Grazing resistance in nutrient-stressed phytoplankton

Grazing experiments were performed with the zooplankters Daphnia pulex and Daphnia magna, feeding on phosphorus-saturated and phosphorus-limited cells of two green algae (Scenedesmus subspicatus and Selenastrum capricornutum). P-limited algal cells passed largely intact through the gut and were thus spared from heavy grazing pressure. P-saturated algal cells, in contrast, were efficiently assimilated. Structural and morphological changes in the P-limited cells most probably reduced their digestibility. This phenomenon may be an important factor in zooplankton production and competition, and may serve as an example of a highly efficient strategy of P-limited algae to resist heavy grazing pressure.     

Effects of UV-B radiation on a charophycean alga,Chara aspera

The charophycean algal species Chara aspera was exposed for 73 days to three levels of UV-B radiation (weighted according to Caldwell's generalized plant action spectrum): 1.9 kJ m^–2 day^–1 (`no UV-B'), 6.4 KJ m<sup>–2</sup> day<sup>–1</sup> (ambient) and 10.5 kJ m<sup>–2</sup> day<sup>–1</sup> (enhanced UV-B), the latter level simulating 30% ozone reduction in The Netherlands.Charophycean algae are mainly freshwater organisms and are thought to be the algae most closely related to higher land plants. Therefore we expected that responses of charophycean algae to UV-B radiation might be more related to those observed in the higher land plants than those of other `lower' algal groups.Under elevated UV-B radiation algal length was reduced. There was no induction of UV absorbing compounds under enhanced UV-B. This might relate to a sensitive response to UV-B radiation. The charophycean algae show similar adaptations to UV-B radiation as terrestrial plants, while not having UV-screens as occur in many angiosperms. Vegetative reproduction (bulbils) increased in the presence of UV-B radiation, while generative reproduction (antheridia and oogonia) decreased.     

Soluble polyamines in Salix myrsinifolia and S. myrsinites × S. myrsinifolia plantlets exposed to increased UV-B irradiation and decreased watering

Hybridisation between certain willow species is a common feature leading to novel genotypes varying in growth rate and stress tolerance. The objective of this 4-week study was to investigate the effects of decreased watering, enhanced ultraviolet-B irradiation (UV-B_BE, 280–315 nm, 7.2 kJ m⁻² day⁻¹) and combined decreased watering and enhanced UV-B irradiation on di- and polyamines in the leaves of Salix myrsinifolia and its hybrid with S. myrsinites. Control plantlets were well-watered and exposed to ambient UV-B irradiation (UV-B_BE, 3.6 kJ m⁻² day⁻¹). HPLC analyses showed that the constitutive concentrations of soluble di- and polyamines varied markedly between S. myrsinifolia and its hybrids. The degree of responses to treatments also varied: in S. myrsinifolia, concentrations of free putrescine were clearly increased by reduced watering, while in the hybrid willow, change in putrescine was less pronounced and not significant. Results also showed that the increase in putrescine in S. myrsinifolia by reduced watering was mitigated by concurrent enhancement of UV-B irradiation. There were no direct UV-B effects on the soluble polyamines.     

Effects of UV-B irradiated algae on zooplankton grazing

We tested the effects of UV-B stressed algae on grazing rates of zooplankton. Four algal species (Chlamydomonas reinhardtii, Cryptomonas sp., Scenedesmus obliquus and Microcystis aeruginosa) were used as food and fed to three zooplankton species (Daphnia galeata, Bosmina longirostris and Brachionus calyciflorus), representing different taxonomic groups. The phytoplankton species were cultured under PAR conditions, and under PAR supplemented with UV-B radiation at two intensities (0.3 W m^–2 and 0.7 W m^–2, 6 hours per day). Ingestion and incorporation experiments were performed at two food levels (0.1 and 1.0 mg C l^–1) using radiotracer techniques. The effect of food concentration on ingestion and incorporation rate was significant for all three zooplankton species, but the effect of UV-B radiation was more complex. The reactions of the zooplankton species to UV-B stressed algae were different. UV-B stressed algae did not affect Daphnia grazing rates. For Bosmina the rates increased when feeding on UV-B stressed Microcystis and decreased when feeding on UV-B stressed Chlamydomonas, compared with non-stressed algae. Brachionus grazing rates were increased when feeding on UV-B stressed Cryptomonas and UV-B stressed Scenedesmus, and decreased when feeding on UV-B stressed Microcystis, compared with non-stressed algae. These results suggest that on a short time scale UV-B radiation may result in increased grazing rates of zooplankton, but also in decreased grazing rates. Long term effects of UV-B radiation on phytoplankton and zooplankton communities are therefore difficult to predict.     

The influence of ultraviolet-B radiation on the growth, pigment production and chlorophyll fluorescence of Norway spruce seedlings

Norway spruce (Picea abies (L.)Karst.) from seven seed sources was grown in a greenhouse with 8.3 and 14.7 kJ·m⁻²·d⁻¹ m UV-B_BE (biologically effective UV-B: 280–320 nm) irradiation, and with no supplemental irradiation as control. The seedlings total biomass (dry weight) and shoot growth decreased with high UV-B treatment but spruce from low elevation seed sources were more affected. The seedlings grown at the highest UV-B irradiance (14.7 kJ·m⁻²·d⁻¹) showed from 5 to 38% inhibition of total biomass and 15 to 70 % shoot growth inhibition. Norway spruce populations from higher altitude seed sources manifested greater tolerance to UV-B radiation compared to plants from low altitudes. Changes in phospholipids and protective pigments were also determined. The plants grown at the lower UV-B irradiance (8.3 kJ·m⁻²·d⁻¹) showed greater ability to concentrations UV-B-absorbing pigments then control plants. Chlorophyll a fluorescence parameter R_fd, (R_fd=(F_m-F_s)/F_s) showed a significant decrease in needles of UV-B treated plants and this correlated with the altitude of seed source. Exposure to UV-B affect levels of the ratio of variable to maximum fluorescence (F_v/F_m). Results from this study suggest that the response to increased levels of UV-B radiation is depended upon the ecotypic differentiation of Norway spruce and involved changes in metabolites in plant tissues.     

Nitric oxide plays a role as second messenger in the ultraviolet-B irradiated green alga <Emphasis Type="Italic">Chlorella pyrenoidosa</Emphasis>

Nitric oxide (NO) stimulated the activity of plasma membrane H⁺-ATPase, 5′-nucleotidase, peroxidase, ascorbate peroxidase and glutathione reductase in ultraviolet B (UV-B) irradiated Chlorella pyrenoidosa. It also boosted the activity of nitrogen-metabolism enzymes such as nitrate reductase, nitrite reductase, glutamine synthetase, which were inhibited by UV-B irradiation. The chlorophyll fluorescence ratio (Fv/Fm) of the UV-B irradiated algae and decreased continuously after the cells were transferred to UV-B irradiation. A continuing decrease of the Fv/Fm was observed even after the cells were transferred to photosynthetically active radiation (PAR). After adaptation for 8 h under PAR (after treatment with nitric oxide), Fv/Fm recovered to 55 % of normal levels — without NO the value approached zero. Exogenous NO stopped the decay of chlorophyll and thylakoid membrane in cells exposed to UV-B irradiation. NO plays probably a key role in damage induced by UV-B irradiation in green algae.     

UV-B Radiation Mediated Alterations in the Nitrate Assimilation Pathway of Crop Plants 1. Kinetic Characteristics of Nitrate Reductase

The kinetics and other characteristics of nitrate reductase (NR, EC 1.6.6.1) in cowpea [Vigna unguiculata (L.) Walp.] seedlings irradiated with biologically effective UV-B radiation (280-320 nm, 3.2 W m^-2 s^-1) were recorded. The in vivo and in vitro NR activities were inhibited by 34 and 41 % under UV-B treatment, respectively. Both V_max and K_m for the substrate were enhanced by UV-B radiation. The K_m for nitrate increased from 1.2 to 1.7 mM after the UV-B irradiation. The change in K_m for NADH was from 0.12 to 0.17 mM. The increases in K_m indicate that UV-B radiation seriously changes the topology of NR, particularly with respect to the nitrate and NADH binding sites. The rate of NR turnover indicates the extent of damage inflicted by UV-B radiation on the nitrate metabolism. The half-life (t_1/2) of NR was reduced from 7 to 4 h in the UV-B treated seedlings. UV-B also inhibited the kinetics of nitrate uptake by plants: its K_m increased from 0.08 to 0.12 mM. This revised version was published online in June 2006 with corrections to the Cover Date.     

UV-B Radiation Mediated Alterations in the Nitrate Assimilation Pathway of Crop Plants 2. Kinetic Characteristics of Nitrite Reductase

Cowpea [Vigna unguiculata (L.) Walp. cv. Co 4] seedlings were subjected to a weighted irradiance of 3.2 W m^-2 s^-1 of biologically effective ultraviolet-B radiation (UV-B, 280–320 nm) and the changes in the kinetic and other characteristics of nitrite reductase (NiR) were recorded. The activity of NiR was hampered by 19 % under UV-B irradiation compared to the control. The UV-B treated plants required higher concentrations of nitrate for the induction of NiR synthesis than the controls. The NiR activity decay kinetics showed that the UV-B treatment significantly lowers the t_1/2 of the enzyme, thereby indicating a reduced rate of enzyme turnover. The comparison of kinetic characteristics of nitrate reductase (NR) and NiR under UV-B treatment showed that NiR was not so sensitive to UV-B radiation as NR. As shown by enzyme turnover rates, NiR extracted from plants irradiated by UV-B in situ was less sensitive to UV-B radiation than the enzyme extract subjected to in vitro UV-B irradiation. Though NiR was less damaged by UV-B treatment than NR, subtle changes occurred in its kinetic characteristics. This revised version was published online in June 2006 with corrections to the Cover Date.     

Singlet oxygen-induced alteration of bacteria associated with phytodetritus: Effect of irradiance

Contrasting irradiation of senescent cells of the diatom Thalassiosira sp. in association with the bacterium Pseudomonas stutzeri showed the effect of intensity of irradiance on the transfer of singlet oxygen (¹O₂) to bacteria attached to phytoplanktonic cells. Under low irradiances, ¹O₂ is produced slowly, favors the oxidation of algal unsaturated lipids (photodynamic effect), and limits ¹O₂ transfer to attached bacteria. However, high irradiances induce a rapid and intense production of ¹O₂, which diffuses out of the chloroplasts and easily reaches the attached bacteria, where it efficiently oxidizes their unsaturated membrane components. Analysis of numerous sinking particle samples collected in different regions of the Canadian Arctic showed that the photooxidation state of attached bacteria increased from ice-covered areas to open water, in agreement with in vitro results. Photooxidation of bacteria appeared to be particularly intense in sea ice, where the sympagic algae–bacteria association is maintained at relatively high irradiances for long periods of time.     

Response of Barley Seedlings to UV-B Radiation as Affected by Proline and NaCl

Barley (Hordeum vulgare L. cv. Alfa) seedlings were treated for 4 d before UV-B irradiation with 0.05 mM proline or 150 mM NaCl. UV-B exposure induced synthesis of yellow coloured compounds with maximum absorbance at 438 nm. The content of these compounds was increased in proline-treated and decreased in NaCl-treated plants. UV-B radiation reduced chlorophyll/carotenoids ratio, oxygen evolution rate and photochemical efficiency of PS 2 as estimated by chlorophyll fluorescence and increased proline accumulation, H₂O₂ generation and lipid peroxidation. Exogenous proline had no effect on the parameters studied and did not change the response of plants to UV-B radiation. NaCl inhibited photochemical efficiency of PS 2, reduced oxygen evolution and increased H₂O₂ concentration and lipid peroxidation. The combination of NaCl and proline treatment led to lowering the inhibitory effect of NaCl in non UV-B irradiated seedlings. There was not relationship between the level of UV-B-induced compounds and UV-B tolerance of barley seedlings.     

Effects of the novel allelochemical ethyl 2-methylacetoacetate from the reed (<Emphasis Type="Italic">Phragmitis australis</Emphasis> Trin) on the growth of several common species of green algae

Bioassays were performed to investigate the effects of the novel allelochemical, ethyl 2-methylacetoacetate (EMA), isolated from the reed (Phragmitis australis) on the growth of three common species of algae; Scenedesmus obliquus, Selenastrum capricornutum and Chlamydomonas reinhardtii. The results demonstrated that EMA has three quite different types of effect on these three species of algae. The growth of S. capricornutum was significantly inhibited by EMA during the whole cultivation period. The EC₅₀ values of EMA on S. capricornutum was 0.6 mg L⁻¹(7 days). However, the inhibitory effect of EMA on S. obliquus was apparent during the first 4 days of batch cultivation and then the inhibitory effect disappeared, and a stimulating effect was observed instead. The EC₅₀ value of EMA on S. obliquus was 0.43 mg L⁻¹(4 days). In addition, following the addition of EMA, the cells of S. obliquus and S. capricornutum became significantly larger than the normal untreated one and the algal cells changed morphologically. The microstructure of the algal cells was disrupted by the addition of EMA. There was no significant inhibition of the growth of C. reinhardtii by EMA, but cell motility was affected.     

Effect of UV Irradiance on Utilization of Inorganic Nitrogen by the Antarctic Diatom Odontella weissflogii (Janisch) Grunow

Abstract: The impact of UV-B irradiation on unialgal cultures of the temperate marine diatom Odontella sinensis and of the Antarctic Odontella weissflogii was tested under controlled laboratory conditions. Uptake rates of inorganic nitrogen by Odontella sinensis were more affected by UV-B radiation than those of Odontella weissflogii. Utilization of ¹⁵N-ammonium was reduced after 3 h of UV-B exposure. Values of K_m from several marine phytoplankton species were estimated from algae not exposed to UV-B and from those after 3 h of UV-B radiation. Calculation of Lineweaver-Burk plot showed, under UV-B stress, a noncompetitive inhibition for ¹⁵NH⁺₄ uptake and a competitive inhibitory effect for ¹⁵NO^?₃ by Odontella weissflogii. The damage to ¹⁵NH⁺₄ uptake by UV-B was more pronounced under red than blue light; a contradictory result was obtained for ¹⁵NO^?₃ utilization by Odontella weissflogii. Reduction of the pigments by UV-B under white light was dependent on the exposure time; a strong depression of the contents of chlorophyllide a, chlorophyll c, diatoxanthin and the fucoxanthins was found. Contents of the chlorophylls are markedly affected by UV-B under red light whereas the chlorophyll a concentration is enhanced in blue and green light. UV-B exposure in conjunction with blue and green light led to a reduction of the protein content and an increase in the amino acid contents. The pattern of pool sizes of free amino acids varied after UV-B exposure. UV-A irradiance had no effect. The possible targets of UV-B irradiation on the uptake system of inorganic nitrogen are discussed in detail. Adaptation to the environmental conditions, e.g. via synthesis of UV stress proteins or mycosporine-like amino acids, were also considered.     

Hydrocaffeic and p-coumaric acids,natural phenolic compounds,inhibit UV-B damage in WKD human conjunctival cells in vitro and rabbit eye in vivo

This paper studied the effect on UV-B ocular damage of 10µm hydrocaffeic acid (HCAF) alone and as a mixture (MIX) (5µm HCAF+5µm p-coumaric acid). Since ocular UV-B damage is mediated by reactive oxygen species, the aim was to test if HCAF and MIX could reduce oxidation damage in human conjunctival cells (WKD) in vitro and in cornea and sclera of rabbits in vivo. After UVB irradiation (44 J/m²) of WKD cells, 8-oxodG levels in DNA were markedly increased and this effect was attenuated by HCAF and MIX. Rabbit eyes were treated by application of HCAF and MIX drops before UV-B exposure (79 J/m²). Corneal and scleral DNA oxidation damage, xanthine-oxidase (XO) activity and malondialdehyde levels (MDA) in corneal tissue and prostaglandin E₂ (PGE₂) in the aqueous humour were reduced by HCAF alone and in combination with p-coumaric acid, showing their potential as a topical treatment against UV-B damage.     

The effects of enhanced ultraviolet-B and nitrogen supply on growth,photosynthesis and nutrient status of <Emphasis Type="Italic">Abies faxoniana</Emphasis> seedlings

Abies faxoniana is a key species in reforestation processes in the southeast of the Qinghai-Tibetan Plateau of China. The changes in growth, photosynthesis and nutrient status of A. faxoniana seedlings exposed to enhanced ultraviolet-B (UV-B), nitrogen supply and their combination were investigated. The experimental design included two levels of UV-B treatments (ambient UV-B, 11.02 KJ m⁻² day⁻¹; enhanced UV-B, 14.33 KJ m⁻² day⁻¹) and two nitrogen levels (0; 20 g N m⁻²). The results indicated that: (1) enhanced UV-B significantly caused a marked decline in growth parameters, net photosynthetic rate (Pn), photosynthetic pigments and F _v/F _m, (2) supplemental nitrogen supply increased the accumulation of total biomass, Pn, photosynthetic pigments and F _v/F _m under ambient UV-B, whereas supplemental nitrogen supply reduced Pn, and not affect biomass under enhanced UV-B, (3) enhanced UV-B or nitrogen supply changed the concentration of nutrient elements of various organs.     

Changes in the condition of photosynthetic apparatus of a diatom alga <Emphasis Type="Italic">Thallassiosira weisflogii</Emphasis> during photoadaptation and photodamage

Two populations of a diatom alga Thallassiosira weisflogii were grown at photon flux densities (PFD) of 0.8 and 8 μmol/(m² s). For both diatom populations, the recovery of chlorophyll fluorescence parameters (F ₀, F _m, F _v/F _m, and NPQ) was monitored after nondestructive irradiation by visible light at PFD of 40 μmol/(m² s) and after high-intensity irradiation by visible light (1000–4000 μmol/(m² s)). The exposure of diatoms to PFD of 40 μmol/(m² s)—higher than PFD used for algal growth but still nondamaging to photosynthetic apparatus—induced nonphotochemical quenching (NPQ), which was stronger in algae grown at higher PFD (8 μmol/(m² s)) than in algae grown at low light. After irradiation with high-intensity light, the recovery of chlorophyll fluorescence parameters was more pronounced in algae grown at elevated PFD level. During short-term irradiation of diatoms with high-intensity visible light (1000 μmol/(m² s)), a stronger NPQ was observed in the culture adapted to high irradiance. After the treatment of algae with dithiothreitol (an inhibitor of carotenoid deepoxidase in the diadinoxanthin cycle) or NH₄Cl (an agent abolishing the proton gradient at thylakoid membranes), a short exposure of algae to PFD of 40 μmol/(m² s) induced hardly any nonphotochemical quenching. The results indicate the dominant contribution of xanthophyll cycle carotenoids to energy-dependent quenching.     

Nitric Oxide Alleviates Oxidative Damage Induced by Enhanced Ultraviolet-B Radiation in Cyanobacterium

To study the role of nitric oxide (NO) on enhanced ultraviolet-B (UV-B) radiation (280–320 nm)-induced damage of Cyanobacterium, the growth, pigment content, and antioxidative activity of Spirulina platensis-794 cells were investigated under enhanced UV-B radiation and under different chemical treatments with or without UV-B radiation for 6 h. The changes in chlorophyll-a, malondialdehyde content, and biomass confirmed that 0.5 mM sodium nitroprusside (SNP), a donor of nitric oxide (NO), could markedly alleviate the damage caused by enhanced UV-B. Specifically, the biomass and the chlorophyll-a content in S. platensis-794 cells decreased 40% and 42%, respectively under enhanced UV-B stress alone, but they only decreased 10% and 18% in the cells treated with UV-B irradiation and 0.5 mM SNP. Further experiments suggested that NO treatment significantly increased the activities of superoxide dismutase (SOD) and catalase (CAT), and decreased the accumulation of O ₂ ⁻ in enhanced UV-B-irradiated cells. SOD and CAT activity increased 0.95- and 6.73-fold, respectively. The accumulation of reduced glutathione (GSH) increased during treatment with 0.5 mM SNP in normal S. platensis cells, but SNP treatment could inhibit the increase of GSH in enhanced UV-B-stressed S. platensis cells. Thus, these results suggest that NO can strongly alleviate oxidative damage caused by UV-B stress by increasing the activities of SOD, peroxidase, CAT, and the accumulation of GSH, and by eliminating O ₂ ⁻ in S. platensis-794 cells. In addition, the difference of NO origin between plants and cyanobacteria are discussed.     

Ultraviolet-B inhibition of motility in green and dark bleachedEuglena gracilis

The motility of green and dark bleachedEuglena gracilis was studied under artificial and solar UV-B radiation. The percentage of motile cells in the population was drastically impaired after exposure to unfiltered sunlight for only a few hours. Dark bleached cells were even more affected than green organisms. The effect is caused mainly by the solar UV-B component, since filtering the sunlight by either a layer of ozone or a UV-B-absorbing filter substantially increased the survival rate. Addition ofp-quinone, a scavenger of free radicals produced in a type I photodynamic reaction, did not relieve the UV-B effects, but was cytotoxic at higher concentrations. Likewise, 1,4-diazobicyclo[2,2,2]octane and imidazole, which quench singlet oxygen (¹O₂) generated in a type II photodynamic reaction, did not prolong the survival in UV-B irradiation. D₂O, which, in contrast, prolongs the lifetime of¹O₂, is tolerated by the cells but does not aggravate the UV-B inhibition. Thus, photodynamic processes of both type I and II can be ruled out as possible mechanisms of UV-B inhibition of motility inEuglena gracilis.     

Growth under UV-B radiation increases tolerance to high-light stress in pea and bean plants

Pea (Pisum sativum L.) and bean (Phaseolus vulgaris L.) plants were exposed to enhanced levels of UV-B radiation in a growth chamber. Leaf discs of UV-B treated and control plants were exposed to high-light (HL) stress (PAR: 1200 mol m^–2 s^–1) to study whether pre-treatment with UV-B affected the photoprotective mechanisms of the plants against photoinhibition. At regular time intervals leaf discs were taken to perform chlorophyll a fluorescence and oxygen evolution measurements to assess damage to the photosystems. Also, after 1 h of HL treatment the concentration of xanthophyll cycle pigments was determined. A significantly slower decline of maximum quantum efficiency of PSII (F _v/F _m), together with a slower decline of oxygen evolution during HL stress was observed in leaf discs of UV-B treated plants compared to controls in both plant species. This indicated an increased tolerance to HL stress in UV-B treated plants. The total pool of xanthophyll cycle pigments was increased in UV-B treated pea plants compared to controls, but in bean no significant differences were found between treatments. However, in bean plants thiol concentrations were significantly enhanced by UV-B treatment, and UV-absorbing compounds increased in both species, indicating a higher antioxidant capacity. An increased leaf thickness, together with increases in antioxidant capacity could have contributed to the higher protection against photoinhibition in UV-B treated plants.     

The ingestion and assimilation of algae by Nais elinguis (Oligochaeta: Naididae)

Summary Nais elinguis was offered equal densities of three algal species under controlled conditions. Colonies of Scenedesmus quadricauda were ingested at significantly lower rates than cell of Nitzschia kutzingiana and Chlorella vulgaris. Labelled cells of N. kutzingiana were more rapidly and more efficiently assimilated than those of the other algae. Cells of S. quadricauda were viable in the faeces.This work confirmed conclusions from other studies with respect to the role of algae in the nutrition of Nais elinguis and other freshwater benthic herbivores.     

Photosynthesis and UV-B Tolerance of the Marine Alga Fucus vesiculosus at Different Sea Water Salinities

The marine algal species in the Baltic Sea are few due to the low sea water salinity. One of the few species that can be found is Fucus vesiculosus. Even this species is affected by the low salinity and becomes smaller in size in the Baltic. In present work the photosynthesis of F. vesiculosus in the northern Baltic (Bothnian Sea) was compared to the photosynthesis of F. vesiculosus in the Atlantic. Oxygen evolution was measured before and after exposure to 2.3 W of UV-B (280–320 nm) radiation for 5 h, as well as after 48 h recovery in low light. The plants were kept in their own sea water salinity as well as in a changed salinity, this to examine possible correlations between salinity and photosynthesis. The results show a significant higher initial maximal photosynthesis (P _max) for Atlantic plants (10.3 nmol O₂ g⁻¹ FW s⁻¹) compared to Baltic plants (4.0 nmol O₂ g⁻¹ FW s⁻¹). The Baltic plants were found more sensitive to UV-B with a 40–50% decrease of P _max as well as a lower degree of recovery (60–70% compared to 75–95% for the Atlantic plants). The higher salinity (35 psu) had a positive effect on the Baltic F. vesiculosus with increased P _max as well as increased tolerance to UV-B. The lower salinity (5 psu) had a negative effect on the Atlantic plants with a decreased P _max as well as a lower tolerance to UV-B. Pigment content was found higher in Atlantic F. vesiculosus. The pigment content decreased then the Atlantic plants were transferred to 5 psu. The concentration of Chl a as well as the total content of violaxanthin, diadinoxanthin and zeaxanthin in Baltic plants increased when transferred to 35 psu. The Atlantic F. vesiculosus can not survive the low salinity in the northern Baltic (died within 8 weeks). It is likely that a long time acclimation or adaptation to low salinity has taken place for F. vesiculosus in northern Baltic. If this is an ecotypic or genotypic development it is too early to say.