Papers by Elena Gorokhova
Field data, stable isotope analyses of the Baltic Sea food web structure,and experimental studies... more Field data, stable isotope analyses of the Baltic Sea food web structure,and experimental studies of the functional response indicate that theomnivorous crustacean Mysis mixta (Crustacea, Mysidacea ...
Photochemistry and Photobiology, Jul 2, 2015
Advanced oxidation processes/technologies (AOT) that combine a semiconductor, such as titanium di... more Advanced oxidation processes/technologies (AOT) that combine a semiconductor, such as titanium dioxide (TiO 2), with a UV source have been used to eliminate microorganisms in various water treatment applications. To facilitate the applicability of this technique, the gain in efficiency from the semiconductor compared to the UV source alone with respect to different target organisms requires evaluation. The primary objective of this study was to determine the effects of TiO 2 and UV wavelength on a freshwater alga, Pseudokirchneriella subcapitata, and a marine alga, Tetraselmis suecica. For each species, dose-response experiments were conducted to determine the median lethal dose (LC 50) of the following treatments: UV-light emitted with a peak of 254 nm, UV-light emitted with a peak of 254 nm in the presence of TiO 2 , and UV-light emitted with a peak of 254 nm and 185 nm in the presence of TiO 2. In both species, the presence of TiO 2 significantly increased mortality. Across all three treatments, P. subcapitata was more sensitive than T. suecica; moreover, the addition of the 185 nm wavelength significantly increased cell mortality in P. subcapitata but not in T. suecica.
Aquatic Invasions, Dec 1, 2007
Marine Ecology Progress Series, Jun 30, 2008
We studied the potential of an introduced species, the predatory cladoceran Cercopagis pengoi, to... more We studied the potential of an introduced species, the predatory cladoceran Cercopagis pengoi, to influence native zooplankton populations in the Baltic Sea. Feeding rates (FRs) of different instars of C. pengoi on Eurytemora affinis, a dominant copepod species, were determined experimentally. The FRs of C. pengoi varied from 0.7 to 4.8 prey predator-1 d-1 and were significantly higher in older instars. Based on the experimental results and long-term zooplankton abundance data from the Gulf of Finland, we estimated the in situ predation rates. Our results imply that at maximum abundance, the C. pengoi population feeding in dense prey patches could consume as many as 10 5 E. affinis m-3 d-1. This could explain the observed drastic decrease in copepod abundances in the eastern Gulf of Finland, the region with the highest C. pengoi abundance after the expansion of this species. Such a decline may strengthen food competition between other zooplanktivores, i.e. planktivorous fish and mysids, feeding on the same copepod prey in regions where C. pengoi may reach high abundances. In the Gulf of Finland, especially in the eastern parts, a collapse of E. affinis, a key species in the pelagic system, would cause major changes in virtually all trophic levels, because the food web structure is simple with only a few species of zooplankton, planktivores, and piscivores.
Marine Pollution Bulletin, Oct 1, 2015
Microplastics (MPs) are a newly recognized type of environmental pollution in aquatic systems; ho... more Microplastics (MPs) are a newly recognized type of environmental pollution in aquatic systems; however no monitoring of these contaminants is conducted, mostly due to the lack of routine quantification. In the net samples collected with a 90-μm WP2 net, pelagic MP abundance was quantified by light microscopy and evaluated as a function of inshore-offshore gradient, depth, and season; the same samples were used for zooplankton analysis. The MP abundance was ∼10(2)-10(4)particlesm(-3), with no significant inshore-offshore gradient during summer but increasing offshore in winter. MP abundance in deeper layers was positively affected by zooplankton abundance in the upper layers and significantly lower during winter compared to summer. These findings indicate heterogeneity of MP distribution due to biotic and abiotic factors and suggest that samples collected for other purposes can be used for quantification of MPs in the Baltic Sea, thus facilitating integration of MP assessment into existing monitoring schemes.
Frontiers in Physiology, Jan 4, 2022
The association between oxidative processes and physiological responses has received much attenti... more The association between oxidative processes and physiological responses has received much attention in ecotoxicity assessment. In the Baltic Sea, bloom-forming cyanobacterium Nodularia spumigena is a significant producer of various bioactive compounds, and both positive and adverse effects on grazers feeding in cyanobacteria blooms are reported. To elucidate the effect mechanisms and species sensitivity to the cyanobacteria-dominating diet, we exposed two Baltic copepods, Acartia bifilosa and Eurytemora affinis, to a diet consisting of toxin-producing cyanobacteria N. spumigena and a high-quality food Rhodomonas salina at 0-300 μg C L −1 ; the control food was R. salina provided as a monodiet at the same food levels. The subcellular responses to food type and availability were assayed using a suite of biomarkers-antioxidant enzymes [superoxide dismutases (SOD), catalase (CAT), and glutathione S-transferases (GST)] and acetylcholinesterase (AChE). In parallel, we measured feeding activity using gut content (GC) assayed by realtime PCR analysis that quantified amounts of the prey DNA in copepod stomachs. As growth and reproduction endpoints, individual RNA content (a proxy for protein synthesis capacity), egg production rate (EPR), and egg viability (EV%) were used. In both toxic and nontoxic foods, copepod GC, RNA content, and EPR increased with food availability. Antioxidant enzyme activities increased with food availability regardless of the diet type. Moreover, CAT (both copepods), SOD, and GST (A. bifilosa) were upregulated in the copepods receiving cyanobacteria; the response was detectable when adjusted for the feeding and/or growth responses. By contrast, the diet effects were not significant when food concentration was used as a co-variable. A bimodal response in AChE was observed in A. bifilosa feeding on cyanobacteria, with up to 52% increase at the lower levels (5-25 μg C L −1) and 32% inhibition at the highest food concentrations. These findings contribute to the refinement of biomarker use for assessing environmental stress and mechanistic understanding of cyanobacteria effects in grazers. They also suggest that antioxidant and AChE responses to feeding activity and diet should be accounted for when using biomarker profiles in field-collected animals in the Baltic Sea and, perhaps other systems, where toxic cyanobacteria are common.
Fundamental and Applied Limnology, Dec 18, 2007
Journal of Plankton Research, Nov 10, 2009
Frontiers in Environmental Science, Aug 21, 2020
Scientific Reports, Mar 10, 2017
Limnology and Oceanography, Mar 1, 2007
We use molecular markers, feeding experiments, and stable isotopes to understand trophic interact... more We use molecular markers, feeding experiments, and stable isotopes to understand trophic interactions between native mysids, Mysis mixta and Mysis relicta, and a recent invader to the Baltic Sea, the cladoceran Cercopagis pengoi. In feeding experiments, both mysid species ingested C. pengoi at a maximum of 16 prey mysid 21 d 21 and a specific consumption rate of 0.15 d 21 , similar to rates reported for predation on other prey species. The frequency of predation on C. pengoi assayed by molecular diet analysis of field-collected mysids varied between 5% and 43% depending on mysid size and species. Surprisingly, it was consistently higher in juveniles than in adults and in M. mixta than in M. relicta. The results of stable isotope analysis corroborate those of feeding experiments and molecular analysis and indicate a higher contribution of C. pengoi to the nutrition of juveniles and M. mixta. These ontogenetic and interspecific differences in mysid predation on C. pengoi are likely to reflect differences related to their different migratory behavior. Thus, despite its low relative abundance, C. pengoi is readily consumed by mysids; this may impact lower food web interactions and the nutrition of mysids in the invaded ecosystems.
It has recently been hypothesized that variation in the intergenic spacer (IGS) of rDNA has consi... more It has recently been hypothesized that variation in the intergenic spacer (IGS) of rDNA has considerable developmental, evolutionary and ecological signi cance through effects on growth rate and body C : N : P stoichiometry resulting from the role of the IGS in production of rRNA. To test these ideas, we assessed changes in size and structure of the repetitive region of the IGS, juvenile growth rate (JGR), RNA and phosphorus (P) contents in clonal lineages of Daphnia pulex derived from a single female and subjected to divergent selection on weight-speci c fecundity (WSF). As a result of selection, WSF diverged rapidly, with signi cant reductions within two generations. Other signi cant changes accompanying shifts in WSF were that juveniles produced by low-WSF females grew more rapidly and had higher RNA and P contents. An increased predominance of long IGS variants was observed in lineages with elevated JGRs and low WSF. The observed variations in IGS length were related to the number of subrepeat units carrying a promoter sequence in the repetitive region. These results strongly support the hypothesized relationships, indicate a genetic mechanism for the evolution of such associations and demonstrate that Daphnia (and perhaps other parthenogens) possess considerable potential for rapid adaptive change in major lifehistory traits.
Human-mediated introductions of non-indigenous species now threaten to homogenize the biota of th... more Human-mediated introductions of non-indigenous species now threaten to homogenize the biota of the Globe, causing huge economic and ecological damage. This thesis studies the ecological role of 3 invasive planktonic crustaceans, the omnivorous copepod Acartia tonsa (western Atlantic and Indo-Pacific) and the predatory cladocerans, Cercopagis pengoi (Ponto-Caspian) and Bythotrephes longimanus (Eurasian). B. longimanus invaded the North American Great Lakes in 1982, C. pengoi the Baltic in 1992 and the Great Lakes in 1999, while A. tonsa has an extensive invasion history that includes the Baltic.We review current knowledge on feeding biology of the predatory cladocerans. A study of stable C and N isotope ratios indicated mesozooplankton as the main food source of C. pengoi in the northern Baltic Sea proper, with young C. pengoi also eating microzooplankton, such as rotifers. Young-of-the-year herring did eat C. pengoi and herring trophic position shifted from 2.6 before the invasion to 3.4 after, indicating that C. pengoi had been “sandwiched” into the modified food web between mesozooplankton and fish.Salinity tolerance experiments on Acartia tonsa and co-occurring Acartia clausi showed the formers euryhaline character and high grazing potential. Energy partitioning between ingestion, production and respiration was rather constant over the tested salinity range of 2 to 33, with small differences in gross growth efficiency and cost of growth, but maximum ingestion at 10-20. Egg hatching in A. tonsa was only reduced at the lowest salinity. Extreme changes in salinity were needed to cause significant mortality of A. tonsa in the field, but its feeding activity could be severely reduced by salinity changes likely to occur in estuaries. A study of a hypertrophic estuary showed that A. tonsa can sustain a population despite very high mortality rates, caused by predation, high pH and low oxygen, helping explain the success of A. tonsa as an invader of estuaries.
Royal Society Open Science, Mar 1, 2017
In ecology, stable isotope labelling is commonly used for tracing material transfer in trophic in... more In ecology, stable isotope labelling is commonly used for tracing material transfer in trophic interactions, nutrient budgets and biogeochemical processes. The main assumption in this approach is that the enrichment with a heavy isotope has no effect on the organism growth and metabolism. This assumption is, however, challenged by theoretical considerations and experimental studies on kinetic isotope effects in vivo. Here, I demonstrate profound changes in life histories of the rotifer Brachionus plicatilis fed 15 N-enriched algae (0.4-5.0 at%); i.e. at the enrichment levels commonly used in ecological studies. These findings support theoretically predicted effects of heavy isotope enrichment on growth, metabolism and ageing in biological systems and underline the importance of accounting for such effects when using stable isotope labelling in experimental studies.
Social Science Research Network, 2022
Vi utvecklade indikator för djurplankton baserat på biomassan och medelstorlek (MSTS) för att utv... more Vi utvecklade indikator för djurplankton baserat på biomassan och medelstorlek (MSTS) för att utvärdera statusen hos pelagiska näringsvävar. Därmed bedömer man miljöstatus med hjälp av dels djurplanktons medelstorlek, och dels för den totala biomassan av djurplankton. Indikatorn är en del av deskriptorerna för näringsvävar (D4) och biodiversitet (D1) i MSFD. För utvärdering av GES använde vi data på djurplankton, som samlats in av svenska nationella miljöövervakningsprogrammet för fria vattenmassan och dess finska och tyska motsvarigheter över en 30 årsperiod. Resultatet av projektet är en D4-indikator baserad på djurplankton, med rekommendationer för statistisk analys och GES för svenska vatten i Östersjön. Avgränsningarna för god miljö (GES) skickades till projektet HOLAS II (HELCOM) och användes för att bedöma miljöstatus i Östersjön mellan 2011 och 2015. • Djurplankton betar av växtplankton och utgör föda för predatorer, så som fisk. De utgör därför en livsviktig roll i marina näringsvävar då de transporterar energi till högre trofinivåer och därmed ökar produktiviteten i ekosystemet. Dessutom hjälper de till att omsätta näringsämnen och kol. Därför är det nödvändigt att utvärdera djurplanktonsamhällen för att analysera pelagiska näringsvävar. • Djurplanktons medelstorlek ger en indikation på hur det står till med födotillgång för fisk och betestryck som djurplankton utövar på växtplankton. Storvuxna individer av djurplankton i stora antal ger större möjlighet till effektiv energitransport från växtplankton till fisk. Om djurplanktonsamhället istället domineras av småväxta individer så sker oftast ett större svinn av energi. Med detta i åtanke är det alltså önskvärt med rika djurplanktonsamhällen med storvuxna individer då detta ger en effektivare näringsväv. Därmed är djurplanktonsamhällen som inte består av många storvuxna individer suboptimala och begränsande när det gäller produktivitet och energitransport i näringsväv. • Indikatorn Djurplanktons storlek och mängd (Mean size and total stock; MSTS) använder dels djurplanktons medelstorlek och dels deras totala biomassa för att utvärdera strukturen av pelagiska näringsvävar med fokus på lägre trofinivåer för att utvärdera huruvida god miljöstatus (GES) uppnås. I regel sker detta då individerna är storvuxna och många till antalet. Ett område anses ha god miljöstatus när både medelstorlek och total biomassa hos djurplankton uppnår specifika tröskelvärden. Värdena för god miljöstatus varierar mellan de olika bassängerna i Östersjön. • MSTS är gemensam för alla bassänger inom HELCOM. Indikatorn utvärderas med hjälp av HELCOMs bedömningsskala 2. Framöver bör diskuteras huruvida exempelvis kustområden och havsområden börbedömas olika. Tillförlitligheten hos indikatorn är hög då dataserierna som använts i analysen är långa. • Bedömning av status med hjälp av indikatorn är redo för Norra Östersjön, Bottniska havet, Bottniska viken och Ålands hav. För resten av Östersjöns bassänger pågår arbetet med att fastställa de för utvärderings skull nödvändiga tröskelvärdena. I svenska vatten, saknar vi en fastslagen bedömning för djurplankton i Kvarken, Västra Gotlandshavet, Östra Gotlandshavet, Södra Östersjön, Arkona, Öresund och Kattegat i dagsläget. • God status under perioden 2011-2015 uppnåddes i Bottniska viken och Bottniska havet. I norra Östersjön och i Ålands hav har dock medelstorlek och total biomassa av djurplankton dalat de senaste decennierna, så god miljöstatus uppnåddes ej för perioden 2011-2015. Denna negativa trend är ett resultat av dels fler småvuxna djurplanktonarter (på grund av övergödning) och dels en minskning av hoppkräftor (på grund av högre tryck från predatorer). Det är också möjligt att andra faktorer, som exempelvis minskande salthalt och högre temperatur, skulle kunna ha spelat en roll. Den negativa trenden i flertalet av Östersjöns bassänger indikerar att de pelagiska näringsvävarna är suboptimala apropå energitransport från växtplankton till fisk.We developed ecological indicator that employs zooplankton mean size and total stock (MSTS) to evaluate pelagic food web structure, with particular focus on lower webs. MSTS evaluates good environmental status (GES) using two boundaries, one for mean size and one for total standing stock (biomass) of zooplankton. The indicator contributes to the descriptors D4 (food webs) and D1 (biodiversity) of the MSFD. For GES evaluation, we used zooplankton data collected by the Swedish National Marine Monitoring in combination with Finnish and German Monitoring data; most data series are over 30 years long, and consistent sampling and analysis methodologies have been employed during this time. The outcome of the project is ready-to-use zooplankton indicator, with recommendations on the statistical evaluation and GES values for Swedish waters (Gulf of Bothnia, Baltic Proper and Bornholm basin). The GES boundaries were submitted to HOLAS II project and adopted for Baltic Sea assessment period 2011-2015.…
bioRxiv (Cold Spring Harbor Laboratory), Dec 10, 2019
In the Baltic Sea, the dinoflagellates Apocalathium malmogiense, Biecheleria baltica, and Gymnodi... more In the Baltic Sea, the dinoflagellates Apocalathium malmogiense, Biecheleria baltica, and Gymnodinium corollarium are important contributors to the spring bloom. However, their relative contribution to the bloom community cannot be unambiguously determined by conventional light microscopy due to lack of resolution of distinctive morphological features of the three species. Here, we describe a molecular approach based on a quantitative real-time polymerase chain reaction (qPCR) primer and probe system, targeting the ITS1 and ITS2 regions of the rRNA gene for all three species and enabling their quantification. The specificity of the method was demonstrated using monocultures of A. malmogiense, B. baltica, G. corollarium as well as three other dinoflagellate species co-occurring in the Baltic Sea during spring and validated using fieldcollected phytoplankton samples. .
Limnology and Oceanography-methods, Aug 1, 2010
A simplified method for viability analysis of zooplankton eggs by staining of nonviable eggs with... more A simplified method for viability analysis of zooplankton eggs by staining of nonviable eggs with a fluorescent nucleic acid stain TO-PRO-1 iodide is proposed here as a further development of fluorescence-based egg viability assays. This is one-step analysis with no intermediate steps for chorion removal. The method was calibrated using predetermined mixtures of viable and nonviable eggs (rotifers and copepods), and validated using hatching experiments (copepods) and egg development assay (cladocerans) as reference measurements. In these tests, eggs of several zooplankton species, Brachionus plicatilis (Rotatoria), Daphnia magna (Cladocera), Nitocra spinipes (Harpacticoida), Acartia tonsa (Calanoida), were used. Moreover, staining efficiency was not affected by storage of samples for up to 1 month in-80°C, making the assay suitable for egg viability assessment in field and laboratory studies. To illustrate usefulness of the method, it was applied to evaluate how absence of re-mating affects production of viable eggs in females of A. bifilosa (Calanoida). In females separated from males, proportion of sterile eggs increased in 3 d after the separation and no viable eggs were produced after 5 d. The effects of mating frequency on egg viability are important to understand when designing egg production experiments and interpreting field data on egg viability in populations with skewed sex ratios.
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Papers by Elena Gorokhova