Long-term Changes and Controlling Factors of Phytoplankton Community in the Gulf of Riga (Baltic Sea)

Jurgensone, Iveta; Carstensen, Jacob; Ikauniece, Anda; Kalveka, Baiba

doi:10.1007/s12237-011-9402-x

Cited by 39 publications

(39 citation statements)

References 54 publications

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“…This attenuation of top-down control at lower trophic levels conforms to what was found in other field and experimental studies (25). Though a significant negative effect of copepods on phytoplankton was unveiled in our model (26), temperature and river Daugava runoff were also important drivers (Table 1, Fig. 2, and Fig.…”

Section: Resultssupporting

confidence: 91%

Predator transitory spillover induces trophic cascades in ecological sinks

Casini

Blenckner²,

Möllmann³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

102

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Understanding the effects of cross-system fluxes is fundamental in ecosystem ecology and biological conservation. Source-sink dynamics and spillover processes may link adjacent ecosystems by movement of organisms across system boundaries. However, effects of temporal variability in these cross-system fluxes on a whole marine ecosystem structure have not yet been presented. Here we show, using 35 y of multitrophic data series from the Baltic Sea, that transitory spillover of the top-predator cod from its main distribution area produces cascading effects in the whole food web of an adjacent and semi-isolated ecosystem. At varying population size, cod expand/contract their distribution range and invade/retreat from the neighboring Gulf of Riga, thereby affecting the local prey population of herring and, indirectly, zooplankton and phytoplankton via top-down control. The Gulf of Riga can be considered for cod a "true sink" habitat, where in the absence of immigration from the source areas of the central Baltic Sea the cod population goes extinct due to the absence of suitable spawning grounds. Our results add a metaecosystem perspective to the ongoing intense scientific debate on the key role of top predators in structuring natural systems. The integration of regional and local processes is central to predict species and ecosystem responses to future climate changes and ongoing anthropogenic disturbances.ecosystem regulation | predator distribution | landscape ecology | exploited resources | cross-system management

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Section: Resultssupporting

confidence: 91%

Predator transitory spillover induces trophic cascades in ecological sinks

Casini

Blenckner²,

Möllmann³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

102

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“…Figure 2), and from March to May in the Baltic Proper (see also Carstensen et al, 2004). This period covers also the spring bloom in the northern Baltic Proper (Höglander et al, 2004), Gulf of Finland (Niemi and Ray, 1977;Jaanus and Liiva, 1996), Gulf of Riga (Jurgensone et al, 2011), and the Bothnian Sea (Andersson et al, 1996). In the Bothnian Bay, the spring bloom concept is not directly applicable because the phytoplankton (diatom) growth may start rather late and reaches its peak usually only in June or July (Alasaarela, 1979).…”

Section: Methodsmentioning

confidence: 99%

The Diatom/Dinoflagellate Index as an Indicator of Ecosystem Changes in the Baltic Sea 1. Principle and Handling Instruction

et al. 2017

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Assessments of the environmental status of the Baltic Sea as called for by the Marine Strategy Framework Directive (MSFD) must be based on a set of indicators. A pre-core indicator is the diatom/dinoflagellate index (Dia/Dino index), which reflects the dominance of diatoms or dinoflagellates during the phytoplankton spring bloom. Here we explain the principles of the Dia/Dino index and the conditions for its calculation using examples from two very different water bodies, the Eastern Gotland Basin and Kiel Bay. The index is based on seasonal mean diatom and dinoflagellate biomass values. A precondition for its applicability is the coverage of the bloom. As a criterion, the maximum value of diatom or dinoflagellate biomass has to exceed a predefined threshold, e.g., 1000 µg/L in the investigated areas. If this condition is not fulfilled, an alternative Dia/Dino index can be calculated based on silicate consumption data. Changes in the dominance of these two phytoplankton classes impact the food web because both their quality as a food source for grazers and their periods of occurrence differ. If diatoms are dominant, their rapid sinking reduces the food stock for zooplankton but delivers plenty of food to the zoobenthos. Consequently, the Dia/Dino index can be used to follow the food pathway (Descriptor 4 of MSFD: "food web"). Moreover, a low Dia/Dino index may indicate silicate limitation caused by eutrophication (Descriptor 5 of MSFD: "eutrophication"). The Dia/Dino index was able to identify the regime shift that occurred at the end of the 1980s in the Baltic Proper. Diatom dominance, and thus a high Dia/Dino index, are typical in historical data and are therefore assumed to reflect good environmental status (GES). In assessments of the environmental status of the Eastern Gotland Basin and Kiel Bay, Dia/Dino index GES thresholds of 0.5 and 0.75, respectively, are suggested. The GES thresholds as calculated by the alternative Dia/Dino index are 0.84 and 0.94, respectively.

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“…The regeneration from sediment and water column and wet deposition could not provide enough DRSi for diatom blooms. Nutrient limitations in coastal waters may seasonally and spatially switch between nitrogen and phos- phorus limitation in response to variable nutrient inputs (Vuorio et al, 2005;Howarth and Marino, 2006;Jurgensone et al, 2011). In Sishili Bay, anthropogenic inputs also relieved DRSi limitations to a great extent, especially in the first 3 months of 2010.…”

Section: Nutrient Limitations In the Study Areamentioning

confidence: 99%