Naslov
Marine diatoms overcoming the phosphorus limitation: the Northern Adriatic case study

Autori
Godrijan, Jelena ; Marić Pfannkuchen, Daniela, Ivančić, Ingrid ; Precali, Robert ; Pfannkuchen, Martin ;

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Abstract book of the 8th Central European Diatom Meeting / Ljubešić, Zrinka ; Godrijan, Jelena ; Marić Pfannkuchen, Daniela ; - Zagreb : Hrvatsko Botaničko Društvo, 2014, 26-26

ISBN
978-953-99774-7-2

Skup
8th Central European Diatom Meeting

Mjesto i datum
Zagreb, Hrvatska, 10.04.2014. - 13.04.2014

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
northern Adriatic; diatoms; P limitation

Sažetak
The northern Adriatic is a shallow, semi-enclosed area characterized by a set of ecological gradients which provide a large variety of environmental conditions. Discharges of the Po River and different circulation patterns are major drivers of nutrient input and distribution, governing the phytoplankton dynamics in the area. Phytoplankton assemblage in the northern Adriatic is dominated by diatoms, with blooms occurring in February, May, July and October. During summer stratification surface waters of the northern Adriatic are P limited. Diatoms adapt to this ecological challenge via utilization of dissolved organic phosphorus by membrane bound alkaline phosphatase (AP). The prevalence of smaller cell size species during summer, like Chaetoceros sp. and Pseudo–nitzschia sp, indicates their supreme adaptability to P-limitation. Furthermore, the synergy between AP upregulation and synthesis of non-phospholipids enables cells to sustain the high rate of primary production and to increase their biomass. Presumably the biological cycling of phosphorus controls its availability in the system, and could actively influences biomass and production, as well as changes in the community compositions. The objectives of this study were to evaluate the mechanisms with which the diatom community adapted to orthophosphate starvation, to identify the key species in the community as well as the physiological processes underlying their adaptation. In situ studies were carried out during 2013 encompassing periods of stratification as well as the mixing in the water column. Samples were taken for analysis of alkaline phosphatase activity (APA) as well as taxonomic and physiological studies of the diatom community. Additionally, several species were cultured and subjected to orthophosphate starvation, to further investigate their adaptive strategy in a P-limited system. Diatom assemblage was dominated by the Chaetoceros–Rhizosolenia (Proboscia) community. Succession of species followed the typical sequence and the community was dominated by genera: Chaetoceros, Pseudo–nitzschia, Proboscia, Rhizosolenia, Bacteriastrum, Cerataulina, Leptocylindrus and Thalassionema. During the whole summer period APA was induced, and P turnover time was very short. Differences in APA production in cultured strains were evident and certain species were able to produce ample amounts of AP. We were able to microscopically localize and quantify the AP production and activity on a sub cellular level of selected diatoms and distinguish it from intracellular AP activity as well as from possible bacterial production. With this methodology we investigated field samples (in situ status) and cell cultures. Our results indicate that a major selective pressure on diatom species is ortophospate starvation and that adaptive live strategies are related to AP production. Species capable of high AP production and activity are continuously selected in the conditions of P limitation in areas such as the northern Adriatic. Key species within the NAs phytoplankton do have to respond to this challenge.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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