Acid Deposition and the Acidification of Soils and Waters

Convergence of trophic state and the lower food web in Lakes Huron, Michigan and Superior

Sulfur and nitrogen emissions in the Czech Republic and Slovakia from 1850 till 2000

P> A survey of c. 350 remote high altitude and high latitude lakes from 11 different mountain regions was undertaken to explore species distribution across Europe at a scale not previously attempted.Lakes were sampled for planktonic crustaceans, rotifers, littoral invertebrates and sub-fossil chironomids, diatoms and cladocerans. Each lake was characterised in terms of water chemistry, morphology, catchment attributes and geographical location.Separate twinspan analyses were undertaken on diatom, chironomid, planktonic crustacean, littoral invertebrate and cladoceran (chydorids only) data to classify sites according to taxonomic composition. For most datasets there was a spatial component to the classification with distinct geographical groups emerging - Norway and Scotland, Finland and Central/Eastern Europe.Constrained ordination methods were employed to examine how species responded to a range of environmental factors, which were aggregated into a series of component groups - proximal environment (the chemical, trophic and physical attributes of the lake), catchment characteristics and geographical location. Several key environmental gradients were identified, which explained significant levels of the variance across several of the biological groups including dissolved organic carbon (chironomids, planktonic crustaceans), temperature (chironomids and littoral invertebrates), chloride/sea-salt (littoral invertebrates, diatoms and rotifers), lake morphology (all groups), calcium/pH (diatoms), nitrate (chydorids, littoral invertebrates, rotifers and planktonic crustaceans) and fish (littoral invertebrates). In some cases these statistical relationships are likely to represent direct ecological constraints and, in others, it is probable that the environmental variable is acting as a surrogate for some other attribute or process.Variance partitioning was undertaken to quantify how much of the variation in each biological group could be uniquely attributed to variables representing the proximal environment, catchment characteristics and geographical location. For most groups the location of the lake tends to explain the greatest variation in species composition across the Lake Districts. The proximal environment was also important but, with the exception of diatoms, secondary to location. Therefore, a strong geographical signal emerged from the analyses. Three distinct limno-regions were identified; Nordic (Scotland and Norway), Sub-Arctic (Northern Finland) and Alpine (Pyrenees, the Alps and Eastern Europe ranges).Our results have implications for the development of regionalisation schemes based on biological responses to environmental gradients; (i) lake 'types' based on environmental factors cannot be extrapolated throughout Europe, even within the relatively narrow gradients found in remote mountain lakes, (ii) biotic response to large-scale variations in environmental conditions, such as those that could be expected with climate change, is likely to vary according to regions because of the biogeographical differences among them.

Regionalisation of remote European mountain lake ecosystems according to their biota: environmental versus geographical patterns.

Ninety-one lakes distributed along the Tatra Mountains (most of lakes > 1 ha and 65% of lakes > 0.01 ha) were sampled and analysed for ionic and nutrient composition in September 2004 (15 years after reduction in acid deposition). Eighty-one lakes were in alpine zone and ten lakes in Norway spruce forest. The results were compared to similar lake surveys from 1994 (the beginning of water recovery from acidification) and 1984 (maximum acidification). Atmospheric deposition of SO
 4
 2−
 and inorganic N decreased 57% and 35%, respectively, in this region from the late 1980s to 2000. Lake water concentrations of SO
 4
 2−
 and NO
 3
 −
 have decreased both by ∼50% on average (to 23 and 19 μmol L−1, respectively, in 2004) since 1984. While the decrease in SO
 4
 2−
 concentrations was stable throughout 1984–2004, most of the NO
 3
 −
 decrease occurred from 1994 to 2004. The declines in SO
 4
 2−
 and NO
 3
 −
 concentrations depended on catchment coverage with vegetation, being most rapid for SO
 4
 2−
 in forest lakes and for NO
 3
 −
 in rocky lakes. Concentrations of the sum of base cations (dominated by Ca2+) significantly decreased between 1984 and 2004, with the highest change in rocky lakes. Most of this decline occurred between 1994 and 2004. Acid neutralising capacity (ANC) did not change in the 1984–1994 period, but increased on average by 29 μmol L−1 between 1994 and 2004, with the highest change in rocky lakes. Over the last decade, the proportion of lakes with ANC > 150 μmol L−1 increased from 15% to 21% and that of ANC < 20 μmol L−1 decreased from 37% to 20%. The highest decline in H+ and Al concentrations occurred in the most acid lakes. On a regional basis, no significant change was observed for total phosphorus, total organic nitrogen, and dissolved organic carbon (DOC) in the 1994–2004 period. However, these parameters increased in forest lakes, which exhibited an increasing trend in DOC concentrations, inversely related (P < 0.001) to their decreasing ionic strength (30% on average in 1994–2004).

Chemical composition of the Tatra Mountain lakes: Recovery from acidification

A dynamic process-based model of surface water acidification, MAGIC, was applied to 31 representative alpine lakes in the Tatra Mountains (~50% of all alpine lakes >0.3 ha in the lake-district). The model was calibrated to observed lake chemistry for the period 1980-2002. Surface water and soil chemistry were reconstructed from 1860 to 2002, given estimates of historical acid deposition, and forecast to 2020 based on the reduction in sulphur and nitrogen emissions presupposed by the Gothenburg Protocol. In the 1860s, all lakes were buffered by the carbonate system and only ~6% of lakes had acid neutralising capacity (ANC) 50% of the SAA change) in sensitive lakes with intermediate weathering rates and little soils (low BC exchangeable capacity and elevated terrestrial export of nitrate) and (3) by parallel changes in concentrations of protons and aluminium (each ~20% of the SAA change) in extremely sensitive lakes, with the lowest weathering rates and soil base saturation. The full implementation of the Gothenburg Protocol will not be sufficient to allow recovery of the latter group of lakes, which will remain acidified after 2020.

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Evžen Tuchlík

Papers

Response of alpine lakes and soils to changes in acid deposition: the MAGIC model applied to the Tatra Mountain region, Slovakia-Poland