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Bonsdorff, Erik; Rönnberg, Cecilia; Aarnio, Katri

doi:10.1023/a:1020395526898

Cited by 54 publications

(6 citation statements)

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“…Eutrophication of the Baltic Sea, and possibly also climate changes, 4 are believed to contribute to an increase in the intensity and duration of the summer blooms. [5][6][7][8][9][10][11] The annual blooms are depleting the waters of oxygen and lead to formation of toxic sulfide in the bottom layers 12 and they also cause economic problems due to fish death and loss of tourism, and health hazards due to the toxicity of Nodularia. 13,14 To better understand the response of Nodularia to eutrophication and the factors promoting bloom formation, we need a deeper knowledge of its physiological and molecular responses to different nutrients such as nitrogen, phosphate and iron.…”

Section: Introductionmentioning

confidence: 99%

Variability in the response of the cyanobacterium Nodularia spumigena to nitrogen supplementation

Vintila

El-Shehawy

2010

J. Environ. Monit.

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Nodularia spumigena is a filamentous cyanobacterium that is commonly found in brackish water bodies. The species is capable of fixing atmospheric nitrogen in specialized cells termed heterocysts. N. spumigena dominates the annual toxic summer blooms in the Baltic Sea causing environmental and economical problems. We have previously demonstrated that N. spumigena strain AV1 exhibits a different response to the presence of combined nitrogen as compared to model cyanobacteria such as Nostoc PCC7120 and Nostoc punctiforme by uncoupling between nitrogen fixation and heterocyst differentiation.In order to assess whether or not the behaviour of N. spumigena strain AV1 is characteristic of N. spumigena populations, especially in the Baltic Sea, we have investigated the effect of nitrate and ammonium ions on growth, nitrogen fixation activity and presence of heterocysts in eight different Nodularia strains. Our results show that most of the strains retain heterocysts in the absence of nitrogenase activity indicating that uncoupling between nitrogen fixation and heterocyst differentiation is most likely a common behaviour among N. spumigena strains, especially in the Baltic Sea. In addition, there are variations between strains in regard to nitrate uptake.

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Section: Introductionmentioning

confidence: 99%

Variability in the response of the cyanobacterium Nodularia spumigena to nitrogen supplementation

Vintila

El-Shehawy

2010

J. Environ. Monit.

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“…The SW Finnish archipelago has a clear seasonal cycle in physicochemical processes: a stratification develops in the summer and in the winter and is interrupted by vertical autumn and spring circulations. Moreover, there are very high concentrations of organic dissolved matter [30], and the archipelago is therefore highly eutrophic [31,32].…”

Section: Study Areamentioning

confidence: 99%

Scalability of Water Property Measurements in Space and Time on a Brackish Archipelago Coast

2021

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Our paper aims at advancing global change management in marine archipelago environments. Water properties vary along temporal and vertical gradients, and studies indicate that these patterns may be site-specific, i.e., they may vary at local or regional scales. Understanding these complex processes is crucial for designing environmental monitoring campaigns or assessing the scalability of their results. To our knowledge, the four-dimensional (temporal, vertical and horizontal) patterns of water quality have not been statistically quantified. In this paper, we partition the variation in four key water property variables into temporal, vertical and horizontal dimensions, by utilising a unique pre-existing high-density dataset and multilevel regression modelling. The dataset comprised measurements of temperature, salinity, pH and chlorophyll-a concentration, sampled eight times from April to October on the SW Finnish archipelago coast. All variables were sampled along the depth gradient and at local (102 m) and regional scales (104 m) at 20 sites. All measured variables varied significantly along the temporal and vertical gradients, and the overall levels, temporal patterns and vertical gradients of these variables were significantly site-dependent. Our study confirms that many water properties, especially chlorophyll-a concentration, show high four-dimensional variability in the complex archipelago environment. Thus, studies on the regional dynamics of archipelago water properties call for a high sampling density in time, along the vertical gradient, and in space.

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“…The Baltic Sea (Figure 1) is a semi-closed marginal sea of the North Sea. As a shallow and brackish water sea (mean depth 54 m), it is ecologically sensitive [45,46]. The northern location (approx.…”

Section: Materials 21 Study Areamentioning

confidence: 99%

Partition of Marine Environment Dynamics According to Remote Sensing Reflectance and Relations of Dynamics to Physical Factors

et al. 2021

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Seawaters exhibit various types of cyclic and trend-like temporal alterations in their biological, physical, and chemical processes. Surface water dynamics may vary, for instance, when the timings, durations, or amplitudes of seasonal developments of water properties alter between years and locations. We introduce a workflow using remote sensing to identify surface waters undergoing similar dynamics. The method, called ocean surface dynamics partitioning, classifies pixels based on their temporal change patterns instead of their properties at successive time snapshots. We apply an efficient parallel computing method to calculate Dynamic Time Warping (DTW) time series distances of large datasets of Earth Observation MERIS-instrument reflectance data Rrs(510 nm) and Rrs(620 nm), and produce a matrix of time series distances between 12,252 locations/time series in the Baltic Sea, for both wavelengths. We define cluster prototypes by hierarchical clustering of distance matrices and use them as initial prototypes for an iterative process of partitional clustering in order to identify areas that have similar reflectance dynamics. Lastly, we compute distances from the time series of the reflectance data to selected physical factors (wind, precipitation, and changes in sea surface temperature) obtained from Copernicus data archives. The workflow is reproducible and capable of managing large datasets in reasonable computation times and identifying areas of distinctive dynamics. The results show spatially coherent and logical areas without a priori information about the locations of the satellite image time series. The alignments of the reflectance time series vs. the observational time series of the physical environment clarify the causalities behind the cluster formation. We conclude that following the changes in an aquatic realm by biogeochemical observations at certain temporal intervals alone is not sufficient to identify environmental shifts. We foresee that the changes in dynamics are a sensitive measure of environmental threats and therefore they will be important to follow in the future.

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Cited by 54 publications

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Variability in the response of the cyanobacterium Nodularia spumigena to nitrogen supplementation

Variability in the response of the cyanobacterium Nodularia spumigena to nitrogen supplementation

Scalability of Water Property Measurements in Space and Time on a Brackish Archipelago Coast

Partition of Marine Environment Dynamics According to Remote Sensing Reflectance and Relations of Dynamics to Physical Factors

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