Lake Plankton Research Articles

Response to nutrient enrichment by the plankton of Antarctic coastal lakes and the inshore Ross Sea

Water samples from coastal lakes and ponds on Ross Island (77°S) and from the adjacent Ross Sea were analyzed to determine nutrient supply relative to the population size of planktonic algae and bacteria. An enrichment test was applied to each water to measure N and P accumulation by the seston as a guide to nutrient demand and deficiency. In all waters, including the sea, the dissolved inorganic N-to-P ratios were low, but inorganic nitrogen was generally present at concentrations that satisfied or exceeded the current growth requirements of the algae. None of the samples responded to added P, and only 3 of the 13 plankton assemblages tested responded positively to nitrogen enrichment. These waters are therefore characterized by an abundance of resources relative to demand. This apparently r-selecting coastal environment contrasts markedly in many ecosystem properties with the inland meromictic lakes of Antarctica.

Food selection by Dreissena polymorpha Pallas (Mollusca: Bivalvia)

SUMMARY. The role of the selection systems in the mantle cavity and the stomach of Dreissena polymorpha was investigated by comparing the composition of particles in the plankton, the stomach and the mid‐gut. Both systems selected particles of 15–40 μm for food. The selection mechanism functioned more efficiently in the presence of simple algal mixtures than in the presence of lake plankton, but did not function at all in animals fed after 16 h starvation. The composition of successive pseudo‐faecal pellets differed. It is concluded that selection of different kinds of particle occurs in specific places in the mantle cavity. Cryptomonas spp. were highly preferred as food. Indications were found that not only does size‐selection occur, but also selection of a chemical nature.

Interactions Between Bacteria and Algae in Aquatic Ecosystems

Bacteria and algae are the numerically dominant organisms in the plankton of lakes and the ocean and their metabolism largely controls pelagic energy flow and nutrient cycling. The purpose of this review is to examine the means by which algae and heterotrophic bacteria interact in planktonic systems. In terrestrial systems, bacterial-plant interactions have been well studied in the rhizosphere, the zone in the soil where microorganisms are influenced by plant roots (108). The concept of the was introduced as a pelagic analogy to the rhizosphere (7). The phycosphere would be the zone surrounding an algal cell within which microorganisms are influenced by algal products. In considering bacterial-algal interactions, then, we should ask ourselves whether a phycosphere exists. I cite specific evidence from the literature for various types of interactions. In doing this I rely heavily on laboratory studies because relatively little field oriented work is available. I include neither the photosynthetic bacteria (e.g. Chlorobiaceae, Rhodospirillaceae) nor the large macroalgae (seaweeds) in this review. The cyanobacteria have both algal and bacterial characteristics, being prokaryotes and capable of oxygenic photosynthesis. As planktonic, aerobic photo-autotrophs the cyanobacteria clearly belong with the phytoplankton in terms of this review.

Vertical Separation of Light and Available Nutrients as a Factor Causing Replacement of Green Algae by Blue-Green Algae in the Plankton of a Stratified Lake

(1) A change from the green alga, Dictyosphaerium pulchellum to the blue-green algae Microcystis aeruginosa and Anabaena spiroides occurred in the plankton of Mt Bold reservoir, South Australia, during November and December 1978. (2) The reservoir was 30-34 m deep, thermally stratified with water mixed to 6-7 m, and a euphotic zone of less than 2.7 m. Measurements of photosynthesis and light penetration showed that photosynthesis was restricted probably to the upper 2.5 m. (3) Growth experiments with eight cultured species, and the natural phytoplankton assemblage, showed that during this change there was a decline of the potential of the water for algal growth to undetectable levels at a depth of 8 m. This could be restored by the combined addition of nitrogen, phosphorus and Fe-EDTA. (4) Continuous measurement of concentration of chlorophyll a in the water column demonstrated that the blue-green algal community was able to migrate to a depth of 12 m despite substantial density barriers. (5) In situ growth experiments, using dialysis bags, showed that populations which were artificially circulated between 0.2 and 10 m, were able to grow, whereas those maintained at a single depth (0-2 m or 10 m) were not. (6) The ability of blue-green algae to overcome successfully this spatial separation between light and nutrients was proposed as the probable cause of the change from green to blue-green algae.

Desmids of theStaurastrum tetracerum-group from a eutrophic lake in mid-wales

Seven desmids have been found in the phytoplankton of a markedly eutrophic lake in mid Wales. All have grown well in laboratory cultures and so an opportunity has been provided to explore the taxonomy and morphological variability of four species, Staurastrum tetracerum, S. irregulare, S. bibrachiatum and S. pseudotetracerum, previously described inadequately. Suggestions for nomenclatural changes are made for S. irregulare and the very variable S. bibrachiatum, which is recorded from the British Isles for the first time. Reasons for the occurrence of the seven desmid species in the eutrophic lake plankton are discussed.

Photosynthetic response of lake plankton to nutrient enrichment: A test for nutrient limitation

Measurements of carbon uptake by lake plankton at different levels of added phosphorus reveal some phytoplankton strategies that contribute to their survival in low‐nutrient waters. Nutrient‐deficient populations seem to temporarily reduce, rather than enhance, photosynthesis when phosphorus becomes available. This contradicts the basic hypothesis of the 14C bioassay used to determine “limiting” nutrients in natural waters. The reduction of carbon uptake rate continues until either the nutrient addition is taken up or no further storage is possible; at this time carbon upake may be enhanced. Concurrent measurements of phosphorus uptake showed no light response unless the plankton were exposed to significant phosphorus concentrations in the dark for several hours. Phytoplankton seem to be adapted for and dependent upon intermittent events exposing them to nutrient‐enriched water. The ability of phosphate‐depleted plankton to take up phosphate in excess of their growth requirements was used to develop an index for phosphate deficiency. To normalize for different biomass levels, the optimum photosynthetic rate was divided by the maximum uptake velocity giving a range for the C:P maximum uptake from 1.2 to 206 for plankton samples of varying phosphate deficiency.

An In Situ Study of Cadmium and Mercury Stress in the Plankton Community of Lake 382, Experimental Lakes Area, Northwestern Ontario

Four in situ experiments with small-volume (28-L) enclosures were conducted in Experimental Lakes Area Lake 382 to assess the effects of inorganic mercury and cadmium on the plankton community. Additions of 0.9 × 10−8 mol Cd/L caused significant reductions of crustacean zooplankton density, zooplankton community similarity, zooplankton species diversity, and dissolved oxygen concentration over 3-wk periods. Additions of 1.0 × 10−8 mol Hg/L caused reductions similar to those of 0.9 × 10−8 mol Cd/L. Phytoplankton primary productivity was reduced by additions of 2.0 × 10−8 mol Hg/L but not by 1.0 × 10−8 mol Hg/L. On a molar concentration basis, the toxicities of inorganic mercury and cadmium were quite similar. Significant changes in lake plankton communities may occur at molar concentrations above 0.2 × 10−8 mol/L. Potentially toxic concentrations of cadmium may occur in many contaminated lakes, but toxic concentrations of mercury probably occur in few lakes.Key words: Precambrian Shield lakes, plankton communities, phytoplankton, zooplankton, cadmium, mercury toxicity

Prey selection by young trout fry (Salmo trutta)

Factors influencing the choice of invertebrate food by early feeding trout are sought, special attention being given to the dimensions of the prey. The stomach contents of fish of similar age feeding on lake plankton and drifting stream fauna are compared. Little consistent preference was displayed for the smaller planktonic organisms but prey size was of importance in the distribution of stream benthos among predators of different lengths. The width of the prey was of greater significance to selection than the mean volume or the area of the largest surface of the food items. When the fish were in obvious competition for food the correlation between predator length and all prey dimensions improved.

CHRYSOCHROMULINA BREVITURRITA SP. NOV., A NEW FRESHWATER MEMBER OF THE PRYMNESIOPHYCEAE1

ABSTRACTChrysochromulina breviturrita sp. nov. is described as a new haptonema‐bearing member of the freshwater Prymnesiophyceae. It is ca. three times larger than the only other known freshwater member of the genus (C. parva Lackey)and possesses a haptonema only ca. 0.2–0.3 as long as the haptonema of C. parva. Two equal flagella (1.5–2 as long as the haptonema), a large contractile vacuole, two parietal plasties, a single pyremid, nucleus, Chrysolaminarin‐like droplets and a food vacuole are features readily observed with the light microscope. Dried and shadoweast whole mounts examined with the electron microscope reveal the cell surface covered with two types of small, delicate scales: outer spined scales with a clubshaped terminus and with the spine anchored to a circular to oval base‐plate by 2–6 (7) branching arms; and, spineles oval plate scales with concentric lines and radiating ridges on one face and parallel ridges on the other. C. breviturrita has been found in nine lakes in Ontario (Canada). Pereliminary observations suggest that it is an important component of lake plankton and has probably not been delected in previous work, more because of its fragility than because of its scarcity. Living specimens are a prerequisite for initial identification, since cells frequently rupture and haptonemata are often lost when the organisms are killed with the commonly used fixatives.

Mercury and chlorinated hydrocarbons in plankton of Lake Päijänne, Finland

Plankton was sampled for residue analysis as different size fractions in the years 1972–1974 from four sub-areas of Lake Päijänne, Finland. Of the residues studied PCB was the greatest contaminant, the dry weight content being, on average, 290 μg/kg. The corresponding content of total mercury was 178 and of DDE + DDT (= Σ DDT) 91 μg/kg. Annual and regional differences were generally small. The Σ DDT content of the greatest size fraction (350 μm) was, on average, higher than in fractions 100, 50 and 25 μm. Correlation between the contents of PCB and Σ DDT was highly significant. The mercury contents were generally of the same order as marine values but smaller than those in polluted regions elsewhere. The contents of PCB and Σ DDT were generally lower in Lake Päijänne than in marine plankton.

Cybernetic mechanisms in lake plankton systems: how to control undersirable algae

TOXIC algal blooms represent a serious nuisance in lakes and ponds. Not only do they form floating scums and impart odours and tastes to the water, but they are also associated with the occurrence of dermatitis in our own species and fatal poisoning in livestock. To reduce algal levels, man resorts to various practices that range from chemical ‘control’ to artificial mixing of the lake1. Most of these have deleterious, if not immediately toxic, effects on the other compartments of the system as well. In this report safer alternatives are presented.

Plankton and primary production of the dystrophic lakes in Shiga Heights

Plankton and primary production of the dystrophic lakes in Shiga Heights

Heterotrophic bacteria and their relationship with plankton in a New Zealand freshwater lake

Abstract The viable heterotrophic bacteria of Lake Grasmere in inland Canterbury (43° 05 S, 171° 45 E) were studied. Numbers of bacteria in water above a spring were positively correlated with rainfall in the 7 days before sampling, but bacteria in open water and from over the macrophyte Elodea canadensis were not. There was some increase in the bacterial population in the water over E. canadensis in the autumn to winter months. Numbers of bacteria in the open water ranged from 55 to 1020 cells per millilitre, and were outnumbered by algae by a factor of between 4 and 34. The bacterial population tended to increase after blooms of zooplankton, but there was little or no response to changes in phytoplankton populations. Benthic bacteria rarely increased in numbers after the deposition of organic matter.

Plankton, Chemistry, and Physics of Lakes in the Churchill Falls Region of Labrador

Of 10 lakes and a reservoir in the Churchill Falls region of western Labrador studied in 1970–71, nine lakes were 12 m or less deep, humic, thermally unstratified, and had Secchi disc transparencies between 3.5 and 8.25 m. Maximum surface temperatures of 16–17 C in the nine lakes were generally reached by mid-August. Michikamau Lake (area 1980 km2, depth 84 m) rarely exceeded 12 C and had a Secchi disc transparency of 13 m. Conductivities and alkalinities (as CaCO3) ranged from about 13 μmho/cm and less than 6.5 mg/liter, for lakes draining granite, gneiss, or quartz bedrock, to about 30 and 15, for those draining gabbro or slate. Maximum live phytoplankton biomasses in 1970 ranged from 70 mg/m3, in Michikamau Lake, to 739 mg/m3, in Ossokmanuan Reservoir, and, in general, there was a positive correlation with conductivity. Diatoms were the most abundant group, in particular Asterionella formosa, Tabellaria fenestrata, and Rhizosolenia eriensis; however, flagellated Chrysophyta, mainly species of Dinobryon, were more abundant in the reservoir than in the natural lakes. Predominant zooplankters included Diaptomus minutus, Cyclops scutifer, Holopedium gibberum, Daphnia longiremis, D. galeata mendotae, and Bosmina coregoni. Maximum seasonal standing crops ranged from 1600 to 8910 individuals/m3, with the highest densities being found in the reservoir. The chemical and biological data suggested that the reservoir 8 yr after filling, showed little evidence of trophic upsurge and was possibly entering a period of trophic depression.

On the rotifer plankton of some East African lakes

Slightly alkaline and strongly alkaline lakes were investigated. A rather varied rotifer fauna was found in the first category, while in the second group, no rotifers at all or, at the most, only one species was found.

Surface nitrogen and plankton in Skaha Lake, British Columbia (Canada)

SummaryThis study (1970–71) of an oligotrophic lake subject to cultural enrichment indicates the presence of complex interrelations between plankton and nitrogen levels in surface waters. Generally inorganic nitrogen was high in the winter (0.4–0.5 ppm) and Iow in summer (less than 0‐1 ppm). However, in late July and August a large increase in nitrogen (1.5 ppm) was recorded. This correlated with the Gloeotrichia echinulata J. E. Smith ex P. Richt. bloom (Cyanophyceae) and the increase in nitrogen fixation, or nitrogenase activity (measured as acetylene reduction). It was calculated that the cyanophyte bloom could have contributed a minimum of 2350 kg nitrogen to the lake in August 1970 which is c. 62% of the nitrate‐nitrogen occurring at any time.

Effect of certain physico-chemical factors on the plankton of the nangal lake

Physical factors such as temperature of air and water and penetration of light, and chemical factors like pH, total alkalinity, dissolved oxygen and phosphates were studied for one year. Maximum and minimum temperatures of air were recorded in June 1969 and February 1969 respectively and that of water in September 1968 and February 1969. Dissolved oxygen was maximum in May and June 1969 and minimum in October, 1968. pH did not show much variation. Penetration of light was maximum in April 1969 and minimum in June, 1969. Maximum total alkalinity was observed in October 1968 and minimum in August 1968. Phosphates were absent in October 1968. Maximum abundance of zooplankton generally followed the phytoplankton bloom.

Grazing Rates and Food Selection in Diaptomus oregonensis (Copepoda) from Marion Lake, British Columbia

The filtration and ingestion rates of Diaptomus oregonensis females and stage V copepodids were examined in three experimental situations. When unialgal cultures of 20,000 cells per milliliter were offered to D. oregonensis the filtration rates remained constant for cells ranging from 120 to 10,000 µ3. When a mixture of diatoms was offered the animals did not filter cells ranging from 1 to 60 µ3 despite the fact that the cells in this size range were concentrated at about 20,000 per milliliter. When natural phytoplankton from Marion Lake was used as a food source, the filtration rates were low for cells smaller than 100 µ3, increased to a maximum of 12.9 ml per animal per day for cells ranging from 102 to 333 µ3, and remained constant with increased cell volume and decreased cell concentration. Several species of Cyclotella and Merismopedia were not removed from the Marion Lake plankton by D. oregonensis.

Strontium-90 concentration factors of lake plankton, macrophytes, and substrates.

The ratio of concentration of strontium-90 in living and inert lake components to that in lake water (concentration factors) was determined for plankton, macrophytes, and substrates in eutrophic, mesotropric-eutrophic, and dystrophic Latgalian lakes. Concentration factors of strontium-90 in aquatic organisms and substrates are higher in a dystrophic lake than in the other types.

Studies on British chytrids: XXVI. A critical examination of Zygorhizidium melosirae Canter and Z. planktonicum Canter

SUMMARY The paper is concerned with two species of the Chytridiales belonging to the genus Zygorhizidium which parasitize diatoms in the plankton of lakes. Z. melosirae, a parasite of Melosira, was first described by the writer in 1950. Later, in 1953, another chytrid belonging to this genus was found on Synedra and Asterionella. Although it showed a close resemblance to Z. melosirae it was nevertheless thought to be different and diagnosed as a separate species namely Z. planktonicum. However Paterson in 1958, after studying parasites belonging to the genus Zygorhizidium in several Michigan lakes, U.S.A., put forward the view that Z. melosirae and Z. planktonicum were synonymous. More recent findings made by the writer on the other hand have strengthened the original view that in fact two distinct species exist. Collections of Z. planktonicum from two new localities have been obtained and observations made on living material which are here described. Z. melosirae has also been re-investigated and additional data concerning its morphology are described. A Latin diagnosis of Z. planktonicum is provided in order to validate this species, and the diagnosis of Z. melosirae is emended. Evidence so far suggests that there are distinct host-parasite relationships separating the two species and some examples are described. In conclusion the writer retains Z. melosirae and Z. planktonicum as separate species.