Short-term response to light after the polar night in the Arctic kelps Alaria esculenta and Saccharina latissima.

The current absence of ice in early spring in a number of Arctic fjords allows sunlight to penetrate the water column about two months earlier than it used to be when a thick ice cover was present. This can potentially change the growth dynamics of permanent seaweed forests. To elucidate the ability of seaweeds to take advantage of this early available light, growth, photosynthetic performance, and biochemical composition has been analyzed in two major forest-forming algal species, Alaria esculenta and Saccharina latissima, from Kongsfjorden (Svalbard) collected in early February, and incubated in dim light and dark conditions.

Underwater Light Manipulation by the Benthic Diatom : From PAR Efficient Collection to UVR Screening.

Several species of diatoms, unicellular microalgae which constitute the main component of phytoplankton, are characterized by an impressive photosynthetic efficiency while presenting a noticeable tolerance versus exposure to detrimental UV radiation (UVR). In particular, the growth rate of the araphid diatom is not significantly affected by harsh treatments with UVR, even in absence of detectable, specific UV-absorbing pigments and even if it is not able to avoid high UV exposure by motility. In this work we applied a multi-disciplinary approach involving numerical computation, photonics, and biological parameters in order to investigate the possible role of the frustule, micro- and nano-patterned silica shell which encloses the cell, in the ability of to efficiently collect photosynthetic active radiation (PAR) and to simultaneously screen the protoplasm from UVR.

Effects of seawater scrubbing on a microplanktonic community during a summer-bloom in the Baltic Sea.

The International Maritime Organization (IMO) has gradually applied stricter regulations on the maximum sulphur content permitted in marine fuels and from January 1, 2020, the global fuel sulphur limit was reduced from 3.5% to 0.5%.

A reflection on four impactful Ambio papers: The biotic perspective : This article belongs to Ambio's 50th Anniversary Collection. Theme: Climate change impacts.

Climate change represents one of the most pressing societal and scientific challenges of our time. While much of the current research on climate change focuses on future prediction, some of the strongest signals of warming can already be seen in Arctic and alpine areas, where temperatures are rising faster than the global average, and in the oceans, where the combination of rising temperatures and acidification due to increased CO concentrations has had catastrophic consequences for sensitive marine organisms inhabiting coral reefs. The scientific papers highlighted as part of this anniversary issue represent some of the most impactful advances in our understanding of the consequences of anthropogenic climate change.

Cultivation and Photophysiological Characteristics of Desmids in Moderately Saline Aquaculture Wastewater.

Although desmids typically inhabit freshwater environments characterized by low amounts of nutrients and low salinity, several desmid species have been recorded in eutrophic waters, indicating their adaptation to elevated pollution and conductivity. This study aimed to determine whether desmids could be used for remediation of moderately saline aquaculture wastewater (AWW) from a fish farm situated in the southeast of Sweden. Fourteen desmid strains isolated from different climates (tropical to polar) and trophic conditions (oligotrophic to eutrophic) were cultivated in diluted AWW and we estimated their growth rates, biomass, nutrient removal efficiency, chlorophyll fluorescence parameters and cellular C, N and P quotas.

Glacial melt disturbance shifts community metabolism of an Antarctic seafloor ecosystem from net autotrophy to heterotrophy.

Climate change-induced glacial melt affects benthic ecosystems along the West Antarctic Peninsula, but current understanding of the effects on benthic primary production and respiration is limited. Here we demonstrate with a series of in situ community metabolism measurements that climate-related glacial melt disturbance shifts benthic communities from net autotrophy to heterotrophy. With little glacial melt disturbance (during cold El Niño spring 2015), clear waters enabled high benthic microalgal production, resulting in net autotrophic benthic communities.

Future HAB science: Directions and challenges in a changing climate.

There is increasing concern that accelerating environmental change attributed to human-induced warming of the planet may substantially alter the patterns, distribution and intensity of Harmful Algal Blooms (HABs). Changes in temperature, ocean acidification, precipitation, nutrient stress or availability, and the physical structure of the water column all influence the productivity, composition, and global range of phytoplankton assemblages, but large uncertainty remains about how integration of these climate drivers might shape future HABs. Presented here are the collective deliberations from a symposium on HABs and climate change where the research challenges to understanding potential linkages between HABs and climate were considered, along with new research directions to better define these linkages.

Diatom frustules enhancing the efficiency of gel polymer electrolyte based dye-sensitized solar cells with multilayer photoelectrodes.

The incorporation of nanostructures that improve light scattering and dye adsorption has been suggested for dye-sensitized solar cells (DSSCs), but the manufacture of photonic and nanostructured materials with the desired properties is not an easy task. In nature, however, the process of light-harvesting for photosynthesis has, in some cases, evolved structures with remarkable wavelength-sensitive light-trapping properties. The present work is focused on enhancing the efficiency of quasi solid-state DSSCs by capitalizing on the light trapping properties of diatom frustules since they provide complex 3-dimensional structures for scattering and trapping light.

Fatty acids as chemotaxonomic and ecophysiological traits in green microalgae (desmids, Zygnematophyceae, Streptophyta): A discriminant analysis approach.

Desmids (Zygnematophyceae) are a group of poorly studied green microalgae. The aim of the present study was to identify fatty acids (FAs) that could be used as biomarkers in desmids in general, and to determine FAs as traits within different ecophysiological desmid groups. FA profiles of 29 desmid strains were determined and analysed with respect to their geographic origin, trophic preference and age of cultivation.

Microalgal photophysiology and macronutrient distribution in summer sea ice in the Amundsen and Ross Seas, Antarctica.

Our study addresses how environmental variables, such as macronutrients concentrations, snow cover, carbonate chemistry and salinity affect the photophysiology and biomass of Antarctic sea-ice algae. We have measured vertical profiles of inorganic macronutrients (phosphate, nitrite + nitrate and silicic acid) in summer sea ice and photophysiology of ice algal assemblages in the poorly studied Amundsen and Ross Seas sectors of the Southern Ocean. Brine-scaled bacterial abundance, chl a and macronutrient concentrations were often high in the ice and positively correlated with each other.

Diatom frustules protect DNA from ultraviolet light.

The evolutionary causes for generation of nano and microstructured silica by photosynthetic algae are not yet deciphered. Diatoms are single photosynthetic algal cells populating the oceans and waters around the globe. They generate a considerable fraction (20-30%) of all oxygen from photosynthesis, and 45% of total primary production of organic material in the sea.

Ocean acidification and desalination: climate-driven change in a Baltic Sea summer microplanktonic community.

Helcom scenario modelling suggests that the Baltic Sea, one of the largest brackish-water bodies in the world, could expect increased precipitation (decreased salinity) and increased concentration of atmospheric CO over the next 100 years. These changes are expected to affect the microplanktonic food web, and thereby nutrient and carbon cycling, in a complex and possibly synergistic manner. In the Baltic Proper, the extensive summer blooms dominated by the filamentous cyanobacteria sp.

Harmful algal blooms and climate change: Learning from the past and present to forecast the future.

Climate change pressures will influence marine planktonic systems globally, and it is conceivable that harmful algal blooms may increase in frequency and severity. These pressures will be manifest as alterations in temperature, stratification, light, ocean acidification, precipitation-induced nutrient inputs, and grazing, but absence of fundamental knowledge of the mechanisms driving harmful algal blooms frustrates most hope of forecasting their future prevalence. Summarized here is the consensus of a recent workshop held to address what currently is known and not known about the environmental conditions that favor initiation and maintenance of harmful algal blooms.

Long-term acclimation to elevated pCO2 alters carbon metabolism and reduces growth in the Antarctic diatom Nitzschia lecointei.

Increasing atmospheric CO2 levels are driving changes in the seawater carbonate system, resulting in higher pCO2 and reduced pH (ocean acidification). Many studies on marine organisms have focused on short-term physiological responses to increased pCO2, and few on slow-growing polar organisms with a relative low adaptation potential. In order to recognize the consequences of climate change in biological systems, acclimation and adaptation to new environments are crucial to address.

Physicochemical control of bacterial and protist community composition and diversity in Antarctic sea ice.

Due to climate change, sea ice experiences changes in terms of extent and physical properties. In order to understand how sea ice microbial communities are affected by changes in physicochemical properties of the ice, we used 454-sequencing of 16S and 18S rRNA genes to examine environmental control of microbial diversity and composition in Antarctic sea ice. We observed a high diversity and richness of bacteria, which were strongly negatively correlated with temperature and positively with brine salinity.

UVR defense mechanisms in eurytopic and invasive Gracilaria vermiculophylla (Gracilariales, Rhodophyta).

The invasive success of Gracilaria vermiculophylla has been attributed to its wide tolerance range to different abiotic factors, but its response to ultraviolet radiation (UVR) is yet to be investigated. In the laboratory, carpospores and vegetative thalli of an Atlantic population were exposed to different radiation treatments consisting of high PAR (photosynthetically active radiation) only (P), PAR+UV-A (PA) and PAR+UV-A+UV-B (PAB). Photosynthesis of carpospores was photoinhibited under different radiation treatments but photosystem II (PSII) function was restored after 12 h under dim white light.

Interspecific resource competition-combined effects of radiation and nutrient limitation on two diazotrophic filamentous cyanobacteria.

The cyanobacterial blooms in the Baltic Sea are dominated by diazotrophic cyanobacteria, the potentially toxic species Aphanizomenon sp. and the toxic species Nodularia spumigena. The seasonal succession with peaks of Aphanizomenon sp.

SENSITIVITY OF ANTARCTIC UROSPORA PENICILLIFORMIS (ULOTRICHALES, CHLOROPHYTA) TO ULTRAVIOLET RADIATION IS LIFE-STAGE DEPENDENT(1).

The sensitivity of different life stages of the eulittoral green alga Urospora penicilliformis (Roth) Aresch. to ultraviolet radiation (UVR) was examined in the laboratory. Gametophytic filaments and propagules (zoospores and gametes) released from filaments were separately exposed to different fluence of radiation treatments consisting of PAR (P = 400-700 nm), PAR + ultraviolet A (UVA) (PA, UVA = 320-400 nm), and PAR + UVA + ultraviolet B (UVB) (PAB, UVB = 280-320 nm).

Photosynthetic response of Nodularia spumigena to UV and photosynthetically active radiation depends on nutrient (N and P) availability.

Biomass of N. spumigena is distributed within the dynamic photic zone that changes in both light quantity and quality. This study was designed to determine whether nutrient status can mitigate the negative impacts of experimental radiation treatments on the photosynthetic performance of N.

Interaction effects of ambient UV radiation and nutrient limitation on the toxic cyanobacterium Nodularia spumigena.

Nodularia spumigena is one of the dominating species during the extensive cyanobacterial blooms in the Baltic Sea. The blooms coincide with strong light, stable stratification, low ratios of dissolved inorganic nitrogen, and dissolved inorganic phosphorus. The ability of nitrogen fixation, a high tolerance to phosphorus starvation, and different photo-protective strategies (production of mycosporine-like amino acids, MAAs) may give N.