Coastal upwelling regions are among the most productive marine ecosystems but may be threatened by amplified ocean acidification. Increased acidification is hypothesized to reduce iron bioavailability for phytoplankton thereby expanding iron limitation and impacting primary production. Here we show from community to molecular levels that phytoplankton in an upwelling region respond to short-term acidification exposure with iron uptake pathways and strategies that reduce cellular iron demand. A combined physiological and multi-omics approach was applied to trace metal clean incubations that introduced 1200 ppm CO2 for up to four days. Although variable, molecular-level responses indicate a prioritization of iron uptake pathways that are less hindered by acidification and reductions in iron utilization. Growth, nutrient uptake, and community compositions remained largely unaffected suggesting that these mechanisms may confer short-term resistance to acidification; however, we speculate that cellular iron demand is only temporarily satisfied, and longer-term acidification exposure without increased iron inputs may result in increased iron stress.
Marine phytoplankton produce and scavenge Reactive Oxygen Species, to support cellular processes, while limiting damaging reactions. Some prokaryotic picophytoplankton have, however, lost all genes encoding scavenging of hydrogen peroxide. Such losses of metabolic function can only apply to Reactive Oxygen Species which potentially traverse the cell membrane outwards, before provoking damaging intracellular reactions. We hypothesized that cell radius influences which elements of Reactive Oxygen Species metabolism are partially or fully dispensable from a cell. We therefore investigated genomes and transcriptomes from diverse marine eukaryotic phytoplankton, ranging from 0.4 to 44 μm radius, to analyze the genomic allocations encoding enzymes metabolizing Reactive Oxygen Species. Superoxide has high reactivity, short lifetimes and limited membrane permeability. Genes encoding superoxide scavenging are ubiquitous across phytoplankton, but the fractional gene allocation decreased with increasing cell radius, consistent with a nearly fixed set of core genes for scavenging superoxide pools. Hydrogen peroxide has lower reactivity, longer intracellular and extracellular lifetimes and readily crosses cell membranes. Genomic allocations to both hydrogen peroxide production and scavenging decrease with increasing cell radius. Nitric Oxide has low reactivity, long intracellular and extracellular lifetimes and readily crosses cell membranes. Neither Nitric Oxide production nor scavenging genomic allocations changed with increasing cell radius. Many taxa, however, lack the genomic capacity for nitric oxide production or scavenging. The probability of presence of capacity to produce nitric oxide decreases with increasing cell size, and is influenced by flagella and colony formation. In contrast, the probability of presence of capacity to scavenge nitric oxide increases with increasing cell size, and is again influenced by flagella and colony formation.
- MeSH
- fytoplankton genetika metabolismus MeSH
- genomika MeSH
- oxid dusnatý * metabolismus MeSH
- peroxid vodíku metabolismus MeSH
- reaktivní formy kyslíku metabolismus MeSH
- superoxidy * metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- oxid dusnatý * MeSH
- peroxid vodíku MeSH
- reaktivní formy kyslíku MeSH
- superoxidy * MeSH
The concentration of dissolved oxygen in aquatic systems helps to regulate biodiversity1,2, nutrient biogeochemistry3, greenhouse gas emissions4, and the quality of drinking water5. The long-term declines in dissolved oxygen concentrations in coastal and ocean waters have been linked to climate warming and human activity6,7, but little is known about the changes in dissolved oxygen concentrations in lakes. Although the solubility of dissolved oxygen decreases with increasing water temperatures, long-term lake trajectories are difficult to predict. Oxygen losses in warming lakes may be amplified by enhanced decomposition and stronger thermal stratification8,9 or oxygen may increase as a result of enhanced primary production10. Here we analyse a combined total of 45,148 dissolved oxygen and temperature profiles and calculate trends for 393 temperate lakes that span 1941 to 2017. We find that a decline in dissolved oxygen is widespread in surface and deep-water habitats. The decline in surface waters is primarily associated with reduced solubility under warmer water temperatures, although dissolved oxygen in surface waters increased in a subset of highly productive warming lakes, probably owing to increasing production of phytoplankton. By contrast, the decline in deep waters is associated with stronger thermal stratification and loss of water clarity, but not with changes in gas solubility. Our results suggest that climate change and declining water clarity have altered the physical and chemical environment of lakes. Declines in dissolved oxygen in freshwater are 2.75 to 9.3 times greater than observed in the world's oceans6,7 and could threaten essential lake ecosystem services2,3,5,11.
- MeSH
- časové faktory MeSH
- ekosystém MeSH
- fytoplankton metabolismus MeSH
- jezera chemie MeSH
- klimatické změny MeSH
- kyslík analýza chemie metabolismus MeSH
- oceány a moře MeSH
- rozpustnost MeSH
- teplota * MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
- Geografické názvy
- oceány a moře MeSH
- Názvy látek
- kyslík MeSH
Unicellular nitrogen fixer Crocosphaera contributes substantially to nitrogen fixation in oligotrophic subtropical gyres. They fix nitrogen even when significant amounts of ammonium are available. This has been puzzling since fixing nitrogen is energetically inefficient compared with using available ammonium. Here we show that by fixing nitrogen, Crocosphaera can increase their population and expand their niche despite the presence of ammonium. We have developed a simple but mechanistic model of Crocosphaera based on their growth in steady state culture. The model shows that the growth of Crocosphaera can become nitrogen limited despite their capability to fix nitrogen. When they fix nitrogen, the population increases by up to 78% relative to the case without nitrogen fixation. When we simulate a simple ecological situation where Crocosphaera exists with non-nitrogen-fixing phytoplankton, the relative abundance of Crocosphaera increases with nitrogen fixation, while the population of non-nitrogen-fixing phytoplankton decreases since a larger fraction of fixed nitrogen is consumed by Crocosphaera. Our study quantitatively supports the benefit of nitrogen fixation despite the high electron/energy costs, even when an energetically efficient alternative is available. It demonstrates a competitive aspect of Crocosphaera, permitting them to be regionally significant nitrogen fixers.
- MeSH
- amoniové sloučeniny farmakologie MeSH
- biologické modely MeSH
- dusík metabolismus MeSH
- fixace dusíku účinky léků MeSH
- fosfor metabolismus MeSH
- fytoplankton účinky léků metabolismus MeSH
- počítačová simulace MeSH
- sinice účinky léků metabolismus MeSH
- uhlík metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- amoniové sloučeniny MeSH
- dusík MeSH
- fosfor MeSH
- uhlík MeSH
We report the results of simple experiments which support the hypothesis that changes in ocean chemistry beginning in the Mesozoic Era resulted in an increase in the nutritional quality per mole of C and per cell of planktonic algal biomass compared to earlier phytoplankton. We cultured a cyanobacterium, a diatom, a dinoflagellate, and a green alga in media mimicking aspects of the chemistry of Palaeozoic and Mesozoic-Cenozoic oceans. Substantial differences emerged in the quality of algal biomass between the Palaeozoic and Mesozoic-Cenozoic growth regimes; these differences were strongly affected by interspecific interactions (i.e., the co-existence of different species alters responses to the chemistry of the medium). The change was in the direction of a Mesozoic-Cenozoic biomass enriched in protein per mole C, although cells contained less carbon overall. This would lead to a lower C:N ratio. On the assumption that Mesozoic-Cenozoic grazers' assimilation of total C was similar to that of their earlier counterparts, their diet would be stoichiometrically closer to their C:N requirement. This, along with an increase in mean cell size among continental shelf phytoplankton, could have helped to facilitate observed evolutionary changes in the Mesozoic marine fauna. In turn, increased grazing pressure would have operated as a selective force for the radiation of phytoplankton clades better equipped with antigrazing capabilities (sensu lato), as found widely in phytoplankton with biomineralization. Our results emphasize potential links between changing seawater chemistry, increased predation pressure and the rise to ecological dominance of chlorophyll a+c algae in Mesozoic oceans. The experiments also suggest a potential role for ocean chemistry in changes of marine trophic structure from the Palaeozoic to the later Mesozoic Era.
- Klíčová slova
- CO 2, FTIR, Mesozoic, Palaeozoic, biomass quality, interspecific communication, organic composition, phytoplankton evolution,
- MeSH
- biomasa * MeSH
- chlorofyl a metabolismus MeSH
- chlorofyl metabolismus MeSH
- fytoplankton metabolismus MeSH
- oceány a moře MeSH
- spektroskopie infračervená s Fourierovou transformací MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
- Geografické názvy
- oceány a moře MeSH
- Názvy látek
- chlorofyl a MeSH
- chlorofyl MeSH
- chlorophyll c MeSH Prohlížeč
Stagnant water bodies have generally received little attention regarding the presence of endocrine disruptive compounds, although they can integrate diverse pollutants from multiple different sources. Many compounds of anthropogenic as well as natural origin can contribute to the overall estrogenicity of surface waters and some of them can exhibit adverse effects on aquatic biota even in very low concentrations. This study focused on freshwater ponds and reservoirs affected by water blooms and determined the estrogenic activity of water by in vitro bioassay as well as concentrations of several important groups of estrogenic compounds (estrogenic hormones, alkylphenols, and phytoestrogens) by LC-MS/MS analyses. Estrogenic hormones were found at concentrations up to 7.1 ng.L-1, similarly to flavonoids, whose concentrations did not exceed 12.5 ng.L-1. Among alkylphenols, only bisphenol A and 4-tert-octylphenol were detected in levels reaching 100 ng.L-1 at maximum. Estrogenic activity of water samples varied from below the quantification limit to 1.95 ng.L-1. There does not seem to be any general causal link of the massive phytoplankton occurrence with the estrogenicity of water or concentration of phytoestrogens, since they showed no direct relationship with the phytoplankton abundance or composition across sites. The contribution of the analysed compounds to the estrogenic activity was calculated in three scenarios. In minimum scenario, just the compounds above quantification limit (LOQ) were taken into account and for most samples, only minor part (<6%) of the biological activity could be explained. In the mean and maximum scenarios, we included also compounds below LOQ into the calculations at the level of LOQ/2 and LOQ, respectively. In these cases, a considerable part of the estrogenic activity could be attributed to the possible presence of steroid estrogens below LOQ. However, for the samples with estrogenic activity greater than 1 ng.L-1, more than 50% of the estrogenic activity remained unexplained even in the maximum scenario. Probably other compounds or possible interactions between individual substances cause the estrogenic activity in these types of water bodies and in this case, the results of LC-MS/MS analyses cannot sufficiently predict the biological effects. A complex approach including bioassays is needed when assessing the estrogenicity of these types of surface waters.
- Klíčová slova
- Alkylphenols, Estrogenicity, Estrogens, Flavonoids, Surface water,
- MeSH
- chemické látky znečišťující vodu analýza metabolismus MeSH
- chromatografie kapalinová MeSH
- endokrinní disruptory analýza metabolismus MeSH
- estrogeny analýza metabolismus MeSH
- fytoplankton chemie metabolismus MeSH
- sladká voda chemie MeSH
- tandemová hmotnostní spektrometrie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- chemické látky znečišťující vodu MeSH
- endokrinní disruptory MeSH
- estrogeny MeSH
In vast areas of the ocean, the scarcity of iron controls the growth and productivity of phytoplankton. Although most dissolved iron in the marine environment is complexed with organic molecules, picomolar amounts of labile inorganic iron species (labile iron) are maintained within the euphotic zone and serve as an important source of iron for eukaryotic phytoplankton and particularly for diatoms. Genome-enabled studies of labile iron utilization by diatoms have previously revealed novel iron-responsive transcripts, including the ferric iron-concentrating protein ISIP2A, but the mechanism behind the acquisition of picomolar labile iron remains unknown. Here we show that ISIP2A is a phytotransferrin that independently and convergently evolved carbonate ion-coordinated ferric iron binding. Deletion of ISIP2A disrupts high-affinity iron uptake in the diatom Phaeodactylum tricornutum, and uptake is restored by complementation with human transferrin. ISIP2A is internalized by endocytosis, and manipulation of the seawater carbonic acid system reveals a second-order dependence on the concentrations of labile iron and carbonate ions. In P. tricornutum, the synergistic interaction of labile iron and carbonate ions occurs at environmentally relevant concentrations, revealing that carbonate availability co-limits iron uptake. Phytotransferrin sequences have a broad taxonomic distribution and are abundant in marine environmental genomic datasets, suggesting that acidification-driven declines in the concentration of seawater carbonate ions will have a negative effect on this globally important eukaryotic iron acquisition mechanism.
- MeSH
- biologický transport MeSH
- endocytóza MeSH
- fytoplankton klasifikace genetika metabolismus MeSH
- genom genetika MeSH
- koncentrace vodíkových iontů MeSH
- lidé MeSH
- molekulární evoluce MeSH
- mořská voda chemie MeSH
- rozsivky genetika metabolismus MeSH
- transferin metabolismus MeSH
- uhličitany metabolismus MeSH
- vodní organismy klasifikace genetika metabolismus MeSH
- železo metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
- Názvy látek
- transferin MeSH
- uhličitany MeSH
- železo MeSH
Teratogenic effects, which were remarkably similar to those induced by retinoic acids, have been seen in wild frogs indicating possible source of retinoids in the environment. Recent studies indicate that some cyanobacterial species can contain teratogenic retinoic acids (RAs) and their analogues. Retinoids are known to regulate important processes such as differentiation, development, and embryogenesis. The study investigated the effects of exudates (extracellular compounds) of two cyanobacteria species with retinoic-like activity and one algae species on embryonic development of amphibians. The retinoid-like activity determined by in vitro reporter gene assay reached 528ng retinoid equivalents (REQ)/L and 1000ng REQ/L in exudates of Cylindrospermopsis raciborskii and Microcystis aeruginosa, respectively, while algal exudates showed no detectable activity. Total mean of retinoid-like copounds into exudate was 35.6ng ATRA/mil.cells for M.aeruginosa and 6.71ng ATRA/mil.cells for C.raciborskii, respectively. Toxicity tests with amphibian embryos up to 96h of development were carried out according to the standard guide for the Frog Embryo Teratogenesis Assay Xenopus. Lowest observed effect concentrations (LOEC) of malformations (2.5-2.6µg/L REQ) were two times lower than LOEC for ATRA (5µg/L). The exudates of both cyanobacteria were indeed provoking diverse teratogenic effects (e.g. tail, gut and eyes deformation) and interference with growth in frogs embryos, while such effects were not observed for the algae. Xenopus embryos were also exposed to all-trans retinoic acid (ATRA) in concentration range (1-40µg/L) equivalent to the REQs detected in cyanobacterial exudates. ATRA (10µg/L) caused similar teratogenic phenotypes at corresponding REQs as cyanobacterial exudates. The study confirms the ability of some species of cyanobacteria to produce retinoids naturally and excrete them directly into the environment at concentrations which might have adverse influence on the development of amphibians.
- Klíčová slova
- All-trans retinoic acid, Cyanobacterial exudates, Embryonic development, Retinoid-like activity, Retinoids, Xenopus laevis,
- MeSH
- biotest MeSH
- chemické látky znečišťující vodu toxicita MeSH
- embryonální vývoj účinky léků MeSH
- fytoplankton metabolismus MeSH
- Microcystis účinky léků MeSH
- reportérové geny účinky léků MeSH
- sinice metabolismus MeSH
- teratogeny toxicita MeSH
- tretinoin metabolismus toxicita MeSH
- Xenopus laevis embryologie MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- chemické látky znečišťující vodu MeSH
- teratogeny MeSH
- tretinoin MeSH
The aim of this study was to assess the phylogenetic relationships, ecology and ecophysiological characteristics of the dominant planktic algae in ice-covered lakes on James Ross Island (northeastern Antarctic Peninsula). Phylogenetic analyses of 18S rDNA together with analysis of ITS2 rDNA secondary structure and cell morphology revealed that the two strains belong to one species of the genus Monoraphidium (Chlorophyta, Sphaeropleales, Selenastraceae) that should be described as new in future. Immotile green algae are thus apparently capable to become the dominant primary producer in the extreme environment of Antarctic lakes with extensive ice-cover. The strains grew in a wide temperature range, but the growth was inhibited at temperatures above 20 °C, indicating their adaptation to low temperature. Preferences for low irradiances reflected the light conditions in their original habitat. Together with relatively high growth rates (0.4-0.5 day-1) and unprecedently high content of polyunsaturated fatty acids (PUFA, more than 70% of total fatty acids), it makes these isolates interesting candidates for biotechnological applications.
- Klíčová slova
- Antarctica *, Ecology *, Fatty acids *, Ice-covered lakes *, Light *, Monoraphidium *, Phylogeny *, Temperature *,
- MeSH
- biodiverzita * MeSH
- Chlorophyta klasifikace genetika metabolismus MeSH
- fytoplankton klasifikace genetika izolace a purifikace metabolismus MeSH
- fyziologická adaptace MeSH
- jezera MeSH
- ledový příkrov * MeSH
- nenasycené mastné kyseliny metabolismus MeSH
- RNA ribozomální 18S genetika MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Antarktida MeSH
- Názvy látek
- nenasycené mastné kyseliny MeSH
- RNA ribozomální 18S MeSH
The sulfate facilitation hypothesis suggests that changes in ocean sulfate concentration influenced the rise to dominance of phytoplankton species of the red lineage. The mechanistic reasons for this phenomenon are not yet understood. We started to address this question by investigating the differences in S utilization by algae of the green and red lineages and in cyanobacteria cultured in the presence of either 5 mmol · L-1 (approximately equivalent to Paleozoic ocean concentrations) or 30 mmol · L-1 (corresponding to post-Mesozoic/extant concentrations) sulfate. The activities of the main enzymes involved in SO42- assimilation changed in response to changes in growth sulfate concentration. ATP sulfurylase showed different kinetics in the various taxa, with an especially odd behavior for the dinoflagellate. Sulfate availability had a modest effect on cell organic composition. Species-specific differences in the use of some elements were instead obvious in algae grown in the presence of different sulfate concentrations, overall confirming that algae of the red lineage do better at high sulfate than algae of the green lineage. The increase in sulfate concentration may thus have had an impact on phytoplankton radiation both through changes in their enzymatic machinery and through indirect repercussion on elemental usage.
- Klíčová slova
- ATP sulfurylase, algae evolution, cell composition, elemental stoichiometry, sulfate assimilation, sulfur metabolism,
- MeSH
- biologická evoluce * MeSH
- Chlorophyta metabolismus MeSH
- Dinoflagellata metabolismus MeSH
- fytoplankton metabolismus MeSH
- rozsivky metabolismus MeSH
- sinice metabolismus MeSH
- síra metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- síra MeSH
