Search results for "plankton"

Theme: Morphological plasticity of phytoplankton under different environmental constraints Fourteenth Workshop of the International Association of Ph…

2007

History of bioavailable lead and iron in the Greater North Sea and Iceland during the last millennium – A bivalve sclerochronological reconstruction

2014

We present the first annually resolved record of biologically available Pb and Fe in the Greater North Sea and Iceland during 1040-2004 AD based on shells of the long-lived marine bivalve Arctica islandica. The iron content in pre-industrial shells from the North Sea largely remained below the detection limit. Only since 1830, shell Fe levels rose gradually reflecting the combined effect of increased terrestrial runoff of iron-bearing sediments and eutrophication. Although the lead gasoline peak of the 20th century was well recorded by the shells, bivalves that lived during the medieval heyday of metallurgy showed four-fold higher shell Pb levels than modern specimens. Presumably, pre-indus…

Seasonal zooplankton patterns in a shallow oligotrophic lake: Loch Rusky (Scotland)

1990

The zooplankton taxa and their seasonal distribution are describeb for Loch Rusky, a shallow oligotrophic lake in the central region of Scotland. 15 species were indentified: 11 Rotifera, 2 Cladocera and 2 Copepoda. Only 5 species Polyarthra remata, Keratella cochlearis, Filinia terminalis, Trichocerca sp. and Eudiaptomus gracilis occurred in sufficient numbers to facilitate a description of their seasonal pattern. The annual zooplankton variation was dominated by rotifers for most of the year, but copepods (E. gracilis, Cyclops sp.) only were dominant in the epilimnion during summer. It is presumed that this pattern was the result of the rotifers faster rate of reproduction and higher graz…

Latvijas ūdeņu vides pētījumi un aizsardzība: LU Bioloģijas fakultātes Bioloģijas sekcijas referātu tēžu krājums (Rīga, 2013. gada 18. februāris)

2013

Latvijas Universitātes 71. zinātniskās konferences Bioloģijas sekcijas sēde (Rīga, 2013. gada 18. februāris) veltīta Prof. Heinriha Skujas 120. dzimšanas dienai.

Suitability of Phytosterols Alongside Fatty Acids as Chemotaxonomic Biomarkers for Phytoplankton

2016

The composition and abundance of phytoplankton is an important factor defining ecological status of marine and freshwater ecosystems. Chemotaxonomic markers (e.g., pigments and fatty acids) are needed for monitoring changes in a phytoplankton community and to know the nutritional quality of seston for herbivorous zooplankton. Here we investigated the suitability of sterols along with fatty acids as chemotaxonomic markers using multivariate statistics, by analyzing the sterol and fatty acid composition of 10 different phytoplankton classes including altogether 37 strains isolated from freshwater lakes. We were able to detect a total of 47 fatty acids and 29 sterols in our phytoplankton sampl…

Impairing the largest and most productive forest on our planet: how do human activities impact phytoplankton?

2012

This article summarizes the outcomes of the 16th Workshop of the International Association for Phytoplankton Taxonomy and Ecology. Four major issues dealing with the impact exerted by human activities on phytoplankton were addressed in the articles of this special volume: climate change and its impacts on phytoplankton, the role of land use in shaping composition and diversity of phytoplankton, the importance of autecological studies to fully understand how phytoplankton is impacted by stressors and the role of ecological classification to evaluate community changes due to the different impacts. Case studies from different types of aquatic environments (rivers, deep and shallow lakes, reser…

Potential predation pressure of littoral mysids on herring (Clupea harengus membras L.) eggs and yolk-sac larvae

2008

The predation potential of littoral mysid shrimps (Mysidacea) on Baltic herring (Clupea harengus membras L.) eggs and yolk-sac larvae was studied experimentally. The results showed that littoral mysids feed actively on both eggs and yolk-sac larvae. It was shown that Neomysis integer preys on eggs, which are not attached to the substrate. Alternative food (yolk-sac larvae or zooplankton) did not decrease feeding rate on eggs. Only gravel as a bottom material lowered the ingestion rate to nearly zero. The largest of the mysid species Praunus flexuosus ate yolk-sac larvae more than other mysids and most efficiently. Mysids switched to feed on eggs when larvae and eggs were offered simultaneou…

Light and Primary Production Shape Bacterial Activity and Community Composition of Aerobic Anoxygenic Phototrophic Bacteria in a Microcosm Experiment

2020

ABSTRACT Phytoplankton is a key component of aquatic microbial communities, and metabolic coupling between phytoplankton and bacteria determines the fate of dissolved organic carbon (DOC). Yet, the impact of primary production on bacterial activity and community composition remains largely unknown, as, for example, in the case of aerobic anoxygenic phototrophic (AAP) bacteria that utilize both phytoplankton-derived DOC and light as energy sources. Here, we studied how reduction of primary production in a natural freshwater community affects the bacterial community composition and its activity, focusing primarily on AAP bacteria. The bacterial respiration rate was the lowest when photosynthe…

Influence of Nutrients and Mixing on the Primary Production and Community Respiration in the Gulf of Riga

1999

Abstract Rates of plankton community production and respiration in relation to wind, solar radiation, biomass and nutrients were measured in the mixed layer during a late spring, a mid-summer and an early autumn situation in the Gulf of Riga. System metabolism was estimated by the in vitro oxygen method and from oxygen mass balance directly in the water. Gross production (GPP) remained fairly stable throughout the investigation periods with a mean of 1.8 g C m−2 day−1 (range: 0.5–3.9 g C m−2 day−1). Community respiration varied from 0.5 to 6.4 g C m−2 day−1 during the two summer studies (the high respiration rates ranging from 3.0 to 10.4 g C m−2 day−1 found during the autumn cruise were pr…

Spatio-temporal behaviour of five picophytoplankton populations in Tyrrhe- nian Sea: Model and data

2014

Recent works presented detailed analyses of spatio-temporal dynamics in marine ecosystems, reproducing real vertical distributions of phytoplankton biomass. These study however do not take into account the changes in environmental variables. On the contrary, seasonal variations can influence considerably the primary production, i.e. phytoplankton biomass, in marine ecosystems, determining significative consequences in the whole food chain, in particular fish species, whose growth is mainly explained by seasonal changes in the chlorophyll concentration, a marker of phytoplankton species. Here we present a one-dimensional reaction-diffusion-taxis model to describe the spatio-temporal dynamics…