Changes in the planktonic community structure related to trophic conditions: The case study of the northern Adriatic Sea

Abstract

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...

Effects of fish farming on microbial planktonic communities in the middle Adriatic sea

“…On the other hand, nitrate concentrations were higher than in the aforementioned studies implying different structure of the nutrient pool between these two basins. The concentrations of measured nutrients at the Farm are comparable with the values commonly found in the Adriatic Sea for the locations that are not under the aquaculture influence (Ivančić, Fuks, Najdek, Blažina, Devescovi, Šilović, Paliaga & Orlić ; Fuks, Ivančić, Najdek, Lučić, Njire, Godrijan, Marić, Šilović, Paliaga, Blažina, Precali & Orlić ; Šantić, Šestanović, Šolić, Krstulović, Kušpilić, Ordulj & Ninčević ). Thus, the general assumption that continuous nutrient loadings from fish farms could have serious effects on natural occurring nutrient concentrations, particularly in the oligotrophic environment does not appear to be the case here.…”

The carbon budget in the northern Adriatic Sea, a winter case study

“…Therefore, the carbon budget of this period can be considered as a suitable baseline in order to (i) verify the possibility of the northern Adriatic Sea acting as a “continental shelf pump” for CO 2 sequestration, from the combined effect of solubility and biological pumps, and (ii) define the degree of eutrophication that sometimes occurs during spring‐summer. Among the few studies about this topic, some researches of the microbial C biogeochemistry showed different trophic regimes in different areas and seasons [ Giani et al ., ; La Ferla et al ., , , ; Fonda Umani et al ., ; Fuks et al ., ]. During the PRISMA 2 project (1996–1998), the trophic balance appeared to move toward autotrophy in winter when a positive C budget resulted.…”

“…Fuks et al . [] found that, both under oligotrophic conditions and in eutrophic events, chl‐ a ‐derived biomass in the northern Adriatic Sea was always higher than the prokaryotic one, the two being almost equal only at surface during oligotrophic conditions. In the Gulf of Trieste (the northeastern part of northern Adriatic Sea), Fonda Umani et al .…”

The Impact of a Fish Cannery Wastewater Discharge on the Bacterial Community Structure and Sanitary Conditions of Marine Coastal Sediments

“…A high abundance of prokaryotes and faecal indicator bacteria was present in these waters. Such concentrations were more than twenty times higher than at an unpolluted referent station [40,41]. The ratio of FC/FS ~1 indicated the prevalence of a non-human source for these bacteria [42] since the cannery effluent contained exclusively fish remains and waste from fish processing.…”