Increasing pCO2 correlates with low concentrations of intracellular dimethylsulfoniopropionate in the sea anemone Anemonia viridis.

Marine anthozoans maintain a mutualistic symbiosis with dinoflagellates that are prolific producers of the algal secondary metabolite dimethylsulfoniopropionate (DMSP), the precursor of the climate-cooling trace gas dimethyl sulfide (DMS). Surprisingly, little is known about the physiological role of DMSP in anthozoans and the environmental factors that regulate its production. Here, we assessed the potential functional role of DMSP as an antioxidant and determined how future increases in seawater pCO2 may affect DMSP concentrations in the anemone Anemonia viridis along a natural pCO2 gradient at the island of Vulcano, Italy. There was no significant difference in zooxanthellae genotype and characteristics (density of zooxanthellae, and chlorophyll a) as well as protein concentrations between anemones from three stations along the gradient, V1 (3232 μatm CO2), V2 (682 μatm) and control (463 μatm), which indicated that A. viridis can acclimate to various seawater pCO2. In contrast, DMSP concentrations in anemones from stations V1 (33.23 ± 8.30 fmol cell(-1)) and V2 (34.78 ± 8.69 fmol cell(-1)) were about 35% lower than concentrations in tentacles from the control station (51.85 ± 12.96 fmol cell(-1)). Furthermore, low tissue concentrations of DMSP coincided with low activities of the antioxidant enzyme superoxide dismutase (SOD). Superoxide dismutase activity for both host (7.84 ± 1.37 U·mg(-1) protein) and zooxanthellae (2.84 ± 0.41 U·mg(-1) protein) at V1 was 40% lower than at the control station (host: 13.19 ± 1.42; zooxanthellae: 4.72 ± 0.57 U·mg(-1) protein). Our results provide insight into coastal DMSP production under predicted environmental change and support the function of DMSP as an antioxidant in symbiotic anthozoans

Microalgae for municipal wastewater nutrient remediation: mechanisms, reactors and outlook for tertiary treatment

This review explores the use of microalgae for nutrient removal in municipal wastewater treatment, considering recent improvements in the understanding of removal mechanisms and developments of both suspended and non-suspended systems. Nutrient removal is associated to both direct and indirect uptake, with the former associated to the biomass concentration and growth environment (reactor). Importantly, direct uptake is influenced by the Nitrogen:Phosphorus content in both the cells and the surrounding wastewater, with opposite trends observed for N and P. Comparison of suspended and non-suspended systems revealed that whilst all were capable of achieving high levels of nutrient removal, only non-suspended immobilized systems could do so with reduced hydraulic retention times of less than 1 day. As microalgae are photosynthetic organisms, the metabolic processes associated with nutrient assimilation are driven by light. Optimization of light delivery remains a key area of development with examples of improved mixing in suspended systems and the use of pulsating lights to enhance light utilization and reduce costs. Recent data provide increased confidence in the use of microalgae for nutrient removal in municipal wastewater treatment, enabling effluent discharges below 1 mg L−1 to be met whilst generating added value in terms of bioproducts for energy production or nutrient recovery. Ultimately, the review suggests that future research should focus on non-suspended systems and the determination of the added value potential. In so doing, it is predicted that microalgae systems will be significant in the delivery of the circular economy

SPECTRAL PROPERTIES OF MICROWAVE-POWERED SULFUR LAMPS IN COMPARISON TO SUNLIGHT AND HIGH PRESSURE SODIUM/METAL HALIDE LAMPS

The spectral properties of 3.4kW microwave-powered sulfur (MPS) lamps were compared with sunlight and with a combination of high-pressure sodium (HPS) and metal halide (MH) lamps. Photosynthetic photon flux (PPF) levels at 1.2m from the MPS lamps (half and full power) and the HPS/MH lamps were 565, 1650, and 875μmol m^<-2>s^<-1>, respectively, versus 2000μmol m^<-2>s^<-1> for sunlight. The percent of spectral irradiance from bare MPS lamps operated at full power was comparable to that of sunlight in the 400-500nm (blue) and 600-700nm (red) regions but was 60% higher in the 500-600nm (yellow) region. On a percent distribution basis, HPS/MH lamps had 50% less blue, nearly 25% more red, and twice as much yellow irradiance as sunlight. On a percent basis, MPS and HPS/MH lamps emitted one third to one half as much 700-792nm (far-red) irradiance as sunlight. At half power, there was a significant shift in spectral output of the MPS lamps from the red to the blue region. Measurements taken with a pyranometer and a pyrgeometer indicate that the biggest difference between MPS and HPS/MH lamps was in the 0.8 to 3.0μm (near infrared, NIR) region; MPS lamps emitted one quarter as much NIR as HPS/MH lamps or the sun on a normalized basis (Jμmol^<-1>). There was no appreciable difference in far IR (3 to 50μm) between half power MPS and HPS/MH lamps, while at full power, MPS lamps had only one half as much far IR. Based on their spectral characteristics and high PPF, MPS lamps should provide an excellent source of radiant energy for use in plant growth chambers