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Microbial plankton communities in the coastal southeastern Black Sea : biomass, composition and trophic interactions

Aytan U., Feyzioglu A. M., Valente A., Agirbas E., Fileman E. S.

Oceanologia

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2018

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No. 60 (2)

139--152

EN

We investigated biomass and composition of the pico-, nano- and microplankton communities in a coastal station of the southeastern Black Sea during 2011. We also examined trophic interactions within these communities from size-fractionated dilution experiments in February, June and December. Autotrophic and heterotrophic biomasses showed similar seasonal trends, with a peak in June, but heterotrophs dominated throughout the year. Autotrophic biomass was mainly comprised by nanoflagellates and diatoms in the first half of the year, and by dinoflagellates and Synechococcus spp. in the second half. Heterotrophic biomass was mostly dominated by heterotrophic bacteria, followed by nanoflagellates and microzooplankton. Dilution experiments suggest that nano- and microzooplankton were significant consumers of autotrophs and heterotrophic bacteria. More than 100% of bacterial production was consumed by grazers in all experiments, while 46%, 21% and 30% of daily primary production were consumed in February, June and December, respectively. In February, autotrophs were the main carbon source, but in December, it was heterotrophic bacteria. An intermediate situation was observed in June, with similar carbon flows from autotrophs and heterotrophic bacteria. Size-fraction dilution experiments suggested that heterotrophic nanoflagellates are an important link between the high heterotrophic bacterial biomass and microzooplankton. In summary, these results indicate that nano- and microzooplankton were responsible for comprising a significant fraction of total microbial plankton biomass, standing stocks, growth and grazing processes. This suggests that in 2011, the microbial food web was an important compartment of the planktonic food web in the coastal southeastern Black Sea.

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Latitudinal pattern of abundance and composition of ciliate communities in the surface waters of the Atlantic Ocean

Rychert K., Nawacka B., Majchrowski R., Zapadka T.

Oceanological and Hydrobiological Studies

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2014

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Vol. 43, No. 4

4436--441

EN

Abundance, biomass, and taxonomic composition of the ciliate community were studied in the surface waters along a transect between 50°S 61°W and 48°N 5°W (Atlantic Ocean, March-April 2011). The abundance of heterotrophic ciliates was low in the equatorial zone (280–320 cells l−1, 0.11–0.12 μg C l−1), but it increased toward both the northern and southern temperate zones with the maximum abundance observed at 44°S (2667 cells l−1, 0.82 μg C l−1). This pattern resembles the global distribution of oceanic primary production, which is low at lower latitudes and high in temperate zones. In temperate zones ciliate abundance peaks during spring and fall. Thus, because the present study was carried out during spring in the northern hemisphere and austral fall in the southern hemisphere, the ciliate abundance at higher latitudes was additionally elevated. Functionally autotrophic Mesodinium rubrum was only observed in the northern hemisphere and tropical waters. Its maximum abundance was observed at 48°N (1080 cells l−1, 1.14 μg C l−1). The most frequently observed ciliates were oligotrichs and choreotrichs. Other important ciliates were haptorids (including M. rubrum) and hypotrichs.

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Modelling the seasonal dynamics of marine plankton in the southern Baltic Sea. Part 2. Numerical simulations

Dzierzbicka-Głowacka L.

Oceanologia

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2006

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No. 48 (1)

41-71

EN

This work presents numerical simulations of the time-dependent vertical distributions of phytoplankton, microzooplankton, Pseudocalanus elongatus, early juvenile herring (Clupea harengus) and two nutrient components (total inorganic nitrogen and phosphate) using the 1D-Coupled Ecosystem Model with a high-resolution mesozooplankton (herbivorous copepods) module for P. elongatus and a simple prey-predator model for early juvenile herring C. harengus. This model was discussed in detail in Part 1. The calculations were done for one year (1999) for astation in the Gdańsk Deep (southern Baltic Sea). The results of the simulations were compared with the mean concentrations of nutrients, phytoplankton and zooplankton recorded in situ. The differences between the calculated and mean recorded values of nutrients and phytoplankton are c. 5-30% and depend on the month and depth for which the calculations were done. However, the calculated depth-integrated biomass of P. elongatus differs from the mean recorded value. This difference ranges from 30 to 50% at the end of May. The 1DCEM model can be used to forecast ecological changes in the southern Baltic Sea.

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Modelling the seasonal dynamics of marine plankton in the southern Baltic Sea. Part 1. A Coupled Ecosystem Model

Dzierzbicka-Głowacka L.

Oceanologia

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2005

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No. 47 (4)

591-619

EN

The paper presents a one-dimensional Coupled Ecosystem Model (1DCEM) consisting of three submodels: a meteorological submodel for the physics of the upper layer and a biological submodel, which is also driven by output from the physical submodel. The biological submodel with a high-resolution zooplankton module and a simple prey-predator module consists of seven mass conservation equations. There are six partial second-order differential equations of the diffusion type for phytoplankton, microzooplankton, mesozooplankton, fish, and two nutrient components (total inorganic nitrogen and phosphate). The seventh equation, an ordinary differential equation, describes the development of detritus at the bottom. In this model the mesozooplankton (herbivorous copepods) is represented by only one species - Pseudocalanus elongatus - and is composed of 6 cohorts. The fish predator is represented by 3 cohorts of early juvenile herring Clupea harengus. Hence, the biological submodel consists of an additional twelve equations, six for weights and six for the numbers in 6 cohorts of P. elongatus, and three equations for the biomasses of 3 predator cohorts. This model is an effective tool for solving the problem of ecosystem bioproductivity and was tested in Part 2 for one partcular year.