60 research outputs found
Phytoplankton photosynthetic responses in a highly dynamic frontal area (Northern Adriatic Sea).
No full textMESOSCALE VARIABILITY OF PHOTOSYNTHETIC PARAMETERS IN A HIGHLY DYNAMIC FRONTAL AREA (NORTHERN ADRIATIC SEA).
No full textImplications of prolonged ice coverage in the Ross Ssea, (Antarctica) on phytoplankton assemblages
No full text
Structure and photosynthetic properties of phytoplankton assemblages in a highly dynamic system, the Northern Adriatic Sea
No full textThe photosynthetic properties of phytoplankton populations as related to physicalechemical variations on small temporal and spatial scales and to phytoplankton size structure and pigment spectra were investigated in the Northern Adriatic Sea off the Po River delta in late winter 1997.
Large diatoms (fucoxanthin) dominated the phytoplankton in the coastal area whereas small phytoflagellates (mainly 19-hexanoyloxyfucoxanthin, chlorophyll b, 19-butanoyloxyfucoxanthin) occurred outside the front. The front was defined by the steep gradient in density in the surface layer separating low-salinity coastal waters from the offshore waters.
Physical features of the area strongly influenced phytoplankton biomass distributions, composition and size structure. After high volumes of Po River discharge several gyres and meanders occurred in the area off the river delta in February. Decreasing river discharge and the subsequent
disappearance of the gyres and the spreading dilution of the river plume was observed in March. The dynamic circulation of February resulted in high photosynthetic capacity of the abundant phytoplankton population (>3.40 mg m-3). In March, the slow circulation and an upper lowsalinity
water layer, segregated from the deeper layers, resulted in lack of renewal of this water mass. The huge phytoplankton biomass, up to 15.77 mg chl a m-3, became nutrient depleted and showed low photosynthetic capacity. In February, an exceptionally high PmaxB, 20.11 mg C (mg chl a)-1 h-1 was recorded in the Po River plume area and average PmaxB was three-fold in February as compared to the March recordings, 10.50 mg C (mg chl a)-1 h-1 and 3.22 mg C (mg chl a)-1 h-1, respectively.
The extreme variability and values of phytoplankton biomass in the innermost plume area was not always reflected in primary production.
Modeling of circulation patterns and water mass resilience in the area will help to predict phytoplankton response and biomass distributions. In the frontal area, despite a considerable variability in environmental conditions, our findings have shown that the phytoplankton assemblages will
compensate for nutrient depression and hydrographic constraints, by means of size and taxonomic composition and, as a result, the variability in the photosynthetic capacity was much less pronounced than that observed for other parameters
The role of platelet ice microalgae in seeding phytoplankton blooms in Terra Nova Bay (Ross Sea, Antarctica): a mesocosm experiment.
No full textThe 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 lmol L-1 d-1 of TIN in the high light tank and 6.18 lmol 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 lg Chla L-1
Primary production processes in the Ross Sea (Antarctica): limiting factors and system carrying capacity.
No full textPhotoacclimation in Antarctic bottom ice algae: an experimental approach
No full textThe aim of the study was to investigate the capacity of microalgae from the extremely low light habitat of bottom ice to acclimate to different light conditions.
During austral spring 1997 the bottom layer of land-fast ice
in Terra Nova Bay displayed high values of microalgal
biomass up to 2,400 lg Chla L-1 concentrated in a few
centimetres ice layer. The algal assemblage was dominated
by benthic pennate diatoms. Photoacclimation of the microalgae was addressed in terms of pigment spectra and
photosynthetic parameters. Immediate and long term
(minutes to days) changes in the photoprotective pigments
(DD-cycle) were analysed. Severe photodamage occurred
in microalgal assemblages exposed to high light. However,
part of the bottom ice algal community showed a notable
ability to acclimate to high irradiance levels. Changes in
photosynthetic parameters preceded the sudden abrupt
changes in pigment synthesis and the rapid increase in
biomass and growth rates
Structure and photosyntetic properties of phytoplankton assemblages in a highly dynamic system, the Northern Adriatic Sea
No full textThe photosynthetic properties of phytoplankton populations as related to physicalechemical variations on small temporal and spatial scales
and to phytoplankton size structure and pigment spectra were investigated in the Northern Adriatic Sea off the Po River delta in late winter 1997.
Large diatoms (fucoxanthin) dominated the phytoplankton in the coastal area whereas small phytoflagellates (mainly 190-hexanoyloxyfucoxanthin,
chlorophyll b, 190-butanoyloxyfucoxanthin) occurred outside the front. The front was defined by the steep gradient in density in the surface
layer separating low-salinity coastal waters from the offshore waters.
Physical features of the area strongly influenced phytoplankton biomass distributions, composition and size structure. After high volumes of
Po River discharge several gyres and meanders occurred in the area off the river delta in February. Decreasing river discharge and the subsequent
disappearance of the gyres and the spreading dilution of the river plume was observed in March. The dynamic circulation of February resulted in
high photosynthetic capacity of the abundant phytoplankton population (>3.40 mg m3). In March, the slow circulation and an upper lowsalinity
water layer, segregated from the deeper layers, resulted in lack of renewal of this water mass. The huge phytoplankton biomass, up
to 15.77 mg chl a m3, became nutrient depleted and showed low photosynthetic capacity. In February, an exceptionally high Pmax
B ,
20.11 mg C (mg chl a)1 h1 was recorded in the Po River plume area and average Pmax
B was three-fold in February as compared to the March
recordings, 10.50 mg C (mg chl a)1 h1 and 3.22 mg C (mg chl a)1 h1, respectively.
The extreme variability and values of phytoplankton biomass in the innermost plume area was not always reflected in primary production.
Modeling of circulation patterns and water mass resilience in the area will help to predict phytoplankton response and biomass distributions. In
the frontal area, despite a considerable variability in environmental conditions, our findings have shown that the phytoplankton assemblages will
compensate for nutrient depression and hydrographic constraints, by means of size and taxonomic composition and, as a result, the variability in
the photosynthetic capacity was much less pronounced than that observed for other parameters
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