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1.
SAMUEL PIRLOT JULIE VANDERHEYDEN JEAN-PIERRE DESCY PIERRE SERVAIS 《Freshwater Biology》2005,50(7):1219-1232
1. This study focused on heterotrophic microorganisms in the two main basins (north and south) of Lake Tanganyika during dry and wet seasons in 2002. Bacteria (81% cocci) were abundant (2.28–5.30 × 106 cells mL?1). During the dry season, in the south basin, bacterial biomass reached a maximum of 2.27 g C m?2 and phytoplankton biomass was 3.75 g C m?2 (integrated over a water column of 100 m). 2. Protozoan abundance was constituted of 99% of heterotrophic nanoflagellates (HNF). Communities of flagellates and bacteria consisted of very small but numerous cells. Flagellates were often the main planktonic compartment, with a biomass of 3.42–4.43 g C m?2. Flagellate biomass was in the same range and often higher than the total autotrophic biomass (1.60–4.72 g C m?2). 3. Total autotrophic carbon was partly sustained by the endosymbiotic zoochlorellae Strombidium. These ciliates were present only in the euphotic zone and usually contributed most of the biomass of ciliates. 4. Total heterotrophic ciliate biomass ranged between 0.35 and 0.44 g C m?2. In 2002, heterotrophic microorganisms consisting of bacteria, flagellates and ciliates represented a large fraction of plankton. These results support the hypothesis that the microbial food web contributes to the high productivity of Lake Tanganyika. 5. As the sole source of carbon in the pelagic zone of this large lake is phytoplankton production, planktonic heterotrophs ultimately depend on autochthonous organic carbon, most probably dissolved organic carbon (DOC) from algal excretion. 相似文献
2.
Bacterial diversity in five Icelandic geothermal waters: temperature and sinter growth rate effects 总被引:1,自引:0,他引:1
The microbial ecology associated with siliceous sinters was studied in five geochemically diverse Icelandic geothermal systems.
Bacterial 16S rRNA clone libraries were constructed from water-saturated precipitates from each site resulting in a total
of 342 bacterial clone sequences and 43 species level phylotypes. In near-neutral, saline (2.6–4.7% salinity) geothermal waters
where sinter growth varied between 10 and ~300 kg year−1 m−2, 16S rRNA gene analyses revealed very low (no OTUs could be detected) to medium (9 OTUs) microbial activity. The most dominant
phylotypes found in these waters belong to marine genera of the Proteobacteria. In contrast, in alkaline (pH = 9–10), meteoric geothermal waters with temperature = 66–96°C and <1–20 kg year−1m−2 sinter growth, extensive biofilms (a total of 34 OTUs) were observed within the waters and these were dominated by members
of the class Aquificae (mostly related to Thermocrinis), Deinococci (Thermus species) as well as Proteobacteria. The observed phylogenetic diversity (i.e., number and composition of detected OTUs) is argued to be related to the physico-chemical
regime prevalent in the studied geothermal waters; alkaliphilic thermophilic microbial communities with phylotypes related
to heterotrophic and autotrophic microorganisms developed in alkaline high temperature waters, whereas halophilic mesophilic
communities dominated coastal geothermal waters. 相似文献
3.
Bacterioplankton in Antarctic Ocean Waters During Late Austral Winter: Abundance, Frequency of Dividing Cells, and Estimates of Production 总被引:10,自引:5,他引:5
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R. B. Hanson David Shafer Theresa Ryan Daniel H. Pope H. Kenneth Lowery 《Applied microbiology》1983,45(5):1622-1632
Bacterioplankton productivity in Antarctic waters of the eastern South Pacific Ocean and Drake Passage was estimated by direct counts and frequency of dividing cells (FDC). Total bacterioplankton assemblages were enumerated by epifluorescent microscopy. The experimentally determined relationship between in situ FDC and the potential instantaneous growth rate constant (μ) is best described by the regression equation ln μ = 0.081 FDC − 3.73. In the eastern South Pacific Ocean, bacterioplankton abundance (2 × 105 to 3.5 × 105 cells per ml) and FDC (11%) were highest at the Polar Front (Antarctic Convergence). North of the Subantarctic Front, abundance and FDC were between 1 × 105 to 2 × 105 cells per ml and 3 to 5%, respectively, and were vertically homogeneous to a depth of 600 m. In Drake Passage, abundance (10 × 105 cells per ml) and FDC (16%) were highest in waters south of the Polar Front and near the sea ice. Subantarctic waters in Drake Passage contained 4 × 105 cells per ml with 4 to 5% FDC. Instantaneous growth rate constants ranged between 0.029 and 0.088 h−1. Using estimates of potential μ and measured standing stocks, we estimated productivity to range from 0.62 μg of C per liter · day in the eastern South Pacific Ocean to 17.1 μg of C per liter · day in the Drake Passage near the sea ice. 相似文献
4.
Spatial changes of small nanoplankton (2–10 μm) were investigated in relation to sea-ice conditions, hydrography and receding
ice processes in the Ross Sea (Antarctica) during spring 1994. Abundance and biomass of heterotrophic and autotrophic nanoplankton,
as well as bacterioplankton, were determined along a south-north transect from the open waters polynya towards the pack ice.
Autotrophic and heterotrophic nanoplankton biomass ranged from 758 to 4570 mgC m−2 and from 3 to 387 mgC m−2, respectively. Heterotrophic nanoplankton accounted, on average, for about 9% of the total (i.e. autotrophic plus heterotrophic)
nanoplankton biomass. The size structure of both auto- and heterotrophic nanoplankton in the Ross Sea continental shelf receding
ice edge was different from that of nanoplankton associated with the shelf break and open Antarctic ice-edge area. Generally,
the highest heterotrophic biomass was found in the pack-ice zone on the continental shelf, while the highest heterotrophic
contribution to the total nanoplankton biomass (up to 25%) was encountered at the shelf break where phytoplankton was largely
dominated by 2- to 3-μm-size cells.
Accepted: 2 May 1999 相似文献
5.
Hans Mose Jensen Lorna Pedersen AnnDorte Burmeister Benni Winding Hansen 《Polar Biology》1999,21(5):269-278
The distribution of phytoplankton biomass and primary production were studied during summer 1993 at 16 stations from 65 to
72°N off West Greenland, ranging more than 900 km. Hydrography, nutrients and chlorophyll a profiles revealed a significant change in structure from south to north. Nitrate was depleted in the euphotic zone at most
stations except close to the ice edge (West Ice) or close to outflow from large glaciers. The vertical distribution of phosphate
followed that of nitrate, but was never depleted. Despite two stations with relatively high surface concentrations, silica
showed the same distribution as the other two nutrients. In the south, chlorophyll a concentration and primary production were lower than north of Disko Bay (69°N), associated with a well-mixed versus a salinity-generated
stratification, respectively. In Vaigat, a high-production station was identified, (st. 910, 69°52′69N–51°30′61W) with a chlorophyll a concentration in the euphotic zone of >13 μg l−1 and an area primary production of 3.2 g C m−2 day−1. This is seldom encountered in arctic waters and was presumably due to nutrient-rich melt-water originating from the Iluliíssat
Glacier. The overall primary production for the studied area was 67–3207 mg C m−2 day−1 (mean ± SD=341± 743 mg C m−2 day−1), which is within the range of the few results published for West Greenland and eastern Canadian Arctic waters.
Accepted: 24 October 1998 相似文献
6.
Seasonal relationships between planktonic microorganisms and dissolved organic material in an alpine stream 总被引:1,自引:1,他引:0
Diane M. McKnight Richard L. Smith Richard A. Harnish Christine L. Miller Kenneth E. Bencala 《Biogeochemistry》1993,21(1):39-59
The relationships between the abundance and activity of planktonic, heterotrophic microorganisms and the quantity and characteristics
of dissolved organic carbon (DOC) in a Rocky Mountain stream were evaluated. Peak values of glucose uptake, 2.1 nmol L−1 hr−1, and glucose concentration, 333 nM, occurred during spring snowmelt when the water temperature was 4.0°C and the DOC concentration
was greatest. The turnover time of thein situ glucose pool ranged seasonally from 40–1110 hours, with a mean of 272 hr. Seasonal uptake of3H-glucose, particulate ATP concentrations, and direct counts of microbial biomass were independent of temperature, but were
positively correlated with DOC concentrations and negatively correlated with stream discharge. Heterotrophic activity in melted
snow was generally low, but patchy. In the summer, planktonic heterotrophic activity and microbial biomass exhibited small-scale
diel cycles which did not appear to be related to fluctuations in discharge or DOC, but could be related to the activity of
benthic invertebrates. Leaf-packs placed under the snow progressively lost weight and leachable organic material during the
winter, indicating that the annual litterfall in the watershed may be one source of the spring flush of DOC. These results
indicate that the availability of labile DOC to the stream ecosystem is the primary control on seasonal variation in heterotrophic
activity of planktonic microbial populations. 相似文献
7.
The distribution of picoplankton and nanoplankton in Kongsfjorden,Svalbard during late summer 2006 总被引:2,自引:0,他引:2
Abundance and biomass of pico- (<2 μm) and nanoplankton (2–20 μm) were investigated in relation to hydrography in Kongsfjorden,
Svalbard (79°N, 12°E) during late summer 2006. Autotrophic and heterotrophic picoplankton abundance ranged from 0.1 × 106 to 35.2 × 106 cells L−1 and from 0.4 × 106 to 20.3 × 106 cells L−1, respectively. The highest number of bacteria in the entire water column was recorded at station 2 at 10 m (22.3 × 108 cells L−1); the lowest concentration was observed at station 1 (6.0 × 108 cells L−1). The abundance of autotrophic and heterotrophic nanoplankton varied from 0.4 × 105 cells L−1 to 46 × 105 cells L−1 and from 0.3 × 106 to 9.1 × 106 cells L−1, respectively. Our results demonstrated that heterotrophic nanoflagellates and bacteria in Kongsfjorden microbial community
were relatively important. The structure of plankton communities integrated with environmental variables could act as indicators
of the variability of the inflow of Atlantic Water into Kongsfjorden. 相似文献
8.
Regional variations in mesozooplankton composition, abundance and biomass were studied during a cruise in August 2006 near
Novaya Zemlya Archipelago (eastern Barents Sea) using Juday net hauls from the bottom (or 100 m depth) to the surface. A comparison
with multiannual literature values revealed that the mean temperature and salinity in the south and centre of the study area
were similar to typical values, while temperature in the north was significantly higher. A total of 36 species and higher
taxa were identified. Mesozooplankton abundance and biomass varied from 47 to 851 ind m−3 and from 5 to 74 mg dry weight m−3, respectively. Copepods dominated the mesozooplankton community, reaching 73–98% and 61–97% of the total abundance and biomass.
Calanus finmarchicus and Oithona similis were the most abundant species at all stations. The biodiversities (Shannon indices) of the mesozooplankton community varied
between stations from 1.10 to 2.46 (estimated from species abundances) and from 0.19 to 1.92 (estimated from species biomasses),
averaging 1.93 ± 0.127 and 1.34 ± 0.151, respectively. Three groups at the 48% level of dissimilarity of species abundance
were delineated by cluster analyses. The clusters differed significantly with respect to temperature and salinity. The total
mesozooplankton abundance and biomass as well as quantitative parameters of most common taxa scaled negatively with temperature. 相似文献
9.
We investigated the distribution of mesozooplankton in waters north of Svalbard (north of 78°50′N) at 38 stations in August
and September of 2002, 2003 and 2004. The zooplankton community was numerically dominated by copepods (58–98% of the total
abundance). Zooplankton abundance ranged from 115 individuals m−3 at the northern most location to 12,296 individuals m−3 on the shelf. Cluster analysis revealed four different groups with distinct geographic integrity that were identified by
variation in species densities rather than by variation in taxonomic composition. Water temperature and salinity differed
significantly between the different cluster groups indicating that part of the observed variations in species distribution
relate to differences in hydrography. Numerous significant regressions between zooplankton abundance at species level and
hydrographical parameters suggest that variability in water masses has measurable effects on zooplankton distribution and
species composition in the study area. 相似文献
10.
The benthic fauna off King George Island (South Shetland Islands, Antarctica) was investigated during "Polarstern" expedition ANT XV/3 in March 1998. Samples were taken along two cross-shelf/slope transects both north (Drake Passage) and south of the island (Bransfield Strait, off Potter Cove) at water depths ranging from 130 m to 2,000 m. For a quantitative inventory, a multibox corer was used at nine stations to collect mostly infaunal macrobenthos; at seven stations, seabed photography was employed concomitantly to survey the epibenthic megafauna. Macrofauna abundances ranged from 730 ind. m–2 at 2,000 m to >14,000 ind. m–2 at 100 m; biomass values varied between about 50 g wet mass m–2 (6 g ash-free dry mass m–2) at 2,000 m and about 950 g wet mass m–2 (about 90 g ash-free dry mass m–2) at 200 m. Densities were dominated everywhere by polychaetes, followed by bivalves, crustaceans and ophiuroids; in terms of biomass, krill and holothurians surpassed polychaetes at some stations. No significant differences between the northern and the southern transects in total abundance and biomass were obvious. Megafauna abundances were clearly higher south of King George Island, totalling about 110–150 ind. m–2 on the shelf (235–330 m) and about 50 ind. m–2 at the continental slope (750 m), whereas along the northern transect they reached values of only 21–31 ind. m–2 on the shelf (130–430 m) and decreased at the continental slope (950 m) to about 5 ind. m–2. A brittle star, Ophionotus victoriae, strongly dominated the southern-shelf epibenthos, with relative abundances of 70–95% and a biomass of about 40–80 g wet mass m–2 (about 4–7 g ash-free dry mass m–2), but was numerically less important at the slope (5%) where ammotheid pycnogonids prevailed (80%). Macro- and megabenthos distribution patterns were characterized by a pronounced shelf-slope gradient – in standing stock as well as in faunistic composition – but this resemblance was statistically not significant. This finding indicates that the spatial distributions of macrobenthos and megabenthos are primarily determined by a depth-dependent factor, most probably food supply, but apparently respond differently to secondary driving forces, possibly seabed features. Our results provide further evidence for the notion that there is no distinct latitudinal gradient in benthic abundance and biomass in the Southern Ocean between the South American Magellan region and high-Antarctic waters of the Weddell Sea. 相似文献
11.
Gustavo A. Thompson Estela O. Dinofrio Viviana A. Alder 《Helgoland Marine Research》2012,66(2):127-138
The relative importance of small forms of copepods has been historically underestimated by the traditional use of 200?C300-??m mesh nets. This work quantified the distribution and abundance of copepods, considering two size fractions (<300???m and >300???m), in superficial waters (9?m deep) of the Drake Passage and contributed to the knowledge of their interannual fluctuations among three summers. Four types of nauplii and eleven species of copepods at copepodite and adult stages were identified, with abundance values of up to 13 ind L?1 and 28,300???g C m?3. The <300-??m fraction, composed of Oithona similis, small cyclopoids and nauplii, dominated the copepod communities in the 3?years; it accounted for more than 77% of the total number and for between 40 and 63% of the total biomass. Changes in density and biomass values among the three cruises differed according to copepod size fraction and water mass; the >300-??m fraction showed no changes among the 3?years, both in Antarctic (density and biomass) and in Subantarctic waters (density), whereas the <300-??m fraction showed higher (density and biomass) values in 2001 both in Subantarctic and in Antarctic waters. Sea surface temperature and its anomaly accounted for the largest proportion of variability in copepod density and biomass, particularly for the <300-??m fraction. 相似文献
12.
Bacterioplankton abundance and production, chlorophyll a (Chl a) concentrations and primary production (PP) were measured from the equatorial Indian Ocean (EIO) during northeast (NEM),
southwest (SWM) and spring intermonsoon (SpIM) seasons from 1°N to 5°S along 83°E. The average bacterial abundance was 0.52 ± 0.29,
0.62 ± 0.33 and 0.46 ± 0.19 (× 108 cells l−1), respectively during NEM, SWM and SpIM in the top 100 m. In the deep waters (200 m and below), the bacterial counts averaged
∼0.35 ± 0.14 × 108 cells l−1 in SWM and 0.39 ± 0.16 × 108 cells l−1 in SpIM. The 0–120 m column integrated bacterial production (BP) ranged from 19 to 115 and from 10 to 51 mg C m−2 d−1 during NEM and SWM, respectively. Compared with many open ocean locations, bacterial abundance and production in this region
are lower. The bacterial carbon production, however, is notably higher than that of phytoplankton PP (BP:PP ratio 102% in
SWM and 188% in NEM). With perpetually low PP (NEM: 20, SWM: 18 and SpIM: 12 mg C m−2 d−1) and Chl a concentration (NEM: 16.5, SWM: 15.0 and SpIM: 20.9 mg m−2), the observed bacterial abundance and production are pivotal in the trophodynamics of the EIO. Efficient assimilation and
mineralization of available organics by bacteria in the euphotic zone might serve a dual role in the ultra-oligotrophic regions
including EIO. Thus, bacteria probably sustain microheterotrophs (micro- and meso-zooplankton) through microbial loop. Further,
rapid mineralization by bacteria will make essential nutrients available to autotrophs. 相似文献
13.
Mesozooplankton assemblages in the shallow Arctic Laptev Sea in summer 1993 and autumn 1995 总被引:2,自引:0,他引:2
Mesozooplankton distribution and composition in the very shallow part of the Siberian Laptev Sea shelf were studied during
the German-Russian expeditions “Transdrift I” (August/September 1993) and “Transdrift III” (October 1995). Maximum abundances
were found close to the outflow of the Lena River (7,965 ind. m−3) and in the Yana river mouth (38,163 ind. m−3). Lowest abundances occurred in the northeast and west of the Laptev Sea (64–95 ind. m−3). Highest biomass values (104–146 mg DM m−3) were determined in the northern and northeastern part of the shallow Laptev Sea, as well as close to the river outflows,
with a record biomass maximum in the Yana river mouth (270 mg DM m−3). Biomass minima were situated north of the Lena Delta and in the western part of the shallow Laptev Sea (0.3–1.0 mg DM m−3). Copepods dominated in terms of abundance and biomass. Cluster analyses separated four mesozooplankton assemblages: the
assemblage “Lena/Yana” in the southern part, “Eastern-central” in the centre, “Kotelnyy” in the eastern part and “Taimyr”
in the western part of the shallow Laptev Sea. The small-sized neritic and brackish-water copepods Drepanopus bungei, Limnocalanus grimaldii and Pseudocalanus major occurred in enormous numbers and made up the bulk of zooplankton abundance and biomass in the very shallow part of the Laptev
Sea close to the rivers Lena and Yana. In the more northern and northeastern areas, Calanus glacialis, P. minutus and P. major were dominant copepod species, whereas Oithona similis and Acartia sp. became important in the western Laptev Sea. Appendicularians, as well as hydromedusae and the chaetognath Sagitta sp., contributed significantly to abundance and biomass, respectively, but not over the entire area studied. One can identify
taxon-specific distribution patterns (e.g. Sagitta predominated the biomass in a zone between the area heavily influenced by Lena/Yana and the offshore area to the north),
which differ from the patterns revealed by cluster analysis. Hydrographic features, especially the enormous freshwater inflow,
apparently determine the occurrence and formation of zooplankton aggregations. Extremely high numbers of small-sized neritic
and brackish-water copepods occurred locally, which were probably also supported by excellent feeding conditions. 相似文献
14.
Outbreak of blue-green algal blooms, with associated unsightly scum and unpleasant odor, occurs frequently in eutrophic lakes.
We conducted feeding experiments to study ingestion and digestion of Microcystis aeruginosa by tilapia (Oreochromis niloticus) under laboratory conditions and field testing to reduce Microcystis blooms by stocking tilapia in Lake Yuehu and other eutrophic waters in Ningbo, China between 2000 and 2003. Our results show
that tilapia was capable of ingesting and digesting a large quantity of Microcystis. Digestion efficiency ranged from 58.6 to 78.1% at water temperature of 25 °C. Ingestion rate increased with increasing fish
weight and water temperature. Intensive blooms occurred in Lake Yuehu in both 1999 and 2000. The lake was stocked with silver
carp (Hypophthalmichthys molitrix), bighead (Aristichthys nobilis) and a freshwater mussel (Hyriopsis cumingii) at a total biomass of 9.8 g m−3 in early 2001, and tilapia at 3–5 g m−3 in April of 2002. From June to October, average phytoplankton density decreased from 897.6×106 cells l−1 in 2000 to 291.7×106 cells l−1 in 2001 and 183.0×106 cells l−1 in 2002. Compared to 2000, the annual average phytoplankton biomass in 2001 and 2002 decreased by 48.6% and 63.8%, respectively.
The blue-green algal biomass which made up 70% of the total phytoplankton biomass in 2000 was reduced to 22.1% in 2001 and
11.2% in 2002. Meanwhile, Secchi depth increased from 20–50 cm to 55–137 cm during the same time period. Similar results were
observed in some other eutrophic waters. For example, algal bloom disappeared about 20 days after tilapia fingerlings were
stocked (8–15 g m−3) to a pond in Zhenhai Park. Chlorophyll a concentration and phytoplankton production declined dramatically whereas water transparency increased substantially. However,
the impacts of tilapia on nitrogen and phosphorus dynamics in natural lakes need further investigation. Our studies revealed
that stocking tilapia is an effective way to control algal blooms in eutrophic waters, especially in lakes where nutrient
loading cannot be reduced sufficiently, and where grazing by zooplankton cannot control phytoplankton production effectively. 相似文献
15.
This study reports on the density, growth, and production response of the dominant black fly, Prosimulium martini, to whole river fertilization of the Kuparuk River in arctic Alaska during the summer of 1984. Beginning in 1983, a long
term study of fertilization effects was initiated in the Kuparuk River. Increased nutrient supply stimulated algal and microbial
biomass and microbial activity, which in turn affected the larval growth and abundance of Prosimulium. This experiment allowed us to isolate the effects of nutrient supply from other factors in determining black fly growth
and abundance.
Phosphorus addition had the following indirect effects on Prosimulium: growth was higher, but abundance decreased in the enriched section, leading to a net decrease in secondary production from
2.62 g m−2 yr−1 to 0.77 g m−2 yr−1. Prosimulium emergence rates were not measureably affected. The decrease in abundance and production appears to be a result of competitive
displacement by the caddisfly Brachycentrus americanus which increased in abundance in the fertilized section of the river. 相似文献
16.
Chlorophyll a and nutrient concentrations along with temperature and salinity values were measured at 22 CTD stations along a 735-km transect
running to the northwest of the island of South Georgia, Southern Ocean. Measurements were repeated during five summer surveys
(January and February 1994, January 1996, December 1996, January 1998) and one spring survey (October 1997). The transect
sampled Sub-Antarctic Zone water in the north, Polar Frontal Zone water and Antarctic Zone water in the south. Chlorophyll
a concentrations were lowest to the north of the transect and frequently high (up to 17 mg m−3) in the deep open ocean of the Antarctic Zone. Sub-surface peaks were measured in all zones and chlorophyll a was detectable to a depth of 150 m. There was a clear latitudinal temperature gradient in the near-surface waters (0–50 m),
the warmest water occurring in the north (∼12 °C), and the coolest in the Antarctic Zone (∼2 °C). There was also a well-defined
latitudinal gradient in summer near-surface silicate concentrations (∼2, 4, and 10 mmol m−3 in the Sub-Antarctic Zone, the Polar Frontal Zone and the Antarctic Zone, respectively), increasing to >20 mmol m−3 near South Georgia. Distinct differences in silicate concentrations were also evident in all three zones to a depth of 500 m.
Near-surface nitrate and phosphate concentrations were relatively low to the north of the transect (∼14 and 1 mmol m−3, respectively) and higher in the Polar Frontal Zone and Antarctic Zone (∼18 and 1.4 mmol m−3, respectively). Ammonium and nitrite were restricted to the upper 200 m of the water column, and exhibited sub-surface concentration
peaks, the lowest being in the Sub-Antarctic Zone (0.68 and 0.25 mmol m−3, respectively) and the highest in the Antarctic Zone (1.72 and 0.29 mmol m−3, respectively). Surface (∼6 m) spring nutrient measurements provided an indication of pre-bloom conditions; ammonium and
nitrite concentrations were low (∼0.27 and 0.28 mmol m−3, respectively), while silicate, nitrate and phosphate concentrations were high and similar to previously measured winter
values (e.g. ∼26, 23, 2 mmol m−3, respectively in the Antarctic Zone). Although the values measured were very variable, and there was some evidence of a seasonal
growth progression, the chlorophyll a and nutrient distribution patterns were dominated by intercruise (interannual) factors. Approximate nutrient depletions (spring
minus summer) appeared similar in the Polar Frontal Zone and Antarctic Zone for nitrate and phosphate, while silicate showed
a marked latitudinal increase from north to south throughout the transect. Highest chlorophyll a concentrations coincided with the highest apparent silicate depletions over the deep ocean of the Antarctic Zone. In this
area, relatively warm, easterly flowing Antarctic Circumpolar Current water meets cooler, westerly flowing water that is influenced
by the Weddell-Scotia Confluence and is rich in nutrients, especially silicate.
Accepted: 27 November 1999 相似文献
17.
Recovery of Aboveground Plant Biomass and Productivity After Fire in Mesic and Dry Black Spruce Forests of Interior Alaska 总被引:1,自引:0,他引:1
Michelle C. Mack Kathleen K. Treseder Kristen L. Manies Jennifer W. Harden Edward A. G. Schuur Jason G. Vogel James T. Randerson F. Stuart Chapin III 《Ecosystems》2008,11(2):209-225
Plant biomass accumulation and productivity are important determinants of ecosystem carbon (C) balance during post-fire succession.
In boreal black spruce (Picea mariana) forests near Delta Junction, Alaska, we quantified aboveground plant biomass and net primary productivity (ANPP) for 4 years
after a 1999 wildfire in a well-drained (dry) site, and also across a dry and a moderately well-drained (mesic) chronosequence
of sites that varied in time since fire (2 to ∼116 years). Four years after fire, total biomass at the 1999 burn site had
increased exponentially to 160 ± 21 g m−2 (mean ± 1SE) and vascular ANPP had recovered to 138 ± 32 g m−2 y−1, which was not different than that of a nearby unburned stand (160 ± 48 g m−2 y−1) that had similar pre-fire stand structure and understory composition. Production in the young site was dominated by re-sprouting
graminoids, whereas production in the unburned site was dominated by black spruce. On the dry and mesic chronosequences, total
biomass pools, including overstory and understory vascular and non-vascular plants, and lichens, increased logarithmically
(dry) or linearly (mesic) with increasing site age, reaching a maximum of 2469 ± 180 (dry) and 4008 ± 233 g m−2 (mesic) in mature stands. Biomass differences were primarily due to higher tree density in the mesic sites because mass per
tree was similar between sites. ANPP of vascular and non-vascular plants increased linearly over time in the mesic chronosequence
to 335 ± 68 g m−2 y−1 in the mature site, but in the dry chronosequence it peaked at 410 ± 43 g m−2 y−1 in a 15-year-old stand dominated by deciduous trees and shrubs. Key factors regulating biomass accumulation and production
in these ecosystems appear to be the abundance and composition of re-sprouting species early in succession, the abundance
of deciduous trees and shrubs in intermediate aged stands, and the density of black spruce across all stand ages. A better
understanding of the controls over these factors will help predict how changes in climate and fire regime will affect the
carbon balance of Interior Alaska.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
Distribution of abundance, biomass, production and productivity of macrozoobenthos in the sub-Antarctic Magellan Province (South America) 总被引:3,自引:3,他引:0
Distribution of abundance, biomass, productivity and production of macrozoobenthos was investigated in four study areas in
the Magellan region (South Patagonian Ice-Field, Strait of Magellan, Beagle Channel, Continental Shelf). Using a Reineck box
corer and a multibox corer, a total of 277 quantitative benthos samples were taken at 78 stations in water depths between
8 and 1139 m during the Joint Chilean-German-Italian Magellan “Victor-Hensen Campaign” in 1994, the “Polarstern” expedition
ANT XIII/4 in 1996 and the Chilean expeditions “Cimar Fiordo II + III” in 1996 and 1997, respectively, on board RV “Vidal
Gormaz”. Mean abundance in the South Patagonian Ice-Field was significantly lower than in the Strait of Magellan and the Beagle
Channel. Biomass and abundance decreased clearly with depth (20–300 m to 700–1500 m: 3.9 gC m−2 to 0.6 gC m−2; 2832 ind. m−2 to 569 ind. m−2). Average abundance, biomass and production of the whole Magellan region are lower (2318 ind. m−2, 3.2 gC m−2, 0.62 gC m−2 year−1) than in the high Antarctic Weddell Sea. In the Magellan region, macrozoobenthos composition of abundance is mainly dominated
by polychaetes (56%), followed by arthropods (16%), echinoderms (10%) and molluscs (11%). Comparisons of our present results
with those of high Antarctic areas make it clear that the Magellan region has a transitional character.
Accepted: 21 December 1998 相似文献
19.
Sparse Ulmus pumila woodlands play an important role in contributing to ecosystem function in semi-arid grassland of northern China. To understand
the key attributes of soil carbon cycling in U. pumila woodland, we studied dynamics of soil respiration in the canopy field (i.e., the projected crown cover area) and the open
field at locations differing in distance (i.e., at 1–1.5, 3–4, 10, and >15 m) to tree stems from July through September of
2005, and measured soil biotic factors (e.g., fine root mass, soil microbial biomass, and activity) and abiotic factors [e.g.,
soil water content (SWC) and organic carbon] in mid-August. Soil respiration was further separated into root component and
microbial component at the end of the field measurement in September. Results showed that soil respiration had a significant
exponent relationship with soil temperature at 10-cm depth. The temperature sensitivity index of soil respiration, Q
10, was lower than the global average of 2.0, and declined significantly (P < 0.05) with distance. The rate of soil respiration was generally greater in the canopy field than in the open field; monthly
mean of soil respiration was 305.5–730.8 mg CO2 m−2 h−1 in the canopy field and 299.6–443.1 mg CO2 m−2 h−1 in the open field from July through September; basal soil respiration at 10°C declined with distance, and varied from ~250 mg
CO2 m−2 h−1 near tree stems to <200 mg CO2 m−2 h−1 in the open field. Variations in soil respiration with distance were consistent with patterns of SWC, fine root mass, microbial
biomass and activities. Regression analysis indicated that soil respiration was tightly coupled with microbial respiration
and only weakly related to root respiration. Overall, variations in SWC, soil nutrients, microbial biomass, and microbial
activity are largely responsible for the spatial heterogeneity of soil respiration in this semi-arid U. pumila woodland. 相似文献
20.
David Pecqueur Francesca Vidussi Eric Fouilland Emilie Le Floc’h Sebastien Mas Christian Salles Marie-George Tournoud Behzad Mostajir 《Hydrobiologia》2011,673(1):13-27
Episodic river flash floods, characteristic of Mediterranean climates, are suspected to greatly affect the functioning of
microbial food webs. For the first time, the abundance, biomass and diversities of microbial food web components were studied
before and during 4 consecutive days after a flash flood that occurred in November 2008, in the surface waters of five stations
along a salinity gradient from 20 to 36 in the Thau lagoon. Eukaryotic pico- and nanophytoplankton were discharged from the
river into the lagoon and increased by 30- and 70-fold, respectively. Bacteria increased by only 2-fold in the lagoon, from
around 4–8 × 106 cells ml−1, probably benefiting from river nutrient input. Chlorophyll a increased 4-fold, and pigment biomarkers showed that the dinophyceae, prasinophyceae and prymnesiophyceae were sensitive
to the flood perturbation, whereas the bacillariophyceae, cryptophyceae and chlorophyceae were resistant and/or transported
to the lagoon from the river. Predator responses were more complex as total heterotrophic flagellate abundance decreased slightly,
whereas those of specific naked ciliates increased, particularly for Uronema sp. The flood also induced a specific change in diversity, from a community dominated by Strobilidium spiralis to a community dominated by Uronema sp. The tintinnid community was particularly sensitive to the flood event as the abundance of all species decreased greatly.
The high increases in biomass, mainly brought by the river during the flood, could have eventually sedimented to the benthic
layer and/or been transported further into the lagoon, supporting the pelagic food web, or have even been exported to the
Mediterranean Sea. 相似文献