Search results for "plankton"
showing 10 items of 549 documents
Long-term abundance dynamics of coastal zooplankton in the Gulf of Riga
1998
The dynamics of three most abundant mesozooplankton species in the coastal zone of the Gulf of Riga — Bosmina longispina, Synchaeta baltica, Keratella quadrata — is analyzed to detect the regulating environmental factors. The only significant downward trend of species abundance was found for S. baltica in autumn. Statistically significant correlation was estimated only between the summer salinity and the abundance of B. longispina. K. quadrata though showed a negative correlation with summer salinity. The abundance of S. baltica had only nonsignificant correlations with the environmental factors. The abundance of coastal mesozooplankton species is determined by the combination of hydrologic…
Evaluation of plankton communities in small highly humic bog lakes in Latvia
1998
This paper reports the results of a study performed at the Teici State Reserve in Latvia The results indicated that algal communities in brown water lakes were formed by species that were tolerant to a low pH and high humic substance concentration. The composition of the species of phytoplankton and zooplankton was comparatively simple. A significant correlation was found between the number of species of phytoplankton, zooplankton, and the pH value. Similarly there was a clear relationship between the taxonomic composition of phytoplankton, zooplankton, and the trophic state of the lakes. Dyseutrophic lakes were characterized by comparatively higher biodiversity of planktonic communities th…
Bacterial and phytoplankton responses to nutrient amendments in a boreal lake differ according to season and to taxonomic resolution
2011
Nutrient limitation and resource competition in bacterial and phytoplankton communities may appear different when considering different levels of taxonomic resolution. Nutrient amendment experiments conducted in a boreal lake on three occasions during one open water season revealed complex responses in overall bacterioplankton and phytoplankton abundance and biovolume. In general, bacteria were dominant in spring, while phytoplankton was clearly the predominant group in autumn. Seasonal differences in the community composition of bacteria and phytoplankton were mainly related to changes in observed taxa, while the differences across nutrient treatments within an experiment were due to chang…
Method for Reproducible Shipboard Segmented Flow Analysis Ammonium Measurement Using an In-House Reference Material for Quality Control
2021
Ammonium is a fundamental nutrient for phytoplankton growth in seawater and is a key component of the microbial loop. Ammonium measured in parallel with other nutrients is crucial in understanding the small temporal scale changes in oceanographic ecology. Despite the importance of measuring ammonium at sea, owing to its lability, there is no consensus on the best method. The lack of availability of certified reference materials for ammonium in seawater also makes it difficult to assess the accuracy and reproducibility of ammonium measurements. In this study we present a modified segmented flow analysis method using ortho-phthaldialdehyde (OPA) with fluorescence detection to measure ammonium…
Erratum for Piwosz et al., "Light and Primary Production Shape Bacterial Activity and Community Composition of Aerobic Anoxygenic Phototrophic Bacter…
2020
Metabolic coupling between phytoplankton and bacteria determines the fate of dissolved organic carbon in aquatic environments, and yet how changes in the rate of primary production affect the bacterial activity and community composition remains understudied. Here, we experimentally limited the rate of primary production either by lowering light intensity or by adding a photosynthesis inhibitor. The induced decrease had a greater influence on bacterial respiration than on bacterial production and growth rate, especially at an optimal light intensity. This suggests that changes in primary production drive bacterial activity, but the effect on carbon flow may be mitigated by increased bacteria…
Temperature effects explain continental scale distribution of cyanobacterial toxins
2018
Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect…
Littoral contribution to whole-lake primary production in highly humic Lake Mekkojärvi
2013
Suurin osa koko järven perustuotantoa käsittelevistä tutkimusta on tehty oligotrofisissa tai eutrofisissa järvissä ja vähän on tutkittu dystrofisten järvien toimintaa. Tämän tutkimuksen tarkoitus oli selvittää litoraalivyöhykkeen perustuotannon osuutta koko järven perustuotannosta dystrofisessa Mekkojärvessä vuonna 2012. Mekkojärvessä on korkeat liuennen orgaanisen hiilen (DOC) ja humushappojen pitoisuudet ja näiden tuloksena erittäin matala valon tunkeutuvuus, suhteellisen matala ravinnepitoisuus ja suhteellisen korkea keskisyvyyden suhde maksimisyvyyteen. Mallit, jotka perustuvat edellä mainittuihin parametreihin, ennustavat pohjaleville vain 5 % osuutta kokonaisperus…
Increasing temperature and productivity change biomass, trophic pyramids and community‐level omega‐3 fatty acid content in subarctic lake food webs
2021
Climate change in the Arctic is outpacing the global average and land-use is intensifying due to exploitation of previously inaccessible or unprofitable natural resources. A comprehensive understanding of how the joint effects of changing climate and productivity modify lake food web structure, biomass, trophic pyramid shape and abundance of physiologically essential biomolecules (omega-3 fatty acids) in the biotic community is lacking. We conducted a space-for-time study in 20 subarctic lakes spanning a climatic (+3.2 degrees C and precipitation: +30%) and chemical (dissolved organic carbon: +10 mg/L, total phosphorus: +45 mu g/L and total nitrogen: +1,000 mu g/L) gradient to test how temp…
Carbon dynamics in highly heterotrophic subarctic thaw ponds
2015
Abstract. Global warming has accelerated the formation of permafrost thaw ponds in several subarctic and arctic regions. These ponds are net heterotrophic as evidenced by their greenhouse gas (GHG) supersaturation levels (CO2 and CH4), and generally receive large terrestrial carbon inputs from the thawing and eroding permafrost. We measured seasonal and vertical variations in the concentration and type of dissolved organic matter (DOM) in five subarctic thaw (thermokarst) ponds in northern Quebec, and explored how environmental gradients influenced heterotrophic and phototrophic biomass and productivity. Late winter DOM had low aromaticity indicating reduced inputs of terrestrial carbon, wh…
Increasing concentration of polyunsaturated fatty acids in browning boreal lakes is driven by nuisance algaGonyostomum
2020
Elevated concentrations of dissolved organic carbon (DOC) promote browning of lakes, which alters the physicochemical properties of water and ecosystem functioning. However, browning‐induced changes in basal production of polyunsaturated fatty acids from the n‐3 and n‐6 families (n‐3 and n‐6 PUFA) in lakes are not fully understood. The concentrations of PUFA, which are micronutrients required to maintain growth and reproduction of consumers, have been suggested to either rise or decline in seston as a response to lake browning. Elevated DOC concentrations may also promote bacterial biomass and production and thus potentially increase the concentration of bacterial fatty acids (BAFA) in sest…