Warm Monomictic Lake Research Articles

Late Cenozoic lacustrine and climatic environments at Tule Lake, northern Great Basin, USA

Cores of lake sediment to a depth of 334 m in the town of Tulelake, Siskiyou County, northern California, document the late Cenozoic paleolimnologic and paleoclimatic history of the northwestern edge of the Great Basin. The cores have been dated by radiometric, tephrochronologic and paleomagnetic analyses. Lacustrine diatoms are abundant throughout the record and document a nearly continuous paleolimnologic history of the Tule Lake basin for the last 3 Myr. During most of this time, this basin (Tule Lake) was a relatively deep, extensive lake. Except for a drier (and cooler?) interval recorded by Fragilaria species about 2.4 Ma, the Pliocene is characterized by a dominance of planktonic Aulacoseira solida implying a warm monomictic lake under a climatic regime of low seasonality. Much of the Pleistocene is dominated by Stephanodiscus and Fragilaria species suggesting a cooler, often drier, and highly variable climate. Benthic diatoms typical of alkaline-enriched saline waters commonly appear after 1.0 Ma, and tephrochronology indicates slow deposition and possible hiatuses between about 0.6 and 0.2 Ma. The chronology of even-numbered oxygen isotope stages approximately matches fluctuations in the abundance of Fragilaria since 800 ka indicating that glacial periods were expressed as drier environments at Tule Lake. Glacial and interglacial environments since 150 ka were distinct from, and more variable than, those occurring earlier. The last full glacial period was very dry, but shortly thereafter Tule Lake became a deep, cool lacustrine system indicating a substantial increase in precipitation. Aulacoseira ambigua characterized the latest glacial and Holocene record of Tule Lake. Its distribution indicates that warmer and wetter climates began about 15 ka in this part of the Great Basin. Diatom concentration fluctuates at 41 000 year intervals between 3.0 and 2.5 Ma and at approximately 100 000 year intervals after 1.0 Ma. In the late Pliocene and early Pleistocene, Aulacoseira solida percentages wax and wane in an approximately 400 000 year cycle. The possible response of Tule Lake diatom communities to orbitally-induced insolation cycles underscores the importance of this record for the study of late Cenozoic paleoclimate change.

Modern and Holocene carbonate sedimentology of two saline volcanic maar lakes, southern Australia

ABSTRACTThe Basin Lakes are two adjacent maar lakes located in the centre of the Western Volcanic Plains District of Victoria, Australia. Both lakes are saline and alkaline; West Basin Lake is meromictic whereas East Basin is a warm monomictic lake. The carbonate mineral suite of the modern offshore bottom sediments of these Basins consists mainly of dolomite and calcite, with smaller amounts of hydromagnesite and magnesite in West Basin and monohydrocalcite in East Basin. The dolomite, hydromagnesite, magnesite, and monohydrocalcite are endogenic in origin, being derived by primary inorganic precipitation within the water columns of the lakes or at the sediment‐water interface. The calcite is biologically precipitated as ostracod valves.In addition to the carbonates in the modern offshore (deep‐water) sediments, the lakes also contain a girdle of nearshore carbonate hardgrounds. Both beachrock and microbialites (algal boundstones) are present. These modern lithified carbonate units exhibit a wide range of depositional and diagenetic fabrics, morphologies and compositions. In West Basin, the hardgrounds are composed mainly of dolomite, hydromagnesite, and magnesite, whereas dolomite and monohydrocalcite dominate the East Basin sediments. Aragonite, high‐Mg calcite, kutnahorite, siderite, and protohydromagnesite also occur in these lithified carbonate units.Stratigraphic variations in the carbonate mineralogy of the Holocene sediment record in the lakes were used to help decipher the palaeochemistry and palaeohydrology of the Basins. These changes, in conjunction with fluctuations in organic remains and fossil content, indicate a pattern of lake level histories similar to that deciphered from other maar lakes in western Victoria.

Modifications in habitat use patterns and trophic interrelationships in the fish fauna of an oligotrophic artificial lake: Sainte Croix (Provence, France)

Lake Sainte-Croix is a hydro-electric reservoir on the river Verdon that came into operation about 16 years ago. The area of the lake is about 22 km2 and the volume about 767 Mm3. The water level drops by as much as 16 m in winter. Sainte-Croix is a warm monomictic oligotrophic lake. The indigenous fish fauna of the Verdon originally included 8 species. Successive stocking has raised this number to 17. In catches made in 1976–1977 with 27 mm mesh nets, 80 to 90% of the fish with a body size of between 15 and 25 cm were of the four main species indigenous to the river before the dam was built: Leuciscus cephalus, Barbus fluviatilis, Chondrostoma toxostoma, Salmo trutta. Catches made at same period with 14 mm mesh nets gave only Chondrostoma toxostoma and Leuciscus cephalus. Changes in the fish fauna were apparent from catches made in 1984 and 1987 with nets of the same mesh size. There was a marked demographic increase of roach, and more recently of bleak and gudgeon, all three species introduced after the construction of the dam. At the same time, there was a decrease in catch frequency of Ch. toxostoma, L. cephalus and B. fluviatilis in the downstream area of the lake. Stomach content analysis carried out in different seasons on the six most abundant species of the lake (roach, toxostome, chub, bleak, perch and gudgeon) provided evidence on the trophic organisation of the fish fauna. We have measured niche breadth for each species by the Simpson diversity index and niche overlap by the Pianka index. Bleak is the only species to feed on zooplankton in open water. Roach is a particularly opportunistic feeder, sometimes taking plankton, but at Sainte-Croix it is exclusively herbivorous and benthophagous. Niche overlap between these two species is slight or null, depending on the season. On the other hand, there is a high degree of overlap between roach and chub and between roach and toxostome. The decrease in toxostome and chub frequency in the downstream area of the lake, where roach is most abundant, would appear to be a competitive exclusion phenomenon. There is high niche overlap between bleak and young perch, which partly explains the low abundance of the latter species; other contributory factors are the scarcity of zooplankton inshore, and the scarcity of zoobenthos resulting from the drop in the water level in winter.

Algal picoplankton production and contribution to food-webs in oligotrophic British Columbia lakes

The pelagic communities of two contrasting oligotrophic lakes in British Columbia were studied to determine why an interior, dimictic lake (Quesnel) supports a greater biomass of zooplankton and produces larger planktivorous sockeye salmon (Oncorhynchus nerka) than a coastal warm-monomictic lake (Sproat). The ultra-oligotrophic status and differing planktivore densities in Sproat Lake increased the relative importance of algal picoplankton, diminished the abundance of large zooplankton, and increased the significance of rotifers and other small-bodied zooplankton. These picoplankton based food webs result in longer, indirect and less efficient pathways of carbon flow from phytoplankton to fish. In contrast, Quesnel Lake is a more productive oligotrophic lake and its pelagic food webs are based more on nanoplankton and small microphytoplankton that support larger-bodied zooplankton (Daphnia, Diaptomus), and a more direct and efficient two-step transfer to fish. The greater variability of the annual recruitment of sockeye fry in interior lakes may keep zooplankton communities in a non-steady state, this in turn may perpetuate the occurrence of quadrennial cyclic dominance in adult salmon returning to these systems.

Bacterioplankton, Phytoplankton, and Zooplankton Communities in a British Columbia Coastal Lake Before and After Nutrient Reduction

Inorganic nitrogen and phosphorus were applied weekly during the growing season from 1980 to 1982 and twice weekly in 1983 to Hobiton Lake, a warm monomictic coastal lake in British Columbia. The lake was not fertilized in 1984. Average numbers of bacteria during the growing season decreased from a high of 1.53 × 106∙mL−1 in the fertilized condition to 0.84 × 106∙mL−1 in the unfertilized condition. Chlorophyll a concentrations decreased from a maximum seasonal average of 2.69 μg∙L−1 (1981) to 1.30 μg∙L−1 (1984), and algal numbers decreased from 5.83 × 104∙mL−1 (1983) to 2.29 × 104∙mL−1 (1984). Although the numbers of phytoplankton in each size fraction (picoplankton, nanoplankton, or microplankton) decreased in the unfertilized condition, the greatest change was an almost fourfold decrease in picoplankton, which consisted of 90% cyanobacteria (primarily Synechococcus spp.). Abundance of the large diatoms Rhizosolenia spp. and Melosira spp. increased in 1984, resulting in an increase in average seasonal algal volume. Average densities of medium (0.15–0.84 mm) and large (0.85–1.5 mm) zooplankton were greatest in 1982, while rotifers and small zooplankton (0.10–0.14 mm) were most dense in 1984 following nutrient reduction. The lake had relatively high concentrations of planktivorous juvenile sockeye salmon (Oncorhynchus nerka) that appeared to minimize any direct effect of nutrient additions on zooplankton densities.

Vertical distribution of potentially pathogenic free-living amoebae in freshwater lakes.

The vertical distribution of thermotolerant (37 degrees C and 45 degrees C) free-living amoebae (FLA) in warm monomictic lakes was determined in relation to the onset of thermal stratification and associated physical and chemical changes. The position of abiotic or biotic particulate layers in the water column was located by using a submersible horizontal beam transmissometer that measures attenuance, or the absorption and scattering of light by particulates in the water column. During mixis, the vertical distribution of amoebae was sporadic with significant numbers of FLA only occurring in clay layers caused by runoff after heavy rains. With the onset of thermal stratification in the lakes, phytoplankton layers began to form. Few amoebae were isolated from layers containing flagellated phytoplankton; however, significant (P less than 0.005) numbers of FLA were isolated from two particulate layers dominated by the filamentous blue-green algae Aphanizomenon and Lyngbya, respectively. By late June, a persistent detrital or decomposition layer formed in the lower metalimnion, as well as a hypolimnetic iron layer where the Fe2+ state was predominant. In this midsummer period, 13 Naegleria fowleri were isolated, with three from the detrital layer and seven from the iron layer. The presence of attenuation zones was found to be the best indicator of the vertical distribution of FLA in the water column, and such layers represent an important, previously undescribed habitat for potentially pathogenic FLA.

Aspects of the limnology of Lake Rotongaio

Abstract Lake Rotongaio, a warm monomictic lake, was sampled at monthly intervals for 1 year to investigate water temperature, transparency, chemistry, zooplankton, and benthic macroinver‐tebrates. Phytoplankton composition and standing crop represented by concentration of chlorophyll a, were measured for 6 months. Secchi disc values were always less than 2 m because of the large standing crops of algae dominated throughout the year by Anabaena oscillarioides. The major ion composition of the lake water indicated a source typical of a pumice aquifer. The average concentration of dissolved reactive phosphorus during the circulation period was 275 mg m‐3 and the average reactive N:P ratio was 0.55. The decline in concentration of inorganic N during the breakdown of thermal stratification could not be accounted for by mixing, and 606 kg or 6.71 mg m‐3d‐l of inorganic N was lost from the lake. The zooplankton comprised rotifers (57%), crustaceans (34%), and ciliates (9%). There was 1 species of calanoid copepod, 2 species of cladocera, and 6 species of rotifer. Ninetyone percent of the benthic macroinverte‐brates were chironomids; the rest were other insects, oligochaete worms, and molluscs.

Structure and function of a warm monomictic lake

Abstract Construction and simulation of a model of Lake Conway, Florida, U.S.A., provided a framework for defining major characteristics of this ecosystem. The relationships that are formalized in this model comprise a set of hypotheses about the nature of a warm monomictic lake. The data that were used to parameterize the model came primarily from literature estimates, although approximations of biomass levels were available from associated research conducted on the lake. Submersed macrophytes are a major biomass component in Lake Conway; simulation suggested that their role in nutrient recycling overshadows their importance in the grazing food chain. Phytoplankton biomass and degree of fluctuation are considerably lower than are observed in most cool temperate lakes, although simulated respiration and herbivory rates are closer to temperate values than tropical values. Simulated epipelic algae biomass varies an order of magnitude during the year, and this group appears to be a significant part of the food chain. Simulated zooplankton consumption and turnover rates are very high, in part because of the relatively small biomass per individual. Simulation of the model suggests that slightly more carbon is processed through the grazing food chain in Lake Conway than through the detritus food chain.

Bottom sediments of Lake Rotoma

Abstract Lake Rotoma is a deep (70–80 m), oligotrophic, warm monomictic lake of volcanic origin with insignificant stream inflow and no clearly defined outflow. For at least 60 years up to 1972 the lake level fluctuated markedly about an overall rising trend of some 6–10 m. Nearshore profiles are related to the prevailing wave climate superimposed upon the overall rising lake level, shelves being wider, less steep, and deeper about the more exposed eastern and southern shorelines. The outer portions of shelves extending well below modern storm wave base into waters as deep as 15–25 m are relict features from lower lake level stands. Sediments fine from sand‐gravel mixtures nearshore to silts in basinal areas. Their composition reflects a composite provenance involving the lavas and tephras about the lake, as well as intralake diatom frustules and organic matter. The distribution pattern of surficial bottom sediments is an interplay between grains of both biological and terrigenous origin, supplied present...

Phytoplankton Production and Winter Mixing: Contrasting Effects in Two Oligotrophic Lakes

SUMMARY (1) Two deep oligotrophic lakes in the centre of North Island, New Zealand, shared several limnological features but differed in their seasonal patterns of algal production. (2) Lake Waikaremoana followed, in its thermal stratification, the classic pattern for temperate warm-monomictic lakes. During winter circulation, light availability to the phytoplankton was reduced by a factor of at least 13 relative to that in spring and summer, and there was no increased supply of phosphorus, which later controlled the amount of growth of its phytoplankton. Concentrations of algal biomass and algal production rates were predictably low, but rose rapidly with increased irradiance in spring. (3) Lake Taupo experienced similar thermal stratification and mixing, but concentrations of algal biomass and algal photosynthetic production rose to maxima for the year during winter isothermy when temperatures were at their annual minimum and when mixing extended to the bottom of the lake. Winter circulation brought an increased supply of phosphorus and, more importantly, nitrogen which later controlled the amount of algal growth in the euphotic zone. This increased availability of potentially limiting nutrients offset the effects of low light availability and low temperature. (4) Lake Taupo, and other nearby lakes which behave similarly, form intermediates between temperate lakes with typical winter minima of algal production and many tropical lakes which experience maximum phytoplankton production during storminduced mixing.

Instar development rates and production of three generations of Boeckella dilatata (Copepoda: Calanoida) in a warm-monomictic lake

Instar development rates and production of three generations of <i>Boeckella dilatata</i> (Copepoda: Calanoida) in a warm-monomictic lake

Phytoplankton ecology of Loch Ard, Scotland

The results of the ecological investigation discussed in this paper represent the first seasonal study of the phytoplankton to be carried out in Loch Ard. This body of water is a typical warm monomictic lake, with water temperatures during the period of study ranging from 18.6 to 4.4 °C and oxygen saturation from 68 to 112%. Stratification lasted from May to November. Phosphate was generally very low, being almost undetectable for about six months and not exceeding 0.125 µg.at.P 1−1 even at the winter maximum. Dissolved silica showed a regular seasonal pattern ranging from 9 to 21 µg.at.Si 1−1. Nitrate, like silicate, never showed signs of complete exhaustion, with a minimum of 4.0 and a maximum of 21.0 µg.at.N 1−1. The pH remained on the acid side of neutrality while the alkalinity never exceeded 7 mg CaCO3/1. From an examination of net phytoplankton Loch Ard could be described as diatom-desmid in nature. Quantitatively the population was dominated by diatoms(Cyclotella, Asterionella andMelosira) till May whence a mixed population of blue-green algae, desmids and dinoflagellates persisted till late September.

Limnology of Perched Lake, south-west Tasmania

Perched Lake is one of the few lakes of lowland parts of south-west Tasmania. It is a warm monomictic lake, stratifying for 7-8 months each summer and, unlike most other bodies of standing water in the south-west, is only moderately dystrophic. Oxygen concentrations of the hypolimnion decline late in the stratification period but do not fall below 20% saturation, indicating low areal productivity. Though only moderately dystrophic, there is sufficient organic colour to cause marked attenuation of photosynthetically active radiation, particularly in the blue wavelengths. Its water chemistry is that of dilute seawater. Certain thermal and chemical anomalies are possibly explained by subsurface inflows of artesian water. The plankton of Perched Lake is dominated by chrysophytes and chlorophytes, with no well-defined seasonal change of biomass or species composition. An unusual dinoflagellate with marine affinities. probably Phalacroma sp., occurs in the lake.

THE LIMNOLOGY OF SOME SOUTH AFRICAN IMPOUNDMENTS I. THE PHYSICO-CHEMICAL LIMNOLOGY OF HARTBEESPOORT DAM

SUMMARY Hartbeespoort Dam is a eutrophic, warm monomictic lake with overturn occurring in April. The lake is stratified for about six months of the year and in late summer the stratification appears stable. Light penetration in the dam depends both on the inflow of turbid water as well as on the magnitude of the algal population. In summer the surface waters are often super-saturated with oxygen, whilst the hype limnion is anaerobic. The concentrations of nitrogen compounds, phosphate, Na, K, Ca, CI and SO4 are higher in waters entering the dam via the Crocodile River. Nitrogen compounds arc the primary growth-limiting nutrients for algal growth and phosphate is the secondary growth-limiting nutrient. Phosphate concentrations in the water have increased approximately a hundredfold since 1928 and NO3 −N concentrations about threefold. The pH as well as the mineral content of the dam have also increased over the last 50 years.

Physico‐chemical features of lake Ototoa, a sand‐dune lake in northern New Zealand

Abstract Lake Ototoa is a warm monomictic lake at 36° 31’ S, 174° 14'E. During a year's study (March 1969‐March 1970), the lake became thermally stratified in November, the metalimnion being between depths of 12 m and 16 m. Surface temperatures ranged between 10.2°c (in August) and 25.2°c (in late January), and bottom temperatures between 9.7°c and 17.5°c. The annual heat budget was calculated to be 642 354 KJ.m‐2 (15 500 cal.cm‐2) and the work of the wind in distributing the heat income 1.730 KJ.m‐2 (1766 g.cm.cm‐2). Secchi disc transparencies ranged between 5 m and 9.2 m (mean 7.07 m) and were greatest in the summer. Light transmission per metre was also high, ranging between 61% and 87%. Surface waters were normally supersaturated with oxygen, but during summer stratification oxygen concentrations in the bottom waters dropped to a minimum of 2.3 mg.litre‐2 and a positive heterograde distribution of oxygen with depth was found. The oxygen deficit was 0.015 mg.cm‐2.day‐1 and showed the lake to be oligotr...

Stratification and biogenic meromixis in Tasmanian reservoirs

Part of the Mersey-Forth hydro-electric scheme, Tasmania, Lakes Rowallan and Barrington are oligotrophic, slightly humic, warm monomictic reservoirs. Their flooded vegetation, shelter and deep V-section lead to pronounced clinograde oxygen profiles despite meagre autochthonous production. With surprising rapidity, Lake Barrington developed a monomolimnetic pool which, when destroyed by severe floods, soon reformed. Though crenogenic and triptogenic elements may participate, principal causes of this partial meromixis are flooded vegetation and basin morphometry. The monimolimnion exhibits unusually large temperature rises and considerable enrichment of such chemical species as iron, manganese, hydrogen suiphide and bicarbonate. Iron is a major factor in the meromixis and largely accounts for marked monimolimnetic rises in electrical conductivity. The sharp upper monimolimnetic boundary is an almost horizontal chemocline, above which the mixolimnion behaves as a warm monomictic lake. Winter ventilation of its hypolimnion is tardy but complete. The monimolimnion is therefore maintained by decomposition and basin morphometry, not climate. Attendant chemical phenomena of prolonged anoxia in hypolimnetic or monimolimnetic water pose alleviable problems when that water is used domestically, industrially or for power generation.

Cayuga Lake: Effects of Exploitation and Introductions on the Salmonid Community

Cayuga Lake, a glacially formed, warm monomictic lake in New York State, has an area of 172.1 km2 and a mean depth of 54.5 m. It now exhibits qualitative signs of eutrophication in phytoplankton composition and aquatic vegetation. However, hypolimnetic oxygen depletion has not changed to any great extent over the last fifty years.Early commercial fisheries were for nonsalmonid species. Whitefish have apparently never been common in the lake, though cisco have at times been abundant. In recent times the lake and rainbow trouts have provided an appreciable sport fishery. The lake trout population is maintained by annual stocking at a level that provides good sport fishing. Natural reproduction is not successful for lake trout, presumably due to siltation of spawning areas.Introduced species appear to have caused some changes in the native fish community. The alewife appears to have replaced the cisco and now is the major forage species in the lake. Other important introductions include the smelt and the sea lamprey. The salmonine populations were built up despite the presence of sea lamprey. Life history information on other species common in the lake is presented.

MORPHOMETRIC CONTROL OF ANNUAL HEAT BUDGETS IN TEMPERATE LAKES1

Annual heat budgets of 71 lakes in the temperate zone are strongly correlated with mean depth and area. Depth and area influences taken together are responsible for an even higher degree of correlation between heat budgets and lake volumes. For lakes of a given volume, the deeper ones of lesser area appear to take up slightly more heat than the shallower ones of greater area. Dimictic lakes exhibit slightly higher heat budgets than warm monomictic lakes of similar size. Heat uptake appears to rise continuously with increasing lake dimensions, though at a decreasing rate, up to the largest dimensions observed.