Browsing by Author "Rytövuori, Suvi"

Phycobilins are the main light harvesting pigments in picocyanobacteria. Chlorophyll-a is the main photosynthetic pigment in cyanobacteria as in all phytoplankton. In cyanobacteria, most of chl-a is positioned within the non-fluorescing photosystem I (PSI). Cyanobacteria phycobiliproteins are the main photosynthetic pigments in photosystem II (PSII). Phycobilins fluorescence can be used to help assess the presence and monitoring of cyanobacteria. The fluorescence intensity depends on the examined cyanobacteria group, pigment concentration and phytoplankton growth phase. In this research I studied, using flow-through fluorometers, where the phycoerythrin (PE) fluorescence is originating from and its variation in the Baltic Sea. PE fluorescence signal measured with flow-through fluorometers was also compared with other optical measurements. This study was performed in summer 2016 as part of Alg@line and JERICO-Next projects. Flow-through fluorometers (TriOS and Chelsea) were installed to M/S Finnmaid ship, which trafficked regularly on its route Helsinki–Travemünde. The automated flow-through sensors onboard M/S Finnpartner collected continuous data during 25.5–31.8.2016. Along the route Travemünde-Helsinki, a refrigerated sampler collected water samples once a week from 3 stations. Water samples acted as a reference samples for PE fluorescence signal analysis. Water samples were separated by filtration into three size fractions (total < 2 µm, and < 0.2 µm) and an excitation-emission spectrum was measured. The number of picocyanobacteria/ml, their surface area/ml and biovolume/ml was calculated using epifluorescence microscope. The number of PE-containing picocyanobacteria cells/ml and size was determined by flow cytometer and number of larger PE-containing phytoplankton cells, their size and taxonomy was determined using FlowCam. Most of the PE-fluorescence measured during summer 2016 was originating from pico-fraction. There was not a clear connection between flow-through PE fluorometers and other optical measurements. PE signal originating from fluorometers did not correlate with total fluorescence signal measured with spectrofluorometer. A reason for this can be that the sample has suffered preservation and transport due to the elapsed time. Some of the optical measurements correlated well with each other, and some did not. Excitation-emission spectrum measured from pico-fraction correlated with picocyanobacteria surface area/ml calculated with epifluorescence microscope. This can be explained by the fact that picocyanobacteria pigments are mainly located in the cell membrane. Number of cells/ml calculated with flow cytometer was much lower than the number/ml calculated with epifluorescence microscope. Sample could have been too dense when multiple cells has been interpreted as one larger cell. The program used for the grouping of cells could have also left low PE fluorescence value containing cells without counts. PE fluorescence originating from over 2 µm size fraction measured with spectrofluorometer and fluorescence originating from over 3 µm fraction pictured with FlowCam was not observed similar incidence of various stations in the summer of 2016. PE fluorometers alone are not sufficient for monitoring picocyanobacteria cells containing phycoerythrin in the Baltic Sea but PE fluorometers can be used as support to other methods.