共查询到20条相似文献,搜索用时 46 毫秒
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.
Olga Mangoni Maria Saggiomo Monica Modigh Giulio Catalano Adriana Zingone Vincenzo Saggiomo 《Polar Biology》2009,32(3):311-323
The aim of this study was to assess the role of platelet ice microalgal communities in seeding pelagic blooms. Nutrient dynamics,
microalgal biomass, photosynthetic parameters, cell densities and species succession were studied in two mesocosm experiments,
designed to simulate the transition of microalgal communities from platelet ice habitat to pelagic conditions. The microalgal
assemblages were dominated by diatoms, 70% of which were benthic species such as Amphiprora kufferathii, Nitzschia stellata, and Berkeleya adeliensis. Photoacclimation of benthic species was inadequate also at relatively low irradiances. Exceptional growth capacity at different
light levels was observed for pelagic species such as Fragilariopsis cylindrus and Chaetoceros spp. which may be important in seeding blooms at ice breakup. Fragilariopsis cylindrus showed high growth rates both at 65 and 10% of incident light and in nutrient replete as well as in nutrient depleted conditions.
Five days after inoculation, phytoplankton biomass increased and nutrient concentrations decreased in both light conditions.
Nutrient uptake rates were up to 9.10 μmol L−1 d−1 of TIN in the high light tank and 6.18 μmol L−1 d−1 in the low light tank and nutrient depletion in the high light tank occurred 3 days prior to depletion in the low light tank.
At nutrient depletion, biomass concentrations were similar in both tanks, 30 and 34 μg Chla L−1.
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
3.
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
4.
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
5.
Katherina Petrou Ross Hill Martina A. Doblin Andrew McMinn Robert Johnson Simon W. Wright Peter J. Ralph 《Journal of phycology》2011,47(1):77-86
All photosynthetic organisms endeavor to balance energy supply with demand. For sea‐ice diatoms, as with all marine photoautotrophs, light is the most important factor for determining growth and carbon‐fixation rates. Light varies from extremely low to often relatively high irradiances within the sea‐ice environment, meaning that sea‐ice algae require moderate physiological plasticity that is necessary for rapid light acclimation and photoprotection. This study investigated photoprotective mechanisms employed by bottom Antarctic sea‐ice algae in response to relatively high irradiances to understand how they acclimate to the environmental conditions presented during early spring, as the light climate begins to intensify and snow and sea‐ice thinning commences. The sea‐ice microalgae displayed high photosynthetic plasticity to increased irradiance, with a rapid decline in photochemical efficiency that was completely reversible when placed under low light. Similarly, the photoprotective xanthophyll pigment diatoxanthin (Dt) was immediately activated but reversed during recovery under low light. The xanthophyll inhibitor dithiothreitol (DTT) and state transition inhibitor sodium fluoride (NaF) were used in under‐ice in situ incubations and revealed that nonphotochemical quenching (NPQ) via xanthophyll‐cycle activation was the preferred method for light acclimation and photoprotection by bottom sea‐ice algae. This study showed that bottom sea‐ice algae from the east Antarctic possess a high level of plasticity in their light‐acclimation capabilities and identified the xanthophyll cycle as a critical mechanism in photoprotection and the preferred means by which sea‐ice diatoms regulate energy flow to PSII. 相似文献
6.
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
7.
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
8.
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
9.
The aim of this paper is to contribute to the knowledge on the feeding habits of larvae and juvenile Pleuragramma antarcticum in the western Ross Sea. In summer, the diet of P. antarcticum postlarvae (8–17 mm) was dominated by calanoid eggs (35.5%), Limacina (32.1%) and tintinnids (17.6%), while the principal food of juveniles consisted mainly of copepods (98.2%), with Oncaea curvata being the most abundant (85.1%) and the most frequently consumed prey. The food composition of P. antarcticum postlarvae (24–29 mm), collected in spring, suggest that they fed actively under the sea ice. Stephos longipes, Harpacticus furcifer and Paralabidocera antarctica sea ice copepods represent, in all their different developmental stages, the most abundant biomass food in Terra Nova Bay
in this period. Our results therefore suggest that the diet of younger Pleuragramma specimens shifted in prey composition from the first summer to the following spring. This study draws attention to the key
role of the copepod, P. antarctica, in the food web of Terra Nova Bay.
This article belongs to a special topic: Five articles coordinated by L. Guglielmo and V. Saggiomo appear in this issue of
Polar Biology and are a result of a workshop on Sea-ice communities in Terra Nova Bay (Ross Sea) held in August 2007 in Capo
Calavà, Messina, Italy. 相似文献
10.
The responses of sea ice microalgae to variation in ambient irradiance (0 to 150 μE · m?2· s?1), temperature (–6° to + 6° C), and salinity (0 to 100 ppt) were tested to determine whether these variables act independently or in concert to influence rates of microalgal photosynthesis. The photosynthetic efficiency and maximum photosynthetic rate for sea ice microalgae increased as a function of incubation temperature between -6° and + 6° C. Furthermore, photosynthetic efficiency, maximum photosynthetic rate, and quantum yield were greatest at salinities between SO and 50 ppt. In contrast, the mean specific absorption coefficients were lowest near seawater salinities, and the saturating irradiance, Is, appeared to be inversely proportional to salinity. Results also suggest that the effects of salinity on the growth of sea ice microalgae are independent of those elicited by temperature or light, and that the functional relationship between salinity and light or temperature is multiplicative. This information is essential to the proper formulation of algorithms used to describe algal growth in environments where light, temperature, and salinity are changing simultaneously, such as within sea ice or within the water column at the marginal ice edge zone. 相似文献
11.
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
12.
Mariachiara Chiantore Riccardo Cattaneo-Vietti Paul Arthur Berkman Marco Nigro Marino Vacchi Stefano Schiaparelli Giancarlo Albertelli 《Polar Biology》2001,24(2):139-143
Along the Victoria Land Coast, the population structure of the Antarctic scallop (Adamussium colbecki) was studied in McMurdo Sound (New Harbor), Terra Nova Bay, and Wood Bay, on a latitudinal span of 3 degrees. At a large
spatial scale, most relevant differences between the scallop populations are linked to their depth distributions. The McMurdo
and Wood Bay populations show a shallower bathymetric distribution with maximum abundance between 5 and 15 m depth. In contrast,
inside Terra Nova Bay, at sites with similar near-shore bathymetric profiles, the maximum biomass is found between 40 and
70 m. This difference can be related to the different ice-cover persistency characterising these two areas, being less at
Terra Nova Bay than in the other localities. Differences arise also in the reproductive period: at McMurdo, it seems to occur
early in the austral spring, while at Terra Nova Bay, mature females are observed at the beginning of February. Also at a
small scale, in sites only a few miles from each other, the population structures inside Terra Nova Bay and Wood Bay vary
in terms of abundance and size frequency distribution, suggesting various environmental and biological constraints. Among
environmental factors, bottom features (slope, sediment grain size, organic content) and water-column food supply during the
summer months may be considered. In addition, as Adamussium is preyed upon by starfishes and fishes, its abundance and population structure may be affected by predators and their abundance.
Accepted: 7 August 2000 相似文献
13.
The phytoplankton and sea ice algal communities at the end of winter in McMurdo Sound were dominated by Fragilariopsis sublineata, with Thalassiosira antarctica, Melosira adele, Pinnularia quadreata, Entomoneis kjellmannii and heterotrophic dinoflagellates also present. Sea ice algal biomass at the end of winter was very low, only 0.050 ± 0.019 mg chla m−2 in 2007 and 0.234 ± 0.036 mg chla m−2 in 2008, but this increased to 0.377 ± 0.078 mg chla m−2 by early October in 2007 and to 1.07 ± 0.192 by late September in 2008. Under ice phytoplankton biomass remained consistently
below 0.1 μg chla l−1 throughout the measuring period in both years. The photosynthetic parameters Fv/Fm, rETRmax and α document microalgal communities
that are mostly healthy and well adapted to their low light under ice environment. Our results also suggest that species such
as Fragilariopsis sublineata are well adapted to deal with low winter light levels but are unlikely to survive an increase in irradiance, whereas other
taxa, such as Thalassiosira antarctica, will do better in a higher light environment. 相似文献
14.
Antonio Pusceddu Riccardo Cattaneo-Vietti Giancarlo Albertelli Mauro Fabiano 《Polar Biology》1999,22(2):124-132
Water samples and particulate materials settling under the pack ice were collected in an ice-covered area near the Terra
Nova Bay Italian Station during late summer 1995, in order to study short-term changes in the biochemical composition of particulate
organic matter. At the end of the study period the phytoplankton biomass increase (up to >3.0 μg chlorophyll-a l−1) was probably related to the intrusion under the pack ice of chlorophylls-enriched surface waters coming from the near ice-free
area. Such increase was associated also with a notable increase in particulate organic matter concentrations, as well as in
particulate organic matter vertical fluxes (up to >100 mg C m−2 day−1). Proteins were the most abundant biochemical class of particulate organic matter (on average about 49%), followed by lipids
(29%) and carbohydrates (22%). By contrast, organic matter collected in the sediment trap was characterized by the dominance
of lipids (about 55% of the total biopolymeric carbon flux) over carbohydrates (28%) and proteins (17%). The hydrolizable
particulate biopolymeric carbon accounted for about 23% of total biopolymeric carbon. This value was about one-half of that
found in ice-free waters, suggesting that the suspended particulate organic material under the pack ice was less digestible
than in ice-free waters or was already partially digested. Despite this, and the decay of labile organic compounds in the
sediment trap during the deployment, material settling towards the sea bottom under the pack ice in Terra Nova Bay, owing
to its high lipid content, might represent an important high-quality food source for benthic consumers. Finally, assuming
as possible the intrusion under sea ice of primary organic matter-enriched waters, we hypothesize the occurrence of a “fertilization”
effect deriving from ice-melting areas towards under-ice waters, supplying the latter with an additional rate of primary organic
matter.
Accepted: 18 February 1999 相似文献
15.
S. Becquevort I. Dumont J.-L. Tison D. Lannuzel M.-L. Sauvée L. Chou V. Schoemann 《Polar Biology》2009,32(6):879-895
Pack ice, brines and seawaters were sampled in October 2003 in the East Antarctic sector to investigate the structure of the
microbial communities (algae, bacteria and protozoa) in relation to the associated physico-chemical conditions (ice structure,
temperature, salinity, inorganic nutrients, chlorophyll a and organic matter). Ice cover ranged between 0.3 and 0.8 m, composed of granular and columnar ice. The brine volume fractions
sharply increased above −4°C in the bottom ice, coinciding with an important increase of algal biomass (up to 3.9 mg C l−1), suggesting a control of the algae growth by the space availability at that period of time. Large accumulation of NH4
+ and PO4
3− was observed in the bottom ice. The high pool of organic matter, especially of transparent exopolymeric particles, likely
led to nutrients retention and limitation of the protozoa grazing pressure, inducing therefore an algal accumulation. In contrast,
the heterotrophs dominated in the underlying seawaters. 相似文献
16.
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
17.
Sea ice microalgae are released from their relatively stable light environment to the water column seasonally, and any subsequent growth in a vertically mixed water column may depend, in part, on their photoadaptation rates. In this study we followed the time course of photoadaptation in natural sea ice algal communities from bottom ice and surface ice by measuring their photophysiological response to an artificial shift in the ambient irradiance field. Microalgae from under-ice habitats, were incubated under full sunlight (LL-HL) and microalgae from surface ice habitats were incubated under artificial light to mimic under-ice irradiance (HL-LL). During 3- to 4-day time course studies, opposite shifts in chlorophyll: carbon, α, PBm, and Ik were observed, depending on the direction of the irradiance change. First-order rate constants (k) ranged from 0.0067 to 0.29 h?1 for photosynthetic parameters, although PBm did not always show a clear change over time. Rates of photoadaptation for ice algae are comparable to k values reported for temperate phytoplankton, suggesting that sea ice algae may be equally capable of adapting to the light conditions experienced in a vertically mixed water column. This study presents the first evidence that sea ice microalgae are physiologically capable of adapting to a planktonic life and thus could serve as a seed population for polar marine phytoplankton blooms. 相似文献
18.
Exposure to high temperatures affects the photosynthetic processes in marine benthic microalgae by limiting the transport
of electrons, thus reducing the ability of the cell to use light. This causes damage to the Photosystem II (PSII) and may
lead to photoinhibition. However, the PSII of benthic microalgal communities from Brown Bay, eastern Antarctica, were relatively
unaffected by significant changes in temperature. Benthic microalgae exposed to temperatures up to 8°C and an irradiance of
450 μmol photons m−2 s−1 did not experience any photosynthetic damage or irreversible photoinhibition. The effective quantum yield (∆F/F
m′) at 8°C (0.433 ± 0.042) was higher by comparison to cell incubated at −0.1°C (0.373 ± 0.015) with similar irradiances. Temperatures
down to −5°C at a similar irradiance showed a decrease in photosynthesis with decreasing temperature, but no severe photoinhibition
as the cells were able to dissipate excess energy via non-photochemical quenching and recover from damage. These responses
are consistent with those recorded in past studies on Antarctic benthic microalgae and suggest that short-term temperature
change (from −5 to 8°C) will not do irreversible damage to the PSII and will not affect the photosynthesis of the benthic
microalgae. 相似文献
19.
Ken G. Ryan Rebecca O. M. Cowie Elizabeth Liggins Daniel McNaughtan Andrew Martin Simon K. Davy 《Journal of phycology》2009,45(6):1290-1298
Although sea‐ice represents a harsh physicochemical environment with steep gradients in temperature, light, and salinity, diverse microbial communities are present within the ice matrix. We describe here the photosynthetic responses of sea‐ice microalgae to varying irradiances. Rapid light curves (RLCs) were generated using pulse amplitude fluorometry and used to derive photosynthetic yield (ΦPSII), photosynthetic efficiency (α), and the irradiance (Ek) at which relative electron transport rate (rETR) saturates. Surface brine algae from near the surface and bottom‐ice algae were exposed to a range of irradiances from 7 to 262 μmol photons · m?2 · s?1. In surface brine algae, ΦPSII and α remained constant at all irradiances, and rETRmax peaked at 151 μmol photons · m?2 · s?1, indicating these algae are well acclimated to the irradiances to which they are normally exposed. In contrast, ΦPSII, α, and rETRmax in bottom‐ice algae reduced when exposed to irradiances >26 μmol photons · m?2 · s?1, indicating a high degree of shade acclimation. In addition, the previous light history had no significant effect on the photosynthetic capacity of bottom‐ice algae whether cells were gradually exposed to target irradiances over a 12 h period or were exposed immediately (light shocked). These findings indicate that bottom‐ice algae are photoinhibited in a dose‐dependent manner, while surface brine algae tolerate higher irradiances. Our study shows that sea‐ice algae are able to adjust to changes in irradiance rapidly, and this ability to acclimate may facilitate survival and subsequent long‐term acclimation to the postmelt light regime of the Southern Ocean. 相似文献
20.
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