Impacts of land use at the catchment scale constrain the habitat benefits of stream riparian buffers

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Distribution of benthic diatoms in U.S. rivers in relation to conductivity and ionic composition

• 1 We quantified the relationships between diatom relative abundance and water conductivity and ionic composition, using a dataset of 3239 benthic diatom samples collected from 1109 river sites throughout the U.S.A. [U.S. Geological Survey National Water‐Quality Assessment (NAWQA) Program dataset]. This dataset provided a unique opportunity to explore the autecology of freshwater diatoms over a broad range of environmental conditions.
• 2 Conductivity ranged from 10 to 14 500 μS cm^?1, but most of the rivers had moderate conductivity (interquartile range 180–618 μS cm^?1). Calcium and bicarbonate were the dominant ions. Ionic composition, however, varied greatly because of the influence of natural and anthropogenic factors.
• 3 Canonical correspondence analysis (CCA) and Monte Carlo permutation tests showed that conductivity and abundances of major ions (HCO + CO, Cl^?, SO, Ca²⁺, Mg²⁺, Na⁺, K⁺) all explained a statistically significant amount of the variation in assemblage composition of benthic diatoms. Concentrations of HCO + CO and Ca²⁺ were the most significant sources of environmental variance.
• 4 The CCA showed that the gradient of ionic composition explaining most variation in diatom assemblage structure ranged from waters dominated by Ca²⁺ and HCO + CO to waters with higher proportions of Na⁺, K⁺, and Cl^?. The CCA also revealed that the distributions of some diatoms correlated strongly with proportions of individual cations and anions, and with the ratio of monovalent to divalent cations.
• 5 We present species indicator values (optima) for conductivity, major ions and proportions of those ions. We also identify diatom taxa characteristic of specific major‐ion chemistries. These species optima may be useful in future interpretations of diatom ecology and as indicator values in water‐quality assessment.

     

Contrasting effects of nutrients and climate on algal communities in two lakes in the Windermere catchment since the late 19th century

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Burial rates and stoichiometry of sedimentary carbon,nitrogen and phosphorus in Midwestern US reservoirs

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Are geothermal streams important sites of nutrient uptake in an agricultural and urbanising landscape (Rotorua,New Zealand)?

1. Lakes in the Rotorua region of New Zealand are affected by eutrophication from urbanisation and agricultural land use. Some lake tributaries contain geothermally influenced waters, and it is currently unknown whether geothermal tributaries are active sites of nutrient cycling or represent point sources of nutrients to the lakes. 2. Using government data sets, we characterised the physicochemical conditions of geothermal and non‐geothermal streams. We then measured ecosystem metabolism and reach‐scale uptake of nitrate (), ammonium () and phosphate () in summer 2010 (n = 8 streams). Finally, we used government data to compare annual nutrient flux from geothermal and non‐geothermal surface water inputs to Lake Rotoiti. 3. As expected, geothermal streams had higher temperature, conductivity and nutrient concentrations and lower pH. However, primary production, community respiration and uptake rates in geothermal streams were not different from those in their non‐geothermal counterparts. Uptake rates of were higher in geothermal streams, and uptake was below detection in geothermal streams, probably due to the saturation by naturally high concentrations. 4. A comparison of Lake Rotoiti inputs suggested that geothermal streams are not significant sources of and , while geothermal inputs of represent an average of 46% of total flux from Lake Rotoiti tributaries. 5. Despite their high temperature and low pH, geothermal streams are active sites of photosynthesis, respiration and and cycling, indicating dynamic biofilm communities. 6. Management options for geothermal streams, if any, should focus on retention (e.g. uptake or coupled nitrification and denitrification) but could prove challenging given the persistent, naturally occurring high flux.     

Importance of scale,land‐use,and stream network properties for riparian plant communities along an urban gradient

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Context dependency in biodiversity patterns of central German stream metacommunities

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Pink salmon productivity is driven by catchment hydrogeomorphology and can decline under a changing climate

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Relationships between nutrient enrichment,pleurocerid snail density and trematode infection rate in streams

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High resolution land cover data improve understanding of mechanistic linkages with stream integrity

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Effects of moderate ammonium enrichment on three submersed macrophytes under contrasting light availability

1. Increased ammonium concentrations and decreased light availability in a water column have been reported to adversely affect submersed vegetation in eutrophic waters worldwide. 2. We studied the chronic effects of moderate enrichment (NH₄–N: 0.16–0.25 mg L^?1) on the growth and carbon and nitrogen metabolism of three macrophytes (Ceratophyllum demersum, Myriophyllum spicatum and Vallisneria natans) under contrasting light availability in a 2‐month experiment. 3. The enrichment greatly increased the contents of free amino acids and nitrogen in the shoot / leaf of the macrophytes. This indicates that was the dominant N source for the macrophytes. 4. Soluble carbohydrate contents remained relatively stable in the shoot / leaf of the macrophytes irrespective of the treatments. Under ambient light, the starch contents in the shoot / leaf of C. demersum and M. spicatum increased with enrichment, whereas V. natans did not exhibit any change. The starch contents decreased in C. demersum, increased in M. spicatum and remained unchanged in V. natans after the combined treatment of enrichment and reduced light. 5. The enrichment did not affect the growth of the three macrophytes under the ambient light. However, it did suppress the growth of C. demersum and M. spicatum under the reduced light. The results indicate that a moderate enrichment was not directly toxic to the macrophytes although it might change their viability in eutrophic lakes in terms of the carbon and nitrogen metabolism.     

The late summer crustacean zooplankton in western U.S.A reservoirs reflects ecoregion,temperature and latitude

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Landscape variables influence taxonomic and trait composition of insect assemblages in Neotropical savanna streams

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Modelling and mapping the distribution,diversity and abundance of freshwater mussels (Family Unionidae) in wadeable streams of Illinois,U.S.A.

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Macroinvertebrate communities in streams in the Himalaya, Nepal

• 1 Macroinvertebrates were sampled in the riffles of fifty-eight streams from three regions of the Himalaya (Anapurna, Langtang and Everest) in Nepal. A semi-quantitative method with identification to family level was used to describe communities on-site.
• 2 Stream physicochemistry was assessed and the community structure of macroinvertebrates was related to chemistry, physiography (substratum composition, altitude and size), geographical location and the dominant land use in each catchment (terraced agriculture, forest or scrub). Community data were analysed by ordination (DECORANA) and classification (TWINSPAN).
• 3 The concentration of cations in stream water decreased significantly with altitude. Chemistry also differed between regions; sites from Anapurna had a higher pH and conductivity than those in the other two areas.
• 4 Communities were dominated by aquatic insect larvae, with Ephemeroptera, in particular the Baetidae, most numerous across sites.
• 5 There were, nevertheless, differences in community structure between sites, which were related closely to stream physicochemistry. Ordination scores were strongly correlated with altitude, magnesium concentration and substratum composition. Classification was also linked to altitude and chemistry, differentiating high-altitude sites with low silica concentrations from others. Sites from the Anapurna and Everest regions, with their contrasting chemistry, were also separated.
• 6 Community structure was also related to land use: streams draining catchments dominated by terraced agriculture had different communities from those in scrub or forest. This result was confounded, however, by the strong relationship between land use, altitude and chemistry; sites in terracing were at lower altitude, had higher concentrations of silica and a higher proportion of fine sediments than those in the other land-use types.
• 7 Overall, our data indicate that natural features of the relief and geology in the Himalaya create strong gradients in their invertebrate faunas, but that activities of man may have an effect on stream structure and ecology through catchment management.

     

Suspended-sediment responses after strip thinning in headwater catchments

We examined changes in suspended-sediment yields (SSY) after a 50 % strip thinning in headwater streams draining a Japanese cedar (Cryptomeria japonica) and cypress (Chamaecyparis obtusa) plantation forest. We applied a paired-catchment analysis to treated (K _T : 17.1 ha) and control (K _C : 8.9 ha) catchments. Annual suspended-sediment yield (SSY_an) in the prethinning period in the K _T and K _C catchments was 110.0 and 142.1 kg/ha per year. For the postthinning period, SSY_an in the K _T catchment became 5055.6 kg/ha per year, whereas that in the K _C catchment increased 893.2 kg/ha per year. The paired-catchment analysis revealed that SSY in the K _T catchment increased 17.0-fold compared with the prethinning period. However, the dominant hysteresis pattern remained clockwise in both pre- and postthinning periods. Sequences of large storm events in the postthinning period elevated SSY in both catchments. Increase in suspended sediment in the K _T catchment was associated with the combined impacts of thinning and sequences of storm events during the period of thinning operation.     

Land‐use effects on resource net flux rates and oxygen demand in stream sediments

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Ponds and their catchments: size relationships and influence of land use across multiple spatial scales

The information on both the catchment land use and catchment area has the potential to be adopted into the conservation and management of ponds. There have been, however, few attempts to describe the effects of land use acting at various spatial scales on ponds and the studies were restricted to specific categories of ponds. This paper presents a study on 92 ponds distributed over a broad range of environmental conditions in Central Europe. We combined an extensive field survey and a detailed analysis of sediment and water chemistry with GIS-derived data to estimate the relationship between the area of the ponds and the area of their catchments, and to assess the relationship between pond physico-chemical conditions and land use across multiple spatial scales. Relating the area of ponds to the area of their catchments, we found a significant positive relationship (r = 0.72). Considering land use effects on pond conditions, catchment-scale land use was the only significant spatial extent influencing the physico-chemical conditions. Most notably, the proportion of intensively exploited land (arable land, urban areas) in the catchment scale was positively correlated with the deterioration of pond physico-chemical properties. The results of the study suggest that effective conservation of ponds cannot be achieved merely through the management of narrow buffer zones around them but should involve maintenance of less intensive land use within the whole catchment. Moreover, easily accessible catchment-scale GIS data could serve as a decision-support tool for cost-effective management strategies aimed at improving pond physico-chemical conditions.     

The effect of evapoconcentration on dissolved organic carbon concentration and quality in lakes of SW Greenland

1. Dissolved organic carbon (DOC) concentration was determined for a range of lakes of varying conductivity (30–4000 μS cm⁻¹) in the low Arctic of SW Greenland. DOC concentration range from <1 to >100 mg C L⁻¹, occasionally approaching 200 mg C L⁻¹ in meromictic, oligosaline lakes. DOC concentration was strongly related to [log₁₀] conductivity and total nitrogen. 2. Peak DOC concentrations (>80 mg L⁻¹) occur in lakes located approximately 50 km from the present ice sheet margin, a zone of low effective precipitation; evaporative concentration is the first‐order control on DOC concentration. Lakes at the coast and closer to the ice margin had lower DOC concentrations (<20 mg C L⁻¹). Local factors, notably the presence or absence of an outflow and catchment morphometry, resulted in considerable variability in concentration (20–100 mg C L⁻¹) within the area of maximum concentration around 51°W. 3. Despite their high DOC concentration, these lakes are essentially colourless. Dissolved organic matter (DOM) absorption (a₃₇₅) was low in most lakes (<10 m⁻¹) with maximum values (approximately 20 m⁻¹) occurring in one humic‐stained lake in the area. Absorption values corrected for DOC concentration () were very low (<0.6 m² g⁻¹ C) for all lakes apart from those at the coast, perhaps reflecting greater allochthonous inputs at these sites. 4. S, the spectral slope coefficient, ranged from 16 to 27 μm⁻¹ and was weakly correlated with DOC concentration. Both a₃₇₅ and S showed similar distribution patterns along the sampling gradient as did DOC, with maximum values at approximately 51°W. High and low S may indicate fresher, more rapidly flushed, systems with less degraded DOM or greater inputs from their catchments. 5. The lakes closer to the head of the fjord with higher conductivity, had low (<0.2 m² g⁻¹ C) and high S (>21 μm⁻¹) and this may reflect increasingly longer lake water residence times, greater DOM age and photochemical degradation.     

Urbanisation alters fatty acids in stream food webs

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