Organic chlorine compounds in lake sediments. IV. Dioxins, furans and related chloroaromatic compounds

Polychlorodibenzo-p-dioxins (PCDDs), polychlorodibenzofurans (PCDFs), polychloronaphthalenes (PCNs) and coplanar PCBs were measured in surface sediments from 18 lake areas in Central Finland. Toxic 2, 3, 7, 8-substituted PCDD and PCDF congeners occurred at low levels (<20 − 230 pg/g dw). PCNs appeared at few ng/g (total PCNs) levels. Pulp mills or any other local sources could not be associated with the sedimented PCDDs, PCDFs and PCNs. Coplanar PCB congeners 77 and 105 (IUPAC Nr) were generally found at 20–550 pg/g levels. The most toxic congener 126 was measured (110 pg/g) only at one area near a local PCB leakage. Pulp mill originated aromatic chlorocompounds which coelute with PCDDs and PCDFs in clean up, probably alkyl polychlorobibenzyls (R-PCBBs) appeared at ng/g levels and showed a clear gradient dowstreams from pulp mill effluent points.     

Rapid behavioural and morphological responses of hydropsychid larvae (Trichoptera, Hydropsychidae) to sublethal cadmium exposure

Larvae of Hydropsyche contubernalis and H. siltalai were exposed to sublethal cadmium concentrations of 0, 0.012, 0.16 and 10 mg/litre(-1) for 72 h. Linear logit models revealed a significant increase in the frequency and degree of damage of the anal papillae of both species with increasing Cd concentration. Hydropsyche contubernalis showed a stronger and earlier anal papillae response under Cd exposure than H. siltalai, whereas in the latter species darkening of the ventral sides of the abdomen was also observed. The lowest Cd level altered the competition behaviour of Hydropsyche contubernalis larvae after only 24 h exposure, yet no visual signs of morphological damage were detected. The exposure intruder larvae spent significantly less time trying to enter the nets of resident larvae than did unexposed intruders. In addition, both the exposed intruders and exposed residents pursued different behavioural tactics during the encounters compared to their unexposed counterparts.     

Effects of male removal on female foraging behavior in the Eurasian treecreeper

In old, spruce-dominated forests of central Finland, Eurasian treecreepers Certhia familiaris divide their territories spatially during the breeding season. Females forage primarily on the upper parts of the tree trunks, while males use the lower parts of the tree trunks. In this study we removed males from eight territories in the early nestling period to see if the mate's absence would change the foraging patterns of the resident female. Widowed females foraged at lower heights, thus behaving more like paired males. These females also spent less time on each tree and on each foraging bout than did paired females. We conclude that male removal facilitated the change in a female's foraging niche and foraging time at the trees. Females may re-optimize their foraging site selection owing to the absence of dominant males and a consequent need to increase their parental care. Behavioral plasticity may be the mechanism of niche partitioning between the sexes in this species. Received: 28 June 1996 / Accepted after revision: 27 March 1997     

Do brain parasites alter host personality? — Experimental study in minnows

Despite that the existence of animal personalities is widely recognized, no consensus has been reached on the relative importance of different ecological factors behind their expression. Recently, it has been suggested that parasites may have a crucial role in shaping animal personalities, but only a very few studies have experimentally tested the idea. We infected Eurasian minnows (Phoxinus phoxinus) with the brain-encysted trematode parasite, Diplostomum phoxini, and studied whether infection could modify the personality of their hosts. Our results show that D. phoxini infection did not affect the mean levels of boldness, activity or exploration, but infected minnows showed higher repeatability in boldness and activity, and reduced repeatability in exploration. We also found that D. phoxini may be able to break the associations (behavioral syndromes) between behavioral traits, but that this effect may be dependent on parasite intensity. Furthermore, the effect of D. phoxini infection on personality of the hosts was found to be nonlinearly dependent on infection intensity. Taken together, our results suggest that D. phoxini parasites may shape the personality of their hosts, but that behavioral consequences of ecologically relevant infection levels may be rather subtle and easily remain undetected if only the mean trait expressions are compared.     

Contribution of winter to the annual CH4 emission from a eutrophied boreal lake

The springtime methane (CH4) emission from a small, eutrophied boreal lake was assessed during the winter ice-cover by measurement of gas ebullition and CH4 accumulation in the water column in association with the development of oxygen depletion after ice formation. The winter CH4 production was estimated to result in a loss of 3.6-7.9 g CH4 m(-2) from the lake to the atmosphere during the short period of ice melt. This could account for 22-48% of the annual CH4 emission from the pelagic zone of the lake. The contribution of winter to the annual CH4 release can be similar or even higher in seasonally ice-covered northern aquatic ecosystems than in northern terrestrial wetlands, thus winter must be considered in any studies into the aquatic CH4 emissions. The trophic state and wintertime oxygen conditions, linked to the changes in land-use in the catchments and climate, are important factors controlling the springtime lake CH4 emissions.     

Food chain enrichment of organochlorine compounds and mercury in clean and polluted lakes of Finland

Lakes polluted by pulp mill and urban wastes including chlorobleaching of pulp, semipolluted lakes and reference lakes in nearly natural condition in Central Finland were studied for contents of mercury, methyl mercury and organochlorine compounds in sediment, plankton, roach and pike. Chlorobleaching had caused a 30-fold concentration of Hg in bottom sediment related to that of the purest reference lake. This was not reflected to the mercury levels in fish which were highest at one natural condition (humic) lake and rather high also at semipolluted lake Päijänne. Mercury in fish was shown to be mostly methylated but not completely and its time trends could be estimated. Chloroform showed no but carbon tetrachloride, tetrachloroethylene and chlorinated cymenes significant bioaccumulation in fish. Levels of chlorophenols from bleaching had strongly decreased but pentachlorophenol and 2,3,4,6-tetrachlorphenol levels remained related to earlier results. Using fat basis attenuated the power of estimation of food chain enrichment by a three throphic level model for lipohilic biocides and a strong proof was obtained of the enrichment of hexachlorobenzene. The time trends at Päijänne were decreasing for mercury and DDE but increasing for PCB.     

Fluxes of methane,carbon dioxide and nitrous oxide in boreal lakes and potential anthropogenic effects on the aquatic greenhouse gas emissions

We have examined how some major catchment disturbances may affect the aquatic greenhouse gas fluxes in the boreal zone, using gas flux data from studies made in 1994-1999 in the pelagic regions of seven lakes and two reservoirs in Finland. The highest pelagic seasonal average methane (CH(4)) emissions were up to 12 mmol x m(-2) x d(-1) from eutrophied lakes with agricultural catchments. Nutrient loading increases autochthonous primary production in lakes, promoting oxygen consumption and anaerobic decomposition in the sediments and this can lead to increased CH(4) release from lakes to the atmosphere. The carbon dioxide (CO(2)) fluxes were higher from reservoirs and lakes whose catchment areas were rich in peatlands or managed forests, and from eutrophied lakes in comparison to oligotrophic and mesotrophic sites. However, all these sites were net sources of CO(2) to the atmosphere. The pelagic CH(4) emissions were generally lower than those from the littoral zone. The fluxes of nitrous oxide (N(2)O) were negligible in the pelagic regions, apparently due to low nitrate inputs and/or low nitrification activity. However, the littoral zone, acting as a buffer for leached nitrogen, did release N(2)O. Anthropogenic disturbances of boreal lakes, such as increasing eutrophication, can change the aquatic greenhouse gas balance, but also the gas exchange in the littoral zone should be included in any assessment of the overall effect. It seems that autochthonous and allochthonous carbon sources, which contribute to the CH(4) and CO(2) production in lakes, also have importance in the greenhouse gas emissions from reservoirs.