Temporal evolution of primary production in the central Barents Sea (original) (raw)
Related papers
1997
The coastal and archipelago waters of the northern Baltic Sea are influenced by increasing eutrophication (significantly increasing temporal trends in nutrient availability). Increased nutrient levels and pelagic primary production have led to decreased transparency in the water body, increased plankton biomass, and increased amounts of filamentous algae. Large-scale and long-term (15-30 years) comparisons have shown that zoobenthic communities have changed significantly (altered species diversity, increased total abundance and increased biomass). The stress in the ecosystem is also illustrated at the population level (Macoma balrhica). An increasing trend is shown for a near-shore fish community, where the increase in biomass has been linear over the past twenty years. Significant predictability of the regression has been shown for 1989-1994. Some areas show signs of community recovery, or changes attributable to natural variation, whereas other nearby areas may display opposite trends. The paper illustrates: (a) overall long-term changes (abiotic: nutrients and turbidity; and biotic: primary production, zoobenthos and fish); (b) site-specific long-term dynamics (infaunal and fish communities); and (c) cases of alternating long-term recovery and deterioration (water quality, zoobenthos).
FOOD WEBS AND PRIMARY PRODUCTION IN THE BARENTS SEA (Twelfth Symposium on Polar Biology)
This summary paper describes the food webs in the Barents Sea and deals with the seasonal changes in the phytoplankton stock and productivity. The pelagic food web is, as elsewhere, based mainly on unicellular algae (phytoplankton) as the primary producers. Temperatures of -1.8 to 5OC set an upper limit of about 0.6-0.8 d-I for the growth rate of diatoms in the Barents Sea. Phytoplankton biomass may reach as high as 10-1 5 mg m-3 in terms of Chlorophyll a or 300-600 mg m-3 in terms of carbon at the peak of the spring bloom. During most of the productive season, Chl a concentrations are 0.2-1 .O mg m-3 in the upper layers and 5-20mg m-3 at and near the pycnocline. Typical daily rates for primary production are 10-60mgC m-3; during the peak of the spring bloom up to 300-600 mgC m-3.
Trophic Status of the South-Eastern Baltic Sea: A Comparison of Coastal and Open Areas
Estuarine Coastal and Shelf Science, 2001
Primary production, nutrient concentrations, phytoplankton biomass (incl. chlorophyll a) and water transparency (Secchi depth), are important indicators of eutrophication. Earlier basin-wide primary production estimates for the Baltic Sea, a shallow shelf sea, were based mainly on open-sea data, neglecting the fundamentally different conditions in the large river plumes, which might have substantially higher production. Mean values of the period 1993-1997 of nutrient concentrations (phosphate, nitrate, ammonium and silicate), phytoplankton biomass, chlorophyll a (chl a) concentration, turbidity and primary production were calculated in the plumes of the rivers Oder, Vistula and Daugava and Klaipeda Strait as well as the open waters of the Arkona Sea, Bornholm Sea, eastern Gotland Sea and the Gulf of Riga. In the plumes, these values, except for primary production, were significantly higher than in the open waters. N:P ratios in the plumes were >16 (with some exceptions in summer and autumn), indicating potential P-limitation of phytoplankton growth, whereas they were <16 in the open Baltic Proper, indicating potential N-limitation. On the basis of in situphytoplankton primary production, phytoplankton biomass and nutrient concentrations, the large river plumes and the Gulf of Riga could be characterized as eutrophic and the outer parts of the coastal waters and the open sea as mesotrophic. Using salinity to define the border of the plumes, their mean extension was calculated by means of a circulation model. Taking into account the contribution of coastal waters, the primary production in the Baltic Proper and the Gulf of Riga was 42·6 and 4·3 10 6 t C yr 1 , respectively. Hence, an annual phytoplankton primary production in the whole Baltic Sea was estimated at 62 10 6 t C yr 1 . The separate consideration of the plumes had only a minor effect on the estimation of total primary production in comparison with an estimate based on open sea data only. There is evidence for a doubling of primary production in the last two decades. Moreover, a replacement of diatoms by dinoflagellates during the spring bloom was noticed in the open sea but not in the coastal waters. A scheme for trophic classification of the Baltic Sea, based on phytoplankton primary production and biomass, chl a and nutrient concentrations, is proposed.
Productivity in the Barents Sea - Response to Recent Climate Variability
The temporal and spatial dynamics of primary and secondary biomass/production in the Barents Sea since the late 1990s are examined using remote sensing data, observations and a coupled physical-biological model. Field observations of mesozooplankton biomass, and chlorophyll a data from transects (different seasons) and large-scale surveys (autumn) were used for validation of the remote sensing products and modeling results. The validation showed that satellite data are well suited to study temporal and spatial dynamics of chlorophyll a in the Barents Sea and that the model is an essential tool for secondary production estimates. Temperature, open water area, chlorophyll a, and zooplankton biomass show large interannual variations in the Barents Sea. The climatic variability is strongest in the northern and eastern parts. The moderate increase in net primary production evident in this study is likely an ecosystem response to changes in climate during the same period. Increased open water area and duration of open water season, which are related to elevated temperatures, appear to be the key drivers of the changes in annual net primary production that has occurred in the northern and eastern areas of this ecosystem. The temporal and spatial variability in zooplankton biomass appears to be controlled largely by predation pressure. In the southeastern Barents Sea, statistically significant linkages were observed between chlorophyll a and zooplankton biomass, as well as between net primary production and fish biomass, indicating bottom-up trophic interactions in this region.
Marine Biology, 1982
The distribution of phytoplankton primary production into four size fractions (> 10/zm, 10-3 #m, 3-0.2/~m and <0.2~m), the utilization of algal exudates by bacteria and the bacterial production were studied in a eutrophication gradient in the northern Baltic proper. The polluted area exhibits substantially increased nutrient, especially nitrogen, levels while only minor differences occur in salinity and temperature regimes. Total primary production was 160 g C-m-2"yr -1 at the control station and about 275 g C-m ~ 9 yr -1 at the eutrophicated stations. The estimated total exudate release was 16% of the totally fixed ~4CO2 in the control area and 12% in the eutrophicated area (including the estimated bacterial uptake of exudates). The difference in ~4CO2 uptake rates between incubation of previously filtered water (< 3, < 2, <l/~m) and unfiltered water was used to estimate bacterial uptake of phytoplankton exudates which were found to contribute about half of the estimated bacterial carbon requirement in both areas. Bacterial production was estimated by the frequency of dividing cells (FDC) method as being 38 g C 9 m -2 -yr -1 at the control station and 50 g C 9 m -2 9 yr -~ at the eutrophicated stations. To estimate the mean in situ bacterial cell volume a correlation between FDC and cell volume was used. The increased annual primary production in the eutrophicated area was due mainly to higher production during spring and autumn, largely by phytoplankton cells (mainly diatoms) retained by a 10/zm filter. Primary production during summer was similar in the two areas, as was the distribution on different size fractions. This could possibly explain the similar bacterial production in the trophic layers at all stations since the bulk of bacterial production occurs during summer. It was demonstrated that selective filtration does not quantitatively separate photoautotrophs and bacteria. A substantial fraction of the primary production occurs in the size fraction <3~tm. The primary production encountered in the 3-0.2k tin fraction was due to abundant picoplankton (0.5 to 8.107 ind'l-1), easily passing a 3/~m filter. The picoplankton was estimated to constitute up to 25% of the total phytoplankton biomass in the control area and up to 10% in the eutrophicated area.
Journal of Marine Systems, 2002
The project ''Climatic variability and vertical carbon flux in the marginal ice zone in the central Barents Sea'' was initiated to fill some of the gaps in our knowledge on the biological processes related to the dynamic hydrography in the Barents Sea. A previously modelled transect from the Atlantic waters, crossing the Polar Front into the Arctic waters and the MIZ in the central Barents Sea, was investigated to cover the zonal structure and different water masses. The present paper describes the hydrography, nutrients and Chl a distribution in March, May 1998 and July 1999 along this transect. Based on the nutrient consumption, the new production is estimated and discussed as related to topography, water masses and climate change. Atlantic water dominated in south with a Polar Front shaped by the bank topography, and water with more Arctic characteristics in north. A high, uniform nutrient regime in March was depleted giving a spring bloom in May with Chl a accumulation < 100 m in the Atlantic dominated region. The phytoplankton biomass was concentrated in the upper 30 m in the strongly stratified MIZ. The new production estimates for the period ranged 30 -80 g C m À 2 (0.5 -1.4 g C m À 2 day À 1 ). New production rates were closely related to the mixing depth with highest rates in the deeper mixed Atlantic region and trenches where the Polar Front was located. Non-Si demanding species were more important for new production in the deeper mixed regions. Seasonal changes from May to July was most likely masked by interannual variations as the July cruise took place the following year, characterised as a warmer year than 1998 in the Barents Sea due to increased Atlantic inflow in 1999 A locally produced cold but saline water mass observed on Sentralbanken in March and May resulting from the freezing process in the waters above the bank was replaced by warmer waters in July and the strongly stratified MIZ was pushed further north. Interannually variable hydrographic regimes in different regions influence the new production and the biological community in the Barents Sea. D Seasonal and interannual variability 0924-7963/02/$ -see front matter D 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 4 -7 9 6 3 ( 0 2 ) 0 0 1 6 7 -7
Marine Ecology Progress …, 1997
In t h~s study we estimated the amount and fate of phytoplankton primary product~on in the coastal zone of the Gulf of Gdansk, Poland, an area exposed to nutnent enrichment from the Vistuld R~v e r and nearby inunlcipal agglomeration The ~n v e s t i g a t~o n s were carned out at 2 sites d u r~n g 5 months in 1993 (February, April, May, August and October). A prolonged bloom pei-iod occurred in the coastal zone, as compared to the open Gulf and the open sea waters. From Aprll until October most values of gross primary production in the near-surface layer were in the range 100 to 500 m g C m-'' d 1 Phytoplankton net exudate release constituted on average 5 % of the gross prlmai-y production, total exudate release was estimated to be about 2 times h~gher. Bacterial production in the growth season was relatively low (the mean value l y~n g between 5 and 9 % of gloss primary production), nevertheless, the microbial community (bactena and protozoans) u t~l~z e d a large proportion of primary production (from about 50% in April and May to 16'%, in October). Usually direct protozoan grazing on phytoplankton exceeded bacterial uptake of the phytoplankton exudates. In winter, summer and autumn communlty respiration exceeded depth-averaged primary production, ~n d~c a t i n g that external energy sources (s e d~m e n t resuspension, allochthonous organic matter) play a substantial role in communlty metabol~sm.