Contribution of Zooplankton Lipids to the Flux of Organic Matter in the Northern Adriatic Sea

Analyses of particulate material collected by sediment traps moored at a location in the northern Adriatic Sea in 1991 revealed the presence of zooplankton fatty acids, even though zooplankton and other \u27swimmers\u27 killed by the trap\u27s preservative were carefully removed. Laboratory experiments were conducted to (1) prove the existence of zooplankton lipids within fecal pellets, (2) exclude the possibility of incomplete separation of swimmers and other material as eventual contamination with polyunsaturated fatty acids in fecal pellets, (3) evaluate the importance of zooplankton lipids to mass flux and (4) reveal the mechanisms which lead to excretion of undigested organic matter, in this case polyunsaturated fatty acids. Our results show that the main source of fatty acids found in mass flux were zooplankton lipid droplets inside fecal pellets. The predominant fatty acids of zooplankton fecal pellets were saturated acid 16:0, monounsaturated acid 18:1 and polyunsaturated acid 22:6. Lipid composition of fecal pellets was compared with those of zooplankton and phytoplankton. Aliquots of collected fecal pellets were stained with Nile Red in order to visualize lipid droplets within fecal pellets

Fuentes potenciales de alimento en Glycymeris nummaria (Mollusca: Bivalvia) durante el ciclo anual a partir del análisis de ácidos graso

Seasonal changes of food sources were investigated by analysing the fatty acid profiles of digestive gland and muscle tissues of the naturally occurring clams Glycymeris nummaria in Mali Ston Bay, Croatia. Total lipids in the digestive gland and the adductor muscle showed parallel changes, with a maximum after the main spawning event in September. In the digestive gland saturated fatty acids were highly dominant (up to 82%), indicating detritus as the main food source for this species. This type of food prevailed during the autumn/winter period, in contrast to the spring/summer period when detritus was enriched with phyto- and, to a lesser extent, zooplankton. Fatty acid composition of muscles indicated highly efficient utilization of ingested food through significant retention of polyunsaturated fatty acid from the clams’ diet during the entire period investigated.Se han investigado los cambios estacionales en las fuentes de alimentación de poblaciones naturales del bivalvo Glycymeris nummaria en la bahía Mali Ston (Croacia) por medio del análisis de los perfiles de ácidos grasos de la glándula digestiva y del tejido muscular. El total de lípidos tanto de la glándula digestiva como en el músculo aductor mostró cambios similares después del principal evento de freza (septiembre). En la glándula digestiva los ácidos grasos saturados fueron altamente dominantes (hasta el 82%), lo que señala a los detritos como principal fuente de alimentación de esta especie. Este tipo de alimento prevalece durante el otoño/invierno, mientras que en primavera/verano la alimentación se complementa con fitoplancton y, en menor medida, con zooplancton. La composición de ácidos grasos en el tejido muscular indica una alta eficiencia en la utilización del alimento ingerido mediante la retención de los ácidos grasos poliinsaturados (PUFA) de la dieta durante todo el periodo investigado

Prilagodbene promjene u staničnim masnim kiselinama bakterija izdvojenim iz sjevernog Jadrana– odgovor na trofičke razlike

The adaptational changes in cellular fatty acids and morphology of γ-Proteobacteria belonging to different genera (Vibrio, halomonas, Pseudoalteromonas) isolated from northern Adriatic waters and cultured in four media (Marine Broth, R2 Broth and tenfold dilutions of both) were investigated. The bacterial strains with identical 16S rRNA sequences isolated from different waters used differ- ent mechanisms, or different extent of the same mechanism, to adapt their growth in equal culture media. In contrast, a similar growth strategy in each of the used cultures was employed by different strains isolated from the same water body. Divergence in nutrient quality and requirement in cul- tures from that presented in the bacterias’ natural environment induced important changes in cel- lular fatty acids; (i) unsaturation, (ii) cis to trans isomerisation, (iii) chain elongation (iv) branching and/or morphology (Winnie-the-Pooh effect) or even cell division blocking. The results strongly suggest that growth and the appropriate cellular response of bacteria in culture is predetermined by nutritional conditions in their true environment and can be useful for interpretation of trophic differences between proximate environments.Istražene su prilagodbene promjene u staničnim masnim kiselinama i morfologiji γ-Proteobacteria koje pripadaju različitim svojtama; Vibrio, Halomonas, Pseudoalteromonas; izoliranih iz sjevernog Jadrana i uzgojenim na četiri hranjive podloge (Marine Broth, R2 Broth i deseterostruko razrjeđenje od oba). Sojevi s jednakim 16S rRNK sekvencama izolirani iz različitih vodenih masa koristili su različite mehanizme ili jedan mehanizam različitog intenziteta kako bi prilagodili rast u istom mediju uzgoja. Nasuprot tome, sličnu strategiju rasta su koristili različiti sojevi izolirani iz iste vodene mase. Odstupanje u kvaliteti hranjiva i potreba u kulturi od onih prisutnih u prirodnom okolišu izaziva važne promjene u staničnim masnim kiselinama (i) nezasićenost, (ii) cis/trans izomerizacija, (iii) produljenje acilnih lanaca, (iv) razgranavanje acilnih lanaca ili/i promjene morfologije stanica (Winnie-The-Pooh učinak), te zaustavljanje dijeljenja stanica. Rezultati upućuju da su rast i odgovarajući stanični odgovor bakterija u kulturi unaprijed određeni stanjem hranjiva u prirodnom okolišu, te mogu poslužiti za interpretaciju trofičkih razlika između bliskih okoliša

Ecological Importance of Alkaline Phosphatase Activity in Changing Marine Environmental Conditions

The effects of changing hydrological and climatic conditions on the dynamics of phosphorus (P) were studied in the Northern Adriatic Sea (NA), a coastal system currently affected by these changes. P limitation is one of the key stresses in the NA and it is a globally important phenomenon in aquatic ecosystems. Therefore, the response to P stress by inducing alkaline phosphatase activity (APA) was studied in characteristic water types in the NA, formed by the changing freshwater input in different thermic conditions. APA was important in providing P for microbial growth in upper waters dominated by assimilation during the warmer part of the year in stratified conditions. Contrarily, APA was not important during mixing in the colder part of the year, as well as in waters dominated by regeneration. In waters influenced by freshwater, temperature had no effect on APA, while in high-salinity waters, temperature was an important factor for APA increase. The highest APA occurred during riverine nutrients supply, indicating that the alteration of anthropogenic nutrient loads might strongly change P status in this coastal system. Furthermore, predicted increases in winter sea temperature and summer Po River discharge could delay the water column mixing, prolonging periods of P limitation