Temporal variation in Adélie penguin diet at Béchervaise Island,east Antarctica and its relationship to reproductive performance

Diet, and in particular, food quality and quantity can influence the reproductive performance of marine predators. Also, the diet of specialist predators is often monitored in programmes that model and manage ecosystems. We examined the diet of Adélie penguins (Pygoscelis adeliae), an important consumer of Southern Ocean living resources, at Béchervaise Island, east Antarctica, during the chick-rearing periods for 11 years between 1991–1992 and 2002–2003. We also investigated the relationship between diet and annual reproductive performance. Substantial inter- and intra-annual variation in both meal mass and composition was evident: adults generally returned with larger food loads during the crèche compared with the guard stages, and diet composition was dominated by two prey types, krill and fish, which combined contributed to >90% of the diet by mass in 7 out of 11 years. Females generally brought back meals dominated by krill; males generally consumed fish-dominated meals. However, both sexes returned with a high proportion of krill when annual mean meal mass was also high, suggesting that more food was available in high krill years. There was also evidence that years of high reproductive performance were positively correlated with years of both high meal and krill mass. We believe that our results indicate that there is significant long-term inter- and intra-annual variability in the amount of food available to Adélie penguins and that this was reflected in their diet and measures of reproductive performance. Coupled with the observation that penguins did not switch prey, this indicates that Adélie penguins from Béchervaise Island are dependent predators of krill. This contrasts with populations in other locations but supports the notion that Adélie penguins are an informative species to monitor the management of Southern Ocean marine living resources in this region.     

Isotopic niches of emperor and Adélie penguins in Adélie Land,Antarctica

The emperor and Adélie penguins are the only two species of penguins that co-occur at high-Antarctic latitudes. We first measured and compared their isotopic niches on the same year in Adélie Land in spring, when the two species co-exist. Emperor and Adélie penguins segregated by their blood isotopic signatures, with adult δ¹³C values (−24.5 ± 0.2 and −25.4 ± 0.2‰, respectively) suggesting that emperor penguins foraged in more neritic waters than Adélie penguins in spring. At that time, difference in their δ¹⁵N values (4.1‰, 12.0 ± 0.4 vs. 7.9 ± 0.1‰) encompassed more than one trophic level, indicating that emperor penguins preyed mainly upon fish (and squids), while Adélie penguins fed exclusively on euphausiids. Second, we compared the food of breeding adults and chicks. The isotopic signatures of adults and chicks of emperor penguins were not statistically different, but δ¹⁵N value of Adélie penguin chicks was higher than that of adults (10.2 ± 0.8 vs. 9.0 ± 0.2‰). The difference showed that adult Adélie penguins captured higher trophic level prey, i.e. higher-quality food, for their chicks. Third, the isotopic signatures of Adélie penguins breeding in Adélie Land showed that adults fed on Antarctic krill in oceanic waters in spring and shifted to neritic waters in summer where they preyed upon ice krill for themselves and upon fish and euphausiids for their chicks. A comparison of isotopic niches revealed large overlaps in both blood δ¹³C and δ¹⁵N values within the community of Antarctic seabirds and pinnipeds. The continuum in δ¹⁵N values nevertheless encompassed more than one trophic level (5.2‰) from Adélie penguin and crabeater seal to the Weddell seal. Such a broad continuum emphasizes the fact that all Antarctic seabirds and marine mammals feed on varying proportions of a few crustacean (euphausiids) and fish (Antarctic silverfish) species that dominate the intermediate trophic levels of the pelagic neritic and oceanic ecosystems.     

Differential effects of increased corticosterone on behavior at the nest and reproductive output of chick-rearing Adélie penguins

Glucocorticoid hormones (GCs) are important mediators of physiological and behavioral responses to stress. While many studies have evaluated the environmental, behavioral, or physiological correlates of GCs and their effects on reproductive performances, further work is needed to clarify the relationship between GCs and fitness. Assessing the effects of increased GC levels on specific behaviors of breeding animals should improve our understanding of how GCs affect parental care. In this experimental study, we measured the effects of an experimental increase in corticosterone (CORT, the main avian GC) levels on the behavior of free-living male Adélie penguins (Pygoscelis adeliae) within the colony, their reproductive output, and the indirect consequences of both on the behavior of their partners. We show that increased CORT levels in males decreased their foraging time at sea while increased their attendance at the nest, although their attentiveness toward the nest itself decreased. In addition, treated males spent more time on comfort behaviors (e.g., preening), vocalizing, and engaging in positive social interactions relative to controls. Treatment further affected the behavior of their partners, but not chick begging and feeding rates. Penguins with increased CORT levels also exhibited decreased reproductive output. Previous studies of Adélie penguins in different life history stages and environmental conditions suggest that the consequences of CORT treatment on reproductive performance are context-dependent. In addition to the potential delay in the effects of increased CORT levels on reproduction, this context dependence should be taken into account when studying the behavior of free-living animals in relation to stress-inducing situations.     

Reproductive effort in Adélie penguins

Summary We estimated reproductive effort (energy expenditures for reproduction, as opposed to maintenance) in Adélie penguins breeding at Palmer Station, Antarctica. Data on body composition changes and metabolic rate were obtained using isotopic methods. Adelie breeding behavior consists of an initial courtship stage (during which both sexes fast), incubation, the guard stage (when chicks are 1 to 18–28 days old), and the creche stage (from the end of guarding until chicks are 28–45 days old). Both males and females lost considerable mass during the initial stages of the reproductive season, but males fasted longer and lost more mass. Mass losses of both sexes consisted of 66% depot fat and 34% lean tissue. Mass and body composition remained constant once birds resumed feeding. The metabolic expenditure for the foraging necessary to accumulate the mass lost while fasting — one component of reproductive effort —was about 63 MJ in males and 39 MJ in females. Field metabolic rates (FMR) were low during courtship and while incubating, increasing more than 2-fold when birds resumed foraging. Although mean FMR increased between incubation and the creche stage, differences between stages were small and not significant. We used FMR data and an energy balance model to estimate the cost of feeding chicks. Results suggest a maintenance FMR of about 2.7 × basal metabolism (BMR), increasing to 3.4–3.6 × BMR during the creche stage. The reproductive effort (as metabolic expenditures) associated with feeding chicks is 31 MJ (males) to 36 MJ (females). Cumulative reproductive effort is 94 MJ in males and 75 MJ in females, or 5.3–6.2% of the annual energy budget. The reproductive effort devoted to chick care does not appear to be constrained by physiological or time limitations. Instead, selection to reduce the risk of predation may prevent the evolution of increased parental care. Correspondence to: M.A. Chappell     

Effects of El Niño on distribution and reproductive performance of Black Brant

Climate in low-latitude wintering areas may influence temperate and high-latitude breeding populations of birds, but demonstrations of such relationships have been rare because of difficulties in linking wintering with breeding populations. We used long-term aerial surveys in Mexican wintering areas and breeding areas in Alaska, USA, to assess numbers of Black Brant (Branta bernicla nigricans; hereafter brant) on their principal wintering and breeding area in El Ni?o and non-El Ni?o years. We used Pollock's robust design to directly estimate probability of breeding and apparent annual survival of individually marked brant at the Tutakoke River (TR) colony, Alaska, in each year between 1988 and 2001. Fewer brant wintered in Mexico during every El Ni?o event since 1965. Fewer brant were observed on the principal breeding area following each El Ni?o since surveys began in 1985. Probability of breeding was negatively related to January sea surface temperature along the subtropical coast of North America during the preceding winter. Between 23% (five-year-olds or older) and 30% (three-year-olds) fewer brant nested in 1998 following the strong El Ni?o event in the winter of 1997-1998 than in non-El Ni?o years. This finding is consistent with life history theory, which predicts that longer-lived species preserve adult survival at the expense of reproduction. Oceanographic conditions off Baja California, apparently by their effect on Zostera marina (eelgrass), strongly influence winter distribution of brant geese and their reproduction (but not survival), which in turn affects ecosystem dynamics in Alaska.     

Validation of oesophagus temperature recording for detection of prey ingestion on captive Adélie penguins (Pygoscelis adeliae)

The efficiency of oesophagus and stomach temperature loggers to detect ingestion of prey items was studied in captive Adélie penguins (Pygoscelis adeliae) fed on land in Antarctica and in an aquarium in Japan. On land, the detection rate was studied for different masses of prey delivered at various frequencies, while in the pool the delay between capture and swallowing was investigated. The rate at which food items were detected and the magnitude of the temperature drops induced were higher in the oesophagus than in the stomach. Where small food items were delivered at a high frequency, birds collected prey items in the beak before swallowing them. Thus, oesophagus sensors may underestimate the number of prey swallowed if the system is used in the wild. In the oesophagus temperature recordings, the magnitude of drops was weakly, but positively, correlated to the mass of single, ingested prey (R ²=0.40). Received: 24 April 2000 / Accepted: 20 September 2000     

Foraging strategies of male Adélie penguins during their first incubation trip in relation to environmental conditions

Knowledge of habitat use by top marine predators in response to environmental conditions is crucial in the current context of global changes occurring in the Southern Ocean. We examined the at-sea locations of male Adélie penguins (Pygoscelis adeliae) breeding at Dumont d’Urville during their first, long incubation trip. Compared with the chick-rearing period, penguins performed longer trips, going to oceanic waters as far as 320 km from the colony. We observed 3 strategies: (1) five individuals covered large distances to the north, targeting open-ocean areas and following the currents of two persistent eddies; (2) five individuals foraged to the north-west, close to the Antarctic shelf slope at the limit of the pack ice; and (3) three individuals covered much shorter distances (northwards or eastwards). The foraging range also seemed to be limited by the body condition of the penguins before their departure to sea.     

Abundance and variability of microorganisms and transparent exopolymer particles across the ice–water interface of melting first-year sea ice in the Laptev Sea (Arctic)

The distribution and abundance of transparent exopolymer particles (TEP) was determined in and below pack ice of the Laptev Sea from July to September 1995. Samples were collected from the lowermost 10 cm of ice floes and at 10 cm below the ice–water interface. Abundance of bacteria, protists and TEP was determined, and the sea ice–water boundary layer was characterized using temperature, salinity and molecular viscous shear stress. TEP, with a distinct size distribution signal, were found in highest concentrations inside the sea ice, ranging from not detectable to 16 cm² l⁻¹ (median: 2.9 cm² l⁻¹). In the water, concentrations were one order of magnitude lower, ranged from below detection to 2.7 cm² l⁻¹ (median: 0.2 cm² l⁻¹) and decreased after the middle of August, whereas abundances of autotrophic flagellates (AF), diatoms, heterotrophic flagellates (HF) and ciliates increased. The abundance of TEP decreased with its size in all samples following a power law relationship. The relation of TEP to the microbial community differed between the sea ice and water, being positively correlated with bacteria and diatoms in the ice and negatively correlated with HF in the sea water. The presence of a pycnocline significantly influenced the abundance of organisms, diatom composition and TEP concentrations. Pennate diatoms dominated by Nitzschia frigida were most abundant inside the ice. Though bacteria have the potential to produce exopolymeric substances (EPS), the results of this study indicate that the majority of TEP at the ice–water interface in first-year Arctic summer pack ice are produced by diatoms. Received: 19 August 1999 / Accepted: 4 July 2000     

Persistent “upwelling shadows” and their influence on zooplankton distributions

Physical (temperature and salinity) and biological (zooplankton) properties were sampled over a 15 mo period in 1988 and 1989 to monitor nearshore environmental variability in northern Monterey Bay, California, USA. During the upwelling seasons of 1988 and 1989, there were two distinct bodies of water along the sampling transect. The offshore water body was characterized by recently upwelled water (typically <12°C) while the nearshore body was significantly warmer (approaching 16°C). A sharp thermal gradient (=front) separated the two water bodies. This front persisted 6.5 km from shore throughout the upwelling season of 1988 and was present again in 1989. Zooplankton-assemblage analysis confirmed the presence of two distinct regions in northern Monterey Bay. We refer to this phenomenon as an upwelling shadow, which is the result of the advection of recently upwelled water bearing nutrients and larvae past coastal recesses which are equatorward of upwelling centers.     

δ13C and fatty acid composition of mesopelagic fishes in the South China Sea and their influence factors

Study of the ecology of mesopelagic fishes is central for assessing the active biological pump in the ocean, especially in the mesopelagic layers. The use of δ¹³C and fatty acid analysis can help to analysis the ecology of mesopelagic fishes. Here, we analysed the fatty acid composition of mesopelagic fishes from the continental northern slope of the South China Sea (NSSCS) and compared with nearshore SCS fishes and mesopelagic fishes collected from the Southern Ocean. The mesopelagic fishes had unusually high lipids, which resulted in Δδ¹³C values exceeding 1‰, more than the enrichment factor in the food web. The mesopelagic fishes had higher C18:1n-9/C18:1n-7 and C20:1n-9/ C18:1n-7 ratios compared with other fishes in the SCS, which confirmed that plankton were their main dietary source. The mesopelagic fishes from SCS and Southern Ocean had different ratios of C20:5n-3/C22:6n-3 (EPA/DHA), suggesting geographical locations and diet sources had obvious influence on their fatty acid composition. The SCS mesopelagic fishes had higher C20:4n-6/C22:6n-3 (ARA/DHA) and C20:4n-6/C20:5n-3 (ARA/EPA) ratios than mesopelagic fishes in the Southern Ocean, indicating the influence of physical factors on fatty acid composition. Thus, future studies of the fatty acids in mesopelagic fishes should consider both dietary sources and physical environments.     

Carboxymethyl‐β‐cyclodextrin influence on the solubility and toxicity of substituted indole compounds

The solubilization of eight selected substituted indole compounds (SICs) by carboxymethyl‐β‐cyclodextrin (CMCD) in water is reported. The results show that their solubility was well improved in CMCD aqueous solution, and the stoichiometry of inclusion complex of the studied SICs with CMCD was 1: 1. The acute toxicity to Photobacterium phosphoreum of the investigated SICs in CMCD aqueous solutions was also investigated and was compared with that in water. The results show that the toxicity of five studied SICs decreased while the toxicity of the rest three SICs increased in CMCD aqueous solutions, but neither the increase nor the decrease was significant.     

Early reproduction and development of dominant calanoid copepods in the sea ice zone of the Barents Sea—need for a change of paradigms?

Reproduction and growth of the dominant copepods Calanus finmarchicus, C. glacialis, C. hyperboreus and Pseudocalanus minutus were studied on transects across the sea ice zone of the northern Barents Sea in May and June 1997. C. glacialis and C. finmarchicus were numerically dominant and also the largest component of the biomass. C. hyperboreus was rather rare. Moderate levels of phytoplankton and eventually high concentrations of ice algae supported maximum egg production rates of 53.6 and 48.5 eggs female^–1 day^–1 of C. glacialis in May and June, respectively. Results of incubation experiments were supported by a tremendous abundance of C. glacialis eggs in the water column ranging from 7×10³ to 4.4×10⁴ m^–2 in May and from 9.8×10³ to a maximum of 9.7×10⁴ m^–2 in June. In contrast, C. finmarchicus spawned only in the vicinity of the ice edge, at a maximum rate of 30 eggs female^–1 day^–1. Egg sacs of P. minutus were often observed in the preserved samples, but contained only few eggs, which may be due to loss during sampling. The presence of considerable concentrations of young stages in May and June indicated successful recruitment of C. glacialis and P. minutus. Back calculation using published stage duration estimates indicates March/April as the begin of the reproductive and growth period for these species under the first-year ice of the Barents Sea. Hence, secondary production in the study area starts at the same time as in open water regions and polynyas in the northern North Atlantic. Although the role of ice algae in the nutrition of copepods was not clarified here, the significant relationship between phytoplankton chlorophyll and egg production of C. glacialis suggests that high reproductive activity has already been achieved at moderate food concentrations.Communicated by O. Kinne, Oldendorf/Luhe     

Advances in research on haloalkane dehalogenases and its sulfur mustard degradation function北大核心CSCD

Sulfur Mustard (bis-(2-chloroethyl) sulphide, HD), also known as yperite, is one of the most important blister agents. It could react with a large number of biological molecules with a strong cytotoxicity effect, resulting in blistering, erosion and necrosis of the skin and various tissues. Recently, several classes of microbial enzymes have been found to be able to degrade HD with high catalytic activity but no disadvantages of the common chemical decontamination of HD. Haloalkane dehalogenases (HLDs, EC3.8.1.5) draws great research attention for environmentally friendly decontaminating HD with only nontoxic thiodiglycol produced. In order to provide theoretical reference basis for enzymatic decontamination of HD, this paper reviews the observation and evolutionary relationship, structures, substrate specificities, catalytic properties and potential applications of these HLDs with high catalytic hydrolysis of HD. The analysis shows that these HLDs belonging to the same subfamily have different substrate specificities but similar spatial structures of the catalytic triad contributing to the common SN2 nucleophilic substitution reaction mechanism for catalytic hydrolysis of HD. The paper also suggests that the problems on improving poor stability of HLDs and efficiency of catalytic hydrolysis of HD should be addressed by methods of molecular biology, genetic engineering and immobilized techniques.     

Benefit–risk assessment of commonly consumed fish species from South China Sea based on methyl mercury and DHA

Even though a growing number of reports indicated favorable health effects with fish consumption, kinds of hazardous substances in fish were detected in fish and to be exceeded advisory limitation. Benefit–risk assessment of commonly consumed fish is urgently needed. We conducted fish consumption survey and fish sampling in the coast of South China Sea to assess benefit–risk effect of commonly consumed fish species. For local residents, weekly methyl mercury (MeHg) exposures from commonly consumed fish species ranged from 0.12 to 2.11 μg/kg bw. Apart from Muraenesox cinereus and Acanthopagrus latus, the rest of 92% (23/25) fish species were at low risk of MeHg exposure. Daily docosahexaenoic acid intakes via consuming specific fish were between 42.18 and 1687.04 mg/day. A total of 72% (18/25) fish species could provide 200 mg/day of DNA for local residents. Benefit–risk assessment assuming intelligence quotient (IQ) score model showed net IQ point gains between 1.53 and 5.65 points with consuming various fish species, indicative of large distinction of health benefit from various fish species. This study suggests commonly consumed fish species from China South Sea could bring much more positive effect than negative effect. Species-specific fish should be considered when providing recommendations of fish consumption. Muraenesox cinereus and Acanthopagrus latus should be minded with risk of MeHg exposure in taking large amounts.

     

Effect of iron addition on the performance of anoxic-oxic membrane process and biological phosphorus removal北大核心CSCD

In order to solve the problem of poor treatment of phosphorus in membrane bioreactor (MBR) with long sludge retention time (SRT), a ferric salt was added to enhance phosphorus removal; FeCl36H2O (Fe/P = 2.0) was added to the reactor. The removal efficiency of nitrogen, organic matters, and phosphorus in the MBR was investigated systematically. Moreover, this study focused on the membrane performance, the change of active sludge flora, and the effect of adding a ferric salt on membrane fouling before and after the addition. It was seen that adding the ferric salt could not affect the removal of COD and NH4 +-N and the removal rate of COD and NH4 +-N reached over 90%. However, the average removal rate of phosphorus was 52%, while the removal rate increased by nearly 40% after adding the ferric salt. The effects of adding ferric salts on the dominant bacteria and biological phosphorus removal of activated sludge were further studied. The results showed that the addition of ferric salt (Fe/P = 2.0) decreased the diversity of active sludge flora and relative abundance of some phosphorusaccumulating organisms and had a negative effect on biological phosphorus removal. The analysis of transmembrane pressure difference (TMP) recording revealed that the concentration of iron salts did not exacerbate membrane fouling. The results showed that the concentration of iron salts entering the membrane bioreactor would reduce the relative abundance and phosphorus removal efficiency of the activated sludge in the system to a certain extent, but it had no obvious effect on membrane fouling. It allowed the effluent to attain acceptable standards, especially with respect to phosphorus removal efficiency. © 2018 Science Press. All rights reserved.     

The spectral analysis of Ce^（3＋） and polyferric sulfate composite flocculant and it＇s performance on treating oilfield wastewater

以FeSO.47H2O为原料,NaClO3氧化法制备出聚合硫酸铁,并用Ce^3＋与其进行复合得到复合絮凝剂.运用紫外光谱及傅里叶红外光谱对絮凝剂样品进行了表征,并通过CODCr去除率和浊度去除率考察了絮凝剂处理油田废水的性能.结果表明,Ce^3＋与聚合硫酸铁复合以后,Ce^3＋与聚合硫酸铁中的羟基作用形成了新的化学键Ce—OH—Fe,实现了Ce^3＋与聚合硫酸铁的成功复合.该复合絮凝剂对油田废水的处理效果均优于聚合硫酸铁,当复合比为1.5%时处理效果最好,CODC r去除率和浊度去除率均接近或高于90%,表现出良好的应用前景.     

Genotoxic and cytotoxic in vitro evaluation of ivermectin and its formulation ivomec® on Aedes albopictus larvae (CCL-126™) cells

Genotoxic effects of ivermectin (IVM) and its commercial formulation ivomec® (IVM 1.0%) were studied on Aedes albopictus larvae (CCL-126?) cells by sister chromatid exchange (SCE) and single cell gel electrophoresis (SCGE) while cytotoxicity was determined by cell-cycle progression (CCP), proliferative rate index (PRI), mitotic index (MI), 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and neutral red (NR) endpoints within a 1–250 µg mL^?1 concentration range. While IVM and ivomec® did not markedly affect SCE frequencies, these agents induced DNA-strand breaks enhancing both slightly damaged and damaged cells at 25–50 and 5–50 µg mL^?1 IVM and ivomec®, respectively. Both compounds exerted a delay in CCP and reduction of PRI at 10 µg mL^?1. Cytotoxicity was observed at concentrations higher than 25 µg mL^?1. A marked reduction of about 98% and 94% of MI compared to controls was noted with 25 µg mL^?1 of IVM and ivomec®, respectively. NR and MTT assays revealed that both compounds induced a cell growth inhibition within the 1–250 µg mL^?1 concentration range. Data indicated that IVM and ivomec® exert both genotoxicity and cytotoxicity in insect cells in vitro, at least in A. albopictus larvae CCL-126? cells.