Search results for "Biomass"
showing 10 items of 956 documents
Potential for large-bodied zooplankton and dreissenids to alter the productivity and autotrophic structure of lakes.
2014
While limnological studies have emphasized the importance of grazers on algal biomass and primary production in pelagic habitats, few studies have examined their potential role in altering total ecosystem primary production and it's partitioning between pelagic and benthic habitats. We modified an existing ecosystem production model to include biotic feedbacks associated with two groups of large-bodied grazers of phytoplankton (large-bodied zooplankton and dreissenid mussels) and estimated their effects on total ecosystem production (TEP), and the partitioning of TEP between phytoplankton and periphyton (autotrophic structure) across large gradients in lake size and total phosphorus (TP) co…
Comparative study of phytoplankton in an oligotrophic soft water lake under different pH-phosphate ranges
1998
This work reports phytoplankton changes in a shallow, acidic and oligotrophic lake (Loch Rusky, Scotland) from two different periods: one with artificial phosphate fertilization and neutral pH (SRP 3–18 µg l-1, pH 6.6–7.8, 1972–73) and the other with low phosphate and acidic pH values (SRP <1.5 µg l-1, pH 5.6–6.9, 1985–86). Phosphate enhanced markedly total algal biomass and favoured the presence of cyanophytes, especially in the summer epilimnion, while cryptophytes dominated at this time during unfertilized periods. Anabaena sp. peaked during summer and a higher density of Ceratium hirundinella and Peridinium sp. in mid-summer was also observed during the fertilized period. Otherwise, alg…
Effects of eutrophication and organic loading on the occurrence of profundal harpacticoids in a lake in southern Finland.
1992
Harpacticoids made up 19 and 30% of the meiobenthos proper by number and 39 and 55% by biomass at maximum depths and a depth of 20 m, respectively, in Lake Paijanne. Harpacticoids accounted for higher proportions of the total meiobenthos in oligotrophic and unpolluted areas than in polluted areas. Seven species were identified, with Canthocamptus staphylinus confined to semi-lotic areas influenced by organic pollution from a pulp mill. Other species exhibited somewhat different distributions in oligotrophic and mesotrophic areas. Harpacticoid densities were most closely correlated with oxygen content and phytoplankton biomass, and correlations with environmental values were closer at maximu…
Spatial distribution of phytoplankton in the Gulf of Riga during spring and summer stages
1999
Distribution patterns of chlorophyll a, phytoplankton species and biomass were studied in the Gulf of Riga, one of the most eutrophicated areas of the Baltic Sea. Quasi-synoptic measurements were carried out during four seasonal stages (spring bloom 1995, early-summer stage 1994, cyanobacterial bloom 1994, and late summer stage 1993). For each stage, common factor analysis was used to simplify the highly correlated patterns of nutrients, salinity, temperature and the depth of mixed layer. Obtained latent variables were used to explain spatial distribution of phytoplankton. Generally, the distribution of phytoplankton variables followed closely the patterns of nutrient rich fresh water. Duri…
Plant effects on the soil community: A microcosm experiment
1999
Abstract An experiment was carried out in microcosms for testing the hypothesis that a higher level of primary production should maintain a decomposer community with higher biomass and activity. Microcosms with coniferous forest humus and a diverse microbial and faunal community were divided into three sets: (1) control without plants, (2) with birch seedlings in full illumination, and (3) with birch seedlings, shaded to reduce the net primary production. During 16 weeks of incubation at +16 °C, no treatment effects were found in numbers or biomass of taxonomic or functional groups of soil organisms, nor in the system respiration in darkness. The community structure of the shaded systems di…
Distribution and seasonal dynamics of Cryptomonads in Sicilian water bodies
2003
Several species with a relevant ecological importance belong to Cryptophyta. Nevertheless, species-level identification from microscopic observations is problematic, lacking recent taxonomic keys. In this study we report our observations on distribution and seasonal dynamics of Cryptomonads in 33 Sicilian water bodies, as well as the main taxonomical problems we encountered. Species of the genera Cryptomonas and Plagioselmis are the most common in the examined water bodies. Their biomass seasonal trends usually show a peak in late winter and early spring. In advanced spring, and also in summer, due to the higher grazing pressure, the Cryptomonads biomass reaches its lowest values. Moreover,…
Understorey plant and soil responses to disturbance and increased nitrogen in boreal forests
2009
Question: How do N fertilization and disturbance affect the understorey vegetation, microbial properties and soil nutrient concentration in boreal forests? Location: Kuusamo (66°22′N; 29°18′E) and Oulu (65°02′N; 25°47′E) in northern Finland. Methods: We conducted a fully factorial experiment with three factors: site (two levels), N fertilization (four levels) and disturbance (two levels). We measured treatment effects on understorey biomass, vegetation structure, and plant, soil and microbial N and C concentrations. Results: The understorey biomass was not affected by fertilization either in the control or in the disturbance treatment. Fertilization reduced the biomass of deciduous Vacciniu…
Phytoplankton distribution along trophic gradients within and among reservoirs in Catalonia (Spain)
2008
SUMMARY 1. Longitudinal gradients in the epilimnetic waters of stratified reservoirs provide a useful database to study changing environmental conditions. The spatial distribution, assemblage structure and specific adaptations of phytoplankton assemblages can be analysed along these gradients over short time scales. 2. Four reservoirs with a similar typology, located along an altitudinal gradient in the same eco-region, were sampled along their longitudinal axes. In total, 19 sampling stations provided a trophic spectrum, ranging from oligo-mesotrophy to hypertrophy, which was quantified by calculating the trophic state index of each sampling station in the four reservoirs. 3. Several patte…
Mesocosm experiments on nutrient and fish effects on shallow lake food webs in a Mediterranean climate
2004
Summary 1. Nutrient and fish manipulations in mesocosms were carried out on food-web interactions in a Mediterranean shallow lake in south-east Spain. Nutrients controlled biomass of phytoplankton and periphyton, while zooplankton, regulated by planktivorous fish, influenced the relative percentages of the dominant phytoplankton species. 2. Phytoplankton species diversity decreased with increasing nutrient concentration and planktivorous fish density. Cyanobacteria grew well in both turbid and clear-water states. 3. Planktivorous fish increased concentrations of soluble reactive phosphorus (SRP). Larger zooplankters (mostly Ceriodaphnia and copepods) were significantly reduced when fish wer…
Responses of decomposer community to root-isolation and addition of slash
2001
Abstract We studied the causal relationships between forest harvesting and the soil decomposer community focusing on suppression of energy inputs from trees to the soil through root–mycorrhizal network and increased energy input to the soil in the form of slash left on site. We hypothesised that both of these factors would affect the decomposer community, since the soil food web has been regarded as a system in which the amount of resources controls the numbers of consumers. To study the importance of these factors without changes in microclimate, like in sunshine and shade, taking place in clear-felled areas, the experiment was performed in a mature spruce ( Picea abies (L.) Karst.) forest…