Lowland Lakes Research Articles

Diatoms of Lake Peipsi-Pihkva: a floristic and ecological review

463 taxa of diatoms have been recorded from the pelagic and littoral plankton, benthos and periphyton of Lake Peipsi-Pihkva. This typical eutrophic plain lake has many common features with large lakes of both Central and North Europe. As to the richness of diatom taxa, L. Peipsi- Pihkva surpasses other eutrophic lowland lakes, which can be explained by the size of this lake, and by the variety of living conditions in it. The list of taxa as well as notes about rare and phytogeographically interesting diatoms are presented.

Geochemistry and anthropogenic inputs of metals in a tropical lake in Venezuela

Lake Valencia is a tropical lowland lake in north-central Venezuela. Lake bottom sediments were collected from 25 locations in April, 1988. At 2 locations water pH, conductivity, dissolved O 2 and temperature were measured at successive depths. After drying, 5 sediment samples were sieved into 5 mechanical fractions. Each was extracted with 1 M HNO 3 and analysed for AI, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb and Zn. The <63 μm fraction of all samples was similarly analysed. Water temperatures declined with depth (1°C/25 m) from approximately 26°C. Conductivity varied little with depth but dissolved O 2 contents indicated anoxic conditions < 25 m. Water pH (8.8–9.4) was consistent with high dissolved carbonates. There was little consistent relationship between grain size and sediment metal contents. Approximate baseline metal contents were calculated from 21 of 25 samples. The average composition of the sediments corresponded to an ideal mixture of shales/carbonate rocks as 0.5–0.7/0.5-0.3. Five samples from alluvial fans near the mouths of rivers traversing urban-industrial zones had compositions different from the other sediments. Generally, Ph, Zn, Ni, Cd and Cu were anthropogenically enriched by factors of 2–16. The major sources of pollutants were identified as domestic and industrial activities affecting the rivers that traverse the lakeside cities of Maracay and Valencia. Sodium, Mg, Ca, Mn and CO 3 − showed natural enrichment arising from carbonate precipitation following a physical mixing of 2 sedimentary components (biogenic carbonate and terrigenous material). Low geochemical mobility of metallic elements in neutral-basic and reducing waters, a processes of bury and mixture of sediments and precipitation of carbonate result in only 10% of the lake area being affected by contamination. Isoline plots of elements in the bottom sediments supported a hypothesis that material mixing, physical transport and carbonate precipitation are the main controls of spatial distribution patterns.

Pleistocene refuge areas and postglacial dispersal of copepods of the northeastern United States

The distribution of common freshwater copepods of the northeastern United States has a marked association with major meltwater drainage systems and coastal marine submergence zones formed during the retreat of the Wisconsinan ice sheet. Postglacial dispersal routes inferred from the deglaciation chronology indicate that zooplankton could have come from several major Pleistocene refuges in the Mississippi Valley, Appalachian Plateaus, and mid-Atlantic Coastal Plain, and from northern locations on the Atlantic Coastal Plain. Contemporary distribution patterns suggest that some species of copepods dispersed primarily in surface waters during advances and retreats of continental glaciers. These include species of the calanoid Skistodiaptomus and the cyclopoid Diacyclops thomasi that occur in coastal lowlands and in lower elevation lakes in mountainous areas that could be flooded by retreating ice-front lakes. There is little evidence, except for inadvertent introductions through human activities, that these species have expanded beyond their original postglacial dispersal boundaries. In contrast, other calanoid and cyclopoid species were widely distributed and are dominant in high-elevation lakes and lowland lakes behind mountain barriers unreachable by species dependent on water transport. These species commonly occur in permanent and temporary ponds and may produce dormant stages that are readily dispersed.

Evidence of the younger dryas in Central America

Three sites provide records that address whether the Younger Dryas was manifest in Central America. Marine records from Barbados and the Cariaco Basin are discussed, as well as possible climatic forcing mechanisms. Sequences from montane La Chonta Bog, Costa Rica, and lowland Lake Quexil, Guatemala, record a temperature decline of 1.5–2.5°C dated between 11,070–10,400 14C years BP and ca. 12,000–10,300 14C years BP, respectively. The record from Lake La Yeguada, Panama, does not include cooling, although significant reorganization of local communities occurred during the Younger Dryas chronozone. Colder tropical SSTs throughout deglaciation contributed to sub-regional climatic variation, more intense monsoonal activity, and cooler air temperatures. However, the temperature reversals are not associated with the coldest tropical SSTs which occurred during meltwater pulses. The temperature reversals appear to be a response to extra-tropical conditions, presumably in the North Atlantic, which suggests that Younger Dryas cooling extended as far south as Costa Rica. In Panama, monsoonal conditions may have blocked cooler temperatures. Precipitation continued to increase throughout deglaciation due to strong forcing by seasonal solar insolation in Central America while desiccation events occurred to the north and south.

Landscape development in northeast Ireland over the last half millennium

The fragmentary documentary evidence from the 18th century which refers to the lowland landscape of the northeast of Ireland describes enclosure by hedges, with extensive areas under arable agriculture in some areas whilst in others scrubby uncultivated conditions predominate. As few palynological studies of deposits from the last 500 years have been conducted in Ireland, almost nothing is known of the development of the lowland landscape.The results from a modern pollen rain study of a reconstructed 19th centuryfarm, characteristics of northeast Ireland, were used to interpret the palynological evidence from lowland lake deposits and peats from approximately the last five hundred years. Scrub clearance in the 18th century resulted in an open landscape which was enclosed by hedges of Crataegus and Prunus spinosa. These hedge taxa are poorly represented in both the modern pollen rain study and the fossil pollen record, as were weeds. An upsurge in arable agriculture in the 18th century included the introduction of flax.

Recent trends in the acid-base status of surface waters in Maine, USA

Data from the EPA Long Term Monitoring Program lakes at the Tunk Mountain Watershed, Maine, indicate that decreases of ≤1 Μeq L−1 yr−1 in SO4, and increases of ≤2 Μeq L−1 yr−1 in ANC occurred in the 1980s. The sum of base cations also increased. These changes in aquatic chemistry were coincident with decreased concentrations of all solutes in precipitation during the 1980s. Other data on lakes and streams in Maine collected between the 1930s and 1990 generally confirm these trends and further indicate that larger increases in ANC may have occurred in some lowland lakes since 1940. Paleolimnologic studies indicate that decreases of 0.1 to 0.5 pH units occurred in a few small mountain lakes during the past 20 to 70 yr. However, ongoing acidification of lakes is indicated based on available data. Only lakes that were already at least marginally acidic (pH ≤5.8, ANC approximately 0) appear to have acidified.

Experimental hybridization of alpine and lowland forms of Boeckella dilatata, a calanoid copepod

The freshwater calanoid copepod Boeckella dilatata Sars inhabits lakes and ponds of glacial origin in central and southern South Island, New Zealand. In lowland lakes and ponds, this copepod is small and transparent while in alpine bodies of water, it is larger and bright red. The life history traits of alpine and lowland populations of this copepod also differ. In this paper we present the results of experimental hybridization between individuals from an alpine and a lowland population. Crosses between a transparent, lowland morph of B. dilatata and a red, alpine morph produced viable F1. Intermorph matings showed no sign of reduced clutch size in either alpine or lowland females. Back- and inter-crossing of the F1 showed that this generation was fertile and that subsequent F2 were viable. Clutch sizes of F1 hybrid females backcrossed to lowland males, however, were significantly smaller than those of females in other F1 crosses; in addition, a high variance in clutch size was observed in all F1 crosses, which is also interpreted as reduced fitness. F1 hybrid breakdown was also apparent from the observation that clutch sizes of females in backcrosses with a parental constitution of 25 per cent alpine were significantly smaller than clutch sizes of females in pure crosses. These observations are attributed to heritable differences in life history characteristics between alpine and lowland populations of B. dilatata. We conclude that the red alpine and transparent lowland morphs of this copepod are best regarded as conspecifics in the early stages of speciation and we discuss the results as they relate to current concepts of speciation. F1 and F2 offspring all showed red pigmentation of similar intensity to the original alpine parental generation and we conclude that either pigmentation in B. dilatata is a polygenic character with dominance or is induced by a factor present in the alpine water.

The morphometry and hydrology of Oak Mere, a lowland kataglacial lake in the north-west Midlands, England

SUMMARY 1. This paper presents geological, climatic, morphometric and hydrological data, collected from 1941 to 1991, on a lowland kataglacial lake and its catchment, as a basis for the development of a descriptive hydrological model. 2. The catchment occupies an area of 2.56 km2, at altitudes of 73–130 m above sea level, and receives an average annual net precipitation of 558 000 m3. The surface geology consists principally of sandy glacial drift and peat overlying Triassic strata which are exposed at the western extremity of the catchment. 3. The mere (lake) has an asymmetrical basin lying in sandy glacial drift and peat. The area (18.4–22.9 ha), depth (7–8 m) and volume (320000–453000m3) fluctuate in relation to net precipitation in at least two ways: an immediate response and a response with a rime lag of approximately 2 years. 4. The pH, normally <5.5 but varying from 4.0 to 7,8, and ionic composition of the mere fluctuate. The evidence suggests that the fluctuation is a response to at least two essentially separate types of water supply: a base-poor surface supply and a base-richer supply entering at a depth of 4m. 5. Essentially, the descriptive model postulates that the mere waters are controlled by a water-table of varying level, in relation to net precipitation, which is base poor at the surface but becomes increasingly base rich with depth.

The relationship between cladoceran body size and the growth of underyearling roach (Rutilus rutilus) (L.) in two shallow lowland lakes: a mechanism for density-dependent reductions in growth

Large planktonic Cladocera are typically the most important components of the diet of underyearling roach. Selection for large species and individuals by fish can result in a shift in the species composition of the cladoceran community as well as a reduction in the mean size of the individuals of large species and in the assemblage as a whole. Laboratory experiments demonstrated that underyearlings feeding on Daphnia hyalina smaller than 1 mm in length has a significantly lower intake of prey volume per unit time than when feeding on prey greater than 1.5 mm. A decrease in the nutritional quality of zooplankton prey, brought about by increasing predation pressure is suggested as the mechanism for density-dependent reductions in the growth of underyearling roach in eutrophic water bodies.

Potential effects of greenhouse warming on freshwater systems in the U.K. with special reference to coastal lowlands

There are two major potential effects of rising atmospheric temperature on freshwater wetlands: direct effects, and indirect effects of rising sea level. Direct effects are varied, but muted by the high specific heat of water and the key dependence of freshwater production on nutrients rather than temperature. However, there may be effects on lake stratification, fish distribution and restoration of lakes by biomanipulation. Rising sea levels have the potential to alter lowland riverine lakes very considerably by saline influx. A holistic, intuitive view is more likely to produce realistic scenarios for the future than one based on reductionism.

Vegetation change and pollen recruitment in a lowland lake catchment: Groby Pool, Leics (England)

This investigation adopts an historical approach to pollen recruitment in a lowland English lake. The history of woodland and land-use has been reconstructed for the past 200 years from documentary sources and from the lake sediment pollen record. Comparison of these data sets are used to establish the ‘effective’ pollen catchment of the lake and to investigate how well these support predictive models of pollen input to lakes.

Viable seeds in deposits of the former lakes Kvismaren and Hornborgasjön, Sweden

The viable seed content in sediments from two shallow lowland lakes, Lake Kvismaren and Lake Hornborgasjön in south Sweden, was investigated and compared. The number of seeds per species and their depth distribution (0–50 cm) in the sediment were examined through germination trials in a greenhouse. Samples of sediments were given either an exposed moist treatment (Kvismaren and Hornborgasjön) or a submerged treatment (Hornborgasjön). The species composition of viable seeds differed considerably between the two lakes. The sediments in Kvismaren were dominated by Alisma plantago-aquatica L. and Carex spp. and in Hornborgasjön by Carex acuta L., other Carex spp. and Juncus spp. From the two samples sites in Kvismaren, 481 000 seeds m −2 and 248 000 seeds m −2 germinated. In Hornborgasjön an average of 48 300 seeds m −2 germinated. Exposed moist treatments resulted in the germination of 30 species. Submerging the sediment samples gave only 23. Depth distributions of seeds in the sediments differed strikingly between the lakes. Large numbers of seeds were found in a distinct horizon ∼ 25 cm below the sediment surface in Kvismaren. This horizon is interpreted as being the remains of an earlier vegetation stage. In Hornborgasjön the greatest number of seeds was found near the sediment surface.

Factors Responsible for Retarding the Eutrophication Rate of Some Mesotrophic Lowland Lakes in N.E. Poland

AbstractThe chemical composition of watershed waters supplying 13 mesotrophic lakes (in N.E. Poland) including as the deepest lake L. Hańcza, z = 108.5 m (summer total phosphorus [TP] content ≤0.050 mg · 1−1, chlorophyll a ≤5μg · 1−1, SD≥2.5 m) in a typical postglacial lake district (Suwalski Landscape Park) as well as surface and bottom waters of the lakes were studied in summer. Although the underestimated (i.e. including only surface runoff, river inflows and precipitation) yearly TP loading is equal to or higher than the permissible value, the lakes have maintained their mesotrophic features for 20 to 30 years. P sorption to the allochthonous inorganic material as well as decalcification processes in the lakes are probably responsible for this situation, as there is a strong difference between the chemical content of supplying waters and lake waters and as there is a considerable enrichment of P on sestonic particles. As a consequence of the low bio‐availability of P, the midsummer amount of chlorophyll a is lower than predicted from the “TP—chlorophyll‐a” relation found for harmoniously eutrophicating (i.e. P‐limited) lakes.

The effects of land use upon water chemistry, particularly nutrient enrichment, in shallow lowland lakes: comparative studies of three lochs in Scotland

Three shallow, lowland lochs (lakes) in the Tayside region of Scotland, experiencing the same climatic regime, were found to be dimictic lakes showing similar clinograde oxygen distributions in summer. Land use differences in their catchments were shown to result in estimated total nutrient surface loadings from 0.3 to 32 g m−2 a−1 phosphorus and from 4 to 240 g m−2 a−1 nitrogen. The major ions in the lochs were calcium and carbonate, but with elevated sulphate levels in all three lochs and an increase in sodium, chloride and sulphate in Forfar loch, which was affected by sewage effluent. Conductivity and total alkalinity showed marked increases with greater intensity of land use, from 64 to 439 µS cm−1 and 0.5–3 meq l−1 Maximum winter loch concentrations of soluble reactive phosphorus ranged from 60 to just under 5 000 mg m−3 and of inorganic nitrogen from 500 to 10500 mg m−3. Maximum chlorophyll ‘a’ ranged from 20 to 250 mg m−3 and comparisons indicated that above winter levels of 5000 mg m−3 N and 500 mg m−3 P, the nutrient-chlorophyll relationships did not hold. Predictions of nutrient input, from land use categories and soil losses of N and P derived from other north temperate areas, were shown to be comparable with inputs calculated from loch measurements. Models predicting loch concentrations of phosphorus from inputs were comparable with measured concentrations, but predictions of chlorophyll and transparency became less accurate with higher nutrient levels. The lochs were mesotrophic (the Lowes), eutrophic (Balgavies) and hypertrophic (Forfar) under the several classification systems used. The implications of their nutrient status for lake management are discussed and the value of studying this unique lake series in a similar physical environment but with considerable chemical differences is considered.

Restoration of Two Lowland Lakes by Isolation from Nutrient-Rich Water Sources With and Without Removal of Sediment

SUMMARY (1) The Norfolk Broadland has suffered extreme eutrophication. Restoration of the once clear water and aquatic plant communities from the present phytoplankton dominance is sought. (2) In the first two experiments, Alderfen Broad was isolated, by diversion of an inflow stream, without removal of its recently-deposited phosphorus-rich sediments. In the second, sediment was removed from Cockshoot Broad and dams were placed against the effluent-rich River Bure, but the Broad continued to be fed by a small stream draining an agricultural and fen catchment. (3) In four years (1979-82) after isolation of Alderfen Broad, the phytoplankton crop was greatly reduced and the water became clear. Net release of P04-P from the sediment ceased and the Broad became dominated by Ceratophyllum demersum L. Then, because of the reduction in turbulence of the water column by the plants, and the organic matter supplied to the sediment surface in their decay, the mechanism for release of P04-P from the sediment was reactivated and, in 1984, supported a large phytoplankton crop in the spring. The aquatic plant population declined. In 1985 there was both spring and summer phytoplankton growth, the latter probably supported by nitrogen-fixation, and the aquatic plant growth was negligible. (4) In Cockshoot Broad a reduction in phytoplankton growth followed soon after isolation and sediment-removal, and the water became very clear and has remained so. Part of the Broad has already recolonized with a diverse collection of aquatic plants. (5) The consequences of these results for the management of the rest of the Broadland waterway are discussed.

The distribution, life cycle and production of Leptophlebia vespertina (L.) (Ephemeroptera) in a lowland lake

Oak Mere, the water body studied, is a moderately productive base-poor lowland lake. It has zones of submerged marginal vegetation growing on sand at the south-west end and on peat at the north-east end. The distributions of L. vespertina and other macroinvertebrates are described in relation to these two distinct areas. Laboratory experiments on behaviour and survival are described in an attempt to explain the patterns of distribution. The seasonal distribution, variations in population density, spatial distribution variance in relation to mean density, life cycle, length-weight relationship, growth and biomass of L. vespertina are then described during two years at the sandy south-west end. The data are used to estimate annual production. Distribution, life cycle, growth and production are compared with populations in water bodies of lower conductivity in the British Isles and Scandinavia.

Factor interaction influencing the distribution of the freshwater "shrimp" Gammarus.

The enormous variation in the environmental factors of south-eastern Norway makes this area particularly suitable for field studies on the relationship between environmental factors and fauna. Lakes are abundant, from 1 to 1,837 m a.s.l., and the geology of the surroundings as well as acid precipitation influence their chemical characteristics. In lowland areas the distribution of Gammarus lacustris is related to how rich in lime the lakes are. Populations found in mountain lakes tolerate much lower levels of calcium and higher H+ concentrations than populations inhabiting lowland lakes. The lowland populations probably have a higher calcium demand when stressed by high temperature. We predict that factor interaction may be used to explain the distribution patterns of the species also in other parts of Europe.

Palynological evidence for lake-level changes during the Flandrian in Scotland

Summary Stratigraphic, relative pollen analytical data and pollen concentration data are presented from two cores collected from a lowland infilled lake basin in the eastern Scottish Borderlands. The stratigraphic sequence between 1·30 m and 2·16 m shows an oscillation of open water and deep water sediments indicating lake-level changes. This is supported by the pollen analytical data which show a markedly changing pollen sedimentation rate and a hiatus in Flandrian II due to changing lake-levels and an overall reduction in water-level. Supporting evidence is also drawn from Din Moss, a nearby radiocarbon dated profile.

Traffic and visitor surveys at Rutland Water

The creation of England’s largest lowland lake has resulted in major changes to existing patterns of recreation demand in the East Midlands. In 1977 and 1978, Leicestershire County Council carried out a number of surveys at Rutland Water as part of a regular monitoring of all large countryside recreation sites in the county. In addition to establishing visitor levels and characteristics, the surveys sought to establish the extent to which Rutland Water has attracted visitors from other beauty spots in the region or indeed has generated an additional demand. Further studies were undertaken to assess the impact of the large number of visitors on the surrounding roads and villages. Lessons learnt in planning for recreation at Rutland Water may well have a general application to similar new developments elsewhere in the country.

Ecological studies of phytoplankton in the Waikato River and its catchment

Most of the main streams and lakes of the Waikato catchment were surveyed for phytoplankton in April 1974 and February 1975; 69 genera (118 species) of phytoplankton were identified. Phytoplankton density increased going downstream along the Waikato River and the diversity of phytoplankton communities increased with distance from the river mouth. An explosive increase in algal density in the centre of Lake Ohakuri was found in both surveys. The increase was believed to be associated with an increase of nutrients and a shift from river to lake environment in this part of the river system. Diatoms dominated the Waikato River and most of its tributaries. Blue‐green algae formed blooms in the lowland lakes. Green algae were common, but were never dominant in any locality. The seasonal succession of some major species in the lower Waikato River (i.e., at Ngaruawahia, Rangiriri, and Tuakau) was determined from September 1973 to August 1974. Most species were most abundant in summer. Phytoplankton density was positively correlated with temperature and negatively with nitrate concentration. Flow rate may exert an overall control on phytoplankton growth in the Waikato River.