Warming and UV Radiation Alleviate the Effect of Virus Infection on the Microalga Emiliania huxleyi.

The marine microalga Emiliania huxleyi is widely distributed in the surface oceans and is prone to infection by coccolithoviruses that can terminate its blooms. However, little is known about how global change factors like solar UV radiation (UVR) and ocean warming affect the host-virus interaction. We grew the microalga at 2 temperature levels with or without the virus in the presence or absence of UVR and investigated the physiological and transcriptional responses.

Reduced primary productivity and notable resilience of phytoplankton community in the coastal water of southern China under a marine heatwave.

Increasing frequency, intensity and duration of marine heatwaves (MHWs) are supposed to affect coastal biological production in different regions to different extents. To understand how MHWs impact coastal primary productivity and community succession of phytoplankton and assess the changes in resilience of phytoplankton communities, we conducted a mesoscale enclosure experiment simulating a MHW in the coastal water of southern China. After 8 days of the MHW (+3 °C) treatment, community biomass was significantly lower than the control's, and primary productivity per volume of water was reduced by about 56%.

The copepod Acartia spinicauda feeds less and dies more under the influences of solar ultraviolet radiation and elevated pCO.

While solar ultraviolet radiation (UVR) is known to impact zooplankton, little has been documented on its impacts under elevated pCO. Here, we show that exposure to UVR decreased the feeding and survival rates of the copepod Acartia spinicauda, that artificial UV-B of 2.25 W·m for 4 h resulted in a 52 % inhibition of its grazing rates and a 45 % reduction in survival rates compared to visible light alone.

Marine heatwaves alter competition between the cultured macroalga Gracilariopsis lemaneiformis and the harmful bloom alga Skeletonema costatum.

Seaweed cultivation can inhibit the occurrence of red tides. However, how seaweed aquaculture interactions with harmful algal blooms will be affected by the increasing occurrence and intensity of marine heatwaves (MHWs) is unknown. In this study, we run both monoculture and coculture systems to investigate the effects of a simulated heatwave on the competition of the economically important macroalga Gracilariopsis lemaneiformis against the harmful bloom diatom Skeletonema costatum.

Correlation of methane production with physiological traits in IMS 101 grown with methylphosphonate at different temperatures.

The diazotrophic cyanobacterium has been recognized as a potentially significant contributor to aerobic methane generation via several mechanisms including the utilization of methylphophonate (MPn) as a source of phosphorus. Currently, there is no information about how environmental factors regulate methane production by . Here, we grew IMS101 at five temperatures ranging from 16 to 31°C, and found that its methane production rates increased with rising temperatures to peak (1.

Ocean acidification alters microeukaryotic and bacterial food web interactions in a eutrophic subtropical mesocosm.

Ocean acidification (OA) is known to influence biological and ecological processes, mainly focusing on its impacts on single species, but little has been documented on how OA may alter plankton community interactions. Here, we conducted a mesocosm experiment with ambient (∼410 ppmv) and high (1000 ppmv) CO concentrations in a subtropical eutrophic region of the East China Sea and examined the community dynamics of microeukaryotes, bacterioplankton and microeukaryote-attached bacteria in the enclosed coastal seawater. The OA treatment with elevated CO affected taxa as the phytoplankton bloom stages progressed, with a 72.

Ocean acidification and desalination increase the growth and photosynthesis of the diatom Skeletonema costatum isolated from the coastal water of the Yellow Sea.

Global climate changes induce substantial alterations in the marine system, including ocean acidification (OA), desalination and warming of surface seawater. Here, we examined the combined effects of OA and reduced salinity under different temperatures on the growth and photosynthesis of the diatom Skeletonema costatum. After having been acclimated to 2 CO concentrations (400 μatm, 1000 μatm) and 2 salinity levels (20 psu, 30 psu) at temperature levels of 10 °C and 20 °C, the diatom showed enhanced growth rate at the lowered salinity and elevated pCO irrespective of the temperature.

UV-A radiation increases biomass yield by enhancing energy flow and carbon assimilation in the edible cyanobacterium .

Ultraviolet (UV) A radiation (315-400 nm) is the predominant component of solar UV radiation that reaches the Earth's surface. However, the underlying mechanisms of the positive effects of UV-A on photosynthetic organisms have not yet been elucidated. In this study, we investigated the effects of UV-A radiation on the growth, photosynthetic ability, and metabolome of the edible cyanobacterium .

Shift in algal blooms from micro- to macroalgae around China with increasing eutrophication and climate change.

Blooms of microalgal red tides and macroalgae (e.g., green and golden tides caused by Ulva and Sargassum) have caused widespread problems around China in recent years, but there is uncertainty around what triggers these blooms and how they interact.

Warming exacerbates the impacts of ultraviolet radiation in temperate diatoms but alleviates the effect on polar species.

Under global change scenarios, the sea surface temperature is increasing steadily along with other changes to oceanic environments. Consequently, marine diatoms are influenced by multiple ocean global change drivers. We hypothesized that temperature rise mediates the responses of polar and temperate diatoms to UV radiation (UVR) to different extents, and exposed the temperate centric diatoms, Thalassiosira weissflogii and Skeletonema costatum, and a polar pennate diatom Entomoneis sp.

Light history modulates growth and photosynthetic responses of a diatom to ocean acidification and UV radiation.

Unlabelled: To examine the synergetic effects of ocean acidification (OA) and light intensity on the photosynthetic performance of marine diatoms, the marine centric diatom was cultured under ambient low CO (LC, 390 μatm) and elevated high CO (HC, 1000 μatm) levels under low-light (LL, 60 μmol m s) or high-light (HL, 220 μmol m s) conditions for over 20 generations. HL stimulated the growth rate by 128 and 99% but decreased cell size by 9 and 7% under LC and HC conditions, respectively. However, HC did not change the growth rate under LL but decreased it by 9% under HL.

Deoxygenation enhances photosynthetic performance and increases N fixation in the marine cyanobacterium under elevated CO.

Effects of changed levels of dissolved O and CO on marine primary producers are of general concern with respect to ecological effects of ongoing ocean deoxygenation and acidification as well as upwelled seawaters. We investigated the response of the diazotroph IMS 101 after it had acclimated to lowered O (~60 μM O) and/or elevated CO levels (HC, ~32 μM CO) for about 20 generations. Our results showed that reduced O levels decreased dark respiration significantly, and increased the net photosynthetic rate by 66 and 89% under the ambient (AC, ~13 μM CO) and the HC, respectively.

Increased genetic diversity loss and genetic differentiation in a model marine diatom adapted to ocean warming compared to high CO.

Although high CO and warming could act interactively on marine phytoplankton, little is known about the molecular basis for this interaction on an evolutionary scale. Here we explored the adaptation to high CO in combination with warming in a model marine diatom Phaeodactylum tricornutum. Whole-genome re-sequencing identifies, in comparison to populations grown under control conditions, a larger genetic diversity loss and a higher genetic differentiation in the populations adapted for 2 years to warming than in those adapted to high CO.

Corrigendum: Applying Dialysis Bags to Grow Microalgae and Measure Grazing Rates by Secondary Producers.

[This corrects the article DOI: 10.3389/fphys.2022.

Applying Dialysis Bags to Grow Microalgae and Measure Grazing Rates by Secondary Producers.

Traditional methods using sealed bottles to determine the grazing rates by secondary producers neglect chemical changes induced by biological activities during the incubation, giving rise to instable levels of nutrients, pH, CO, O and other chemicals along with changing microalgal cell concentrations and grazers' metabolism. Here, we used dialysis bags, which allows exchanges of nutrients and gases, to grow microalgae and to determine grazing rates of secondary producers. The specific growth rate of diatom within the dialysis bags increased with increasing water velocities, indicating its suitability to grow microalgae under dynamic water conditions.

Elevated pCO changes community structure and function by affecting phytoplankton group-specific mortality.

The rise of atmospheric pCO has created a number of problems for marine ecosystem. In this study, we initially quantified the effects of elevated pCO on the group-specific mortality of phytoplankton in a natural community based on the results of mesocosm experiments. Diatoms dominated the phytoplankton community, and the concentration of chlorophyll a was significantly higher in the high-pCO treatment than the low-pCO treatment.

Enhancement of diatom growth and phytoplankton productivity with reduced O availability is moderated by rising CO.

Many marine organisms are exposed to decreasing O levels due to warming-induced expansion of hypoxic zones and ocean deoxygenation (DeO). Nevertheless, effects of DeO on phytoplankton have been neglected due to technical bottlenecks on examining O effects on O-producing organisms. Here we show that lowered O levels increased primary productivity of a coastal phytoplankton assemblage, and enhanced photosynthesis and growth in the coastal diatom Thalassiosira weissflogii.

Nitrogen-limitation exacerbates the impact of ultraviolet radiation on the coccolithophore Gephyrocapsa oceanica.

To investigate effects of UV radiation (UVR, 280-400 nm) on coccolithophorids under nutrient-limited conditions, we grew Gephyrocapsa oceanica to determine its resilience to consecutive daily short-term exposures to +UVR (irradiances >295 nm) under a range of nitrate availabilities (100, 24, 12, 6 and 3 μM). +UVR alone significantly hampered the growth of G. oceanica, with the synergistic negative effects of +UVR and N-limitation being about 58% and 22% greater than under UVR or N-limitation alone, respectively.

Additive impacts of ocean acidification and ambient ultraviolet radiation threaten calcifying marine primary producers.

Ocean acidification (OA) represents a threat to marine organisms and ecosystems. However, OA rarely exists in isolation but occurs concomitantly with other stressors such as ultraviolet radiation (UVR), whose effects have been neglected in oceanographical observations. Here, we perform a quantitative meta-analysis based on 373 published experimental assessments from 26 studies to examine the combined effects of OA and UVR on marine primary producers.

Ocean acidification exacerbates copper toxicity in both juvenile and adult stages of the green tide alga Ulva linza.

The toxicity of heavy metals to coastal organisms can be modulated by changes in pH due to progressive ocean acidification (OA). We investigated the combined impacts of copper and OA on different stages of the green macroalga Ulva linza, which is widely distributed in coastal waters, by growing the alga under the addition of Cu (control, 0.125 (medium, MCu), and 0.

Effects of climate change factors on marine macroalgae: A review.

Marine macroalgae, the main primary producers in coastal waters, play important roles in the fishery industry and global carbon cycles. With progressive ocean global changes, however, they are increasingly exposed to enhanced levels of multiple environmental drivers, such as ocean acidification, warming, heatwaves, UV radiation and deoxygenation. While most macroalgae have developed physiological strategies against variations of these drivers, their eco-physiological responses to each or combinations of the drivers differ spatiotemporally and species-specifically.

Ultraviolet Radiation Stimulates Activity of CO Concentrating Mechanisms in a Bloom-Forming Diatom Under Reduced CO Availability.

The diatom is cosmopolitan and forms algal blooms in coastal waters, being exposed to varying levels of solar UV radiation (UVR) and reduced levels of carbon dioxide (CO). While reduced CO availability is known to enhance CO concentrating mechanisms (CCMs) in this diatom and others, little is known on the effects of UV on microalgal CCMs, especially when CO levels fluctuate in coastal waters. Here, we show that upregulated its CCMs in response to UVR (295-395 nm), especially to UVA (320-395 nm) in the presence and absence of photosynthetically active radiation (PAR).

Photosynthesis and calcification of the coccolithophore Emiliania huxleyi are more sensitive to changed levels of light and CO under nutrient limitation.

Photophysiological responses of phytoplankton to changing multiple environmental drivers are essential in understanding and predicting ecological consequences of ocean climate changes. In this study, we investigated the combined effects of two CO levels (410 and 925 μatm) and five light intensities (80 to 480 μmol photons m s) on cellular pigments contents, photosynthesis and calcification of the coccolithophore Emiliania huxleyi grown under nutrient replete and limited conditions, respectively. Our results showed that high light intensity, high CO level and nitrate limitation acted synergistically to reduce cellular chlorophyll a and carotenoid contents.

Nitrogen Limitation Decreases the Repair Capacity and Enhances Photoinhibition of Photosystem II in a Diatom.

Macronutrient limitation and increased solar exposure coincide with ocean warming-enhanced stratification, with consequences for phytoplankton within the upper mixing layer. In this study, we grew a diatom, Thalassiosira punctigera, under nitrogen-limited and replete conditions for more than 14 generations and investigated both the biochemical composition of treated cells and their photochemical responses to high light and UV exposure. The photosynthetic pigment and the particulate organic nitrogen (PON) content significantly decreased in the low nitrate grown cells, with drastic decline of the absorption of UV absorbing compounds.