Iron physiological autecology of the vertically migrating diatoms \u3ci\u3eEthmodiscus\u3c/i\u3e spp. and \u3ci\u3eRhizosolenia\u3c/i\u3e spp. in the Central North Pacific (CNP) gyre

Low Fe availability constrains algal primary production in numerous oceanic provinces. Although not numerically abundant, the diatom microplankton (\u3e 20 micro m) are important contributors to new production in these regions. To better understand the contributions made to new production by diatoms in Fe-depleted waters, this dissertation work addressed the Fe-specific physiological and biochemical autecology of this group. A field component consisted of two research cruises in 2002 and 2003 along a transect at 29 degrees North spanning the eastern half of the Central North Pacific (CNP) gyre, and focused on the vertically migrating bouyant giant diatom genera Rhizosolenia spp. and Ethmodiscus spp. The lab component examined physiological, biochemical and growth responses of large open-ocean and coastal diatom isolates to perturbations of Fe in the growth medium. Whereas mats of Rhizosolenias howed elevated values (ca. 0.61, n = 88) of Fv/Fm, a measure of photochemical energy conversion efficiency, along the easterly transect from Hawaii to San Diego, a clear decline in this parameter measured at locations west of 165 degrees West provided physiological evidence of nutrient limitation. By contrast, cells of Ethmodiscus showed consistently near maximal values of Fv/Fm (ca.0.7, n = 70). The higher Fv/Fmassociated with Ethmodiscus was supported in part by an enhanced Ferredoxin Index (Fd Index), a common biochemical measure for Fe status. By comparison, the Fd Index for Rhizosolenia along the western reaches of the transect was consistently depressed. Cellular Fe quotas of both diatoms rinsed with oxalate, a reagent used to reduce cell surface adsorbed Fe facilitating its removal from the cell surface, demonstrated comparable low Fe:C stoichiometry (means of 5.41 SE 4.76 and 9.21 SE 5.10) (micro mol:mol) for Ethmodiscus and Rhizosolenia, respectively. This was consistent with the presumed low dissolved Fe content of these ultraoligotrophic waters. These cellular Fe quotas represent among the first such measurements for oceanic diatoms. A Fd protein-coding gene (petF) was partially sequenced from Rhizosolenia fallax, an isolate from the CNP gyre. Application of bioinformatics tools validated the cross reactivity of Fd protein with the antibodies used for immunoblotting in this study. This petF gene sequence represents among the first petF gene sequences for open ocean diatom isolates

Chlorophyll–Nutrient Relationships of an Artificial Inland Lagoon Equipped with Seawater Replenishment System in the Northern Red Sea (Gulf of Aqaba)

Data are reported for an inland artificial lagoon (Ayla) to evaluate the impact of the lagoon’s modeled design and water replenishment system on its water quality and the coastal ecosystem. This study focused on Ayla’s upper lagoon (UL) only, due to its isolation from the two other lagoons and the ambient seawater in the Gulf of Aqaba (GoA). Nutrient measurements (nitrite, nitrate, ammonium, phosphate, and silicate) in addition to Chlorophyll a (Chl a) data were collected between July 2012 and June 2013. Chl a values in the UL were not significantly different from ambient seawater in the GoA, and the UL did not show seasonal differences (p = 0.456). Significant variability for nitrite was observed in the UL between spring and summer (p < 0.0001) and between fall and winter (p < 0.0001). Nitrite showed a stronger seasonal effect in the GoA seawater than in the UL (p = 0.056). Phosphorus showed a seasonal effect and remained similar between the UL and GoA. Nutrient stoichiometry showed a Redfield-like nitrogen-to-phosphorus (N:P) ratio for the ambient GoA seawater around the inlet pumping source and an increased N:P ratio inside the UL. This study emphasizes the importance of modeled lagoon design and seawater replenishment system in preventing and inhibiting eutrophication of the lagoon and therefore minimizing contamination in the coastal ecosystem

Preliminary Investigation of Bioaccumulation of Microcystins in Hypereutrophic Irrigation Ponds Case Study – the Jordan Valley

Microcystis blooms and the related toxin known as microcystin-LR (MC-LR) put the safety of human water consumption and global irrigation practices in jeopardy. MC-LR is widely distributed in various environments, including water, sediments, plants, and other aquatic organisms. The use of water-containing microcystins for agricultural purposes may have to be restricted despite the limited availability of clean water resources. Accordingly, the present work aimed to determine the MC-LR concentrations and recognize the environmental parameters that initiate the growth of toxic cyanobacteria and MC-LR occurrence in 20 irrigation ponds in the Jordan Valley area. The irrigation ponds studied were found in a hypereutrophic condition, with high levels of N:P ratio and low transparency. These cause inseparable effects such as cyanobacterial bloom and MC-LR occurrence. The investigated ponds were classified as hypereutrophic according to General Quality Index (GQI), with two different types of algae covering the surface. The first was the Lemna sp. or duckweeds (Family Araceae) which are free-floating masses, and the second was the cyanobacteria algal bloom. Unpaired t-tests were performed and showed that the concentrations of MC-LR in pond water abundant with cyanobacteria algal bloom in September 2021 were significantly higher (P = 0.7906) than in June for the same year (0.3022 ± 0.0444 and 0.1048 ± 0.0171 ppb, respectively). Two methods for extracting MC-LR were used and showed a significant difference in MC-LR concentration in ponds with an abundance of cyanobacteria algal blooms (0.2273 ± 0.0356 ppb) compared to the ponds with an abundance of Lemna sp. or duckweeds collected in June 2021 (0.1048 ± 0.0171 ppb). Despite all of the efforts made by Jordan Valley farmers to prevent or limit the mass growth of cyanobacteria and its consequences for the eutrophication process in their irrigation ponds through the use of fish breading and chemicals such as copper sulfate, this environmental problem is still harming their crops and irrigation methods and requires immediate government assistance

Budget of Primary Production and Dinitrogen Fixation in a Highly Seasonal Red Sea Coral Reef

Biological dinitrogen (N2) fixation (diazotrophy, BNF) relieves marine primary producers of nitrogen (N) limitation in a large part of the world oceans. N concentrations are particularly low in tropical regions where coral reefs are located, and N is therefore a key limiting nutrient for these productive ecosystems. In this context, the importance of diazotrophy for reef productivity is still not resolved, with studies up to now lacking organismal and seasonal resolution. Here, we present a budget of gross primary production (GPP) and BNF for a highly seasonal Red Sea fringing reef, based on ecophysiological and benthic cover measurements combined with geospatial analyses. Benthic GPP varied from 215 to 262 mmol C m−2 reef d−1, with hard corals making the largest contribution (41–76%). Diazotrophy was omnipresent in space and time, and benthic BNF varied from 0.16 to 0.92 mmol N m−2 reef d−1. Planktonic GPP and BNF rates were respectively approximately 60- and 20-fold lower than those of the benthos, emphasizing the importance of the benthic compartment in reef biogeochemical cycling. BNF showed higher sensitivity to seasonality than GPP, implying greater climatic control on reef BNF. Up to about 20% of net reef primary production could be supported by BNF during summer, suggesting a strong biogeochemical coupling between diazotrophy and the reef carbon cycle

Molecular Accounting and Profiling of Human Respiratory Microbial Communities: Toward Precision Medicine by Targeting the Respiratory Microbiome for Disease Diagnosis and Treatment

The wide diversity of microbiota at the genera and species levels across sites and individuals is related to various causes and the observed differences between individuals. Efforts are underway to further understand and characterize the human-associated microbiota and its microbiome. Using 16S rDNA as a genetic marker for bacterial identification improved the detection and profiling of qualitative and quantitative changes within a bacterial population. In this light, this review provides a comprehensive overview of the basic concepts and clinical applications of the respiratory microbiome, alongside an in-depth explanation of the molecular targets and the potential relationship between the respiratory microbiome and respiratory disease pathogenesis. The paucity of robust evidence supporting the correlation between the respiratory microbiome and disease pathogenesis is currently the main challenge for not considering the microbiome as a novel druggable target for therapeutic intervention. Therefore, further studies are needed, especially prospective studies, to identify other drivers of microbiome diversity and to better understand the changes in the lung microbiome along with the potential association with disease and medications. Thus, finding a therapeutic target and unfolding its clinical significance would be crucial

Environmental conditions, nitrogen fixation and gross photosynthesis rates measured in Stylophora pistillata from in the northern Gulf of Aqaba, Red Sea

Tropical corals are often associated with dinitrogen (N2)-fixing bacteria (diazotrophs), and seasonal changes in key environmental parameters, such as dissolved inorganic nitrogen (DIN) availability and seawater temperature, are known to affect N2 fixation in coral-microbial holobionts. Despite, then, such potential for seasonal and depth-related changes in N2 fixation in reef corals, such variation has not yet been investigated. Therefore, this study quantified seasonal (winter vs. summer) N2 fixation rates associated with the reef-building coral Stylophora pistillata collected from depths of 5, 10 and 20 m in the northern Gulf of Aqaba (Red Sea). Findings revealed that corals from all depths exhibited the highest N2 fixation rates during the oligotrophic summer season, when up to 11% of their photo-metabolic nitrogen demand (CPND) could be met by N2 fixation. While N2 fixation remained seasonally stable for deep corals (20 m), it significantly decreased for the shallow corals (5 and 10 m) during the DIN-enriched winter season, accounting for less than 2% of the corals' CPND. This contrasting seasonal response in N2 fixation across corals of different depths could be driven by 1) release rates of coral-derived organic matter, 2) the community composition of the associated diazotrophs, and/or 3) nutrient acquisition by the Symbiodinium community

Contrasting seasonal responses in dinitrogen fixation between shallow and deep-water colonies of the model coral Stylophora pistillata in the northern Red Sea

Tropical corals are often associated with dinitrogen (N-2)-fixing bacteria (diazotrophs), and seasonal changes in key environmental parameters, such as dissolved inorganic nitrogen (DIN) availability and seawater temperature, are known to affect N-2 fixation in coral-microbial holobionts. Despite, then, such potential for seasonal and depth-related changes in N-2 fixation in reef corals, such variation has not yet been investigated. Therefore, this study quantified seasonal (winter vs. summer) N-2 fixation rates associated with the reef-building coral Stylophora pistillata collected from depths of 5, 10 and 20 m in the northern Gulf of Aqaba (Red Sea). Findings revealed that corals from all depths exhibited the highest N-2 fixation rates during the oligotrophic summer season, when up to 11% of their photo-metabolic nitrogen demand (CPND) could be met by N-2 fixation. While N-2 fixation remained seasonally stable for deep corals (20 m), it significantly decreased for the shallow corals (5 and 10 m) during the DIN-enriched winter season, accounting for less than 2% of the corals' CPND. This contrasting seasonal response in N-2 fixation across corals of different depths could be driven by 1) release rates of coral-derived organic matter, 2) the community composition of the associated diazotrophs, and/or 3) nutrient acquisition by the Symbiodinium community