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1.
Antonio Pusceddu Antonio Dell’Anno Luigi Vezzulli Mauro Fabiano Vincenzo Saggiomo Stefano Cozzi Giulio Catalano Letterio Guglielmo 《Polar Biology》2009,32(3):337-346
We investigated organic carbon quantity and biochemical composition, prokaryotic abundance, biomass and carbon production
in the annual and platelet sea ice of Terra Nova Bay (Antarctica), as well as the downward fluxes of organic matter released
by melting ice during early spring. Huge amounts of biopolymeric C accumulated in the bottom layer of the ice column concomitantly
with the early spring increase in sympagic algal biomass. Such organic material, mostly accounted for by autotrophic biomass,
was characterised by a high food quality and was rapidly exported to the sea bottom during sea ice melting. Prokaryote abundance
(up to 1.3 × 109 cells L−1) and extracellular enzymatic activities (up to 24.3 μM h−1 for amino-peptidase activity) were extremely high, indicating high rates of organic C degradation in the bottom sea ice.
Despite this, prokaryote C production values were very low (range 5–30 ng C L−1 h−1), suggesting that most of the degraded organic C was not channelled into prokaryote biomass. In the platelet ice, we found
similar organic C concentrations, prokaryote abundance and biomass values and even higher extracellular enzymatic activities,
but values of prokaryote C production (range 800–4,200 ng C L−1 h−1) were up to three orders of magnitude higher than in the intact bottom sea ice. Additional field and laboratory experiments
revealed that the dissolved organic material derived from algae accumulating in the bottom sea ice significantly reduced prokaryote
C production, suggesting the presence of a potential allopathic control of sympagic algae on prokaryote growth.
This article belongs to a special topic: Five articles on Sea-ice communities in Terra Nova Bay (Ross Sea), coordinated by
L. Guglielmo and V. Saggiomo, appear in this issue of Polar Biology. The studies were conducted in the frame of the National
Program of Research in Antarctica (PNRA) of Italy. 相似文献
2.
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
3.
Net growth of ice algae in response to changes in overlying snow cover was studied after manipulating snow thickness on land-fast,
Arctic sea ice. Parallel laboratory experiments measured the effect of changing irradiance on growth rate of the ice diatom,
Nitzschia frigida. After complete removal of thick snow (≥9 cm), in situ ice algae biomass declined (over 7–12 days), while removal of thin
snow layers (4–5 cm), or partial snow removal, increased net algal growth. Ice bottom ablation sometimes followed snow removal,
but did not always result in net loss of algae. Similarly, in laboratory experiments, small increases in irradiance increased
algal growth rate, while greater light shifts suppressed growth for 3–6 days. However, N. frigida could acclimate to relatively high irradiance (110 μmol photons m2 s−1). The results suggest that algal loss following removal of a thick snow layer was due to the combination of photoinhibition
and bottom ablation. The smaller relative increase in irradiance after removal of thin or partial snow layers allowed algae
to maintain high specific-growth rates that compensated for loss from physical mechanisms. Thus, the response of ice algae
to snow loss depends both on the amount of change in snow depth and algal photophysiology. The complex response of ice algae
growth and export loss to frequently changing snow fields may contribute to horizontal and temporal patchiness of ecologically
and biogeochemically important variables in sea ice and should be considered in predictions of how climate change will affect
Arctic marine ecosystems. 相似文献
4.
Pack ice around Svalbard was sampled during the expedition ARK XIX/1 of RV “Polarstern” (March–April 2003) in order to determine
environmental conditions, species composition and abundances of sea-ice algae and heterotrophic protists during late winter.
As compared to other seasons, species diversity of algae (total 40 taxa) was not low, but abundances (5,000–448,000 cells l−1) were lower by one to two orders of magnitude. Layers of high algal abundances were observed both at the bottom and in the
ice interior. Inorganic nutrient concentrations (NO2, NO3, PO4, Si(OH)4) within the ice were mostly higher than during other seasons, and enriched compared to seawater by enrichment indices of
1.6–24.6 (corrected for losses through the desalination process). Thus, the survival of algae in Arctic pack ice was not limited
by nutrients at the beginning of the productive season. Based on less-detailed physical data, light was considered as the
most probable factor controlling the onset of the spring ice-algal bloom in the lower part of the ice, while low temperatures
and salinities inhibit algal growth in the upper part of the ice at the end of the winter. Incorporation of ice algae probably
took place during the entire freezing period. Possible overwintering strategies during the dark period, such as facultative
heterotrophy, energy reserves, and resting spores are discussed. 相似文献
5.
L. Guglielmo G. C. Carrada G. Catalano A. Dell'Anno M. Fabiano L. Lazzara O. Mangoni A. Pusceddu V. Saggiomo 《Polar Biology》2000,23(2):137-146
Studies on the chemical and biological properties of annual pack ice at a coastal station in Terra Nova Bay (74°41.72′S,
164°11.63′E) were carried out during austral spring at 3-day intervals from 5 November to 1 December 1997. Temporal changes
of nutrient concentrations, algal biomasses, taxonomic composition, photosynthetic pigment spectra and P–E relationships were
studied. Quantity, composition and degradation rates of organic matter in the intact sea ice were also investigated. In addition,
microcosm experiments were carried out to evaluate photosynthetic and photo-acclimation processes of the sympagic flora in
relation to different light regimes. High concentrations of ammonia were measured in four ice-cores (weighted mean values
of the cores ranged from 4.3 ± 1.9 μM to 7.2 ± 3.4 μM), whereas nitrate and phosphate displayed high concentrations (up to
35.9 μM and 7.6 μM, respectively) only in the bottom layer (135–145 cm depth). Particulate carbohydrate and protein concentrations
in the intact sea ice ranged from 0.5 to 2.3 mg l−1 and 0.2 to 2.0 mg l−1, respectively, displaying a notable accumulation of organic matter in the bottom colored layer, where bacterial enzymatic
activities also reached the highest values. Aminopeptidase activity was extremely high (up to 19.7 μM l−1 h−1 ± 0.05 in the bottom layer), suggesting a rapid turnover rate of nitrogen–enriched organic compounds (e.g. proteins). By
contrast, bacterial secondary production was low, suggesting that only a very small fraction of mobilized organic matter was
converted into bacterial biomass (<0.01‰). The sympagic autotrophic biomass (in terms of chlorophaeopigments) of the bottom
layer was high, increasing during the sampling period from 680 to 2480 μg l−1. Analyses of pigments performed by HPLC, as well as microscope observations, indicated that diatoms dominated bottom communities.
The most important species were Amphiprora sp. and Nitschia cfr. stellata. Bottom sympagic communities showed an average P
B
max
of 0.12 mgC mg Chl−1 and low photoadaptation index (E
k=18 μE m−2 s−1, E
m=65 μE m−2 s−1). Results of the microcosm experiment also indicated that communities were photo-oxidized when irradiance exceeded 100 μE m−2 s−1. This result suggests that micro- autotrophs inhabiting sea ice might have a minor role in the pelagic algal blooms.
Accepted: 4 August 1999 相似文献
6.
Preliminary investigation of Okhotsk Sea ice algae; taxonomic composition and photosynthetic activity 总被引:1,自引:1,他引:0
Okhotsk Sea pack ice from Shiretoko in northern Hokkaido, sampled in March 2007, contained microalgal communities dominated
by the centric diatoms Thalassiosira
nordenskioeldi and T. punctigera. Domination by this genus is very unusual in sea ice. Communities from nearby fast ice at Saroma-ko lagoon were dominated by Detonula conferavea and Odontella aurita. Average microalgal biomass of the Okhotsk Sea pack ice (surface and bottom) was 1.59 ± 1.09 μg chla l−1 and for fast ice (bottom only) at nearby Saroma-ko lagoon, 16.5 ± 3.2 μg l−1 (=31.1 ± 5.0 mg chla m−2). Maximum quantum yield of the Shiretoko pack ice algal communities was 0.618 ± 0.056 with species-specific data ranging
between 0.211 and 0.653. These community values are amongst the highest recorded for sea ice algae. Rapid light curves (RLC) on individual cells indicated maximum relative electron transfer rates (relETR) between 20.8 and
60.6, photosynthetic efficiency values (α) between 0.31 and 0.93 and onset of saturation values (E
k) between 33 and 91 μmol photons m−2 s−1. These data imply that the pack ice algal community at Shiretoko was healthy and actively photosynthesising. Maximum quantum
yield of the Saroma-ko fast ice community was 0.401 ± 0.086, with values for different species between 0.361 and 0.560. RLC
data from individual Saroma-ko fast ice algal cells indicated relETR between 55.3 and 60.6, α values between 0.609 and 0.816
and E
k values between 74 and 91 μmol photons m−2 s−1 which are consistent with measurements in previous years. 相似文献
7.
Landfast ice algal communities were studied in the strongly riverine-influenced northernmost part of the Baltic Sea, the Bothnian
Bay, during the winter-spring transition of 2004. The under-ice river plume, detected by its low salinity and elevated nutrient
concentrations, was observed only at the station closest to the river mouth. The bottommost ice layer at this station was
formed from the plume water (brine volume 0.71%). This was reflected by the low flagellate-dominated (93%) algal biomass in
the bottom layer, which was one-fifth of the diatom-dominated (74%) surface-layer biomass of 88 μg C l−1. Our results indicate that habitable space plays a controlling role for ice algae in the Bothnian Bay fast ice. Similarly
to the water column in the Bothnian Bay, average dissolved inorganic N:P-ratios in the ice were high, varying between 12 and
265. The integrated chlorophyll a (0.1–2.2 mg m−2) and algal biomass in the ice (1–31 mg C m−2) correlated significantly (Spearman ρ = 0.79), with the highest values being measured close to the river mouth in March and during the melt season in April. Flagellates
<20 μm generally dominated in both the ice and water columns in February–March. In April the main ice-algal biomass was composed
of Melosira arctica and unidentified pennate diatoms, while in the water column Achnanthes taeniata, Scrippsiella hangoei and flagellates dominated. The photosynthetic efficiency (0.003–0.013 (μg C [μg chl a
−1] h−1)(μE m−2s−1)−1) and maximum capacity (0.18–1.11 μg C [μg chl a
−1] h−1) could not always be linked to the algal composition, but in the case of a clear diatom dominance, pennate species showed
to be more dark-adapted than centric diatoms. 相似文献
8.
The algal, protozoan and metazoan communities within different drift-ice types (newly formed, pancake and rafted ice) and
in under-ice water were studied in the Gulf of Bothnia in March 2006. In ice, diatoms together with unidentified flagellates
dominated the algal biomass (226 ± 154 μg ww l−1) and rotifers the metazoan and protozoan biomass (32 ± 25 μg ww l−1). The under-ice water communities were dominated by flagellates and ciliates, which resulted in lower biomasses (97 ± 25
and 21 ± 14 μg ww l−1, respectively). The under-ice water and newly formed ice separated from all other samples to their own cluster in hierarchical
cluster analysis. The most important discriminating factors, according to discriminant analysis, were chlorophyll-a, phosphate and silicate. The under-ice water/newly formed ice cluster was characterized by high nutrient and low chlorophyll-a values, while the opposite held true for the ice cluster. Increasing trends in chlorophyll-a concentration and biomass were observed with increasing ice thickness. Within the thick ice columns (>40 cm), the highest
chlorophyll-a concentrations (6.6–22.2 μg l−1) were in the bottom layers indicating photoacclimation of the sympagic community. The ice algal biomass showed additional
peaks in the centric diatom-dominated surface layers coinciding with the highest photosynthetic efficiencies [0.019–0.032 μg C (μg Chl-a
−1 h−1) (μE m−2 s−1)−1] and maximum photosynthetic capacities [0.43-1.29 μg C (μg Chl-a
−1 h−1)]. Rafting and snow-ice formation, determined from thin sections and stable oxygen isotopic composition, strongly influenced
the physical, chemical and biological properties of the ice. Snow-ice formation provided the surface layers with nutrients
and possibly habitable space, which seemed to have favored centric diatoms in our study. 相似文献
9.
Zamalloa C De Vrieze J Boon N Verstraete W 《Applied microbiology and biotechnology》2012,93(2):859-869
The biomass of industrially grown Phaeodactylum tricornutum was subjected in a novel way to bio-methanation at 33°C, i.e., in an anaerobic membrane bioreactor (AnMBR) at a hydraulic
retention time of 2.5 days, at solid retention times of 20 to 10 days and at loading rates in the range of 2.6–5.9 g biomass-COD L−1 day−1 with membrane fluxes ranging from 1 to 0.8 L m−2 h−1. The total COD recovered as biogas was in the order of 52%. The input suspension was converted to a clear effluent rich in
total ammonium nitrogen (546 mg TAN L−1) and phosphate (141 mg PO4-P L−1) usable as liquid fertilizer. The microbial community richness, dynamics, and organization in the reactor were interpreted
using the microbial resource management approach. The AnMBR communities were found to be moderate in species richness and
low in dynamics and community organization relative to UASB and conventional CSTR sludges. Quantitative polymerase chain reaction
analysis revealed that Methanosaeta sp. was the dominant acetoclastic methanogen species followed by Methanosarcina sp. This work demonstrated that the use of AnMBR for the digestion of algal biomass is possible. The fact that some 50% of
the organic matter is not liquefied means that the algal particulates in the digestate constitute a considerable fraction
which should be valorized properly, for instance as slow release organic fertilizer. Overall, 1 kg of algae dry matter (DM)
could be valorized in the form of biogas (€2.07), N and P in the effluent (€0.02) and N and P in the digestate (€0.04), thus
totaling about €2.13 per kilogram algae DM. 相似文献
10.
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
11.
Influence of sea ice on the composition of the spring phytoplankton bloom in the northern Baltic Sea 总被引:5,自引:2,他引:3
During the late winter and spring of 1994, the influence of sea ice on phytoplankton succession in the water was studied
at a coastal station in the northern Baltic Sea. Ice cores were taken together with water samples from the underlying water
and analysed for algal composition, chlorophyll a and nutrients. Sediment traps were placed under the ice and near the bottom, and the sedimented material was analysed for
algal composition. The highest concentration of ice algae (4.1 mmol C m−2) was found shortly before ice break-up in the middle of April, coincidental with the onset of an under-ice phytoplankton
bloom. The ice algae were dominated by the diatoms Chaetoceros wighamii Brightwell, Melosira arctica (Ehrenberg) Dickie and Nitzschia frigida Grunow. Under the ice the diatom Achnanthes taeniata Grunow and the dinoflagellate Peridiniella catenata (Levander) Balech were dominant. Calculations of sinking rates and residence times of the dominant ice algal species in the
photic water column indicated that only one ice algal species (Chaetoceros wighamii) had a seeding effect on the water column: this diatom dominated the spring phytoplankton bloom in the water together with
Achnanthes taeniata and Peridiniella catenata.
Received: 9 May 1997 / Accepted: 15 February 1998 相似文献
12.
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
13.
Microscale photographs were taken of the ice bottom to examine linkages of algal chlorophyll a (chl a) biomass distribution with bottom ice features in thick Arctic first-year sea ice during a spring field program which took
place from May 5 to 21, 2003. The photographic technique developed in this paper has resulted in the first in situ observations
of microscale variability in bottom ice algae distribution in Arctic first-year sea ice in relation to ice morphology. Observations
of brine channel diameter (1.65–2.68 mm) and number density (5.33–10.35 per 100 cm2) showed that the number of these channels at the bottom of thick first-year sea ice may be greater than previously measured
on extracted ice samples. A variogram analysis showed that over areas of low chl a biomass (≤20.7 mg chl a m−2), patchiness in bottom ice chl a biomass was at the scale of brine layer spacing and small brine channels (∼1–3 mm). Over areas of high chl a biomass (≥34.6 mg chl a m−2), patchiness in biomass was related to the spacing of larger brine channels on the ice bottom (∼10–26 mm). Brine layers and
channels are thought to provide microscale maxima of light, nutrient replenishment and space availability which would explain
the small scale patchiness over areas of low algal biomass. However, ice melt and erosion near brine channels may play a more
important role in areas with high algal biomass and low snow cover. 相似文献
14.
Janne-Markus Rintala Jonna Piiparinen Jens Ehn Riitta Autio Harri Kuosa 《Hydrobiologia》2006,554(1):11-24
The response of Baltic Sea ice communities to changing light climate was studied in three subsequent 3 week in situ experiments on the SW coast of Finland. The investigation covered three different winter periods, short day with low solar
angles leading to limited light in the ice, late winter with deep snow cover and early spring with melting snow and increasing
light availability. The experimental setup consisted of transparent (no snow) and completely darkened (heavy snow cover) plexiglass
tubes in which the ice cores were incubated in situ from 1 to 2 weeks. Changes in the concentrations of inorganic nutrients (NO3−-–N, PO43−-–P, SiO4−-–Si) and chlorophyll-a concentration in the phytoplankton community composition were recorded as responses to different light manipulations. Changes
in inner ice light intensity in untreated ice as well as the temperature both in air and ice were recorded over the entire
study period. Increased irradiance in late winter/early spring and during meltdown affected the chlorophyll-a amount in the sea ice. During these periods the phytoplankton community in the top layers decreased possibly as a consequence
of photo-acclimation. Closer to the bottom of the ice, however, the increased inner ice light intensity induced algal growth.
Complete exclusion of light stopped the algal growth in the whole ice column. Darkening the ice cores also slowed down the
ice melting opposite to accelerated melting caused by increased light. The significant differences found in nutrient concentrations
between the light and dark treatments were mostly explicable by changes in algal biomass. No obvious changes were observed
in the phytoplankton community composition due to light manipulation, diatoms and heterotrophic flagellates dominating throughout
the study period. 相似文献
15.
The dissolved oxygen concentration (DO) was sampled during a diurnal cycle in three water holes heavily used by wildlife and
with distinctive biological features along the Seronera River. The DO fluctuated widely (by up to 11.5 mg l−1) as a function of time, mechanical stirring and aeration by animals, and the presence of fringing wetlands. The DO cycle
was successfully modeled (within 0.3 mg l−1) by assuming that the four dominant processes were photosynthesis and respiration by algae near the surface, trapping by
wetlands, decomposition of dead organic matter on the bottom, and stirring/aeration by hippos. The rate of DO decline from
the decay of dead organic matter was equal to the rate of DO removal by algal respiration at night. 相似文献
16.
Evidence for active microbial nitrogen transformations in sea ice (Gulf of Bothnia, Baltic Sea) in midwinter 总被引:5,自引:3,他引:2
Hermanni Kaartokallio 《Polar Biology》2001,24(1):21-28
Nutrient concentrations, chlorophyll-a, bacterial biomass and relative activity of denitrifying organisms were investigated from ice-core, brine and underlying
water samples in February 1998 in the Gulf of Bothnia, Baltic Sea. Examined sea ice was typical for the Baltic Sea; ice bulk
salinity varied from 0.1 to 1.6 psu, and in underlying water salinity was from 4.2 to 4.7 psu. In 2- to 3-months-old sea ice
(thickness 0.4–0.6 m), sea-ice communities were at the winter stage; chl-a concentrations were generally below 1 mg m−3 and heterotrophic organisms composed 7–20% of organism assemblage. In 1-month-old ice (thickness 0.2–0.25 m), an ice spring
bloom was already developing and chl-a concentrations were up to 5.6 mg m−3. In relation to low salinity, high concentrations of NH+
4, NO−
2, PO3+
4 and SiOH4 were found in the ice column. The results suggest that the upper part of ice accumulates atmospheric nutrient load during
the ice season, and nutrients in the upper 10–20 cm of ice are mainly of atmospheric origin. The most important biological
processes controlling the sea-ice nutrient status are nutrient regeneration, nutrient uptake and nitrogen transformations.
Nutrient regeneration is specially active in the middle parts of the 50- to 60-cm-thick ice and subsequent accumulation of
nutrients probably enhances the ice spring bloom. Nitrite accumulation and denitrifying activity were located in the same
ice layers with nutrient regeneration, which together with the observed significant correlation between the concentrations
of nitrogenous nutrients points to active nitrogen transformations occurring in the interior layers of sea ice in the Baltic
Sea.
Accepted: 12 June 2000 相似文献
17.
Currently, the impact of declining seasonal sea ice extent in the Arctic on polar food webs remains uncertain. Previously,
a range of proxy techniques has been employed to determine links between sea ice or phytoplankton primary production and the
Arctic marine food web, although it is accepted that such approaches have their limitations. Here, we propose a novel approach
to tracing sea ice primary production through Arctic food webs using the sea ice diatom biomarker, IP25. Various benthic macrofaunal specimens were collected between March and May 2008 from Franklin Bay in the Amundsen Gulf,
Arctic Canada, as part of the International Polar Year–Circumpolar Flaw Lead system study. Each specimen was analysed for
the presence of the sea ice diatom biomarker IP25 in order to provide evidence for feeding by benthic organisms on sea ice algae. IP25 was found in nineteen out of the twenty-one specimens analysed, often as the most abundant of the highly branched isoprenoid
biomarkers detected. The stable isotope composition of IP25 (δ13C = −17.1 ± 0.5‰) in the sea urchin (Strongylocentrotus sp.) specimens was similar to that reported previously for this biomarker in Arctic sea ice, sedimenting particles and sediments.
It is concluded that detection of IP25 in Arctic benthic macrofauna represents a novel approach to providing convincing evidence for feeding on sea ice algae. It
is also proposed that analysis of IP25 may be used to trace trophic transfer of sea ice algal-derived organic matter through Arctic food webs in the future. 相似文献
18.
Catabolic diversity of periphyton and detritus microbial communities in a subtropical wetland 总被引:1,自引:0,他引:1
The catabolic diversity of wetland microbial communities may be a sensitive indicator of nutrient loading or changes in environmental
conditions. The objectives of this study were to assess the response of periphyton and microbial communities in water conservation
area-2a (WCA-2a) of the Everglades to additions of C-substrates and inorganic nutrients. Carbon dioxide and CH4 production rates were measured using 14 days incubation for periphyton, which typifies oligotrophic areas, and detritus,
which is prevalent at P-impacted areas of WCA-2a. The wetland was characterized by decreasing P levels from peripheral to
interior, oligotrophic areas. Microbial biomass and N mineralization rates were higher for oligotrophic periphyton than detritus.
Methane production rates were also higher for unamended periphyton (80 mg CH4-C kg−1 d−1) than detritus (22 mg CH4-C kg−1 d−1), even though the organic matter content was higher for detritus (80%) than periphyton (69%). Carbon dioxide production for
unamended periphyton (222 mg CO2-C kg−1 d−1) was significantly greater than unamended detritus (84 mg CO2-C kg−1 d−1). The response of the heterotrophic microbial community to added C-substrates was related to the nutrient status of the wetland,
as substrate-induced respiration (SIR) was higher for detritus than periphyton. Amides and polysaccharides stimulated SIR
more than other C-substrates, and methanogenesis was greater contributor to SIR for periphyton than detritus. Inorganic P
addition stimulated CO2 and CH4 production for periphyton but not detritus, indicating a P limitation in the interior areas of WCA-2a. Continued nutrient
loading into oligotrophic areas of WCA-2a or enhanced internal nutrient cycling may stimulate organic matter decomposition
and further contribute to undesirable changes to the Everglades ecosystem caused by nutrient enrichment. 相似文献
19.
Denitrification activity and oxygen dynamics in Arctic sea ice 总被引:1,自引:0,他引:1
Søren Rysgaard Ronnie N. Glud Mikael K. Sejr Martin E. Blicher Henrik J. Stahl 《Polar Biology》2008,31(5):527-537
Denitrification and oxygen dynamics were investigated in the sea ice of Franklin Bay (70°N), Canada. These investigations
were complemented with measurements of denitrification rates in sea ice from different parts of the Arctic (69°N–85°N). Potential
for bacterial denitrification activity (5–194 μmol N m−2 day−1) and anammox activity (3–5 μmol N m−2 day−1) in melt water from both first-year and multi-year sea ice was found. These values correspond to 27 and 7%, respectively,
of the benthic denitrification and anammox activities in Arctic sediments. Although we report only potential denitrification
and anammox rates, we present several indications that active denitrification in sea ice may occur in Franklin Bay (and elsewhere):
(1) despite sea ice-algal primary production in the lower sea ice layers, heterotrophic activity resulted in net oxygen consumption
in the sea ice of 1–3 μmol l−1 sea ice per day at in situ light conditions, suggesting that O2 depletion may occur prior to the spring bloom. (2) The ample organic carbon (DOC) and NO3
− present in sea ice may support an active denitrification population. (3) Measurements of O2 conditions in melted sea ice cores showed very low bulk concentrations, and in some cases anoxic conditions prevailed. (4)
Laboratory studies using planar optodes for measuring the high-resolution two-dimensional O2 distributions in sea ice confirmed the very dynamic and heterogeneous O2 distribution in sea ice, displaying a mosaic of microsites of high and low O2 concentrations. Brine enclosures and channels were strongly O2 depleted in actively melting sea ice, and anoxic conditions in parts of the brine system would favour anaerobic processes. 相似文献
20.
Extensive beds of benthic, non-calcareous macroalgae are associated with reef formations in oligotrophic coastal waters of
Northeastern Brazil. Large amounts of these algae constantly and naturally detach and decay. Part of them is deposited on
the beach, remains exposed during low tides, and decomposes. Field experiments on decomposition were carried out in a tidal
pool (temperatures fluctuating from 29 to 43°C salinity from 6 to 35 at Ponta do Seixas (Paraiba, Brazil), and laboratory
studies were made in aerobic and anaerobic conditions. High values of NO
3
−
(up to 148.92 μg at 1−1), NO
2
−
(up to 3.14 μg at 1−1) and PO
3
4−
(up to 22.95 μg at 1−1) were released during algal degradation. Nitrogen values were higher in the tidal pool than in aerobic and anaerobic experiments,
as opposed to phosphorus where the opposite phenomenon occurred. The diatom Phaeodactylum tricornutum inoculated in seawater enriched with decomposition products of algae showed intense growth, sometimes similar to that in
complete algal culture medium. Inhibition and death of this diatom was observed in some other experiments. The importance
of drift seaweed as a source of nutrients for the local ecosystem is stressed. 相似文献