Lake Plankton Research Articles

Flow cytometric determination of bacterial abundance in lake plankton with the green nucleic acid stain SYTO 13

We have developed a protocol for the cytometric enumeration of bacterioplankton in lakes with the nucleic acid stain SYTO 13; our protocol can be used with any standard bench‐top flow cytometer equipped with an argon laser with excitation at 488 nm. The protocol performs well in the range of bacterial densities from 105 to 106 ml−1. Estimates of bacterial abundance using the cytometric technique ranged from 72 to 141% of the epifluorescence estimates with DAPI staining. The average C.V. of replicate cytometric counts was 2.4%, and the average C.V. for cytometric counts in replicate water samples was 6.7%. The precision of cytometric counts was 10‐fold higher than corresponding epifluorescence bacterial counts, and the sample processing time is decreased by 10–15‐fold relative to the epifluorescence technique. This cytometric protocol can be applied to samples from a wide variety of lakes and offers an accurate, precise, and fast alternative to standard epifluorescence bacterial counts.

Ecosystem‐specific patterns in the relationship between zooplankton and POM or microplankton del13C

Measurements of plankton δ13C from 28 temperate lakes show that zooplankton are depleted in 13C relative to smaller planktonic size fractions. A broad literature survey indicates that this is a general pattern in lakes but not in marine and estuarine plankton communities, where zooplankton are generally enriched in 13C relative to particulate organic matter (POM) or microplankton. Marine plankton thus conform to the assumptions that pelagic food webs are essentially driven by phytoplankton and that POM or small planktonic size classes largely reflect algal carbon, which is transferred to zooplankton with a slight enrichment in 13C. The plankton of lakes and possibly of estuaries, however, do not conform to this expectation. We show that there is a continuum in the δ13C differences between POM and zooplankton from open ocean to coastal areas and estuaries and that a similar pattern occurs from unproductive to highly productive lakes. These differences probably reflect both the degree in POM dilution by nonalgal sources of organic carbon and depthrelated changes in the isotopic signature of phytoplankton in lakes and suggest systematic differences in organic carbon flow pathways among aquatic ecosystems.

Seasonal dynamics of the planktonic community in Lake Druzhby, Princess Elizabeth Land, Eastern Antarctica

1. The temporal abundance and composition of the plankton of a continental Antarctic lake (Lake Druzhby) situated in the Vestfold Hills, Eastern Antarctica was investigated from December 1992 to December 1993. The system was dominated by microbial plankton (cyanobacteria, heterotrophic bacteria and protozoans) with few metazoans.2. Chlorophyll a concentrations ranged between 0.15 and 1.1 μg l–1 and showed highest levels from late winter to spring.3. Heterotrophic bacteria ranged between 75 and 250 × 106 l–1 with highest abundances in late winter/spring. Mean bacterial biovolumes showed considerable seasonal variation (0.05–0.31 μm3). Largest biovolumes occurred in summer and this was the time of highest community biomass.4. Heterotrophic nanoflagellates reached highest abundances in late summer (maximum 14 × 105 l–1). Their mean biovolume also exhibited considerable seasonal variation, ranging between 1.77 and 27.0 μm3, with largest size resulting in community biomass peaking in early summer. Ciliated protozoa were poorly represented and sparse. Phototrophic nanoflagellates were sparse in this lake; instead the phototrophic plankton was dominated by a small rod‐shaped cyanobacterium which constituted the largest carbon pool in the system. It was common throughout the year, its biomass peaking in autumn. Its presence is discussed in relation to lake morphometry and light climate.5. Heterotrophic flagellate grazing rates ranged from 6.78 bacteria cell–1 day–1 at 2 °C to 11.8 bacteria cell–1 day–1 at 4 °C. They remove around 2% of the bacterial carbon pool per day during summer and winter.6. Nutrient levels were low and recorded in pulses. Dissolved and particulate organic carbon were also low, usually less than 3 mg l–1 and 600 μg l–1, respectively. The carbon pools were derived from autochthonous sources. This lake system is driven by bottom‐up forces and lacks top‐down control, which fits into the picture currently seen for continental Antarctic lakes.

Lake trophic state and the limnological effects of omnivorous fish

Ecologists have hypothesized that planktivorous fish have greater effects on the plankton and water quality of oligotrophic lakes than eutrophic lakes. We tested this hypothesis in a tank-mesocosm experiment of factorial design in which five biomass levels of filter-feeding omnivorous gizzard shad (Dorosoma cepedianum) were cross-classified with two levels of lake trophic state achieved by filling tank-mesocosms with water and plankton transported by truck from two lakes with different trophic states. The presence of gizzard shad significantly increased total phosphorus, primary productivity, chlorophyll, and particulate phosphorus (PP) 2–20 and 20–200 µm and significantly decreased Secchi depth, cladocerans, copepods and PP > 200 µm. The effects of gizzard shad on chlorophyll, Secchi depth, cladocerans, copepods and PP 2–20 and > 200 µm were dependent on lake trophic state and most intense in the eutrophic lake system. This experiment suggests that filter-feeding omnivorous fish interact synergistically with trophic state so that the limnological effects of omnivorous fish become more intense with increased eutrophication.

Effects of phosphorus and allochthonous humic matter enrichment on metabolic processes and community structure of plankton in a boreal lake (Lake Pääjärvi)

Effects of phosphorus and allochthonous humic matter enrichment on metabolic processes and community structure of plankton in a boreal lake (Lake Pääjärvi)

Fish-induced changes in zooplankton grazing on phytoplankton and bacterioplankton: a long-term study in shallow hypertrophic Lake Søbygaard

The impact of fish-mediated changes on the structure and grazing of zooplankton on phytoplankton and bacterioplankton was studied in Lake S0bygaard during the period 1984-92 by means of in vitro grazing experiments (C-labelled phytoplankton, H-labelled bacterioplankton) and model predictions. Measured zooplankton clearance rates ranged from 0-25 ml I' h on phytoplankton to 0-33 ml H h on bacterioplankton. The highest rates were found during the summer when Daphnia jpp. were dominant. As the phytoplankton biomass was substantially greater than that of bacterioplankton throughout the study period, ingestion of phytoplankton was 26-fold greater than that of bacterioplankton. Multiple regression analysis of the experimental data revealed that Daphnia spp., Bosmina longirostru and Cyclops vidnus, which were the dominant zooplankton, all contributed significantly to the variation in ingestion of phytoplankton, while only Daphnia spp. contributed significantly to that of bacterioplankton. Using estimated mean values for clearance and ingestion rates for different zooplankters, we calculated zooplankton grazing on phytoplankton and bacterioplankton on the basis of monitoring data of lake plankton obtained during a 9 year study period. Summer mean grazing ranged from 2 to 4% of phytoplankton production and 2% of bacterioplankton production to maxima of 53 and 88%, respectively. The grazing percentage decreased with increasing density of planktrvorous fish caught in August each year using gill nets and shore-line electrofishing.The changes along a gradient of planktivorous fish abundance seemed highest for bacterioplankton. Accordingly, the percentage contribution of bacterioplankton to the total ingestion of the two carbon sources decreased from a summer mean value of 8% in ZJap/tnia-dominated communities at lower fish density to 0.7-1.1% at high fish density, when cyclopoid copepods or Bosmina and rotifers dominated. Likewise, the percentage of phytoplankton production channelled through the bacteria varied, it being highest (5-8%) at high fish densities. It is argued that the negative impact of zooplankton grazing on bacterioplankton in shallow lakes is highest at intermediate phosphorus levels, under which conditions Daphnia dominate the zooplankton community.

Highly active microbial communities in the ice and snow cover of high mountain lakes

An exploratory study carried out in Pyrenean and Alpine lakes shows that a rich, active microbial community lives in the slush layers of the winter cover of such lakes in spite of the low temperature and the seasonal occurrence of the habitat. Bacteria were very diverse in morphology, with filaments reaching up to 100 (mu)m long; flagellates, both autotrophic (chrysophytes, cryptophytes, dinoflagellates, and volvocales) and heterotrophic, and ciliates were abundant, reaching biovolume values up to 2.7 x 10(sup6) (mu)m(sup3) ml(sup-1). Species composition was very variable, with dominance depending on date and depth. Although many species were typical of lake plankton communities, some were restricted to the slush, for instance the predatory ciliates Dileptus sp. and Lacrymaria sp., and others were restricted to the surface pools, such as the snow algae Chlamydomonas nivalis. Microbial biomasses and usually bacterial and algal activities were greater in the slush layers than in the lake water. Photosynthesis rate in the upper cover layers reached values up to 0.5 (mu)g of C liter(sup-1) h(sup-1), and high bacterial activities up to 226 pmol of leucine incorporated liter(sup-1) h(sup-1) and 25 pmol of thymidine incorporated liter(sup-1) h(sup-1) were measured. For most species, lake water flooding the ice and snow cover could provide an inoculum. Differential growth depending on the environmental conditions (nutrients, organic matter, light) of a particular slush layer could provide dominance of different groups or species. However, there was no obvious colonizing mechanism for those species not appearing either in plankton or in communities on top of the snowpack.

The Dynamics and Relative Strength of Bottom-Up vs Top-Down Impacts in a Community of Subtropical Lake Plankton

By analysis of a previously described system consisting of three trophic levels (phytoplankton, zooplankton, and an invertebrate predator in a eutrophic lake), the generality of two hypotheses of food web theory was tested. (1) Top-down (predator-on-prey) impact weakens down the food web. (2) Time lags in the trophic level interactions decrease in duration from top to bottom of food webs. In the lake studied, a spring pulse of phytoplankton impacted with a delay the biomass of upper trophic levels ― herbivorous zooplankton and the predatory water mite, Piona sp. Later in the season, the top-down control by Piona cascading down the food web became prevailing over bottom-up forces. Cross-correlations revealed that the top-down effect was not weakening downwards. Instead, the impact of zooplankton biomass on phytoplankton biomass was stronger than that of the invertebrate predator on zooplankton, despite the fact that the predator caused a decline in zooplankton biomass. Contrary to the theory, the time lags did not differ significantly between the impacts of trophic levels of a given pathway direction. However, they differed between bottom-up vs top-down pathways in suppose of the theory. Thus, some predictions of the food web theory may be restricted only to fish-impacted systems for which it was originally developed. An alternative explanation could be that the strength of top-down impact is associated with the width of consumers' feeding niches: the impact is stronger when niches are wider

Selective scavenging of copper, zinc, lead, and arsenic by iron and manganese oxyhydroxide coatings on plankton in lakes polluted with mine and smelter wastes: results of energy dispersive X-ray micro-analysis

Energy dispersive X-ray micro-analyses of the remains of individual organisms in plankton samples, together with more conventional analyses of sediments and water, were performed for the purpose of investigating the accumulation of heavy metals by plankton in three Canadian Shield lakes polluted with Cu, Zn, Cd, Pb, As, and SO 2− 4 from a base metal mine and smelter. The results showed that appreciable quantities of Cu and Zn were bound to crustacean exoskeletons, loricae of the rotifer Keratella, and loricae of the euglenophytcs Trachelomonas and Strombomonas; euglenophyte loricae also contained As and Pb, but an associated chrysophyte cyst, though richer in Cu, Zn, and Pb, had no detectable As. In all specimens except the chrysophyte cyst, the trace elements were associated with Fe and Mn, implying that Fe and Mn oxyhydroxides deposited on the organisms' armour had scavenged them from the water. Euglenophyte loricae were richest in Fe and Mn and associated trace elements. Moreover, the inferred FeOOH and MnOOH phases discriminated between different elements, Zn being selectively bound by MnOOH whereas Cu and As were bound by FeOOH. Adsorbed Cu and Zn were associated with S to a significant degree only where the sediments were poorest in sulfide, suggesting that the metals were complexed by thiol compounds secreted by organisms as a defense against metal toxicity wherever environmental sultide levels were too low to provide protection. The Fe, Mn, Zn, and Cu concentrations and Mn Fe and Zn Cu ratios of plankton hard parts decreased with the E h of the sediments. Dissolved Fe and Mn released into the water column from anoxic but sulfide-poor sediments probably precipitated as FeOOH and MnOOH on surfaces of organisms wherever the water hud sufficient dissolved O 2, the MnOOH FeOOH ratio and hence the Zn Cu ratio increasing with O 2 concentration; but strongly reducing conditions and H 2S production in sediments interfered with the formation of both FeOOH and MnOOH. Fe precipitating as FeS in the sediments whilst Mn remained in solution. Sulfides inhibited bio-accumulation of Cu and Zn by hindering the formation of FeOOH and MnOOH coatings and by suppressing the release of dissolved Cu and Zn (Cu in particular) from the sediments. The Cu, Zn, Fe. and Mn concentrations and Zn Cu and Mn Fe ratios of plankton hard parts and the concentrations of bio-available (DTPA-extractable) Cu and Zn in the sediments were lowest in a lake whose sediments had anomalously low E h and high sultide levels caused by sewage effluents, algal blooms, and SO 2− 4, even though these sediments had the highest total Cu and Zn content. Thus, bio-accumulation of metals depended on the bio-availability, not the total supply, of the metals. The results of the research are consistent with the following generalisations: (1) FeOOH and MnOOH are commonly deposited on exposed surfaces of a wide range of plankton hard parts in different freshwater environments: (2) the FeOOH and MnOOH coatings scavenge heavy metals and metalloids from the water and are largely responsible for the passive accumulation of these elements by plankton: (3) FeOOH and MnOOH have different trace element affinities, thus affecting the proportions as well as the quantities of the elements bound to the plankton surfaces: (4) the accumulation of metals by plankton hard parts is controlled by environmental variables such as E h and sulfide and O 2 levels, as these factors regulate the precipitation of FeOOH and MnOOH surface films, determine the MnOOH FeOOH ratio, and control the speciation, solubility and bio-availability of metals stored in bottom sediments, whereas total metal concentrations in sediments may have no appreciable effect on the bio-accumulation of the metals; and (6) heavy metal bio-availability is limited mainly by sulfides generated in sediments: where sulfides are lacking, thiol compounds are released into the water by the plankton to prevent toxic effects of the metals. These conclusions have significant implications for the cycling and ecological effects of toxic and nutritional trace elements and for the monitoring, abatement, and prevention of water pollution due to mining, smelting, and other industrial activities.

Are phytoplankton dynamics in rivers so different from those in shallow lakes?

This paper introduces a series of contributions to the ninth meeting of the International Association of Phytoplankton Taxonomy and Ecology, held in Belgium during July, 1993. It draws from the original papers a synthesis which supports the view that the successful species in rivers and turbid shallow lakes are selected primarily on their ability to survive high-frequency irradiance fluctuations as they are circulated through steep light gradients. The selective distinction is less than that which discriminates between plankton of deep lakes and shallow lakes or even between clear and turbid shallow ones. River plankton is, however, dependent on fast growth rates but its survival in rivers is aided by a suite of water-retentive mechanisms. The ecology of turbid systems is dominated by physical interactions, those biotic interactions traditionally believed to regulate limnetic communities being suppressed and rarely well-expressed.

A survey on water chemistry and plankton in high mountain lakes in northern Swedish Lapland

A survey on water chemistry and plankton in high mountain lakes in northern Swedish Lapland

Radiotracer study ofphosphorus uptake by plankton and redistribution in the water column of a small humic lake

The movement of P in the plankton of a humic lake was studied in late July within a 2‐m‐diameter tube. The tube enclosed water from the surface to below the epilimnion with the steep vertical stratification of the lake undisturbed. [32P]orthophosphate was mixed into the epilimnion of the enclosure and its fate followed for 2 weeks. In the epilimnion ∼85% of all the P in organisms was in Daphnia longispina, which comprised almost all the zooplankton biomass. The respective proportions for bacterioplankton and phytoplankton were ∼12 and 3%. Early in the experiment when the temperature of the epilimnion was ∼20°C, the turnover rate of phosphate was of the order of 3 h. By the first sampling, 3 h after the experiment began, bacteria showed the highest affinity for phosphate, but with this coarse time resolution, the pattern of 32P incorporation into phytoplankton appeared similar. The specific radioactivity in D. longispina equaled that in the bacterial and algal fractions after only 2 d, implying rapid and direct foodchain linkage between these P pools. An explanation for such rapid transfer of P may be that D. longispina consumes food with a high concentration of P, such as bacteria. At the end of the experiment, the specific radioactivity of the dissolved P pool was considerably lower than that of the other fractions, indicating only slow exchange between part of the dissolved P pool and the plankton.

Calanoid copepod grazing on phytoplankton: seasonal experiments on natural communities

Calanoid copepods are major components of most lacustrine ecosystems and their grazing activities may influence both phytoplankton biomass and species composition. To assess this we conducted four seasonal, in situ, grazing experiments in eutrophic Lake Rotomanuka, New Zealand. Ambient concentrations of late stage copepodites and adults of calanoid copepods (predominantly Calamoecia lucasi, but with small numbers of Boeckella delicata) were allowed to feed for nine days on natural phytoplankton assemblages suspended in the lake within 1160 litre polyethylene enclosures. The copepods reduced the total phytoplankton biomass of the dominant species in all experiments but were most effective in summer (the time of highest grazer biomass) followed by spring and autumn. In response to grazing pressure the density of individual algal species showed either no change or a decline. There were no taxa which increased in density in the presence of the copepods. The calanoid copepods suppressed the smallest phytoplankton species (especially those with GALD (Greatest Axial Linear Dimension) < µm) and there appeared to be no selection of algae on the basis of biovolume. Algal taxa which showed strong declines in abundance in the presence of the copepods include Cyclotella stelligera, Coelastrum spp., Trachelomonas spp., Cryptomonas spp., and Mallomonas akrokomos. Calanoid copepods are considered important grazers of phytoplankton biomass in this lake. The study supports the view that high phytoplankton:zooplankton biomass ratios and large average algal sizes characteristic of New Zealand lake plankton may, at least partly, be caused by year round grazing pressure on small algae shifting the competitive balance in favour of larger algal species.

Spatial Variation of Crustacean Plankton in Lakes of Different Size

The patterns of spatial distribution of planktonic crustaceans changed with increasing lake size. Greatest abundances were often found offshore in smaller lakes but nearshore in larger lakes. Interstation similarity of plankton, measured with Jaccard's and Renkonen's indices, was higher in small- to middle-sized lakes and lower in very small and very large lakes, indicating that mechanisms existed at both ends of the size spectrum which prevented plankton from mixing horizontally. The information content of a single central lake sample was evaluated against a lake average from 9–10 stations. To capture at least 80% of the species present, one station was sufficient only in smaller lakes, three to six stations were needed in the smallest and medium-sized lakes, and more than nine stations were needed in the largest lake. The single central station in small- and medium-sized lakes represented average total plankton abundance and dominant species relatively well but underestimated rare species. In larger lakes, lake average plankton was not well characterized by a single station. In Lake Superior, the central station reflected the offshore but not the nearshore community. Neither plankton abundance nor the number of species appeared related to lake size in the series of lakes investigated.

Composition and Sedimentation of Aquatic Pigments Associated with Deep Plankton in Lakes

High Performance Liquid Chromatography (HPLC) pigment techniques were applied to study planktonic pigment composition and sedimentation in four Wisconsin (USA) lakes. In each lake, deep blooms of phytoplankton overlaid phototrophic sulfur bacteria in the region of the oxic-anoxic interface. Chlorophyll a and bacteriochtorophyll (a, d, and e) were observed as indicators of phytoplankton and phototrophic sulfur bacteria, respectively. Major taxonomic classes of phytoplankton were further resolved based on carotenoid signatures. In contrast to three oligo-mesotrophic Wisconsin lakes in which deep phytoplankton were comprised of dinoflagellates (indicated by the carotenoids peridinin, diadinoxanthin), cryptophytes (alloxanthin), and chrysophytes (fucoxanthin), the deep phytoplankton community in mesotrophic Mirror Lake was dominated by blue-green algae (oscillaxanthin, myxoxanthophyll, zeaxanthin, and echinenone). Deep planktonic production strongly influenced sedimentation of algal pigments and obscured the relationship between apparent water quality and sedimentary pigment deposition.

Microbial consortia in the plankton of a freshwater Antarctic lake

Microbial consortia in the plankton of a freshwater Antarctic lake

Dissolved alkaline phosphatase activity (APA) and the contribution of APA by size fractionated plankton in Lake Schöhsee

In 1987, the kinetics of alkaline phosphatase activity (APA) of size fractionated planktonic cells were examined to define the relative roles of free (dissolved) APA and the plankton components of ...

Long-term effects of reduced nutrient loading and food-web manipulation on plankton in a stratified Baltic hardwater lake (Lake Haussee, Germany, Feldberg)

Long-term effects of reduced nutrient loading and food-web manipulation on plankton in a stratified Baltic hardwater lake (Lake Haussee, Germany, Feldberg)

The stoichiometry of carbon, nitrogen, and phosphorus in particulate matter of lakes and oceans

The mean carbon, nitrogen, and phosphorus contents of particulate material for 51 lakes or lake basins, extending from arctic to tropical climatic regions, including small lakes as well as the largest lakes in the world, indicate that Redfield ratios are the exception rather than the rule in freshwater. The C : P and N : P ratios are more variable for lake particles but generally higher than marine particles, and the mean molar C : N, C : P, and N : P ratios are substantially higher than the Redfield ratio of 106 : 16: 1. On average, lower C : N, C : P, and N : P ratios occur in subarctic lakes while higher ratios occur in the tropics and in temperate, oligotrophic lakes on the Canadian Shield. In shield lakes with long residence times (&gt;6 months) the high ratios of C : N, C : P, and N : P do not originate from streamborne or atmospherically deposited particles but arise from in‐lake processes. Regression analysis demonstrates that small lakes are generally more N and P deficient than large lakes. In freshwaters, particulate composition ratios imply that a wide variety of conditions exists in lakes, including N and P deficiency, as well as N and P sufficiency. In the Experimental Lakes Area of Canada, independent physiological nutrient status indicators generally agree with the status indicated by seston ratios. The relative uniformity of marine C : N : P composition (compared to lakes) at the Redfield ratio suggests that marine plankton cannot be as severely, or as frequently, limited by N and P as lake plankton. Consequently, the paradigm of N limitation in the oceans requires qualification. Based on particulate composition, it is more correct to say that ocean plankton is not as N and P deficient as lake plankton.

The microbial plankton of freshwater lakes in the Vestfold Hills, Antarctica

The plankton of twelve freshwater and slightly saline lakes in the Vestfold Hills, Antarctica was sampled in February 1991. All of the lakes are oligotrophic. The chlorophyll a concentrations in the lakes ranged from 0.10–2.69 μg · 1−1. The majority of the phytoplankton were flagellates or picoplanktonic cyanobacteria with the species composition varying between the lakes. Cyanobacteria were found in five of the lakes. Five to 6 species of ciliated protozoa occurred, among them oligotrichs, including the mixotrophic species Strombidium viride. The concentrations of protists and bacteria were an order to several orders of magnitude lower than reported from lower latitude oligotrophic lakes. Low species diversity and low numbers in the plankton characterise these eastern Antarctica lakes which reflects their low nutrient status and isolation.