Development of a prototype for submarine communications in shallow waters

The Telecommunications Marine Laboratory (TML) of the University of Cádiz takes part in a research project to study the intertidal sediments of the Bay of Cádiz. The collection of samples from the seabed and the transmission of data to the surface are performed by a Mini Profiler with four channels (MP4), which is supplied by UNISENSE. Each channel processes the samples collected by a single sensor. For power, control, and data transmission, a special wiring that connects the submerged subsystem with the surface subsystem is used. The tension transmitted by the cable to the MP4 structure makes its handling and positioning under water more difficult. This article explains the technological solution developed by the TML to replace some wiring from the MP4. For the prototype, two underwater acoustic modems have been used and an electronic system has been developed based on the Arduino platform, in order to multiplex, digitize, and transmit the data collected by the MP4 sensors, eliminating the need to use wiring. The submerged subsystem has an autonomous power supply by a battery.Peer Reviewe

Kinetics of Indigenous Nitrate Reducing Sulfide Oxidizing Activity in Microaerophilic Wastewater Biofilms

23 páginas.-- 10 figuras.-- 2 tablas.-- 74 referencias.-- Supporting Information: Dataset. in http://dx.doi.org/10.1371/journal.pone.0149096Nitrate decreases sulfide release in wastewater treatment plants (WWTP), but little is known on how it affects the microzonation and kinetics of related microbial processes within the biofilm. The effect of nitrate addition on these properties for sulfate reduction, sulfide oxidation, and oxygen respiration were studied with the use of microelectrodes in microaerophilic wastewater biofilms. Mass balance calaculations and community composition analysis were also performed. At basal WWTP conditions, the biofilm presented a double-layer system. The upper microaerophilic layer (~300 μm) showed low sulfide production (0.31 μmol cm-3 h-1) and oxygen consumption rates (0.01 μmol cm-3 h-1). The anoxic lower layer showed high sulfide production (2.7 μmol cm-3 h-1). Nitrate addition decreased net sulfide production rates, caused by an increase in sulfide oxidation rates (SOR) in the upper layer, rather than an inhibition of sulfate reducing bacteria (SRB). This suggests that the indigenous nitrate reducing-sulfide oxidizing bacteria (NR-SOB) were immediately activated by nitrate. The functional vertical structure of the biofilm changed to a triple-layer system, where the previously upper sulfide-producing layer in the absence of nitrate split into two new layers: 1) an upper sulfide-consuming layer, whose thickness is probably determined by the nitrate penetration depth within the biofilm, and 2) a middle layer producing sulfide at an even higher rate than in the absence of nitrate in some cases. Below these layers, the lower net sulfide-producing layer remained unaffected. Net SOR varied from 0.05 to 0.72 μmol cm-3 h-1 depending on nitrate and sulfate availability. Addition of low nitrate concentrations likely increased sulfate availability within the biofilm and resulted in an increase of both net sulfate reduction and net sulfide oxidation by overcoming sulfate diffusional limitation from the water phase and the strong coupling between SRB and NR-SOB syntrophic relationshipAC was funded by projects P06-RNM-01787, P11-RNM-7199, the PAI group RNM-214 from Consejería de Innovación, Ciencia y Empresa, Junta de Andalucía and CTM2013-43857-R from the Spanish Ministry of Economy and Competitiveness. JMG was funded by the PAI group BIO-288 from Consejería de Innovación, Ciencia y Empresa, Junta de Andalucía. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewe

Microbenthic Net Metabolism Along Intertidal Gradients (Cadiz Bay, SW Spain): Spatio-Temporal Patterns and Environmental Factors

Microphytobenthos (MPB), the photosynthetic primary producing component of microbenthos, shows variable patterns in its biomass distribution along the intertidal gradient as a result of the interactions of factors such as light, tides, temperature, and grazing pressure. These patterns have been studied more extensively in northern European estuaries than southern European coastal systems. Even less information is available regarding temporal changes in MPB primary production rates in these systems. For this reason, we followed the seasonal changes in net production in light and dark respiration rates (determined by oxygen microelectrodes) and MPB biomass (estimated by sediment chlorophyll a) along the intertidal gradient of the inner Cadiz Bay during a year. Sediment cores were collected along two transects (five sampling stations per transect) with distinct sediment granulometry: one muddy [Puerto Real (PR)] and one muddy-sandy transect [San Fernando (SF)]. Our results show that MPB biomass and net production increased seawards reaching their maxima in winter. In contrast to what is observed in northern European systems, the higher solar irradiance and temperatures occurring in summer in southern Spain likely inhibit MPB production. In Cadiz Bay, spatial patterns of MPB biomass and net production depended on season and location due to the environmental heterogeneity observed. Environmental variables, analyzed by principal component analysis (PCA), were used to explain the variability of MPB metabolism by multiple regression. Selected principal component (PC) axes explained 60% of the net production in light and 41% of the dark respiration rates variability in PR, while they only accounted for 25% of the same rates in SF. The differences observed between transects and the variability in the environmental variables explaining them highlight the importance of considering the spatial heterogeneity of our system to estimate the contribution of MPB to the inner Cadiz Bay productivity. In our case, this contribution is significant accounting for up to 49% of the total benthic production of the inner Cadiz Bay intertidal sediments, confirming previous global estimates

Trophic status of a coastal lagoon - marine harbor system: Potential outwelling rates to the Mesoamerican Barrier Reef southern region

Eutrophication is still a serious problem in many coastal areas, including the tropics, where river discharges of nutrients is usually high. The ecological stability and ecosystem services of the Mesoamerican Barrier Reef System (MBRS), the world's second-largest coral reef system, suffer a generalized impact by riverine discharge of sediment and organic and inorganic nutrients, which may lead to coastal eutrophication and a coral-macroalgal phase shift. However, few data exist on the MRBS coastal zone status, particularly in Honduras. Here, two in situ sampling campaigns were carried out (May 2017 and January 2018) in the Alvarado Lagoon and Puerto Cortés Bay (Honduras). Measurements included water column nutrients, chlorophyll-a (Chla), particulate organic and inorganic matter and net community metabolism, completed with satellite images analysis. The lagoon and bay environments are ecologically different systems and present different sensitivities to seasonal changes in precipitation as shown by the multivariate analysis. Nonetheless, net community production and respiration rates were neither different spatially, nor seasonally. In addition, both environments were highly eutrophic as shown by the TRIX index. Thus, the Puerto Cortés system represents an important source of dissolved nutrients and particulate matter to the coastal zone. Even though offshore, water quality, based on estimated outwelling rates from the Puerto Cortés system to the coastal waters of the southern MRBS region, improved considerably, concentrations of Chla and nutrients remained higher than those typically measured in non-polluted coral reefs in the Caribbean region and the suggested threshold values. In situ monitoring and assessment of these aspects are crucial to evaluate the ecological functioning of and threats on the MBRS, and elaborate and implement adequate policies for integrated management given its regional and global importance

Diel patterns of microphytobenthic primary production in intertidal sediments: the role of photoperiod on the vertical migration circadian rhythm

Diel primary production patterns of intertidal microphytobenthos (MPB) have been attributed to short-term physiological changes in the photosynthetic apparatus or to diel changes in the photoautotrophic biomass in the sediment photic layer due to vertical migration. Diel changes in primary production and vertical migration are entrained by external factors like photoperiod and tides. However, the role of photoperiod and tides has not been experimentally separated to date. Here, we performed laboratory experiments with sediment cores kept in immersion, in the absence of tides, with photoperiod or under continuous light. Measurements of net production, made with O-2 microsensors, and of spectral reflectance at the sediment surface showed that, in intertidal sediments, the photoperiod signal was the major driver of the diel patterns of net primary production and sediment oxygen availability through the vertical migration of the MPB photoautotrophic biomass. Vertical migration was controlled by an endogenous circadian rhythm entrained by photoperiod in the absence of tides. The pattern progressively disappeared after 3 days in continuous light but was immediately reset by photoperiod. Even though a potential contribution of a subjective in situ tidal signal cannot be completely discarded, Fourier and cross spectral analysis of temporal patterns indicated that the photosynthetic circadian rhythm was mainly characterized by light/dark migratory cycles

Reduction of net sulfide production rate by nitrate in wastewater bioreactors. Kinetics and changes in the microbial community

15 páginas, 7 figuras, 5 tablas, 44 referencias.-- [email protected] addition stimulated sulfide oxidation by increasing the activity of nitrate-reducing sulfide-oxidizing bacteria (NR-SOB), decreasing the concentration of dissolved H2S in the water phase and, consequently, its release to the atmosphere of a pilot-scale anaerobic bioreactor. The effect of four different concentrations of nitrate (0.12, 0.24, 0.50, and 1.00 mM) was investigated for a period of 3 days in relation to sulfide concentration in two bioreactors set up at Guadalete wastewater treatment plant (Jerez de la Frontera, Spain). Physicochemical variables were measured in water and air, and the activity of bacteria implicated in the sulfur and nitrogen cycles was analyzed in the biofilms and in the water phase of the bioreactors. Biofilms were a net source of sulfide for the water and gas phases (7.22±5.3 μmol s−1) in the absence of nitrate dosing. Addition of nitrate resulted in a quick (within 3 h) decrease of sulfide both in the water and atmospheric phases. Sulfide elimination efficiency in the water phase increased with nitrate concentrations following the Michaelis–Menten kinetics (Ks=0.63 mM NO3 −). The end of nitrate addition resulted in a recovery or increase of initial net sulfide production in about 3 h. Addition of nitrate increased the activity of NR-SOB and decreased the activity of sulfate-reducing bacteria. Results confirmed the role of NR-SOB on hydrogen sulfide consumption coupled with nitrate reduction and sulfate recycling, revealing Sulfurimonas denitrificans and Paracoccus denitrificans as NR-SOB of great importance in this process.We acknowledge the support of the grants P06-RNM-01787, P11-RNM-7199, the PAI groups RNM-214 and BIO-288 from Consejería de Innovación, Ciencia y Empresa, Junta de Andalucía, Spain and CTM2009-10736 from the Ministerio de Innovación y Ciencia, Spain, which include cofinancing from FEDER funds. S. Papaspyrou was funded by a JAE-Doc fellowship (Programa JAE, JAE-Doc109, Spanish National Research Council) and a Marie Curie ERG action (NITRICOS, 235005, European Union).Peer reviewe

Size fractionated phytoplankton biomass and net metabolism along a tropical estuarine gradient

Size structure of phytoplankton determines to a large degree the trophic interactions in oceanic and coastal waters and eventually the destiny of its biomass. Although, tropical estuarine systems are some of the most productive systems worldwide compared to temperate systems, little is known about phytoplankton biomass size fractions, their contribution to net metabolism, or the ecological factors driving phytoplankton size distribution in tropical estuaries. Hence, we measured the size-fractionated biomass and net metabolism of the plankton community along a salinity and nutrient gradient in the Gulf of Nicoya estuary (Costa Rica), during the dry season. Respiration (23.6 mmol O2 m−3 h−1) was highest at the estuary head, whereas maximum net primary production (23.1 mmol O2 m−3 h−1) was observed in the middle of the estuary, coinciding with the chlorophyll a maximum (15.9 mg m−3). Thus, only the middle section of the estuary was net autotrophic (2.9 g C m−2 d−1), with the rest of the estuary being net heterotrophic. Regression analysis identified light availability, and not nutrients, as the principal factor limiting primary production in the estuary due to increased turbidity. The changes in net metabolism along the estuary were also reflected in the phytoplankton's size structure. Although micro- and picophytoplankton were the most productive fractions overall, in the middle section of the estuary nanophytoplankton dominated primary production, chlorophyll, and autotrophic biomass

New Eremophilane-Type Sesquiterpenes from the Marine Sediment-Derived Fungus Emericellopsis maritima BC17 and Their Cytotoxic and Antimicrobial Activities

The fungal strain BC17 was isolated from sediments collected in the intertidal zone of the inner Bay of Cadiz and characterized as Emericellopsis maritima. On the basis of the one strain–many compounds (OSMAC) approach, four new eremophilane-type sesquiterpenes (1–4), together with thirteen known derivatives (5–17) and two reported diketopiperazines (18, 19), were isolated from this strain. The chemical structures and absolute configurations of the new compounds were determined through extensive NMR and HRESIMS spectroscopic studies and ECD calculation. Thirteen of the isolated eremophilanes were examined for cytotoxic and antimicrobial activities. PR toxin (16) exhibited cytotoxic activity against HepG2, MCF-7, A549, A2058, and Mia PaCa-2 human cancer cell lines with IC50 values ranging from 3.75 to 33.44 µM. (+)-Aristolochene (10) exhibited selective activity against the fungal strains Aspergillus fumigatus ATCC46645 and Candida albicans ATCC64124 at 471 µM

A multiproxy study distinguishes environmental change from diagenetic alteration in the recent sedimentary record of the inner Cadiz Bay (SW Spain)

In this study, we reconstruct the recent environmental evolution of the inner Cadiz Bay using sedimentary records reaching back as far as AD 1700. We report lithological descriptions of the sediments and extensive mineralogical and geochemical analyses. An extraction technique that identifies different Fe phases provides an assessment of diagenetic alteration, which allows an estimation of the original organic matter inputs to the inner Cadiz Bay. Downcore variations in Corg/N ratios, δ13Corg and δ15N are related to changes in organic matter sources and the trophic state of the water column. The downcore records of selected trace metals (e.g. Pb, Zn and Cu) are interpreted to reflect changes in heavy metal pollution in the bay, while records of other elements (e.g. Mn and P) are likely overprinted by diagenetic alteration. Major environmental shifts took place during the 20th century, when the population around Cadiz Bay increased exponentially. Increases in sediment accumulation rates, organic matter inputs and heavy metal contents, in parallel with increases in δ13Corg and δ15N over this period, are interpreted as direct effects of the increasing anthropogenic influence in the area. The results of this study suggest that multiproxy approaches and detailed consideration of diagenetic overprinting are required to reconstruct past environmental conditions from coastal sediments