The bacterial community in coastal waters of northeastern Adriatic Sea was dominated by SAR11 and Sulfitobacter taxa throughout the year. The seasonal distribution of bacterioplankton taxa showed continual differences between surface (0 m) and bottom (27 m) layers. The surface assemblage was represented by Actinobacteria, Cyanobacteria, Alphaproteobacteria, and Gammaproteobacteria, while the bottom assemblage was made up of Bacteroidetes, Cyanobacteria and Alphaproteobacteria. As SAR11 was more dominant in the bottom layer, its appearance may be linked to northward transport of oligotrophic waters of higher salinity from the south. Gammaproteobacteria appeared only in the surface layer during summer, influenced by higher amounts of nutrients, brought in by the Po River. Synechococcus was the most abundant taxon at the genus level. Dominance of Synechococcus during the whole season agrees with its dominance in terms of abundance determined by flow cytometry, and confirms its utmost importance in the picoplankton community of this area. We found two different types of Synechococcus: one type with high similarity to Synechococcus CC9902, present in the surface and bottom layers, and another one similar to Synechococcus WH7803, present only in the surface layer. Oligotrophic conditions together with complex hydrological features of this area were reflected in diversification and dynamic shifts of surface and bottom assemblages.

12The importance of bacterial, phytoplankton and dissolved alkaline phosphatase 13 activity (APA) in the northern Adriatic was investigated during 2006. In upper waters total 14 APA increased from early spring (0.05-0.08 µmol l -1 h -1 ) to late spring (up to 4.64 µmol l -1 15 h -1 ) and remained relatively high during the summer (0.46-0.71 µmol l -1 h -1 ), due to an 16 increase in specific phytoplankton (up to 30 µmol µg C -1 h -1 ) and bacterial APA (up to 23 17 µmol µg C -1 h -1 ). Activity of free enzymes was not important. During late spring and 18 summer both communities exploited dissolved organic phosphorus although, taking into 19 account biomass, phytoplankton activity usually dominated over bacterial. In autumn an 20 extra P supply from deeper waters drastically reduced phytoplankton APA, though not 21 bacterial APA, in upper waters. Probably in these months bacteria degrading 22 phytoplankton produced organic matter were P limited. In deeper waters APA was low and 23 mainly due to the activity of free enzymes. 24

Bosak, Sunčica; Godrijan, Jelena; Šilović, Tina. Dynamics of the marine planktonic diatom family Chaetocerotaceae in a Mediterranean coastal zone // Estuarine, coastal and shelf science, 180 (2016) 69-81. ABSTRACT 13 The planktonic diatoms belonging to two genera Chaetoceros and Bacteriastrum, included 14 within the family Chaetocerotaceae, are ecologically important as they represent a constitutive 15 component of the phytoplankton in the coastal regions and are often among bloom-forming 16 taxa. We analysed the chaetocerotacean species composition and abundances in the coastal 17 area of northeastern Adriatic in a biweekly study conducted from September 2008 to October 18 2009 with the aim of investigating seasonal dynamics and species succession on the finer 19 temporal scale and determining the most important ecological factors influencing their 20 distribution. The study identified seven Chaetoceros and three Bacteriastrum species as major 21 phytoplankton components showing the clear annual succession and two types of blooms (one 22 species/multi species) governed by differing ecological conditions. Autumn bloom was 23 composed of 20 chaetocerotacean species with Chaetoceros contortus and C. vixvisibilis 24 alternating in dominance. Summer period was characterized by spreading of freshwater from 25 the Po River up to the eastern coast increasing availability of phosphate which triggered the 26 monospecific Chaetoceros vixvisibilis bloom. We explained the chaetocerotacean dominant 27 species succession pattern by the environmental parameters, with the temperature, salinity and 28 phosphate availability as most important factors driving the species seasonality.29 30 31 32 33 34 Highlights 35  First coherent investigation of temporal dynamics and species succession of 36 marine planktonic diatom family Chaetocerotaceae 37  Two types of blooms (one species/multi species) are governed by differing 38 ecological conditions 39  The succession pattern of dominant chaetocerotacean species was explained by 40 temperature, salinity and phosphate availability as the most important factors 41 driving the species seasonality 42 43 1. Introduction 44 The family Chaetocerotaceae Ralfs in Pritchard (1861) include cosmopolitan diatoms, 45 notably thriving in the phytoplankton of coastal regions (Rines and Hargraves, 1988), and 46 play an important role in neritic food webs and biogeochemical carbon and silica cycles. The 47 hallmarks of this family are setae, long and hollow silicate spine-like projections protruding 48 from the valve surface (Round et al., 1990). The strong and robust setae can irritate fish gills 49 and cause excess mucus secretion and damage, thus certain species have been characterized as 50 nuisance and harmful to fish and invertebrates (Hallegraeff et al., 2003; Smayda, 2006). 51Members of this family are important model species in not only in ecology and physiology, 52 but also in toxicology and nanomaterial studies (Nagao et al., 2010; Peng et al., 2011; 53 Osterholz et al., 2014). 54Cha...

Abstract. This paper documents the picoplankton community's response to changes in oceanographic conditions in the period between October 2011 and September 2012 at two stations belonging to the South Adriatic Pit (SAP). The recorded data include the community's abundance, composition, prokaryotic production rates and bacterial metabolic capacity. The sampling period included an intense sea cooling with formation of exceptional, record-breaking dense water. We documented an especially intense winter convection episode that completely diluted the core of Levantine intermediate waters (LIW) in a large area encompassing the SAP's center and its margin. During this convection event the whole picoplankton community had significantly higher abundances with a recorded picoeukaryotic peak at the SAP margin. In the post-convection phase in March, prokaryotic heterotrophic production strongly increased in the entire SAP area (up to 50 times; 456.8 nM C day−1). An autotrophic biomass increase (up to 5 times; 4.86 μg L−1) and a disruption of a close correspondence between prokaryotic heterotrophic biomass production and cell replication rates were observed only in the center of the SAP, which was not under the influence of LIW. At the SAP's margin such an effect was attenuated by LIW, since the waters affected by LIW were characterized by decreased concentrations of dissolved inorganic nitrogen, decreased autotrophic biomasses, and by increased bacterial biomass production balanced with cell replication rates as well as by the domination of Synechococcus among autotrophic picoplankton. The metabolic capacity was lowest in spring when autotrophic biomass largely increased, while the highest levels found in the pre-convection phase (October 2011) suggest that the system was more oligotrophic before than after the convection event. Furthermore, we showed that metabolic capacity is a trait of bacterial community independent of environmental conditions and tightly linked to cell replication and substrate availability. In contrast, the bacterial community composition appears to be strongly influenced by physico-chemical characteristics of waters (e.g., temperature and nutrients) and environmental forcing (e.g., convection and LIW). Our results showed that the two oceanographic phenomena of the Southern Adriatic, strongly relevant for the total production of the Adriatic Sea, winter convection and LIW intrusion, regulate the changes in picoplankton community structure and activities.

Fuks Dragica et all. Changes in the planktonic community structure related to trophic conditions: The case study of the northern Adriatic Sea Journal of marine systems, 96-97 (2012), 4; 95-102 Introduction 30One of the important aims of the community ecology is the understanding of 31 carbon flux through the trophic levels. There is evidence that the transfer of organic 32 carbon through the trophic levels differs between regions with diverse productivity. 33The plankton from unproductive regions is characterized by high relative 34 heterotrophic biomasses resulting in an inverted biomass pyramid, whereas the 35 plankton from productive areas is characterized by a smaller contribution of 36 heterotrophs and a broad autotrophic base (Gasol et al., 1997). The Northern Adriatic 37 is one of the most productive regions of the Mediterranean Sea at several trophic 38 levels, from phytoplankton to fish (Vollenweider et al., 1992). Particularly, high but 39 variable plankton standing crop and production was quantified off the Po River delta 40 3 and related to the spreading of its plume (Gilmartin and Revelante, 1981 (Revelante and Gilmartin, 1990), while the mesozooplankton by strictly neritic 45 copepod and cladoceran species (Fonda Umani 1996; Fonda Umani et al., 2005). 46Copepod nauplii of the smallest size fractions were revealed as the major mediators 47 of material transfer between primary producers and higher trophic levels (Lučić et al., 63Since the relative biomass distribution between heterotrophs and autotrophs is 64 regulated by nutrient supply (Duarte et al., 2000), the objectives of the study were to Material and methods 77Measurements were performed at three stations at the Po River delta -Rovinj 78 transect located in the northern Adriatic (Fig. 1) with CaCO 3 . In the laboratory, samples were sedimented until the original volume of 99 5 L was reduced to 10 mL, which took 72 hours (Kršinić, 1980). The organisms were 100 counted with an Olympus inverted microscope at magnifications of 100x and 400x. 101The microzooplankton was separated in two categories: ciliated protozoans 102(nonloricate ciliates and tintinnids), and metazoans (copepods nauplii, copepodites 103 and small adult copepods). Results 131From May to September chl a concentrations were related to the freshwater input. 132In absence of new freshwater input minimal chl a concentrations were observed in 133 the whole area (Fig. 2). In these months with "closed" circulation and stratified water (Fig. 2). Most often during the winter river waters did not influence the area, 144 as indicated by generally high surface salinity in these months. observed only in bottom waters (Fig. 4). In conditions of similar chl a values, larger 164 abundance of heterotrophic organisms was observed at the western stations, 165 especially in the upper parts of the water column (Fig. 4, 5). The difference in (Fig 4, 5). Maximal values were found at the surface 176 (chl a 2.12µg l -1 , HB 124 . 10 7 cell l -l , HF 1.6 . 10 6 cell l -l , ciliates 308 ind...