Enriched Seawater Research Articles

Plantlet Regeneration from Callus Cultures of Kappaphycus alvarezii for Cultivation in Coastal Waters at Myeik Archipelago, Myanmar.

<b>Background and Objective:</b> The cultivation of <i>Kappaphycus alvarezii</i>, the most economically valuable rhodophyte seaweed species, began in Myanmar in 2004, primarily on islands in the Myeik Archipelago. Since <i>K. alvarezii</i> is not native to Myanmar, it was initially imported from the Philippines and Indonesia. This study aimed to develop a tissue culture procedure for the generation of <i>K. alvarezii</i> plantlets to ensure a continuous supply of seaweed for commercial farming in the coastal waters of Myanmar. <b>Materials and Methods:</b> Specimens of <i>K. alvarezii</i>, two-month-old, were procured in the Myeik Archipelago, Myanmar. After being cleared epiphytes and clinging materials, the specimens were placed in glass aquarium tanks with circulating seawater. Axenic explant culture was established using 1% povidone-iodine for 1 min and a 1% antibiotic mixture for 24 hrs. Plant growth regulators, 6-benzyl aminopurine (BAP) and indole 3 acetic acid (IAA) were supplemented in solid Provasoli's enriched seawater (PES) media to induce callus formation and somatic embryogenesis. <b>Results:</b> The optimal culture conditions were incubation at 22-25°C under cool-white fluorescent-light (15-20 μmol photons/m<sup>2</sup>/sec) with a 12:12 hrs light and dark cycle. Water quality during the culturing process was maintained at a pH of 8 and salinity of 30 PSU. The tissue-cultured <i>K. alvarezii</i> plantlets exhibited an average daily growth rate of 9.70±0.25% over the growth period. <b>Conclusion:</b> Therefore, plantlet regeneration from <i>K. alvarezii</i> callus cultures can be utilized as seedlings for revenue-generating cultivation along the Myanmar coastline.

Establishment of Effective Callus Induction in the Economically Important Brown Seaweed Ecklonia cava

The edible brown seaweed, Ecklonia cava, is highly valued for its bioactive compounds, and is widely used in food supplements and functional foods. The increasing demand for this seaweed in the food industry emphasizes the necessity for sustainable cultivation practices. This study focused on inducing callus in the meristem and stipe of E. cava using different culture media: Provasoli’s enriched seawater medium (PESI), enriched artificial seawater medium (ESAW), artificial enriched seawater medium (ASP2), or Von Stosch’s enriched seawater medium (VS). Various abiotic stress factors (photoperiod, agar concentration, and temperature), growth regulators, carbon sources, polyamines, and plasma treatments were explored for their impact on callus induction. Both stipe and meristem explants developed callus within three to six weeks across all media except ASP2. Callus development was favored at temperatures between 8 to 13 °C and in the absence of light. Stipe explants showed a higher callus induction rate (up to 65.59 ± 6.24%) compared to meristem (up to 57.53 ± 8.32%). Meristem explants showed optimal callus induction in PESI medium with a low concentration of indole-3-acetic acid (IAA; 40.93 ± 8.65%). However, higher concentrations of IAA and 1-naphthaleneacetic acid (NAA) reduced meristem callus induction. Stipe showed high induced-callus (up to 50.37 ± 5.17%) in PESI medium with low concentrations of IAA, NAA, and 6-benzylaminopurine (BAP). Both stipe and meristem explants induced largest callus at 2% sucrose, but higher carbon source concentrations reduced callus induction. Spermine (Spm) at 1 µM resulted in high induced calluses; however, increasing Spm concentrations decreased callus induction. This tissue culture technique not only supports mass cultivation of E. cava, but also holds potential for extending to other seaweed species, contributing to the sustainability of seaweed stocks for the food industry.

Study of copper corrosion via extracellular electron transfer by nitrate reducing Halomonas titanicae

The microbiologically influenced corrosion (MIC) of copper via extracellular electron transfer (EET) caused by Halomonas titanicae was investigated using two different methods. Copper corrosion in enriched seawater was accelerated by H. titanicae and was further promoted by riboflavin (RF), an electron mediator that can accelerate EET. Within minutes of 20 ppm RF injection, the copper corrosion started to increase. The copper weight loss for 100% carbon source reduction was 1.4 times that of 0% carbon source reduction. The RF injection data together with carbon starvation data indicate that H. titanicae utilized elemental copper as an electron source to cause EET-MIC.

Electrochemical investigation of the “double-edged” effect of low-dose biocide and exogenous electron shuttle on microbial corrosion behavior of carbon steel and copper in enriched seawater

The microbiologically influenced corrosion (MIC) behavior of carbon steel and copper induced by SRB was investigated by low levels of the biocide tetrakis hydroxymethyl phosphonium sulphate (THPS) and the environmental electron shuttle riboflavin in early incubation and harsh conditions. After 7 days of incubation, riboflavin weakened the inhibition for SRB by THPS in the carbon steel system, but did not apply to the copper. Thirty ppm THPS inhibited planktonic cell proliferation, but still formed visual biofilms on carbon steel and copper surfaces. In the co-existence of THPS and riboflavin, higher corrosion rates were obtained in carbon steel, while the MIC of copper was mitigated. For the harsh biotic systems, thirty ppm THPS was ineffective against the SRB-MIC of the harsh systems. Riboflavin was the icing on the cake for carbon steel under this condition, accelerating the SRB-MIC process. Electrochemical noise currents were used to monitor the effects of chemical injection in harsh conditions.

In Situ Capture and Real-Time Enrichment of Marine Chemical Diversity.

Analyzing the chemical composition of seawater to understand its influence on ecosystem functions is a long-lasting challenge due to the inherent complexity and dynamic nature of marine environments. Describing the intricate chemistry of seawater requires optimal in situ sampling. Here is presented a novel underwater hand-held solid-phase extraction device, I-SMEL (In Situ Marine moleculELogger), which aims to concentrate diluted molecules from large volumes of seawater in a delimited zone targeting keystone benthic species. Marine benthic holobionts, such as sponges, can impact the chemical composition of their surroundings possibly through the production and release of their specialized metabolites, hence termed exometabolites (EMs). I-SMEL was deployed in a sponge-dominated Mediterranean ecosystem at a 15 m depth. Untargeted MS-based metabolomics was performed on enriched EM extracts and showed (1) the chemical diversity of enriched seawater metabolites and (2) reproducible recovery and enrichment of specialized sponge EMs such as aerothionin, demethylfurospongin-4, and longamide B methyl ester. These EMs constitute the chemical identity of each targeted species: Aplysina cavernicola, Spongia officinalis, and Agelas oroides, respectively. I-SMEL concentrated sponge EMs from 10 L of water in a 10 min sampling time. The present proof of concept with I-SMEL opens new research perspectives in marine chemical ecology and sets the stage for further sustainable efforts in natural product chemistry.

Microbiologically influenced corrosion inhibition of two marine structural steels caused by Halomonas titanicae in aerobic environments

Corrosion is a global problem, especially in marine environments. The currently popular corrosion mitigation methods have the drawbacks of being costly, susceptible to environmental limitations, or causing environmental contamination. Microbiologically influenced corrosion inhibition (MICI), as a widespread phenomenon, can provide a new strategy utilizing bacteria to control corrosion. This study investigated the MICI mechanism of Halomonas titanicae on two marine structural steels (EH36-low alloy steel (E-LAS) (with copper) and Q235-carbon steel (Q-CS) (without copper)) in aerobic environments. Results show that the corrosion of E-LAS and Q-CS was both inhibited by H. titanicae in an aerobic enriched seawater. It was found that the aerobic respiration mode of H. titanicae was very different from its anaerobic respiration. The former respiration mode significantly reduced the dissolved oxygen (DO) concentrations in the medium. In addition, the DO levels in the biotic medium immersed with the two steels were similar, but the corrosion inhibition degree of E-LAS (22% drop) caused by H. titanicae was weaker than that of Q-CS (55% drop), indicating that the MICI mechanism of H. titanicae goes beyond simply reducing the DO concentration. The number of sessile cells on E-LAS was only 20% of that on Q-CS due to Cu in E-LAS, which led to a thinner extracellular polymeric substance (EPS) film and a corrosion product film with less Fe(II) content. This reduced the Rf values significantly. Therefore, the EPS and corrosion product films caused by H. titanicae aerobic respiration are also important in the corrosion inhibition process.

Natural Antioxidant Potential of Melon Peels for Fortified Foods.

Agricultural and food waste recycling reduces natural resource losses, contributing significantly to the development of new green markets through the creation of redesigned products. In order to cycle valuable molecules, the peels from Italian cantaloupe (Cucumis melo L.) cultivars were studied and successfully characterized for high-added biomolecules to verify their possible exploitation as wealthy biomasses. Peels were investigated for their cell wall-modifying and browning enzymes, as well as for total polyphenols, ortho-diphenols, flavonoids, tannins, and antioxidant properties. The results of the analyses displayed great promise in one of the three cultivars investigated. Later on, a preliminary study using the best peel extract as a dietary supplement was carried out by preparing fortified seawater to enhance its antioxidant power. The effects of storage time (60 days) were examined at two temperatures through the determination of the stability of the polyphenol content. The kinetic parameters of degradation were also calculated. The "enriched sea water" retained great antioxidant activity in refrigerated conditions, demonstrating that there is good potential for melon by-products to add their natural compounds for food fortification. These findings may provide valuable data for scale-up, from the lab to the pilot or industrial application.

Neutral Spores—An Easier Way to Cultivate Pyropia leucosticta (Thuret) Neefus & J.Brodie, 2011 (Bangiales, Rhodophyta) along the Romanian Black Sea Shore

Macroalgal cultures are currently of great interest worldwide. Although along the Romanian Black Sea coast, there is no tradition in this sense, currently, a major interest in developing this direction exists, taking into consideration that the overexploitation of wild seaweed resources involves the disturbance of the marine environment, with implications that can sometimes be irreversible. Porphyra and Pyropia species (also known as nori algae) are considered the world’s most valuable mariculture algal products due to their high nutritional value and multiple active principles, considered unique representatives of marine algae. Considering these aspects, attention was focused on the only nori species from the Romanian Black Sea coast, namely, Pyropia leucosticta. The species was cultivated in controlled laboratory conditions for 5.5 months by manipulating its reproductive elements. The aim was to establish a simple, low-cost method by avoiding the complicated conchocelis phase of the species; therefore, reproduction and further species development were achieved by collecting the released neutral spores and isolating them in culture vessels, ensuring, at the same time, proper nutrient conditions, using sterile enriched seawater and mimicking ambient conditions. At the end of the experiment, specimens of almost 80−90 mm were obtained, making this method suitable for obtaining ex situ P. leucosticta blades on the Romanian Black Sea shore.

Toward developing more sustainable marine biorefineries: A novel ‘sea-thermal’ process for biofuels production from microalgae

This work explores the ‘sea-thermal’ treatment of the aquatic protein-rich microalga Chlorella Vulgaris to produce energy-dense biofuels and value-added, nitrogen-rich liquid products. The impact of the processing conditions (temperature, 200–300 °C; time, 20–180 min) and reaction medium (seawater/(deionized water + seawater) ratio, 0–100 wt%) on the yields and properties of these products has been addressed using a two-level, three-factor (23) Box-Wilson Central Composite, Face Centered (CCF, α: ±1) design. These processing parameters ruled the distribution of the overall reaction products, including gas (1–5 %), biocrude (17–57 %), aqueous product (32–47 %) and hydrochar (3–45 %), and the fuel and chemical properties of these fractions. The calorific values of the hydrochar and biocrude ranged from 2 to 25 MJ/kg and 23 to 32 MJ/kg, respectively. Using low temperatures and/or short reaction times favored biocrude formation, while higher temperatures and/or more prolonged processing times boosted the repolymerization of the biocrude to hydrochar. These transformations depended on the reaction medium, with seawater exerting different influences based on the reaction medium salinity. Diluted seawater promoted the dissolution and depolymerization of polysaccharides and proteins in the alga by disrupting the H-bonding networks within these macromolecules, while enriched seawater media favored the deoxygenation and repolymerization of the biocrude. These variations highlighted the bespoke nature of this ‘sea-thermal’ process to furnish liquid and solid biofuels and/or biochemicals. Process optimization based on the formulae developed from the ANOVA of the experimental data showed that 55–60 wt% of the alga could be converted either to energy-dense (30 MJ/kg) biofuels (36 wt% biocrude, with hydrocarbons and fatty acids/esters in high amount, and 20 wt% hydrochar) at 200 °C for 180 min using enriched seawater (64 wt% seawater) as a solvent or to value-added liquids (a nitrogen-rich (88 %) biocrude, including abundant fatty amides and N-heterocycles) at 237 °C for 169 min in seawater. These results lay the first stone toward developing more sustainable marine biorefineries using marine-based solvents to valorize marine feedstocks.

Mitigation of carbon steel biocorrosion using a green biocide enhanced by a nature-mimicking anti-biofilm peptide in a flow loop

Biocorrosion, also called microbiologically influenced corrosion (MIC), is a common operational threat to many industrial processes. It threatens carbon steel, stainless steel and many other metals. In the bioprocessing industry, reactor vessels in biomass processing and bioleaching are prone to MIC. MIC is caused by biofilms. The formation and morphology of biofilms can be impacted by fluid flow. Fluid velocity affects biocide distribution and MIC. Thus, assessing the efficacy of a biocide for the mitigation of MIC under flow condition is desired before a field trial. In this work, a benchtop closed flow loop bioreactor design was used to investigate the biocide mitigation of MIC of C1018 carbon steel at 25 °C for 7 days using enriched artificial seawater. An oilfield biofilm consortium was analyzed using metagenomics. The biofilm consortium was grown anaerobically in the flow loop which had a holding vessel for the culture medium and a chamber to hold C1018 carbon steel coupons. Peptide A (codename) was a chemically synthesized cyclic 14-mer (cys-ser-val-pro-tyr-asp-tyr-asn-trp-tyr-ser-asn-trp-cys) with its core 12-mer sequence originated from a biofilm dispersing protein secreted by a sea anemone which possesses a biofilm-free exterior. It was used as a biocide enhancer. The combination of 50 ppm (w/w) THPS (tetrakis hydroxymethyl phosphonium sulfate) biocide + 100 nM (180 ppb by mass) Peptide A resulted in extra 1-log reduction in the sulfate reducing bacteria (SRB) sessile cell count and the acid producing bacteria (APB) sessile cell count compared to 50 ppm THPS alone treatment. Furthermore, with the enhancement of 100 nM Peptide A, extra 44% reduction in weight loss and 36% abatement in corrosion pit depth were achieved compared to 50 ppm THPS alone treatment.Graphical

Growth performance of brown-golden marine microalga, Isochrysis sp., cultivated in alternative algal culture media

The present study aimed to evaluate the suitability of introduced algal culture media as an alternative to the general enriched seawater media in the laboratory cultivation of Isochrysis sp., a marine microalga commonly cultivated for aquaculture purposes. Isochrysis sp. was established into culture in three replications using three experimental algal culture media (Walne’s medium as a control, China-contributed culture medium (CCM) and CCM supplemented with vitamins (CCM + Vit)). The experiment was performed with a continuous illumination for a period of seven days at 25±1°C. The effect of introduced algal culture media (CCM and CCM + Vit) on the growth performance of Isochrysis sp. was highlighted. CCM demonstrated promising results for the cultivation of Isochrysis sp. A maximum cell density of 9.16×106 ± 5.40×105 cells mL-1, which corresponded to an instantaneous growth rate (r) of 0.21 cell day-1 and a doubling time (T2) of 3.29 days, was observed in Isochrysis sp. cultivated in CCM. In view of its potential and reduced preparation labour, CCM may be recommended as an alternative to the general enriched seawater media in the cultivation of Isochrysis sp. in laboratories with basic facility as well as small- and medium-scale aquaculture hatcheries.

The Brown Algae Saccharina japonica and Sargassum horneri Exhibit Species-Specific Responses to Synergistic Stress of Ocean Acidification and Eutrophication

Ocean acidification and eutrophication are two important environmental stressors. They inevitably impact marine macroalgae, and hence the coastal ecosystem of China. Saccharina japonica, as the main culture species in China, is suffering the harmful golden tide caused by Sargassum horneri. However, it remains unclear whether the detrimental effects of S. horneri on S. japonica cultivation become more severe in future acidified and eutrophic scenario. In this study, we respectively investigated the effects of pCO2 (400 µatm and 1000 µatm) and nutrients (non-enriched and enriched seawater) on the growth, photosynthesis, respiration, chlorophyll contents, and tissue nitrogen of S. japonica and S. horneri. Results indicated that enrichment of nutrients contributed S. horneri to utilize HCO3−. The carbon acquisition pathway shifted from HCO3− to CO2 in S. japonica, while S. horneri remained using HCO3− regulated by nutrient enrichment. S. horneri exhibited better photosynthetic traits than S. japonica, with a higher level of net photosynthetic rate and chlorophyll contents at elevated pCO2 and enriched nutrients. Tissue nitrogen also accumulated richly in the thalli of S. horneri under higher pCO2 and nutrients. Significant enhancement in growth was only detected in S. horneri under synergistic stress. Together, S. horneri showed competitive dominance in current study. These findings suggest that increasing risk of golden tide in acidified and eutrophic ocean can most likely result in great damage to S. japonica cultivation.

Cultivating marine macroalgae in CO2-enriched seawater: A bio-economic approach

By the end of the current century atmospheric CO2 concentration may reach 1000 ppm, more than twice the present level set at ca. 400 ppm. Marine macroalgae (seaweeds) contribute to global primary production and by taking up CO2 they may ameliorate and regulate global climate change. Seaweeds also have direct and indirect economic importance by providing food and bioactive compounds for human benefit. Nonetheless, all these benefits could be jeopardized by the ongoing pressures, both local and global, on marine environments. In this study we examine the effects of dissolved CO2 and seasonal seawater temperature on the growth rates (measured weekly changes in biomass and expressed on a daily basis) of two model species, Ulva rigida (Chlorophyta) and Gracilaria conferta (Rhodophyta), which are common in the intertidal zone of the Israeli Mediterranean Sea, and cultivated by the local seaweed industry. The seaweeds were grown in land-based 40 L fiberglass tanks fertilized with sufficient N and P, supplied with running seawater and continuous air bubbling to keep equal exposure of the seaweeds to nutrients and light. The tanks were also provided with aeration with regular air (ambient CO2, ~ 400 ppm) or CO2-enriched air (~780 ppm). Seaweeds exposed to CO2–enriched seawater grew faster, 32.5 and 8.5% growth per day for U. rigida and G. conferta, respectively. Following calculations of productivity rates, market price, and input cost, we estimate production and show a quadratic production function with respect to temperature for each CO2 concentration. Thus, there is an optimal temperature that maximizes seaweed output. Based on the production function estimates and using market prices, maximal short-run profits were obtained at ca. 22.5 °C and 27.5 °C for U. rigida and G. conferta, respectively. These results may provide useful information for seaweed growers on what and where to grow seasonally, and how farming activities should adapt to external changes in temperature and CO2 concentration.

Efecto del fotoperiodo y el uso de un nutriente foliar comercial en el crecimiento (Biomasa) de Pyropia sp. CHI “Cochayuyo” bajo condiciones controladas de cultivo

In order to determine the effect of photoperiod and the addition of commercial foliar nutrient at different concentrations in the biomass increasing of Pyropia sp. CHI, gametophytic individuals were collected in Santa Elena beach, Paracas - Pisco and transferred to Applied Biology Laboratory of Universidad Nacional Agraria La Molina. The thalli were divided into groups of 1,0 ± 0,02 g of initial biomass and placed in flasks with enriched sea water with three different concentrations of Bayfolan® commercial foliar nutrient (0,1 ml/L; 0,05 m/L; and 0,025 ml/L) and a control treatment (0 ml/L) against two photoperiod conditions: long day (DL) (L/O = 18:6) and short day (DC) (L/O = 6:18). Biomass (wet weight) and growth rate (g/week) were evaluated weekly during six weeks. The results have demonstrated the effect of nutrient addition in biomass increase of Pyropia sp. CHI where all treatments with added nutrient, for both DC and DL, obtained significantly higher growth rates (p <0,05) than treatment without nutrient addition (0 ml/L). Likewise, a higher biomass was obtained for DL condition with 1,53 g (0 m/L); 2,98 g (0,025 ml/L); 3,28 g (0,05 ml/L) and 3,57 g (0,1 ml/L) unlike that obtained in DC condition with 1,42 g (0 ml/L); 2,79 g (0,025 ml/L); 2,66 g (0,05 ml/L) and 2,65 g (0,1 ml/L) (p ><0,05).

Long-term Culture Characteristics of Sterile Ulva spp. (Chlorophyta)

Sterile mutants of green algae in the genus Ulva have the potential to grow stably and are expected to be a suitable food or feed resource containing various nutrients, such as proteins and minerals. In this study, we isolated U. lactuca and U. pertusa from Tokyo Bay and Imari Bay, respectively, in Japan and evaluated their growth rates using a model reactor at Imari. The newly isolated U. lactuca had a growth rate of approximately 11.4 g-dry·m−2·d−1, which is estimated to be seven times greater than the rice yield in paddy fields, while repeatedly cultured U. lactuca had a growth rate of 8.1 g-dry·m−2·d−1. We also demonstrated that this species could be produced in subculture. Heavy metal analysis showed that after culture production, As, Cr, Pb, and Zn were present at concentrations of 0.1 ppm or less and Cd and Hg were below the detection limit for both Ulva species, indicating that long-term cultured sterile Ulva species have almost no accumulation of heavy metals and so would meet safety requirements for use in foods and feeds. Based on these findings, we designed a new type of efficient production system for sterile mutant Ulva spp. using enriched seawater.

Differential methods of cell lysis for protein profiling of Alexandrium sp. using 2D gel electrophoresis

Introduction: Protein profiling of harmful algae is an ongoing study where the latest analysis was conducted on A. minutum. It is a fundamental study where the protein expression of targeted species can be used to understand the biochemical pathway of selected proteins. The Malaysia Alexandrium spp. has the potential to cause massive blooming that brings harm to the aquatic ecosystem. Methods: In this experiment three methods of cell lysis were tested against A. leei isolated from Malaysian waters. Results: The Axenic culture of the sample was established in enriched seawater media (ESDK) with 12 hours of light and 12 hours of dark conditions. The sample was extracted during exponential phase (day 18) where the same amount of cells was collected via centrifugation. The same buffer was used for each technique of cell lysis in order to get the best protein profiles in terms of a band or spot intensity and number. The cells of A. leei were lysed using sonication in the ice-cold water bath, sonication with probe and freeze-thawing followed by sonication in iced bath is the best method of protein extraction. Conclusions: Nevertheless, it can be concluded that the qualitative analysis using SDS-PAGE and 2D gel electrophoresis could be best method and the freeze thawing mode of cell lysis produced an excellent result among others as the protein spots produced were precise and less streaking were observed.

Diverse fractionation patterns of Rare Earth Elements in deep fracture groundwater in the Baltic Shield – Progress from utilisation of Diffusive Gradients in Thin-films (DGT) at the Äspö Hard Rock Laboratory

Rare earth elements (REEs) were studied in groundwater in fractures at depths between 144 m and 450 m in Proterozoic granitoids on the Baltic Shield at a coastal site in south eastern Sweden (Äspö Hard Rock Laboratory). A specially designed device was used to sample the groundwater under in situ high pressure and low redox conditions. The REEs were measured via both diffusive gradients in thin-films (DGT) samplers after approximately three-week deployment times, and after conventional filtration (0.45 µm membrane filters). The concentrations of REEDGT were lower than the REE0.45µm concentrations in all 14 studied groundwaters. This is explained by development of a diffuse boundary layer (DBL) in the solution at the DGTs caused by the low flow, and in some of the groundwaters additionally by the presence of organically complexed REE that diffuse slowly in the diffusive gel of the DGT. Among the 14 studied groundwaters there was a huge range in REEDGT-fractionation patterns, ranging from enrichment to a nearly three-order-of-magnitude depletion of the heavy REEs (HREEs), despite a relatively homogenous bedrock (granitoids). The HREE enrichment is explained by preservation of the fractionation signature as HREE enriched sea water intruded and flowed through the fractures, supported by the high proportion of modelled REE fulvic-acid complexes in these waters. The strong HREE depletion, which occurred in saline groundwater, was ascribed to an advanced REE equilibrium between the groundwater and primary and/or secondary minerals and the pore water in the bedrock. Yet other groundwaters had flat or moderately HREE depleted patterns, which in some cases may have been caused by mixing of small portions of surficial waters with saline groundwater.

Effects of UV Radiation on Photosynthesis, Antioxidant Capacity and the Accumulation of Bioactive Compounds in Gracilariopsis longissima, Hydropuntia cornea and Halopithys incurva (Rhodophyta).

The red macroalgae Hydropuntia cornea, Gracilariopsis longissima and Halopithys incurva were cultured for 14d under laboratory conditions, in enriched seawater with a high nutrient content (N-NH4+ and P-PO43- ) and two radiation regimes: PAR (400-700nm) and PAB (280-700nm). The UV radiation effects under high availability of nutrients on growth, photosynthetic pigments (chlorophyll a, carotenoids and phycobiliproteins), photosynthetic activity and biochemical composition were studied. Maximum quantum yield (Fv /Fm ) was not significantly different among the PAR and PAB treatments during the experiment. However, the maximum electronic transport rate (ETRmax ) increased over time, showing the highest values in PAR for H.incurva and H.cornea, whereas for G.longissima it was found in PAB. Photosynthetic efficiency (αETR ) decreased over time in the first two species, but increased in G.longissima. Saturation irradiance (EkETR ) and maximum nonphotochemical quenching (NPQmax ) increased in PAB with time up to 80% and 30%, respectively, indicating a photosynthetic acclimatization like that of sun-type algae. Five MAAs were identified in all species using high performance liquid chromatography (HPLC). The total content of MAAs increased over time, being 30% higher in H.incurva, 40% in G.longissima and 50% in H.cornea in PAB than in the PAR treatment. Finally, the antioxidant activity was also higher in the PAB treatment. All of the species presented an effective mechanism of photoprotection based on the accumulation of photoprotective compounds with antioxidant activity, as well as a high dissipation of excitation energy (high NPQmax ).

Indonesian throughflow controlled the westward extent of the Indo-Pacific Warm Pool during glacial-interglacial intervals

Abstract The tropical atmospheric circulation is strongly influenced by the sea surface temperature (SST) of the warmest region of the world ocean, the Indo-Pacific Warm Pool (IPWP). The effect of recent anomalous Indian Ocean warming on the extent of the IPWP remains uncertain. Past SST records from the tropical Indian Ocean, associated with different temporal boundary conditions, can help shed light on how climate change impacts the IPWP and associated monsoonal processes. Here, we reconstruct the seawater temperature and precipitation changes (from Mg/Ca and δ18O of surface-dwelling planktic foraminifera Globigerinoides ruber) of the last ~184 kyr BP from the westernmost margin of the IPWP. The data is then used to reconstruct the spatial extent and intensity of the IPWP structure as well as its relationship with other regional phenomena. A consistently warmer (>28 °C) central equatorial Pacific Ocean and significantly cooler equatorial western Pacific and the Indian Ocean suggests that the warm pool extent reduced considerably during MIS6 as well as the last glacial interval, leading to a strong La-Nina like condition. The most enriched seawater δ18O (δ18Osw) during MIS6, was in the westernmost IPWP, suggesting weakened precipitation, despite La-Lina like conditions. The westernmost part of the IPWP became warmer than the threshold 28 °C during MIS5e and the early Holocene, suggesting the westward extension of the IPWP. The eastern equatorial Pacific Ocean also warmed considerably during MIS5e, suggesting a weaker Walker Circulation and a stronger El-Nino. The difference in δ18Osw decreased considerably during MIS5e and is attributed to increased precipitation/freshwater runoff in the central equatorial Indian Ocean. The increase in δ18Osw (~1.5‰) between ~55 kyr until the last glacial maximum, in a majority of the Indian Ocean records, suggests progressively weakened precipitation. A majority of the records have a uniform SST anomaly throughout the Holocene. A warmer equatorial Indian Ocean during interglacials suggests a strong modulation of the IPWP extent by the transport of warm water through the Indonesian throughflow region. The large drop in δ18Osw despite the comparable change in SST during the last glacial interval suggests that monsoon forcing has been much stronger in altering the surface hydrography in the Indian Ocean than the central Pacific Ocean.

The influence of Zn and I on growth and desiccation-induced chlorophyll fluorescence quenching of Trebouxia asymmetrica

The composition of the growth medium has a major influence on the physiological properties of microalgae. We have previously shown that addition of the trace elements Zn and I enhances desiccation-induced fluorescence quenching (qdes) in the lichen phycobiont Trebouxia asymmetrica. qdes is likely to be an important factor of the tolerance against drought, as it has a protective function against photoinhibition in the dehydrated state of this poikilohydric organism. The influence of the presence of iodine and/or zinc ions in culture media on growth of T. asymmetrica and its ability to show qdes were investigated. T. asymmetrica was able to grow in seawater and showed enhanced qdes as compared to when grown in the usual Bold’s basal growth medium. While artificial seawater had no effect, addition of Zn and I in the concentrations present in natural seawater enhanced qdes to almost the same level as observed in natural seawater. The presence of Zn and I also increased growth by the factor of almost 2, thus approximating the growth rate reached in enriched seawater. Both effects, enhancement of qdes and of the growth rate were dependent on the simultaneous presence of both elements. Adding only one element at any concentration resulted in no or very little effect on either growth rate or qdes. The mechanism of the action of both elements is unknown. It is possible that the simultaneous presence of I and Zn has a profound effect on the fitness of lichens containing T. asymmetrica in nature.