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We studied the loadings of dissolved organic matter (DOM) and nutrients from the Neva River into the Eastern Gulf of Finland, as well as their distribution within the salinity gradient. Concentrations of dissolved organic carbon (DOC) ranged from 390 to 840 mu M, and were related to absorption of colored DOM (CDOM) at 350 nm, a(CDOM)(350), ranging from 2.70 to 17.8 m(-1). With increasing salinity both DOC and a(CDOM) decreased, whereas the slope of a(CDOM) spectra, S-CDOM(300-700), ranging from 14.3 to 21.2 mu m(-1), increased with salinity. Deviations of these properties from conservative mixing models were occasionally observed within the salinity range of approximately 1-4, corresponding to the region between 27 and 29 degrees E. These patterns are suggested to mostly reflect seasonal changes in properties of river end-member and hydrodynamics of the estuary, rather than non-conservative processes. On the other hand, observed nonlinear relationships observed between a(CDOM)*(350) and S-CDOM(275-295) emphasized the importance of photochemistry among various transformation processes of DOM. Dissolved inorganic nitrogen was effectively transformed in the estuary into particulate organic nitrogen (PON) and dissolved organic nitrogen (DON), of which DON was mostly exported from the estuary, enhancing productivity in nitrogen limited parts of the Gulf of Finland. DON concentrations ranged from 12.4 to 23.5 mu M and its estuarine dynamics were clearly uncoupled from DOC. In contrast to DOC, estuarine DON dynamics suggest that its production exceeds losses in the estuary. Total nitrogen (TN) and phosphorus (TP) loadings from the Neva River and St. Petersburg were estimated as 73.5 Gg N yr(-1) and 4.2 Gg P yr(-1), respectively. Approximately 59% of TN and 53% of TP loads were in organic forms. DOC and DON loadings were estimated as 741.4 Gg C yr(-1) and 19.0 Gg N yr(-1), respectively. Our estimate for DOC loading was evaluated against a previously published carbon budget of the Baltic Sea. According to the updated model, the Baltic Sea could be identified as a weak source of carbon into the atmosphere. (C) 2016 The Authors. Published by Elsevier B.V.

Distribution of cyanobacteria cannot be evaluated using chlorophyll a (Chl a ) in vivo fluorescence, as most of their Chl a is located in non-fluorescing photosystem I. Phycobilin fluorescence, in turn, is noted as a useful tool in the detection of cyanobacterial blooms. We applied phycocyanin (PC) fluorometer in the monitoring of the filamentous cyanobacterial bloom in the Baltic Sea. For the bloom forming filamentous cyanobacteria Aphanizomenon flos-aquae and Nodularia spumigena , PC fluorescence maximum was identified using the excitation–emission fluorescence matrix. Consequently, the optical setup of our instrument was noted to be appropriate for the detection of PC, and with minor or no interference from Chl a and phycoerythrin fluorescence, respectively. During summer 2005, the instrument was installed on a ferryboat commuting between Helsinki (Finland) and Travemunde (Germany), and data were collected during 32 transects providing altogether 200 000 fluorescence records. PC in vivo fluorescence was compared with Chl a in vivo fluorescence and turbidity measured simultaneously, and with Chl a concentration and biomass of the bloom forming filamentous cyanobacteria determined from discrete water samples. PC fluorescence showed a linear relation to the biomass of the bloom forming filamentous cyanobacteria, and the other sources of PC fluorescence are considered minor in the open Baltic Sea. Estimated by PC fluorescence, cyanobacterial bloom initiated late June at the Northern Baltic Proper, rapidly extended to the central Baltic Proper and the Gulf of Finland, and peaked in the mid-July with values up to 10 mg l −1 (fresh weight). In late July, bloom vanished in most areas. During single transects, or for the whole summer, the variability in Chl a concentrations was explained more by PC fluorescence than by Chl a fluorescence. Thus, filamentous cyanobacteria dominated the overall variability in phytoplankton biomass. Consequently, we show that during the cyanobacterial blooms, the estimation of Chl a concentration using only Chl a in vivo fluorescence is not applicable, but PC in vivo fluorescence is required as a predictor as well.

Finnish Institute of Marine Research (FIMR) as a founding member of Alg@line consortium has been a forerunner in the field of monitoring research using commercial ferries. In 1992 FIMR started continuous measurements on board the ferry Finnjet, crossing the Baltic Sea Proper, using unattended recording and sampling system. During the spring of 2007 the ferrybox monitoring system was reinstalled in a new ferry Finnmaid providing real time observed data transmission with satellite connection. Chlorophyll-a (Chla) still remains the principal monitoring parameter. However, the distribution of cyanobacteria cannot be evaluated using Chla in vivo fluorescence, as most of their Chla is located in the poorly-fluorescing photosystem I. Instead, phycocyanin (PC) fluorescence is used in the detection of cyanobacterial blooms in 2005-07. PC fluorescence shows a linear relation to the biomass of the bloom forming filamentous cyanobacteria. During blooms of filamentous cyanobacteria the variability in Chla concentrations is better explained by PC fluorescence than by Chla fluorescence. Additionally, Chla records have been applied in validation of MODIS satellite monitoring for the water quality.

[1] Satellite observations and surface-observed transect data are combined to assess the spatial characteristics of water quality in the Baltic Sea, northern Europe. The technique that optimally assimilates the two data sources is based on Bayes' theorem. The method considers the spatial accuracy characteristics of both transect and satellite data. The mathematical formulation of the method is generally applicable. Hence it can be applied to other environmental monitoring problems as well. This investigation demonstrates its feasibility for water quality mapping. The characteristic under investigation is chlorophyll (chl a) concentration, which is currently operationally monitored in the Baltic Sea at shipborne Alg@line transects, using flow-through fluorometer sampling systems. In order to optimally extrapolate transect observations the developed method benefits from the full spatial coverage of spaceborne optical spectroradiometer data. The results show that the estimation accuracy of regional chl a concentration during the spring bloom period substantially improves as satellite observations are assimilated to transect data. The assimilation results show significantly higher accuracies than those obtained using either extrapolated transect data or stand-alone retrieval algorithms for satellite data.

The Baltic Sea is a unique continental brackish water sea. Today the Baltic Sea is eutro- phied and the blooms of harmful planktonic algae are annual phenomena. The blooms are harmful to the marine ecosystem as well as to the recreational and economic use of marine resources. High-quality research gives reliable information on the state of the ecosystem and its changes. Adequate monitoring information is a prerequisite for sound protection measures and only research is able to reliably show the effects of the protection investments. Because the phytoplankton blooms are extremely patchy and temporally rapidly changing, they often remain unobserved when using traditional sampling methods.

FerryBox monitoring provides cost-effective means to study the coastal ocean. In the Baltic Sea, FerryBox measurements have been conducted already for three decades. Despite the lack of formal structuration of the network, the Baltic FerryBox community has been interacting and collaborating actively in the maintenance of systems, in calibration of sensors, extending the suite of measured variables, and in improving the overall quality of measurements. However, the emerging needs for improving the consistency and availability of data and products call for better structuration of collaboration. EU funded JERICO-RI (Joint European Research Infrastructure of Coastal Observatories) provides a pan-European framework to improve the regional networking and transnational harmonization. Here we provide an overview of current collaborations within Baltic FerryBox community and an outlook for next actions, to be tested during JERICO-RI Pilot Supersite demonstration phase in 2021-22.