Carbon cycling in the pelagic environment

Važan dio pelagičkog ekosustava je epipelagijal, područje slobodne vode do oko 150 m dubine u kojem se razvija primarni proizvođač – fitoplankton. Fitoplankton se razvija unutar godišnjih ciklusa, a u ovisnosti o fizikalno-kemijskim i biotičkim čimbenicima. Organsku tvar u moru predstavlja čitav niz ugljikovih. Prema porijeklu može biti alohtona, donesena iz drugih sustava i autohtona, porijeklom od primarne produkcije. Autohtona organska tvar proizvedena u epipelagijalu potrebna je svim životnim zajednicama u moru a posebno onima na dnu. Pelagički sustavi imaju mehanizme recikliranja i vertikalnog prijenosa organske tvari. Taj se prijenos najčešće odvija putem agregiranja i sedimentacije organske tvari te putem hranidbenih mreža. Agregiranje organske tvari u obliku „morskog snijega“ i njeno tonjenje posljedica je cvjetanja dijatomeja. Stanice dijatomeja luče ljepljive polisaharide koji djeluju kao središta agregiranja i dok tonu na sebe vežu organsku tvar. Način prijenosa organske tvari u dubinu su i fekalne grudice zooplanktona koje sadrže neprobavljenu organsku tvar. Bakterijska razgradnja te mikrobni krug važni su za recikliranje otopljene organske tvari i njeno vraćanje u hranidbenu mrežu.Important part of pelagic environment is its upper layer, shallower than 150 m which contains the biggest biomass of primary producers – phytoplankton (photic zone). Phytoplankton develops in regular annual cycles which depend on certain physical, chemical and biological parameters. The organic matter in the sea is represented by carbon compounds. Organic matter in the sea can originate from other ecosystems (alochtonous) or it can be produced by primary producers (autochtonous). The one that is assimilated in epipelagic zone is vital for all marine ecosystems, especially for those on the bottom of the ocean. Pelagic system has mechanisms for recycling and vertical export of organic matter. It is conducted by aggregation and sedimentation of organic matter or through different food webs. Aggregation of organic metter and its sinking is taking place after large diatom blooms, and it's also called „marine snow“. „Marine snow“ is created by sticky diatom exopolimers which act as centers of aggregation. Faecal pellets of zooplankton are also very important way of vertical transport. They contain non-digested organic matter. Microbial decomposers recycle dissolved organic matter and return it into food web

Carbon cycling in the pelagic environment

Važan dio pelagičkog ekosustava je epipelagijal, područje slobodne vode do oko 150 m dubine u kojem se razvija primarni proizvođač – fitoplankton. Fitoplankton se razvija unutar godišnjih ciklusa, a u ovisnosti o fizikalno-kemijskim i biotičkim čimbenicima. Organsku tvar u moru predstavlja čitav niz ugljikovih. Prema porijeklu može biti alohtona, donesena iz drugih sustava i autohtona, porijeklom od primarne produkcije. Autohtona organska tvar proizvedena u epipelagijalu potrebna je svim životnim zajednicama u moru a posebno onima na dnu. Pelagički sustavi imaju mehanizme recikliranja i vertikalnog prijenosa organske tvari. Taj se prijenos najčešće odvija putem agregiranja i sedimentacije organske tvari te putem hranidbenih mreža. Agregiranje organske tvari u obliku „morskog snijega“ i njeno tonjenje posljedica je cvjetanja dijatomeja. Stanice dijatomeja luče ljepljive polisaharide koji djeluju kao središta agregiranja i dok tonu na sebe vežu organsku tvar. Način prijenosa organske tvari u dubinu su i fekalne grudice zooplanktona koje sadrže neprobavljenu organsku tvar. Bakterijska razgradnja te mikrobni krug važni su za recikliranje otopljene organske tvari i njeno vraćanje u hranidbenu mrežu.Important part of pelagic environment is its upper layer, shallower than 150 m which contains the biggest biomass of primary producers – phytoplankton (photic zone). Phytoplankton develops in regular annual cycles which depend on certain physical, chemical and biological parameters. The organic matter in the sea is represented by carbon compounds. Organic matter in the sea can originate from other ecosystems (alochtonous) or it can be produced by primary producers (autochtonous). The one that is assimilated in epipelagic zone is vital for all marine ecosystems, especially for those on the bottom of the ocean. Pelagic system has mechanisms for recycling and vertical export of organic matter. It is conducted by aggregation and sedimentation of organic matter or through different food webs. Aggregation of organic metter and its sinking is taking place after large diatom blooms, and it's also called „marine snow“. „Marine snow“ is created by sticky diatom exopolimers which act as centers of aggregation. Faecal pellets of zooplankton are also very important way of vertical transport. They contain non-digested organic matter. Microbial decomposers recycle dissolved organic matter and return it into food web

Sastav i prostorna raspodjela fitoplanktona u sjeveroistočnom kanalu Jadranskog mora u jesen 2008. godine

The Velebit and Pag Channels form a 40 km long and 4-14 km wide system running parallel to the northeastern Adriatic coast. The aim of this study was to investigate phytoplankton abundance, composition and distribution along the system in the autumn period. Sampling was carried out at 8 stations in November 2008. The spatial distribution of physico-chemical parameters indicated the existence of a pronounced horizontal thermohaline and trophic gradient. From the inner part of the Velebit Channel, which is an extension of the karstic Zrmanja River estuary, to the outer end of the Pag Channel, which communicates with the open sea, the temperature and salinity ranged from 11.0 to 16.0 °C and from 23.4 to 38.2, respectively. Nutrient concentrations ranged from 0.001 to 0.1 µmol L-1 for orthophosphates, from 0.85 to 7.0 µmol L-1 for total inorganic nitrogen and from 0.3 to 15.4 µmol L-1 for silicates. Total abundance of phytoplankton decreased from 5.5 x 105 cells L-1 to 8.5 x 104 cells L-1 along the trophic gradient. Diatoms dominated the phytoplankton with maximum abundances from 7.3 x 104 cells L-1 (85% of total phytoplankton) at the most oligotrophic stations up to 9.6 x 105 cells L-1 (96% of total phytoplankton) at the nutrient enriched stations. Statistical analysis on the basis of environmental and biological parameters clustered the stations in three main groups. The first group represented the southern Velebit Channel with higher nutrient levels and phytoplankton dominated by Thalassionema nitzschioides. The second group included stations from the middle Velebit Channel with significantly lower levels of nutrients, and phytoplankton mostly dominated by Bacteriastrum sp. with a contribution by various diatom species. The third group represented the stations from the Pag Channel, and associated with the exclusive domination of Bacteriastrum sp. and a greater contribution of coccolithophorids. This paper also gives the first checklist of species present in the extremely oligotrophic area of the Velebit and Pag Channels. 148 taxa were identified: 91 diatoms, 47 dinoflagellates and 10 other flagellate morphotypes. Detailed electron microscopy analysis revealed three potentially toxic diatoms of Pseudo-nitzschia genus: P. calliantha, P. pseudodelicatissima and P. manii. The results of this work represent a valuable contribution to the knowledge of phytoplankton species composition and distribution relative to prevailing physico-chemical conditions in this poorly investigated transition zone.Velebitski i Paški kanal čine 40 km dug i 4-14 km širok sustav koji se proteže usporedno sa sjeveroistočnom obalom Jadranskog mora. Cilj ovog istraživanja je bio istražiti abundanciju, sastav i raspodjelu fitoplanktona duž sustava u jesenskom razdoblju. Uzorkovanje je obavljeno na 8 postaja u studenom 2008. Prostorna raspodjela fizikalno kemijskih parametara upućivala je na postojanje izrazitog horizontalnog termohalinog i trofičkog gradijenta. Od unutrašnjeg dijela Velebitskog kanala, koji je produžetak estuarija krške rijeke Zrmanje do vanjskog dijela Paškog kanala koji se spaja s otvorenim morem, raspon površinske temperature mora iznosio je 11.0 do 16.0 °C, a saliniteta 23.4 do 38.2. Koncentracije nutrijenata kretale su se u rasponu 0.001 - 0.1 μmol L-1 za fosfate, 0.85 - 7.0 μmol L-1 za otopljeni anorganski dušik i 0.3 - 15.4 μmol L-1 za silikate. Dijatomeje su prevladavale u fitoplanktonu s maksimalnom abundancijom u rasponu od 7.3 x 104 stanica L-1 (85% ukupnog fitoplanktona) na najviše oligotrofnim do 9.6 x 105 stanica L-1 (96% ukupnog fitoplanktona) na postajama s većom koncentracijom nutrijenata. Statistička analiza na osnovi bioloških i fizikalno kemijskih parametara podijelila je postaje u tri glavne grupe. Prva grupa predstavljala je južni dio Velebitskog kanala s većom koncentracijom nutrijenata i prevladavajućom vrstom Thalassionema nitzschioides. Druga grupa uključila je postaje iz središnjeg dijela Velebitskog kanala s nižim razinama nutrijenata i s prevladavajućom dijatomejom Bacteriastrum sp.. Treća grupa uključila je postaje u Paškom kanalu u kojima gotovo isključivo prevladava Bacteriastrum mannii sp. i prisutan je veći udio kokolitoforida. Ovaj rad također donosi prvi popis vrsta fitoplanktona prisutnih u ekstremno oligotrofnom području Velebitskog i Paškog kanala. Identificirano je 148 taksona od čega 91 dijatomeja, 47 dinoflagelata i 10 taksona raznih flagelata. Detaljna analiza pomoću elektronskog mikroskopa otkrila je tri vrste iz potencijalno toksičnog dijatomejskog roda Pseudo-nitzschia: P-n. calliantha, P-n. pseudodelicatissima i P-n. mannii. Rezultati ovog rada predstavljaju značajan doprinos poznavanju sastava i raspodjele fitoplanktona u odnosu na prevladavajuće fizikalno kemijske uvjete u ovom slabo istraženom tranzitnom području

BRIDGING FUNCTIONAL AND PHYLOGENETIC DIVERSITY OF MARINE HETEROTROPHIC PROTISTS VIA SINGLE-CELL TRANSCRIPTOMICS

The comprehensive description of unicellular heterotrophic protists is essential for understanding the functioning of marine ecosystems and defining evolutionary relationships within marine microbial communities. For that reason, new insights into the functional genes of key protists, such as ciliates and dinoflagellates, are needed to complement the increasing taxonomic complexity and bridge the gap between various eco-functional processes in the ocean. In this study, single-cell transcriptomic sequencing proved to be an efficient method to create a snapshot of expressed genes of unicellular heterotrophs. We sequenced 65 single-cell transcriptomes from 20 fresh field samples collected from Sub-Arctic and North Sea waters. These 13 ciliate and 52 dinoflagellate transcriptomes will generally contribute to a greater understanding of functional and evolutionary processes of these marine protists. Further, we generated multi-gene phylogenies of several dozen genes to unravel the relationships of these heterotrophic taxa to other dinoflagellates and ciliates, respectively. These approaches also helped to elucidate the evolution of functional genes and traits for these understudied essential groups. Additionally, the datasets were incorporated into our metatranscriptomic reference database to fill the gap (of approx. 50%) of genomic information of heterotrophic organisms and their functional processes. Overall, identifying the phylogenetic relationships and functional diversity of heterotrophic and mixotrophic protists will clarify paramount marine microbial food web processes and provide clues to the system's sensitivity to climate change

Cryptophyte bloom in a Mediterranean estuary: High abundance of Plagioselmis cf. prolonga in the Krka River estuary (eastern Adriatic Sea)

During the June 2010 survey of phytoplankton and physicochemical parameters in the Krka River estuary (eastern Adriatic Sea), a cryptophyte bloom was observed. High abundance of cryptophytes (maximum 7.9×106 cells l–1) and high concentrations of the class-specific biomarker pigment alloxanthine (maximum 2312 ng l–1) were detected in the surface layer and at the halocline in the lower reach of the estuary. Taxonomical analysis revealed that the blooming species was Plagioselmis cf. prolonga. Analysis of the environmental parameters in the estuary suggested that the bloom was supported by the slower river flow as well as the increased orthophosphate and ammonium concentrations. The first record of a cryptophyte bloom in the Krka River estuary may indicate that large-scale changes are taking place in the phytoplankton community. Such changes could have a major impact on the natural ecosystem dynamics and the mariculture production in the area

Ammonia as alternative future fuel

U ovom radu opisan je amonijak kao obična tvar te kao potencijalno buduće gorivo. Objašnjeni su razlozi njegove upotrebe u kontekstu pozitivnog utjecaja na okoliš te dekarbonizacije brodskog transporta. Opisani su načini skladištenja amonijaka i njegova dobivanja Haber-Boschovim postupkom. Prikazana je usporedba amonijaka s drugim gorivim te su navedene prednosti i nedostaci njegove upotrebe. Istraženi su načini njegova izgaranja, potencijalna poboljšanja i povećanja brzine izgaranja smjese amonijaka i zraka. Prikazana je njegova upotreba u gorivnim ćelijama te u MAN-ovom dvotaktnom motoru. Shematski je prikazan sustav goriva, a također je i proračunat sustav goriva prekooceanskog broda s pogonskim sustavom snage 10MW pri čemu je određen volumen dnevnog tanka, spremnika goriva, dimenzioniran je cjevovod te pumpa goriva i prikazana je ekonomska iskoristivost plovidbe broda na amonijak.This master's thesis describes ammonia as a common substance and as a potential future fuel. The reasons for its use in context of a positive impact on the environment and the decarbonization of ship transport are explained. Methods of ammonia storage and its production by the Haber-Bosch process are described in this thesis. A comparison of ammonia with other fuels is presented and the advantages and disadvantages of its use are stated. Ways of its combustion, potential improvements and increases in the combustion speed of the mixture of ammonia and air were investigated. Its use in fuel cells and in MAN's two stroke engine is shown. The fuel system is shown schematically and the fuel system of an ocean-going ship with a 10MW propulsion system is also calculated where the volume of the day tank is determined, fuel tank is determined, the pipeline and the fuel pump are dimensioned and the economic usability of the ship's navigation on ammonia is shown

The evolution of nuclear power plants

Nuklearna elektrana je postrojenje kojim se, uz pomoć kontroliranog procesa fisije, pri kojem se oslobađa velika količine energije, proizvodi električna energija. U reaktoru se oslobađa toplinska energija koja se upotrebljava pri proizvodnji pare koja pokreće turbinu spojenu na elektrogenerator. Ovisno o godini puštanja u pogon, nuklearne elektrane možemo podijeliti u četiri generacije. Prve dvije su se razvijale do kraja 20-og stoljeća, a ostale generacije su, ili će biti u pogonu do 2030. godine. Reaktore se može podijeliti na više različitih tipova s obzirom na vrstu goriva, moderator i rashladni medij. Najzastupljeniji su tlakovodni i kipući reaktori. Kipući reaktori rade na sličnom principu kao tlakovodni, ali u postrojenju nema parogeneratora jer se para postiže u samoj jezgri. Od reaktora prve i druge generacije bitno je još spomenuti teškovodne reaktore, reaktore hlađene plinom i reaktore hlađene tekućim metalom. Kroz godine nuklearne elektrane su napredovale s izvedbama reaktora i svojim karakteristikama u cijelosti koje se ogledaju u povećanju sigurnosti i smanjenju komponenata postrojenja. Nuklearne elektrane ne predstavljaju veliku opasnost po okoliš. Nove izvedbe su sve sigurnije, tj. imaju sve manju mogućnost oštećenja jezgre i emitiranja radioaktivnih čestica u okoliš.Nuclear power plant is a station which uses controlled fission process that generate big ammount od energy, to create electric energy. Thermal energy that's used in creating steam which powers the turbine connected to electrogenerator is released inside the reactor. Depending on the year of commisioning, we can divide nuclear power plants in four generations. First two were being developed until the end of 20th century, and the others are, and will be in use until 2030. Reactors can be divided in more different types considering fuel type, moderator and cooling medium. The most common are pressure reactors and boiling reactors. Boiling reactors work on the similar principle as pressure reactors, but without steam generator because the steam is generated inside the very core. From the first and second generation reactors it is important to mention high-flow reactors, gas-cooled reactors and liquid metal cooled reactors. Through the years nuclear power plants advances with reactor preformances and also characteristics in its entirety which can be seen in increasing security and reducing plant components. Nuclear power plants don't pose much threat to the environment. New designs are becoming even safer, ie. they have less possibility of core damage and radioactive particle emission to the environment

Phenotypic evolution and adaptive strategies in marine phytoplankton (Coccolithophores)

Coccolithophores are biogeochemically important marine algae that interact with the carbon cycle through photosynthesis (CO2 sink), calcification (CO2 source) and burial of carbon into oceanic sediments. The group is considered susceptible to the ongoing climate perturbations, in particular to ocean acidification, temperature increase and nutrient limitation. The aim of this thesis was to investigate the adaptation of coccolithophores to environmental change, with the focus on temperature stress and nutrient limitation. The research was conducted in frame of three approaches: experiments testing the physiological response of coccolithophore species Helicosphaera carteri and Coccolithus pelagicus to phosphorus limitation, field studies on coccolithophore life-cycles with a method comparison and an investigation of the phenotypic evolution of the coccolithophore genus Helicosphaera over the past 15 Ma. Experimental results show that the physiology and morphology of large coccolithophores are sensitive to phosphorus limitation, and that the adaptation to low-nutrient conditions can lead to a decrease in calcification rates. Field studies have contributed to our understanding of coccolithophore life cycles, revealing complex ecological patterns within the Mediterranean community which are seemingly regulated by seasonal, temperature-driven environment changes. In addition, the high-throughput sequencing (HTS) molecular method was shown to provide overall good representation of coccolithophore community composition. Finally, the study on Helicosphaera evolution showed that adaptation to decreasing CO2 in higher latitudes involved cell and coccolith size decrease, whereas the adaptation in tropical ecosystems also included a physiological decrease in calcification rates in response to nutrient limitation. This thesis advanced our understanding of coccolithophore adaptive strategies and will improve our predictions on the fate of the group under ongoing climate change