Planktonic Algae Research Articles

The recent invasion of Rutilus rutilus (L.) (Pisces: Cyprinidae) in a large South- Alpine lake: Lago Maggiore

Very recently, a common cyprinid fish species at northern latitude, the roach (Rutilus rutilus L.) has been observed in the large south-alpine Lago Maggiore for the first time. The colonization of the lake has the characteristics of an invasion. In order to investigate this new fish population, benthic multi-mesh and commercial gill nets were used to sample fish in a wide gulf in the central part of the lake (Golfo Borromeo) from February to October 2006. In total 779 roach (TL: 5.5 – 38.8 cm) were caught, aged, sexed and stomach analyzed. Fecundity was assessed by counting the eggs in ripe gonads of females of age 3 and 4. The roach have become clearly the dominant species in the catches, constituting over 70% of the biomass and 70% of the numbers caught. None of the roach exceeded 8 years in age. They grow very fast (Φ' = 2.55) and have high fecundity (Fabs = 13740 ±4700 S.D. at age 3 and Fabs = 14768 ±5642 S.D. at age 4). The diet spectrum is wide and characterized by a strong seasonality. In early spring algae (benthic and planktonic algae), benthos and detritus prevail, whereas in summer zooplankton is the most frequent food item. In autumn roach switch back to benthos and detritus. Algae occur more frequently in young specimens while zooplankton, benthos and detritus in adults. The roach population is practically unimpacted by fishing. The minimum legal mesh size (25 mm) of gillnets, used by commercial fishermen, selects roach at the mean LT of 21.2 cm, which is over its length at maturity. The results suggest that roach established a viable population in Lago Maggiore less than a decade ago and rapidly became one of the dominant (if not the dominant) fish species. The possible consequence for the fish fauna in general and for the ecological status of the whole lake is briefly discussed.

Inhibition of photosynthesis in cyanobacteria and plankton algae by the bacterium Brevibacillus laterosporus metabolites

Inhibition of photosynthesis in cyanobacteria and plankton algae by the bacterium Brevibacillus laterosporus metabolites

High‐frequency measurements of productivity of planktonic algae using rugged nondispersive infrared carbon dioxide probes

We have constructed a system based on commercially available inexpensive NDIR CO2 sensors to continuously monitor CO2 concentrations in water bodies. Here we demonstrate its use in a boreal humic lake. With the system, we collect high frequency data with a 10‐min time resolution for determination of CO2 consumption and production. We use and modify the computational methods commonly used in forest ecology to enable characterization of aquatic primary production. To demonstrate the advantages of the method, we present the results against the observations from the long‐term monitoring program applying traditional bottle methods. With the probes, we can detect a clear, photosynthesis‐driven daily pattern in the CO2 concentration and determine the CO2 consumption or production resulting in more than a 10‐fold improvement in the time resolution when compared with traditional incubation methods. The measuring frequency is high enough to determine the dependence of photosynthesis on irradiance. The high‐frequency data highlights the inherent problems of discrete bottle incubations and bring into question their reliability. Our free water approach yielded productivity and mineralization rates that were clearly higher than obtained with incubations.

Fungal infection for cyanobacterium Anabaena smithii by two chytrids in eutrophic region of large reservoir Lake Shumarinai, Hokkaido, Japan

Fungal infection of the filamentous cyanobacterium Anabaena smithii was observed in Lake Shumarinai in 2004–2006. Two fungal species were found to parasitize the specialized cells of A. smithii. These fungi might not correspond to the chytrid species that the previous studies reported as the parasites for Anabaena species. One fungus showed selective attachment to the akinete (akinete type). The filaments parasitized by this fungus increased in August 2004 and October 2006, when akinete and filament densities also increased. The maximum percentage of parasitized filaments was 3.2% of all filaments in October 2006. The other fungus was usually attached to the heterocyst (heterocyst type). The filaments parasitized by this fungus increased in October from 2004 to 2006. The maximum percentage of parasitized filaments was 20.6% in October 2004. The biomass of A. smithii was not suppressed by akinete-type fungus because of the low percentage of parasitized filaments. The heterocyst-type fungus might disturb the nitrogen fixation, but its effect was negligible due to a high concentration of available nitrogen for planktonic algae in Lake Shumarinai.

Long term trend of chemical oxygen demand in Saroma-ko Lagoon, Japan; possible effects of climatic warming

A trend of shortening duration of ice coverage has been reported in many rivers, ponds and lakes around the world due to climatic warming. The shortening will have much influence on organic production due to the greater supply of light intensity and hence on water quality. Chemical Oxygen Demand (COD), a useful measure of water quality, has been monitored over the past thirty years in Saroma-ko Lagoon, a boreal lake in Japan characterized by wintertime ice coverage. Here the data set of water quality in the lagoon is analyzed to reveal long-term trends in COD and the influence of climatic warming on such trends. There has been a significant increasing trend, caused primarily by an abrupt increase in the early 1990s. However, the increase could not be explained by the increased load of organic matter on the lagoon from the river basin and organic production in the lagoon. On the other hand, periods of freezing of the entire surface have tended to be shorter with inevitable thinning of ice over the past forty years, probably due to climatic warming. Ice and planktonic algae are exposed to the low light intensity in situ, which is not optimum for the algal production of organic matter. The shortening and thinning should thus bring an improvement in ambient light conditions for algae, resulting in an increase of organic matter in winter. Most of the organic matter possibly remains even after spring because of the low water temperature. It is highly possible that climatic warming promotes deterioration in water quality in ice-covered lakes.

Long term trend of chemical oxygen demand in Saroma-ko Lagoon, Japan; possible effects of climatic warming

AbstractA trend of shortening duration of ice coverage has been reported in many rivers, ponds and lakes around the world due to climatic warming. The shortening will have much influence on organic production due to the greater supply of light intensity and hence on water quality. Chemical Oxygen Demand (COD), a useful measure of water quality, has been monitored over the past thirty years in Saroma-ko Lagoon, a boreal lake in Japan characterized by wintertime ice coverage. Here the data set of water quality in the lagoon is analyzed to reveal long-term trends in COD and the influence of climatic warming on such trends. There has been a significant increasing trend, caused primarily by an abrupt increase in the early 1990s. However, the increase could not be explained by the increased load of organic matter on the lagoon from the river basin and organic production in the lagoon. On the other hand, periods of freezing of the entire surface have tended to be shorter with inevitable thinning of ice over the past forty years, probably due to climatic warming. Ice and planktonic algae are exposed to the low light intensity in situ, which is not optimum for the algal production of organic matter. The shortening and thinning should thus bring an improvement in ambient light conditions for algae, resulting in an increase of organic matter in winter. Most of the organic matter possibly remains even after spring because of the low water temperature. It is highly possible that climatic warming promotes deterioration in water quality in ice-covered lakes.

Winter phytoplankton communities in different depths of three mesotrophic lakes (Łęczna-Włodawa Lakeland, Eastern Poland)

AbstractPhytoplankton samples were collected from three mesotrophic lakes: Piaseczno, Rogóźno and Krasne during winter seasons (from January to March). The samples were analyzed for species analysis and abundance of planktonic algae in relation to different depths of water column (0–7 m). Selected water physical-chemical parameters were also measured. Abundance of phytoplankton depended strongly on the thickness of snow and ice cover or mixing conditions. The maximal phytoplankton total number reached about 5 × 106 ind. L−1 beneath the clear ice in the Krasne Lake, minimal numbers were recorded under the thick snow and ice layers in the Piaseczno Lake (2 × 103 ind. L−1). The winter phytoplankton communities were dominated by flagellates principally cryptomonads (Cryptomonas spp. Rhodomonas minuta), euglenophytes (Trachelomonas volvocina, T. volvocinopsis), dinoflagellates (Peridinium bipes, Gymnodinium helveticum) and chrysophytes (Mallomonas elongata, M. akrokomos, Dinobryon sociale) or non-motile small species of blue-green algae (e.g. Rhabdoderma lineare, Limnothrix redekei), diatoms (Stephanodiscus spp., Asterionella formosa), and green algae (e.g. Scenedesmus spp., Monoraphidium spp.). Phytoplankton abundance and structure showed differentiation during the winter season and along the water column as well.

Postglacial sedimentary record and history of West Hawk Lake crater, Manitoba

West Hawk Lake (WHL) is located within the glacial Lake Agassiz basin, 140 km east of Winnipeg, Manitoba. The small lake lies in a deep, steep-sided, meteorite impact crater, which has been partly filled by 60 m of sediment that today forms a flat floor in the central part of the basin below 111 m of water. Four cores, 5–11 m in length, were collected using a Kullenberg piston gravity corer. All sediment is clay, contains no unconformities, and has low organic content in all but the upper meter. Sample analyses include bulk and clay mineralogy, major and minor elements, TOC, stable isotopes of C, N, and O, pollen, charcoal, diatoms, and floral and faunal macrofossils. The sequence is divided into four units based mainly on thickness and style of lamination, diatoms, and pollen. AMS radiocarbon dates do not provide a clear indication of age in the postglacial sequence; possible explanations include contamination by older organic inwash and downward movement of younger organic acids. A chronological framework was established using only selected AMS dates on plant macrofossils, combined with correlations to dated events outside the basin and paleotopographic reconstructions of Lake Agassiz. The 822 1-cm-thick varves in the lower 8 m of the cored WHL sequence were deposited just prior to 10,000 cal years BP (∼8,900 14C years BP), during the glacial Lake Agassiz phase of the lake. The disappearance of dolomite near the top of the varved sequence reflects the reduced influence of Lake Agassiz and the carbonate bedrock and glacial sediment in its catchment. The lowermost varves are barren of organisms, indicating cold and turbid glacial lake waters, but the presence of benthic and planktonic algae in the upper 520 varves indicates warming; this lake phase coincides with a change in clay mineralogy, δ18O and δ13C in cellulose, and in some other parameters. This change may have resulted from a major drawdown in Lake Agassiz when its overflow switched from northwest to east after formation of the Upper Campbell beach of that lake 9,300–9,400 14C years ago. The end of thick varve deposition at ∼10,000 cal years BP is related to the opening of a lower eastern outlet of Lake Agassiz and an accompanying drop in West Hawk Lake level. WHL became independent from Lake Agassiz at this time, sedimentation rates dropped, and only ∼2.5 m of sediment was deposited in the next 10,000 years. During the first two centuries of post-Lake Agassiz history, there were anomalies in the diatom assemblage, stable O and C isotopes, magnetic susceptibility, and other parameters, reflecting an unstable watershed. Modern oligotrophic conditions were soon established; charcoal abundance increased in response to the reduced distance to the shoreline and to warmer conditions. Regional warming after ∼9,500 cal years BP is indicated by pollen and diatoms as well as C and O isotope values. Relatively dry conditions are suggested by a rise in pine and decrease in spruce and other vegetation types between 9,500 and 5,000 cal years BP (∼8,500–4,400 14C years BP), plus a decrease in δ13Ccell values. After this, there was a shift to slightly cooler and wetter conditions. A large increase in organic content and change in elemental concentration in the past several thousand years probably reflects a decline in supply of mineral detritus to the basin and possibly an increase in productivity.

Colony induction and growth inhibition in Desmodesmus quadrispina (Chlorococcales) by allelochemicals released from the filamentous alga Uronema confervicolum (Ulotrichales)

In biofilms, the competition between microorganisms for light, nutrients and space is extreme. Moreover, planktonic algae can be considered as competitors insofar as they decrease the available light for the benthic algae. One of the strategies employed by microorganisms to eliminate competitors is the release of inhibiting compounds, a process known as allelopathy. Here we demonstrate that a benthic/epiphytic alga, Uronema confervicolum, produces allelopathic compounds that induce oxidative stress and growth inhibition in the planktonic Desmodesmus quadrispina. Some of these compounds can also trigger the formation of colony in D. quadrispina. As colonies have higher sedimentation rates than unicells, their induction by U. confervicolum might decrease shading. This study is the first report of colony induction in the context of alga-alga interaction. Our results also suggest the implication of mitogen-activated protein (MAP) kinases in the transduction of the signal leading to the formation of reactive oxygen species in the cells. A comparison with allelochemicals from another planktonic green alga, Monoraphidium aff. dybowski, emphasizes the specificity of colony induction by U. confervicolum, in contrast with oxidative stress which is induced by several compounds. The reciprocal production of inhibiting compounds by D. quadrispina makes this interaction an interesting example of co-evolution between two microorganisms belonging to different compartments of the ecosystem.

Diversity and Distribution of Algae in Wetlands of the Rio Grande do Sul, Brazil

Surveys of algae diversity and distribution involving the Rio Grande do Sul State was completely unknown. The main goals of this study were to analyze the richness and distribution of the algae genera in wetlands of Rio Grande do Sul and to compare the algal composition among five geomorphologic provinces and between different wetland classes and types. A total of 146 wetlands were sampled within the five geomorphologic provinces of Rio Grande do Sul: Coastal Plain, Central Depression, Cristaline Shield, Highlands and Pampas. One single visit took place in each wetland from March to October 2002. A total of 107 genera of algae were found, distributed along five divisions: Cyanophyta, Heterokontophyta, Dinophyta, Euglenophyta, and Chlorophyta. The highest number of genera was found in Chlorophyta (52). Most of the observed genera presented a sporadic and occasional distribution in the wetlands of Rio Grande do Sul. The wetland algal composition of Cristaline Shield, Central Depression and Pampas was similar. While the planktonic algae were more associated with the aquatic bed vegetation (Gymnodinium, Scenedesmus and Ankistrodemus), and permanent wetlands (Dictyosphaerium and Ankistrodesmus), the periphytic algae were more associated with the emergent vegetation (Oscillatoria and Encyonema), and intermittent wetlands (Nostoc). The results showed a high richness and wide geographic distribution of the algae in wetlands of Rio Grande do Sul.

Plankton Algae of Water Bodies of the Molodo River Basin (Russia, Yakutiya)

Plankton Algae of Water Bodies of the Molodo River Basin (Russia, Yakutiya)

Peculiarities of the plankton diversity in the Southern Bug River in the region of the city of Vinnitsa (Ukraine)

The composition of the planktonic algae in the Southern Bug River in the region of the city of Vinnitsa is studied, and specificity of its systematic diversity is estimated. The dominant algo complexes are revealed, and their quantitative parameters are presented. The reasons of transformation in the phytoplankton species composition of different areas of the river and a degree of their pollution by the presence of algae-indicators are discussed.

Evaluation of Barley Straw and a Commercial Probiotic for Controlling Prymnesium parvum in Fish Production Ponds

AbstractSince 2001, the ichthyotoxic microalga Prymnesium parvum has caused major fish kills in 13 U.S. states, including Texas, raising concerns about its impacts on hatchery fish production, sport fisheries, and local economies. We investigated the efficacy of two natural products, barley Hordeum vulgare straw and the probiotic Liquid Live Micro‐Organisms (LLMO) System in controlling P. parvum and its ichthyotoxicity. Their effects on factors essential for successful production of fingerling fish (i.e., water quality, nutrient levels, phytoplankton biomass and composition, zooplankton density and composition, and fingerling fish production) were also evaluated. Barley straw and LLMO were individually tested during summer and fall 2004 in hatchery ponds for 140 d (experiment 1). Four ponds were treated with barley straw applied once at the beginning of the study at 252 kg/ha, and four ponds received LLMO at a rate of 1 L/56,718 L of pond water at 2‐week intervals throughout the study. Another four ponds were untreated and served as the control. Barley straw was further tested at 280 kg/ha in winter 2005 for 93 d (experiment 2). These barley straw treatment rates were similar to those used in other studies, and the LLMO rate was recommended by the supplier. In both experiments, P. parvum blooms did occur. Neither barley straw nor LLMO had a significant effect on P. parvum density, toxin levels, or ichthyotoxicity at the rates used in this study. Similarly, neither barley straw nor LLMO affected any of the other variables investigated. Our results do not support reports that barley straw and LLMO can control planktonic algae.

Do Nutrients Limit Algal Periphyton in Small Blackwater Coastal Plain Streams?1

Abstract: We examine the potential for nutrient limitation of algal periphyton biomass in blackwater streams draining the Georgia coastal plain. Previous studies have investigated nutrient limitation of planktonic algae in large blackwater rivers, but virtually no scientific information exists regarding how algal periphyton respond to nutrients under different light conditions in smaller, low‐flow streams. We used a modification of the Matlock periphytometer (nutrient‐diffusing substrata) to determine if algal growth was nutrient limited and/or light limited at nine sites spanning a range of human impacts from relatively undisturbed forested basins to highly disturbed agricultural sites. We employed four treatments in both shaded and sunny conditions at each site: (1) control, (2) N (NO3‐N), (3) P (PO4‐P), and (4) N + P (NO3‐N + PO4‐P). Chlorophyll a response was measured on 10 replicate substrates per treatment, after 15 days of in situ exposure. Chlorophyll a values did not approach what have been defined as nuisance levels (i.e., 100‐200 mg/m2), even in response to nutrient enrichment in sunny conditions. For Georgia coastal plain streams, algal periphyton growth appears to be primarily light limited and can be secondarily nutrient limited (most commonly by P or N + P combined) in light gaps and/or open areas receiving sunlight.

Primary production and chlorophyll distributions in the subtropical and tropical waters of the Atlantic Ocean in the autumn of 2002

In October and November 2002, high and relatively high values of the chlorophyll a concentration at the sea surface (Cchl) were observed in the English Channel (0.47 mg/m3), in the waters of the North Atlantic Current (0.25 mg/m3), in the tropical and subtropical anticyclonic gyres (0.07–0.42 mg/m3), and also in the southwestern region of the southern subtropical anticyclonic gyre (usually 0.11–0.23 mg/m3). The central regions of the southern subtropical anticyclonic gyre (SATG) and the North Atlantic tropical gyre (NATR) were characterized by lower values of Cchl (0.02–0.08 mg/m3 for the SATG and 0.07–0.14 mg/m3 for the NATR). At most of the SATG stations, the values of the surface primary production (Cphs) varied from 2.5 to 5.5 mg C/m3 per day and were mainly defined by the fluctuations of Cchl (r = +0.78) rather than by those of the assimilation number (r = +0.54). The low assimilation activity of phytoplankton in these waters (1.3–4.6 mg chl a per hour) pointed to a lack of nutrients. An analysis of the variability of their concentration and the composition of photosynthetic pigments showed that, in the waters north of 30° N, the growth of phytoplankton was mostly restricted by the deficiency of nitrogen, while, in more southern areas, at the majority of stations (about 60%), the phosphorus concentrations were the minimum. At the low concentrations of nitrates and nitrites, ammonium represented itself as a buffer that prevented planktonic algae from extreme degrees of nitric starvation. In the tropical waters and in the waters of the SATG, the primary production throughout the water column varied from 240 to 380 mg C/m2 30° per day. This level of productivity at stations with low values of Cchl (<0.08 mg/m3) was provided by a well-developed deep chlorophyll maximum and a high transparency of the water. The light curves of photosynthesis based on in situ measurements point to the high efficiency of utilizing the penetrating solar radiation by phytoplankton on cloudy days.

Interactions of planktonic algae and bacteria: effects on algal growth and organic matter dynamics

Interactions between phytoplankton and heterotrophic bacteria have been intensively studied, but many aspects of these interactions are still unknown because most of the studies were performed under non-axenic conditions. Therefore, we investigated the growth and release of dis- solved organic matter of the marine diatom Thalassiosira rotula in axenic culture in comparison to T. rotula cultures inoculated with either a natural marine bacterial community (German Wadden Sea) or 3 different bacterial isolates. The isolates affiliated to the Roseobacter group (HP50), Hyphomonas (HP48) and Flexibacteriaceae (HP49) and were previously obtained from a T. rotula culture inoc- ulated with a natural marine bacterial community (German Wadden Sea). To test whether the availability of inorganic nutrients, vitamins and trace metals affects algal growth, organic matter release and interactions with heterotrophic bacteria, we performed experiments with either Guil- lard's f/2 or f/10 medium, which differ in their inorganic nutrient, vitamin and trace metal concentra- tion by a factor of 5. The bacterial community promoted growth of T. rotula in both media, as shown by the higher algal numbers relative to the axenic cultures, but also led to a rapid decline after the growth phase. Isolate HP50 promoted algal growth in the f/2 medium, but inhibited growth in the f/10 medium, whereas isolate HP48 showed the opposite patterns. Isolate HP49 prevented algal growth in both media. T. rotula exhibited distinct release patterns of dissolved organic carbon (DOC), dissolved amino acids, dissolved neutral carbohydrates, transparent exopolymer particles (TEP) and protein-containing particles (Coumassie Blue-stainable particles, CSP), which were modulated by the bacteria added. TEP and CSP were produced by the growing alga only in the presence of bac- teria, indicating that the bacterial modification of algal exudates and/or the bacterial decomposition of the alga are prerequisites for formation of these microparticles. Our results show that the presence of the bacterial community and of specific populations have distinct effects on the growth and organic matter release of T. rotula and presumably also on other algae.

On the determination of mass transfer in a concentration boundary layer

The mass transfer of scalar quantities (e.g., O2 and nutrients) in aquatic environments is an important and complex process involving diffusion and advection. In a flowing environment, concentration boundary layers (CBL) occur above the surfaces of organisms when they are a sink or source of scalars. In this study, we used an O2 microsensor to profile the O2 concentrations in the CBL above photosynthesizing freshwater macrophyte (Vallisneria americana) leaves that were oriented parallel to the flow in a recirculating flow chamber at 0.5 and 3.3 cm s−1. Measured O2 profiles were nonlinear indicating the effect of higher order processes near the surface. O2 flux (Jobs) was estimated from these profiles by two nonlinear techniques, hyperbolic tangent and logarithmic models, and the commonly applied linear model. An integrated measurement of O2 flux (Jint) for each leaf was also measured independently in a stirred chamber. Whereas Jobs determined from the hyperbolic tangent (0.42 ± 0.04 [mean SE] µmol m−2 s−1) and linear (0.31 ± 0.04 µmol m−2 s−1) models overestimated and underestimated Jint (0.37 ± 0.05 µmol m−2 s−1), respectively, and were not velocity dependant, the hyperbolic tangent model provided the best fit (r2 = 0.88) compared with the linear model (r2 = 0.77). In addition, the slope of the regression against Jint (1.08 ± 0.06) was closest to 1.00 (i.e., a “perfect” fit). The logarithmic model varied with velocity and overestimated Jobs (0.98 ± 0.22 µmol m−2 s−1 at 0.005 m s−1 and 0.90 ± 0.18 µmol m−2 s−1 at 0.033 m s−1). These results were confirmed in an analysis of 21 published O2 concentration profiles measured next to sediments, microbial biofilms, planktonic algae, and epilithic algae. We would, therefore, recommend the hyperbolic tangent model to estimate mass transfer in a CBL.

Activity of digestive enzymes of three morpho-ecological forms of Altai osman (Oreoleuciscus potanini) from the Nogon-Nur Lake (the Large Lakes’ Depression, Mongolia)

INTRODUCTIONThe Altai osmans of g. Oreoleuciscus (Cyprinidae)are the most numerous inhabitants of the Central-Asianinternal basin of the Western Mongolia. Earlier, basedupon the analysis of living traits and morphology, sev-eral morpho-ecological forms were distinguishedamong the Mongolian Altai osmans, some of whichwere previously ranked as species (Dgebuadze, 1982;Baasanzhav et al., 1983; Borisovets et al., 1985). Thus,in the lower reaches of the Kobdo River (Ogon-NurLake), three forms of the Potanin’s Altai osman (Oreo-leuciscus potanini) were described. Conventionally,these forms were named as the “phytophagous”,“sharp-nosed,” and “piscivorous” (Baasanzhav et al.,1983). Despite presence of numerous intermediateforms, the adult specimens of the above forms are eas-ily differentiated with consideration of morphologicalfeatures, patterns of distribution in a water body, andfeeding spectra (Baasanzhav et al., 1983; 1985). Thefeeding base of all three forms is composed of thecharophytes. However, in the phytophagous form, ashare of insect larvae and imagos is comparatively high,while other groups of aquatic organisms, including fish,are represented to a lesser extent. In the food of thesharp-nosed form, the planktonic algae and inverte-brates made up a considerable share, while in the pis-civorous form—fish (the osmans, and sometimes theloaches Ortrias sp.). The young osmans feed predomi-nantly on the planktonic organisms while in the stom-ach content of the phytophagous form, the share of thebenthic organisms is quite considerable, making upfrom 16 to 53% of the mass (Baasanzhav et al., 1985).It seems obvious that, during the process of morpho-ecological diversification of the Altai osmans, the selec-tion of particular food items played an important role.Consequently, the question arises if there are any differ-ences in the activities of digestive enzymes that digestfood proteins and carbohydrates in different forms ofosmans and at different stages of their ontogenesis. The presence of specific feeding preferences in thisvery variable group of fish (while the feeding spectraare really wide, from charophytes to fish) suggests thepresence of adaptations in the digestive enzymes' sys-tem to the biochemical composition of food. However,we do not know of any published data concerning theactivities of the digestive enzymes processing the mainplastic and energetic food components in the Altaiosman intestines.The goal of the present paper is to determine theactivities of digestive hydrolases (carbohydrases andproteinases) in the intestinal mucus of the three formsof Altai osmans from the Mongolian Nogon-Nur Lake.MATERIAL AND METHODSThe material was collected during the field studiesof the ichthyological detachment of the Joint Russian-Mongolian combined biological expedition of the Rus-sian Academy of Sciences and the Academy of Sci-ences of Mongolia at the end of August 2004. The fishwere collected in the Lake Nogon-Nur that is a part ofthe lake system Hara-Us-Nur–Hara-Nur–Durgun-Nur,at the River Kobdo downstream (Western Mongolia).Young and mature specimens of the phytophagous(56 ± 3.0 and 116.4 ± 7.0 g in weight), sharp-nosed(17.3 ± 1.3 and 109 ± 11 g) and piscivorous (116 ± 14and 589 ± 30 g) forms of the Potanin’s Altai osman.The fish were caught by nets (10 mm to 55 mm meshsize) from which they were removed every 8 h. Theintestines were removed immediately after the catch,

Planktonic algae of Derbent Dam Lake (Samsun, Turkey)

The phytoplankton of the Derbent Dam Lake was investigated between February 2001 and July 2002. In this study, a total 180 taxa belong to 8 division have been identified. These were Cyanophyta (Cyanobacteria) [22 taxa; 12%], Bacillariophyta [74 taxa; 41%], Chlorophyta [69 taxa; 38%], Chrysophyta [1 taxa; 1%], Cryptophyta [2 taxa; 1%], Euglenophyta [6 taxa; 3%], Pyrrophyta [3 taxa; 2%] and Xanthophyta [3 taxa; 2%]. According to planktonic algae composition, Derbent Dam Lake has a changing characteristic from oligotrophy to mesotrophy.

Transport and degradation of a dinoflagellate bloom in permeable sublittoral sediment

Filtration of planktonic algal cells from the water column into permeable sublittoral sediment and the fate of the cells in the shallow sands were studied during a red tide produced by the dinoflagellate Peridinella catenata at Hel Peninsula/Baltic in May 2004. Advective porewater flows associated with ripple topography of the bed caused rapid transport of algal cells down to 5 cm sediment depth. Sedimentary concentrations of algal cells mirrored algal concentrations in the overlying water column with increases and decreases within the upper 3 cm of the bed occurring within a few hours. Sedimentary algal uptake and release significantly differed between stations only 15 m laterally apart. Laboratory sediment-column experiments with 13C-labeled algal cells revealed algal decomposition at rates of up to 0.2% 13C h–1 in percolated sands originating from the study site. This was 2 orders of magnitude lower than observed decreases in sediment algal cell C abundance of up to 23% C h–1 after a drop in cell concentrations in the water column. Because bioturbation and ripple migration were negligible, we conclude that advective flushing of the uppermost sediment layer could rapidly remove cells from the sediment. Our results demonstrate close spatial and temporal coupling between algal cell concentrations in the boundary layer and those in the upper 6 cm of permeable sand sediment, and suggest that permeable beds can act as short-term storage buffer for phytoplankton. During passage through the sediment, planktonic algae may benefit from the higher nutrient concentrations available in the porewater.