Kinetics of the oxidation of endocrine disruptor nonylphenol by ferrate(VI)

The kinetics of the oxidation of endocrine disruptor nonylphenol (NP) by potassium ferrate(VI) (K₂FeO₄) in water as a function of pH 8.0–10.9 at 25°C is presented. The observed second-order rate constants, k _obs, decrease with an increase in pH 269–32 M^?1 s^?1. The speciation of Fe(VI) (HFeO ₄ ^? and FeO ₄ ^2? ) and NP (NP–OH and NP–O^?) species was used to explain the pH dependence of the k _obs values. At a dose of 10 mg L^?1 (50 μM) K₂FeO₄, the half-life for the removal of NP by Fe(VI), under water treatment conditions, is less than 1 min.     

Change in zooxanthellae and mucocyte tissue density as an adaptive response to environmental stress by the coral, <Emphasis Type="Italic">Montastraea annularis</Emphasis>

Results from controlled in situ experimentation conducted on the leeward reef tract of Curaçao, Netherlands Antilles, indicate that the coral Montastraea annularis exhibits a complex, yet consistent, cellular response to increasing sea surface temperature (SST) and decreasing irradiance. This was determined by simultaneously quantifying and tracking the tissue density of zooxanthellae and mucocytes using a novel technique that integrates the lectin histochemical stain wheat germ agglutinin (WGA) with high-resolution (200 nm) optical epifluorescence microscopy. Coral colonies growing at 6-m water depth (WD) and an irradiance of 100.2 ± 6.5 μmol m^?2 s^?1 were treated with a shading experiment for 11 days that reduced irradiance to 34.9 ± 6.6, 72.0 ± 7.0 and 90.1 ± 4.2 μmol m^?2 s^?1, respectively. While a significant decrease in the density of both zooxanthellae and mucocytes were observed at all shade levels, the largest reduction occurred between the natural non-shaded control (44,298 ± 3,242 zooxanthellae cm^?2; 4,853 ± 346 mucocytes cm^?2) and the highest shading level (13,982 ± 1,961 zooxanthallae cm^?2; 2,544 ± 372.9 mucocytes cm^?2). Colonies were also sampled during a seasonal increase in SST of 1.5°C, where the density of zooxanthellae was significantly lower (from 54,710 ± 1,755 to 34,322 ± 2,894 cells cm^?2) and the density of mucocytes was significantly higher (from 6,100 ± 304 to 29,658 ± 3,937 cells cm^?2). These observations of coral cellular response to environmental change provide evidence to support new hypotheses for coral survival and the complex role played by mucus in feeding, microbial associations and resilience to increasing SST.     

The foraging ecology of coastal bottlenose dolphins based on stable isotope mixing models and behavioural sampling

Understanding trophic interactions is critical for elucidating ecological roles of marine predators. We used behavioural observations and stable isotope mixing models to investigate the feeding ecology of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the lagoon of Mayotte (East Africa). We identified prey during 77 % of 54 observed feeding events, observed in both rainy (61 % of events) and dry (39 %) seasons. Caranx melampygus and Gnathanodon speciosus were involved in 67 % of these events, with Tylosurus crocodilus (20 %) and Mugil cephalus (13 %) also consumed. Mixing models, based on δ¹³C and δ¹⁵N values of skin and blubber (n = 30 samples for both tissues), suggest that behavioural observations are representative of general feeding patterns. Indeed, C. melampygus and T. crocodilus (G. speciosus could not be included in models) were estimated to contribute most to dolphin diets, with mean estimated contributions of 44.6 % (±18.9) and 48.1 % (±19.1) for skin and 73.7 % (±14.9) and 16.9 % (±12.4) for blubber, respectively. Our results highlight the value of two independent methods (stable isotopes and behavioural observations) to assess prey preferences of free-ranging dolphins.     

Measurement of indoor radon concentration and assessment of doses in different districts of Alexandria city, Egypt

The main objective of this study is to assess the health hazard due to the indoor radon. Measurement studies have been carried out in 56 dwellings belonging to 14 residential areas in Alexandria city, Egypt. Results are obtained using the LR-115 (Type II) alpha track detector in “closed-can” geometry. The dosimeters were installed in bedroom, living room, and the kitchens of each house. For intercomparison purpose, dosimeters are installed in basements, ground floor, and first floor. Measured indoor radon concentrations were found to vary from 15 to 132 Bq m^?3. The average radon concentrations in living room, bedrooms, and kitchen in basements were found to vary from to be 39 ± 10, 63 ± 15 and 81 ± 25 Bq m^?3, respectively. In living room, bedrooms, and kitchen, on ground floor, the average radon concentrations were found to be 35 ± 9, 44 ± 6 and 56 ± 10 Bq m^?3, whereas on first floor, the average values are 29 ± 8, 34 ± 7 and 45 ± 8 Bq m^?3, respectively. The overall mean radon concentration in all surveyed districts has been found to be 44 ± 16 Bq m^?3. The mean annual estimated effective dose received by the residents of the studied area is estimated to be 0.75 mSv. The obtained results are compared with the indoor radon levels prescribed by the International Commission on Radiation Protection and are found to be less than the action level recommended.     

Ecotoxicological risks of the abandoned F–Ba–Pb–Zn mining area of Osor (Spain)

Due to its potential toxic properties, metal mobilization is of major concern in areas surrounding Pb–Zn mines. In the present study, metal contents and toxicity of soils, aqueous extracts from soils and mine drainage waters from an abandoned F–Ba–Pb–Zn mining area in Osor (Girona, NE Spain) were evaluated through chemical extractions and ecotoxicity bioassays. Toxicity assessment in the terrestrial compartment included lethal and sublethal endpoints on earthworms Eisenia fetida, arthropods Folsomia candida and several plant species, whereas aquatic tests involved bacteria Vibrio fischeri, microalgae Raphidocelis subcapitata and crustaceans Daphnia magna. Total concentrations of Ba (250–5110 mg kg^?1), Pb (940 to >5000 mg kg^?1) and Zn (2370–11,300 mg kg^?1) in soils exceeded intervention values to protect human health. Risks for the aquatic compartment were identified in the release of drainage waters and in the potential leaching and runoff of metals from contaminated soils, with Cd (1.98–9.15 µg L^?1), Pb (2.11–326 µg L^?1) and Zn (280–2900 µg L^?1) concentrations in filtered water samples surpassing US EPA Water Quality Criteria (2016a, b). Terrestrial ecotoxicity tests were in accordance with metal quantifications and identified the most polluted soil as the most toxic. Avoidance and reproduction tests with earthworms showed the highest sensitivity to metal contamination. Aquatic bioassays performed in aqueous extracts from soils confirmed the results from terrestrial tests and also detected toxic effects caused by the mine drainage waters. Algal growth inhibition was the most sensitive aquatic endpoint. In view of the results, the application of a containment or remediative procedure in the area is encouraged.     

Demography and interannual variability of salp swarms (Thalia democratica)

Swarms of the pelagic tunicate, Thalia democratica, form during spring, but the causes of the large interannual variability in the magnitude of salp swarms are unclear. Changes in asexual reproduction (buds per chain) of T. democratica populations in the coastal waters of south-east Australia (32–35°S) were observed in three austral springs (October 2008–2010). T. democratica abundance was significantly higher in 2008 (1,312 individuals m^?3) than 2009 and 2010 (210 and 92 individuals m^?3, respectively). There was a significant negative relationship (linear regression, r ² = 0.61, F _1,22 = 33.83, P < 0.001) between abundance and asexual reproduction. Similarly, relative growth rates declined with decreasing abundance. Generalised additive mixed modelling showed that T. democratica abundance was significantly positively related to preferred food >2 μm in size (P < 0.05) and negatively related to the proportion of non-salp zooplankton (P < 0.001). Salp swarm magnitude, growth, and asexual reproduction may depend on the abundance of larger phytoplankton (prymnesiophytes and diatoms) and competition with other zooplankton.     

Seasonal and diel variation in movement rhythms of sand dollar, Peronella lesueuri (Valenciennes 1841), in Cockburn Sound, Western Australia

Rates and direction of movement in the sand dollar Peronella lesueuri were measured in summer and winter in Cockburn Sound, a large coastal embayment in south-western Australia. P. lesueuri was found to have a diurnal activity pattern throughout the year and had a greater movement rate in the summer (mean of 5.3 cm h^?1, day; 3.9 cm h^?1, night) than in the winter (mean of 2.7 cm h^?1, day; 2.0 cm h^?1, night). Seasonal change in temperature and physiological requirements by the sand dollar are the most likely reason for the seasonal differences. Reasons for diurnal variation were not clear. Direction of movement was found to be random at both times of the year. Based on these movement rates, one sand dollar can bioturbate an approximate area of 0.1 m² day^?1 and 36.4 m² year^?1. At a conservative density estimate of 0.5 sand dollars per m² it takes approximately 20 days for the sand dollars to rework the entire area of the sediments in the habitats they occupy.     

Dissolved nutrient dynamics along the southwest coastal waters of India during northeast monsoon: a case study

Dissolved nutrients, Chl-a and primary productivity were measured from seven transects along the coastal waters of the southeastern Arabian Sea during northeast monsoon. Ten major estuaries were chosen to study the influence of estuarine discharge on the nutrient dynamics in the coastal waters. The mean water discharge of the estuaries in the north (64.8?±?18?×?10⁵?m³?d^?1) was found to be higher than those in the south (30.6?±?21.4?×?10⁵?m³?d^?1), whereas the nutrient concentrations were found to be higher in the estuaries of the south. The results from the offshore waters were discussed in accordance with the depth contour classification, that is, shelf (depth?≤?30?m) and slope waters (depth?≥?30?m). Our results suggest that the estuarine discharge plays a major role in the nutrient distribution in near shore shelf waters, whereas in shelf and slope waters, it was mainly controlled by in situ biological processes. The inorganic form of N to P ratios were found to be higher than Redfield ratio in slope waters when compared with shelf waters, suggesting that PO₄^3? (<0.15?µmol?L^?1) is a limiting nutrient for primary production. The multivariate statistical analysis revealed that the nutrient dynamics in the coastal waters was controlled by both biological and physical processes.     

Interactive effects of UV radiation and enhanced temperature on photosynthesis, phlorotannin induction and antioxidant activities of two sub-Antarctic brown algae

Lessonia nigrescens and Durvillaea antarctica, two large sub-Antarctic brown algae from the southern Chilean coast, were exposed to solar UV radiation in an outdoor system during a summer day (for 11 h) as well as to artificial UV radiation under controlled laboratory conditions at two temperatures (15 and 20 °C) for 72 h. Chlorophyll a fluorescence–based photoinhibition of photosynthesis was measured during the outdoor exposure, while electron transport rates, lipid peroxidation, antioxidant activity and content of phlorotannins were determined at different time intervals during the laboratory exposure. Under natural solar irradiances in summer, both species displayed well-developed dynamic photoinhibition: F _v/F _m values decreased by 70 % at noon coinciding with the levels of PAR >1,500 μmol m^?2 s^?1 and UV-B radiation >1 W m^?2 and recovered substantially in the afternoon. In treatments including UV radiation, recovery in D. antarctica started already during the highest irradiances at noon. The results from laboratory exposures revealed that (a) elevated temperature of 20 °C exacerbated the detrimental effects of UV radiation on photochemical parameters (F _v/F _m and ETR); (b) peroxidative damage measured as MDA formation occurred rapidly and was strongly correlated with the decrease in F _v/F _m, especially at elevated temperature of 20 °C; (c) the antioxidant activity and increases in soluble phlorotannins were positively correlated mainly in response to UV radiation; (d) phlorotannins were rapidly induced but strongly impaired at 20 °C. In general, short-term (2–6 h) exposures to enhanced UV radiation and temperature were effective to activate the photochemical and biochemical defenses against oxidative stress, and they continued operative during 72 h, a time span clearly exceeding the tidal or diurnal period. Furthermore, when algae were exposed to dim light and control temperature of 15 °C for 6 h, F _v/F _m increased and lipid peroxidation decreased, indicating consistently that algae retained their ability for recovery. D. antarctica was the most sensitive species to elevated temperature for prolonged periods in the laboratory. Although no conclusive evidence for the effect of the buoyancy of fronds was found, the interspecific discrepancies in thermo-sensitivity in the UV responses found in this study are consistent with various ecological and biogeographical differences described for these species.     

Metal characterization of airborne particulate matters in a coastal region

The concentrations of suspended particulate matter in the air of the Orissa Sand Complex had an average value of 128 ± 10 µg m^?3 in residential areas and 170 ± 8 µg m^?3 in mining areas. PM₁₀ levels in residential areas were found to have an average of 35 ± 10 µg m^?3, in mining areas 45 ± 10 µg m^?3. The distribution of some elements is also discussed here. Inhalation doses were observed to be higher in summer than in winter and the rainy season. The highest dose rate was for the age group of 1 year, and health risks were found to be highest for the same. For adults, inhalation dose and health risk are 1.3 times higher in mining than in residential areas.     

Seasonal changes in biomass,growth rates and production of subantarctic calanoid copepods in the Bay of Morbihan,Kerguelen Islands

The present study addresses the ecology of two dominant copepod species in the Bay of Morbihan, Kerguelen Archipelago. The biomass of the herbivore Drepanopus pectinatus (from 2 mg m^?3 in winter up to 500 mg m^?3 in summer) is tightly coupled to seasonal changes in chlorophyll a concentration in the region, whereas the biomass of the predatory euchaetiid Paraeuchaeta antarctica increases during two distinct periods over the year: 250 mg m^?3 in early summer, with the recruitment of the annual generation, and 100 mg m^?3 in autumn, with the deposition of lipids as energy reserves in C5 stages and adults. The juvenile growth rates predicted by temperature-dependent models (0.09 day^?1) closely approximate those observed in D. pectinatusin summer, but are much greater than those observed in P. antarctica (from 0.001 to 0.04 day^?1 depending on developmental stages). This difference can be explained by the reproductive strategies and trophic positions of the two species and may also result from the dependence of larval growth on energy reserves in P. antarctica. The production rates are five- and tenfold greater in juvenile stages than in adults, respectively, for D. pectinatus and P. antarctica. The secondary production by D. pectinatusis insufficient to support P. antarcticaduring winter, when the predatory species probably shifts to alternate prey. In summer the predation by P. antarctica accounts for only a minor part of the mortality estimated for D. pectinatus (from 20% to 60% depending on the examined station). At two of the three stations examined in the Bay of Morbihan, the production of P. antarctica could potentially support the dietary requirements of planktivorous seabirds in the region (~2,000 kg prey day^?1 for common diving petrels, Pelecanoides urinatrix, and ~90 kg prey day^?1 for rockhopper penguins, Eudyptes chysocome filholi).     

Environmental impact of CO<Subscript>2</Subscript>, Rn,Hg degassing from the rupture zones produced by Wenchuan <Emphasis Type="Italic">M</Emphasis><Subscript>s</Subscript> 8.0 earthquake in western Sichuan,China

The concentrations and flux of CO₂, ²²²Radon (Rn), and gaseous elemental mercury (Hg) in soil gas were investigated based on the field measurements in June 2010 at ten sites along the seismic rupture zones produced by the May 12, 2008, Wenchuan M _s 8.0 earthquake in order to assess the environmental impact of degassing of CO₂, Rn and Hg. Soil gas concentrations of 344 sampling points were obtained. Seventy measurements of CO₂, Rn and Hg flux by the static accumulation chamber method were performed. The results of risk assessment of CO₂, Rn and Hg concentration in soil gas showed that (1) the concentration of CO₂ in the epicenter of Wenchuan M _s 8.0 earthquake and north end of seismic ruptures had low risk of asphyxia; (2) the concentrations of Rn in the north segment of seismic ruptures had high levels of radon, Maximum was up to level 4, according to Chinese code (GB 50325-2001); (3) the average geoaccumulation index I _geo of soil Hg denoted the lack of soil contamination, and maximum values classified the soil gas as moderately to strongly polluted in the epicenter. The investigation of soil gas CO₂, Rn and Hg degassing rate indicated that (1) the CO₂ in soil gas was characterized by a mean \(\updelta^{13}C_{CO2}\) of ?20.4 ‰ and by a mean CO₂ flux of 88.1 g m^?2 day^?1, which were in the range of the typical values for biologic CO₂ degassing. The maximum of soil CO₂ flux reached values of 399 g m^?2 day^?1 in the epicenter; (2) the soil Rn had higher exhalation in the north segment of seismic ruptures, the maximum reached value of 1976 m Bq m^?2 s^?1; (3) the soil Hg flux was lower, ranging from ?2.5 to 18.7 n g m^?2 h^?1 and increased from south to north. The mean flux over the all profiles was 4.2 n g m^?2 h^?1. The total output of CO₂ and Hg degassing estimated along seismic ruptures for a survey area of 18.17 km² were approximately 0.57 Mt year^?1 and 688.19 g year^?1. It is recommended that land-use planners should incorporate soil gas and/or gas flux measurements in the environmental assessment of areas of possible risk. A survey of all houses along seismic ruptures is advised as structural measures to prevent the ingress of soil gases, including CO₂ and Rn, were needed in some houses.     

Geochemistry and quality of groundwater of the Yarmouk basin aquifer,north Jordan

Quality of groundwater in the Yarmouk basin, Jordan has been assessed through the study of hydrogeochemical characteristics and the water chemistry as it is considered the main source for drinking and agriculture activities in the region. The results of the relationship between Ca²⁺ + Mg²⁺ versus HCO₃^? + CO₃^2?, Ca²⁺ + Mg²⁺ versus total cations, Na⁺ + K⁺ versus total cations, Cl^? + SO₄^2? versus Na⁺ + K⁺, Na⁺ versus Cl^?, Na⁺ versus HCO₃^? + CO₃^2?, Na⁺ versus Ca²⁺, and Na⁺: Cl^? versus EC describe the mineral dissolution mechanism through the strong relationship between water with rocks in alkaline conditions with the release of Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^?, CO₃^2?, SO₄^2?, and F^? ions in the groundwater for enrichment. Furthermore, evaporation processes, groundwater depletion, and ion exchange contribute to the increased concentration of Na⁺ and Cl^? ions in groundwater. Anthropogenic sources are one of the main reasons for contamination of groundwater in the study area and for increasing the concentration of Mg²⁺, Na⁺, Cl^?, SO₄^2?, and NO₃^? ions. Results show the quality of groundwater in the study area is categorized as follows: HCO₃^? + CO₃^2? > Cl^? > SO₄^2? > NO₃^? > F^? and Na⁺ > Ca²⁺ > Mg²⁺ > K⁺. In conclusion, the results of TDS, TH, and chemical composition showed that 26% of the groundwater samples were unsuitable for drinking. About 28% of groundwater samples in the study area have a high concentration of Mg²⁺, Na⁺, and NO₃^? above the acceptable limit. Also, based on high SAR, 10% of the groundwater samples were not suitable for irrigation purposes.     

Winter diet shift of long-beaked common dolphins (Delphinus capensis) feeding in the sardine run off KwaZulu-Natal, South Africa

Unpredictable inter-annual variations in the timing, spatial extent and intensity of the sardine run (Sardinops sagax) have been documented in recent years along the coastline of KwaZulu-Natal, South Africa. This study aimed to determine whether variations in the availability of sardine were reflected in the diet and condition of common dolphins (Delphinus capensis) over the past three decades. Stomach contents from 95 common dolphins incidentally caught between 2000 and 2009 were analysed and compared to historical data collected between 1972 and 1992. A shift in the principal prey species consumed by the dolphins was observed over the past 30 years. Prior to 1992, sardine comprised up to 49 % of the total stomach contents by mass, whilst chub mackerel (Scomber japonicus) was the dominant prey recorded in the stomach contents between 2000 and 2009 (66 %). As common dolphins prey on locally abundant fish species, this dietary shift may indicate changes in the availability of the most abundant fish prey. Stable isotope analyses of tooth tissue revealed no significant changes in the δ¹⁵N and δ¹³C isotopic ratios over the past three decades (P = 0.283 for N and P = 0.922 for C). Blubber thickness as a percentage of body length and blubber weight as a percentage of total body weight were assessed as indicators of animal condition. No significant changes in proportional blubber weight or blubber thickness were seen over the last 40 years (1970–2009) for all age cohorts. This species appears to be well adapted to cope with changes in prey species availability, without impacting on body condition.     

Temporal variability in atmospheric Hg released from natural and anthropogenic sources in central Taiwan

From September 2011 to February 2012, ambient air particulate and particulate-bound mercury [Hg(p)] concentrations were measured, together with dry deposition using a cold vapor atomic fluorescence spectrometry (CVAFS) analyser, at two characteristic sampling sites in central Taiwan. Results from the sampling site at Westin Park indicated that the lowest particulate dry deposition and lowest average particulate concentrations in total suspended particles (TSP) occurred in September (29.70±7.47 μ g m^?2×min) and February (34.38±13.60 ng m^?3), respectively. Moreover, results from the Gung-Ming junior high school (airport) site, showed that the highest average particulate dry deposition and average highest particulate concentrations in TSP occurred in February (156.76±30.36 μ g m^?2×min) and January (125.49±9.51 ng m^?3), respectively, during the winter. The Dragon Steel Plant and Han-Shian Aerospace Industrial Development Corporation were both nearby. These factors led to the high Hg(p) concentrations at Taichung Airport (TA) compared with Westin Park. Local large suspended particulates from heavy traffic were the main reason for the high average Hg(p) deposition at Westin Park compared with TA in this study.     

Metal levels in computer monitor components discarded in the vicinities of electronic workshops

Levels of Pb, Ni, Cr, Cu, Zn, and Cd in the glass screens (GS) and printed wiring boards (PWBs) of obsolete computer monitors (OCMs) were determined by flame atomic absorption spectrophotometry (FAAS) following standard digestion. Metal concentrations (mg kg^?1) in GS were in the following ranges (medians in brackets): Pb ND – 3100 (46), Cd 0.5–2.6 (0.8), Cr ND – 18.7 (3.1), and Zn 8.1–600 (37) and in PWBs (mg kg^?1): Pb 34,600 ± 17,000, Cd 11 ± 9, Cr 59 ± 45, Zn 15,900 ± 7800, Cu79,000 ± 22,600, and Ni 3200 ± 2500. In GS, the levels of the six metals were lower than their total threshold limit concentrations (TTLC), except for Pb with a TTLC of 1000 mg kg^?1 in 10% of the samples. In the PWBs, the TTLC of Pb and Cu (2500 mg kg^?1) was exceeded many fold. For Zn (5000 mg kg^?1) and Ni (2000 mg kg^?1); they were exceeded by 90% and 65%, respectively. For OCMs manufactured in 2001 and later, Pb and Zn levels in GS and Cr, Zn, and Ni in PWBs were significantly reduced.     

An osteological study of the dugong Dugong dugon (Sirenia) from India

An osteological study of the dugong (sea cow) Dugong dugon (Müller) from India, based on complete skeletons of an adult male and a juvenile female indicated certain morphological variations with age. It has also revealed a close osteological similarity between the dugongs from India and the Red Sea. Based on a statistical analysis, regression equations for certain typical skull measurements have been calculated; these equations, characteristic of the dugong from India, could be used for comparing dugongs of different regions.     

Diffusive boundary layers and photosynthesis of the epilithic algal community of coral reefs

The effects of mass transfer resistance due to the presence of a diffusive boundary layer on the photosynthesis of the epilithic algal community (EAC) of a coral reef were studied. Photosynthesis and respiration of the EAC of dead coral surfaces were investigated for samples from two locations: the Gulf of Aqaba, Eilat (Israel), and One Tree Reef on the Great Barrier Reef (Australia). Microsensors were used to measure O₂ and pH at the EAC surface and above. Oxygen profiles in the light and dark indicated a diffusive boundary layer (DBL) thickness of 180–590 μm under moderate flow (~0.08 m s^?1) and >2,000 μm under quasi-stagnant conditions. Under light saturation the oxygen concentration at the EAC surface rose within a few minutes to 200–550% air saturation levels under moderate flow and to 600–700% under quasi-stagnant conditions. High maximal rates of net photosynthesis of 8–25 mmol O₂ m^?2 h^?1 were calculated from measured O₂ concentration gradients, and dark respiration was 1.3–3.3 mmol O₂ m^?2 h^?1. From light–dark shifts, the maximal rates of gross photosynthesis at the EAC surface were calculated to be 16.5 nmol O₂ cm^?3 s^?1. Irradiance at the onset of saturation of photosynthesis, E _k, was <100 µmol photons m^?2 s^?1, indicating that the EAC is a shade-adapted community. The pH increased from 8.2 in the bulk seawater to 8.9 at the EAC surface, suggesting that very little carbon in the form of CO₂ occurs at the EAC surface. Thus the major source of dissolved inorganic carbon (DIC) must be in the form of HCO₃ ^?. Estimates of DIC fluxes across the DBL indicate that, throughout most of the daytime under in situ conditions, DIC is likely to be a major limiting factor for photosynthesis and therefore also for primary production and growth of the EAC.     

Energy demand of larval and juvenile Cape horse mackerels, Trachurus capensis, and indications of hypoxia tolerance as benefit in a changing environment

Trachurus capensis is an important fisheries resource in the degraded Namibian upwelling ecosystem. Food supply and shoaling of hypoxic zones are hypothesised to influence the species’ recruitment success. This paper is the first to quantify energy requirements and hypoxia tolerance of larval and juvenile stages of a Trachurus species. We measured normoxic respiration rates of T. capensis with a size range from 0.001 to 20.8 g wet mass (WM) collected off Cape Town (33.9°S, 18.5°E, 12/2009) and in the northern Benguela (17–24°S, 11–15°E, 02/2011). Routine metabolic rate (RMR) and standard routine rate (SRR) (mg O₂ h^?1) followed the allometric functions RMR = 0.418 WM^0.774 and SRR = 0.275 WM^0.855, respectively. Larvae and juveniles had comparatively high metabolic rates, and the energy demand of juveniles at the upper end of the size range appeared too high to be fuelled by a copepod diet alone. T. capensis’ early life stages showed a high tolerance to hypoxic conditions. RMR in larvae did not change until 30 % O₂sat at 18 °C. In juveniles, critical oxygen saturation levels were low (P_C for SRR = 11.2 ± 1.7 % O₂sat and P_C for RMR = 13.2 ± 1.6 % O₂sat at 20 °C) and oxy-regulation effective (regulation index = 0.78 ± 0.09). A high hypoxia tolerance may facilitate the retention of larvae in near-shore waters providing favourable feeding conditions and allowing juveniles to exploit food resources in the oxygen minimum zone. These mechanisms seem to well adapt T. capensis to a habitat affected by spreading hypoxic zones and probably enhance its recruitment success.     

Hypoxia-driven selective degradation of cellular proteins in jumbo squids during diel migration to the oxygen minimum zones

The jumbo squid, Dosidicus gigas, is an oceanic top predator in the eastern tropical Pacific that undergoes diel vertical migrations into mesopelagic oxygen minimum zones (OMZs). Besides glycogen breakdown, the pathways of the squid’s metabolic (suppression) strategy are poorly understood. Here, juvenile D. gigas were exposed to oxygen levels found in the OMZ off Gulf of California (1 % O₂, 1 kPa at 10 °C) with the aim to identify, via proteomic tools, eventual anaerobic protein degradation as potential energy source at such depths. Under hypoxia, total protein concentration decreased nonsignificantly from 79.2 ± 12.4 mg g^?1 wet mass to 74.7 ± 11.7 mg g^?1 wet mass (p > 0.05). Yet, there was a significant decrease in heat-shock protein (Hsp) 90 and α-actinin contents (p < 0.05). The lower α-actinin concentration at late hypoxia was probably related to decreased protection of the Hsp90 chaperon machinery resulting in increased ubiquitination (p < 0.05) and subsequent degradation. Thus, the present findings indicate that D. gigas might degrade, at least under progressing hypoxia, specific mantle proteins anaerobically to increase/maintain anaerobic ATP production and extend hypoxia exposure time. Moreover, the ubiquitin–proteasome system seems to play an important role in hypoxia tolerance, but further investigations are necessary to discover its full potential and pathways.