Lake Assemblages Research Articles

Behavioural response in plants: adjustment in algal recruitment induced by herbivores

Behavioural responses to chemical cues are common among animals, whereas there is still intense debate as to whether plants are able to detect environmental information and adjust their behaviour accordingly. Here, I report that several freshwater algal species respond to the presence or absence of grazers in the water column by regulating their recruitment rate from sediment to water. In lakes, as well as in controlled laboratory experiments with low abundances of grazers, recruitment of certain flagellated algal species was high, whereas recruitment was negligible when grazer abundances were high. Hence, certain plants equipped with locomotion organelles can use cues released from herbivores to adjust the timing of recruitment from the 'seed-bank', thereby reducing the exposure to grazing. Such an adaptation may have important consequences for dominance and temporal succession in algal communities. In an evolutionary context, this study shows that consumer-avoidance behaviour is not an adaptation exclusive to animals.

Abundance and species richness patterns of diving beetles (Coleoptera, Dytiscidae) from exposed and protected sites in 98 northern Swedish lakes

Forty species of predaceous diving beetles (Coleoptera, Dytiscidae) were collected in sweepnet samples from 98 boreal lakes in northern Sweden. Samples from protected sites with vegetation had significantly more specimens and species than those from exposed sites without vegetation in the same lakes. No geographically based differences, e.g. latitudinal or in distance from the coast, were found. These gradients were 200 and 150 km long, respectively. Species' distribution in terms of occurence at number of sites was positively correlated with the mean abundance of the species. The relationship between species' abundance and body length was characterized by the lack of large, abundant species. Partial least square regressions on dytiscid abundance and species richness showed low predictive power of lake area, altitude and water chemistry. The seven environmental variables used explained at best 15.3 and 24.4% of the total variance in abundance and species richness, respectively. The results are compared to activity trap catches of dystiscids in lakes in an adjacent region. A majority of the species occured in both materials. However, species occuring in high proportion in one of the materials, were rare in the other material. The mean body length of the species caught more efficiently with traps was not larger than that of those overpresented in net sampling. Based on this study and the available literature data, the regional species pool of boreal lake dytiscids is estimated to 30–40 species. It is still an open question if lake assemblages are markedly poorer than those found in the development of vegetation, whereas the impact of water chemistry is small.

Distribution of benthic diatom assemblages in Tasmanian highland lakes and their possible use as indicators of environmental changes

Classification and gradient analyses of littoral diatom assemblages and 37 chemical and physical variables in littoral sediments of 76 Tasmanian dystrophic and (ultra-)oligotrophic highland lakes indicate strong west-east gradients in pH, calcium concentration, sodium concentration, alkalinity, and gilvin, which are underlain by an oceanic-inland gradient and geological discontinuities. Two major clusters of lakes are recognised, concordant with the recognition on chemical and optical criteria of western and eastern limnological provinces and coinciding with a steep gradient in mean annual rainfall and major geological changes. Changes in species composition occur gradually across the corridor separating the two provinces. Highly significant inference models can be constructed for pH and calcium concentration and related variables, which can be used in palaeolimnological reconstructions in Tasmanian highland lakes. Resume : D'apres une classification et des analyses de gradient des assemblages de diatomees du littoral et de 37 variables chimiques et physiques observees dans des sediments littoraux de 76 lacs des hautes terres de Tasmanie, de type dystrophique et (ultra-)oligotrophe, il existe de forts gradients ouest-est de pH, de calcium, d'alcalinite et d'absorbance optique (gilvin), qui sont sous-tendus par un gradient des caracteristiques oceaniques et interieures et des discontinuites geologiques. On distingue deux grappes principales de lacs, qui correspondent a la presence, d'apres des criteres chimiques et optiques des provinces limnologiques de l'ouest et de l'est, et qui coincident avec un gradient prononce des precipitations annuelles moyennes et des grands changements geologiques. On note generalement des changements graduels dans la composition specifique en travers du corridor separant les deux provinces. On peut construire des modeles d'inference tres significatifs a partir du pH, du calcium et de variables connexes, et ceux-ci peuvent servir a reconstructions paleolimnologiques sur les lacs des hautes terres de Tasmanie. (Traduit par la Redaction)

Consequences of elevated temperatures for zooplankton assemblages in temperate lakes

This paper is a review of direct and indirect effects of elevated temperatures (≥25°C) on freshwater zooplankton in temperate latitudes. Effects of temperature on aspects of behavior, individual growth, development and reproduction, and population dynamics are compared across zooplankton taxa. Thermal responses vary markedly among co-occurring species and among clones within parthenogenetic species. There is strong evidence that elevated temperature can produce a reduction in body size within zooplankton populations. Also, some zooplankton assemblages become increasingly dominated by smaller bodied forms under warm conditions. We hypothesize that certain cold-water zooplankton species show the greatest risk of local extinction during late summer heating events because of their dependence on thermal refugia, and their lack of diapausing or dispersal stages. Indirect effects of elevated temperature mediated by changes in the algal food supply or by altered interspecific interactions are also explored. Elevated temperature can change algal community structure and algal food quality, all of which can affect the outcome of zooplankton interspecific competition. Size-selective predation rates of planktivorous fish are also likely to increase with increasing temperature or when zooplankton are driven from the hypolimnion. The onset of fish feeding is also likely to begin earlier in the season thus reducing the time that large zooplankton are present during the ice-free season. Reductions in the size structure of zooplankton assemblages are likely to alter water clarity, nutrient regeneration and fish abundances.

Element ratios and growth dynamics of bacteria in an oligotrophic Canadian shield lake

Basic bacterial physiology predicts that the element composition of cells changes as a function of generation time. Rapidly growing cells are characterized by low C:P and N:P ratios compared to ratios of slowly growing cells. Working from this premise, we (1) determined the element composition of newly synthesized bacteria collected from an oligotrophic Canadian shield lake and (2) compared the changes in element composition of bacteria to their temporal changes in abundance. The element composition of new biomass was determined from the change in bacterial element composition following nutrient enrichment and incubation with nutrients derived from seston concentrated from a eutrophic lake. Bacterial C:P and C:N ratios generally decreased during incubation but N:P ratios changed only slightly. When averaged, new bacterial biomass had a C:P ratio (atomic) of 44.4, N:P of 8.5, and C:N of 5.5 (C N:P 44:9:1). The element composition of the in situ bacterial assemblage of an oligotrophic lake was compared to the temporal dynamics of the assemblage. Cell N:P and C:P ratios were low when cell abundance was increasing compared to the ratios obtained following a rapid decline in cell abundance. The data indicate that bacteria may alter their cellular element composition, and that the growth dynamlcs of bacterial assemblages may be reflected by the element ratios of their biomass.

Effect of Substrate on Colonization of Experimental Ponds by Chironomidae (Diptera)

ABSTRACT The influence of substrate type on larval chironomid community structure was studied in a controlled experiment utilizing small artificial ponds. Wading pools containing three types of sterilized sediments of different particle size and organic content were colonized naturally over two eight-week periods. Total abundance and species composition varied with substrate type. Clay treatment ponds had the lowest abundance and were dominated by Chironomus spp. Gravel and sand-silt treatment ponds were dominated by Kiefferulus dux. Results agree with field studies and indicate that substrate is important in structuring chironomid assemblages in lakes and ponds. Data obtained using multiplate samplers did not agree well with data from benthic samples, indicating that artificial substrates do not always provide a representative sample of the benthic habitat.

Diversity of the phytoplankton assemblages of a polymictic hypertrophic lake

Diversity of phytoplankton assemblages from the shallow hypertrophic lake, the Albufera of Valencia (Spain), was studied for the period 1980 - 1988. The lake serves as a reservoir for the surrounding rice cultivation, with two seasonal periods of water retention to keep ricefields flooded. The seasonal hydrological cycle seems to be the primary factor driving phytoplankton community changes, compounding the disturbances due to water mixing. The lake is dominated throughout by filamentous cyanophytes. A Shannon-Weaver function was used to measure phytoplankton diversity. Phytoplankton steady-states, defined as the periods when more than 80 % of total phytoplankton biomass was shared by only 1-3 species, were assumed for comparative purposes. Phytoplankton diversity and the assemblages showed a high degree of interannual regularity during the study period. Phytoplankton was mainly limited by light and water flushing from November to April, and more by nitrogen and phosphorus during summer. Low diversities were related to stable community states, while higher diversities corresponded to non-steady state periods, the former lasting longer. Four annual phytoplankton associations were found, both steady and non-steady states being characterized by two different algal communities. Diversity reached a steady-state, lasting from November to june. From january to March, water flushing high nutrient levels and oligophotic conditions selected in favour of large unicellular phytoplankton species. The onset of spring quiescence resulted in the lowest values of diversity and species richness, due to the overwhelming dominance of vernal crops of Planktothrix agardhii, whose selfshading populations would have excluded many less well-adapted species. By june, nutrient decrease and increasing temperatures and irradiance, moved phytoplankton towards an intermediate assemblage dominated by smaller and faster growing species. Thereafter, long-summer water stabilization and nutrient depletion interacted to enhance diversity and the onset of a non-steady state, characterized by an immature summer assemblage of large colonies, potentially motile (e.g. Microcystis) and with high nutrient storage capacity. During the autumnal period when the ricefields are drained for harvest, diversities reached maximal levels, including species from the surrounding habitats (ricefields and drainage ditches). Lake reisolation by November-December led to another phytoplankton steady-state, when the phytoplankton reverted toward a composition similar to that of June. Storms increased diversity and the presence of small-sized species, contributing to a more rapid species replacement or arresting the establishment of an steady-state, depending upon their intensity frequency and occurence. Stagnation always selected in favour of cyanophytes, while flushing rates enhanced the presence of other algal groups, mainly diatoms. The annual flushing cycle of the lake is regarded as a potential tool for the future lake restoration. Our results confirm the view of regarding the phytoplankton of polymictic Oscillatoria-dominated lakes, as sub-climatic communities mainly limited by light, and agree with some postulates based on the IDH-diversity theory

Bioenergetic analysis of prey consumption byBythotrephes cederstroemiin Lake Michigan

A bioenergetic model for Bythotrephes cederstroemi was constructed using measured physiological parameters to predict predation rates. The model predicts that juvenile B. cederstroemi will consume approximately 150% of their body weight per day, while adults consume 118% of their body weight per day. These rates are consistent with those of other invertebrate crustaceans. The predicted rate was twice that of an experimental measurement reported for Lake Huron B. cederstroemi; this discrepancy is attributed to experimental artifacts and to differences between B. cederstroemi populations in Lake Michigan and those in Lakes Huron and Erie. The model was most sensitive to estimation of ingestion and assimilation efficiencies and, secondarily, respiration coefficients. This model estimates the consumption rate of B. cederstroemi in Lake Michigan under optimal food resource conditions, and may be useful in predicting the future impact of B. cederstroemi predation on the zooplankton assemblages of other lakes.

Regulation and stability in fish assemblages of neotropical floodplain lakes.

Neotropical floodplain lakes provide an excellent opportunity to examine the regulation and stability of fish assemblages. At low water, when lakes are separated, fish are concentrated in the lakes and are presumably subject to strong interspecific interactions that can shape assemblage structure. At high water, when the lakes and river channels become broadly interconnected, ample potential exists for alteration of assemblage structure because eggs, larvae, and older fish may undergo spatial reshuffling among waterbodies. Twenty lakes of the Orinoco River floodplain in Venezuela were surveyed in the early and late dry seasons of two consecutive years. Marked differences in assemblage structure among lakes were established in the early dry season. Changes in assemblage structure during the dry season were large and detectable even at the ordinal level; they reflected a strong reduction of visually oriented fish relative to fish with adaptations to low light. Changes were similar in the two years and were apparently due to species-specific differences in mortality, which was high over the dry season. The annual flood is a strong natural fluctuation that greatly modifies assemblage properties during the wet season. Nevertheless, the potential for alteration of assemblage structure by reshuffling was not realized: assemblage properties early and late in the dry season were similar in the two years, indicating a regular and predictable annual cycle of change in assemblage structure. This regularity can be explained by mechanisms of regulation which appear to be linked to piscivory and the optical environment. In contrast with the prevailing views on neotropical fish assemblages, there seems to be a strong deterministic component to assemblage structure and dynamics in Orinoco floodplain lakes.

Effects of Experimental and Cultural Lake Acidification on Littoral Benthic Macroinvertebrate Assemblages

A simple method for the assessment of littoral benthic macroinvertebrate (BMI) assemblages in lakes was developed at the Experimental Lakes Area (ELA) in northwestern Ontario and applied to 64 lakes in central Ontario. The presence (1) or absence (0) of BMI taxa was established at five sites on each lake, using a kick-and-sweep net technique. Summing presence/absence scores across sites ranked the importance of each taxon in each lake on a scale of 0 to 5. Relationships between the BMI assemblages were assessed using nonmetric multidimensional scaling (NMDS), based upon the Kendall's τ correlation matrix. Correlations between NMDS dimension 1 and 2 scores and environmental variables identified factors that may structure BMI assemblages. The BMI assemblages of three experimentally acidified and seven reference lakes at the ELA were correlated strongly with lake pH. The BMI assemblage structure of central Ontario lakes was predicted by lake area and sensitivity to acidification (NMDS dimension 1) and by lake elevation (NMDS dimension 2). The BMI assemblages of small or Ca-poor and acidic lakes include fewer oligochaetes, mayflies, and Cryptochironomus and Stictochironomus (chironomids) and more Odonata, Trichoptera, Chironomus, Conchapelopia, Microtendipes, and Procladius (chironomids), and Crangonyx (Amphipoda) than other central Ontario lakes.

Density‐Dependent Effects and the Regulation of Crucian Carp Populations in Single‐Species Ponds

Crucian carp (Carassius carassius) is often the only fish species present in small ponds of northern Europe. Such populations are typically at high densities and consist primarily of small, relatively slender, and short—lived fish; populations in multispecies assemblages in lakes display opposite traits. Field and laboratory experiments have implicated predation as an important mechanism structuring crucian populations in multispecies assemblages. To investigate the role(s) of density dependence in structuring pond populations, we manipulated densities of crucians stocked into four sections of a subdivided natural pond in Finland. Mortality of stocked fish during the 3—mo experiment was low (0—11%) and unrelated to density. Growth rates of crucians were both size and density dependent. Larger fish did not noticeably grow in either high— or low—density sections, but growth of smaller size classes was 22% greater in low—density sections. Lower densities and smaller sizes of zooplankton, especially of inshore cladocerans that are an important food resource for smaller crucians, indicated that resource limitation caused by exploitation competition was an important density—dependent process restricting growth of small fish in high—density sections. Crucians rely on reserves of glycogen, stored in the liver and muscle, to fuel the over winter anerobic metabolism that allows them to maintain populations in ponds where winter hypoxia eliminates other fishes. Liver size was significantly larger and glycogen levels were 82% higher in our low—density pond sections than in high—density sections. At higher, but not lower, densities, relative liver size and glycogen levels decreased with body size; combined with the lack of growth of large fish, this indicates that density—dependent energy limitations contribute to the short life—spans and rarity of large fish that characterize pond populations. An increase in relative body depth can be induced in crucians by the presence of piscivorous fish, reducing vulnerability to predation. It has been proposed that increased body depth incurs a substantial energy cost during swimming and should be restricted to specific size classes in populations sympatric with predators. However, in our experiment, crucians of all sizes became significantly deeper bodied, which contributed to higher condition factors in low—density vs. high—density sections. This morphological change, occurring in the absence of piscivores, suggests that energy benefits (accumulation of overwintering reserves) can override any proposed costs for this sluggish, but metabolically unique, fish. Crucian carp successfully reproduced in all sections during the experiment, but growth and recruitment of 0 + fish (young of year) were strongly and negatively related to the numbers of older fish present. The observed density—dependent recruitment was likely caused by starvation—induced mortality and cannibalism; reduced growth observed in 0 + fish would also be expected to cause higher fist—winter mortality, reducing further recruitment at higher densities. Density dependent has a variety of regulatory effects on pond populations of crucian carp that contribute to their presence and resilence.

The relationship between lake chemistry and surface sediment diatom assemblages in Maritime Antarctic lakes

The relationship between lake chemistry and surface sediment diatom assemblages in Maritime Antarctic lakes

The relationship between water chemistry and surface sediment diatom assemblages in maritime Antarctic lakes

Maritime Antarctic freshwater lakes and their catchments are inherently simple systems in an environment which is characterized by strong seasonality. Such lakes offer excellent opportunities to study the interaction of water chemistry and plant communities. The response of diatom species to environmental gradients was assessed by constructing a diatom and water chemistry dataset from 59 lakes at two locations (Livingston Island, South Shetland Islands and Signy Island, South Orkney Islands). Results indicate that diatom species abundance is predominately related to nutrient and salinity gradients. The dataset will be used to create transfer functions which can be applied to sediment core diatom assemblages to reconstruct historical patterns of lake chemistry.

Effects of trichlorobenzene on natural phytoplankton populations

Natural phytoplankton assemblages from an offshore station in Lake Michigan were exposed to individual isomers of trichlorobenzene (TCB) and incubated in situ for a 24 h period. One set of exposures was initiated with a lake assemblage collected at 0330 h from 30 m and the TCB isomers added at 0400 h. The second exposure experiment was initiated with an assemblage from 30 m collected at 1530 h and the TCB isomers added at 1600 h.Comparisons of the chlorophyll a to neutral lipid ratio and the neutral to polar lipid ratios suggest that 1,2,3-TCB is more toxic than 1,2,4-TCB. Furthermore, more effects were observed when exposures were initiated at 0400 h when compared with a parallel experiment initiated at 1600 h. These studies with natural assemblages support culture studies of effect as a function of time of exposure.

DIATOM ASSEMBLAGES AS INDICATORS OF LAKE TROPHIC STATUS IN SOUTHEASTERN ONTARIO LAKES1

ABSTRACTCanonical correspondence analysis (CCA) was used to explore the relationship between measured environmental variables and surficial diatom (Bacillariophyceae) assemblages in alkaline lakes from southeastern Ontario. Total nitrogen (TN), watershed area, alkalinity, and maximum depth each explain significant (P ≤ 0.05) directions of variance in the distribution of diatom taxa.TN was highly correlated to total phosphorus (TP) (r = 0.92), chlorophyll a (r = 0.86), and Secchi depth (r =0.77). When a series of CCAs were run with the first axis constrained to each of these variables in turn, the ratio of the eigenvalue of the first axis to that of the second axis (λ1/λ2) was highest for TN, indicating that TN best explained the distribution of the diatom assemblages in this set of lakes. Furthermore, results of Monte Carlo permutation tests indicated that these four variables did not act independently on the diatom assemblages. Therefore, TN was selected to represent these four closely related variables to infer lake trophic status.Weighted‐averaging regression and calibration (with classical deshrinking) were used to develop transfer functions to infer TN from the relative abundances of 83 diatom taxa recovered from the surficial sediments of 51 lakes. There was a good correlation between diatom‐inferred TN concentrations and measured TN concentrations (r2= 0.75, n = 51).The weighted‐averaging regression and calibration model was used to infer lake trophic status (represented by TN) from diatom assemblages presented in the sediments from Little Round Lake, Ontario. These data were used in conjunction with historical land‐use data in order to quantify the sequence and extent of nutrient enrichment related to human activity in the watershed area.

DIATOMS AS INDICATORS OF LAKE TROPHIC STATUS IN CENTRAL ONTARIO, CANADA

Diatoms in surface sediment from 50 Canadian Precambrian Shield lakes in the Muskoka-Haliburton and central Ontario regions were analyzed in order to establish the relationship between lake trophic status and subfossil diatom assemblage structure. Distribution optima of the most abundant diatom taxa in 30 lakes were calculated by using a weighted average technique. The most commonly observed diatom taxa were classified into five trophic categories: O = oligotrophia OM = oligomesotrophic, M = mesotrophic, ME = mesoeutrophic and E = eutrophic. Abundance values of these diatom trophic groups were used to estimate corresponding values of total phosphorus (TP), chlorophyll-a (chl-a), Secchi depth (SD) and LTSI (a new lake trophic status index developed in this study) using multiple regression methods. The statistical equations obtained by both simple and multiple regression techniques were then applied to 20 newly sampled lakes to test the model. The transfer functions between diatom community structure and ea...

Ecospace utilization, paleoenvironmental trends, and the evolution of early nonmarine biotas

Paleozoic trace fossils evidence paleoenvironmental trends that are linked directly to progressive ecospace utilization (spatial and functional). These trends resulted in a considerable increase of ichnodiversity throughout the Paleozoic. Colonization of settings began as early as the Late Ordovician, as recorded by the presence of terrestrial burrow systems associated with ancient soils. In the other cases, the presence of nonmarine trace fossils in Cambrian and Ordovician sedimentary rocks was the result of temporary colonization by marginal marine organisms and does not reflect establishment of true fresh-water faunas. Devonian trace fossils have been reported from alluvial and alluvial-lacustrine transitional environments. Surface arthropod trackways are dominant in marginal lake settings, representing the development of true biotas. The presence of vertical burrows in fluvial deposits records the establishment of deep suspension-feeding infaunal organisms. Trace fossils from the Carboniferous reflect migration farther into the lakes. Ichnofossils have been reported from shallow and deep lake deposits and from alluvial and alluvial-lacustrine transitional environments. Lake assemblages are dominated by surface grazing trails. The Permian was characterized by the establishment of a deep deposit-feeding infauna, commonly recorded by the Scovenia ichnofacies represented by backfilled meniscate burrows.

SYSTEMATICS AND THE SYNECOLOGY OF AQUATIC INSECTS: PHENOLOGY AND TEMPORAL STRUCTURE OF TEMPERATE LAKE ASSEMBLAGES

AbstractFour emergence series were collected from a small mesotrophic–dystrophic lake in the southern Laurentians of Québec: near shore (station A, 0.3 m, shrubs and heaths), in the littoral zone (B, 0.6 m, and C, 1 m, aquatic vegetation), and in open water (D, 6 m, no vegetation). A gradient of species richness (121–34), of numbers (4622–1120/m2), of diversity (5.62–2.42 bits), and of equitability (0.81–0.48) extended from the shore to the open water. Also recognized was a seasonal succession of early synchronized species, many of which completed a second generation by late summer, and of more dispersed summer species. This pattern was best exemplified in the shore station, whereas in deeper sites, the assemblages were increasingly less structured and dominated by fewer species. Chaoborus punctipennis, a benthic insect feeding in the water column at night, tended to predominate in the outer stations and to impose its particular seasonal dynamics on the assemblage there. Chronological clustering revealed distinctive early- and late-season assemblages in all sites. A succession of distinct and temporally structured mid-season assemblages was evident at the shore station, but this pattern was obscured in other stations because of the recurrence and dominance of the same species throughout. Though these particular patterns may be restricted to the one lake studied, this approach based on a taxonomical and temporal analysis offers promise for generalizations once it has been applied to a variety of lake systems.

Comparative Evaluation of Periphyton and Plankton Production in a Peninsular Lake

The qualitative and quantitative variations In the perlphytlc assemblages of a freshwater lake In South India during 1981-1982 are presented, with comparative reference to the net plankton. With higher settlement in the surface waters, the average percentage composition ofalgal and animal fractions in the periphyton were 82.60 and 17.40 respectively. The corresponding values in the subsurface level were 70.90 and 29.10, with diatoms, green algae and protozoans forming the major groups. The study brought out the trophic significance of the periphytic community in the lake with low phytoplankton production composition (34.62%).

Distribution of Waterfowl Broods in Sudbury Area Lakes in Relation to Fish, Macroinvertebrates, and Water Chemistry

We studied habitat selection by insectivorous waterfowl in 65 small lakes near Sudbury, Ontario. Data on environmental variables (pH, alkalinity, conductivity, calcium, total phosphorus, dissolved organic carbon (DOC), and area), fish, and littoral macroinvertebrates indicated that the distribution of broods was influenced by differences in invertebrate prey assemblages in lakes with differing degrees of acid stress and types offish predation. Lakes ranged in pH from 4.2 to 7.7 (mean = 5.8); 40% were fishless, 43% were dominated by yellow perch (Perca flavescens) or white sucker (Catostomus commersoni) (YP/WS), and the remainder contained only small cyprinids, sticklebacks, or darters (C/S). Fishless lakes were more acid than lakes with fish. Compared with fishless lakes, C/S lakes had higher levels of DOC and YP/WS lakes were larger. Macroinvertebrate composition was strongly related to fish composition and suggested increasing predation along a gradient: fishless < C/S < YP/WS. pH-related variables distinguished lakes with a taxonomically rich benthos from those with a taxonomically poorer fauna. Insectivorous waterfowl selected fishless lakes over lakes with fish and C/S over YP/WS lakes. Lakes with species-rich, acid-sensitive invertebrate assemblages were not selected over those typified by species-poor, acid-tolerant ones.