| 1. |
- Johansson, Karin S L, et al.
(författare)
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Development of a quantitative PCR method to explore the historical occurrence of a nuisance microalga under expansion
- 2016
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Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 56, s. 67-76
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Tidskriftsartikel (refereegranskat)abstract
- A number of marine and freshwater harmful algal bloom (HAB) species have colonized new areas and expanded their habitat range in recent years. Nevertheless it is notoriously difficult to establish when colonization first occurred, what the dispersal routes are, and to separate recent invasion from increases in existent but small populations. The freshwater raphidophyte Gonyostomum semen is a nuisance species that has expanded its habitat range and increased in abundance in northern Europe during the past decades. To evaluate to what extent sediments can be used for determining historic occurrence of G. semen, a quantitative real-time PCR method for detecting cysts of this algae was developed. This paper presents a qPCR protocol with a set of primers that are specific to Gonyostomum and with PCR conditions optimized for sediment samples from humic lakes, which are the common habitat of G. semen. With this sensitive method as few as 1.6 cysts per PCR reaction could be reliably quantified, corresponding to 320 cysts per g wet weight sediment. Cysts were present in sediments with ages ranging from years to decades and their persistence allows detection of historic populations up to at least 50 years old. With this qPCR assay it will be possible to trace the presence of G. semen in environments prior to the onset of algae-specific monitoring programs as well as for quantification in water column samples. © 2016 The Authors.
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| 2. |
- Anderson, D M, et al.
(författare)
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Community assembly and seasonal succession of marine dinoflagellates in a temperate estuary: The importance of life cycle events
- 2006
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Ingår i: Limnology and Oceanography. - 1939-5590. ; 51:2, s. 860-873
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Tidskriftsartikel (refereegranskat)abstract
- Dinoflagellate successional strategies and community structure were investigated in Perch Pond, a temperate estuary on the North American east coast by field surveys as well as laboratory investigations on growth rates, cyst maturation period, and cyst germination temperature thresholds. The dominant species were those predicted by the Smayda and Reynolds Rules of Assembly life form model. Three successional strategies were characterized: (1) holoplanktonic, (2) meroplanktonic (i.e., germinated from cysts), and (3) introduced by advection. The seasonal succession of the meroplanktonic dinoflagellates that were studied reflects the differential lengths of their mandatory dormancy periods as well as differences in their temperature thresholds or "windows" for germination. The holoplanktonic species present at low densities year-round in Perch Pond had a wide temperature tolerance for growth and thus did not need a cyst stage to survive seasonal extremes. Another non-cyst-forming species relied solely on advection to inoculate the salt pond; thus, blooms in successive years would be expected to be more stochastic in nature than for the other two strategies. The timing of cyst formation and population decline for meroplanktonic species corresponded on several occasions to an increase in grazers, suggesting that grazing might have contributed to bloom decline from cyst formation. This timing also suggests the possibility of encystment as a predator avoidance strategy. We suggest that seasonal succession of cyst-forming dinoflagellates is not stochastic. Instead, the appearance of these species in the plankton is predictable on the basis of measurable physiological responses to both endogenous and exogenous factors that they experience during dormancy and quiescence.
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| 3. |
- Andersson, Björn, 1985, et al.
(författare)
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Cross-contamination risks in sediment-based resurrection studies of phytoplankton
- 2022
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Ingår i: Limnology and Oceanography Letters. - : Wiley. - 2378-2242. ; 8:2, s. 376-84
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Tidskriftsartikel (refereegranskat)abstract
- Resurrection studies can answer some fundamental questions in aquatic ecology and evolutionary biology. For phytoplankton resting stages, longevity of thousands to millions of years has recently been reported. However, contamination during sediment sampling could distort these estimates, and this risk has not been systematically evaluated. Here we used 4.5 mu m diameter microspheres to quantify contamination while reviving the resting stages of seven abundant estuarine diatom and cyanobacterial taxa. We observed a sharp decline in resting stages abundance from 10(6) (g wet sediment)(-1) at the surface to < 0.8 (g wet sediment)(-1) at 12.5 cm depth. Added microspheres (similar to 4.5 x 10(7) cm(-2)) were translocated even deeper down the sediment and could well explain the vertical distributions and abundances of revived cells. Without this control, we could have claimed to have revived seven multi-decades to centennial-old taxa. Our findings suggest that improved contamination controls are needed for sediment core sampling of rare cells, microfossils, or DNA molecules.
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| 4. |
- Andersson, Björn, 1985, et al.
(författare)
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Differences in metal tolerance among strains, populations, and species of marine diatoms – Importance of exponential growth for quantification
- 2020
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Ingår i: Aquatic Toxicology. - : Elsevier BV. - 0166-445X .- 1879-1514. ; 226
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Tidskriftsartikel (refereegranskat)abstract
- © 2020 The Author(s) Strains of microalgae vary in traits between species and populations due to adaptation or stochastic processes. Traits of individual strains may also vary depending on the acclimatization state and external forces, such as abiotic stress. In this study we tested how metal tolerance differs among marine diatoms at three organizational levels: species, populations, and strains. At the species level we compared two pelagic Baltic Sea diatoms (Skeletonema marinoi and Thalassiosira baltica). We found that the between-species differences in tolerance (EC50) to the biologically active metals (Cu, Co, Ni, and Zn) was similar to that within-species. In contrast, the two species differed significantly in tolerance towards the non-essential metals, Ag (three-fold higher in T. baltica), Pb and Cd (two and three-fold higher in S. marinoi). At the population level, we found evidence that increased tolerance against Cu and Co (17 and 41 % higher EC50 on average, respectively) had evolved in a S. marinoi population subjected to historical mining activity. On a strain level we demonstrate how the growth phase of cultures (i.e., cellular densities above exponential growth) modulated dose-response relationships to Ag, Cd, Co, Cu, and Zn. Specifically, the EC50's were reduced by 10–60 % in non-exponentially growing S. marinoi (strain RO5AC), depending on metal. For the essential metals these differences were often larger than the average differences between the two species and populations. Consequently, without careful experimental design, interactions between nutrient limitation and metal stress may interfere with detection of small, but evolutionary and ecologically important, differences in tolerance between microalgae. To avoid such artifacts, we outline a semi-continuous cultivation approach that maintains, and empirically tests, that exponential growth is achieved. We argue that such an approach is essential to enable comparison of population or strain differences in tolerance using dose-response tests on cultures of microalgae.
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| 5. |
- Andersson, Björn, 1985, et al.
(författare)
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Intraspecific variation in metal tolerance modulate competition between two marine diatoms
- 2022
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Ingår i: ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 16, s. 511-520
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Tidskriftsartikel (refereegranskat)abstract
- Despite widespread metal pollution of coastal ecosystems, little is known of its effect on marine phytoplankton. We designed a co-cultivation experiment to test if toxic dose–response relationships can be used to predict the competitive outcome of two species under metal stress. Specifically, we took into account intraspecific strain variation and selection. We used 72 h dose–response relationships to model how silver (Ag), cadmium (Cd), and copper (Cu) affect both intraspecific strain selection and competition between taxa in two marine diatoms (Skeletonema marinoi and Thalassiosira baltica). The models were validated against 10-day co-culture experiments, using four strains per species. In the control treatment, we could predict the outcome using strain-specific growth rates, suggesting low levels of competitive interactions between the species. Our models correctly predicted which species would gain a competitive advantage under toxic stress. However, the absolute inhibition levels were confounded by the development of chronic toxic stress, resulting in a higher long-term inhibition by Cd and Cu. We failed to detect species differences in average Cu tolerance, but the model accounting for strain selection accurately predicted a competitive advantage for T. baltica. Our findings demonstrate the importance of incorporating multiple strains when determining traits and when performing microbial competition experiments.
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| 6. |
- Andersson, Björn, et al.
(författare)
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Strain-specific metabarcoding reveals rapid evolution of copper tolerance in populations of the coastal diatom Skeletonema marinoi
- 2023
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X.
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Tidskriftsartikel (refereegranskat)abstract
- Phytoplankton have short generation times, flexible reproduction strategies, large population sizes and high standing genetic diversity, traits that should facilitate rapid evolution under directional selection. We quantified local adaptation of copper tolerance in a population of the diatom Skeletonema marinoi from a mining-exposed inlet in the Baltic Sea and in a non-exposed population 100 km away. We hypothesized that mining pollution has driven evolution of elevated copper tolerance in the impacted population of S. marinoi. Assays of 58 strains originating from sediment resting stages revealed no difference in the average tolerance to copper between the two populations. However, variation within populations was greater at the mining site, with three strains displaying hyper-tolerant phenotypes. In an artificial evolution experiment, we used a novel intraspecific metabarcoding locus to track selection and quantify fitness of all 58 strains during co-cultivation in one control and one toxic copper treatment. As expected, the hyper-tolerant strains enabled rapid evolution of copper tolerance in the mining-exposed population through selection on available strain diversity. Within 42 days, in each experimental replicate a single strain dominated (30%–99% abundance) but different strains dominated the different treatments. The reference population developed tolerance beyond expectations primarily due to slowly developing plastic response in one strain, suggesting that different modes of copper tolerance are present in the two populations. Our findings provide novel empirical evidence that standing genetic diversity of phytoplankton resting stage allows populations to evolve rapidly (20–50 generations) and flexibly on timescales relevant for seasonal bloom progressions.
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| 7. |
- Annenkova, Nataliia, et al.
(författare)
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Recent radiation in a marine and freshwater dinoflagellate species flock.
- 2015
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Ingår i: The Isme Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 9:8, s. 1821-1834
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Tidskriftsartikel (refereegranskat)abstract
- Processes of rapid radiation among unicellular eukaryotes are much less studied than among multicellular organisms. We have investigated a lineage of cold-water microeukaryotes (protists) that appear to have diverged recently. This lineage stands in stark contrast to known examples of phylogenetically closely related protists, in which genetic difference is typically larger than morphological differences. We found that the group not only consists of the marine-brackish dinoflagellate species Scrippsiella hangoei and the freshwater species Peridinium aciculiferum as discovered previously but also of a whole species flock. The additional species include Peridinium euryceps and Peridinium baicalense, which are restricted to a few lakes, in particular to the ancient Lake Baikal, Russia, and freshwater S. hangoei from Lake Baikal. These species are characterized by relatively large conspicuous morphological differences, which have given rise to the different species descriptions. However, our scanning electron microscopic studies indicate that they belong to a single genus according to traditional morphological characterization of dinoflagellates (thecal plate patterns). Moreover, we found that they have identical SSU (small subunit) rDNA fragments and distinct but very small differences in the DNA markers LSU (large subunit) rDNA, ITS2 (internal transcribed spacer 2) and COB (cytochrome b) gene, which are used to delineate dinoflagellates species. As some of the species co-occur, and all four have small but species-specific sequence differences, we suggest that these taxa are not a case of phenotypic plasticity but originated via recent adaptive radiation. We propose that this is the first clear example among free-living microeukaryotes of recent rapid diversification into several species followed by dispersion to environments with different ecological conditions.The ISME Journal advance online publication, 20 January 2015; doi:10.1038/ismej.2014.267.
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| 8. |
- Annenkova, Nataliia V., et al.
(författare)
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Closely related dinoflagellate species in vastly different habitats–an example of a marine–freshwater transition
- 2020
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Ingår i: European Journal of Phycology. - : Informa UK Limited. - 0967-0262 .- 1469-4433. ; 55:4, s. 478-489
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Tidskriftsartikel (refereegranskat)abstract
- Phytoplankton are present in a large variety of aquatic environments, ranging from small freshwater ponds to the oceans. Typically, freshwater and marine species are not closely related, indicating an ancient divergence and that salinity poses a strong dispersal barrier. Here we reveal a common recent origin of two dinoflagellates that are well adapted to different habitats. Gymnodinium baicalense inhabits the geologically old freshwater Lake Baikal, which is located in the middle of the Eurasian continent. Gymnodinium corollarium, on the other hand, is a brackish water species from the Baltic Sea. Both species form blooms under ice during the spring. We generated 10 DNA sequences from these species. The partial 28S rRNA gene from G. baicalense and the partial 18S rRNA gene and internal transcribed spacer-2 (ITS2) from G. corollarium were sequenced for the first time. A more detailed description of G. baicalense, which was previously known only from light microscopy observations, is also provided. In the laboratory we demonstrated that G. baicalense is strictly adapted to fresh water, while G. corollarium had a wide salinity tolerance. However, the two species have almost identical morphology, identical SSU rRNA gene sequences, and only small differences in the LSU rRNA gene and ITS2. We infer a common ancestor, which was a species from the Arctic region with a tolerance to a range of salinities. Our data support the scenario that the under-ice phytoplankton community in Lake Baikal has been formed recently, even though the lake is the oldest in the world.
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| 9. |
- Annenkova, Nataliia V., et al.
(författare)
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Delineating closely related dinoflagellate lineages using phylotranscriptomics
- 2018
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646. ; 54:4, s. 571-576
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Tidskriftsartikel (refereegranskat)abstract
- Recently radiated dinoflagellates Apocalathium aciculiferum (collected in Lake Erken, Sweden), Apocalathium malmogiense (Baltic Sea) and Apocalathium aff. malmogiense (Highway Lake, Antarctica) represent a lineage with an unresolved phylogeny. We determined their phylogenetic relationships using phylotranscriptomics based on 792 amino acid sequences. Our results showed that A. aciculiferum diverged from the other two closely related lineages, consistent with their different morphologies in cell size, relative cell length and presence of spines. We hypothesized that A. aff. malmogiense and A. malmogiense, which inhabit different hemispheres, are evolutionarily more closely related because they diverged from a marine common ancestor, adapting to a wide salinity range, while A. aciculiferum colonized a freshwater habitat, by acquiring adaptations to this environment, in particular, salinity intolerance. We show that phylotranscriptomics can resolve the phylogeny of recently diverged protists. This has broad relevance, given that many phytoplankton species are morphologically very similar, and single genes sometimes lack the information to determine species’ relationships.
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| 10. |
- Björnerås, Caroline, et al.
(författare)
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Inland blue holes of The Bahamas - chemistry and biology in a unique aquatic environment
- 2020
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Ingår i: Fundamental and Applied Limnology. - : Schweizerbart science publishers. - 1863-9135. ; 194:2, s. 95-106
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Tidskriftsartikel (refereegranskat)abstract
- While lake systems in temperate regions have been extensively studied, tropical and subtropical systems have received less attention. Here, we describe the water chemistry and biota of ten inland blue holes on Andros Island, The Bahamas, representative of the morphological, abiotic, and biotic variation among Androsian inland blue holes. The majority of the studied blue holes were vertically stratified with oxic freshwater overlying anoxic saline groundwater of marine origin. Water chemistry (e.g. total phosphorus and nitrogen) in shallow waters was similar among blue holes, while turbidity and water color varied. Presence of hydrogen sulfide and reduced iron in and below the halocline indicate reducing conditions in all stratified blue holes. The biota above the halocline was also similar among blue holes with a few taxa dominating the phytoplankton community, and the zooplankton community consisting of copepods and rotifers. The Bahamas mosquitofish (Gambusia hubbsi) was present in all investigated blue holes, often accompanied by other small planktivorous fish, while the piscivorous bigmouth sleeper (Gobiomorus donnitor) was only present in some of the blue holes. Our field study reinforces that inland blue holes are highly interesting for biogeochemical research, and provide naturally replicated systems for evolutionary studies.
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