Succession and growth limitation of phytoplankton in the Gulf of Bothnia (Baltic Sea)

Andersson, Agneta; Hajdu, Susanna; Haecky, Pia; Kuparinen, Jorma; Wikner, Johan

doi:10.1007/bf00351346

Cited by 120 publications

(107 citation statements)

References 18 publications

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“…Biological uptake effectively removed discharged nitrate near-shore, resulting in surplus phosphate being transported to the open sea (Humborg et al 1998). The absence of a clear summer increase in total nitrogen in the Bothnian Sea (data not shown), where filamentous diazotrophic cyanobacteria are less common (Andersson et al 1996), also supports this argument.…”

Section: Discussionmentioning

confidence: 71%

Baltic Sea nitrogen fixation estimated from the summer increase in upper mixed layer total nitrogen

Larsson

Hajdu

Walve

et al. 2001

Limnology & Oceanography

259

290

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We estimated nitrogen fixation from the increase in total nitrogen (N 2 gas excluded) in the upper 20 m during the summer biomass increase of heterocystous filamentous cyanobacteria at the off-shore Landsort Deep station (BY31, 5 yr) and at 10 more stations in all major basins of the Baltic Sea proper. Estimated fixation rates were 2.3-5.9 mmol N m Ϫ2 d Ϫ1, within the range of reported direct measurements. Estimated total fixation in the Baltic Sea proper, 180-430 Gg N yr Ϫ1 taking nitrogen settling loss and atmospheric deposition into account, was sufficient to sustain 30-90% of the June-August pelagic net community production. Filamentous cyanobacteria (mostly Aphanizomenon sp.) had low C : N and C : P ratios in spring 1998, indicating internal storage of both N and P. From early June, when their biomass growth started, ratios rose gradually to the biomass peak in August and early September, when the C : N ratio (6.5 mol/mol) was close to the Redfield ratio, but the C : P ratio reached 420, almost four times Redfield. The C : N ratio of the peak biomass was 1.5 times that in spring, and the C : P ratio was 13 times higher. The high C : P ratio indicates a smaller P demand by filamentous diazotrophs than expected from Redfield ratios. Only a few percent of the P mineralized daily is needed for filamentous cyanobacterial growth in summer. Filamentous cyanobacteria incorporated 16-41 mmol N m Ϫ2 into biomass (C : N ϭ 6.2) at BY31 in summer 1998. This was less than the estimated nitrogen fixation, suggesting fixed N leaks from growing diazotrophs.

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Section: Discussionmentioning

confidence: 71%

Baltic Sea nitrogen fixation estimated from the summer increase in upper mixed layer total nitrogen

Larsson

Hajdu

Walve

et al. 2001

Limnology & Oceanography

259

290

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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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“…For example, the low salinity Bothnian Bay in the northern Baltic Sea is P-limited year around (Andersson et al, 1996), whereas the higher salinity open waters of the Baltic display N-limitation throughout (Granéli et al, 1990). It is only where freshwater enters these Baltic coastal systems, as in the Himmerfjärden Estuary (Elmgren & Larsson, 1977) and in the Gulf of Riga (Maestrini et al, 1997), where seasonal switches in nutrient limitation occurs.…”

Section: Nutrient Limitationmentioning

confidence: 99%

Biogeochemical nutrient cycles and nutrient management strategies

Conley¹

1999

Man and River Systems

175

154

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Nutrient loading by riverine input into estuarine systems has increased by 6-50 times for the N load from pristine conditions to present, whereas a 18-180 times increase has been observed in the P load. Reductions in the ratio of N to P delivery has also occurred with time. In a review of nutrient limitation in estuarine systems, it is shown that many estuarine systems display P limitation in the spring, switching to N limitation in the summer with some estuaries displaying dissolved silicate limitation of the spring diatom bloom. Historical and recent changes in nutrient loading and their effect on nutrient limitation have intensified the debate on the control of nutrient delivery to estuaries from both agricultural and point sources, and as to what nutrient (N or P) should be managed for in estuarine systems. It is hypothesized that potential reductions in P may help oxygen depletion especially in deep estuaries and reduce fast growing macrophytes such as Ulva sp., although P reductions probably will have little effect on summer chlorophyll concentrations, an important recreational management goal. Reductions in N loading should reduce summer chlorophyll concentrations and improve the conditions for submerged aquatic vegetation and thus improve ecosystem functioning. Finally, if only P reductions are pursued, that is if we are able to reduce P such that it is limiting year around in estuarine systems, it is likely that the export of N from estuarine systems would increase to the bordering N-limited marine systems, thus only exporting the problem of enhanced production with eutrophication.

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Succession and growth limitation of phytoplankton in the Gulf of Bothnia (Baltic Sea)

Cited by 120 publications

References 18 publications

Baltic Sea nitrogen fixation estimated from the summer increase in upper mixed layer total nitrogen

Baltic Sea nitrogen fixation estimated from the summer increase in upper mixed layer total nitrogen

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

Biogeochemical nutrient cycles and nutrient management strategies

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