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1.
Arctic ecosystem dynamics are shifting in response to warming temperatures and sea ice loss. Such ecosystems may be monitored by examining the diet of upper trophic level species, which varies with prey availability. To assess interannual variation in the Beaufort Sea ecosystem, we examined spatial and temporal trends in ringed seal (Pusa hispida) δ13C and δ15N in claw growth layers grown from 1964 to 2011. Stable isotopes were correlated with climate indices, environmental conditions, seal population productivity, and geographic location. Sex and age did not influence stable isotopes. Enriched 13C was linked to cyclonic circulation regimes, seal productivity, and westward sampling locations. Higher δ15N was linked to lower sea surface temperatures, a higher percentage of pups in the subsistence harvest, and sample locations that were eastward and further from shore. From the 1960s to 2000s, ringed seal niche width expanded, suggesting a diversification of diet due to expansion of prey and/or seal space use. Overall, trends in ringed seal stable isotopes indicate changes within the Beaufort Sea ecosystem affected by water temperatures and circulation regimes. We suggest that continued monitoring of upper trophic level species will yield insights into changing ecosystem structure with climate change.  相似文献   

2.
Spore formers were detected in samples of calcareous crust with manganiferous laminations and in water from the Dead Sea in Israel. They were able to grow in media made with fresh water but not with synthetic Dead Sea water. Some of these spore formers were also able to oxidize Mn (II) in fresh water. No other bacteria capable of both growth and Mn(II) oxidation in hypersaline media prepared with synthetic Dead Sea water were found in the samples. However, bacteria capable of growth and Mn(II) oxidation in fresh water media were detected in water and sediment from fresh water springs at Ein Feshkha and in lake water and sediment from the beach near Wadi Kidron. Both sites are located on the western shore of the lake. These findings suggest that the manganiferous laminations in calcareous crusts and concretions in the Dead Sea along its western shore may have originated, at least in part, from manganese oxide formed by bacteria in fresh water environments on shore and washed into the lake in runoff, with subsequent incorporation into the crusts and concretions.  相似文献   

3.
Pannacciulli  F. G.  Relini  G. 《Hydrobiologia》2000,426(1):105-112
The Mediterranean Sea is characterised by a small tidal range (0.3–1 m). Despite this, intertidal communities are well established and their upper limits often extend above mean high water level. Organisms living in the intertidal region and in the supralittoral zone rely on both tides and wave action to perform their biological functions. Lack of food, desiccation and predation are common stresses in such a harsh environment. The present study deals with the vertical distribution of two species of intertidal barnacles, Chthamalus montagui Southward and Chthamalus stellatus (Poli), which are the main constituents of the barnacle belt along Mediterranean rocky shores. Previous work, carried out in the Atlantic, showed that where the distribution ranges of the two Chthamalus species overlap, C. montagui is more common in the upper barnacle zone while C. stellatus is dominant lower down. The main aims of our study are: (1) to establish if there is a relationship between position and extension of the barnacle belt on the shore and tidal range and/or wave exposure, (2) to test the hypothesis that in the study areas C. montagui is more abundant than C. stellatus high on the shore, and that the pattern is reversed lower down. Barnacle populations were monitored in summer 1998 in the Gulf of Genoa (Ligurian Sea) and in the Gulf of Trieste (North-Adriatic Sea). The two areas differ in tidal range and hydrodynamism, the former presenting quite strong wave action and a tidal range of 30 cm, the latter having limited wave action and 1 m tidal range. Three shores were randomly selected in each gulf and two transects on each shore. Counts of barnacles in 10 * 10 cm quadrats were done at different shore heights along each transect. The data was subjected to analysis of variance. Results showed that a more pronounced hydrodynamic regime corresponded to a shift of the barnacle belt towards the higher shore (Gulf of Genoa), while in more sheltered areas (Gulf of Trieste), the barnacle distribution was confined to the intertidal region. The relative spatial distribution of C. montagui and C. stellatus within the barnacle belt varied locally, even between transects on the same shore, and this obscured the distribution pattern along the vertical gradient. Nevertheless, it was still possible to conclude that at mid and high shore in Genoa, C. stellatus was more abundant than C. montagui, while in Trieste the pattern was reversed.  相似文献   

4.
This study presents data on the distribution of the palynofacies assemblages during the last 1500 years in sediments from Greenland and Faroe Islands fjords and North Atlantic deep-water sites. The sediments studied consist of olive grey to brown muddy silt occasionally mottled and faintly laminated. The chronology is based on 210Pb and 137Cs measurements and Accelerator Mass Spectrometry 14C dating of shells and plant remains. As a result, the distribution of particulate organic matter at the high latitudes is controlled by the distance from the shore and water depth. Changes in water depth do not affect the assemblages near the shore. In order to provide a tool using palynofacies analysis for assessing high-latitude depositional settings, we propose to revise the palynological model of Tyson (1993). The revised model is a ternary plot of the relative amount of (1) amorphous organic material, (2) phytoclasts +sporomorphs, and (3) foraminifera + dinoflagellates +acritarchs +other marine algae in the sediment. Based on the integration of quantitative palynofacies analysis and environmental data, the revised model has the potential for discriminating spatial and redox status differences and providing information about terrestrial/fresh water influx at the high latitudes.  相似文献   

5.
Foraging herbivores have to trade-off between energy requirements and predator avoidance. We aimed to study the relative roles of these factors in beavers (Castor canadensis) when foraging on land. We hypothesized that beavers were able to assess the risk of predation by using two main cues: the distance from the water and the presence or absence of predator odors. First, we studied the food selection of beavers in relation to distance from the water in natural settings. The transects were made at beaver ponds, and the diameter, species, and distance from the shore of intact and beaver-cut trees were recorded. Secondly, we placed rows of aspen sticks (Populus tremula) perpendicular to the shore around beaver ponds, and treated each row with a neutral, alien, or wolf odor. We found that aspen, downy birch (Betula pubescens), and speckled alder (Alnus incana) were the preferred tree species. More of these species were cut close to the shore, and cut trees were smaller further away from the shore, except in the case of aspen. In the experiment, most of the aspen sticks were taken close to the shore. As predicted, beavers took less aspen sticks in rows treated with wolf odor than water. As the predator odor did not affect the foraging distance from the shore, it is likely that our observation that foraging was the most intense close to shore is due to energetic constraints. However, predation risk probably affects the decision whether to forage on the land in the first place.  相似文献   

6.
Microbiological, biogeochemical, and isotopic geochemical investigation of Lake Kislo-Sladkoe (Polusolenoe in early publications) at the Kandalaksha Bay shore (White Sea) was carried out in September 2010. Lake Kislo-Sladkoe was formed in the mid-1900s out of a sea gulf due to a coastal heave. At the time of investigation, the surface layer was saturated with oxygen, while near-bottom water contained sulfide (up to 32 mg/L). Total number of microorganisms was high (12.3 × 106 cells/mL on average). Light CO2 fixation exhibited two pronounced peaks. In the oxic zone, the highest rates of photosynthesis were detected at 1.0 and 2.0 m. The second, more pronounced peak of light CO2 fixation was associated with activity of anoxygenic phototrophic bacteria in the anoxic layer at the depth of 2.9 m (413 μg C L?1 day?1). Green-colored green sulfur bacteria (GSB) predominated in the upper anoxic layer (2.7–2.9 m), their numbers being as high as 1.12 × 104 cells/mL, while brown-colored GSB predominated in the lower horizons. The rates of both sulfate reduction and methanogenesis peaked in the 2.9 m horizon (1690 μg S L?1 day?1 and 2.9 μL CH4 L?1 day-1). The isotopic composition of dissolved methane from the near-bottom water layer (δ13C (CH4) = ?87.76‰) was significantly lighter than in the upper horizons (δ13C (CH4) = ?77.95‰). The most isotopically heavy methane (δ13C (CH4) = ?72.61‰) was retrieved from the depth of 2.9 m. The rate of methane oxidation peaked in the same horizon. As a result of these reactions, organic matter (OM) carbon of the 2.9 m horizon became lighter (?36.36‰), while carbonate carbon became heavier (?7.56‰). Thus, our results demonstrated that Lake Kislo-Sladkoe is a stratified meromictic lake with active microbial cycles of carbon and sulfur. Suspended matter in the water column was mostly of autochthonous origin. Anoxygenic photo-synthesis coupled to utilization of reduced sulfur compounds contributed significantly to OM production.  相似文献   

7.
ABSTRACT Quantifying the factors influencing behaviors of aquatic mammalian grazers may enhance the generic understanding of grazer ecology. We investigated diel and tidal patterns in movements of the dugong (Dugong dugon) by Global Positioning System—tracking 12 animals in 5 inshore—intertidal and 3 offshore—subtidal habitats along the coast of Queensland, Australia. We examined effects of tide height and time of day on the dugong's distance from 1) the nearest coast, 2) water >3 m deep, 3) actual water depth (bathymetry + tide ht) experienced, and 4) distribution of the directions of movements. Both tidal and diel cycles influenced dugong movement. Tracked dugongs tended to be closer to shore at high tide than at low tide and closer to shore at night than during the day. Onshore movement was more prevalent on incoming tides and in the afternoon and evening. Offshore movement was more prevalent on outgoing tides and from midnight through the morning until midday. Tidal and diel variation in water depths used by the inshore—intertidal dugongs was small, but probably underestimated, hidden by a sampling bias in the telemetry equipment. Onshore movement at high tide allowed dugongs to exploit intertidal seagrass beds. Dugongs are closer to shore in afternoons and evenings than in mornings. This behavior may be related to the avoidance of predators or watercraft. Our findings can be used to predict spatial patterns of dugongs within areas of conservation management significance and to assess, avoid, and mitigate adverse effects of anthropogenic disturbance.  相似文献   

8.
Shell size distribution patterns of marine gastropod populations may vary considerably across different environments. We investigated the size and density structure of genetically continuous periwinkle populations (Littorina littorea) on an exposed rocky and a sheltered sedimentary environment on two nearby islands in the south-eastern North Sea (German Bight). On the sedimentary shore, periwinkle density (917 ± 722 individuals m−2) was about three times higher than on the rocky shore (296 ± 168 individuals m−2). Mean (9.8 ± 3.9 mm) and maximum (22 mm) shell size of L. littorea on the sedimentary shore were smaller than on the rocky shore (21.5 ± 4.2 and 32 mm, respectively), where only few small snails were found. Additionally, periwinkle shells were thicker and stronger on the rocky than on the sedimentary shore. To ascertain mechanisms responsible for differences in population structures, we examined periwinkles in both environments for growth rate, predation pressure, infection with a shell boring polychaete (Polydora ciliata) and parasitic infestation by trematodes. A crosswise transplantation experiment revealed better growth conditions on the sedimentary than on the rocky shore. However, crab abundance and prevalence of parasites and P. ciliata in adult snails were higher on the sedimentary shore. Previous investigations showed that crabs prefer large periwinkles infested with P. ciliata. Thus, we suggest that parasites and shell boring P. ciliata in conjunction with an increased crab predation pressure are responsible for low abundances of large periwinkles on the sedimentary shore while high wave exposure may explain low densities of juvenile L. littorea on the rocky shore. We conclude that biotic factors may strongly contribute to observed differences in size structure of the L. littorea populations studied on rocky and sedimentary shores.  相似文献   

9.
Temporal changes in the zoobenthos of southwest Mecklenburg Bay were studied using routine survey data collected in 1980–94. Earlier studies suggested that long-term oxygen deficiency on the scale of several months affects the zones below 20 m depth. Episodic benthic recolonization occurred during periods with improved oxygen conditions, as a rule by opportunistic polychaetes followed by some actively immigrating adult species. However, these observations were restricted to central and southern Lübeck Bay. Our recent data indicate that benthic recolonization exhibits greater regularity along the northern shore of Lübeck Bay. Special wind conditions and water exchange processes in the western Baltic Sea are likely to displace the deep water in northern Lübeck Bay more rapidly than in the southern zones. By means of multidimensional scaling, two types of episodic recruitment are identified in the benthos that are probably related to enhanced nitrogen discharge through river runoff in the winter and exceptionally weak water stratification in the summer.  相似文献   

10.
The life cycle of Mesidotea entomon sampled near the shore of Norrbyn in the northern Bothnian Sea, has been investigated. The species, a predacious brackish water isopod, had a three year life cycle. In May – June the juveniles were released from the female marsupium at a size of 3 mm. During the second summer size dimorphism became apparent, where the males were larger than the females. During the third summer and autumn the development of ova started in females. Maturation mostly occurred during late winter. Males matured before, and at larger sizes, than the females, 36.0 and 29.1 mm, respectively. The average fecundity was 153.2 and the females carried the eggs and embryos for several months before the release. Calculation of the survival rate for each year during the life-span revealed 0.05, 0.66 and 0.43, respectively.  相似文献   

11.
In the lower St. Lawrence estuary (LSLE, eastern Canada), blooms of the toxic dinoflagellate Alexandrium tamarense are a recurrent phenomenon, resulting in paralytic shellfish poisoning outbreaks every summer. A first coupled physical–biological model of A. tamarense blooms was developed for this system in order to explore the interactions between cyst germination, cellular growth and water circulation and to identify the effect of physical processes on bloom development and transport across the estuary. The simulated summer (1998) was characterized by an A. tamarense red tide with concentrations reaching 2.3 × 106 cells L−1 along the south shore of the LSLE. The biological model was built with previously observed A. tamarense cyst distribution, cyst germination rate and timing, and A. tamarense growth limitation by temperature and salinity. The coupled model successfully reproduced the timing of the A. tamarense bloom in 1998, its coincidence with the combined plumes from the Manicouagan and Aux-Outardes (M-O) rivers on the north shore of the estuary, and the temporal variations in the north-south gradients in cell concentrations. The simulation results reveal that the interaction between cyst germination and the estuarine circulation generates a preferential inoculation of the surface waters of the M-O river plume with newly germinated cells which could partly explain the coincidence of the blooms with the freshwater plume. Furthermore, the results suggest that the spatio-temporal evolution of the bloom is dominated by alternating periods of retention and advection of the M-O plume: east or north-east winds favor the retention of the plume close to the north shore while west or north-west winds result in its advection toward the south shore. The response of the simulated freshwater plume to fluctuating wind forcing controls the delivery of the A. tamarense bloom from the northern part of the estuary to the south shore. In addition, our results suggest that a long residence time of the M-O plume and associated A. tamarense population in the LSLE during the summer 1998 contributed to the development of the red tide. We thus hypothesize that the wind-driven dynamics of the M-O plume could partly determine the success of A. tamarense blooms in the LSLE by influencing the residence time of the blooms and water column stability, which in turn affects A. tamarense vertical migrations and growth.  相似文献   

12.
Biological control efforts against the shore fly Scatella tenuicosta Collin, a pest of commercial glasshouses, have had limited success. The ability of one of its parasitoids, Aphaereta debilitata Morley, to control shore fly populations was investigated on lettuce crops within six experimental glasshouse units, over 26 weeks. The six shore fly populations, either with or without a single release of 150 mixed-sexed parasitoids, were estimated by rearing from harvested pots each week. The presence of the parasitoid significantly reduced shore fly numbers from a mean of 30.3–13.2 adult flies emerging per pot. The level of damage to each lettuce was assessed using a scoring system (0–5: no damage to heavy damage, respectively). The introduction of parasitoids reduced the median damage score of the lettuces from 2 to 1 over the study, representing a considerable change in the marketability of the crop. This study shows that single inoculative releases of A. debilitata can quickly establish within a glasshouse and significantly reduce crop damage. This suggests that the parasitoid may represent a valuable addition to an IPM strategy for shore flies.  相似文献   

13.
K. Kivi  H. Kuosa 《Polar Biology》1994,14(6):389-399
Microbial communities in the water column and sea ice were studied during the EPOS-cruise on R/V Polarstern in the western Weddell Sea in late winter (October–November 1988). Samples were taken from four transects from heavy pack-ice to open water. The results indicated the important role of protozoans especially in the ice-edge area. Heterotrophic nanofiagellates, dinoflagellates, ciliates and sarcodines showed significant positive correlations with chlorophyll a. Autotrophic picoplankton and autotrophic flagellates, which were probably motile zooids of Phaeocystis pouchetii (up to 3×106 cells 1–1), were most abundant in the areas of low or medium chlorophyll a concentration. Sea ice contained high numbers of heterotrophic organisms, and the distribution of the different groups showed distinct vertical zonation. At two sites, the microbial assembly beneath the ice was clearly influenced by communities from the melting ice.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation  相似文献   

14.
Global climate warming is exacerbating the melting of glaciers in Arctic and subarctic nearshore regions. Glacial discharge causes increases in sedimentation, abrasion of organisms, and sand/silt cover along with lowered light intensity, salinity, nitrate and hard substrate cover. These effects can have deleterious consequences on foundation species, such as the kelps that provide important habitat structure and support tightly‐linked food webs. The purpose of this study was to determine if the kelp, Saccharina latissima, from a glacially‐influenced and an oceanic shore in a subarctic Alaskan estuary exhibits differing seasonal growth patterns in response to its environment. Reciprocal in situ shore transplant studies examined seasonal patterns in growth, physiological competence (as maximum quantum yield), morphology and storage product levels (mannitol) of S. latissima. In situ growth was seasonally different at the two shore locations, with a shorter growing season at the glacially‐influenced shore. During the glacial melt season, the thalli at the two shore locations were morphologically distinct. Mannitol levels were typically higher in thalli from the oceanic site, with generally low mannitol levels at the end and the beginning of the growing season on both shores. Maximum quantum yield was consistently high (≥0.7) at both shore sites and did not vary seasonally. Growth rates of glacially‐influenced transplants to the oceanic shore suggest that the glacially‐influenced population has a different seasonal growth pattern from that of the oceanic shore site, which seems to be genetically fixed or based on differences in gene expression. It appears that S. latissima is a highly resilient species, partly due to high phenotypic plasticity, which may have led to genetic fixation under persistent glacial conditions.  相似文献   

15.
Nitrogen fixation was investigated by means of the acetylene reduction method during the development of a water bloom of Nodularia in coastal waters of the Baltic Sea west of the island of Hiddensee and in backwaters showing different degrees of eutrophication. Depending on plankton density, the values found varied greatly. The maximum of nitrogen fixation values found in extremely dense water blooms under special conditions (Baltic Sea, 2250 μg N2/l · h; Kleiner Jasmunder Bodden, 374 μg N2/l · h) are up to 103 times higher than from other parts of the Baltic Sea or from inland waters. The average nitrogenase activity determined for coastal water populations of the Baltic Sea is 2.15 pg N2/heterocyst · h and that of the inmost backwaters 0.77 pg N2/heterocyst · h. The relationship between N2-fixation and nutrient content in water is discussed.  相似文献   

16.
Populations of the colonial hydroid Obelia geniculata in the White Sea reproduce asexually by frustule formation. Young medusae appear in the plankton during July and August. The number of medusae rarely exceeds 36 per m3, and the average number varies every year from 0.4 to 10 per m3. The size of medusae is smaller than reported from other regions. The umbrella of the largest recorded medusa was only 0.57 mm in diameter and the specimen had just 35 tentacles. Only a few mature medusae were found during the study. The colonies in the White Sea are epiphytic and grow only on laminarian thalli. At the beginning of July there are no colonies on thalli from the upper subtidal zone. By the end of August, colonies of O.␣geniculata had increased in density to 30 per m2. Hydroid recruitment was attributed to active frustule production by colonies living below that zone. The frustules detach from the stems of the hydroids and are found in plankton. Production of frustules on branches occurs continuously during colony growth until water temperatures climb above 0 °C. We found that water temperature in this Arctic environment is generally too low for medusa maturation and planula development in the species. Propagation by frustule formation is the principal means of reproduction in Obelia geniculata within the White Sea, and this phenomenon accounts for the species being a dominant epiphyte on laminarian thalli there.  相似文献   

17.
The study included 546 specimens of seven myctophid fish species from the South China Sea (captured during June 2015 by bottom and mid‐water trawls). Length‐weight relationships (LWRs), aLb, were estimated using standard length. The species belong to four genera. The values for the parameter a ranged from 0.006 to 0.022, while the b values ranged from 2.710 to 3.476 (Range of r2 values: .938 to .971). According to FishBase, this study presents the first LWRs for these species, including two maximum standard lengths for Diaphus chrysorhynchus and Notoscopelus resplendens.  相似文献   

18.
Research was undertaken to characterize Escherichia coli isolates in interstitial water samples of a sandy beach on the southeastern shore of Lake Huron, Ontario, Canada. A survey of the beach area revealed the highest abundance of E. coli in interstitial water of the foreshore beach sand next to the swash zone. Higher concentrations of E. coli (up to 1.6 × 106 CFU/100 ml of water) were observed in the interstitial water from the sampling holes on the beach itself compared to lake water and sediment. Repetitive extragenic palindromic PCR (REP-PCR) was used to characterize the genetic diversity of E. coli isolates from interstitial water samples on the beach. E. coli isolates from the same sampling location frequently exhibited the same REP-PCR pattern or were highly similar to each other. In contrast, E. coli isolates from different sampling locations represented populations distinct from each other. This study has identified a unique ecological niche within the foreshore area of the beach where E. coli may survive and possibly multiply outside of host organisms. The results are of interest as increasing concentrations of E. coli in recreational waters are often considered to be an indication of recent fecal pollution.  相似文献   

19.
Seasonal trends of biodeposition and animal coverage in backbarrier beds of the musselMytilus edulis in the East Frisian Wadden Sea were documented and quantified to assess the effects of physical disturbance by storms and to develop a conceptual model for the interpretation of biodeposits in the stratigraphic record. Accretion and erosion of biogenic muds (faeces and pseudofaeces) were quantified by repeated precision levelling of a 12 m2 test area. Animal coverage was documented by vertical photography prior to each levelling survey. Levelling and photography were conducted from a bridge and rail system to avoid physical disturbance by trampling. Four surveys, covering a period of different weather conditions, showed variable mean accretion/erosion rates of biodeposits ranging from +0.56 mm d−1 (accretion) to −1.34 mm d−1 (erosion) and areal coverage of mussels ranging from 39.1% to 0%. A pronounced seasonal trend in the biodepositional pattern was observed. Mean accretion rates were high (>0.5 mm d−1) during the summer season, whereas in the winter season net deposition decreased to zero or showed erosional trends. Longterm sediment budgets are thus composed of highly variable mean annual rates which, in turn, comprise highly variable seasonal and even monthly rates, depending on the local weather pattern. This forms the basis for a conceptual model, in terms of which the stratigraphic record of fossil biodeposits can be meaningfully interpreted.  相似文献   

20.
Many organisms possess remarkable abilities to orient and navigate within their environment to achieve goals. We examined the orientation behavior of a riparian spider, the Long‐Jawed Orb Weaver (Tetragnatha elongata), when displaced onto the surface of the water. When displaced, spiders move with alternating movements of the first three leg pairs while dragging the most posterior pair of legs behind them. In addition, spiders often perform a series of orientation behaviors consisting of concentric circles before ultimately choosing a path of travel directly toward the nearest point to land. While the number of orientation behaviors increased with increasing distance from shore, distance from shore had no effect on the direction of travel, which was significantly oriented toward the closest shoreline. These results indicate a complex ability to orient toward land when displaced onto water, possibly to decrease the amount of time on the surface of the water and thus decrease predation risk.  相似文献   

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