Iveta Jurgensone

Latvian Institute of Aquatic Ecology | LHEI · Department of Marine Monitoring

In eutrophied marine systems such as the Baltic Sea, diazotrophic cyanobacteria have the potential to add additional bioavailable nitrogen (N) to the system through fixation of atmospheric dinitrogen (N2). However, their growth is regarded to be limited by phosphorus availability (P). This study investigates the response of two cyanobacteria specie...

In eutrophied marine systems such as the Baltic Sea, the diazotrophic cyanobacteria has a capacity to further enhance eutrophication or negate mitigation measures by converting atmospheric nitrogen into bioavailable forms through N 2 -fixation. This study investigates the response of two cyanobacteria species, Aphanizomenon flosaquae and Nodularia...

This is a technical guide for monitoring the taxonomic diversity of phytoplankton using environmental DNA metabarcoding, together with conventional phytoplankton monitoring techniques in marine and brackish waters. The guidelines focus on the detection of eukaryotic and prokaryotic phytoplankton with 18S and 16S rRNA primers, using high-throughput...

Temporal variations in the primary production of the size-fractionated autotrophic plankton community were studied in coastal-estuarine waters of the eutrophic Gulf of Riga, Baltic Sea. The community was net-autotrophic during spring and summer and net-heterotrophic during autumn. The results of the present study clearly demonstrate strong covariat...

The semi-enclosed Baltic Sea experiences regular summer blooms of diazotrophic cyanobacteria. Previously it has been conclusively demonstrated that in open nitrogen-limited parts of the Baltic Sea, cyanobacteria successfully fix atmospheric N2. At the same time, diazotrophic activity is still poorly understood in Baltic Sea sub-regions where nitrog...

A method for automatically counting and measuring sizes and motility behavior of zooplankton and phytoplankton in water samples is presented. Two video cameras are focused on separate optical chambers of different sizes. The chambers are filled and emptied repeatedly by synchronized pumps. Real‐time motion analysis is performed by computer on the r...

The ratio of stable carbon and nitrogen isotopes in the suspended particulate matter has been widely used to study processes occurring in the marine ecosystem. At the same time, the signals provided by isotope ratios in coastal ecosystems can be difficult to interpret, due to several, often contradictory processes taking place simultaneously. In th...

Recommendations to frame problems and solutions for the pelagic habitats’ assessment

Zooplankton as an essential component in the pelagic food web are directly linked to pelagic ecosystem functioning. Therefore, comprehension of zooplankton functional diversity (FD) and its responses to environmental changes is crucial for ecosystem-based view. To identify FD responses to environmental drivers, we analysed 25 years of summer data o...

Studying how food web structure and function vary through time represents an opportunity to better comprehend and anticipate ecosystem changes. Yet, temporal studies of highly resolved food web structure are scarce. With few exceptions, most temporal food web studies are either too simplified, preventing a detailed assessment of structural properti...

Large‐scale alterations in marine ecosystems as a response to environmental and anthropogenic pressures have been documented worldwide. Yet, these are primarily investigated by assessing abundance fluctuations of a few dominant species, which inadequately reflect ecosystem‐wide changes. In addition, it is increasingly recognized that it is not spec...

The seasonal patterns of primary production, phytoplankton biomass, chlorophyll a, and nutrients were investigated in the central part of the Gulf of Riga (Baltic Sea) during 2011 and 2012. Annual primary productivity in the gulf was in the range of 353.4–376.2 gC m⁻². Maximum carbon fixation rates occurred during the phytoplankton spring bloom fro...

...Baltijas jūras reģionā kopš 1871. gada ir novērojams nozīmīgs gaisa temperatūras pieaugums. Tomēr tas šajā periodā nav bijis vienmērīgs. Kopumā var izšķirt trīs periodus: temperatūras pieaugums līdz 20. gadsimta trīsdesmitajiem gadiem, temperatūras samazināšanās līdz seš­desmitajiem gadiem, kam atkal sekoja posms, kurā bija vērojams temperatūras...

Assessments of the environmental status of the Baltic Sea as called for by the Marine Strategy Framework Directive (MSFD) must be based on a set of indicators. A pre-core indicator is the diatom/dinoflagellate index (Dia/Dino index), which reflects the dominance of diatoms or dinoflagellates during the phytoplankton spring bloom. Here we explain th...

Three dams affect the flow of the lower Daugava River. The water reservoirs created by damming are relatively small with residence times from three to nine days. However, the water flow alteration is sufficient to cause a decrease in the phytoplankton biomass from an average of 246 to 96 mg m–3. The diatom community was dominated by single-cell and...

The ability of Cd and other trace metals to be incorporated in living phytoplankton cells has been widely used to explain its dynamic in marine ecosystem. However, the discrepancy between results from water column studies and those from studies in sediments remain unexplained. This strongly suggests a need for study with a more interconnected appro...

A common and established view is that increased inputs of nutrients to the sea, for example via river flooding, will cause eutrophication and phytoplankton blooms in coastal areas. We here show that this concept may be questioned in certain scenarios. Climate change has been predicted to cause increased inflow of freshwater to coastal areas in nort...

Changes in biomass of major phytoplankton >5 µm with time: a) week 1, b) week 3 and c) week 5. (TIF)

Changes in bacterial (a and b), phytoplankton (c and d) and zooplankton (e and f) biomass over time during the mesocosms experiments. Figures a, c and e represent NP treatments and b, d and f represent CNP treatments: 0 (), 5 (▪), 10 (), 15 (⧫), 20 (▪), 25 (×), 30 (⧫) and 35 (). (TIF)

Changes in phytoplankton size class during the experiment. Figures a, b and c represent NP 5, 15 and 30, respectively, and figures d, e and f represent CNP 5, 15 and 30, respectively. Phytoplankton smaller <5 µm (black bars), 5–20 µm (dark grey bars) and >20 µm (pale grey bars). (TIF)

Trends in phytoplankton monitoring data (1976–2008) from the Gulf of Riga were investigated and linked to environmental factors. Annual means of spring phytoplankton biomass correlated to phosphorus input from land and shifts between diatoms and dinoflagellates were attributed to potential Si limitation and time of sampling relative to the spring p...

There is an increasing understanding and requirement to take into account the effects of invasive alien species (IAS) in environmental quality assessments. While IAS are listed amongst the most important factors threatening marine biodiversity, information on their impacts remains unquantified, especially for phytoplankton species. This study attem...

Data collection and thus also possibilities to have direct information on the marine environment situation in the Latvian Baltic Proper which is covering the Eastern Gotland Basin was stopped in 1994. The real alterations of ecosystem were not estimated, as only indirect data were available. Thanks to the start of National research program KALME, t...

During the latest years medium-sized (15–30 lm), single-celled dinoflagellates have been reported to form blooms in the northern Baltic Proper and the Gulf of Finland in winter and spring. Recent studies (Kremp et al., 2003. Proceedings of the 7th International conference of Modern and Fossil Dinoflagellates, September 21–25, Nagasaki, Japan, 66 pp...

Baltic Sea environment proceedings, ISSN 0357-2994 ; 106 Pages: 144 p. The report on biovolumes and size-classes of phytoplankton in the Baltic Sea has been produced by the HELCOM Phytoplankton Expert Group (PEG). Most laboratories involved in the HELCOM Baltic Monitoring Programme (COMBINE) have contributed to the work, us ing regional phytoplankt...