Methods of pH calibration of sedimentary diatom remains for reconstructing history of pH in lakes

The pH history of lakes can be inferred from diatom remains in dated sediment cores. To derive transfer functions for pH inference in acidic lakes, we counted diatoms in surface-sediment from 31 soft-water lakes in n. New England (NE) and 36 in Norway (N), covering pH 4.4–7.1. Cluster analysis of each data set indicates that pH 6 is an upper limit for a group of similar diatom assemblages. For each set, we developed multiple linear regressions to relate three versions of the diatom data to pH of surface-waters: (1) relative frequencies of selected diatom taxa, (2) the first principal component (1 PC) of these frequencies, and (3) the frequencies of Hustedt pH groups. Also, simple linear regressions were developed for two versions: (1) Index B and (2) Index Alpha, both based on pH groups. Regressions were run separately for lakes with pH 6; these are most relevant for pH inference in acidic lakes. The best regressions (N: taxa & 1 PC taxa) have r² 0.69–0.91 and S_e 0.24–0.31 pH units, the worst (NE: log alpha) have r² 0.27–0.57 and S_e 0.51. In all cases, errors for NE are greater than N, partly due to greater diversity of NE lakes. Regressions based on pH groups (directly & by indices) have smaller r² and larger S_e than those based on taxa and 1 taxa. The Index Alpha is least useful because its requirement for alkaline diatom units is unsatisfied at many acidic lakes. Regressions based on taxa may give erratic pH inferences due to sensitivity to unusual frequencies of individual taxa; this effect is reduced by using 1 PC taxa. Four regressions based on pH 6 lakes were used for inferring pH in a ²¹⁰Pb dated core from Nedre Målmesvatn, N (now pH 4.6). There is good agreement among three of the four (not for the regression based directly on taxa) that there has been a decrease of ca. 0.6 pH units starting in the late 1800's.     

Diatom distribution and diatom inferred pH in the sediment of four alpine lakes

The diatom distribution in the sediment of four alpine lakes in the central alpine area (Ötztaler Alpen, Tyrolia, and Mölltal, Carinthia) has been analysed in order to assess possible influences of atmospheric pollutants on remote lakes. The lakes are located more than 2000 m above sea level on poorly buffered bedrock (granite, gneiss and mica schist) and are therefore susceptible to acidification by acid deposition. The pH history of the lakes has been calculated by using Index B from Renberg & Hellberg (1982), which has been adjusted to central European conditions and applied in this region for the first time. The results indicate that there have been no pH decreases in three of the lakes, while in one lake diatom composition and distribution change significantly towards the sediment surface. But taxonomical problems and difficulties in the pH classification of the rarely found diatoms complicate the interpretation of the results. Important taxa will be discussed in view of their ecological significance.     

Paleolimnological investigation of three manipulated lakes from Sudbury,Canada

Stratigraphic changes in diatoms and chrysophytes from three manipulated Sudbury lakes were explored in an attempt to examine the influence of fertilization and/or neutralization on algal microfossil assemblages. Both diatom- and chrysophyte-inferred pH profiles indicate that the pH of Labelle Lake has remained fairly stable in the past. The study of Labelle and Middle lakes indicates that the addition of nutrients to acidic and non-acidic oligotrophic lakes did not directly influence diatom and chrysophyte species composition, perhaps because pH remained stable. The diatom and chrysophyte assemblages of Middle Lake only changed when the pH was raised. In Mountaintop Lake the recent shift in chrysophyte species composition and the resulting inferred pH decline is most likely related to a decline in mid-summer epilimnetic pH. Reliable paleolimnological inferences are difficult in lakes such as these because it is difficult to track limnological conditions in the absence of modern analogues.     

Relationships between lakewater pH and sedimentary diatoms in the Matamek Watershed,Northeastern Quebec,Canada

Twenty lakes in the Matamek and nearby watersheds were sampled in the summer of 1983 for water chemistry and surficial sediments. Thirty-two physical and chemical variables, including pH, alkalinity, cations and metal concentrations were measured on samples from the epilimnion and hypolimnion of each lake. In three lakes, two to four replicate cores were collected to estimate spatial variability of the sediment flora.All lakes were acidic (pH 4.59 to 5.80), highly colored and poorly buffered. Aluminum and magnesium concentrations reached 494 and 70 µg l^-1, respectively. The pH of the lakes appears to be declining, as indicated by a comparison of our results with those from a survey done in 1970. An empirical chemical model based on the alkalinity/sulfate ratio and the regression of pH on calcium also indicated that these lakes may be undergoing acidification.Analyses of the diatom flora of the surficial sediments showed strong dominance of 6 species that cooccurred with a large number of rare species (in all, 229 taxa were found). Variability among samples within a lake was as high as among lakes. Calculation of Nygaard's alpha index for each sample and the regression of its log-transformed value on surface pH yielded a relationship that was significantly from other published models. The regression model was applied to a down-core analysis of the diatom flora of the sediments of two lakes. Although the large confidence intervals on pH values predicted by the model obscured any evidence of pH change with sediment depth, there was a significant increase of acidophilous and a decrease of circumneutral species over time, suggesting that a change in the flora, possibly correlated with pH, is taking place.In making comparisons among lakes, the surficial-sediment flora did not provide clear evidence of a relationship with the pH of surface water. Indices computed from the surficial-sediment flora are apparently insensitive to differences in pH over a narrow range, particularly when the lakes being compared are similar chemically. Nygaard's alpha index is shown to be unduly sensitive to outliers. The currently accepted assumption of a progressive linear change in communities may be inadequate for the quantification of acidification processes. Other models, derived from catastrophe theory, may prove more fruitful.     

Correlation of surface sediment diatoms with the present lake water pH in 28 Algoma lakes,Ontario, Canada

The surface sediment diatom analysis of 28 Algoma lakes (pH 4.40–8.13) indicates that even though each lake has a widely different aquatic environment and characteristic diatom assemblage, a definite relationship exists between the lake water pH and their diatom assemblages. In the acidic lakes acidobiontic and acidophilous diatom species predominate whereas in circumneutral and alkaline lakes circumneutral and alkaliphilous diatoms were most common. Cluster analysis of the pH indicator diatom assemblages grouped the study lakes into three distinct cluster groups. These groups also closely corresponded to lake water pH. On the basis of published ecological information as well as their presence in our study lakes, the pH indicator status of a number of diatom taxa have been discussed. A detailed listing of the diatom taxa identified and their pH indicator status is provided in order to facilitate their use in future diatom-inferred pH studies.     

Paleolimnological reconstruction of the effects of atmospheric deposition of acids and heavy metals on the chemistry and biology of lakes in New England and Norway

Sediment cores from nine lakes in southern Norway (N) and six in northern New England (NE) were dated by ¹³⁷Cs, ²¹⁰Pb and in NE also by pollen, and were analyzed geochemically and for diatoms. Cores from two N and three NE lakes were analyzed for cladocerans. ¹³⁷Cs dating is unreliable in these lakes, probably due to mobility of Cs in the sediment. In Holmvatn sediment, an up-core increase in Fe, starting ca. 1900, correlates with geochemical indications of decreasing mechanical erosion of soils. Diatoms indicate a lake acidification starting in the 1920's. We propose that soil Fe was mobilized and runoff acidified by acidic precipitation and/or by soil acidification resulting from vegetational succession following reduced grazing. Even minor land use changes or disturbances in lake watersheds introduce ambiguity to the sedimentary evidence relating to atmospheric influences. Diatom counts from surface sediments in 36 N and 31 NE lakes were regressed against contemporary water pH to obtain coefficients for computing past pH from subsurface counts. Computed decreases of 0.3–0.8 pH units start between I890 and I930 in N lakes already acidic (pH 5.0–5.5) before the decrease. These and lesser decreases in other lakes start decades to over a century after the first sedimentary indications of atmospheric heavy metal pollution. It is proposed that the acidification of precipitation accompanied the metal pollution. The delays in lake acidification may be due to buffering by the lakes and watersheds. The magnitude of acidification and heavy metal loading of the lakes parallels air pollution gradients. Shift in cladoceran remains are contemporary with acidification, preceding elimination of fishes.     

The impact of atmospheric deposition on the aquatic ecosystem with special emphasis on lake productivity,Newfoundland, Canada

To document and analyze the ecosystem response to acidification and possible concurrent heavy metal enrichment process, a detailed paleoecological study was conducted in Lake 817, a small, and sensitive, second order lake, in insular Newfoundland. The inferred pH history of the lake was recreated using the region-specific equation relating fossil diatom taxa to pH. The profile demonstrated a fairly stable pH history over the bottom 22 cm of the sediment core with an appreciable pH decline in the upper 5 cm. The decrease of inferred pH began in the 1930's (ca. 1931 to 1944) and the lowest inferred pH value (5.3) was observed in the surface stratum. The decreasing pH trend (0.4 unit; 5.7 to 5.3) between ca. 1931 and 1985 correlated well with changes in sediment chemistry. Major elements (P, Mg, Ca, Na, and K) showed significant decrease in deposition primarily in the upper 3 cm level (ca. 1944). The profiles of selected metals (Fe, Mn, Cr, Cu, Zn, Pb, Co, Hg, As, and Ni) indicated that the deposition of these elements increased noticeably, primarily in the upper 3 cm level. The enrichment of Pb began earlier, about 50 years ago (1931 to 1944). The stratigraphy of fossil pigments (chlorophyll derivatives and total carotenoids) demonstrated a general trend of increasing accumulation upwards in the core while the only significant decrease in pigments was observed in the recent strata (ca. between 1957 to 1985). The most dramatic decrease of primary production occurred during ca. 1957 to 1974 period and this phenomenon was associated with increased levels of heavy metals. It seems that primary production in oligotrophic, acidifying lakes in Newfoundland is controlled more by nutrients loading and the possible toxicological effects of heavy metals, than directly by water acidity.     

Hydrological controls on the diatom assemblage of a seasonal arctic river: Boothia Peninsula,Nunavut, Canada

This study characterizes the melt season diatom assemblage of a middle arctic river with respect to hydrological conditions. In addition, the potential to identify species that show a strong affinity for the lotic environment provides an opportunity to interpret stratigraphic changes in these species in the lake sedimentary record in terms of past hydrological change. Understanding long-term hydrological variability is critical for assessing both current and future environmental change. Significantly higher relative abundances of Achnanthes minutissimaKützing, Fragilaria capucina var. vaucheriae (Kützing) Lange-Bertalot, Diatoma tenuisAgardh, Cymbella arctica(Lagerstedt) Schmidt, C. minutaHilse ex. Rabenhorst, C. silesiaca Bleisch and Encyonema fogedii Krammer in the lotic environment throughout the 2001 growing season compared to the lacustrine sedimentary record suggest that these species characterize the Lord Lindsay River diatom assemblage. Comparison of seasonal abundances of these taxa to hydrological parameters including discharge, electrical conductivity, and water temperature reveal key information about the character of this community. The fact that the river diatom assemblage changes very little throughout the sampling period, despite major changes in hydrological conditions, suggests a degree of resilience and inherent structure in the community. However, a decrease in diatom biomass in response to rapid and dramatic changes in hydrological conditions following a major rainfall event suggests that a threshold tolerance may exist, with potentially important implications for interpreting stratigraphic changes in the paleoenvironmental record.     

Morphological variation in populations of the diatom Asterionella ralfsii W. Smith from Nova Scotia,Canada

Preliminary investigations of the diatom genus Asterionella ralfsii W. Smith from Kejimkujik National Park, Nova Scotia indicate that its morphology differs from other reported forms. Mean cell length increased between the spring and the fall. Bimodal distribution of length classes occurred in several lakes and was not related to measured environmental variables. The need for further work on this species in this and other geographical areas is considered.     

Interannual and between-site variability in the occurrence of clear water phases in two shallow Mediterranean lakes

It is widely accepted that clear water phases constitute a regular stage in the seasonal succession of plankton in dimictic lakes and reservoirs (i.e. PEG Model). The occurrence of such a phenomenon in Mediterranean shallow lakes is characterised by a marked interannual variability, which makes it difficult to establish reliable predictions on the dynamics and functioning of plankton in these ecosystems. In the present paper we analyse the factors influencing the occurrence of the clear water phases in the two shallow lakes of the Albufera of Adra, a coastal wetland region of south-eastern Spain: Lake Honda and Lake Nueva. Despite their geographical proximity, both lakes depicted large hydrological and limnological differences. Lake Honda is an epigenic and recharge lake that is strongly influenced by the hydrological conditions in its watershed, while Lake Nueva can be classified as a hypogenic and discharge lake and, as such, is less affected by the hydrological regime. In contrast, the morphometry, exposure and fetch of Lake Nueva make this ecosystem especially sensitive to wind forcing. Clear water phases in these shallow lakes were linked with periods of low thermal stability and the dominance of small-edible algae in the phytoplankton community, both of which allowed a Daphnia magna population to grow up and induce the algae collapse by grazing. In Lake Honda, those conditions were met during the spring of 2002 under the influence of intense rainfall-events, while in Lake Nueva the clear water phase was induced in the spring of 2003 by the occurrence of strong and frequent wind events. In both lakes, a relatively high water column thermal stability and the abundance of cyanobacteria early in the spring prevented the development of the Daphnia magna population and the occurrence of the clear water phase.     

Lessons Learned from Reconstructing Interactions Between Local Ecological Knowledge, Fisheries Science, and Fisheries Management in the Commercial Fisheries of Newfoundland and Labrador, Canada

Questions centered on the development of local and traditional ecological knowledge and the relationship of that knowledge to the development of conservation and management practices have recently attracted critical attention. We examine these questions with respect to the dynamic commercial fisheries of the Canadian province of Newfoundland and Labrador. The knowledge of fish harvesters coevolves with fishing practices and is embedded in a dynamic socioecological network that extends into and beyond the fisher, fishery households, and communities to include management, technologies, markets, and marine ecological conditions. Changes in these networks have moved knowledge and practices related to fishing in directions defined by policy, science, economic rationality, and new ecological realities. We characterize this movement as a shift along a continuum from local ecological knowledge (LEK) towards globalized harvesting knowledge (GHK) as harvesters become increasingly disconnected from socioecological relationships associated with traditional species and stocks. We conclude with a discussion of how LEK/GHK have interacted over time and space with other knowledge systems (particularly science) to influence management, and suggest that contingent, empirical evaluations of these interactions will provide a fruitful avenue for future interdisciplinary research.

光肩星天牛产卵刻槽含水量与pH值的分析

测定了光肩星天牛Anoplophora glabripennis(Motsch.)在柳树皮上产卵刻槽、模拟刻槽及健康树皮的含水量和pH值。结果表明:柳树在不同受伤条件下的含水量及pH值都有所不同,其中含水量的顺序为产卵刻槽>健康树皮>模拟刻槽;pH值的顺序为产卵刻槽>模拟刻槽>健康树皮。这些结果为进一步研究刻槽内微生物的种类和丰度及树木在不同受伤条件下的生理反应提供依据。     

The interactions of water hardness and pH with the acute toxicity of zinc to the brown trout, Salmo trutta L.

Exposure of brown trout, Salmo trutta , to zinc under continuous flow conditions over 96 h showed that both water hardness and pH exert major influences on the toxicity of the metal. 96-h LC50 values for total zinc ranged from <0.14mg 1⁻¹ in alkaline soft water (pH 8; lOmg 1⁻¹ as CaCO₃) to 3.20 mg 1⁻¹ in acidic hard water (pH 5; 204 mg 1⁻¹ as CaCO₃). A variable reduction in zinc toxicity in hard water compared with soft water over the pH range 4–9 was attributed to high external calcium. Zinc toxicity was positively correlated with decreasing acidity over the pH range 5–7, the metal being most toxic at pH 8–9 where metal complexes predominate. Below pH 5 metal toxicity also increased, irrespective of hardness. Water hardness and pH interacted with zinc toxicity in a complex manner, apparently dependent on physical and chemical transformations of the metal, and as changes in uptake. detoxification and excretion by the fish.     

Changes in the algal composition and water quality of the Sundays River,Karoo, South Africa,from source to estuary

A first survey was done on algae present in the Sundays River from its source to its confluence with the sea. Species found in the upstream sections of the river included indicators of good water quality, but the quality deteriorated downstream with peaks in algal abundance being ascribed to peaks in nutrient concentrations. Cyanobacteria and euglenoids were present in the upper and middle reaches of the river, but were absent downstream. Dinoflagellates became more important downstream, especially in the estuary. Dominant species, reaching high concentrations along the river, included Nitzschia frustulum, Nitzschia capitellata, Carteria klebsii, Chlorella vulgaris and Anabaena species. The presence of the diatom Eolimna comperei is a first record of its occurrence in South Africa. The Sundays River can be described as a brackish, hard water system with high nutrient concentrations in certain sections. The most important contributors to high nutrient concentrations were point sources in the vicinity of towns along the river banks, as well as diffuse sources contributing to high nitrogen concentrations in the fertile Sundays River valley. Increasing salinities were due to pollution, evaporation and agricultural activities in the valley.     

Modelling the effect of temperature, water activity and pH on the growth of Serpula lacrymans

Aims: To predict the risk factors for building infestation by Serpula lacrymans, which is one of the most destructive fungi causing timber decay in buildings. Methods and Results: The growth rate was assessed on malt extract agar media at temperatures between 1·5 and 45°C, at water activity (a_w) over the range of 0·800–0·993 and at pH ranges from 1·5 to 11·0. The radial growth rate (μ) and the lag phase (λ) were estimated from the radial growth kinetics via the plots radius vs time. These parameters were then modelled as a function of the environmental factors tested. Models derived from the cardinal model (CM) were used to fit the experimental data and allowed an estimation of the optimal and limit values for fungal growth. Optimal growth rate occurred at 20°C, at high a_w level (0·993) and at a pH range between 4·0 and 6·0. The strain effect on the temperature parameters was further evaluated using 14 strains of S. lacrymans. The robustness of the temperature model was validated on data sets measured in two different wood‐based media (Quercus robur L. and Picea abies). Conclusions: The two‐step procedure of exponential model with latency followed by the CM with inflection gives reliable predictions for the growth conditions of a filamentous fungus in our study. The procedure was validated for the study of abiotic factors on the growth rate of S. lacrymans. Significance and Impact of the Study: This work describes the usefulness of evaluating the effect of physico‐chemical factors on fungal growth in predictive building mycology. Consequently, the developed mathematical models for predicting fungal growth on a macroscopic scale can be used as a tool for risk assessment of timber decay in buildings.     

First results on the water chemistry, algae and trophic status of an Andean acidic lake system of volcanic origin in Patagonia (Lake Caviahue)

The acidic caldera lake Caviahue (Patagonia, Argentina) and its main tributaries were studied on two dates during September 1998. The main results are: The acidity of the Lake Caviahue (pH: 2.56, acidity: >5 mmol H⁺ l^–1) is controlled by the extremely acidic Upper Rio Agrio (pH: 1.78, acidity: >20 mmol H⁺ l^–1). The high sulphate contents of both the river and the lake can be attributed to sulphuric acid generated by the uptake of sulphurous gases in the crater lake of Copahue Volcano at approximately 2800 m a.s.l. The high concentrations of both Fe and trace metals (e.g. Cr, Ni, Zn) in Lake Caviahue originate from sulphur–acid interactions with the predominantly volcanic geology of the catchment area. The P-rich andesitic geology influences both the Upper and Lower Rio Agrio and Lake Caviahue. Both were found to have high phosphorus concentrations (300–500 g P l^–1) indicative of a high potential for eutrophication. The plankton community consisted of bacterioplankton, phytoplankton and rotifers. The phytoplankton was dominated by one green alga, Keratococcus raphidioides (>90% of total abundance) followed by a green sphaerical and Chlamydomonas sp. The total phytoplankton density was about 15000 cells ml^–1 in the upper 10 m of the water column. Rotifers were represented by one bdelloid species and their abundance was highly variable (360–4040 ind l^–1) in the water columm. In the Upper and Lower Rio Agrio, the epilithic community was dominated by one chloroccocal species and two species of Ulothricales. According to trophic categories based on phytoplankton density and TP concentration, Lake Caviahue can be classified as mesotrophic/eutrophic. However, chlorophyll a concentrations observed were not in agreement with this state.     

The geochemistry of two hard water rivers,the Rhine and the Rhone: Part 3: The relations between calcium,bicarbonate, sulphate and pH

In the hard water rivers Rhine and Rhone the quotient Ca/HCO₃ is strongly related to the sulphate concentration and not to the pH. The relationship can be described (by least square analysis) for the Rhine: Ca/HCO₃) = 0.70 + 0.5 (SO₄), for the Rhone: (Ca/HCO₃) = 0.85 + 0.43 (SO₄). With a Teissier analysis (reduced major axis) a slope for both rivers of 0.58 has been found. These values equal the theoretically expected value of 0.5, when a solution of CaSO₄ is added to a saturated solution of CaCO₃. The source of the CaSO₄ (gypsum) is thought to be natural in the Rhone and anthropogenic in the Rhine. Acidification of both rivers is probably the result of decomposition of disposed organic matter.     

Dioxygen uptake by isolated thylakoids from lettuce (<Emphasis Type="Italic">Lactuca sativa</Emphasis> L.): simultaneous measurements of dioxygen uptake,pH change of the medium and chlorophyll fluorescence parameters

The setup has been elaborated for the simultaneous measurements of dioxygen uptake, pH changes, and chlorophyll a fluorescence parameters of an isolated thylakoid suspension. Using this equipment we have found at least three kinetically distinguishable components in the response of dioxygen uptake and pH increase to light intensity in the range of 0–1600 μE m⁻² s⁻¹. The pH changes were not observed in the presence of uncouplers (2 μM valinomycin plus 2 μM nigericin) while O₂ uptake increased by about 10% and F _v /F _m ratio appeared to be unaffected by this treatment. Treatment with DNP-INT, an inhibitor of plastoquinol oxidation, led to a significant reduction of pH increase and O₂ consumption whereas F _v /F _m was impaired only to 71% of the control. Incubation with catalase (580 U/ml) caused a total inhibition of oxygen uptake, while the pH increased and the F _v /F _m ratio decreased to about 60% and 85% of the control, respectively. The addition of catalase after the irradiation period led to an evolution of the same amount of dioxygen as was consumed during the light period. These results show that hydrogen peroxide was formed in the investigated system and accumulated during illumination. On the basis of the obtained data, three sites of dioxygen reduction within isolated thylakoid membranes and the dependence of dioxygen uptake on the photosystem activities were discussed.     

New records of water mites of the family Torrenticolidae (Acari, Hydrachnidia) with descriptions of two new species from Nanshih River system in Taiwan and redescription of Torrenticola ussuriensis (Sokolow, 1940) from the Russian Far East

New records of torrenticolid water mites (Acari: Hydrachnidia, Torrenticolidae) from Nanshih River, Taiwan, are presented. Two new species are described: Torrenticola nanshihensis and Torrenticola taiwanicus; the latter species is compared with Torrenticola ussuriensis (Sokolow, 1940), a poorly known species which is re-described based on a new material from the Russian Far East; Monatractides cf. circuloides (Halík, 1930)is reported for the first time for Taiwan.