The seasonal changes in somatic energy content of Gulf of Alaska yellowfin sole, Pleuronectes asper

Seasonal measurement of body energy content was made for Pleuronectes asper (Pallas, 1814) from the Gulf of Alaska. Whole body energy content of complete fish (～ 3472 J g^?1 wet wt) was minimal in May for females as their overwintering phase ended, then increased to ～ 4456 J g^?1 prior to spawning. The ovarian index [(g.w./t.w.) × 100] and energy content of ovaries (J g^?1) was highest in June and May respectively, and then declined markedly by August as spawning occurred. Throughout the year male whole body energy content of complete fish ranged from 3351 to 4590 J g^?1 with the lowest values in May and highest values occurring during June to September, the feeding season. The testes index [(g.w./t.w.) × 100] and total energy content of testes (J g^?1) were high in March and lowest during June and July. On a weight-specific basis, males and females had similar whole body energy values throughout the year. Juveniles followed the same seasonal trends in energy storage as adults and had similar whole body energy values. Whole body energy content was linearly related to wet and dry weight condition factor with r² values of 0.70 and 0.87, respectively. Dry body weight as percent of wet body weight was the best predictor of body energy (r²=0.91). Yellowfin sole had an annual energy cycle with energy accumulation and growth from May to September. Thereafter they utilized stored energy for metabolic and reproductive needs. Spawning began in late May or early June and fish were spent by August. Whole body energy content increased by 28, 33 and 35% between May and June, for females, juveniles, and males, respectively, the most dramatic change during the year long survey. This suggests that intense feeding in May must be an important aspect of their energy storage cycle.     

Physiological ecology of a tropical dragon,Lophognathus temporalis

Lophognathus temporalis is an arboreal lizard from the wet–dry tropics of Australia. During the wet season the field metabolic rate (FMR) of the lizards was 209 kJ kg^?1 d^?1, but during the dry season FMR was only 62 kJ kg^?1 d^?1. Similarly, water flux decreased from 73.6 mL kg^?1 d^?1 in the wet season to 18.5 mL kg^?1 d^?1 in the dry season. Body temperatures (T_b) were significantly lower in the dry season, and operative temperatures, calculated by incorporating microclimatic data with characteristics of the lizards, indicated that the seasonal shift was due to changes in thermoregulatory behaviour rather than limitations of the thermal environment. By combining field measurements of T_b and FMR with laboratory measurements of standard metabolic rate over a range of T_b, we were able to subdivide the FMR into its components and to determine which factors contributed to the seasonal reduction in energy expenditure. During the dry season, lizards used 147 kJ kg^?1 d^?1 less energy than during the wet season, and 24% of this decrease was estimated to be due to the passive effects of lower nighttime T_b, 14% was due to the active selection of lower daytime T_b, 27% was due to the physiological shift to lower standard metabolic rates, and 35% was due to reduced activity in the dry season. Although the population size remained relatively constant (107 lizards ha^?1 during the wet season and 125 lizards ha^?1 during the dry season), the population structure changed, reflecting the seasonal patterns of recruitment and mortality. The number of lizards active at any one time was much lower in the dry season, reflecting the lower levels of activity in this season. The energy expenditure of the population of L. temporalis was 612 kJ ha^?1 d^?1 during the wet season and 113 kJ ha^?1 d^?1 during the dry season.     

Energy Content of Antarctic Mesopelagic Fishes: Implications for the Marine Food Web

For a better understanding of the role of mesopelagic fish in the Southern Ocean food web, the energy and water content of Bathylagus antarcticus, Electrona antarctica and Gymnoscopelus braueri from the Lazarev Sea were investigated. Mean dry weight energy content of B. antarcticus (20.4 kJ g⁻¹) was significantly lower than in E. antarctica and G. braueri (both 29.4 kJ g⁻¹). In E. antarctica, an increase of dry weight energy density with age was evident from 26.9 kJ g⁻¹ in juveniles of less than 1 year of age to 32.0 kJ g⁻¹ in 3-year-old fish. Water content decreased with size in all three species. Abundant high-energy species such as E. antarctica are at a key position in the food web. Due to a marked influence of age on energy content, population structure can be an important variable in estimates of energy fluxes in the Southern Ocean ecosystem.     

Comparison of the mass and energy exchange of a pasture and a mature transitional tropical forest of the southern Amazon Basin during a seasonal transition

This research utilized tower‐based eddy covariance to quantify the trends in net ecosystem mass (CO₂ and H₂O vapor) and energy exchange of important land‐cover types of NW Mato Grosso during the March–December 2002 seasonal transition. Measurements were made in a mature transitional (ecotonal) tropical forest near Sinop, Mato Grosso, and a cattle pasture near Cotriguaçú, Mato Grosso, located 500 km WNW of Sinop. Pasture net ecosystem CO₂ exchange (NEE) was considerably more variable than the forest NEE over the seasonal transition, and the pasture had significantly higher rates of maximum gross primary production in every season except the dry–wet season transition (September–October). The pasture also had significantly higher rates of whole‐ecosystem dark respiration than the forest during the wetter times of the year. Average (±95% CI) rates of total daily NEE during the March–December 2002 measurement period were 26±15 mmol m^?2 day^?1 for the forest (positive values indicate net CO₂ loss by the ecosystem) and ?38±26 mmol m^?2 day^?1 for the pasture. While both ecosystems partitioned more net radiation (R_n) into latent heat flux (L_e), the forest had significantly higher rates of L_e and lower rates of sensible heat flux (H) than the pasture; a trend that became more extreme during the onset of the dry season. Large differences in pasture and forest mass and energy exchange occurred even though seasonal variations in micrometeorology (air temperature, humidity, and radiation) were relatively similar for both ecosystems. While the short measurement period and lack of spatial replication limit the ability to generalize these results to pasture and forest regions of the Amazon Basin, these results suggest important differences in the magnitude and seasonal variation of NEE and energy partitioning for pasture and transitional tropical forest.     

Milk composition and lactational output in the greater spear-nosed bat, Phyllostomus hastatus

Growth rates of mammalian young are closely linked to the ability of the mother to provide nutrients; thus, milk composition and yield provide a direct measure of maternal investment during lactation in many mammals. We studied changes in milk composition and output throughout lactation in a free-ranging population of the omnivorous bat, Phyllostomus hastatus. Fat and dry matter of milk increased from 9 to 21% and from 21 to 35% of wet mass, respectively, throughout lactation. Energy increased from 6 to 9 kJ · g⁻¹ wet mass, primarily due to the increase in fat concentration. Total sugar levels decreased slightly but non-significantly. Mean sugar level was 4.0% of wet mass. Protein concentration increased from 6 to 11% of wet mass at peak lactation and then decreased as pups approached weaning age. Total milk energy output until pups began to forage was 3609 kJ. Milk levels of Mg, Fe, Ca, K, and Na averaged 0.55 ± 0.26, 0.23 ± 0.2, 8.75 ± 4.17, 5.42 ± 2.11, and 9.87 ± 4.3 mg · g⁻¹ dry matter, respectively. Of the minerals studied, calcium appears to be most limiting in this species. The high degree of variability in foraging time, milk composition and milk yield between individuals at the same stage of lactation could potentially yield high variance in reproductive success among females of this polygynous species. Accepted: 23 January 1997     

High rates of net primary production and turnover of floating grasses on the Amazon floodplain: implications for aquatic respiration and regional CO2 flux

We investigated whether rates of net primary production (NPP) and biomass turnover of floating grasses in a central Amazon floodplain lake (Lake Calado) are consistent with published evidence that CO₂ emissions from Amazon rivers and floodplains are largely supplied by carbon from C4 plants. Ground‐based measurements of species composition, plant growth rates, plant densities, and areal biomass were combined with low altitude videography to estimate community NPP and compare expected versus observed biomass at monthly intervals during the aquatic growth phase (January–August). Principal species at the site were Oryza perennis (a C3 grass), Echinochloa polystachya, and Paspalum repens (both C4 grasses). Monthly mean daily NPP of the mixed species community varied from 50 to 96 g dry mass m^?2 day^?1, with a seasonal average (±1SD) of 64±12 g dry mass m^?2 day^?1. Mean daily NPP (±1SE) for P. repens and E. polystachya was 77±3 and 34±2 g dry mass m^?2 day^?1, respectively. Monthly loss rates of combined above‐ and below‐water biomass ranged from 31% to 75%, and averaged 49%. Organic carbon losses from aquatic grasses ranged from 30 to 34 g C m^?2 day^?1 from February to August. A regional extrapolation indicated that respiration of this carbon potentially accounts for about half (46%) of annual CO₂ emissions from surface waters in the central Amazon, or about 44% of gaseous carbon emissions, if methane flux is included.     

Influence of an intermittent food supply on energy storage by the subpolar deposit feeder Yoldia hyperborea (Bivalvia: Nuculanidae)

Food supply for deposit feeders varies from highly seasonal phytodetritus to a steady source of older organic matter, resulting in contrasting patterns of nutrient uptake and storage. To identify patterns in energy storage and feeding behaviour driven by different food conditions for the circumpolar deposit-feeding protobranch bivalve Yoldia hyperborea, we measured variations in cytological (digestive cell height) and biochemical (lipid class, fatty acid, glycogen, and protein content) components during controlled experiments. Three treatments with organisms in sediment with high refractory organic matter (12 % OM) were exposed to different feeding regimes resembling (a) the annual spring bloom settlement, (b) low food availability during winter, and (c) sporadic resuspension events. Yoldia exposed to a diatom-supplemented diet showed significantly higher mean values for digestive cell height (28.44 μm), glycogen (30.4 mg g^?1 dry mass, DM), diatom-specific fatty acids, and total lipid (TL) levels (14.4 mg g^?1 DM), but lower protein concentrations, than in non-supplemented treatments (digestive cell height 20.34 μm; glycogen 9.23 mg g^?1 DM; TL 6.7 mg g^?1 DM). All analyses showed no effect of resuspension events; thus, it was unlikely that resuspension improved sediment nutritional value. In the absence of recently deposited diatoms, Y. hyperborea did not increase nutrient storage, suggesting that significant amounts of older refractory OM are not used for growth or reproduction. The rapid storage of nutrients derived from diatoms demonstrates the role of seasonal episodic events of settling algae in the nutrition of subpolar Y. hyperborea and in the transfer of energy from the water column to the benthos.     

Microbiological changes in whiting (Merlangius merlangus Linneaus, 1758) fillets during short‐term cold storage and a traditional ‘pastrami‐like’ treatment

The objective of this study was to test the effects of salt‐dried whiting (Merlangius merlangus) fillet storage when treated with a special paste and stored covered. For this purpose whiting fillets were salt‐dried at 4–6°C for 15 days. A subsequent test series involved a paste mixture prepared from ground fenugreek, cumin seeds, black pepper, red pepper powder and garlic. The fillets were coated with this paste and air‐dried (15–20°C) for 5 days. All microbiological changes during this drying period were noted. The aerobic mesophilic bacterial counts decreased significantly (P < 0.05) from 5.08 ± 0.20 log cfu g^?1 to 3.24 ± 0.06 log cfu g^?1 after 15 days of salt‐drying. After then covering with paste and drying for 5 days (at 15–20°C), the aerobic mesophilic and lactic acid bacteria counts of the fillets increased to 6.05 ± 0.45 and 5.85 ± 0.06 log cfu g^?1, respectively. The pH values of dried whiting fillets changed after 15 days of dry salting (from 6.1 to 6.4), but after coating and drying with the paste, the pH values were 5.6 on day 5. Enterobactericeae were few in number at the start of salt‐drying (about 1.20 ± 0.15 log cfu g^?1), but their number decreased to <1.0 log cfu g^?1 after 15 days of dry‐salt storage. Staphylococcus aureus, Escherichia coli, mould and yeast were not detected at any time of drying. According to the resuts of the microbiological analyses, dried whiting fillet are considered safe for human consumption.     

Seasonal variability of the parameters of the Ball–Berry model of stomatal conductance in maize (Zea mays L.) and sunflower (Helianthus annuus L.) under well‐watered and water‐stressed conditions

The Ball–Berry (BB) model of stomatal conductance (g_s) is frequently coupled with a model of assimilation to estimate water and carbon exchanges in plant canopies. The empirical slope (m) and ‘residual’ g_s (g₀) parameters of the BB model influence transpiration estimates, but the time‐intensive nature of measurement limits species‐specific data on seasonal and stress responses. We measured m and g₀ seasonally and under different water availability for maize and sunflower. The statistical method used to estimate parameters impacted values nominally when inter‐plant variability was low, but had substantial impact with larger inter‐plant variability. Values for maize (m = 4.53 ± 0.65; g₀ = 0.017 ± 0.016 mol m^?2 s^?1) were 40% higher than other published values. In maize, we found no seasonal changes in m or g₀, supporting the use of constant seasonal values, but water stress reduced both parameters. In sunflower, inter‐plant variability of m and g₀ was large (m = 8.84 ± 3.77; g₀ = 0.354 ± 0.226 mol m^?2 s^?1), presenting a challenge to clear interpretation of seasonal and water stress responses – m values were stable seasonally, even as g₀ values trended downward, and m values trended downward with water stress while g₀ values declined substantially.     

The time course of early post-mortem biochemical processes in the abdominal muscle of a commercially important decapod crustacean (Nephrops norvegicus): implications for post-catch processing

The post-mortem processes in the fast abdominal muscle of the Norway lobster Nephrops norvegicus have been investigated by simulating the first 24-h post-harvest in a controlled experiment. Tissue pH and the concentrations of arginine phosphate, glycogen, L-lactate, ATP, ADP, AMP, IMP, HxR, and Hx were measured at the time of sacrifice and 3, 6, 12 and 24 h thereafter. Additionally from the nucleotide values the corresponding adenylate energy charge (AEC) was calculated. The results reveal that the post-mortem biochemical processes in the abdomen of the Norway lobster after sacrifice and during storage at 10°C are comparable to those of vertebrates. It was found that arginine phosphate was depleted from 38.5 ± 5.2 to 10.9 ± 2.9 µmol g^?1 within 3 h, and anaerobic glycolysis was enhanced, so that glycogen was depleted and L-lactate accumulated. The muscle pH decreased significantly from 7.6 ± 0.1 to 7.0 ± 0.15 within 20 min and then continued to decrease at a slower rate. Most interestingly, the ATP concentration was maintained at approximately 3.5 ± 0.3 µmol g^?1 for up to 12 h post-mortem. This is unusually long and indicates a special characteristic of this fast-type crustacean muscle. AMP accumulated to a maximum after 12 h and was then slowly transformed into IMP. The AEC fell from an initial value of 0.88 to only 0.17 after 24 h. When viewed in context with the fishing industry the results demonstrate that when the product is tailed (removal of the cephalothorax) upon catch, as is common practice in this industry, the result will always be an extensive post-mortem glycolytic response that will lead to an unavoidable and rapid depletion of the energy reserves resulting in a product of lesser quality.     

Energy contents and organic constituents in Antarctic and south Chilean marine brown algae

The content of proteins, lipids and carbohydrates and the calorific contents in six Antarctic and three south Chilean brown algae were determined. These constitute the first reports of chemical composition in the endemic Antarctic species Cystosphaera jacquinotii, Phaeurus antarcticus and Desmarestia antarctica. There were no marked differences in total energy levels between Antarctic and cold-temperate species (values between 10.6 and 13 kJ g^–1 dry weight). However, species such as Adenocystis utricularis showed significantly higher ash-free energy (26.3 kJ), which is explained in terms of morpho-functional differentiation. Ascoseira mirabilis and Phaeurus antarcticus showed high total lipids (2.1–2.2% dry weight) and soluble carbohydrates (5.9 and 3.4% dry weight). In general, algae from Chile had similar energy levels and no obvious differences in organic content could be found.     

THE SEASONAL DISTRIBUTION,ABUNDANCE AND DIVERSITY OF DESMIDS (CHLOROPHYTA) IN A SOFTWATER,NORTH TEMPERATE STREAM1

Suspended and benthic algal communities from a mildly acidic, third-order Rhode Island stream were examined to determine the seasonal distribution, abundance and diversity of the lotic desmids. Within a one-year sampling period, 148 species and 202 subspecific taxa of desmids were identified, representing 23 genera. Species of Cosmarium and Closterium accounted for approximately 70% of the desmids present, and were the most diverse and abundant taxa during all seasons except spring, when Hyalotheca dissiliens was the dominant desmid species. Average abundance and species richness generally were greatest during summer for both suspended and benthic desmids. Most desmids occurred in benthic habitats, and were randomly distributed among substrata. Average seasonal abundance was 7.4 × 10⁴ cells·g^?1 dry wt substratum, among 13 types of substrata. Highest desmid abundance was measured among substrata with intricate morphologies, such as Fontinalis spp., which was associated with 1.2 × 10⁶ desmid cells·g^?1 dry wt substratum, or 1.7 × 10³ cells·cm^?2 substratum. Cell division was observed for 70 desmid taxa, and average seasonal reproduction (based on cell numbers) among all substrata ranged from 4% in winter to 20% during summer. In addition, sexually produced zygospores were found occasionally for H. dissiliens. Desmids were distributed among most substrata examined in this stream, with abundance comparable to reported estimates from softwater lakes and acid bogs. In contrast to established dogma, lotic desmids are not incidental drift organisms, but rather comprise a viable and persistent component of the stream periphyton.     

Seasonal differences in isoprene and light-dependent monoterpene emission by Amazonian tree species

Whereas for extra‐tropical regions model estimates of the emission of volatile organic compounds (VOC) predict strong responses to the strong annual cycles of foliar biomass, light intensity and temperature, the tropical regions stand out as a dominant source year round, with only little variability mainly due to the annual cycle of foliar biomass of drought‐deciduous trees. As part of the Large Scale Biosphere Atmosphere Experiment in Amazônia (LBA‐EUSTACH), a remote secondary tropical forest site was visited in the dry‐to‐wet season transition campaign, and the trace gas exchange of a strong isoprene emitter and a monoterpene emitter are compared to the wet‐to‐dry season transition investigations reported earlier. Strong seasonal differences of the emission capacity were observed. The standard emission factor for isoprene emission of young mature leaves of Hymenaea courbaril was about twofold in the end of the dry season (111.5 μgC g^?1 h^?1 or 41.2 nmol m^?2 s^?1) compared to old mature leaves investigated in the end of the wet season (45.4 μgC g^?1 h^?1 or 24.9 nmol m^?2 s^?1). Standardized monoterpene emission rate of Apeiba tibourbou were 2.1 and 3.6 μgC g^?1 h^?1 (or 0.3 and 0.8 nmol m^?2 s^‐1), respectively. This change in species‐specific VOC emission capacity was mirrored by a concurrent change in the ambient mixing ratios. The growth conditions vary less in tropical areas than in temperate regions of the world, and the seasonal differences in emission strength could not be reconciled solely with meteorological data of instantaneous light intensity and temperature. Hence the inadequacy of using a single standard emission factor to represent an entire seasonal cycle is apparent. Among a host of other potential factors, including the leaf developmental stage, water and nutrient status, and abiotic stresses like the oxidative capacity of the ambient air, predominantly the long‐term growth temperature may be applied to predict the seasonal variability of the isoprene emission capacity. The dry season isoprene emission rates of H. courbaril measured at the canopy top were also compared to isoprene emissions of the shade‐adapted species Sorocea guilleminiana growing in the understory. Despite the difference in VOC emission composition and canopy position, one common algorithm was able to predict the diel emission pattern of all three tree species.     

Assessment of egg quality and realised fecundity of whiting Merlangius merlangus L. in captivity

Potential predictors of egg quality were assessed in whiting Merlangius merlangus L. permitted to spawn in a tank from which eggs were collected. These included fertilisation rate, the proportion of viable buoyant eggs, egg diameter, and egg wet and dry weights; all were influenced by temporal effects and were negatively correlated with days from start of spawning. The spawning period was protracted, from February to June. Mean daily egg production per female was 2.74 ± 2.43 g and 2338 ± 2075 eggs, equivalent to 14.6 ± 13.1 g kg^?1 day^?1 female^?1. Egg diameter was 1.21 ± 0.04 mm, egg wet weight 1.20 ± 0.21 mg, dry weight 0.10 ± 0.02 mg, and mean fertilisation rate and hatching rates were 76.8 and 73.3%, respectively. The incubation period ranged from 72 to 80 degree days and was dependent on temperature (x) and described by the equation y = 25.92 e^?0.1219x. Realised fecundity was also assessed to determine if this gave a more accurate measure of reproductive potential, and this was compared with potential fecundity estimated from predictive regressions on fish length from fisheries data. Realised egg production of 20 females of 185 g mean weight and 256 mm fork length was 4 444 360 (95% CL 4 093 961–4 743 018), similar to predicted seasonal egg production based on gravimetric fecundity measurements of wild caught fish.     

Effect of Breed,Cage Type,and Reproductive Phase on Fecal Corticosterone Levels in Doe Rabbits

Fecal corticosterone concentration (FCC) is increasingly being used as a noninvasive indicator of stress in assessment of nonhuman animal welfare. The aim of this study was to evaluate effects of breed, cage type, reproductive phase, and their interactions on FCC levels in doe rabbits. A total of 252 doe rabbits were randomly assigned to 2 groups. Does were individually housed in either standard dimension cages (SC) or in cages with a volume more than double that of the SC. Bigger cages (BC) were equipped with a plastic foot mat. Breed, cage type, and reproductive phase significantly affected FCC. New Zealand hybrids showed higher FCCs (p < .001) when compared witho the autochthonous breed (27.77 ± 0.47 vs. 24.61 ± 0.36 pg g^?1, respectively). Increased cage size coupled with a plastic foot mat resulted in a significant decrease in doe FCC. The highest FCCs were detected at partum (BC: 30.40 ± 0.81 pg g^?1; SC: 33.36 ± 0.86 pg g^?1; p ≤ .05), followed by postweaning (BC: 25.09 ± 0.95 pg g^?1; SC: 27.63 ± 0.95 pg g^?1; p ≤ .05). These results support the hypothesis that measurement of FCC provides a useful indicator of chronic stress in doe rabbits.     

Quantification of allochthonous nutrient input into freshwater bodies by herbivorous waterbirds

1. Waterbirds are considered to import large quantities of nutrients to freshwater bodies but quantification of these loadings remains problematic. We developed two general models to calculate such allochthonous nutrient inputs considering food intake, foraging behaviour and digestive performance of waterbirds feeding in terrestrial habitats: an intake model (IM), mainly based on an allometric relationship for energy requirements and a dropping model (DM), based on allometric relationships for defaecation. 2. Reviewed data of nitrogen (N) and phosphorus (P) content of herbivorous food varied according to diet type (foliage, seeds and roots), season and fertilization. For model parameterization average foliage diet contained 38.20 mg N g^?1 and 3.21 mg P g^?1 (dry weight), whereas mean faeces composition was 45.02 mg N g^?1 and 6.18 mg P g^?1. 3. Daily allochthonous nutrient input increased with body mass ranging from 0.29 g N and 0.03 g P in teals Anas crecca to 5.69 g N and 0.57 g P in mute swans Cygnus olor. Results from IM differed from those of DM from ducks to swans by 63–108% for N and by ?4 to 23% for P. Model uncertainty was lowest for the IM and mainly caused by variation in estimates of food retention time (RT). In DM food RT and dropping mass determined model uncertainty in similar extent. 4. Exemplarily applying the models to Dutch wetlands resulted in mean annual contribution of herbivorous waterbirds to allochthonous nutrient loading of 382.8 ± 167.1 tonnes N a^?1and 34.7 ± 2.3 tonnes P a^?1, respectively, which corresponds to annual surface‐water loadings of 1.07 kg N ha^?1 and 0.10 kg P ha^?1. 5. There was a distinct seasonal pattern with peak loadings in January, when bird abundances were highest. Lowest inputs were in August, when bird abundance and nutrient content in food was low and birds foraged less in terrestrial habitats. Three‐quarters of all nutrient input was contributed by greater white‐fronted goose Anser albifrons, greylag goose Anser anser, wigeon Anas penelope and barnacle goose Branta leucopsis alone. 6. We provide general, easy to use calculation methods for the estimation of allochthonous nutrient inputs by waterbirds, which are applicable to a range of waterbird species, a variety of potential diets and feeding behaviours, and across spatial scales. Such tools may greatly assist in the planning and execution of management actions for wetland nutrient budgets.     

Total Mercury in Sediments,Macrophytes, and Fish from a Shallow Steppe Lake in Eastern Austria

During summer 2011, samples of sediment, macrophytes, and fish tissues from the shallow, slightly alkaline Lake Neusiedl, Austria, were evaluated for their total Hg content. This is the first report of Hg levels from this lake. Sediments displayed Hg contents between 0.025 and 0.113 μg g^?1 dw (dry weight), significantly correlating with the proportion of organic components pointing to a small anthropogenic impact on the lake's Hg content. Hg Levels in plants and fish were unexpectedly high: both investigated submerged plant species, Potamogeton pectinatus and Myriophyllum spicatum, showed mean values of 0.245±0.152 and 0.298±0.115 μg g^?1 dw, respectively. Biomagnification was evident when comparing muscle samples of the planktivorous fish species rudd Scardinus erythrophthalmus (n=10, mean=0.084 μg g^?1 ww (wet weight)) with the piscivorous perch Perca fluviatilis (n=21, mean=0.184 μg g^?1 ww) or pike‐perch Sander lucioperca (n=9, mean=0.205 μg g^?1 ww). Significantly lower values were found in the muscle of the piscivorous pike Esox lucius (n=25, mean=0.135 μg g^?1 ww), pointing to a specific Hg metabolism of this fish, presumably under the particular physicochemical properties of the lake. Hg Concentrations in fish could pose a risk to piscivorous birds in this protected wetland system.     

Dietary arginine requirement of fingerling Indian major carp,Labeo rohita (Hamilton) based on growth,nutrient retention efficiencies,RNA/DNA ratio and body composition

To quantify the optimum dietary arginine requirement of fingerling Indian major carp, Labeo rohita (4.10 ± 0.04 cm; 0.62 ± 0.02 g), an 8‐week growth trial was conducted in eighteen 70‐L indoor circular aqua‐coloured troughs provided with a flow‐through system at 28 ± 1°C. Isonitrogenous (40 g 100 g^?1 crude protein) and isocaloric (4.28 kcal g^?1 gross energy) amino acid test diets containing casein and gelatin as intact protein sources with graded levels of arginine (0.5, 0.75, 1.0, 1.25, 1.50 and 1.75 g 100 g^?1 dry diet) were fed to triplicate groups of fish to apparent satiation at 07:00, 12:00 and 17:30 hours. Growth performance of fish fed the above diets was evaluated on the basis of absolute weight gain (AWG), specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), protein retention efficiency (PRE) and energy retention efficiency (ERE). Maximum AWG (2.61), SGR (2.80), best FCR (1.35), highest PER (1.85), PRE (37%) and ERE (76%) were recorded at 1.25 g 100 g^?1 dietary arginine. Maximum body protein (18.88 g 100 g^?1) and RNA/DNA ratio (5.20) were also obtained in a 1.25 g 100 g^?1 arginine dry diet. Except for the reduced growth performance in fish fed arginine‐deficient diets, no other deficiency signs were apparent. Based on the broken‐line and second‐degree polynomial regression analysis of the AWG, SGR, FCR, PER, PRE and ERE data, the optimum arginine requirement for fingerling Labeo rohita was found to be in the range of 1.22–1.39 g 100 g^?1 of the dry diet, corresponding to 3.05–3.47 g 100 g^?1 of dietary protein.     

Chemical composition and tissue energy density of the cuttlefish (Sepia apama) and its assimilation efficiency by Diomedea albatrosses

The cuttlefish Sepia apama Gray (Mollusca: Cephalopoda) is a seasonally abundant food resource exploited annually by moulting albatrosses throughout winter and early spring in the coastal waters of New South Wales, Australia. To assess its nutritional value as albatross forage, we analysed S. apama for water, lipid protein, ash contents, energy density and amino acid composition. Because albatrosses consistently consume S. apama parts preferentially in the order of head, viscera and mantle, we analysed these sections separately, but did not identify any nutritional basis for this selective feeding behaviour. The gross energy value of S. apama bodies was 20.9 kJ/g dry mass, but their high water content (>83%; cf <70% for fish) results in a relatively low energy density of 3.53 kJ/g. This may contribute to a need to take large meals, which subsequently degrade flight performance. Protein content was typically >75% dry mass, whereas fat content was only about 1%. Albatrosses feed on many species of cephalopods and teleost fish, and we found the amino acid composition of S. apama to be comparable to a range of species within these taxa. We used S. apama exclusively in feeding trials to estimate the energy assimilation efficiency for Diomedea albatrosses. We estimated their nitrogen-corrected apparent energy assimilation efficiency for consuming this prey to be 81.82 ± 0.72% and nitrogen retention as 2.90 ± 0.11 g N kg⁻¹ d⁻¹. Although S. apama has a high water content and relatively low energy density, its protein composition is otherwise comparable to other albatross prey species. Consequently, the large size and seasonal abundance of this prey should ensure that albatrosses remain replete and adequately nourished on this forage while undergoing moult.     

Fluxes of carbon, water and energy over Brazilian cerrado: an analysis using eddy covariance and stable isotopes

We present the energy and mass balance of cerrado sensu stricto (a Brazilian form of savanna), in which a mixture of shrubs, trees and grasses forms a vegetation with a leaf area index of 1·0 in the wet season and 0·4 in the dry season. In the wet season the available energy was equally dissipated between sensible heat and evaporation, but in the dry season at high irradiance the sensible heat greatly exceeded evaporation. Ecosystem surface conductance g_s in the wet season rose abruptly to 0·3 mol m^?2 s^?1 and fell gradually as the day progressed. Much of the total variation in g_s was associated with variation in the leaf-to-air vapour pressure deficit of water and the solar irradiance. In the dry season the maximal g_s values were only 0·1 mol m^?2 s^?1. Maximal net ecosystem fluxes of CO₂ in the wet and dry season were –10 and –15 μmol CO₂ m^?2 s^?1, respectively (sign convention: negative denotes fluxes from atmosphere to vegetation). The canopy was well coupled to the atmosphere, and there was rarely a significant build-up of respiratory CO₂ during the night. For observations in the wet season, the vegetation was a carbon dioxide sink, of maximal strength 0·15 mol m^?2 d^?1. However, it was a source of carbon dioxide for a brief period at the height of the dry season. Leaf carbon isotopic composition showed all the grasses except for one species to be C₄, and all the palms and woody plants to be C₃. The CO₂ coming from the soil had an isotopic composition that suggested 40% of it was of C₄ origin.