Small Oligotrophic Lake Research Articles

Elemental analysis of non-living particles in picoplankton fractions from oligotrophic lake water

Electron microscopic (TEM) study of bacterial-sized planktonic fractions recovered from the water column samples of a small oligotrophic lake, consistently showed the presence of non-living organic and inorganic particles as prominent parts of the micro habitat. An all important objective of this work was to determine the composition and possible origins of the minute particles. They were of several morphological types, described by transmission electron microscopic (TEM) appearance as: spherical, oblong, cuboidal, plates and fibrillar. The TEM used in the scanning transmission mode (STEM) in conjunction with the Princeton Gamma Tech (PGT) System 4 energy dispersive X-ray spectrometer (EDX) allowed the determination of the elemental composition of individual particles. The particles referred to as spherical were electron dense and were less than 1 μm in diameter. They were mainly composed of either Fe or Ti but not both. Cuboidal iron particles 37–75 nm in diameter were found in about equal abundance, but they were arranged in chains of individuals. Oblong particles were from 0.18 to 0.2 nm in width to 0.2 to 0.45 μm in length. Most were composed mainly of Ca, S and O but other elemental compositions were observed also. Plates with jagged edges composed of Al and Si were somewhat electron transparent. Both were less than 1 μm in largest dimension. Fibrillar particles were most abundant and were composed of Fe, Si, Cl, K, Na, O and C. They ranged from 90 Å to 37 nm in thickness and 1 μm to several μm in length. Particles of planktonic origin were observed with regularity including fragments of diatom cell walls and scales. These particles were composed of Si and O. Hexagonally shaped virus-like particles of several sizes were observed also. The relationship between elements in micro particles and their possible origins are discussed.

Wind-determined sediment distribution and Holocene sediment yield in a small, Danish, kettle lake

Sediment distribution was mapped by multiple corings in a small oligotrophic lake in northwestern Denmark. Sediment cores along a representative West-East transect were dated by 14C and correlated using pollen, mineral magnetics and general lithology. Estimates of whole-lake Holocene sediment accumulation were used to calculate sediment yield (terrestrial erosion). Results indicate that: 1) sediment yield was low 10000–5000 BP and increased strongly 5000–2500 BP and again 2500–1200 BP, 2) sediment focusing and waves and currents induced by strong winds were the major processes controlling sediment distribution throughout the Holocene; 3) the dominant wind direction of strong winds has been westerly throughout the Holocene; and 4) the lake was probably more productive in the last 5000 years than in the period from 10000 to 5000 BP.

Response of Amphipoda and Trichoptera to Lake Fertilization in the Canadian Arctic

Small oligotrophic lakes at Saqvaqjuac, Northwest Territories, were fertilized with phosphorus and nitrogen after 2 yr of study and the response of macroinvertebrates to increased primary production was followed for 3 yr. The amphipod Gammarus lacustris lacustris (G. O. Sars) had a 2-yr life cycle, with three cohorts present in August. Biomass under natural conditions was approximately 0.1–0.2 g dry wt∙m−2. Gammarus responded immediately to a doubling of phytoplankton production with increased survival of young-of-year. Gammarus biomass increased steadily to 0.9 g dry wt∙m−2 and had not stabilized after 3 yr of fertilization. Trichoptera were represented by three species, with Grensia praeterita composing the bulk of the biomass, followed by Apatania zonella and an uncommon Hesperophylax species. Trichoptera biomass ranged from 0.04 to 0.3 g dry wt∙m−2 before fertilization. Response to increased primary production was slow, beginning in year 2 of fertilization. Trichoptera biomass had doubled by the third year of fertilization but was probably several years from equilibrium. Application of benthos models, in addition to the data, suggested that the production to biomass ratio was between 1 and 2, averaging 1.5.

An electron microscopic study of picoplanktonic organisms from a Small Lake

Picoplankton, both prokaryotic and eukaryotic, are distinguished from other aquatic organisms by their small size (0.1-2.0 μm). Such organisms were recovered from waters of a small oligotrophic lake using screens, filters, and high-speed centrifugation. The majority of the picoplankton were unable to form visible colonies on common media. Cells examined in thin sections by electron microscopy showed that 60-75% of the cells had an average diameter after dehydration of 0.48-0.51 μm. The maximum dimensions of the rest of the cells ranged from 0.56-1.81 μm. Using details of ultrastructure, cells were classified as prokaryotic or eukaryotic. Phototrophs present included two cyanobacterial morphotypes (5-6%) and two eukaryotic algae (less than I%). The arrays of intracytoplasmic membranes in 18-20% of the cells were suggestive of methanotrophic rods and chemoautotrophs. Relatively few prosthecate bacteria were observed in the water column samples. The smallest cells (1-2%) contained magnetosomes, the presence of which were confirmed by x-ray spectroscopy. Iron was also detected in the envelopes of some rod shaped cells by the same technique. The study of in situ picoplankton populations using TEM coupled with other techniques may provide better understanding of picoplankton biomass.

Interactions between Two Distantly Related Species, Brook Trout (Salvelinus fontinalis) and White Sucker (Catostomus commersoni)

We compared spatial distribution and food habits of an allopatric brook trout (Salvelinus fontinalis) population to one living sympatrically with white sucker (Catostomus commersoni) in two small oligotrophic lakes. Small brook trout (< 20 cm) of both sympatric and allopatric populations were more abundant in the littoral than in the offshore zone whereas large [Formula: see text] were found equally in both habitats in May. From June to August, small and large trout from both populations shifted to the offshore zone; this shift was more pronounced for small sympatric trout. Allopatric trout fed mainly on zoobenthos whereas sympatric trout fed mainly on zooplankton except small ones which ate mostly zoobenthos during May and June. White sucker (< 20 and [Formula: see text]) were generally found in the littoral zone, feeding mainly on zoobenthos. These results suggest that brook trout shifted their spatial distribution and/or their feeding habits in the presence of white sucker and that the nature of these interactions varied according to fish size. Diet overlap between trout and sucker was the lowest when the biomass of benthic prey in the littoral zone was lowest (July), indicating that the intensity of interaction among these species varies according to the abundance of food resources.

Comparative Ecology and Behavior of Domestic, Hybrid, and Wild Strains of Brook Trout, Salvelinus fontinalis, after Stocking

Two years after planting in six small oligotrophic lakes, domestic, hybrid and wild strains of brook trout, Salvelinus fontinalis, used space and food resources in the same way as native trout. Although trout living with or without white sucker, Catostomus commersoni, were similarly spatially distributed, they had different diets, suggesting a feeding niche shift of trout in the presence of sucker; we concluded that this shift is under phenotypic control because each planted strain came from similar genetic backgrounds. Sexual maturity was related to the size of individuals, regardless of the strain, and males matured before females. Almost all males and females were sexually mature in the first fall after stocking except wild females (3.0 and 75% matured during the first and second fall, respectively). Gonadosomatic indices (GSI) of domestic and hybrid females were similar during the first fall, but the GSI of domestic females was significantly higher than that of hybrid and wild strains in the second fail. Mean egg diameters were similar among the three strains during the two falls, but fecundity of domestic females, after correction for size differences, was significantly higher than that of hybrid females which, in turn, was significantly higher than that of wild ones.

Performance of Domestic, Hybrid, and Wild Strains of Brook Trout, Salvelinus fontinalis, after Stocking: the Impact of Intra- and Interspecific Competition

Wild and hybrid strains of brook trout, Salvelinus fontinalis, showed better rates of recovery (by angling) and yield (kilograms of fish recovered per kilogram planted) than a domestic strain, during the 2 yr following planting, in six small oligotrophic lakes of the Laurentian Shield. Native brook trout and white sucker, Catostomus commersoni, had a significant impact on planted brook trout. Recovery, percent of increment in weight and yield of each planted strain were inversely correlated with (1) the relative abundance of native brook trout, and (2) the occurrence of white sucker, supporting hypotheses of intra- and interspecific competition. Furthermore, the response variables were also inversely correlated with the number of potential competitors, indicating that the impact of native brook trout and white sucker was additive. The recovery in number of planted trout (both years and all strains) was approximately four times higher in lakes with effectively no competitors than in lakes containing both white sucker and native brook trout; the increase in weight was nearly three times higher, and the yield was more than nine times higher. The performances of planted fish were intermediate in the lake containing only native brook trout as competitor.

Diel onshore–offshore migrations in northern redbelly dace, Phoxinus eos (Cope), in relation to prey distribution in a small oligotrophic lake

Northern redbelly dace, Phoxinus eos (Cope), exhibit diel onshore–offshore migrations in a small oligotrophic Quebec lake. The fish swim in shoals in the littoral zone during the day, migrate to the pelagic zone at sunset, where the shoals break up into single fish, and then go back to the littoral zone at sunrise. Dace eat mainly two cladocerans, Daphnia and Holopedium. Zooplankton sampling indicated that Daphnia were significantly more abundant in the pelagic zone than in the littoral zone, and Holopedium were rarely found in the littoral zone. Dace showed a significant preference for a dense cover habitat over a sparse cover habitat in the littoral zone during the day. Our results support the hypothesis that dace migrate to the pelagic zone at sunset to increase their feeding efficiency on zooplankton. The foraging benefits of remaining in the offshore zone may be offset by increased risk of predation by brook charr, Salvelinus fontinalis (Mitchill), during the daylight hours, thus resulting in diel onshore–offshore migrations.

Pu Residence Times in Freshwaters and Accumulation in Shield Lake Sediments

Activity balances for 239,240Pu in seven oligotrophic lakes were constructed from measurements of 239,240Pu inputs and measurements of 239,240Pu accumulated in the lake sediments. 239,240Pu eroded from the catchment was a significant input to lakes with rapid hydrologic flushing rates. From 28 to 100% of the 239,240Pu input to the lakes accumulated in the lake sediments. The fraction of 239,240Pu inputs accumulated in the lake sediments was inversely correlated with the hydrologic flushing rate of the lake. 239,240Pu concentrations in the sediments were simulated using a single reservoir input–output model. Partial residence times for 239,240Pu transfer from the water to the sediments ranged from 0.09 to 2.7 yr and were shorter in lakes with more rapid flushing. Partial residence times of 239,240Pu in these small shield lakes were very similar to the residence times of 239,240Pu in the Laurentian Great Lakes and to those of 137Cs and 210Pb in other small oligotrophic lakes.

Occurrence of sphagnum moss in the sublittoral of several small oligotrophic lakes in Galloway, Southwest Scotland

Comparison between historical and contemporary aquatic macrophyte data indicates that since 1905 Sphagnum moss has become established in the sublittoral of several oligotrophic lakes (lochs) in Galloway, southwest Scotland. This floristic change is broadly similar to that reported from some recently acidified lakes in Scandinavia and The Netherlands. It is possible that catchment afforestation and associated preparatory ploughing in particular, may encourage the establishment of sublittoral Sphagnum and consequently influence floristic changes in acidifying lakes.

Survival and Growth of Stocked Lake Trout in Relation to Body Size, Stocking Season, Lake Acidity, and Biomass of Competitors

Abstract Juvenile, hatchery-reared lake trout Salvelinus namaycush, 25–36 months old, were stocked (about 24 fish/hectare) in six small oligotrophic lakes to test the effects of fish size, stocking season, and lake water acidity on survival and growth of introduced fish. The test lakes had few, if any, native lake trout. Little or no survival of stocked lake trout occurred in lakes with pH 5.0 or less. High survival and growth occurred in intermediately acidic (pH 5.6–6.1) and circumneutral (pH 6.9–7.3) lakes. Survival of stocked lake trout increased with size at the time of stocking. Size differences of the three size-classes introduced in each lake were maintained throughout the 2-year study. Competition with other resident fish species appeared to influence stocking success strongly. There was an inverse relationship between the biomass of stocked lake trout subsequently recaptured and biomass of all hypolimnefic species present in the lake. Intraspecific competition with previously stocked lake trout ...

Paleolimnology of a small oligotrophic lake on Wolin Island, Baltic Sea, Poland

Paleolimnological studies which included analyses of diatoms, fossil pigments and physico-chemical characteristics of bottom sediments have been used to describe the limnological history of Racze Lake. The influx of terrigenous material into the lake have been determined on the basis of stratigraphy of elements associated with mineral content. The successively eroded soils as well as process of chemical erosion caused increase leaching of metals Mg, Fe, Al into the lake basin. However the concentration of these metals finally deposited in bottom sediments was also effected by the oxygen regime at the sediment-water interface. Both ratios, chlorophyll derivatives to total carotenoids (CD:TC) and Fe:Mn indicated hypolimnetic oxygen depletion in the middle part of the profile. The development of blue-green algal population, estimated by the ratio epiphasic to hypophasic carotenoids (EC:HC) was correlated with periods of redox conditions in the lake. The pH changes ranged from 6.5 to 7.7. The most important factors effecting pH changes were inflow of mineral matter from the watershed and structural changes in the littoral biocenosis.

Persistence of Bacillus Thuringiensis serovar. Israelensis toxic activity in the environment and interaction with natural substrates

The persistence of Bacillus thuringiensis serovar. israelensis (B.t.i.) toxic crystals was studied using environmental chambers filled with a commercial formulation of B.t.i. and natural substrates found in field treatment conditions. The chambers were kept near the bottom of a small oligotrophic lake. In cold waters, toxicity remained stable at least 21 days in the presence of lake water. The presence of solids substrates produced a rapid loss of toxicity. This was caused in part, by interactions between the substrates and the larvicidal crystals of B.t.i.. Toxicity reached a low point between day 43 and 69 and increased thereafter, except for the samples containing organic sediments. This increase in toxicity could be correlated with the behavior of the spore and viable cell counts of B.t.i., in the chambers. These counts indicated that in cold temperate climates, B.t.i. could sporulate and release new crystals.

Relationship of Crayfish (Orconectes virilis) Growth to Population Abundance and System Productivity in Small Oligotrophic Lakes in the Experimental Lakes Area, Northwestern Ontario

Crayfish growth in four lakes in the Experimental Lakes Area (ELA) was examined by analysis of size-frequency distributions, molt increment data, and calculation of instantaneous growth and mean size at onset of sexual maturity. Orconectes virilis growth rates at ELA are only 27–38% of those reported for other areas. Growth varied both among study lakes and between years. Higher temperatures and a longer growing season during 1980 increased growth an average of 12% over that of the preceding year. Crayfish growth and maximum size in four to six lakes were significantly correlated with phytoplankton production and chlorophyll a concentration. Growth regulated both the number of age 1 animals attaining sexual maturity and the per capita egg production, and was also directly related to the proportion of mature females that were fertilized. I believe population regulation is mediated through alterations in reproductive capacity that is correlated with system productivity.

Summer Distribution of Zoobenthos in Grane Langsø, Denmark

The fauna inhabiting the substrate in a small oligotrophic lake, Grane Langsø, Denmark was sampled during July 1977, along a 100 m transect extending from shoreline to 11 m depth. This transect passed through two vegetative and two mud zones. A total of 79 taxa were identified using two sampling techniques. Most taxa showed a habitat preference for either mud or vegetative substrates. Among the animals inhabiting the vegetative substrates, we detected 4 distinct groups -- organisms that had peak numbers in shallow water (<0.5 m), another group that was abundant in the deeper zone (6.3-10.2 m), and two other groups that had peak abundance in or near the plant boundaries of either the upper or lower zone. Peaks in diversity and abundance were found at 0.5 m, and at the lower boundary of both vegetative zones. The peak at 0.5 m corresponded to maximum plant biomass and a morphometric discontinuity.

Allochthonous plant litter as a source of organic material in an oligotrophic lake (Llyn Frongoch)

The importance of airborne plant litterfall as a source of organic material was evaluated for a small oligotrophic lake. The airborne plant litter input was estimated to be 100 kg yr−1 (45 kg C. yr−1), which represents approximately 5% of the phytoplankton productivity. The quantity of plant litter entering the lake followed an exponential decline with distance from the shore.

Initial impacts of experimental fish introductions on the macrozooplankton of small oligotrophic lakes

(1978). Initial impacts of experimental fish introductions on the macrozooplankton of small oligotrophic lakes. SIL Proceedings, 1922-2010: Vol. 20, No. 3, pp. 2003-2012.

The helminths in the gut of perch (Perca fluviatilis L.) in a small oligotrophic lake in southern Norway.

A total of 311 perch were examined for gut parasites during the period from April 1972 to December 1973. Four different metazoan parasites were found; Proteocephalus percae (Müller, 1780), Bunodera luciopercae (Müller, 1776), Acanthocephalus lucii Müller, 1776 and Camallanus lacustris Zoega, 1776. B. luciopercae and P. percae exhibited similar seasonal cycles in appearance and abundance. They were both absent from the fish population during June/July. A. lucii and C. lacustris on the other hand had a peak in infection intensity and incidence during the summer and autumn months. From September/October one year to May/June the following year B. luciopercae was the dominating parasite species showing the highest incidence (approximately 95%) and intensity (a mean of about 25 parasites per infected fish). When 2 times 2 contingency tests were applied on the material from this period a significant negative correlation between the presence of P. percae and A. lucii could be pointed out while there was no correlation between the presence of any of the other 3 parasite species.

A sampling device for the invertebrate fauna of aquatic vegetation

SUMMARY. A sampler designed to provide a quantitative estimate of the benthic invertebrates of littoral/sub‐littoral zones dominated by Sphagnum moss is described. Data obtained from a small oligotrophic lake at a depth of 1 m using this sampler are presented. Optimum sample size was determined and samples comprising five sampling units were found to be adequate in terms of the number of invertebrate species present and their relative abundance. Similarity of such samples was greater than 90%.

Factors relating to annual planktonic primary production in five small oligotrophic lakes in Terra Nova National Park, Newfoundland

AbstractAnnual planktonic primary production in five small oligotrophic lakes in Newfoundland, as measured at maximum depth (P‐area) ranged from 5.6 to 12.0 g C/m2/year. Production per unit surface area representative of the whole lake basin (P‐area ) was considerably lower in the shallower lakes (3.3 to 6.4 g C/m2/yr), while production expressed per unit volume representative of the whole lake basin (P‐vol ) was the higher in the shallower lakes (0.6 to 4.1 g C/m3/yr). Production efficiency varied from lake to lake and throughout the year, but it remained fairly stable in a shorter term. Production efficiency and insolation was used to estimate annual production. Lakes with higher summer concentration of total phosphorus had higher rates of carbon assimilation.