| 1. |
- Andersson, Agneta, et al.
(författare)
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The pelagic food web
- 2017
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Ingår i: Biological oceanography of the Baltic sea. - Dordrecht : Springer Netherlands. - 9789400706682 - 9789400706675 ; , s. 281-332
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Bokkapitel (refereegranskat)abstract
- Environmental drivers and food web structure in the pelagic zone vary from south to north in the Baltic Sea. While nitrogen is generally the limiting nutrient for primary production in the Baltic Sea, phosphorus is the limiting nutrient in the Bothnian Bay. In the Gulf of Bothnia the food web is to a large extent driven by terrestrial allochthonous material, while autochthonous production dominates in the other parts of the Baltic Sea. Changes in bacterioplankton, protist and zooplankton community composition from south to north are mainly driven by salinity. Bacteria are crucial constituents of the pelagic food web (microbial loop) and in oxygen-poor and anoxic bottom waters where they mediate element transformations. Diatoms and dinoflagellates are the major primary producers in the pelagic zone. Summer blooms of diazotrophic (nitrogen-fixing) filamentous cyanobacteria are typical of the Baltic Sea, especially in the Baltic Sea proper and the Gulf of Finland. The mesozooplankton (mainly copepods and cladocerans) channel energy from primary producers and the microbial food web to fish and finally to the top predators in the pelagic system (waterbirds and mammals). Herring and sprat populations are affected by the foraging intensity of their main predator (cod), and therefore the environmental conditions that affect cod may also influence mesozooplankton due to food web effects "cascading down the food web". Anthropogenic pressures, such as overexploitation of fish stocks, eutrophication, climate change, introduction of non-indigenous species and contamination of top predators by hazardous substances, cause changes in the pelagic food web that may have consequences for the balance and stability of the whole ecosystem.
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| 2. |
- Humborg, Christoph, et al.
(författare)
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Silicon and the Baltic Sea Long-term Si decrease in the Baltic Sea - A conceivable ecological risk?
- 2008
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Ingår i: Journal of Marine Systems. - : Elsevier. - 0924-7963 .- 1879-1573. ; 73:3-4, s. 221-222
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Since the pioneering work of Schelske and Stoermer (1971) and Schelske et al., 1983 C.L. Schelske, E.F. Stoermer, D.J. Conley, J.A. Robbins and R.M. Glover, Early eutrophication in the Lower Great-Lakes — new evidence from biogenic silica in sediments, Science 222 (1983), pp. 320–322. View Record in Scopus | Cited By in Scopus (56)Schelske et al. (1983) it has been known that eutrophication of aquatic systems leads to depletion in dissolved silicate (DSi). Early studies on the Nile River have shown that the construction of dams leads to DSi decrease downstream due to the formation of additional deposition sites of biogenic silica (BSi) that was thought to consist mainly of diatoms. In the Baltic Sea there was a perception in the scientific community that DSi concentrations were high and therefore, that DSi concentrations were not limiting for diatom growth. Long-term trend analyses on DSi concentrations in the Baltic have shown decreasing trends in the 1970s and 1980s, whereas similar analysis for the 1990s concluded that DSi concentrations were no longer decreasing, but rather levelling off. Consequently, observations of reduced abundance of diatoms in the early 1990s were attributed to mild winters rather than low DSi concentrations, i.e., a low turbulence regime in the water column favouring non-siliceous algae. However, decadal nutrient trends in the Baltic Sea are significantly influenced by the large and varying internal Si pools in the sediments and deep water masses similar to that described for P dynamics in the Baltic Sea. No one seriously addressed the longer trends in DSi concentrations over the last century, whereas many studies estimated these changes for N and P.The EU funded research project SIBER (Silicate and Baltic Sea Ecosystem Response; EVK3-CT-2002-00069) began in 2002 with the objectives of understanding the major changes in Si dynamics in the Baltic Sea during the last century. The SIBER project addressed various aspects of the biogeochemical Si cycle in the Baltic Sea including constraining Si budgets for the Baltic Sea and its catchment, experiments describing the growth characteristics of Baltic diatoms related to the long-term trends in monitoring data of Baltic Sea diatoms.Si budgets are addressed by several papers in this special issue. Humborg et al. and Sferratore et al. describe riverine Si fluxes. Pastuszak et al. address estuarine Si fluxes. Redfield ratios including DSi and their development in the Baltic Sea are described by Danielsson et al.Possible ecosystem effects of changes in Redfield nutrient ratios are analysed in the paper by Olli et al. who examine phytoplankton responses in the Gulf of Riga and by Wasmund et al. who investigate long-term trends in phytoplankton species in the Kiel Bight. Spilling and Markager describe growth characteristics of Baltic Sea diatoms. Finally, in their paper Conley et al. present a long-term Si budget for the entire Baltic Sea for the first time.The Baltic Sea biogeochemical Si cycle has been fundamentally changed within the last century not only as a consequence of river regulation and lake eutrophication, but also through increases in the sediment accumulation of BSi (Conley et al.). Sediment accumulation of BSi has increased by a factor on 1.9 due to increased diatom growth from marine eutrophication. Results from the SIBER project indicate that DSi concentration were ca. 36 µM a century ago in the Baltic proper compared to ca. 13 µM observed today (Conley et al.). In fact, DSi concentrations have changed much more dramatically compared to N and P regarding the total changes in the available nutrient stocks. Similar changes have occurred in other large water bodies with respect to size and volume, i.e. the North American Great Lakes with long residence times where DSi decreased from 80–100 µM to ca. 25 µM. Surprisingly, such a major change in nutrient inventories has not been reported earlier in this well investigated coastal system. We are only starting to understand the possible ecological consequences, such as the occurrence of different diatom species that are less silicified and its implication for the sedimentation fluxes and carbon flux to benthic communities. The SIBER project has shown that a dramatic change in DSi concentrations is possible within a very short time period, although the situation appears stable today, perhaps since the drivers for this change, i.e. eutrophication and river regulation, have not changed within the last 30 years. However, even a slight increase in N and P loads and/or further damming of rivers may drive the Baltic Sea into Si-limitation.
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| 3. |
- Klais, Riina, et al.
(författare)
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Spring phytoplankton communities shaped by interannual weather variability and dispersal limitation : Mechanisms of climate change effects on key coastal primary producers
- 2013
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 58:2, s. 753-762
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Tidskriftsartikel (refereegranskat)abstract
- Spring bloom composition in the Baltic Sea, a partially ice-covered brackish coastal waterbody, is shaped by winter-spring weather conditions affecting the relative dominance of diatoms and a heterogeneous assemblage of cold-water dinoflagellates, dominated by the chain-forming Peridiniella catenata and a complex of at least three medium-sized, single-celled species: Biecheleria baltica, Gymnodinium corollarium, and Scrippsiella hangoei. During the last decades, the bloom community has dramatically changed in several basins. We analyze here a 30 yr time series of quantitative phytoplankton data, as predicted by hindcast modeled ice thickness and storminess for three distinct Baltic Sea localities, to verify climate-driven mechanisms affecting the spring bloom composition. Thick (> 30 cm) and long-lasting ice cover favored diatom-dominated spring blooms, and mild winters, with storms and thin ice cover (10 to 20 cm), supported blooms of the B. baltica complex. Dispersal limitation plays an important role in the spatial extent of blooms of the B. baltica complex, caused by intricate interplay of local hydrodynamics and the dinoflagellate life cycle. Proportion peaks of key phytoplankton groups have shifted about 10 d earlier in the northwestern Baltic Sea (P. catenata and diatoms) and in the Gulf of Riga (P. catenata). The significant weather effects imply future shifts in spring bloom composition and consequent biogeochemical cycles, driven by the predicted changes in winter storminess and decrease in ice cover extent and duration in climate change models.
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| 4. |
- Kulmala, Markku, et al.
(författare)
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Opinion : The strength of long-term comprehensive observations to meet multiple grand challenges in different environments and in the atmosphere
- 2023
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Ingår i: Atmospheric Chemistry And Physics. - 1680-7316 .- 1680-7324. ; 23:23, s. 14949-14971
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Tidskriftsartikel (refereegranskat)abstract
- To be able to meet global grand challenges (climate change; biodiversity loss; environmental pollution; scarcity of water, food and energy supplies; acidification; deforestation; chemicalization; pandemics), which all are closely interlinked with each other, we need comprehensive open data with proper metadata, along with open science. The large data sets from ground-based in situ observations, ground and satellite remote sensing, and multiscale modeling need to be utilized seamlessly. In this opinion paper, we demonstrate the power of the SMEAR (Station for Measuring Earth surface-Atmosphere Relations) concept via several examples, such as detection of new particle formation and the particles' subsequent growth, quantifying atmosphere-ecosystem feedback loops, and combining comprehensive observations with emergency science and services, as well as studying the effect of COVID-19 restrictions on different air quality and climate variables. The future needs and the potential of comprehensive observations of the environment are summarized.
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| 5. |
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| 6. |
- Olli, Kalle, et al.
(författare)
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Diatom stratigraphy and long-term dissolved silica concentrations in the Baltic Sea
- 2008
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Ingår i: JOURNAL OF MARINE SYSTEMS. - : Elsevier BV. - 0924-7963. ; 73:3-4, s. 284-299
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Tidskriftsartikel (refereegranskat)abstract
- In many parts of the world coastal waters with anthropogenic eutrophication have experienced a gradual depletion of dissolved silica (DSi) stocks. This could put pressure on spring bloom diatom populations, e.g. by limiting the intensity of blooms or by,causing shifts in species composition. In addition, eutrophication driven enhanced diatom growth is responsible for the redistribution of DSi from the water phase to the sediments, and changes in the growth conditions may be reflected in the sediment diatom stratigraphy. To test for changes in diatom communities we have analyzed four sediment cores from the Baltic Sea covering approximately the last 100 years. The sediment cores originate from the western Gulf of Finland, the Kattegat, the Baltic Proper and the Gulf of Riga. Three out of the four cores reveal only minor changes in composition of diatom assemblages, while the Gulf of Riga core contains major changes, occurring after the second World War. This area is set apart from the other Baltic Sea basins by a high frequency of low after spring bloom DSi concentrations (<2 mu mol L-1) during a relatively well defined time period from 1991-1998. In 1991 to 1993 a rapid decline of DSi spring concentrations and winter stocks (down to 5 mu mol L-1) in the Gulf was preceded by exceptionally intense diatom spring blooms dominated by the heavily silicified species Thalassiosira baltica (1991-1992; up to 5.5 mg ww L-1). T baltica has been the principal spring bloom diatom in the Gulf of Riga since records began in 1975. DSi consumption and biomass yield experiments with cultured T baltica suggest that intense blooms can potentially exhaust the DSi stock of the water column and exceed the annual Si dissolution in the Gulf of Riga. The phytoplankton time series reveals another exceptional T baltica bloom period in 1981-1983 (up to 8 mg L-1), which, however, took place before the regular DSi measurements. These periods may be reflected in the conspicuous accumulation of T baltica frustules in the sediment core corresponding to ca. 1975-1995.
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| 7. |
- Sopanen, Sanna, et al.
(författare)
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Transfer of nodularin to copepod Eurytemora affinis through the microbial food web
- 2009
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Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 55:2, s. 115-130
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Tidskriftsartikel (refereegranskat)abstract
- Nodularia spumigena Mertens ex Bornet & Flahault 1886 (Cyanophyceae) frequently forms harmful blooms in the Baltic Sea, and the toxin nodularin has been found in calanoid copepods during the blooms. Although nodularin has been found at higher trophic levels of the food web, no available information exists about the role of the microbial loop in the transfer of nodularin. We followed the transfer of nodularin to the copepod Eurytemora affinis during conditions that resembled initial 'pre-bloom' (Expt 1) and late stationary (Expt 2) phases of a N. spumigena bloom. The experiments were carried out using natural plankton communities spiked with cultured N. spumigena and grown in laboratory mesocosms, and E. affinis, which were isolated from the Baltic Sea and had no prior contact with nodularin. The plankton community was divided into 6 size fractions as follows: <150, <45, <20, <10, <3 and <0.2 pm, in which E. affinis was incubated for 24 h. Ingestion and clearance rates, food selection and faecal pellet production were based on microscopical analyses. Nodularin was measured with HPLC-MS with electrospray ionization in the copepods, as well as in dissolved and particulate fractions before and after incubation. We found that nodularin accumulated in copepods in all the plankton size fractions. The copepods contained nodularin concentrations of 14.3 +/- 11.6 (mean +/- SD) and 6.6 +/- 0.7 pg ind.(-1) after incubation in the < 150 mu m fraction in Expt 1 and Expt 2, respectively, while the range in the smaller size fractions was from 1.3 +/- 2.8 to 5.7 +/- 1.3 pg ind.-1. Nodularin was transferred to the copepods through 3 pathways: (1) by grazing on filaments of small N. spumigena, (2) directly from the dissolved pool, and (3) through the microbial food web by copepods grazing on ciliates, dinoflagellates and heterotrophic nanoflagellates. The relative importance of direct grazing on small N. spumigena filaments varied from moderate to insignificant. The microbial loop was important in nodularin transfer to higher trophic levels. Our results suggest that the importance of the microbial loop in harmful algal bloom (HAB) toxin transfer may be underestimated both in marine and freshwater systems.
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| 8. |
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| 9. |
- Vehmaa, Anu, et al.
(författare)
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Copepod reproductive success in spring-bloom communities with modified diatom and dinoflagellate dominance
- 2012
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 69:3, s. 351-357
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Tidskriftsartikel (refereegranskat)abstract
- Dinoflagellates have increased and diatoms decreased in the Baltic Sea in recent decades, possibly because of changes in the climate and altered patterns of stratification. The hypothesis that grazing copepods would benefit from the change in species composition was tested experimentally by studying the reproductive output of the crustacean copepod Eurytemora affinis in five Baltic Sea phytoplankton spring communities dominated by different dinoflagellates (Biecheleria baltica, Gymnodinium corollarium) and diatoms (Chaetoceros cf. wighamii, Skeletonema marinoi, and Thalassiosira baltica). After a 5-d acclimation and a 4-d incubation, egg production, egg hatching success, and the RNA: DNA ratio of E. affinis were measured. Egg production was highest on a G. corollarium-dominated diet and lowest on a S. marinoi-dominated diet and on a B. baltica-dominated natural spring bloom, but there were no differences in hatching success. The results demonstrate strong species-specific effects unconstrained by the dominating group. Hence, the hypothesis of specific effects derived from a diatom or dinoflagellate diet is too simplistic, and there is a need to explore phytoplankton taxa at a species level to reveal the reasons for copepod reproductive success.
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