The selection and ingestion of epilithic algae byNais elinguis (Oligochaeta: Naididae)

The gut contents ofNais elinguis in an organically polluted river were dominated by epilithic chlorophycean unicells and pennate diatoms with an average cell volume of 1.3 × 10³ µm³. The worm unselectively and opportunistically ingested unicellular algae up to a maximum length of 196 µm and a maximum volume of 24 × 10³ µm³, but colonial and filamentous algae were discriminated against. The morphometry of the pharynx ofN. elinguis probably determined the maximum size of algal cells which could be ingested.     

Composition and dynamics of epilithic algae in a forest stream at Shillong (India)

The seasonal dynamics of epilithic algae in a third order pristine forest stream were analyzed over a period of 2 years. Stream water was slightly acidic and nutrient poor. Encrusting, filamentous flocs, and filaments were found. Algal standing crop was high (mean concentration of Chl a 16–43 mg m^–2) in spring. Filamentous algae contributed most to standing crop. Diatoms made up over 85% by number of the epilithon. Blue-greens were abundant upstream, and chlorophytes downstream. This shift was ascribed to greater light availability downstream. The community was more diverse during spring. Water current was the most important variable regulating epilithon structure. Total phosphorus (TP), orthophosphate (O-PO _inf4 ^su3– ), silica (Si⁴⁺), nitrate (NO _inf3 ^su– ) and conductance correlated negatively with flow rate. Green algae showed a positive correlation to phosphorus during low and stable flow. During rapid runoff, diatoms were the most resistant forms. Seasonal change in the epilithic community was mainly regulated by fluctuations in flow rate.     

Seasonal succession of planktonic and epiphytic algae in a canal in Southern England

The standing crop of phytoplankton in a canal in southern England remained low during 1973 and 1974, seldom exceeding 5 × 10⁴ cells/1. Since phosphorus, nitrogen and silicon occurred abundantly in the water, competition with higher plants for some other substance must have limited development. Although the standing crop of epiphytic algae associated withNasturtium officinale andGroenlandia densa seemed to be limited by the number of attachment sites, this factor was of little importance in the case of algae attached toCladophora glomerata. Achnanthes minutissima v.cryptocephala was always predominant in the epiphytic assemblages, representing 50–8o% by numbers of the flora. The limited pool of predominant epiphytic taxa may have restricted the communities' ability to adapt to fluctuations in environmental conditions. The grazing of isopods, amphipods and molluscs probably never limited algal densities.     

Phytoplankton communities in navigation pool no. 7 of the Upper Mississippi River

A study of the phytoplankton community dynamics in Navigation Pool No. 7 of the Upper Mississippi River was conducted from May through October, 1982. The objectives of this study were to estimate total standing crops, determine the taxonomic composition and examine the seasonal succession of the phytoplankton community. Four sampling sites were established: two in Lake Onalaska, a large backwater lake on the Wisconsin side of the main channel; one in the main channel near Dakota, Minnesota; and one in the main channel just upstream from Lock and Dam No. 7.The phytoplankton communities at all sampling sites were dominated by diatoms except during July and August when a bloom of blue-green algae was observed. The dominant diatoms from May through mid-July were Melosira italica, Stephanodiscus niagarae, Stephanodiscus hantzschii, Stephanodiscus astrea, and Synedra ulna. Aphanizomenon flos-aquae and Microcystis aeruginosa were the most prevalent blue-green algae during the mid-summer bloom. The diatoms Melosira italica and Melosira granulata were dominant in September and October. Lesser amounts of green algae, cryptomonads and euglenoids were also observed at various times of the sampling period.Total standing crops based on cell volume were usually greatest at the Lock and Dam No. 7 site. The maximum standing crop (10.4 mm³ 1^–1) was observed at the Lock and Dam No. 7 site on 4 September; the minimum standing crop (0.4 mm³ 1^–1) was observed at the eastern Lake Onalaska site on the same date. Concentrations of nitrogen, phosphorus, and silica remained at high levels throughout the study period and did not appear to limit phytoplankton standing crops.     

Seasonal succession of the phytoplankton in the upper Mississippi River

Species composition and seasonal succession of the phytoplankton were investigated on the upper Mississippi River at Prairie Island, Minnesota, U.S.A. Both the numbers and volume of individual species were enumerated based on cell counts with an inverted microscope. A succession similar to algal succession in the local lakes occurred. The diatoms were dominant during the spring and fall and blue-green algae were dominant during the summer. The algal concentrations have increased up to 40 fold the concentrations of the 1920's, since the installation of locks and dams. The maximum freshweight standing crop was 4 mg · l^–1 in 1928 (Reinhard 1931), 13 mg · l^–1 in 1975 a wet year, and 47 mg · l^–1 in 1976, a relatively dry year with minimal current discharge. The diatoms varied from 36–99%, the blue-green algae from 0–44% and the cryptómonads from 0–50% of the total standing crop. The green algae were always present but never above 21% of the biomass. The dominant diatoms in recent years were centric -Stephanodiscus andCyclotella spp. (maximum 50,000 ml^–1). The dominant blue-green algae wereAphanizomenon flos-aquae (L.) Ralfsex Born.et Flahault andOscillatoria agardhii Gomont (maximum 800 ml^–1). These algal species are also present in local lakes. Shannon diversity values indicated greatest diversity of algae during the summer months.     

Influence of food availability and other factors on the composition,structure and density on a subarctic population of benthic invertebrates

The factors influencing the composition, structure and density of benthic invertebrate communities in Yellowknife Bay in the Canadian subarctic were determined between June 1975 and April 1977. Attached algae, primarily Fragilaria vaucheriae, Fragilaria pinnata, Cymbella ventricosa and Cocconeis placentula were ingested in large numbers by several dominant species including the oligochaetes Rhyacodrilus sodalis, Lumbriculus variegatus and Limnodrilus claparendeianus and the mollusc Valvata sincera helicoidea. Although up to 7 × 10⁵ cells/oligochaeta, representing 65% by volume of the gut contents, were recorded for littoral zone populations, specimens in the profundal zone contained < 7.5 × 10⁴ cells in their guts. V. sincera helicoidea also ingested large numbers of attached algae (up to 2.3 × 10⁴ cells/animal), these representing 15–18% by volume of the gut contents. Consequently, multiple regression analysis indicated that the availability of attached algae was the major factor influencing the benthic communities. While 31–64% of the population variability could be accounted for by this factor, other parameters such as phytoplankton availability, water depth, temperature, dissolved oxygen levels, total amount of food in the gut, and the organic content of the sediments had little if any direct effect on the benthic populations.     

The benthic macro-algae of Georgian Bay,the North Channel and their drainage basin

Thirty-nine subgeneric taxa of macroalgae have been collected from 83 sites in Georgian Bay, the North Channel and their drainage basin. There were 15 species in the Bay and Channel and 32 species in streams, rivers and impoundments in the basin. Only 8 of the Bay and Channel species were also found in the watershed. Cladophora glomerata was the most important species in Georgian Bay and the North Channel, having an estimated 640 × 10³ m² cover and 19 × 10⁴ kg fresh weight standing crop. However, this species was largely concentrated on the southwestern shorelines of these water bodies. Its distribution along the northeastern shoreline appears to be limited by total ion and phosphorus levels. Chara globularis/vulgaris was the subdominant taxon in Georgian Bay and the North Channel with an estimated 70 × 10³ m² cover and 15 × 10³ kg fresh weight biomass. This species was more widely distributed than C. glomerata. No other taxon contributed significantly to the standing crop including the frequently occurring Ulothrix zonata, Zygnema spp. and Spirogyra spp. The maximum benthic macroalgal biomass was estimated to be approximately 10% of the phytoplankton biomass.     

Struttura e biomassa dei popolamenti fitoplanctonici del Lago Omodeo (Sardegna centrale)

Abstract

Composition and biomass of phytoplanktonic communities of Lago Omodeo (Central Sardinia).—A qualitative and quantitative study has been made on the phytoplankton of Lago Omodeo. The algal associations are typical of eutrophic waters. The dominant blue-green algae in summer and autumn were: Chroococcus dispersus, Microcystis flos-aquae, Aphanizomenon flos-aquae, Anabaena flos-aquae, Anabaena planctonica; dominant in winter and spring the diatom Melosira distans. The mean standing crop of algae for the trophogenic zone was 9.2 mm³/l; a maximum crop of 53 mm³/l was recorded in August during a Microcystis bloom.     

Filamentous green algae in freshwater streams on Signy Island,Antarctica

The streams of Signy Island are varied and extremely seasonal environments. Water flows from November/December to March/April; streams are frozen for the rest of the year. Streams usually flow through small, barren catchments and are nutrient poor, though they may be enriched by dense summer populations of seabirds and seals. Temperatures are consistently low. Stream depth is maximal during the spring melt period, declining over the course of the summer. Vegetation is exclusively algal, and filamentous chlorophytes from a particularly conspicuous component. Small numbers of vegetative cells survive the long frozen period in situ. A steady increase in standing crop results in a maximum 2 to 3 months after flow begins. Sloughing is the major loss mechanism and grazers are effectively absent. Three taxa of filamentous algae are common in Signy streams, species of Zygnema, Mougeotia and Klebsormidium. The distributions of these algae are described and related to physical and chemical features of their environment.     

Observations on standing crops of epipelic and epipsammic algal communities in Shear Water,Wilts

Methods of estimating the standing crops of epipsammic diatoms have been evaluated and compared with those used for epipelic algal crops.

Good correlations between chlorophyll a content and cell counts were obtained for epipelic populations, but because of the presence of large numbers of decaying cells, inseparable from living cells, such correlation was not obtained with epipsammic algae, even after correction of the pigment estimates for the presence of pheophytin a. The standing crop of epipsammic algae was at all times greater than that of epipelic algae at the same sampling station, and this was attributed to the differential effects of sediment disturbance by burrowing animals and water movements.     

A study of the suspended algae in the River Derwent,Derbyshire, U.K.

Studies of the composition and abundance of algae suspended in the water of the River Derwent, Derbyshire, were made during 1983. Samples were collected at intervals of 2–3 weeks from 6 sites on the lower reaches of the river. Variations in both composition and abundance of suspended algae occurred with variations in flow. At the uppermost sites cell densities were generally low (<500 cells ml^–1) and the algae consisted mainly of dislodged benthic diatoms. The density in suspension of these algae of benthic origin increased with flow. At downstream sites a true potamoplankton developed; during the summer this consisted chiefly of centric diatoms with Chlorophyta and Cryptophyta. Even at the lowermost site, the maximum recorded density of cells (3 860 cells ml^–1) and cell load (30 × 10⁹ cells s^–1) were lower in the Derwent than in some other British rivers. However, the cell density could still represent a substantial part (up to 32%) of the total particle density in the river.     

Eutrophication of the salt valley reservoirs, 1968–73 I. The effects of eutrophication on standing crop and composition of phytoplankton

A study was carried out over a period of six years to determine the effects of eutrophication upon standing crop and composition of the phytoplankton in four recently constructed flood control reservoirs in Nebraska. Water samples collected weekly during June, July, and August from 1968–73 were analyzed for chlorophyll a, phytoplankton composition, and phytoplankton abundance. Total volume of phytoplankton was calculated from appropriate dimensions and formulae. Inorganic turbidity in one reservoir was an important factor regulating the size and composition of the phytoplankton standing crop. In that reservoir diatoms were the most important component of the phytoplankton community during those years in which inorganic turbidity was greatest. When inorganic turbidity declined, blue-green algae became dominant.In the clear-water reservoirs chlorophyll a, phytoplankton number, and phytoplankton volume were significantly correlated with reservoir age, with the oldest containing chlorophyll a concentrations up to 247 mg/m³ and mean phytoplankton volumes up to 329 mm³/l, values sufficient to place it in the hypereutrophic category. The reservoirs had 2–6 times more chlorophyll a present at the end of the study than at the beginning, with the increase being greatest in the newest reservoir. Phytoplankton volume was significantly correlated with chlorophyll a in all the reservoirs.Blue-green algae quickly became established as community dominants in the reservoirs, making up over 80 percent of the phytoplankton volume in the newest reservoir by the second year of its existence. In the other clear-water reservoirs, blue-greens usually constituted over 95 percent of the total phytoplankton volume in summer. three genera, Microcystis, Aphanizomenon, and Anabaena, were responsible for virtually the entire standing crop of blue-greens in all the reservoirs.     

BENTHIC ALGAE OF SOUTHERN BAFFIN ISLAND. III. EPILITHIC AND EPIPHYTIC COMMUNITIES1

Blue-green algae–mainly Aphanocapsa pulchra (Kz.) Rabh., Oscillatoria tenuis Ag., Schizothrix muelleri Naeg., and Lyngbyn spp.—were predominant, in the epilithic communities of Baffin Island rivers and lakes during 1972, usually accounting for more than 90% by numbers and volume of the total flora. Diatoms were only important early in the growing season (June) with Achnanthes marginulata Grun., A. kriegeri Krasske, and Tabellaria flocculosa (Roth) Kz. being most common. Standing crop in one river increased from near 0 in June to 6.0 × 10⁴ cells/cm² (2.2 × 10⁸μ³/cm²) in July and back to near 0 again by October. Low levels of nitrate nitrogen probably limited algal numbers, while flooding, light, and grazing by herbivores appeared to have little effect. Changes in algal standing crop in the lakes followed much the same pattern as outlined above. However, the maximum amount of algae was considerably greater than that recorded from the rivers, reflecting the greater availability of nutrients. Lyngbya nana Tild. was the main algal species attached, to filaments of Mougeotia sp., reaching greatest development (5.0 × 10⁴ filaments/cm²) during September. On the other hand, diatoms–mainly Ceratoneis arcus Kz. and varieties, Fragilaria spp., and Synedra spp.–were predominant in the community floating among the filaments with maximum standing crop (64.48 × 10⁶ cells/g dry weight of Mougeotia) occurring in July. The small diameter of the Mougeotia filaments was probably the main factor limiting the size of both the attached and free-floating communities.     

Acidity status and phytoplankton species richness,standing crop,and community composition in Adirondack,New York,U.S.A. lakes

The mid-summer phytoplankton communities of more than 100 Adirondack lakes ranging in pH from 4.0 to 7.2 were characterized in relation to 25 physical-chemical parameters. Phytoplankton species richness declined significantly with increasing acidity. Acidic lakes (pH < 5.0) averaged fewer than 20 species while more circumneutral waters (pH > 6.5) averaged more than 33 species. Phytoplankton abundance was not significantly correlated with any of the measured physical-chemical parameters, but standing crop parameters, i.e., chlorophyll a and phytoplankton biovolume, did correlate significantly with several parameters. Midsummer standing crop correlated best with total phosphorus concentration but acidity status affected the standing crop-phosphorus relationship. Circumneutral waters of low phosphorus content, i.e. < 10 µg·1^–1 TP, averaged 3.62 µg·1^–1 chlorophyll a whereas acidic lakes of the same phosphorus content averaged only 1.96 µg·1^–1 chlorophyll a. The midsummer chlorophyll content of lakes of high phosphorus content, i.e. > 10 µg·1^–1 TP, was not significantly affected by acidity status.Adirondack phytoplankton community composition changes with increasing acidity. The numbers of species in midsummer collections within all major taxonomic groups of algae are reduced with increasing acidity. The midsummer phytoplankton communities of acidic Adirondack lakes can generally be characterized into four broad types; 1) the depauperate clear water acid lake assemblage dominated by dinoflagellates, 2) the more diverse oligotrophic acid lake community dominated by cryptomonads, green algae, and chrysophytes, 3) the productive acid lake assemblage dominated by green algae, and 4) the chrysophyte dominated community. The major phytoplankton community types of acid lakes are associated with different levels of nutrients, aluminum concentrations, and humic influences.     

Importance of algae in the diet of the oligochaetes Lumbriculus variegatus (MÜller) and Rhyacodrilus sodalis (Eisen)

Summary The importance of algae in the diet of the oligochaetes Lumbriculus variegatus and Rhyacodrilus sodalis was determined from cellections made in a eutrophic bay from April 1977 to April 1978. During the summer, algae represented 70–85% of the gut contents of both species. The most frequently ingested algae were Cymatopleura elliptica, Cymbella spp., Epithemia turgida, Pinnularia spp., and Synedra ulna. Almost all species were consumed in proportion to their abundance in the environment. However, Nostoc pruniforme and Nostoc verrucosum were not eaten due to size selection. The high level of algal consumption exhibited by the oligochaetes was primarily related to the large standing crop of algae on the sediments. During the winter, when algal densities were low in the environment, detritus and associated bacteria were the major food source.     

Seasonal variation in biomass and photosynthetic activity of epilithic algae on a rock at the upper littoral area in the north basin of Lake Biwa, Japan

Vertical distributions of biomass and the photosynthetic activity of epilithic algae were observed seasonally with regard to their physical and chemical parameters along a rocky shoreline of the upper littoral area in the north basin of Lake Biwa. Chlorophyll a amounts in epilithic algae showed a marked change with depth from spring to early summer. The algal biomass showed higher values on the lower part of a large rock in early spring, and gradually increased on the upper part as a result of the growth of Spirogyra sp., a filamentous Chlorophyceae. This growth seems to be associated with a rise in water temperature, with the biomass at the upper depths seeming to be affected by a hydraulic disturbance. The standing crop of epilithic algae showed a maximum value in June and declined to a minimum in August because of the corresponding proliferation or disappearance of Spirogyra as well as changes in the water level. The maximum value of the assimilation number calculated from the potential photosynthetic rate of epilithic algae was obtained at the lower depths in June when Spirogyra grew vigorously. Appreciably high assimilation numbers were also observed in summer and fall, although chlorophyll a amounts were low. The present study is the first in a series to clarify the contribution of epilithic algae on rocky areas to productivity throughout the entire littoral ecosystem.     

Periphyton production and grazing by chironomids in Alderfen Broad, Norfolk

The standing crops of periphyton were measured on dead Typha stems and glass rods in a small, eutrophic lake from February to November. Chironomid larvae were also counted on the Typha stems; very few were present on the glass rods. The standing crop of periphyton on the Typha stems fell from 1.8 mg cm⁻² in early April to nearly zero in November. On the glass rods the periphyton reached a peak of 1.93 mg cm⁻² in late May and 1.94 mg cm⁻² in July, thereafter falling to a steady level of 1.6 mg cm⁻². The population of chironomids showed a peak in late May and then declined. The alimentary canals of chironomids collected fromTyphastems contained diatoms and filamentous algae so it appeared that chironomids were grazing down the periphyton. Chironomids moved on to theTyphastems in spring and returned to the mud in autumn. The periphyton is a richer source of essential amino acids than the mud, so that a movement from mud to reedstems in spring may increase the rates of growth and metamorphosis of the larvae. A crude production estimate gave a net primary production of periphyton of 170 mg dry wt m⁻² day⁻¹; the periphyton, however, would have contained bacteria and many small animals as well as algae.     

The dominant attached filamentous algae of Georgian Bay,the North Channel and Eastern Lake Huron: Field ecology and biomonitoring potential during 1980

Field investigations during the ice-free period of 1980 confirm that the dominant attached filamentous algae in the Canadian waters of Lake Huron are the green algae Ulothrix zonata and Cladophora glomerata, and the red alga Bangia atropurpurea. It is believed that nutrient availability limits the distribution of these algae, while temperature controls their seasonal periodicity. Because of favourable physical characteristics, the study area represents a vast potential habitat for attached filamentous algae. It is expected that eastern Georgian Bay, in particular, will suffer significant environmental degradation from the growth of Cladophora unless existing phosphorus levels are maintained indefinitely (i.e., < 0.005 mg total P 1^–1). Attached filamentous algae accumulate (10³ to 10⁵ x) a variety of elements primarily in proportion to availability in the surrounding water. The occurrence of maximum algal metal concentrations at municipal waste water outfalls, river mouths and harbour areas (e.g., in µg g^–1, Cr 29.0, Cu 46.4, Ni 34.0, Pb 55.0) is indicative of discrete source loadings, while elevated levels at remote sites in eastern Georgian Bay (e.g., in µg g^–1, Cr 12.0–15.5, Cu 18.0, Ni 15.0–16.0, Pb 8.5–8.8) are suggestive of generalized loadings from the Canadian Shield, possibly due to the effects of acidic precipitation.     

Physiological adsorption of Sulfolobus acidocaldarius on coal surfaces

Summary The adsorption of Sulfolobus acidocaldarius on bituminous coal surfaces and the respiration rate during adsorption at 70° C were enhanced at pH 1.0–2.0, in comparison with those at pH 3.0–5.0. The maximum number of bacterial cells adsorbed per unit area of coal attained a maximum (1.4 × 10¹¹ cells/m²) at pH 2.0. The rate of desulphurization at pH 2.2–2.5 was higher than at other pHs tested. Micrographs of S. acidocaldarius obtained by TEM and SEM indicated that the cells were adsorbed to the coal surfaces by extracellular slime. Specific inhibitors of membrane-bound ATPase (NaF, 20 mm) and respiration (NaN₃, 1 mm; KCN, 1 mm) had pronounced effects on suppressing adsorption. The amount of S. acidocaldarius adsorbed decreased when the coal particles were leached in advance with 2.0 m HNO₃. These facts lead to the conclusion that the adsorption of S. acidocaldarius on coal surfaces requires physiological activity relatd to respiration or energy conversion. Offprint requests to: V. B. Vitaya     

Epiphytic diatoms of the inshore marine area near Davis Station

Collections of macrophytic algae from the subtidal and lower intertidal regions were processed to observe the diatom epiphytes both by light and scanning electron microscopy. For the purpose of comparison some samples of the sub-ice assemblage were also collected and processed similarly. The standing crop of epiphytes was high throughout the winter as well as the summer but the community composition varied depending upon the collection site and the morphology of the host macrophyte. The genus Cocconeis was ubiquitous achieving densities approaching 10⁵ cells cm⁻² and surpassed only by Nitzchiawith a density of twice that amount on one sample.