共查询到20条相似文献,搜索用时 125 毫秒
1.
Distribution and feeding of chaetognaths in the epipelagic zone of the Lazarev Sea (Antarctica) during austral summer 总被引:1,自引:0,他引:1
This study seeks to determine the effects of local hydrography on the distribution, abundance and feeding of chaetognaths
in the Lazarev Sea, an area strongly controlled by physical processes which has been held responsible for initiating the Weddell
Polynya. Zooplankton samples were taken at 39 stations on four transects located between 6°W and 3°E and from 60°S to 70°S
between surface and 350 m. The dominant species, Eukrohnia hamata, accounted for 86.5% of all chaetognaths, followed by Sagitta gazellae (8.1%) and Sagitta marri (5.4%). These three species showed distinct vertical and horizontal distribution patterns. While E. hamata and S. marri had maximum abundances below 250 m depth, S. gazellae showed a narrow distribution band in the upper 150 m depth. The distribution pattern was strongly modified at the Greenwich
meridian with an upward transport of a high abundance of deep dwelling organisms (S. marri and E. hamata) and a displacement of S. gazellae to the surface, likely coupled with the rise of the warm, saline halo around the Maud Rise. Small copepods were the main
prey of all three chaetognath species. Feeding rates (FR) varied among species and depth. Sagitta marri showed the highest FR with 0.38 prey d−1, followed by S. gazellae and E. hamata (0.22 and 0.07 prey d−1). Feeding rates were usually highest in the 25–80-m stratum. Size distribution and maturity of E. hamata revealed a dominance of small and immature organisms along all depths and stations, suggesting that this area might be acting
as an important source of recently spawned organisms to the surface. 相似文献
2.
Attenuation of the vertical flux of copepod fecal pellets under Arctic sea ice: evidence for an active detrital food web in winter 总被引:1,自引:0,他引:1
Makoto Sampei Alexandre Forest Hiroshi Sasaki Hiroshi Hattori Ryosuke Makabe Mitsuo Fukuchi Louis Fortier 《Polar Biology》2009,32(2):225-232
A variable fraction of fecal pellets produced in the epipelagic layer is intercepted and retained before reaching the bottom.
We assessed fecal pellet retention in the ice-covered Beaufort Sea in early February by comparing the shape and size-frequency
distribution of pellets collected by a sediment trap moored at 210 m to that produced in vitro. Appendicularian ellipsoidal
and copepod cylindrical pellets made up 75 and 24% of the flux (165 μg C m−2 day−1). In contrast, production (135 μg C m−2 day−1) was dominated by cylindrical pellets (93%). The vertical flux of cylindrical pellets at 210 m was attenuated by 70%. Pellets
>120 μm in width, represented 42% of the production, but were not detected in the trap. Retention most likely resulted from
coprorhexic feeding by copepods such as Metridia longa. Our observations suggest that the detritivore food web prevailing under the ice of the Arctic Ocean in winter is dominated
by appendicularians feeding on pellets fragmented by copepods. 相似文献
3.
Algal communities and export of organic matter from sea ice were studied in the offshore marginal ice zone (MIZ) of the northern
Barents Sea and Nansen Basin of the Arctic Ocean north of Svalbard by means of ice cores and short-term deployed sediment
traps. The observations cover a total of ten stations within the drifting pack ice, visited over a period of 3 years during
the period of ice melt in May and July. Maximum flux of particulate organic carbon and chlorophyll a from the ice at 1 m depth (1,537 mg C m−2 per day and 20 mg Chl a m−2 per day) exceeded the flux at 30 m by a factor of 2 during spring, a pattern that was reversed later in the season. Although
diatoms dominated the ice-associated algal biomass, flagellates at times revealed similarly high biomass and typically dominated
the exported algal carbon. Importance of flagellates to the vertical flux increased as melting progressed, whereas diatoms
made the highest contribution during the early melting stage. High export of ice-derived organic matter and phytoplankton
took place simultaneously in the offshore MIZ, likely as a consequence of ice drift dynamics and the mosaic structure of ice-covered
and open water characteristic of this region. 相似文献
4.
Heike Link Philippe Archambault Tobias Tamelander Paul E. Renaud Dieter Piepenburg 《Polar Biology》2011,34(12):2025-2038
Seasonal dynamics in the activity of Arctic shelf benthos have been the subject of few local studies, and the pronounced among-site
variability characterizing their results makes it difficult to upscale and generalize their conclusions. In a regional study
encompassing five sites at 100–595 m water depth in the southeastern Beaufort Sea, we found that total pigment concentrations
in surficial sediments, used as proxies of general food supply to the benthos, rose significantly after the transition from
ice-covered conditions in spring (March–June 2008) to open-water conditions in summer (June–August 2008), whereas sediment
Chl a concentrations, typical markers of fresh food input, did not. Macrobenthic biomass (including agglutinated foraminifera >500 μm)
varied significantly among sites (1.2–6.4 g C m−2 in spring, 1.1–12.6 g C m−2 in summer), whereas a general spring-to-summer increase was not detected. Benthic carbon remineralisation also ranged significantly
among sites (11.9–33.2 mg C m−2 day−1 in spring, 11.6–44.4 mg C m−2 day−1 in summer) and did in addition exhibit a general significant increase from spring-to-summer. Multiple regression analysis
suggests that in both spring and summer, sediment Chl a concentration is the prime determinant of benthic carbon remineralisation, but other factors have a significant secondary
influence, such as foraminiferan biomass (negative in both seasons), water depth (in spring) and infaunal biomass (in summer).
Our findings indicate the importance of the combined and dynamic effects of food supply and benthic community patterns on
the carbon remineralisation of the polar shelf benthos in seasonally ice-covered seas. 相似文献
5.
Sediments from Xuanwu Lake have been dredged in the past 3 years to improve the water quality, but methanogenesis should still
exist in the newly settled sediment. Methane production, methanogens, and physiochemical parameters were detected in the surface
sediments (0–5 cm) and/or vertical sediments (0–21 cm, segmented at interval of 3 cm). Methane flux at water–air interface
varied among five detected sites. Principal component analysis showed that CH4 flux, content of water and the concentration of total nitrogen (TN), CH4 and organic matters (OM) weighed most heavily on the component I in surface sediments while different patterns were observed
for vertical sediments. The copy number of the 16S rRNA gene for bacteria was lower in the surface sediment (0–6 cm) than
that in deeper sediments (12–21 cm), while 16S rRNA genes of Archaea were almost evenly distributed in the vertical sediments.
Representatives belonging to the orders Methanobacteriales, Methanomicrobiales, and Methanosarcinales were detected in all samples of the vertical sediments, except that no members of the Methanococcales were detected in the samples at 0–6 cm. The level of Methanobacteriales reached a highest density at 18.1 × 104 copies g−1 dry weight (dw) at 6–9 cm; for Methanosarcinales (76.89 × 106 copies g−1 dw) and Methanococcales (82.70 × 103 copies g−1 dw) at 12–15 cm, whereas for Methanomicrobiales (43.37 × 106 copies g−1 dw) at 9–12 cm. Methanosarcinaceae and Methanosaetaceae reached to their highest densities at 6–9 and 9–12 cm, respectively. These data provided useful information for better understanding
the methanogenesis in the newly settled sediments of a recently dredged lake. 相似文献
6.
Jana Woelfel Rhena Schumann Florian Peine Anita Flohr Aleksandra Kruss Jaroslaw Tegowski Philippe Blondel Christian Wiencke Ulf Karsten 《Polar Biology》2010,33(9):1239-1253
During summer 2007, Arctic microphytobenthic potential primary production was measured at several stations around the coastline
of Kongsfjorden (Svalbard, Norway) at ≤5 m water depth and at two stations at five different water depths (5, 10, 15, 20,
30 m). Oxygen planar optode sensor spots were used ex situ to determine oxygen exchange in the overlying water of intact sediment
cores under controlled light (ca. 100 μmol photons m−2 s−1) and temperature (2–4°C) conditions. Patches of microalgae (mainly diatoms) covering sandy sediments at water depths down
to 30 m showed high biomass of up to 317 mg chl a m−2. In spite of increasing water depth, no significant trend in “photoautotrophic active biomass” (chl a, ratio living/dead cells, cell sizes) and, thus, in primary production was measured at both stations. All sites from ≤5 to
30 m water depth exhibited variable rates of net production from −19 to +40 mg O2 m−2 h−1 (−168 to +360 mg C m−2 day−1) and gross production of about 2–62 mg O2 m−2 h−1 (17–554 mg C m−2 day−1), which is comparable to other polar as well as temperate regions. No relation between photoautotrophic biomass and gross/net
production values was found. Microphytobenthos demonstrated significant rates of primary production that is comparable to
pelagic production of Kongsfjorden and, hence, emphasised the importance as C source for the zoobenthos. 相似文献
7.
Makoto Sampei Hiroshi Sasaki Ryosuke Makabe Alexandre Forest Hiroshi Hattori Jean-��ric Tremblay Yves Gratton Mitsuo Fukuchi Louis Fortier 《Polar Biology》2011,34(4):501-511
Regional variability in the annual fluxes of particulate organic carbon (POC) and biogenic silica (Si) at the periphery of
the Mackenzie Shelf (Beaufort Sea) was investigated using eight long-term sediment traps moored at ~100-m depth. Relatively
high autochthonous POC and Si fluxes were recorded in the Mackenzie Trough (4.1 and 8.9 g m−2 year−1 respectively) and off Cape Bathurst (6.6 and 79 g m−2 year−1), two areas where upwelling events are frequently observed. Diatomaceous new production was minimum on the mid-slope of the
Mackenzie Shelf (2.8 g C m−2 year−1), moderate in the Mackenzie Trough (14.5 g C m−2 year−1), and highest off Cape Bathurst (128.7 g C m−2 year−1). High annual autochthonous POC flux corresponded to high diatom production. Among sites, the vertical attenuation of the
POC flux increased with diatomaceous new production. Hence, the retention of autochthonous POC in the surface layer (<100 m)
was highest (95%) at the highly productive site off Cape Bathurst, intermediate (72%) in the moderately productive Mackenzie
Trough, and low (4%) at the unproductive mid-slope of the shelf. Our results indicate that, on Arctic shelves, upwelling and
the production of diatoms increase the fraction of the POC which is retained in the surface layer and diverted to the pelagic
food web. In the relatively unproductive waters of the Arctic Ocean, biological hot spots such as the one identified off Cape
Bathurst where the food web promotes retention rather than vertical export could be disproportionately important as feeding
grounds for higher trophic levels. 相似文献
8.
Vertical distribution and abundance of juvenile chaetognaths in the Weddell Sea (Antarctica) 总被引:2,自引:0,他引:2
The composition, abundance and vertical distribution of chaetognaths were analysed along a transect in the Weddell Sea during
late spring. Three species were identified: Eukrohnia hamata (90.8%), Sagitta marri (6.4%) and S. gazellae (2.8%). Only juvenile stages were collected in the samples, a result related both to the type of sampling gear employed (mesh
size: 100 μm) and the species' life-cycles. The vertical distributions showed that the juvenile stages of these species tended
to aggregate at considerable depth (1000–500 m). It is postulated that this pattern may be related to the life-cycles of these
species in association with seasonal Antarctic conditions, similar to the pattern postulated for krill and other polar crustaceans.
Accepted: 10 July 2000 相似文献
9.
Elzbieta Krolak Jerzy Kwapulinski Agnieszka Fischer 《Radiation and environmental biophysics》2010,49(2):229-237
The vertical 137Cs profile of forest and wasteland soils was analyzed in the south of the Podlasie Lowland area (Eastern Poland) about 20 years
after the Chernobyl accident. In addition, the concentration of 40K in soils of the investigated area was measured. Below the litter layer (mean thickness 3 cm), the soil samples were collected
up to a depth of 12 cm and then divided into three layers: 0–3, 3–7, 7–12 cm. The behavior of 137Cs and 40K isotopes in soils was analyzed depending on the depth from which the soil samples were collected, as well as on the content
of organic carbon, pH of soil and its granulometric composition. It was established that the density of 137Cs in the litter layer equals 2.17 kBq m−2; it is the highest in layer 0–3 cm where it equals 3.44 kBq m−2, and it decreases with the depth to the value of 0.76 kBq m−2 in layer 7–12 cm. No similar pattern was observed in wasteland soils. The concentrations of 40K in forest and wasteland soils did not change significantly with depth. 相似文献
10.
Rodrigo S. P. de Skowronski Paula F. Gheller Sandra Bromberg Carlos J. David Mônica A. V. Petti Thaïs N. Corbisier 《Polar Biology》2009,32(6):839-851
The spatial and temporal variation of microphytobenthic biomass in the nearshore zone of Martel Inlet (King George Island,
Antarctica) was estimated at several sites and depths (10–60 m), during three summer periods (1996/1997, 1997/1998, 2004/2005).
The mean values were inversely related to the bathymetric gradient: higher ones at 10–20 m depth (136.2 ± 112.5 mg Chl a m−2, 261.7 ± 455.9 mg Phaeo m−2), intermediate at 20–30 m (55.6 ± 39.5 mg Chl a m−2, 108.8 ± 73.0 mg Phaeo m−2) and lower ones at 40–60 m (22.7 ± 23.7 mg Chl a m−2, 58.3 ± 38.9 mg Phaeo m−2). There was also a reduction in the Chl a/Phaeo ratio with depth, from 3.2 ± 3.2 (10–20 m) to 0.7 ± 1.0 (40–60 m), showing a higher contribution of senescent phytoplankton
and/or macroalgae debris at the deeper sites and the limited light flux reaching the bottom. Horizontal differences found
in the biomass throughout the inlet could not be clearly related to hydrodynamics or proximity to glaciers, but with sediment
characteristics. An inter-summer variation was observed: the first summer presented the highest microphytobenthic biomass
apparently related to more hydrodynamic conditions, which causes the deposition of allochthonous material. 相似文献
11.
E. A. Pakhomov J. Hall M. J. M. Williams B. P. V. Hunt C. J. Stevens 《Polar Biology》2011,34(2):257-271
Depth-stratified vertical sampling was carried out during the New Zealand International Polar Year cruise to the Ross Sea
on board the RV Tangaroa in February–March 2008. The distribution (horizontal and vertical), density and population biology of Salpa thompsoni were investigated. Salps were found at two of the four major sampling locations, e.g. near the continental slope of the Ross
Sea and in the vicinity of seamounts to the north of the Ross Sea. Both abundance and biomass of S. thompsoni were highest near the seamounts in the Antarctic Circumpolar Current reaching ~2,500 ind 1,000 m−3 and 8.2 g dry wt 1,000 m−3 in the water column sampled. The data showed that S. thompsoni populations were able to utilize horizontal and vertical discontinuities in water column structure, in particular the warm
Circumpolar Deep Water (CDW), to persist in the high Antarctic. Although salps appeared to continue migrating to the surface
colder layers to feed, both aggregate chain and young embryo release seem to be restricted to the CDW. This study for the
first time has provided evidence that low Antarctic salp species may successfully reproduce in the hostile high Antarctic
realm. 相似文献
12.
Klaus Martin Meiners S. Papadimitriou D. N. Thomas L. Norman G. S. Dieckmann 《Polar Biology》2009,32(7):1055-1065
Physical, biogeochemical and photosynthetic parameters were measured in sea ice brine and ice core bottom samples in the north-western
Weddell Sea during early spring 2006. Sea ice brines collected from sackholes were characterised by cold temperatures (range
−7.4 to −3.8°C), high salinities (range 61.4–118.0), and partly elevated dissolved oxygen concentrations (range 159–413 μmol kg−1) when compared to surface seawater. Nitrate (range 0.5–76.3 μmol kg−1), dissolved inorganic phosphate (range 0.2–7.0 μmol kg−1) and silicic acid (range 74–285 μmol kg−1) concentrations in sea ice brines were depleted when compared to surface seawater. In contrast, NH4
+ (range 0.3–23.0 μmol kg−1) and dissolved organic carbon (range 140–707 μmol kg−1) were enriched in the sea ice brines. Ice core bottom samples exhibited moderate temperatures and brine salinities, but high
algal biomass (4.9–435.5 μg Chl a l−1 brine) and silicic acid depletion. Pulse amplitude modulated fluorometry was used for the determination of the photosynthetic
parameters F
v/F
m, α, rETRmax and E
k. The maximum quantum yield of photosystem II, F
v/F
m, ranged from 0.101 to 0.500 (average 0.284 ± 0.132) and 0.235 to 0.595 (average 0.368 ± 0.127) in the sea ice internal and
bottom communities, respectively. The fluorometric measurements indicated medium ice algal photosynthetic activity both in
the internal and bottom communities of the sea ice. An observed lack of correlation between biogeochemical and photosynthetic
parameters was most likely due to temporally and spatially decoupled physical and biological processes in the sea ice brine
channel system, and was also influenced by the temporal and spatial resolution of applied sampling techniques. 相似文献
13.
Toshiya Katano Shin-ichi Nakano Hiroyuki Ueno Osamu Mitamura Kaori Anbutsu Masayuki Kihira Yasuhiro Satoh Takeshi Satoh Valentin V. Drucker Yuji Tanaka Yuki Akagashi Masahito Sugiyama 《Limnology》2008,9(3):243-250
The abundance and composition of phytoplankton were investigated at six stations along a transect from the Barguzin River
inflow to the central basin of Lake Baikal in August 2002 to clarify the effect of the river inflow on the phytoplankton community
in the lake. The water temperature in the epilimnion was high near the shore at Station 1 (17.3°C), probably due to the higher
temperature of the river water, and gradually decreased offshore at Station 6 (14.5°C). Thermal stratification developed at
Stations 2–6, and a thermocline was observed at a 17–22-m depth at Stations 2–4 and an 8–12-m depth at Stations 5 and 6. The
concentrations of nitrogen and phosphorus nutrients in the epilimnion at all stations were <1.0 μmol N l−1 and <0.16 μmol P l−1, respectively. Relatively high concentrations of nutrients (0.56–7.38 μmol N l−1 and 0.03–0.28 μmol P l−1) were detected in the deeper parts of the euphotic zone. Silicate was not exhausted at all stations (>20 μmol Si l−1). The chlorophyll a (chl. a) concentration was high (>10 μg l−1) near the shore at Station 1 and low (<3 μg l−1) at five other stations. The <2 μm fraction of chl. a in Stations 2–6 ranged between 0.80 and 1.85 μg l−1, and its contribution to total chl. a was high (>60%). In this fraction, picocyanobacteria were abundant at all stations and ranged between 5 × 104 and 5 × 105 cells ml−1. In contrast, chl. a in the >2 μm fraction varied significantly (0.14–11.17 μg l−1), and the highest value was observed at Station 1. In this fraction, the dominant phytoplankton was Aulacoseira and centric diatoms at Station 1 and Cryptomonas, Ankistrodesmus, Asterionella, and Nitzschia at Stations 2–6. The present study demonstrated the dominance of picophytoplankton in the pelagic zone, while higher abundance
of phytoplankton dominated by diatoms was observed in the shallower littoral zone. These larger phytoplankters in the littoral
zone probably depend on nutrients from the Barguzin River. 相似文献
14.
Motomi Genkai-Kato Miyuki Onishi Hideyuki Doi Kentaro Nozaki Kenji Yoshino Hitoshi Miyasaka Koji Omori 《Ecological Research》2008,23(6):1025-1032
We investigated the photosynthesis–light intensity (P–I) relationships of phytoplankton collected from a sublittoral sand
bank in the Seto Inland Sea, Japan, under different temperature conditions. In spite of low chlorophyll a concentration (<3 mg m−3), phytoplankton had considerably high photosynthetic potential (>10 mg C (mg chl a)−1 h−1) in the study area. Based on the P–I relationships, we conducted numerical simulation of areal primary production using published
data on water temperature, chlorophyll a concentration, and irradiance. The areal primary production ranged between 159 and 187 g C m−2 year−1. This production was within the range of typical values reported previously in deeper areas of the Seto Inland Sea. The productivity
in the sand bank area was discussed in relation to water current, allochthonous resource input, and fisheries. 相似文献
15.
Altitudinal changes in carbon storage of temperate forests on Mt Changbai, Northeast China 总被引:8,自引:0,他引:8
Biao Zhu Xiangping Wang Jingyun Fang Shilong Piao Haihua Shen Shuqing Zhao Changhui Peng 《Journal of plant research》2010,123(4):439-452
A number of studies have investigated regional and continental scale patterns of carbon (C) stocks in forest ecosystems; however,
the altitudinal changes in C storage in different components (vegetation, detritus, and soil) of forest ecosystems remain
poorly understood. In this study, we measured C stocks of vegetation, detritus, and soil of 22 forest plots along an altitudinal
gradient of 700–2,000 m to quantify altitudinal changes in carbon storage of major forest ecosystems (Pinus koraiensis and broadleaf mixed forest, 700–1,100 m; Picea and Abies forest, 1,100–1,800 m; and Betula ermanii forest, 1,800–2,000 m) on Mt Changbai, Northeast China. Total ecosystem C density (carbon stock per hectare) averaged 237 t C ha−1 (ranging from 112 to 338 t C ha−1) across all the forest stands, of which 153 t C ha−1 (52–245 t C ha−1) was stored in vegetation biomass, 14 t C ha−1 (2.2–48 t C ha−1) in forest detritus (including standing dead trees, fallen trees, and floor material), and 70 t C ha−1 (35–113 t C ha−1) in soil organic matter (1-m depth). Among all the forest types, the lowest vegetation and total C density but the highest
soil organic carbon (SOC) density occurred in Betula ermanii forest, whereas the highest detritus C density was observed in Picea and Abies forest. The C density of the three ecosystem components showed distinct altitudinal patterns: with increasing altitude, vegetation
C density decreased significantly, detritus C density first increased and then decreased, and SOC density exhibited increasing
but insignificant trends. The allocation of total ecosystem C to each component exhibited similar but more significant trends
along the altitudinal gradient. Our results suggest that carbon storage and partitioning among different components in temperate
forests on Mt Changbai vary greatly with forest type and altitude. 相似文献
16.
Deepa Dhital Yuichiro Yashiro Toshiyuki Ohtsuka Hibiki Noda Yoko Shizu Hiroshi Koizumi 《Journal of plant research》2010,123(4):519-530
The ecosystem carbon budget was estimated in a Japanese Zoysia japonica grassland. The green biomass started to grow in May and peaked from mid-July to September. Seasonal variations in soil CO2 flux and root respiration were mediated by changes in soil temperature. Annual soil CO2 flux was 1,121.4 and 1,213.6 g C m−2 and root respiration was 471.0 and 544.3 g C m−2 in 2007 and 2008, respectively. The root respiration contribution to soil CO2 flux ranged from 33% to 71%. During the growing season, net primary production (NPP) was 747.5 and 770.1 g C m−2 in 2007 and 2008, respectively. The biomass removed by livestock grazing (GL) was 122.1 and 102.7 g C m−2, and the livestock returned 28.2 and 25.6 g C m−2 as fecal input (FI) in 2007 and 2008, respectively. The decomposition of FI (DL, the dry weight loss due to decomposition)
was very low, 1.5 and 1.4 g C m−2, in 2007 and 2008. Based on the values of annual NPP, soil CO2 flux, root respiration, GL, FI, and DL, the estimated carbon budget of the grassland was 1.7 and 22.3 g C m−2 in 2007 and 2008, respectively. Thus, the carbon budget of this Z. japonica grassland ecosystem remained in equilibrium with the atmosphere under current grazing conditions over the 2 years of the
study. 相似文献
17.
Changes in soil carbon flux and carbon stock over a rotation of poplar plantations in northwest China 总被引:2,自引:0,他引:2
Forest soil is a major component of terrestrial ecosystems for carbon sequestration and plays an important role in the global
carbon cycle. Soil carbon flux and soil carbon pools were investigated in a poplar plantation chronosequence over a rotation
in northwest China. Based on continuous field observation in 2007, the results showed that mean soil CO2 efflux rate was 5.54, 4.81, and 3.93 μmol CO2 m−2 s−1 for stands of 2-, 8-, and 15-year-old, respectively, during the growing season. Significant differences in soil respiration
of three age classes were mainly because soil temperature, carbon allocation, and fine root growth changed greatly with stand
age. Multiple regression analysis suggested that soil temperature and fine root biomass in the upper layer could explain 78–85%
of the variation in soil respiration. Mineral soil C stock at 0–40 cm depth was 55.77, 55.09, and 58.14 t ha−1 in the 2-, 8-, and 15-year-old stands, respectively. The average rate of soil C sequestration was 0.13 t ha−1 year−1 following afforestation on former crop lands. Although the plantations had similar management practices and soil types since
their establishment, many biotic and abiotic factors such as root biomass and turnover rate, soil condition of the plantations
had undergone marked changes at different development stages, which could result in the remarkable differences in soil carbon
flux and storage over a rotation. Our results highlight the importance of the development stage within a rotation of poplar
plantation in assessment of soil carbon budget. 相似文献
18.
N. G. A. Ekelund C. A. Nygård R. Nordström A. M. Gylle 《Journal of applied phycology》2008,20(5):751-756
The brown alga Fucus vesiculous is one of the few marine species in the Baltic Sea. Fucus vesiculosus shows high morphological and physiological variability as a response to its environmental conditions. The salinity in the
Baltic Sea is 4–5 psu, compared to 35 psu in the Atlantic. Photosynthesis of algae is usually measured after collection and
transportation to constant culture conditions. However, in this study, relative photosynthetic electron transport rates, calculated
from chlorophyll a fluorescence parameters were compared in algae collected from 1 and 4 m depths by SCUBA divers. Measurements of light response
curves from the same individuals of F. vesiculosus at different depths and times of the year have, to our knowledge, not been made previously. Measurements were performed on
four different occasions during the spring of 2005 (25 February, 3 and 29 April, and 26 May) in the Baltic Sea, using rapid
light curves generated with a Diving PAM. In addition, samples were collected for photoinhibition studies in the laboratory.
The light response curves obtained in situ at 1 and 4 m depths for F. vesiculosus showed lower values of light saturation with depth. When algae from 1 and 4 m depths were exposed to high irradiances of
photosynthetically active radiation (1,400 μmol photons m−2 s−1), algae from 1 m depth showed a higher degree of photoinhibition in comparison to algae from 4 m depth. 相似文献
19.
Photosynthetic parameters of phytoplankton and sea ice algae from landfast sea ice of the Chukchi Sea off Point Barrow, Alaska,
were assessed in spring 2005 and winter through spring 2006 using Pulse Amplitude Modulated (PAM) fluorometry including estimates
of maximum quantum efficiency (F
v/F
m), maximum relative electron transport rate (rETRmax), photosynthetic efficiency (α), and the photoadaptive index (E
k). The use of centrifuged brine samples allowed to document vertical gradients in ice algal acclimation with 5 cm vertical
resolution for the first time. Bottom ice algae (0–5 cm from ice–water interface) expressed low F
v/F
m (0.331–0.426) and low α (0.098–0.130 (μmol photons m−2s−1)−1) in December. F
v/F
m and α increased in March and May (0.468–0.588 and 0.141–0.438 (μmol photons m−2s−1)−1, respectively) indicating increased photosynthetic activity. In addition, increases in rETRmax (3.3–16.4 a.u.) and E
k (20–88 μmol photons m−2 s−1) from December to May illustrates a higher potential for primary productivity as communities become better acclimated to
under-ice light conditions. In conclusion, photosynthetic performance by ice algae (as assessed by PAM fluorometry) was tightly
linked to sea ice salinity, temperature, and inorganic nutrient concentrations (mainly nitrogen). 相似文献
20.
Daria M. Martynova Natalia A. Kazus Ulrich V. Bathmann Martin Graeve Alexey A. Sukhotin 《Polar Biology》2011,34(8):1175-1195
We have studied the seasonal dynamics of abundance and feeding characteristics of three species of calanoid copepods (Acartia spp., Centropages hamatus and Temora longicornis) in the White Sea from the surface water layer (0–10 m), in order to assess their role in the pelagic food web and to determine
the major factors governing their population dynamics during the productive season. These species dominated in the upper water
layer (0–10 m) from June through September, producing up to 3 generations per year. Data on the food spectra revealed all
species to be omnivorous; but some inter- and intraspecific differences were observed. Generally, copepods consumed diatoms,
dinoflagellates and microzooplankton. The omnivory index ‘UC’ (i.e., fatty acid unsaturation coefficient) varied from 0.2
to 0.6, which implied ingestion of phytoplankton. The different degree of selectivity on the same food items by the studied
species was observed, and therefore, successful surviving strategy with minimal overlapping could be assumed. In total, the
populations of the three studied copepod species grazed up to 2.15 g C m−2 day−1 and released up to 0.68 g C m−2 day−1 in faecal pellets. They consumed up to 50% of particulate organic carbon, or up to 85% of phytoplankton standing stock (in
terms of Chl. a), and thus played a significant role in the transformation of particulate organic matter. Seasonal changes in abundance of
the studied species depended mostly on water temperature in the early summer, but were also affected by food availability
(Chl. a concentration) during the productive season. 相似文献