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     

Territory and group sizes in Eurasian beavers (Castor fiber): echoes of settlement and reproduction?

According to current theories of territoriality, an animal is expected to defend the smallest area that can provide resources for maximisation of reproduction, known as the economically defendable area. In group territorial species however, the strategies behind resource defence are likely to be more complex with corporate territoriality, cooperative breeding, delayed dispersal and intra-group competition all potentially playing a role. Here we examined group territoriality in a social herbivorous rodent, the Eurasian beaver Castor fiber. Beavers in our study do not inhabit economically defendable territories. Instead the sequence of arrival of pairs into unoccupied areas seems to play a more important role in determining the size of the territory, whereas group size is determined by past reproductive success. We argue that the settlement pattern and reproductive history have a lasting impact in the territorial system of beavers due to a combination of the low adult mortality, high dispersal costs, and avoidance of resource depletion.R.D. Campbell and F. Rosell contributed equally to this work     

Growth dynamics of Saccharina latissima (Laminariales,Phaeophyceae) in Aarhus Bay,Denmark, and along the species’ distribution range

Growth dynamics of Saccharina latissima in a Danish embayment (56°03.793N, 10°16.148E) were investigated through an annual cycle (March 1999–March 2000) and related to patterns found in previous studies covering the distribution range of the species. The kelps exhibited meristematic growth as well as distal tissue loss all year around. Elongation rate peaked in spring (March–May, 0.75 cm day^?1), whereas maximum biomass growth occurred in May–July at higher insolation. S. latissima accumulated nitrogen (N) in November–March, when ambient N levels were high and the fast growth in March–July was followed by a depletion of these reserves. Light regimes and seasonal fluctuations of nutrients were, thus, major factors explaining the seasonal growth pattern of S. latissima in this temperate bay. Differences in light and exposure along depth gradients affected the growth, loss and storage product dynamics. High losses of N and carbon (C) through summer abscission of distal tissue question the efficiency of translocation, especially at shallower depths, where losses are accelerated by, e.g., high temperature. A large-scale comparison further highlighted that warming advanced the timing, increased the level of peak growth and also seemed to expand the growth period. Growth rates of the studied Danish population fell in the low end of the range for similar latitudes and temperatures, probably due to sub-optimal salinities (avg. 23.3 psu) in combination with periodically high summer temperatures (max. 21.1 °C).     

Acute toxicity of waterborne manganese to Rutilus caspicus (Yakovlev, 1870) – gill histopathology,immune indices,oxidative condition,and saltwater resistance

The acute toxicity of manganese (Mn) in Caspian roach Rutilus caspicus was determined. The 96 h-LC₅₀ was calculated to be 300 (240–360) mg L^?1. Then, fish were exposed for 96 h to 300 (96 h-LC₅₀), 150 (50% of 96 h-LC₅₀), 60 (20% of 96 h-LC₅₀), and 0 (control group) mg L^?1 Mn. Exposure to all Mn concentrations led to fish gill damages, including epithelial lifting, hyperplasia, lamellar fusion, aneurism, and lamellar curling. Also, the fish exposed to all Mn concentrations showed decreased plasma alternative complement and lysozyme activity. Whole body superoxide dismutase, catalase, and malondialdehyde showed significant increases in the Mn-exposed fish which also exhibited lower tolerance to saltwater than the control group.     

Echolocation behavior and signal plasticity in the Neotropical bat Myotis nigricans (Schinz, 1821) (Vespertilionidae): a convergent case with European species of Pipistrellus?

We used both field and flight cage observations to investigate the echolocation and foraging behavior of the seldom studied, small, aerial insectivorous bat Myotis nigricans (Vespertilionidae) in Panama. In contrast to its temperate congeners, M. nigricans foraged extensively in open space and showed an echolocation behavior well adapted to this foraging habitat. It broadcast narrowband echolocation signals of 7 ms duration that enhance the chance of prey detection in open space. Because of rhythmical alternations of signal amplitude from signal to signal in our sound recordings of search signals in open space, we conclude that the bats scanned their environment with head movements, thereby enlarging their search volume. In edge-and-gap situations, and in the flight cage, M. nigricans introduced an initial broadband component to its search calls. In the field and in the flight cage, M. nigricans hawked for prey in aerial catches; gleaning was never observed. M. nigricans demonstrates call structures, such as narrow bandwidth and rather long signals adapted to foraging predominantly in open space. Moreover, call structure is highly plastic, allowing M. nigricans to forage in edge-and-gap situations also. These adaptations in call structure and plasticity have evolved convergently at least twice within the genus Myotis. Finally, M. nigricans echolocation and foraging behavior parallels that of the small, aerial, insectivorous pipistrelle bats (Vespertilionidae), which are not closely related to M. nigricans but forage in similar habitats.     

Reef coral reproduction in the eastern Pacific: Costa Rica,Panamá, and Galápagos Islands (Ecuador). III. Agariciidae (Pavona gigantea and Gardineroseris planulata)

The reproductive ecology of Pavona gigantea Verrill and Gardineroseris planulata (Dana) was investigated in the equatorial eastern Pacific region from 1985 to 1994. These zooxanthellate scleractinian corals were adversely affected in this region during the 1982–1983 El Niño warming event. Both species were hermaphroditic, with individual colonies showing sequential cosexual development, thus resulting in dominantly outbreeding reproduction. Sexuality was mixed, with high percentages of gonochoric and hermaphroditic colonies in both species. Approximately 1:1 male-to-female gonad ratios were found in gonochoric and hermaphroditic colonies combined. Broadcast spawning was observed in P. gigantea in the Galápagos Islands, and the sudden disappearance of mature gametes and the presence of spent gonads suggest that G. planulata is also a broadcast spawner. Colonies of both species with 200 cm² (10 cm diam) live tissue were nonreproductive. Estimated ages of the youngest reproductive colonies were 11 yr for P. gigantea and 20 yr for G. planulata. The percentage of all colonies of P. gigantea with gonads at nonupwelling sites (Caño Istand, Costa Rica and Uva Island, Panamá) ranged from 37 to 47%, respectively; colonies with gonads from upwelling environments (Saboga and Taboga Islands, Panamá) ranged from 31 to 39%, respectively, and reproductively active colonies from the thermally variable Galápagos islands comprised 40% of the collections. Compared with P. gigantea, the numbers of sexually active G. planulata colonies were roughly onehalf at nonupwelling Caño Island (20%) and Uva Island (25%) sites, or less (10%) at the upwelling Saboga Island site. Peak reproductive activity in P. gigantea occurred during the rainy season at all study sites. In the nonupwelling Costa Rican (Caño Island) and Panamainan (Uva Island) sites, mean monthly sea-surface temperatures (SSTs) were high (28 to 29°C), but slightly lower than in the dry season (29°C). In the upwelling Gulf of Panamá (Saboga and Taboga Islands), reproduction occurred after mean monthly SSTs increased from 24 to 28–29°C. In the Galápagos Islands, reproductive activity peaked during sea warming, when mean monthly SSTs reached 25°C. Sexually active colonies of G. planulata, present only at the main collection sites of Caño and Uva Islands, were also observed during the wet season. The presence of mature or spawned gonalds in both species mostly around new and full lunar phases suggests that spawning is at least weakly synchronized with moon phase. Fecundity estimates disclosed the following nonsignificant differences between sites for P. gigantea, expressed as egg production cm^-2 colony surface surface yr^-1: Galápagos (10 300 to 30 800), Uva Island (4900 to 9800), Caño Island (1800 to 7400), Saboga Island (600 to 1300) Taboga Island (1200 to 2400). Fecundity estimates for G. planulata were considerably lower: Uva Island (700 to 1400), Caño Island (500 to 1000). The sexual recruitment of P. gigantea into El Niño-Southern Oscillation (ENSO) 1982–1983-disturbed, equatorial eastern Pacific coral communities has been low, with only moderate recovery evident since 1983. G. planulata has revealed no sexual recruitment where seed populations are absent or rare (Caño Island, Galápagos Islands), and only low recruitment (Panamá) in areas with colonies that survived the ENSO disturbance.     

Phylogeographic pattern and glacial refugia of a rocky shore species with limited dispersal capability: the case of Montagu’s blenny (Coryphoblennius galerita,Blenniidae)

Phylogeographic patterns among coastal fishes are expected to be influenced by distinct ecological, biological and life history traits, along with historical events and oceanography (past and present). This study focuses on the broad range phylogeography of the Montagu’s blenny Coryphoblennius galerita, a species with well-known ecological features, strictly tied to rocky environments and with limited dispersal capability. Eleven locations from the western Mediterranean to the Bay of Biscay (including the Macaronesian archipelagos) were sampled. Mitochondrial DNA control region (CR) and the first intron of the S7 ribosomal protein gene were used to address the population structure, the signatures of expansion/contraction events retained in the genealogies and potential glacial refugia. The genetic diversity of the Montagu’s blenny was high throughout the sampled area, reaching maximum values in the Mediterranean and western Iberian Peninsula. The results confirmed a marked structure of C. galerita along the sampled area, with a major separation found between the Mediterranean and the Atlantic populations, and suggesting also a separation between the Azores and the remaining Atlantic locations. This study revealed complex and deep genealogies for this species, with Montagu’s blenny populations presenting signatures of events clearly older than the Last Glacial Maximum, with lineages coalescing in early Pleistocene and Pliocene. Three potential glacial refugia where this species might have survived Pleistocene glaciations and from where the recolonization process might have taken place are suggested: South of Iberian Peninsula/North Africa, Mediterranean and Azores.     

Reproductive biology and population structure of the sea cucumber <Emphasis Type="Italic">Isostichopus fuscus</Emphasis> (Ludwig, 1875) (Holothuroidea) in Caamaño,Galápagos Islands,Ecuador

Pre-spawning reproductive biology and population structure of the sea cucumber Isostichopus fuscus were analysed at the Caamaño Island, Galápagos Islands, Ecuador on a monthly basis between January 1995 and June 1996. An average of 25 individuals of all sizes were collected each month. Using microscopic characteristics of the gonads three gonadal stages were described: (1) immature; (2) mature, and (3) spent. Mature individuals showed statistically different morphometric characteristics. I. fuscus was continuously sexually mature throughout the year independent of changes in sea water temperature. Mean oocyte diameter indicated planktotrophic larval development. Mean fecundity for this species was 567,884 (±95,528 SE) eggs per gonad. Size at first maturity was between 161.0 and 170.9 g drained weight and the smallest individual found with mature gonads had a drained weight between 121.0 and 130.9 g. The population sampled ranged between 13 and 31 cm (81.0–400.0 g) with less than 10% of the population of individuals ≥25 cm (≥300.0 g). No juveniles were recorded.     

Microbiological degradation of polycyclic aromatic hydrocarbons: Anthracene,benzo(K)fluoranthene,dibenzothiophene, benzo(H) quinoline and 2‐nitronaphthalene

Biodegradation experiments of various polycyclic aromatic hydrocarbons were studied with mixed bacteria culture under aerobic conditions. An easy‐to‐handle clean‐up procedure was developed for PAH and their metabolites simultaneously as well as a gc‐ms‐method to identify and quantify these compounds.

Anthracene and dibenzothiophene are completely degradable in an aqeous system, whereas biodegradation of benzo(k)fluoranthene and benzo(h)quinoline is possible only in an oil‐in‐water‐system with dodecane as cosubstrate. No degradation of nitronaphthalene was observed in aqueous systems. New metabolites are 2,3‐dihydroxybenzothiophene, hydroxybenzothiophenecarbonic acid and benzothiophenequinone for dibenzothiophene and hydroxyfluoranthenic acid for benzo(k)flouranthene. Whereas the former metabolites are degradable under the experimental conditions, the latter accumulates during the degradation experiment.

The results are important for microbiological wastewater treatment, since knowledge of biodegradation processes is indespensable for the successful treatment of PAH‐containing wastewater.     

Stable isotopes (δ13C, δ15N) and modelling as tools to estimate the trophic ecology of cultivated oysters in two contrasting environments

Food sources for cultivated marine bivalves generally are not well identified, although they are essential for a better understanding of coastal ecosystems and for the sustainability of shellfish farming activities. In addition to phytoplankton, other organic matter sources (OMS), such as microphytobenthos and detritus (of terrestrial or marine origins), can contribute significantly to the growth of marine bivalves. The aim of this study was to identify the potential food sources and to estimate their contributions to the growth of the Pacific oyster (Crassostrea gigas) in two contrasting trophic environments of Normandy (France): the Baie des Veys (BDV) and the Lingreville area (LIN). Two sites were studied in the BDV area (BDV-S and BDV-N) and one in the LIN area. To estimate the contribution of each type of OMS, we used a combination of stable natural isotope composition (δ¹³C, δ¹⁵N) analysis of OMS and oyster tissue together with a modelling exercise. Field sampling was conducted every 2 months over 1 year. The sampled sources were suspended particulate organic matter from marine (PhyOM) and terrestrial (TOM) origins, microphytobenthos (MPB), detrital organic matter from the superficial sediment (SOM), and macroalgae (Ulva sp., ULV). A statistical mixing model coupled to a bioenergetic model was used to calculate the contributions of each different source at different seasons. Results showed that isotopic composition of the animal flesh varied with respect to the potential OMS over the year within each ecosystem. Significant differences were also observed among the three locations. For instance, the δ¹³C and δ¹⁵N values of the oysters ranged from −20.0 to −19.1‰ and from 6.9 to 10.8‰ at BDV-S, from −19.4 to −18.1‰ and from 6.4 to 10.0‰ at BDV-N, and from −21.8 to −19.4‰ and from 6.3 to 8.3‰ at LIN. The contributions of the different sources to oyster growth differed depending on the ecosystem and on the period of the year. Phytoplankton (PhyOM) predominated as the principal food source for oysters (particularly in the LIN location). MPB, TOM, and ULV detritus also possibly contributed to oysters’ diet during summer and autumn at the BDV-S and BDV-N sites. SOM was not considered an OMS because it was already a mix of the other four OMS, but rather a trophic reservoir that potentially mirrored the trophic functioning of marine ecosystems.     

Hydrochemical and radiometric evaluation of fresh and thermal waters from Araxá city (Minas Gerais,Brazil)

Environmental Geochemistry and Health - This paper reports the hydrochemistry and activity concentration of the natural radionuclides 238U, 234U, and 210Po for three compartments of the...     

Synthesis and antifungal property of N,N′-bis(trans-cinnamaldehyde)-1,2-diiminoethane and its derivatives

N,N′-bis(trans-cinnamaldehyde)-1,2-diiminoethane and its derivatives were designed and synthesized. Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (¹H-NMR) techniques were applied to characterize chemical structures, and the filter paper disk method was used to test for antifungal effect of the products against Aspergillus niger, Paecilomyces variotii, and Paecilomyces lilacinus. Chemical structure charaterization showed that the products are target compounds. Antimicrobial experiment results indicated that N,N′-bis(trans-cinnamaldehyde)-1,2-diiminoethane displayed reliable antifungal effects against three fungi, and its antifungal effect is close to that of cinnamaldehyde. N,N′-bis(p-methoxy cinnamaldehyde)-1,2-diiminoethane and N,N′-bis(p-chlorocinnamaldehyde)-1,2-diiminoethane also showed antifungal effects at a low concentration. Of the two, N,N′-bis(p-methoxy cinnamaldehyde)-1,2-diiminoethane appeared to be more suitable as it was more effective at higher concentrations against Paecilomyces.     

Morphological, physiological and reproductive conditions of rafting bull kelp (Durvillaea antarctica) in northern-central Chile (30°S)

The bull kelp Durvillaea antarctica is a common floating alga in the southern hemisphere, but despite the ecological and biogeographic importance of kelp rafts, little is known about the responses of detached kelps to the conditions at the sea surface. The morphological, physiological and reproductive performances of D. antarctica rafts in the Coastal System of Coquimbo, Chile (CSC, ~30°S), were examined during winter and summer of two successive years (2010/11 and 2011/12). Epibionts (Lepas spp.) that only attach to floating objects were used as indicator for the floating time of kelp rafts. Photosynthetic efficiency and reproductive maturity of both benthic and floating algae varied seasonally, with a stronger decrease in summer than in winter. Blade size (measured as weight proportion of kelp individuals), phlorotannin concentrations and antioxidant activities were lower in floating than in benthic algae. Environmental conditions and floating time affected the blade tissues, with stronger negative effects during summer. These results confirm that floating persistence of D. antarctica in the CSC is suppressed during the summer months, which indicates that the dispersal potential of this (and other) floating algae varies seasonally.     

Characterization of the lignin signature in Lake Mead,NV, sediment: comparison of on-line flash chemopyrolysis (600°C) and off-line chemolysis (250°C)

The distribution of lignin in sediment is a useful tool for tracing the transport of land-derived organic matter in an aquatic environment. Tetramethylammonium hydroxide (TMAH) flash chemopyrolysis, or chemolysis followed by GC–MS analysis can be used for evaluating the origin of organic carbon in sediments. TMAH chemopyrolysis or chemolysis of organic matter produces a myriad of semi-volatile products. Among these products are methylated phenols which are an indirect measure of lignin in sediment. In this study, total organic carbon, elemental carbon, and lignin were measured in Lake Mead sediments. This study indicates that terrestrial runoff makes a contribution to Lake Mead sediments, and that this contribution is most apparent in sediment that is close to the Las Vegas Wash. Two chemolysis methods (on-line and off-line) were examined and compared for detection of lignin phenols. The results from these sediment cores indicate that comparable results can be obtained from the two approaches, although detection levels are significantly lower for the off-line approach.     

Study of atmospheric electrical conductivity,SO2, NO2, aerosols SPM (>10 μ) and RSPM (<10 μ) in Mysore city,India

It is well known that atmospheric electrical conductivity is mainly due to the presence of small ions. Near the surface of the earth, radon and its daughter products predominantly produce small ions. In the presence of aerosol particles, the small ion concentration is reduced due to attachment of small ions to aerosol particles which decreases mobility and conductivity in the atmosphere. The ion pair production rate is estimated from the measured radon and its progeny concentrations and correlated with electrical conductivity of the atmosphere. Measurement of concentrations of suspended particulate matter (SPM), SO₂, and NO₂ of air was also carried out. Data showed that reduced electrical conductivity was related to concentration of airborne SPM.     

Reproduction and growth of Isostichopus fuscus (Echinodermata: Holothuroidea) in the southern Gulf of California, México

The reproduction and growth of Isostichopus fuscus (Ludwig, 1875) at Isla Espíritu Santo, Baja California Sur, México from July 1992 to September 1993 and from August 1996 to July 1997 were analyzed. The reproductive cycle was monitored by using histological analysis. Five gonadal stages were described according to cell types present in the gonad; undetermined, gametogenesis, maturity, spawning and post-spawning. This holothurian reproduces annually during summer (July to September), when sea surface temperature reaches 27 °C. The gonad index is related to the gonadal stages. The first sexual maturity for I. fuscus was calculated at 367 g (4 to 5 years old) according to the von Bertalanffy equation, and nearly all the specimens at Isla Espíritu Santo were 5 to 7 years old (including some individuals over 35 years old). Data of the length–weight relationship showed that I. fuscus grows allometrically at the studied site (b = 1.83). The mortality rate was relatively high (M = 0.51), indicating that in a typical cohort, 40% of the recruits does not survive the first year, and less than 20% reaches maturity. Received: 15 July 1998 / Accepted: 19 August 1999     

Si对盐胁迫下水稻根系活力、丙二醛和营养元素含量的影响(Effects of Si on the Index of Root Activity, MDA Content and Nutritional Elements Uptake of Rice under Salt Stress)

为深入了解盐胁迫下外源硅(Si)对水稻生长的作用,采用溶液培养法研究了外源Si对盐(NaCl)胁迫下野生型水稻和硅突变体水稻(不能正常吸收Si)营养元素和生理指标的影响.结果表明:1)外源Si可显著提高盐胁迫下两种水稻的生物量.当NaCl的浓度为100mmol·L-1时,添加1.0mmol·L-1的Si可使野生型水稻茎叶和根系干重提高12.81%和15.25%,硅突变体水稻茎叶干重提高12.31%.2)外源Si可提高盐胁迫下两种水稻茎叶和根系中营养元素含量,降低Na的含量.3)外源Si可显著降低盐胁迫下野生型水稻叶片MDA含量,但对突变体水稻叶片MDA含量影响不大.4)外源Si可显著提高盐胁迫下两种水稻的根系活力.盐胁迫下,与不加Si的对照相比,添加1.0mmol·L-1的Si可分别使野生型和突变体水稻根系活力指数提高60.47%和42.42%.