Phytoplankton, protozooplankton and nutrient dynamics in the Bornholm Basin (Baltic Sea) in 2002–2003 during the German GLOBEC Project

Abstract

From March 2002 to until April 2003 we investigated the seasonal nutrient and phytoplankton dynamics in the central Bornholm Basin (Baltic Sea) within the framework of the German GLOBEC Project. We choose a nested approach consisting of vertical fluorescence profiles, phytoplankton counts and nutrient analyses. The Fluoroprobe (MultiProbe, BBE Moldaenke) is capable of distinguishing four algal groups (Cryptophyceae, Cyanophyceae, Chlorophyceae, Bacillariophyceae + Dinophyceae). Winter nutrient concentrations were about 5 lM NO 3 and 0.5 lM PO 4 in the central Basin. The spring phytoplankton bloom was dominated by the diatom Skeletonema sp. and reached a maximum of about 270 lg C/l before the onset of the seasonal stratification. Protozooplankton was dominated by the Mesodinium rubrum (a phototrophic ciliate = Myrionecta rubra) and reached a maximum biomass of about 200-300 lg C/l about 2 weeks after the demise of the diatom spring bloom. During summer, the water column was stratified and a subsurface maximum developed near the thermocline consisting of Bacillariophyceae, Cryptophycea and other phototrophic flagellates. Phytoplankton and protozooplankton biomass was generally low. Nutrient concentrations point towards a nitrogen limitation during this period. The stratification period ended during September and surface nutrient concentrations increased again. Protozooplankton reached a second maximum during September. With the Fluoroprobe small scale structures in the plankton community could be detected like a subsurface Cryptophyceae maximum near the thermocline that however, could not be confirmed by cell counts. The chlorophyll a estimate of the Fluoroprobe was in good agreement with the phytoplankton biomass estimated from counts. We conclude that only by combining modern sensing technology with microscopy, the small-scale dynamics and taxonomic spectrum of the plankton can be fully captured.

Predicting the Electron Requirement for Carbon Fixation in Seas and Oceans

“…In the Gulf of Finland, for example, vertical mixing and the depth of the surface mixed layer change across different seasons [73]–[75] and with it the optical and physicochemical properties of the water column, that is, light and nutrient availability of the extant phytoplankton community [29]. The clustering of the Gulf of Finland samples - into a late winter (b), spring (c), summer (g) and summer/early autumn (h) mirrors these physicochemical changes.…”

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

“…For example, in the southern Benguela upwelling system, egg production by adult female copepods was higher in waters dominated by diatoms than by microflagellates (Walker and Peterson, 1991). Recently, low food quality of diatoms (Ask et al, 2006;Dutz et al, 2008;Koski et al, 2008) and the inhibitory effects of this group of organisms (Turner et al, 2001;Ianora et al, 2003;Barreiro et al, 2011) have also been described, leading Uusitalo et al (2013) to conclude that diatoms can generally be considered as poor-quality food. According to Vehmaa et al (2012), however, a food-quality approach based on class level is too simplistic; rather, phytoplankton taxa must be considered at the species level.…”

“…The development of indicators was advanced particularly in the projects MARMONI (http://marmoni.balticseaportal.net/ wp/), CORESET (HELCOM, 2013), WATERS (Höglander et al, 2013), GES-REG (Uusitalo et al, 2013), and HOLAS (http:// www.helcom.fi/helcom-at-work/projects/holas-ii/). Finally, the responsibility is located on the national level.…”

Seasonal dynamics of fecundity and recruitment of Temora longicornis in the Baltic Sea

“…Sampling was conducted from March 2002 to April 2003. The microplankton taxonomic composition and biomass were analysed as described in detail by Van Beusekom et al (2009). In short, after concentration in settling chambers, phyto-and microzooplankton were counted with an inverted microscope at 200× to 400× magnification and then classified into taxonomic categories.…”