Feeding and growth of Asellus aquaticus (Isopoda) on food items from the littoral of Windermere, including green leaves of Elodea canadensis

SUMMARY. In the laboratory, Asellus aquaticus devoured intact green leaves from growing shoots of the aquatic macrophyte Elodea canadensis. In four collections of A. aquaticus on Elodea in a lake (Windermere), c. 20% of the specimens contained in their guts fragments of green Elodea leaves; this material and pieces of oak (Quercus) were identified from characteristic leaf hairs. Some specimens had also eaten the filamentous alga Oedogonium. Fluorescence microscopy is a useful aid for screening invertebrates that may have eaten living plant tissues. Immature A. aquaticus, with an initial mean body length of c. 3 mm, wet weight c. 1 mg, were grown through sexual maturity over a 49-day period at 15°C in a series of twenty-two experiments (six to twelve isolated specimens in each experiment) comparing growth rates on different foods, including instances where no food was given. Animals were fed on a variety of items collected from the littoral of Windermere, plus some laboratory cultures of algae and bacteria. The highest mean specific growth rate (5.8% day^?1) was obtained on young Elodea leaves mechanically shaken to remove epiphytes. Other diets yielding fast growth rates (3.7–5.3% day^?1) were young growing leaves of Elodea with few epiphytes and older green and brown living leaves covered with a thick growth of epiphytic algae, epiphytic algae removed from Elodea, plastic imitation Elodea immersed in the lake until covered with attached algae, epilithic algae on stones, Oedogonium, and decaying oak leaves. Slower growth (1.3–2.2% day^?1) and poorer survival was obtained on the following: a pure culture of the bacterium Sphaerotilus natans; cultured bacteria from lakewater; the filamentous algae Cladophora and Stigeoclonium both with and without epiphytes; faecal matter from Asellus; freshly killed Asellus; lake sediment. Some growth (mean = 0.7% day^?1) and 50% survival for 21 days occurred in ‘starved’ animals kept in filtered, sterilized lakewater. Better survival and slightly faster growth (1.0–1.5% day^?1) occurred in ‘starved’ animals kept in filtered and unfiltered lakewater. Growth of A. aquaticus was also experimentally determined from birth in animals fed on young green Elodea leaves and on decaying oak leaves. On both diets, growth was curvilinear and approximately exponential from birth to sexual maturity reached at c. 2mg wet weight in 46–60 days at 15°C. In older specimens the relative growth rate gradually fell over a period of 50 days, representing a more linear phase of growth during sexual maturity.     

Sighting frequency decreases over two decades in three populations of Testudo hermanni from central Italy

Sighting frequency of tortoises (Testudo hermanni), standardized by the number of person-hours of field effort, was studied between 1992 and 2013 at three different study areas in central Italy. Although the frequency of tortoise sightings fluctuated substantially across years and among study areas, there was a significant declining trend in all the three areas, with GLM analyses showing also a significant interaction between study area and sampling year. The decreasing trend was higher in Castel Fusano than in the other two sites, with yearly frequency of sightings being independent of search effort in all of the study areas. These trends may indicate population declines, because no other explanations seem plausible. Total rainfall from previous autumn to the study period was positively correlated to tortoise sightings in only one locality. The yearly frequency of sightings of juvenile tortoises did not vary significantly among study areas and across years, thus indicating that simple differences in detectability cannot explain the observed patterns. Summer fires and forest overgrowing seem to explain the tortoise decline in two study areas (Castel Fusano and Oriolo) whereas we were not able to identify any specific reason for tortoise decline in the third study area (Manziana).     

Food competition between 2+ tench (Tinca tinca L.), common carp (Cyprinus carpio L.) and bigmouth buffalo (Ictiobus cyprinellus Val.) in pond polyculture

Natural diets of tench (Tinca tinca L.), carp (Cyprinus carpio L.) and bigmouth buffalo (Ictiobus cyprinellus Val.) were studied to determine food competition among them in polyculture stocks of two different densities. Tench diet consisted mainly of zooplankton (43.8%) and bottom sediments (21.2%). In contrast, carp diet consisted mainly of bottom items including plant debris and detritus (68.8%), which dominated over zooplankton (19.1%). In bigmouth buffalo, most food bulk comprised zooplankton (80.7%). Thus, the resulting food competition (i.e. similarity) was most pronounced between tench and carp (60.8%) and between tench and bigmouth buffalo (47.4%). When comparing growth performance of the three cultured species, the ratios between stocking and harvesting size were: in normal stocking density (392 kg ha^?1) 1.72, 3.67 and 2.13, and in doubled stocking density (777 kg ha^?1) 1.07, 2.33 and 2.16 in tench, carp and bigmouth buffalo, respectively.     

Primary productivity studies during early years of West Point Reservoir, Alabama-Georgia

SUMMARY. 1. Phytoplankton density (organisms ml^?1), standing crop (chlorophyll a mg m^?2) and primary productivity (mg C m^?2 d^?1) were measured during years 2 (1976) to 5 (1979) after impoundment on West Point Lake. 2. West Point waters had low alkalinity (<0.4 meq 1^–1) and low conductivity (<75 μs cm^?1 at 20°C) but N and P concentrations typically exceeded those considered apt to cause nuisance blooms of algae. Abiogenic turbidity was normally higher in the upstream areas of the reservoir than in the downstream areas and was several times higher in winter-spring than in summer-autumn due to increased rains and runoff. 3. Primary productivity varied greatly both temporally and spatially. A mean value of 684 mg C m^?2 d^?1 was well within the mesotrophic range and did not approach the highly eutrophic state predicted. Productivity increased from a low of 550 mg C m^?2 d^?1 in 1976 to high of 763 mg Cm^?2d^?1 in 1979. 4. Observed variation in both chlorophyll a and primary productivity was more predictable in the cool (December-March) than in the warm (June-September) season and with plant nutrient data than without it. With plant nutrient data in the cool season 84% and 86% of the variation (R²) in chlorophyll a and productivity, respectively, were accounted for by the regression equations. During the warm season, with plant nutrient data, regression equations accounted for 44% and 68% of the variation in chlorophyll a and productivity, respectively. Higher R² values in cool seasons resulted from the overriding influence of abiogenic turbidity on phytoplankton communities.     

Effects of climatic variation on field metabolism and water relations of desert tortoises

We used the doubly labeled water method to measure the field metabolic rates (FMRs, in kJ kg^?1?day^?1) and water flux rates (WIRs, in ml H₂O?kg^?1?day^?1) of adult desert tortoises (Gopherus agassizii) in three parts of the Mojave Desert in California over a 3.5-year period, in order to develop insights into the physiological responses of this threatened species to climate variation among sites and years. FMR, WIR, and the water economy index (WEI, in ml H₂O?kJ^?1, an indicator of drinking of free water) differed extensively among seasons, among study sites, between sexes, and among years. In high-rainfall years, males had higher FMRs than females. Average daily rates of energy and water use by desert tortoises were extraordinarily variable: 28-fold differences in FMR and 237-fold differences in WIR were measured. Some of this variation was due to seasonal conditions, with rates being low during cold winter months and higher in the warm seasons. However, much of the variation was due to responses to year-to-year variation in rainfall. Annual spring peaks in FMR and WIR were higher in wet years than in drought years. Site differences in seasonal patterns were apparently due to geographic differences in rainfall patterns (more summer rain at eastern Mojave sites). In spring 1992, during an El Niño (ENSO) event, the WEI was greater than the maximal value obtainable from consuming succulent vegetation, indicating copious drinking of rainwater at that time. The physiological and behavioral flexibility of desert tortoises, evident in individuals living at all three study sites, appears central to their ability to survive droughts and benefit from periods of resource abundance. The strong effects of the El Niño (ENSO) weather pattern on tortoise physiology, reproduction, and survival elucidated in this and other studies suggest that local manifestations of global climate events could have a long-term influence on the tortoise populations in the Mojave Desert.     

Food habits of Sika deer on Mt. Goyo,northern Honshu

The food habits of Sika deer (Cervus nippon) on Mt. Goyo, northern Honshu (the main island of Japan), were studied. Among 88 plant species found in surveys, 36 species (40.9%) were eaten by the deer. The percentage frequency of feeding (F) was highest for graminoids (59.6%), followed by browses (16.6%) and ferns (7.7%) and lowest for forbs (5.4%). Though various kinds of plants were eaten, only limited species formed the bulk of the deer dietary composition.Sasa nipponica, in particular, was the most important constituent, ranking highest inF value (80.3%) and being the dominant component of feces. Fecal analyses revealed that, 1) in areas lower than 900 m in altitude,Sasa nipponica accounted for between 20 and 60% of the content and that pasture grasses were also important, and 2)S. nipponica occupied more than 50% in montane areas higher than 900 m, and even more than 80% in winter. The utilization ofS. nipponica as a forage for Sika deer was discussed. This plant can be a key forage species because it meets all the necessary conditions: abundance and stability of supply, palatability, nutritive quality and tolerance to grazing.     

Assessing Toxicant Effects in a Complex Estuary: A Case Study of Effects of Silver on Reproduction in the Bivalve,Potamocorbula amurensis,in San Francisco Bay

Contaminant exposures in natural systems can be highly variable. This variability is superimposed upon cyclic variability in biological processes. Together, these factors can confound determination of contaminant effects. Long term, multidisciplined studies with high frequency sampling can be effective in overcoming such obstacles. While studying trace metal contamination in the tissues of the clam, Potamocorbula amurensis, in the northern reach of San Francisco Bay, an episode of high Ag concentrations was identified (maximum of 5.5?µg g^?1) at two mid-estuary sites. High concentrations were not seen in clams up-estuary (maximum of 1.92?µg g^?1) from these sites and were reduced down-estuary (maximum of 2.67?µg g^?1). Silver is not common naturally in the environment, so its elevated presence is usually indicative of anthropogenic influences such as municipal and industrial discharge. Monthly sampling of reproductive status of clams characterized the reproductive cycle and differences in the patterns of reproductive activity that corresponded to changes in Ag tissue concentrations. The proportion of reproductive clams was less than 60% during periods when tissue concentrations were high (generally >2?µg g^?1). When tissue concentrations of Ag decreased (≤1?µg g^?1), the proportion of reproductive clams was 80 to 100%. A comparison between the annual proportion of reproductive clams and annual Ag tissue concentrations showed a significant negative correlation. No other measured environmental variables were correlated with reproductive impairment. The weight-of-evidence approach strongly supports a cause and effect relationship between Ag contamination and reduced reproductive activity in P. amurensis.     

The food and daily food consumption of lacustrine 0+ perch, Perca fluviatilis L.

SUMMARY.

• 1 The diet and daily food consumption (C_t) of 0+ perch were investigated in two shallow Scottish lakes.
• 2 The first food comprised the rotifer Keratella sp., Volvox sp., copepod nauplii and stage I copepodites of Cyclops strenuus abyssorum Sars. Larger copepodites and adults of C. s. abyssorum and Diaptomus gracilis Sars were consumed as larvae grew and cladocerans were also eaten by larvae >11 mm. The diet of juveniles included a wider range of cladocerans and benthic invertebrates. Cannibalism was not observed among 0+ perch.
• 3 The range of food items taken by larvae increased with length, and the size of food particles ingested was governed by jaw gape which was linearly related to fish length.
• 4 Larvae fed during daylight hours with feeding maxima in midmorning and the evening.
• 5 The arithmetic (constant) rate of evacuation R of the digestive tract of larvae was 0.59—1.16% of body weight h^?1 and exponential R was 0.21–0.33% h^?1. Daily C_t calculated using an arithmetic model was 14.2–23.4% body weight at water temperatures of 12.5–18.2°C, and 23.9–40.3% utilizing an exponential method. For larvae of 9 mm. this was 46 μg dry weight day^?1 and 148 by an exponential model. Food conversion efficiency was 37–72% (arithmetic model) and 21–45% (exponential model).

     

Contribution to the feeding ecology of the predatory wingfin anchovy Pterengraulis atherinoides (L.) in north Brazilian mangrove creeks

Stomach contents were examined from 136 Amazonian wingfin anchovy, Pterengraulis atherinoides (Engraulidae), caught from intertidal mangrove creeks at diurnal neap tides between June and September 1997 (early dry season) near Bragança (northern Brazil). The study found that P. atherinoides are specialized predators of juvenile Natantia and Teleostei (mean: 67 and 28% by dry weight, respectively). On average, 5.2 g ha^?1 day^?1 of Natantia and 2.6 g ha^?1 day^?1 of Teleostei (wet weight) were eaten by P. atherinoides. Diet changed with fish size as well as by month. While smaller sizes still fed on several food items (e.g. the copepod Pseudiaptomus marshii, the brachyuran crab Pachygrapsus gracilis, amphipods), fish >13 cm standard length (SL) fed exclusively on Natantia and Teleostei. Copepods were especially abundant in July and August, dominating the diet of fish <9 cm SL in numbers (92%). Our results suggest a positive relationship between predator size and prey size, both in penaeid and piscine prey. However, the largest predator size class apparently selected fewer but larger Teleostei prey. More than 64% of Natantia were juvenile penaeid shrimps of commercial importance (Fenneropenaeus subtilis, F. schmitti, Xiphopenaeus kroyeri). Comparison with ichthyoplankton samples taken simultaneously showed that Sciaenidae and Mugilidae were positively selected while Gobiidae and Engraulidae were negatively selected. The presence of pranzia larvae in the stomachs of fish <10 cm SL, from July onward, suggests that these sizes fulfil a mutually beneficial ‘cleaning’ function on other fish. Block net sampling at neap tides showed that P. atherinoides were present in intertidal mangrove creeks throughout the submergence period, suggesting temporal optimization of the foraging time in the eulittoral.     

Carbon fluxes, nitrogen cycling, and soil microbial communities in adjacent urban, native and agricultural ecosystems

Urban ecosystems are expanding globally, and assessing the ecological consequences of urbanization is critical to understanding the biology of local and global change related to land use. We measured carbon (C) fluxes, nitrogen (N) cycling, and soil microbial community structure in a replicated (n=3) field experiment comparing urban lawns to corn, wheat–fallow, and unmanaged shortgrass steppe ecosystems in northern Colorado. The urban and corn sites were irrigated and fertilized. Wheat and shortgrass steppe sites were not fertilized or irrigated. Aboveground net primary productivity (ANPP) in urban ecosystems (383±11 C m^?2 yr^?1) was four to five times greater than wheat or shortgrass steppe but significantly less than corn (537±44 C m^?2 yr^?1). Soil respiration (2777±273 g C m^?2 yr^?1) and total belowground C allocation (2602±269 g C m^?2 yr^?1) in urban ecosystems were both 2.5 to five times greater than any other land‐use type. We estimate that for a large (1578 km²) portion of Larimer County, Colorado, urban lawns occupying 6.4% of the land area account for up to 30% of regional ANPP and 24% of regional soil respiration from land‐use types that we sampled. The rate of N cycling from urban lawn mower clippings to the soil surface was comparable with the rate of N export in harvested corn (both ～12–15 g N m^?2 yr^?1). A one‐time measurement of microbial community structure via phospholipid fatty acid analysis suggested that land‐use type had a large impact on microbial biomass and a small impact on the relative abundance of broad taxonomic groups of microorganisms. Our data are consistent with several other studies suggesting that urbanization of arid and semiarid ecosystems leads to enhanced C cycling rates that alter regional C budgets.     

Plant and frond dynamics of the giant kelp,Macrocystis pyrifera,forming a fringing zone in the Falkland Islands

Fluctuations in plant and frond characteristics are described for Macrocystis pyrifera (L.) C. Agardh (Laminariales, Phaeophyta) forming a fringing zone in the Falkland Islands. Giant kelp plants were sampled along a transect in the austral autumn (May 1986) and late spring (December 1986) which, according to previous frond weight analysis, were the times when extremes in population parameters were expected. Plant density and holdfast wet weights were similar for both seasons, but plants had more fronds and the fronds weighed more in spring than in autumn. Consequently, in autumn the frond biomass (1·1 wet kg m^?2) and productivity (34·1 wet g m^?2 d^?1) were lower than in spring, when a biomass of 5·0 wet kg m^?2 and a productivity of 72·4 wet g m^?2 d^?1 were recorded. Production of new fronds and loss of old fronds were determined at monthly intervals between April 1986 and March 1987. New frond production rates followed fluctuations in the quantity of light and varied between 0·08 and 0·48 fronds per plant per day. Frond loss rates did not show a seasonal pattern and fluctuated between 0·05 and 0·42 fronds per plant per day. It is suggested that the Falkland Islands Macrocystis population is more stable than most other giant kelp beds at high latitudes, because of the absence of winter storms.     

Linking Belowground Carbon Allocation to Anaerobic CH4 and CO2 Production in a Forested Peatland,New York State

Heterotrophic soil microorganisms rely on carbon (C) allocated belowground in plant production, but belowground C allocation (BCA) by plants is a poorly quantified part of ecosystem C cycling, especially, in peat soil. We applied a C balance approach to quantify BCA in a mixed conifer-red maple (Acer rubrum) forest on deep peat soil. Direct measurements of CH₄ and CO₂ fluxes across the soil surface (soil respiration), production of fine and small plant roots, and aboveground litterfall were used to estimate respiration by roots, by mycorrhizae and by free-living soil microorganisms. Measurements occurred in two consecutive years. Soil respiration rates averaged 1.2 bm μmol m^{? 2} s^{? 1} for CO₂ and 0.58 nmol m^{? 2} s^{? 1} for CH₄ (371 to 403 g C m^{? 2} year^{? 1}). Carbon in aboveground litter (144 g C m^{? 2} year^{? 1}) was 84% greater than C in root production (78 g C m^{? 2} year^{? 1}). Complementary in vitro assays located high rates of anaerobic microbial activity, including methanogenesis, in a dense layer of roots overlying the peat soil and in large-sized fragments within the peat matrix. Large-sized fragments were decomposing roots and aboveground leaf and twig litter, indicating that relatively fresh plant production supported most of the anaerobic microbial activity. Respiration by free-living soil microorganisms in deep peat accounted for, at most, 29 to 38 g C m^{? 2} year^{? 1}. These data emphasize the close coupling between plant production, ecosystem-level C cycling and soil microbial ecology, which BCA can help reveal.     

Apical callus formation and plant regeneration controlled by plant growth regulators on axenic culture of the red alga Gracilariopsis tenuifrons (Gracilariales, Rhodophyta)

Axenic cultures of Gracilariopsis tenuifrons (Bird et Oliveira) Fredericq et Hommersand (Gracilariales, Rhodophyta) were established in ASP12‐NTA solid medium (0.4% agar and 1.0% sucrose) supplemented with plant growth regulators to evaluate the effects on apical callus formation and plant regeneration. Indole‐3‐acetic acid (IAA), 2,4‐dichlorophenoxyacetic acid (2,4‐D) and 6‐benzylaminopurine (BA) were added individually or in combinations (IAA : BA) over a range of concentrations from 0.5 to 5 mg L^?1. Growth of apical and intercalary segments was stimulated by high concentrations of 2,4‐D (5 mg L^?1) and a high IAA to BA ratio (IAA : BA = 5:1 mg L^?1) respectively. Apical calluses were originated from divisions of apical and cortical cells located at apical regions of thallus segments and lateral branches. Low concentration of IAA (0.5 mg L^?1) or a high IAA to BA ratio (IAA : BA = 5:1 mg L^?1) were the optimal treatments for inducing apical callus formation in apical segments, while high concentration of IAA (5 mg L^?1) stimulated the highest callus induction rate in intercalary segments. Conversely, equal parts IAA and BA (IAA : BA = 1:1 mg L^?1) and low concentration of 2,4‐D (0.5 mg L^?1) stimulated growth of apical calluses from apical and intercalary segments, respectively. Two processes of regeneration were observed: direct regeneration (upright axis originated from cells of proximal region of intercalary segments) and indirect regeneration (adventitious plantlet originated from cells of apical calluses). Direct regeneration was promoted significantly by treatment with a low IAA to BA ratio (IAA : BA= 1:5 mg L^?1), and treatments with IAA (0.5 mgL^?1) or 2,4‐D (0.5 or 5 mg L^?1) significantly stimulated the elongation of upright axis. Plant growth regulators are essential to inducing indirect regeneration, and a high concentration of IAA (5 mg L^?1) and BA (5 mg L^?1) were the optimal treatments for inducing the regeneration of plantlets from apical calluses in apical and intercalary segments, respectively. Regenerating plantlets grew into plants morphologically similar to those formed from germinating spores, and became fertile after 6 weeks. The results suggest that auxins and cytokinins are involved in developmental regulatory processes in G. tenuifrons. The regeneration process from calluses in species of Gracilariales was observed for the first time in the present study. The culture system described for G. tenuifrons could be useful for micropropagation and for biotechnological applications in agarophytic algae.     

A comparison of Acroneuria lycorias (Plecoptera) production and growth in northern Michigan hard- and soft-water streams

1. Density, biomass, production and growth of a predaceous stonefly, Acroneuria lycorias, were compared between fourth-order hard- and soft-water streams in Michigan's upper peninsula, U.S.A. 2. Mean densities, estimated from Hess samples, were higher (100 ± 17 individuals m^?2) at the hard-water site than at the soft-water site (40 ± 9 ind. m^?2). Mean dry weight biomass was 4.9 times greater at the hard-water site. 3. Mean annual production, calculated using the size frequency method, was 5.0 times greater at the hard-water site (2.18 ± 0.44 g dry weight m^?2yr^?1) than at the soft-water site (0.43 ± 0.02g dry weight m^?2yr^?1). Annual production/mean biomass ratios were similar between sites. 4. Monthly growth rates of naturally occurring nymphs of paired cohorts were similar in both streams. Individual growth rates were similar for nymphs reared in artificial streams at high and low water hardnesses with unlimited food and space. 5. Stonefly production and growth rates were influenced more by indirect physical, biological, or habitat factors than by streamwater cation concentrations.     

Assessment of heavy metal accumulation in Anzali wetland,Iran, using a submerged aquatic plant,Ceratophyllum demersum

The objective of this study in 2009 was to examine whether levels of cadmium (Cd), copper (Cu), zinc (Zn), lead (Pb) and chromium (Cr) were higher in the leaves than in the stems of a submerged aquatic plant Ceratophyllum demersum in Anzali wetland. Cadmium, Pb and Cr concentrations were highest in the leaves. The mean concentrations of Cd and Cr in the leaves at all the sampling sites ranged between 0.94–1.26 μg g^?1 and 1.03–2.71 μg g^?1, respectively. Lead also had its highest concentrations in the leaves. The mean concentration of Pb in the leaves at all sampling sites ranged between 7.49–11.88 μg g^?1. Copper and Zn concentrations were highest in the stems. The mean concentrations of Cu and Zn in the stems at all sampling sites ranged between 10.79–17.91 μg g^?1 and 19.89–40.01 μg g^?1, respectively. Cadmium and Pb concentrations were higher in the leaves than in the stems, while Zn concentration was higher in the stems than in the leaves. Accumulation of Cu and Cr in the organs of C. demersum was in descending order of leaf ～ stem, since there was no significant difference between their mean concentrations in the leaves and stems.     

Phytoextraction of Ni,Pb and,Cd by duckweeds

Abstract

Heavy metals phytoextraction potential of swollen duckweed (Lemna gibba Linn.) and lesser duckweed (Lemna aequinoctialis Welw.) was determined under greenhouse conditions by exposing to untreated industrial/municipal effluent for a period of 21?days. The nickel (Ni), lead (Pb), and cadmium (Cd) concentrations in water samples were measured weekly and in plant biomass at the termination of experiments. Significant differences (p?<?0.05) between initial and final physicochemical parameters and in heavy metal concentrations of plant and water samples were observed. Periodically measured metal concentrations in mediums revealed that removal percentage was dependent on initial Ni (2.15?mg L^?1), Pb (1.51?mg L^?1), and Cd (0.74?mg L^?1) concentrations. The final metal removal percentages were in the sequence of Ni (97%) > Pb (94%) > Cd (90%) when treated with Lemna gibba L. as compared to control (9–12% reduction). High biomass production of Lemna gibba L. resulted in a large metal reduction in the growth medium and the total plant metal contents were in the sequence of Ni (427?µg) > Pb (293?µg) > Cd (105?µg). The lesser duckweed did not survive under experimental conditions. Based on these results, we concluded that Lemna gibba L. is a good candidate for phytoremediation of wastewater.     

Observations of floating anthropogenic litter in the Barents Sea and Fram Strait,Arctic

Although recent reports indicate that anthropogenic waste has made it to the remotest parts of our oceans, there is still only limited information about its spread, especially in polar seas. Here, we present litter densities recorded during ship- and helicopter-based observer surveys in the Barents Sea and Fram Strait (Arctic). Thirty-one items were recorded in total, 23 from helicopter and eight from research vessel transects. Litter quantities ranged between 0 and 0.216 items km^?1 with a mean of 0.001 (±SEM 0.005) items km^?1. All of the floating objects observed were plastic items. Litter densities were slightly higher in the Fram Strait (0.006 items km^?1) compared with the Barents Sea (0.004 items km^?1). More litter was recorded during helicopter-based surveys than during ship-based surveys (0.006 and 0.004 items km^?1, respectively). When comparing with the few available data with the same unit (items km^?1 transect), the densities found herein are slightly higher than those from Antarctica but substantially lower than those from temperate waters. However, since anthropogenic activities in the Fram Strait are expanding because of sea ice shrinkage, and since currents from the North Atlantic carry a continuous supply of litter to the north, this problem is likely to worsen in years to come unless serious mitigating actions are taken to reduce the amounts of litter entering the oceans.     

Carbon storage and fluxes in ponderosa pine forests at different developmental stages

We compared carbon storage and fluxes in young and old ponderosa pine stands in Oregon, including plant and soil storage, net primary productivity, respiration fluxes, eddy flux estimates of net ecosystem exchange (NEE), and Biome‐BGC simulations of fluxes. The young forest (Y site) was previously an old‐growth ponderosa pine forest that had been clearcut in 1978, and the old forest (O site), which has never been logged, consists of two primary age classes (50 and 250 years old). Total ecosystem carbon content (vegetation, detritus and soil) of the O forest was about twice that of the Y site (21 vs. 10 kg C m^?2 ground), and significantly more of the total is stored in living vegetation at the O site (61% vs. 15%). Ecosystem respiration (R_e) was higher at the O site (1014 vs. 835 g C m^?2 year^?1), and it was largely from soils at both sites (77% of R_e). The biological data show that above‐ground net primary productivity (ANPP), NPP and net ecosystem production (NEP) were greater at the O site than the Y site. Monte Carlo estimates of NEP show that the young site is a source of CO₂ to the atmosphere, and is significantly lower than NEP(O) by c. 100 g C m^?2 year^?1. Eddy covariance measurements also show that the O site was a stronger sink for CO₂ than the Y site. Across a 15‐km swath in the region, ANPP ranged from 76 g C m^?2 year^?1 at the Y site to 236 g C m^?2 year^?1 (overall mean 158 ± 14 g C m^?2 year^?1). The lowest ANPP values were for the youngest and oldest stands, but there was a large range of ANPP for mature stands. Carbon, water and nitrogen cycle simulations with the Biome‐BGC model suggest that disturbance type and frequency, time since disturbance, age‐dependent changes in below‐ground allocation, and increasing atmospheric concentration of CO₂ all exert significant control on the net ecosystem exchange of carbon at the two sites. Model estimates of major carbon flux components agree with budget‐based observations to within ± 20%, with larger differences for NEP and for several storage terms. Simulations showed the period of regrowth required to replace carbon lost during and after a stand‐replacing fire (O) or a clearcut (Y) to be between 50 and 100 years. In both cases, simulations showed a shift from net carbon source to net sink (on an annual basis) 10–20 years after disturbance. These results suggest that the net ecosystem production of young stands may be low because heterotrophic respiration, particularly from soils, is higher than the NPP of the regrowth. The amount of carbon stored in long‐term pools (biomass and soils) in addition to short‐term fluxes has important implications for management of forests in the Pacific North‐west for carbon sequestration.     

Comparative Evaluation of Metal Phytoremediation Potential of Trees,Grasses, and Flowering Plants from Tannery-Wastewater-Contaminated Soil in Relation with Physicochemical Properties

This study reports a comparative account of metal accumulation in the trees, grasses, and flowering plants from agricultural fields contaminated with tannery wastewater. Soil physico-chemical properties along the pollution gradient and soil depth were analyzed. Monitoring and assessment of the plants growing on contaminated sites revealed that the accumulation of Cr in the aboveground part of the trees ranged from 1.87 to 34.44 μg g^?1 dw with maximum concentration in Dendro-calamus strictus (34.44 μg g^?1 dw). Chrysanthemum coronarium and Tagetes erecta showed better accumulation of Cr than other flowering plants. Separate field experiments were conducted on the contaminated area. The shoots of Vetiveria zizanoides (532 mg 4 m^?2) and Cymbopogan winterianus (535.46 mg 4 m^?2) have shown almost similar removal potential of Cr, with maximum removal potential in the roots of C. winterianus (1206.43 mg 4 m^?2). Seasonal flowering plants (i.e., C. coronarium) have shown better accumulation of Cr than T. erecta. The results indicate that the plants of V. zizanoides, C. coronarium, and C. winterianus are suitable for phytoremediation of contaminated sites and trees can successfully be used for phytostabilization.     

Diet and consumption rates of common dolphinfish,Coryphaena hippurus,in the eastern Arabian Sea

The aim of the study was to identify the diet composition, feeding preferences, size and sex related diet changes, and to calculate the consumption rates of common dolphinfish, Coryphaena hippurus, in the eastern Arabian Sea. Fish were caught using longline gear during the years 2006–2009. Stomachs of 238 specimens with fork lengths ranging from 324 to 1250 mm were analysed; 72 (30.25%) of the stomachs were empty. Epipelagic finfishes were the predominant prey followed by cephalopods and crustaceans. Occurrence of items such as sargassum, sea fans, corals, plastics and pieces of wood in the stomachs indicate an opportunistic and voracious feeding nature. Flyingfishes (family Exocoetidae), especially Exocoetus monocirrhus (%IRI 16.92), dominated the diet. Unidentified filefishes (family Monacanthidae), Sthenoteuthis oualaniensis, Euthynnus affinis, Cheilopogon furcatus and Cubiceps pauciradiatus were other important food items. The diet varied between sexes and different size classes. Juveniles and adults (size classes <75 cm, 75–95 and 95–115 cm) fed mainly on epipelagic finfishes, whereas the large adults (>115 cm) fed preferentially on cephalopods. Food consumption rate was higher in females (6.37% BW day^?1) compared to males (4.04% BW day^?1), and increased with their increase in size up to 75–95 cm length classes, thereafter decreasing. The daily meal and daily ration was 332.63 g day^?1 and 5.25% BW day^?1, respectively, and average annual food consumption was 121.41 kg.