Influence of organic and inorganic nutrients on the phytoplankton structure of the Gulf of Riga and development of potentially toxic algae

Darba mērķis bija veikt pētījumus par izšķīdušo organisko un neorganisko biogēnu ietekmi uz Rīgas līča fitoplanktona struktūras veidošanos un potenciāli toksisko aļģu attīstību. Biogēnu limitēšanas eksperimenti pierādīja, ka slāpeklis ir galvenais limitējošais elements Rīgas līcī, īpaši vasarās un ārpus upju ietekmes zonas. Fosfors pamatā limitēja fitoplanktona attīstību pavasaros un upju grīvu rajonos. Eksperimentos ar neorganiskajiem biogēniem novērota intensīva kramaļģu attīstība. Neorganisko biogēnu izsīkums izraisīja fitoplanktona sugu daudzveidības samazināšanos, miksotrofo un potenciāli toksisko aļģu biomasas pieaugumu. Eksperimenti ar organiskajām slāpekli saturošajām vielām pierādija, ka labākais organiskā slāpekļa avots Rīgas līča vasaras fitoplanktonam ir urīnviela, bet fitoplanktona attīstību stimulē arī brīvās aminoskābes un purīni. Par būtisku biogēnu rezervi uzskatāmas arī sauszemes izcelsmes organiskās vielas. Upju ienestās lielmolekulārās izšķīdušās organiskās vielas galvenokārt veicina dinoflagellātu attīstību. Kopumā rezultāti liecina, ka sauszemes izcelsmes organiskajām vielām ir būtiska loma Rīgas līča fitoplanktona attīstībā, tās izraisa būtiskas fitocenozes taksonomiskās izmaiņas, miksotrofo un arī potenciāli toksisko (Microcytis spp., Dinophysis acuminata) sugu īpatsvara pieaugumu, kā arī tālākas izmaiņas Rīgas līča barības ķēdēs.The aaim of the study was to detect the influence of diisoved inorganic and organic nutrients on the phytoplankton composition of the Gulf of Riga and growth of potentially toxic algae. Experiments of nutrient limitation proved that nitrogen is the main limiting nutrient in the Gulf of Riga, especially during summer period and outside of rivers influence. Phosphorus mainly was limiting the phytoplankton development in the springtime and in the river plums. Experiments with different nutient concentrations showed that elevated inorganic nutrients concentrations causes increased development of diatoms, but depletion of nutrients induces decrease of species diversity, and growth of mixotrophic and potentially toxic organisms. An experiment with low molecular weight organic nitrogen compounds revealed that urea is the best organic source of nitrogen for summer phytoplankton. The growth of algae was stumulated also by dissolved free amino acids and purines. Dissolved organic matter from terrestrial origin should be considered as significant source of nutrients during summer time. Terrestrially derived high molecular weight organic matter favours the development of dinoflagellates, but low molecular weight organic substances stimulates the growth of cryptophytes, chlorophytes and colonial cyanobacteria. Altogether, resulta showed, that organic matter from terrestrial origin plays significant role in the development of phytoplankton of the Gulf of Riga, provokes changes of species diversity, causes increase of mixotrophic and potentially toxic species (e.g. Microcystis spp., Dinophysis acuminata), as well as induces further changes in the food webs of Gulf of Riga

BONUS BASMATI Specification of requirements on data and modelling needs. Deliverable 6.1.

Maritime Spatial Planning (MSP) requires a spatially explicit framework for decision-making and on that background the overall objective of BONUS BASMATI is to develop integrated and innovative solutions for MSP from the local to the Baltic Sea Region scale. Based on the results of former MSP projects, the BONUS BASMATI project sets out to analyse governance systems and their information needs regarding MSP in the Baltic Sea region in order to develop an operational, transnational model for MSP, while maintaining compliance with existing governance systems. It also develops methods and tools for the assessments of different plan proposals, while including spatially explicit pressures and effects on marine ecosystem services in order to create a spatial decision support system (SDSS) for the Baltic Sea region to facilitate broad access to information. During the project running until 2020, new data will be produced and tested in assessments corresponding to policy goals. The data will support analysis regarding ecosystem services: provisioning, regulating, and cultural services. A central aim of the project is to facilitate cross-border collaboration and the project is carried out in close cooperation with relevant stakeholders in the Baltic Sea Region. The impact of the project will be facilitated and assessed in transnational case studies, where integrated solutions are required. The local scale will consist of case study areas in the South-West Baltic, the Latvian territorial and EEZ waters including open part of the Baltic Sea and the Gulf of Riga, and across the region, a pan-Baltic case study will be performed.</p