Ecophysiology of coral reef primary producers across an upwelling gradient in the tropical central Pacific

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Johnson, M. D., Fox, M. D., Kelly, E. L. A., Zgliczynski, B. J., Sandin, S. A., & Smith, J. E. Ecophysiology of coral reef primary producers across an upwelling gradient in the tropical central Pacific. Plos One, 15(2), (2020): e0228448, doi:10.1371/journal.pone.0228448.Upwelling is an important source of inorganic nutrients in marine systems, yet little is known about how gradients in upwelling affect primary producers on coral reefs. The Southern Line Islands span a natural gradient of inorganic nutrient concentrations across the equatorial upwelling region in the central Pacific. We used this gradient to test the hypothesis that benthic autotroph ecophysiology is enhanced on nutrient-enriched reefs. We measured metabolism and photophysiology of common benthic taxa, including the algae Porolithon, Avrainvillea, and Halimeda, and the corals Pocillopora and Montipora. We found that temperature (27.2–28.7°C) was inversely related to dissolved inorganic nitrogen (0.46–4.63 μM) and surface chlorophyll a concentrations (0.108–0.147 mg m-3), which increased near the equator. Contrary to our prediction, ecophysiology did not consistently track these patterns in all taxa. Though metabolic rates were generally variable, Porolithon and Avrainvillea photosynthesis was highest at the most productive and equatorial island (northernmost). Porolithon photosynthetic rates also generally increased with proximity to the equator. Photophysiology (maximum quantum yield) increased near the equator and was highest at northern islands in all taxa. Photosynthetic pigments also were variable, but chlorophyll a and carotenoids in Avrainvillea and Montipora were highest at the northern islands. Phycobilin pigments of Porolithon responded most consistently across the upwelling gradient, with higher phycoerythrin concentrations closer to the equator. Our findings demonstrate that the effects of in situ nutrient enrichment on benthic autotrophs may be more complex than laboratory experiments indicate. While upwelling is an important feature in some reef ecosystems, ancillary factors may regulate the associated consequences of nutrient enrichment on benthic reef organisms.This work was supported by funding from the Moore Family Foundation, the Gordon and Betty Moore Foundation, the Scripps family, and anonymous donors. The funders had no role in study design, data collection and analysis, or preparation of the manuscript

Otimização de crescimento e fotofisiologia de duas estirpes de Arthrospira platensis

Arthrospira platensis is a spiral and filamentous cyanobacteria, popularly known as Spirulina, naturally present in highly alkaline lakes. With high nutritional value, it is applied in supplements for human and animal food, being valued for its high protein content (about 60%), antioxidant and anti-inflammatory properties and the presence of pigments such as phycocyanin and β-carotenes, as well as vitamin B12 and omega 3. Due to the growing interest and popularization by the wellness industry, it is industrially produced on an ever-increasing scale. The testing of the cultivation conditions used by the industry, as well as their improvement, with practical applicability is, therefore, of great relevance. In the present study, the evolution of growth and photophysiology of two strains of A. platensis (Chad and UTEX LB2340) is tested with different salinities and temperatures, with the main goal of improving its growth conditions. Based on standard growth conditions (“Spirulina medium”, 35°C, salinity 15 and high light intensity), one of the strains (Chad) was subjected to a test of salinities of 15 (control), 25 and 35, as well as industrial culture medium. Both strains were subjected to an acute temperature test, in a range of 5 to 65°C, in order to assess their photosynthetic response. Growth curves were determined through optical density and assessment of chlorophyll ɑ content, as well as assessment of photophysiological responses using modeled pulse fluorometry. The results demonstrate that the species under study prefer laboratory growth conditions, however, there is potential to produce in salt water, since it shows photosynthetic efficiency when subjected to salinities of 25 and 35. The industrial environment proved to be the least promising in terms of photophysiological response and amount of pigment. Regarding the temperature test, both strains of A. platensis showed a clear preference for values above 35°C, established as optimal by the literature, reaching the maximum photosynthetic efficiency (determined by the parameter “relative electron transport rate”), at 50 and 55°C, respectively for strain UTEX2340 and “Chad”. A test based on the PCR methodology was also carried out to identify the two strains, the results of which are preliminary.Arthrospira platensis é uma cianobactéria helicoidal e filamentosa, popularmente conhecida como Spirulina, naturalmente presente em lagos altamente alcalinos. Com alto valor nutricional, é aplicada em suplementos para alimentação humana e animal, sendo valorizada pelo elevado teor em proteína (cerca de 60%), propriedades antioxidantes e anti-inflamatórias e presença de pigmentos como ficocianina e β-carotenos, bem como vitamina B12 e ómega-3. Devido ao crescente interesse e popularização pela indústria do bem-estar, é industrialmente produzida numa escala cada vez maior. A testagem das condições de cultivo utilizadas pela indústria, bem como o seu aprimoramento, com aplicabilidade prática é, portanto, de grande relevância. No presente estudo, a evolução do crescimento e fotofisiologia de duas estirpes de A. platensis (Chad e UTEX LB2340) é testada com diferentes salinidades e temperaturas, tendo como objetivo principal o melhoramento das condições de cultivo. Tendo como base as condições de crescimento padrão (“Spirulina medium”, 35°C, salinidade 15 e elevada intensidade luminosa), uma das estirpes (Chad) foi submetida a um teste de salinidades de 15 (controlo), 25 e 35, bem como a meio de cultura industrial. Ambas as estirpes foram sujeitas a um teste agudo de temperatura, num espetro de 5 a 65°C, de forma a avaliar a sua resposta fotossintética. Foram determinadas curvas de crescimento através de densidade ótica e avaliação do teor de clorofila, bem como avaliação de respostas fotofisiológicas recorrendo a fluorometria de pulso modelado. Os resultados demonstram que a espécie em estudo prefere meio laboratorial, no entanto, demonstra potencial para ser produzida em água salgada, uma vez que evidencia eficiência fotossintética quando sujeita a salinidades de 25 e 35. O meio industrial mostrou ser o menos promissor em termos de resposta fotofisiológica e quantidade de pigmento. Em relação ao teste de temperatura, ambas as estirpes de A. platensis, demonstraram uma clara preferência por valores acima dos 35°C, estabelecidos como ótimos pela literatura, atingindo o máximo de eficácia fotossintética (determinada pelo parâmetro “taxa relativa de transporte de eletrões”), aos 50 e 55°C, respetivamente para a estirpe UTEX2340 e “Chad”. Foi ainda realizado um teste baseado na metodologia de PCR, para identificação das duas estirpes, cujos resultados são preliminares.Mestrado em Biologia Marinha Aplicad

Response of Phytoplankton Photophysiology to Varying Environmental Conditions in the Sub-Antarctic and Polar Frontal Zone

Climate-driven changes are expected to alter the hydrography of the Sub-Antarctic Zone (SAZ) and Polar Frontal Zone (PFZ) south of Australia, in which distinct regional environments are believed to be responsible for the differences in phytoplankton biomass in these regions. Here, we report how the dynamic influences of light, iron and temperature, which are responsible for the photophysiological differences between phytoplankton in the SAZ and PFZ, contribute to the biomass differences in these regions. High effective photochemical efficiency of photosystem II (F 0 q/F 0 mw0.4), maximum photosynthesis rate (PB max), light-saturation intensity (Ek), maximum rate of photosynthetic electron transport (1/tPSII), and low photoprotective pigment concentrations observed in the SAZ correspond to high chlorophyll a and iron concentrations. In contrast, phytoplankton in the PFZ exhibits low F 0 q/F 0 m (* 0.2) and high concentrations of photoprotective pigments under low light environment. Strong negative relationships between iron, temperature, and photoprotective pigments demonstrate that cells were producing more photoprotective pigments under low temperature and iron conditions, and are responsible for the low biomass and low productivity measured in the PFZ. As warming and enhanced iron input is expected in this region, this could probably increase phytoplankton photosynthesis in this region. However, complex interactions between the biogeochemical processes (e.g. stratification caused by warming could prevent mixing of nutrients), which control phytoplankton biomass and productivity, remain uncertain

The physiological response of seven strains of picophytoplankton to light, and its representation in a dynamic photosynthesis model

Picophytoplankton dominate the phytoplankton community in wide ocean areas and are considered efficient in the acquisition of light compared to other phytoplankton groups. To quantify their photophysiological parameters we use 3 strains of picoprokaryotes and 4 strains of picoeukaryotes. We measure the acclimated response of the exponential growth rates and chlorophyll a to carbon ratios, as well as the instantaneous response of photosynthesis rates at 5-7 light intensities. We then use a dynamic photosynthesis model (Geider, MacIntyre, and Kana 1997) and extend it with a photoinhibition term. We derive five photophysiological parameters: the maximum rate of photosynthesis (PCm), the affinity to light (αchl), the photoinhibition term (βchl), the respiration rate (resp), and the maximum chlorophyll a to carbon ratio (θmax). We show that PCm is significantly lower for picoprokaryotes than for picoeukaryotes and increases significantly with increasing cell size. In turn, αchl decreases significantly with increasing maximum growth rate (µmax). The latter finding is contrary to a previously reported relationship for phytoplankton, but agrees with theoretical assumptions based on size. The higher efficiency in light acquisition gives picoprokaryotes an advantage in light limited environments at the expense of their maximum growth rate. In addition, our results indicate that the accumulation of long-term damage through photoinhibition during acclimation is not well represented by the dynamic photosynthesis model. Hence, we would recommend to distinguish between the effects of irreversible damage (on a time scale of days) on growth rates and of reversible damage (on a time scale of minutes) on photosynthesis rates

Photophysiological and light absorption properties of phytoplankton communities in the river-dominated margin of the northern Gulf of Mexico

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Stratospheric measurement requirements and satellite-borne remote sensing capabilities

The capabilities of specific NASA remote sensing systems to provide appropriate measurements of stratospheric parameters for potential user needs were assessed. This was used to evaluate the capabilities of the remote sensing systems to perform global monitoring of the stratosphere. The following conclusions were reached: (1) The performance of current remote stratospheric sensors, in some cases, compares quite well with identified measurement requirements. Their ability to measure other species has not been demonstrated. (2) None of the current, in-situ methods have the capability to satisfy the requirements for global monitoring and the temporal constraints derived from the users needs portion of the study. (3) Existing, non-remote techniques will continue to play an important role in stratospheric investigations for both corroboration of remotely collected data and in the evolutionary development of future remote sensors