ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Electronic Resource

Precambrian Shield Wetlands: Hydrologic Control of the Sources and Export of Dissolved Organic Matter (1998)

Schiff, Sherry ; Aravena, Ramon ; Mewhinney, Eric ; [et al.]

Springer

Climatic change 40 (1998), S. 167-188

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ISSN: 1573-1480

Keywords: wetlands ; forested catchments ; dissolved organic carbon ; carbon cycling

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Abstract Most Precambrian Shield forested catchments have some wetland component. Even small riparian wetlands are important modifiers of stream chemistry. Dissolved organic matter (DOM) is one of the most important products exported by wetlands in streams. Stratigraphic control of hydraulic conductivity generally leads to decreasing conductivity with depth. Thus important flowpaths occur in the uppermost organic rich layers and are reflected in chemical profiles of dissolved organic carbon (DOC). Accumulation of DOC in peat porewaters is the net effect of production, consumption and transport. DOC profiles vary with degree of interaction with the surrounding upland catchment and distance from the edge of the wetland as well as internal processes within the wetland. In wetlands, DOM production is offset by flushing resulting in decreasing DOC concentrations with increasing flows. Despite old carbon (2,000 to 3,000 years) at relatively shallow depths, 14C activity in DOC exported from wetlands is mostly modern (recent carbon), consistent with shallow flowpaths and export of DOM from shallow organic rich horizons. In contrast, the source area for DOM in upland catchments with developed B horizon soils increases with antecedent soil moisture conditions resulting in increasing DOC concentrations with higher stream flows. Activity of 14C in stream DOC from upland catchments span a range from low activities (older carbon) similar to B horizon soil water during dry moisture conditions to values slightly less than modern (more recent carbon) during high moisture conditions. The more modern carbon activities reflect the increased contribution of the organic rich litter and A horizon soil layers in the area immediately bordering the stream under wet antecedent moisture conditions. Reduced hydrologic export or loss of wetlands under drier climatic conditions may result in in larger fluctuations in stream DOC concentrations and reduced DOM loads to lakes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1005496331593

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2

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Significance of dissolved organic carbon in the prediction of thermocline depth in small Canadian shield lakes (1999)

Pérez-Fuentetaja, Alicia ; Dillon, Peter J. ; Yan, Norm D. ; [et al.]

Springer

Aquatic ecology 33 (1999), S. 127-133

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ISSN: 1573-5125

Keywords: fetch ; thermocline ; light ; oligotrophic ; DOC ; dystrophic ; humic

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Empirical models used to predict thermocline depths of lakes have typically been based on physical and morpho-metric variables. However, lakes with appreciable levels of dissolved organic material, including those found on the Canadian Precambrian Shield (DOC levels 1.4-12.41 mg/l), have seldom been included in these models. Our analysis suggests that for such lakes, thermocline depth is linked strongly to light penetration (Secchi depth r = 0.83, light extinction r = 0.85) which is strongly related to DOC concentration (Secchi depth r = 0.91, light extinction r = 0.97). A multivariate regression based on small Canadian Shield lakes suggests that DOC is the most important predictor of thermocline depth. Maximum effective length, maximum depth, and chlorophyll a contribute significantly to the prediction power of the regression model, but are of secondary importance in the presence of DOC.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1009998118504

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3

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Zooplankton biomass rarely improves predictions of chlorophyll concentration in Canadian Shield lakes that vary in pH (2000)

Pérez-Fuentetaja, Alicia ; McQueen, Donald J. ; Yan, Norman D. ; [et al.]

Springer

Aquatic ecology 34 (2000), S. 127-136

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ISSN: 1573-5125

Keywords: algal biomass ; bottom-up ; chlorophyll-phosphorus relationship ; Daphnia ; grazing ; grazing pressures ; Holopedium ; top-down ; trophic interactions ; zooplankton biomass

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract To determine the frequency with which zooplankton influence chlorophyll a (Chla) levels, we explored annually-averaged data from oligotrophic and mesotrophic lakes that differed in morphometry, total phosphorus (TP) concentrations, and zooplankton community composition due to pH. The data were divided into two sets according to the type of filter used to collect chlorophyll. Residuals of the Chla: TP regressions were not related to lake morphometry, TN content, water clarity or pH. In the first data set there were no consistent relationships between residuals in Chla and twelve grazer biomass variables for 37 of the 38 lakes. The single exception had a very large population of Daphnia dubiaand low concentrations of Chla for its TP. In the second data set, 3 of 25 lakes had exceptionally low Chla concentrations for their TP. These lakes were acidic (pH 〈 6) and had very large biomasses of Holopedium gibberumcorrelated with negative Chla residuals, indicating significant grazing. At pH 〉 6, Daphnia spp. strongly influenced the significant correlations. We conclude that zooplankton contribute to the prediction of Chla beyond that possible by TP alone in acidic and non-acidic Canadian Shield Lakes, but evidence for strong suppression of chlorophyll by grazers was relatively rare (4 of 63 cases) on annual time steps.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1009934506481

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4

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Key processes of the nitrogen cycle in an irrigated and a non-irrigated grazed pasture (2000)

Pakrou, Naser ; Dillon, Peter

Springer

Plant and soil 224 (2000), S. 231-250

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ISSN: 1573-5036

Keywords: grass ; leaching ; legume ; mineralisation ; N fixation ; nitrate ; urine

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract The paper presents integrated measurements of N fixation, net mineralisation, pasture yield and change in soil mineral N over a 12 month period for dairy pastures on a sandy loam soil in the South East of South Australia. The two adjacent pastures studied were an irrigated perennial white clover-ryegrass and an annual non-irrigated subterranean clover with mixed annual grasses. This produced the most comprehensive mineral N balance reported for grazed pastures, to the authors' knowledge, allowing calculation of gaseous and leaching losses of N (210 kg ha−1 in the irrigated and paddock and 81 kg ha−1 in the non irrigated paddock) primarily from urine patches. In both paddocks these losses were about three times the N yield in milk (61 and 28 kg N ha−1 respectively) and were replenished by biological N fixation (294 and 100 kg N ha−1). However, mineralisation of soil organic N, excretal N and pasture residues (687 and 438 kg N ha−1) was the major source of mineral N for cycling and losses. The results demonstrate the enormous impact of pasture management on N fluxes and reinforce the importance of livestock urine on the magnitude of N fluxes including gaseous and leaching losses.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1004838323594

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5

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The effect of core compression on the measurement of zinc concentrations and anthropogenic burdens in lake sediments (1986)

Evans, Hayla E. ; Lasenby, David C. ; Dillon, Peter J.

Springer

Hydrobiologia 131 (1986), S. 185-192

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ISSN: 1573-5117

Keywords: core compression ; sediment enrichment factor ; anthropogenic burden ; zinc

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract An attempt was made to demonstrate the significance of core compression (shortening) by the use of geochemical profiles. In Plastic Lake, Canada, the hypothesis was tested that the measured anthropogenic zinc burdens would differ in the sediments while the measured sediment enrichment factors would be comparable, in shortened and unshortened cores. However, there was no significant difference in either the anthropogenic zinc burdens or the sediment enrichment factors calculated from the shortened and unshortened cores. The fact that the anthropogenic zinc is found, almost exclusively, in the top 10 cm of the sediment in Plastic Lake may explain these results.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00006781

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6

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Dissolved organic and inorganic carbon mass balances in central Ontario lakes (1997)

Dillon, Peter J. ; Molot, Lewis A.

Springer

Biogeochemistry 36 (1997), S. 29-42

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ISSN: 1573-515X

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Geosciences

Notes: Abstract Mass balances of dissolved organic carbon (DOC) and dissolvedinorganic carbon (DIC) based on stream and precipitation inputs andoutflows were measured for seven unproductive lakes in central Ontariobetween 1981 and 1989. Net annual CO2 evasion occurred in sixof the seven study lakes with minor net invasion in the seventh. Atmosphericinvasion might have been significant at certain times of the year, particularlyduring the growing season. Net evasion rates were greater than DIC loadingrates, indicating partial mineralization of the terrestrially-derived DOC in thelakes. A steady state mass balance model adequately described the variationin DOC retention between lakes. Net annual carbon accumulation of forestcommunities based on estimates of net ecosystem production may beoverestimated because of significant export of carbon to lakes via streamsand groundwater, particularly in catchments with extensive peatlands.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1005731828660

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7

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Nitrogen mass balances and denitrification rates in central Ontario Lakes (1993)

Molot, Lewis A. ; Dillon, Peter J.

Springer

Biodegradation 20 (1993), S. 195-212

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ISSN: 1572-9729

Keywords: denitrification ; lake ; mass balance ; nitrogen

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Nitrogen mass balances for seven unproductive lakes and 20 forested catchments in central Ontario were measured between 1977 and 1989. Average annual lake denitrification rates calculated with the N/P ratio method were strongly correlated with summer anoxic factor (extent of surficial sediment anoxia) whereas denitrification rates calculated with a210Pb sediment N accumulation method were poorly correlated with the anoxic factor suggesting that the N/P method is superior. Substantial denitrification occurred in all lakes — an average of 36% of TN inputs or 75% of the net gain. On a regional area-weighted basis, 67% of bulk atmospheric TN deposition was stored or denitrified terrestrially, 12% was denitrified in lakes, 4% was stored in lake sediments, and 17% was exported from lakes. N/P ratios were generally less in streams than in precipitation suggesting preferential N retention in catchments, whereas the N/P ratios in lake outputs were slightly higher than lake input ratios, suggesting preferential P retention in lakes. This is consistent with the notion that P-limited lakes can exist adjacent to N-limited forests.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00000787

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8

Electronic Resource

THE EFFECT OF EL NIÑO-RELATED DROUGHT ON THE RECOVERY OF ACIDIFIED LAKES (1997)

Dillon, Peter J. ; Molot, Lewis A. ; Futter, Martyn

Springer

Environmental monitoring and assessment 46 (1997), S. 105-111

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ISSN: 1573-2959

Keywords: acidification ; El Niño ; global change ; Southern Oscillation (SOI) Index ; sulphate

Source: Springer Online Journal Archives 1860-2000

Topics: Energy, Environment Protection, Nuclear Power Engineering

Notes: Abstract Although SO2 emissions and deposition rates havedeclined substantially since the implementation of sulphuremission control programmes in North America [1], recovery(measured as decreases in $${\text{SO}}_{\text{4}}^{{\text{2 - }}} $$ concentrations) of affected lakes in central Ontario has been much less substantial thananticipated based on the decrease in deposition. The slowrecovery is attributed to the reoxidation and release of storedsulphur in catchments. Reduced sulphur retained in previousyears when sulphur deposition was higher is exposed to air andoxidized during severe droughts, then exported duringsubsequent wet periods. Elevated stream $${\text{SO}}_{\text{4}}^{{\text{2 - }}} $$ concentrations and export rates occur in the autumns of yearswith prolonged severe droughts, particularly in catchments withextensive wetlands. Drought in our study catchments occurred inyears following strong El Niño events. When the SouthernOscillation Index (SOI) was strongly negative (1976–77, 1982–83,1986–87, 1991–92, 1993–94) the frequency of occurrence ofdrought the following summer in small catchments with shallowoverburden was extremely high. A lake‘s rate of recovery fromacidification depends upon the amount of excess reduced Sthat has been stored in anoxic zones in the catchment (largely afunction of the extent of wetlands) during years of elevated Sdeposition rates, and the frequency and severity of droughts. Iflong-term changes in global or regional climate alter thefrequency or magnitude of El Niño-related droughts, therecovery of acidified lakes will be affected.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1005740002952

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