also been proved as one of the most promising non-food-crop-based feedstock for biofuels production. This study applying ecological approach on an open algal cultivation system elucidated that non-filamentous green algae, especially Chlorella, were able to tolerate high nutrient loadings in a five-month cultivation; a chemically pretreated AD effluent which contained 200 g m−3 of total nitrogen and 2.5 g m−3 of total dissolved phosphorus (TDP) provided an optimal nutrient concentration for the cultivation of selected algae. Additionally, the cultivation of selected algae with optimal pretreated AD effluent in a pilot-scale semi-continuously fed raceway pond revealed a stable algal biomass productivity of 6.83 g m−2 d−1.

Estimation of Phosphorus Bioavailability in the Water Column of the Bronx River, New York

Phosphorus (P) is a primary limiting nutrient in rivers and streams, and excessive P results in eutrophication of freshwater systems, in turn, excessive algal growth/toxic algal blooms, oxygen depletion, and water quality degradation. This study analyzed P pool, and hydrolysis of organic P (OP) by native phosphatases (NPase) in the water samples collected in the Bronx River. The soluble reactive P (SRP) of most of the sites’ water collected in 2006 and 2007 were higher (average 67 μg?L–1 and 68 μg?L–1, respectively) than the US Environmental Protection Agency’s (EPA) standard of 15 μg?L–1. The SRP% (SRP/TP%) average was 27% in 2006, much lower than in 2007 of SRP% average 83%. The OP% (OP/TP%) average was 73% in 2006, which was much higher than the OP% in 2007 (which was only 17%). The SRP concentrations and distributions (%), and the total P (TP) concentrations were in substantial amounts compared with other rivers. The NPase hydrolyzed OP % was up to 100% in 2006 and 2007 water samples. The average of NPase% was 59% in 2006 and 73% in 2007. The NPase average concentrations were 348 μg?L–1 in 2006, and 175 μg?L–1 in 2007. The NPase hydrolyzed up to 100% of OP% in the Bronx River water samples at 37?C, indicating a potential threat of eutrophication of freshwater systems as the global rise in temperature may continue to occur.