Implication of Lake Water Residence Time on the Classification of Norwegian Surface Water Sites into Progressive Stages of Nitrogen Saturation

Seasonal behaviour of NO₃ ^- in surfacewater is often used as an indicator on a catchment's ability toretain N from atmospheric deposition. In this paper, weclassify 12 pristine sites (five streams and seven lakes) insouthernmost Norway according to the N saturation stageconcept. All examined sites were acid-sensitive and had annualmean NO₃ ^- concentrations in the range 6–36 μeqL^-1. At lake sites with relatively long water residencetimes, hydrology will have a damping effect on the seasonalNO₃ ^- oscillations in the outlet streams. Under givenrunoff conditions (1.0–2.2 m yr^-1), the seasonalNO₃ ^- pattern was clearly affected when lake:catchmentarea ratios exceeded 0.15 and the total residence time of lakesin the catchments exceeded 0.3 yr. In such cases, annualmean NO₃ ^- concentration rather than seasonalvariations may be the better indicator of N saturation. Toaccount for this we propose a set of supplementary criteria forsuch lake systems, defining limit values for annual meanNO₃ ^- concentrations within each stage class. Beforebeing applied on a broader scale, however, we recommend anexamination of additional lake-dominated catchmentsrepresenting a larger gradient in ecosystem types, N depositionlevels and hydrologic regimes. When applying the supplementarycriteria on the Norwegian sites, two were classified as stage 0(no saturation), five as stage 1 (early stage of saturation)and five as stage 2 (saturated – moderate N loss). No siteswere showing symptoms of stage 3, which characteriseswatersheds that are net sources of N, rather than sinks. Theresults indicate a great variability in N retention capacity inthe study region, despite the fact that many of the catchmentsexperience relatively uniform N deposition amounts and climaticconditions. This suggests that much of this variability must bedue to specific catchment characteristics as e.g. soil type,soil depth, and vegetation cover.     

N Leaching from Small Upland Headwater Catchments in Southwestern Norway

We investigated nitrogen leaching and input-output budgets from 12 small, upland headwater catchments with differing fractions of peat, heather and bare rock in SW Norway. A close relationship was found between annual inorganic nitrogen loss and the fractional cover bare rock explaining 74% of the variation. It was not possible to distinguish between the N leaching from the peat and heather dominated catchments in this investigation. Nitrate loss was negatively correlated to the C/N ratio of the soil organic horizon. Lowest soil C/N ratios of the soil organic surface horizon occurred in catchments receiving the highest amounts of N deposition. Our data for Norwegian moorland are in agreement with previous investigations relating soil C/N ratio and N leaching in forest soils. Runoff from the catchments showed a seasonal pattern in NO₃ ^? concentrations. The low values during the summer are presumably due to increased biological activity (plant uptake and immobilization by soil microbes). The winter and spring NO₃ ^? concentrations in 2001 in all catchments were much higher than in 2000, perhaps due to soil freezing.     

Can Phosphate Help Acidified Lakes to Recover?

Experimental addition of phosphate to enclosures in an acidified lake in Southern Norway was performed to study the effect on nitrate, pH and labile aluminium along a gradient of phosphate from 4–19 µg P L^?1. Nitrate decreased from 180 µg L^?1 to below detection limit after three weeks at P-concentrations > 17 µg L^?1, due to phytoplankton uptake. pH increased from 4.9 to 5.2, corresponding to a 50% decrease of H⁺-equivalents from 12 to 6 µg P L^?1 due to algal uptake of H⁺-ions when assimilating NO₃ ^?-ions. Due to the increased pH and probably also precipitation with phosphate, concentrations of labile aluminium decreased from 150 to 100 µg L^?1 within the P-interval 4–19 µg L^?1. Algal biomass increased from 0.5 to 6 µg chlorophyll a L^?1 along the same P-gradient. The results suggest that moderate P-addition (< 15 µg P L^?1 to avoid eutrophication problems) can improve water quality in moderately acidified lakes, and also increase nitrate retention in strongly acidified lakes. In humic lakes, the treatment will be less efficient due to light limitation of primary production and the presence of organic acids.     

Potentially Mobile Lead Fractions in Montane Organic-Rich Soil Horizons

Anthropogenic emissions during the 20th century resulted in global lead (Pb) contamination of soils. Recent studies have demonstrated that the organic horizons of temperate montane Spodosols in the northeastern United States retain Pb on timescales of 50 to 150 years. The precise mechanism(s) of this strong Pb partitioning to organic-rich soil material remain elusive, but a detailed understanding of Pb retention by organic layers and mineral topsoils is critical for predicting the fate of pollutants deposited on ecosystems. Here we use selective extractions to quantify potentially mobile pools of Pb in the surface horizons of relatively remote montane Spodosols from New Hampshire and Vermont. Using 10 consecutive rinses of water, we extracted a total of 1 to 5% of the carbon, and 4 to 12% of the Pb. Dialysis equilibration experiments demonstrate that this Pb is >5,000 molecular weight, and not truly dissolved as Pb²⁺. When soil was extracted with a single rinse of 0.02 M HCl (pH 1.7), 5 to 11% of the Pb was mobilized. However, hydroxylamine hydrochloride in 0.02 M HCl (a reducing agent) extracted 30 to 40% of the Pb. Repeated rinses with sodium hydroxide and sodium pyrophosphate, which target organic matter but may extract other soil phases removed 16 to 75% and 60 to 100% of the Pb, respectively. We show that significant Fe, Pb, and Al can be released from soils under reducing conditions, and that this fraction can be underestimated if sodium pyrophosphate is used in a previous step for leaching the organic-metal phase, as is typically done in sequential extraction schemes. Our results indicate that inorganic phases play an important role in determining Pb mobility and bioavailability, even in surface soil horizons dominated by organic matter.     

The influence of omega-3 polyunsaturated fatty acids (omega-3 pufa) on lactobacilli adhesion to the intestinal mucosa and on immunity in gnotobiotic piglets

The effect of application of omega-3 polyunsaturated fatty acids (omega-3 PUFA) on intestinal colonization by Lactobacillus paracasei and on cellular immunity has been investigated in gnotobiotic pigs. The administration of polyunsaturated fatty acids positively affected the adhesion of Lactobacillus paracasei to the jejunal mucosa of gnotobiotic piglets. When compared to the control group, the number of Lactobacillus paracasei adhering to the jejunal mucosa was by 12% higher in piglets of the experimental group (5.10 log 10/cm2 vs. 4.55 log 10/cm2). The respective counts of Lactobacillus paracasei adhering to the ileal and colonic mucosa of 28 day old gnotobiotic piglets reached 4.45 and 5.05 log 10/cm2 in group C and 4.44 and 4.95 log 10/cm2 in group E. Omega-3 PUFA supplementation increased the phagocytic activity of neutrophils by almost 100% on day 28 of life as well as the subpopulations of lymphocytes (CD8) in the peripheral blood of germ-free piglets on day 21 of life. Our results indicate that the action of probiotics in the gut may be modulated by dietary PUFA. The stimulatory effect of PUFA upon adhesion of lactobacilli could be used for enhancing the effectiveness of probiotics in inhibiting digestive tract pathogens.     

Intensified forestry as a climate mitigation measure alters surface water quality in low intensity managed forests

ABSTRACT

Climate change has led to a focus on forest management techniques to increase carbon (C) sequestration as a mitigation measure. Fertilisation and increased removal of biomass have been proposed. But these and other forest practices may have undesirable effects on surface water quality. In naturally acid-sensitive areas such as much of Fennoscandia a concern is acidification due to acid deposition in combination with forest practices that increase the removal of base cations and leaching of nitrate (NO₃). Here we apply the biogeochemical model MAGIC to the coniferous-forested catchment at Birkenes, southernmost Norway, to simulate the effects of forest fertilisation and harvest on soil and streamwater. The model was calibrated to the 40-year data for water quality, soil and vegetation and then used to simulate fertilisation and clearcutting of the mature forest by either conventional stem-only harvest (SOH) or whole-tree harvest (WTH). The 5 – 10-year pulse of NO₃ following clearcut was larger with SOH than WTH. WTH causes larger acidification of surface water relative to SOH, due to greater depletion of base cations, N and C from the soil. The use of forestry as a climate mitigation measure should take into consideration the potential effects on soil and surface water quality.     

The Return of the Salmon

The Atlantic salmon population in the River Otra, southern Norway was lost during the 1960's due to acid rain and industrial and municipal pollution. The industrial and municipal pollution sources were sanitized by 1995. A concurrent reduction in acid deposition has during the last 10 years raised pH from 5.2 to 5.7 and reduced inorganic monomeric Al from 71 to 28µg Al L^?1 above the industrial area. The water quality improvement resulted in salmon fry again being caught from 1995. Physiological measurements (blood parameters and seawater tolerance) performed on smolts of Atlantic salmon exposed within the river during the spring of 1999 suggests that the smolts were fully smoltified and seawater tolerant, despite having moderate gill morphological changes and having moderate high gill Al concentrations (70–80 µg Al g^?1 dw). The smolt quality measured suggests that the river again can support a native salmon population, provided no negative change in water quality. Winter episodes and acid tributaries within the watershed can, however, offset the recovery process.     

The River Bjerkreim in SW Norway - Successful Chemical and Biological Recovery after Liming

On a large scale, the acidified River Bjerkreim, southwestern Norway, has been treated with lime since the autumn 1996. During the Atlantic salmon (Salmon salar) smolting period pH has been above 6.2 and LAl concentrations below 10 µg L-l. Before 1996, only the western part of the watercourse harboured acid-sensitive species, such as the Atlantic salmon, snails, mayflies, daphnids and Gammarus lacustris. Prior to liming in 1996, Atlantic salmon fry (0+) and parr (≥1+) were found in 4 of 20 sampling sites, contrary to 17 (fry) and 12 (parr) in 1999. Atlantic salmon catches have increased from about 0.8 tons in 1994 to about 10 tons in 1998 and 1999. Acid-sensitive invertebrates have invaded the limed parts of the river.     

Extreme acidification in small catchments in southwestern Norway associated with a sea salt episode

During heavy storm events in January 1993 in the coastal areas of south-western Norway, a sea salt episode created extreme acidification in the afforested Svela catchment. Stream-water chloride increased sharply to eight times the normal concentration and the non-marine Na concentration was calculated to ?208 μeq L^?1. Negative values indicate that Na was retained in the soil profile. By ion-exchange processes this was largely compensated by an increase in stream-concentrations of Al and H⁺. Concentrations of inorganic monomeric Al increased from about 20 to 200 μeq L^?1 and pH decreased from 4.90 to 4.45. Due to the low pH and the dramatic increase in inorganic monomeric Al the water toxicity for aquatic organisms increased. Acidification associated with the storm was also observed in a forested and a non-forested catchment, but never reached the levels of the afforested catchment. The extra vulnerability of afforested catchments may be due to their ability to intercept larger amounts of sea salts than areas less dominated by dense tree stands. Although both pH and Al went back to normal levels for the area after 3–4 months the Na/Cl-relationship in cumulated transport values indicated a longlasting effect (> 2 years) on the soil profile. Reloading the soil profile with Al and H⁺ back to prestorm values will affect the catchments ability to mobilize these ions during future sea salt episodes. More frequent episodes will probably result in less acid and Al-rich stream-water during the episodes than documented here due to incomplete reacidification of the soils.