Overview and Challenges of Large-Scale Cultivation of Photosynthetic Microalgae and Cyanobacteria.

Microalgae and cyanobacteria are diverse groups of organisms with great potential to benefit societies across the world. These organisms are currently used in food, feed, pharmaceutical and cosmetic industries. In addition, a variety of novel compounds are being isolated. Commercial production of photosynthetic microalgae and cyanobacteria requires cultivation on a large scale with high throughput. However, scaling up production from lab-based systems to large-scale systems is a complex and potentially costly endeavor. In this review, we summarise all aspects of large-scale cultivation, including aims of cultivation, species selection, types of cultivation (ponds, photobioreactors, and biofilms), water and nutrient sources, temperature, light and mixing, monitoring, contamination, harvesting strategies, and potential environmental risks. Importantly, we also present practical recommendations and discuss challenges of profitable large-scale systems associated with economical design, effective operation and maintenance, automation, and shortage of experienced phycologists.

Particles as carriers of matter in the aquatic environment: Challenges and ways ahead for transdisciplinary research.

A diverse array of natural and anthropogenic particles found in the aquatic environment, can act as carriers of co-transported matter (CTM), such as nutrients, genetic material and contaminants. Thus, understanding carrier particle transport will increase our understanding of local and global fluxes of exogenous CTM (affiliated with the particle) and endogenous CTM (an inherent part of the particle). In the present contribution, researchers from multiple disciplines collaborated to provide perspectives on the interactions between carrier particles and CTM, and the fundamentals of transport of particles found in the aquatic environment and the generic spherical smooth particles, often used to make predictions about particle behavior in suspension. Evidently, the particles in the aquatic environment show a great variety of characteristics and vary greatly from each other as well as from the generic particle. However, in spite of these differences, many fundamental concepts apply to particles in general. We emphasize the importance of understanding the basic concepts of transport of particle-associated CTM, and the main assumptions in the generic-founded models, which are challenged by the diverging characteristics of particles found in the aquatic environment, as paramount moving forward. Additionally, we identified the need for a conceptual and semantic link between different scientific fields of particle research and initiated the formation of a consistent terminology. Disciplinary and organizational (academic and funding) barriers need to be overcome to enable individual researchers to move beyond their knowledge sphere, to stimulate future interdisciplinary collaborations and to avoid research silos. Hereby, we can foster faster and better progress of evolving research fields on new and emerging anthropogenic carrier particles, and stimulate the development of solutions to the technological and environmental challenges.

A simple and fast method for extraction and quantification of cryptophyte phycoerythrin.

The microalgal pigment phycoerythrin (PE) is of commercial interest as natural colorant in food and cosmetics, as well as fluoroprobes for laboratory analysis. Several methods for extraction and quantification of PE are available but they comprise typically various extraction buffers, repetitive freeze-thaw cycles and liquid nitrogen, making extraction procedures more complicated. A simple method for extraction of PE from cryptophytes is described using standard laboratory materials and equipment. The cryptophyte cells on the filters were disrupted at -80 °C and added phosphate buffer for extraction at 4 °C followed by absorbance measurement. The cryptophyte Rhodomonas salina was used as a model organism. •Simple method for extraction and quantification of phycoerythrin from cryptophytes.•Minimal usage of equipment and chemicals, and low labor costs.•Applicable for industrial and biological purposes.

Distribution, structure and function of Nordic eelgrass (Zostera marina) ecosystems: implications for coastal management and conservation.

This paper focuses on the marine foundation eelgrass species, Zostera marina, along a gradient from the northern Baltic Sea to the north-east Atlantic. This vast region supports a minimum of 1480 km2 eelgrass (maximum >2100 km2), which corresponds to more than four times the previously quantified area of eelgrass in Western Europe.Eelgrass meadows in the low salinity Baltic Sea support the highest diversity (4-6 spp.) of angiosperms overall, but eelgrass productivity is low (<2 g dw m-2 d-1) and meadows are isolated and genetically impoverished. Higher salinity areas support monospecific meadows, with higher productivity (3-10 g dw m-2 d-1) and greater genetic connectivity. The salinity gradient further imposes functional differences in biodiversity and food webs, in particular a decline in number, but increase in biomass of mesograzers in the Baltic.Significant declines in eelgrass depth limits and areal cover are documented, particularly in regions experiencing high human pressure. The failure of eelgrass to re-establish itself in affected areas, despite nutrient reductions and improved water quality, signals complex recovery trajectories and calls for much greater conservation effort to protect existing meadows.The knowledge base for Nordic eelgrass meadows is broad and sufficient to establish monitoring objectives across nine national borders. Nevertheless, ensuring awareness of their vulnerability remains challenging. Given the areal extent of Nordic eelgrass systems and the ecosystem services they provide, it is crucial to further develop incentives for protecting them. © 2014 The Authors. Aquatic Conservation: Marine and Freshwater Ecosystems published by John Wiley & Sons, Ltd.

Differences in the structure of anthocyanins from the two amphibious plants, Lobelia cardinalis and Nesaea crassicaulis.

The foliar anthocyanin profiles of two amphibious plants, Nesaea crassicaulis and Lobelia cardinalis were analysed for the first time. N. crassicaulis produced very simple anthocyanins, achieving the highest concentrations when grown submerged. In contrast, L. cardinalis produced leaves with a high content of very complex, acylated anthocyanins, especially when growing emergent. Anthocyanins were separated by high performance liquid chromatography. Nesaea crassicaulis anthocyanins were identified according to their fragment mass spectra and ultra-visible-violet spectral characteristics and 1D and 2D NMR spectra as -3,5-di-O-ß-glucosides of delphinidin, cyanidin, petunidin, malvidin and peonidin as well as cyanidine and peonidin-3-O-ß-glucoside. In L. cardinalis cyanidin-3-O-[6-O-(4-O-E-p-coumaroyl-O-α-rhamnopyranosyl)-ß-glucopyrano]-5-O-ß-glucopyranoside was the major anthocyanin and contributed more than 98% of total anthocyanin content. The remaining 2% was made up by cyanidin-3-O-[6-O-(4-O-E-caffeoyl-O-α-rhamnopyranosyl)-ß-glucopyrano]-5-O-ß-glucopyranoside and pelargonidin-3-O-[6-O-(4-O-E-p-coumaroyl-O-α-rhamnopyranosyl)-ß-glucopyrano]-5-O-ß-glucopyranoside.

Temperature acclimation and heat tolerance of photosynthesis in Norwegian Saccharina latissima (Laminariales, Phaeophyceae).

Kelps, seaweeds and seagrasses provide important ecosystem services in coastal areas, and loss of these macrophytes is a global concern. Recent surveys have documented severe declines in populations of the dominant kelp species, Saccharina latissima, along the south coast of Norway. S. latissima is a cold-temperate species, and increasing seawater temperature has been suggested as one of the major causes of the decline. Several studies have shown that S. latissima can acclimate to a wide range of temperatures. However, local adaptations may render the extrapolation of existing results inappropriate. We investigated the potential for thermal acclimation and heat tolerance in S. latissima collected from three locations along the south coast of Norway. Plants were kept in laboratory cultures at three different growth temperatures (10, 15, and 20°C) for 4-6 weeks, after which their photosynthetic performance, fluorescence parameters, and pigment concentrations were measured. S. latissima obtained almost identical photosynthetic characteristics when grown at 10 and 15°C, indicating thermal acclimation at these temperatures. In contrast, plants grown at 20°C suffered substantial tissue deterioration, and showed reduced net photosynthetic capacity caused by a combination of elevated respiration and reduced gross photosynthesis due to lowered pigment concentrations, altered pigment composition, and reduced functionality of Photo-system II. Our results support the hypothesis that extraordinarily high temperatures, as observed in 1997, 2002, and 2006, may have initiated the declines in S. latissima populations along the south coast of Norway. However, observations of high mortality in years with low summer temperatures suggest that reduced population resilience or other factors may have contributed to the losses.

Adaptation to high light irradiances enhances the photosynthetic Cu2+ resistance in Cu2+ tolerant and non-tolerant populations of the brown macroalgae Fucus serratus.

The relationship between light acclimation and Cu(2+) tolerance was studied in two populations of Fucus serratus known to be naturally non-tolerant and tolerant to Cu(2+). Acclimation to high irradiances increased the photosynthetic tolerance to Cu(2+). The xanthophyll cycle was apparently not involved in protecting the photosynthetic apparatus against Cu(2+) toxicity, as results showed that Cu(2+) did not induce dynamic photoinhibition. The higher photosynthetic Cu(2+) resistance of high light algae did not result in increased growth. The excess energy acquired by high light-adapted algae appeared to be utilized in Cu(2+) defense mechanisms in the Cu(2+) non-tolerant population. The polyphenol content of the algae was reciprocal to the Cu(T) content, suggesting that polyphenol may be the primary Cu(2+) defense of non-tolerant low light algae, acting through secretion and extracellular chelating of Cu(2+), while the compounds do not seem to be involved in the primary Cu(2+) tolerance mechanism in Cu(2+) tolerant algae.

Pigments, photosynthesis and photoinhibition in two amphibious plants: consequences of varying carbon availability.

In the present study, we investigated the effects of CO(2) availability on photosynthesis, photoinhibition and pigmentation in two species of amphibious plants, Lobelia cardinalis and Nesaea crassicaulis. The plants were grown emergent under atmospheric conditions and submerged under low and high CO(2) availability. Compared with Lobelia, Nesaea had thin leaves and few stomata in all CO(2) treatments. While Lobelia expressed no variation in anthocyanin content among treatments, Nesaea produced high concentrations of anthocyanin when submerged. Lobelia photosynthesis increased in response to increasing CO(2) availability, and photoinhibition was negatively related to xanthophyll content. By contrast, Nesaea photosynthesis was highest under submerged conditions, and there was no relationship between photoinhibition and the xanthophyll content. We conclude that the response of Lobelia to varying CO(2) availability is similar to that of terrestrial plants and that this species relies on the xanthophyll cycle for nonphotochemical quenching (NPQ) and protection against photoinhibition. By contrast, the thin leaves, few stomata and low levels of chlorophylls and accessory pigments in Nesaea, relative to Lobelia, suggest adaptation to a submerged habitat. While Nesaea does not seem to rely on the xanthophyll cycle or other xanthophylls for NPQ, some role of anthocyanins in the protection against photoinhibition cannot be ruled out, owing to its effect as a sunscreen and as an efficient quencher of free radicals.

Photosynthetic responses to Cu2+ exposure are independent of light acclimation and uncoupled from growth inhibition in Fucus serratus (Phaeophyceae).

We have studied the effect of light acclimation on photosynthetic responses and growth during Cu2+ exposure (0-0.84 microM) in the brown seaweed Fucus serratus. Measurements of chlorophyll fluorescence parameters showed that Cu2+ exposure amplified ETR, reduced the chlorophyll content at the cellular level and that there was no effect of light adaptation on the Cu2+ resistance of the algae. In contrast to the inhibitory effects of Cu2+ on chlorophyll fluorescence, O2 evolution and the total content of chlorophyll and carotenoid of the algae was unaffected by Cu2+. We conclude that photoinhibition and perhaps pigment degradation in the meristoderm was compensated for by cells deeper in the thallus with the result that the overall photosynthetic fitness of the algae was maintained. The pronounced inhibitory effects of Cu2+ on algae growth was not a consequence of photoinhibition and could be attributed to direct inhibitory effects on the growth process.

Broad-scale comparison of photosynthetic rates across phototrophic organisms.

We tested the existence of general patterns in the photosynthetic metabolism of oxygen-evolving organisms, based on a compilation of data for 315 species ranging from cyanobacteria to tree leaves. We used thickness and chlorophyll a concentration of the photosynthetic structure (cell, thallus, leaf) to scale differences in photosynthetic metabolism among plants, because of the demonstrated importance of these plant traits in regulating light absorption properties and photosynthetic rates of particular plant groups. We examined only the properties of the photosynthetic structure because this is the plant unit responsible for the photosynthetic process and thus is closely related to plant productivity, whereas there is a lack of general quantitative descriptors of the whole organism useful for such broad-scale comparisons, and few studies report net photosynthetic rates of whole organisms, including respiration rates of all non-photosynthetic structures. The results demonstrated that descriptors of plant metabolism such as maximum net photosynthesis, initial slope of the photosynthesis-irradiance (PI) curve and dark respiration display strong positive interrelationships. The metabolic rates declined with increasing thickness of the photosynthetic structures and more steeply for photosynthesis than respiration. Photosynthetic rates also changed with increment of volume of the photosynthetic structure resembling patterns that have been previously described for animal metabolism related to body weight. The strong relationship of metabolic rate and chlorophyll a concentration to the thickness of photosynthetic tissue reflects broad-scale patterns and not the adaptive response of individual or closely-related species of similar tissue thickness to varying environmental conditions. Thickness of the photosynthetic structures, therefore, plays an important role in the environmental control of plant performance and, consequently, it might have been an important driver of plant evolution, setting thresholds to the metabolism and productivity of phototrophic organisms.

Land plants of amphibious Littorella uniflora (L.) Aschers. maintain utilization of CO2 from the sediment.

Submerged macrophytes of the isoetid life form derive the majority of their CO2 for photosynthesis from the sediment. The experiments described here were designed to test the hypothesis that root uptake of CO2 is important also in the terrestrial form of Littorella uniflora. The results of 14CO2 experiments showed that sediment CO2 contributed 56% of the total fixation at 0.1MM CO2 in the rhizosphere, 83% at 0.5MM and 96% at 2.5MM. Sediment CO2 in emergent Littorella stands ranged from 0.1 to 1.0MM and averaged 0.5MM. Measurements of the net CO2 exchange over the leaves showed an even higher dependence of the sediment as CO2 source. Littorella leaves had no stomata at the base and densities (ca. 100 mm-2) typical of terrestrial plants at the tip, allowing sediment-derived CO2 to be supplied along the length of the leaf. The stomata permit supply of CO2 from the air during periods of reduced sediment CO2 concentrations (e.g. if the sediment dries up) and regulate transpiration.

Regulation of photosynthetic rates of submerged rooted macrophytes.

Fourteen temperate, submerged macrophytes were cultivated in the laboratory at high DIC levels (3.3-3.8 mM), 10.4-14.4 mol photons (PAR) m-2 d-1 and 15°C. Photosynthesis at photosaturation ranged between 0.59 and 17.98 mg O2 g-1 DW h-1 at ambient pH (8.3) and were markedly higher between 1.76 and 47.11 mg O2 g-1 DW h-1 at pH 6.5 under elevated CO2 concentrations. Photosynthetic rates were significantly related to both the relative surface area and the chlorophyll content of the leaves. Consequently, the photosynthetic rate was much less variable among the species when expressed per surface area and chlorophyll content instead of dry mass. The chlorophyll content was probably a main predictor of photosynthesis of submerged leaves because of the direct relationship of chlorophyll to the light harvesting capacity and/or a coupling to the capacity for photosynthetic electron transport and carboxylation. A comparison with terrestrial leaves characterized the submerged leaves by their low chlorophyll concentrations and low photosynthetic rates per surface area due to the thin leaves. Photosynthetic rates per chlorophyll content in submerged leaves at CO2 saturation, however, were at the same level as photosynthesis in terrestrial leaves measured at ambient CO2 when appropriate corrections were made for differences in incubation temperature.