Search results for "picoplankton"
showing 9 items of 9 documents
Development of picoplankton during natural and enhanced mixing under late-winter ice
2014
We studied the development of autotrophic picophytoplankton and heterotrophic bacterioplankton during the tran- sition from winter ice cover to open water under natural and manipulated mixing conditions in eutrophic Lake Vesijarvi. During the melting of the snow and ice cover, a convection layer developed which eventually met the che- mocline at the interface between the oxic and anoxic water masses. However, in the years with mechanically enhanced mixing, the whole water column remained well oxygenated and the deepening of penetrative convection was facilitated. Stochastic variations in weather, primarily the thickness of the snow cover, likely determined the timing of picophytoplankton gr…
Autotrophic and Heterotrophic Picoplankton in Wetlands: Differences with Lake Patterns
2003
This study describes the occurrence, importance and seasonal patterns of picoplankton in two wetlands (TDNP and La Safor), and compares them to a system of fifteen interconnected lakes (Ruidera). In TDNP we performed a six-year monthly study in three sites of the wetland. Bacterial abundance increased throughout time and the autotrophic picoplankton (APP) range was wide (up to 33 x 10 6 cells/ml). The annual averaged APP contribution to total picoplankton and phytoplankton biovolumes was 0.5-22% and 0.03-6% respectively. There were large differences among sites in terms of APP absolute and relative abundance and seasonal patterns. In La Safor, the APP relative contribution to picoplankton a…
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…
Impact on the water column biogeochemistry of a Mediterranean mussel and fish farm
2002
We investigated and compared the impact of organic loads due to the biodeposition of mussel and fish farms on the water column of a coastal area of the Tyrrhenian Sea (Western Mediterranean). Physico-chemical data (including oxygen, nutrients, DOC and particulate organic matter), microbial variables (picoplankton and picophytoplankton density and biomass) and phytoplankton biomass (as chlorophyll-a) were determined on a monthly basis from March 1997 to February 1998. The results of this study indicate that both fish farm and mussel culture did not alter significantly dissolved inorganic phosphorus and chlorophyll-a values, while inorganic nitrogen concentrations were higher in mussel farm a…
Structure of planktonic microbial communities along a trophic gradient in lakes of Byers Peninsula, South Shetland Islands
2013
AbstractA systematic limnological survey of water bodies of Byers Peninsula (Livingston Island, South Shetland Islands) was carried out during the summer of 2001/02. Abundances of microbial plankton were determined which allowed a delineation of the pelagic food web structure. We also report the nutrient status of these lakes. We demonstrate the occurrence of a trophic gradient that extended from upland lakes (oligotrophic) to the coastal ones (eutrophic). The study shows that a lake's morphology regulates the relative importance of the pelagic and benthic habitats, whereas nutrient loads mainly determine its trophic status. Yet, some of the variability observed could be also a legacy of th…
Size-fractionated δ15N and δ13C isotope ratios elucidate the role of the microbial food web in the pelagial of Lake Tanganyika
2003
Food web structure of the pelagic community in Lake Tanganyika was studied using the stable nitrogen and carbon isotopes 15N and 13C. Size-fractionated seston, zooplankton, shrimps, medusae and fish were sampled in the northern part of Lake Tanganyika. Picoplankton fractions as well as cyanobacteria-dominated nano/microplankton fractions had very low nitrogen isotope signatures typical for nitrogen-fixing organisms. Fractions containing mainly dead organic matter (and associated bacteria) or nano/microalgae (chlorophytes and diatoms) had δ15N 2 to 4‰ higher. The low δ15N signatures of small cyclopoids and shrimps suggest they are feeding on nitrogen-fixing cyanobacteria (picoplankton or lar…
Microbial Food Web Components as Potential Indicators of Urban Hydroecosystems / Mikrobiālās ķēdēs Komponentu Potenciāls Pielietojums Urbānās Vides Ū…
2015
Abstract Assessment of the effect of urbanisation on biodiversity and ecological impact studies are focused on plants, birds, terrestrial arthropods, and relatively few studies have been on aquatic organisms. The aim of this study was to investigate the microbial food web components as potential indicators of the trophic state of two small natural lakes (Gaiļezers, Bābelītis), two artificial lakes or reservoirs (created after excavation activities before 20 years) and the Gulf of Riga seaside Vecāķi beach (littoral), all of which are located in the city of Riga or close to it. Analysis of samples was conducted from April til October 2014 by epifluorescense microscopy for pico and nanoplankt…
Zooplankton dynamics during autumn circulation in a small, wind-sheltered, Mediterranean lake
2006
12 pages, and tables statistics.
Plankton Ecology and Diversity
2010
In this chapter we describe plankton responses induced by fluctuating hydrology and eutrophication process in the semi-arid TDNP wetland. We have followed the planktonic community since 1992, at seasonal and interannual scales, covering as well the spatial heterogeneity of the wetland. The studied planktonic components were bacterioplankton, autotrophic picoplankton, nano and microphytoplankton and zooplankton, including ciliates. Plankton has been studied in terms of species composition (diversity), functional groups, spatial heterogeneity, population dynamics. The present data from this wetland allow us to determine which factors (resources and conditions) are relevant for each group and …