Search

Veličina tijela i temperatura utječu na brojne značajke živog svijeta. Temperatura utječe na brzine svih kemijskih procesa koji se događaju u organizmu, a veličina utječe na izgled i funkcioniranje organizama, dakle utječe na njihovu evolucijsku uspješnost. Je li dobro biti velik? Vodi li globalno zatopljenje prema smanjenju veličine tijela? Zašto je toplije manje? Zašto je toplije ponekad bolje? Kako se kontradiktorni utjecaji klimatskih promjena na živi svijet mogu objasniti? Ekolozi se općenito slažu oko tri univerzalna ekološka odgovora organizama na globalno zatopljenje, a to su (1) pomaci u prostornoj raspodjeli populacija i vrsta (prvenstveno pomaci prema višim geografskim širinama i većim nadmorskim visinama), (2) promjene u početku i trajanju važnih procesa u životnom ciklusu organizama (najčešće njihov raniji početak i duže trajanje), te (3) smanjenje veličine tijela. Svi ovi odgovori povećavaju prostornu i vremensku neusklađenost međusobno ovisnih vrsta i vode k njihovom nestanku i smanjenju biološke raznolikosti na Zemlji, što će ozbiljno ugroziti funkcije ekosustava o kojima ovisi život na Zemlji. Mogu li se klimatske promjene zaustaviti ili se, poput snježne lavine, kada se jednom pokrenu moraju odviti do kraja? Može li ljudska mudrost odnijeti pobjedu nad pohlepom i trkom za profitom i tako smanjiti posljedice klimatskih promjena koje će pogoditi buduće naraštaje.

Institut za oceanografiju i ribarstvo u Splitu osnovan je 1930. godine. Članak donosi povijest ovog Instituta, od odluke za njegovo osnivanje, gradnje zgrade i njenog arhitektonskog značaja, te aktivnosti Instituta vezane za znanstvena istraživanja, stručne poslove, edukaciju, bibliotekarstvo, izdavaštvo, te mnoge zanimljivosti iz njegove bogate povijesti

It is well known that anthropogenic impacts have significant effects on marine communities. One of the consequences is the increased input of anthropogenic substances into the coastal zone which affects the fragile marine environment through various mechanisms, including high inorganic nutrient loads, organic compounds, sediments and the uptake of heavy metals. Recognition of port waters in coastal ecosystem monitoring programs is increasing as economically important infrastructure is embedded in the coastal environment and its management needs to be considered. General knowledge of the ongoing processes in these waters, which play a strategic role in the coastal environment needs to be acquired, considering abiotic and biotic factors, to implement sustainable development (Blue Growth) in port areas. Typically, the regulation implemented in ports and adjacent areas refers to chemical emissions and the consequent pollution of water and sediments together with sanitary aspects related to microbial pathogens, as basic controls to protect human health. Physicochemical and biotic parameters in the water column are subject to higher variability on shorter temporal scales compared to benthic parameters, related to seasonal changes and inflow/outflow from associated marine and inland waters. Planktonic taxa respond rapidly to environmental perturbations, although they have rarely been considered as descriptors of marine ecological quality. Particularly, bacterioplankton abundance and activity have been recognized as sensitive sentinels of environmental change. From an ecological perspective, bacterioplankton, phytoplankton and zooplankton are the most important planktonic components in the water column in terms of abundance, biomass, diversity, trophic networks and ecosystem services provided. Marine microbes are a diverse group of organisms including bacteria, archaea and eukaryotic protists that drive most biogeochemical cycles and play a central role in the transformation and recycling of carbon and energy in the marine environment. Bacteria dominate the abundance, diversity and metabolic activity of the ocean. Autotrophic picoplankton forms the base of the trophic food chain, while heterotrophic bacteria (HB) use almost exclusively the dissolved fraction of primary production and act as decomposers and transformers of compounds into forms suitable for primary producers. Heterotrophic nanoflagellates (HNF) participate in the material and energy flow towards higher trophic levels in the ecosystem through bacterial predation. Studies on inhabiting biota in ports are scarce. The present study aimed to determine the dynamics of the picoplankton community to gain insights into the ecology of two Croatian ports, Špinut and Strožanac. We hypothesized that there would be a difference in the bacterioplankton counts between the investigated stations and the control points in the two ports. Maritime Sports Society Špinut, located in the north of Split, has a total of 950 berths, 350 of which are for boats less than 6 m long. Many freshwater springs influence the water temperature and salinity in winter and spring. Sport Fishing Society Strožanac, with 330 berths for various boat sizes, is located near the beach in Podstrana and the mouth of the river Žrnovnica. Submarine freshwater springs also influence the water temperature and salinity in this area. In this study, sampling campaigns were conducted in the surface layer (30 cm below the surface) monthly for a period from April 2019 to January 2021. Flow cytometric counts of heterotrophic and autotrophic picoplankton, including the cyanobacteria Synechococcus (Syn) and Prochlorococcus (Pro) and picoeukaryotes (PE), were conducted. The Gasol model was used to determine grazing on HB by HNF, i.e., the flux of bacterial biomass to higher trophic levels. To test our hypothesis, we used the paired-samples t-test on HB. In general, abundances of picoplankton were more evenly distributed in Špinut than in Strožanac port throughout the investigated period. Maximum values in both ports were higher in Strožanac, except for HB whose values were similar (1.7 ᵡ 106 cell mL-1) and HNF, whose values were an order of magnitude higher in Špinut (23.85 ᵡ 103 cell mL-1 in April 2020). However, the median values were higher in Špinut than in Strožanac, except for Syn. This indicates that both investigated ports are not under anthropogenic pressure as the values of HB abundances rarely exceed 106 cell mL-1 (median 0.3 and 0.4 ᵡ 106 cell mL-1), which is a limit for eutrophication. The Gasol model showed that HNF grazed mainly on HB during the studied period with some exceptions. Specifically, HNF was “top-down” predated in Špinut partly in winter 2020 and autumn and in Strožanac partly in winter 2020 and summer, while HB was controlled by some other factors at that time. Carbon stored in bacterial biomass is thus transferred to higher trophic levels, which could further enhance the early developmental stages of pelagic fish. A paired t-test revealed a statistically significant difference between the studied and control points in Špinut port (P≤0.05) as predicted. Meanwhile, there was no statistically significant difference between two out of six studied points and the control point in Strožanac (P

Bathing water quality is crucial to prevent the health risks associated with bathing in coastal and inland bathing waters. As bathing water quality has been identified as one of the most important reasons for tourists' choice of destination, it is an important factor for island and coastal communities that depend on coastal tourism. Bathing water management in the European Union (EU) is regulated by Bathing Water Directive (BWD) 2006/7/ EC. The purpose of the BWD is to preserve, protect and improve the quality of the environment and to protect human health. The BWD sets the guidelines for monitoring, quality assessment, classification and quality status of bathing waters, as well as providing information to the public. Bathing water assessment is based on the levels of two fecal indicator bacteria (FIB), Escherichia coli and intestinal enterococci. According to the BWD, the final assessment is based on bathing water quality data sets compiled for this bathing season and the three previous bathing seasons. The bathing water quality datasets used for the final assessment always include at least 16 samples (based on an annual number of four samples) or 12 samples in the case of a bathing water located in a region with specific geographical restrictions. Since most water quality exceedances are single-day events, there is only a small chance (5%) of detection at such a low sampling frequency, even at the most frequently contaminated sites. This results in a significant misclassification of 15- 20% of bathing water sites. Therefore, estimating compliance based on such a small number of bathing water samples is unlikely to fulfill the main purpose of Bathing Water Directive, which is to protect public health, as too many poor quality beaches may be classified in the better category. Although the number of samples per bathing season is much higher than four in all Member States, the World Health Organization (WHO) in "WHO recommendations on scientific, analytical and epidemiological developments relevant to the parameters for bathing water quality in the Bathing Water Directive (2006/7/ EC)" (2018) recommends a further increase to 20 samples per season (80 data for the final assessment). This would certainly contribute to the protection of human health, but could also lead to an additional financial burden and technical difficulties for many Member States. Furthermore, it is questionable whether it is justified to increase the number of samples at sites classified as "excellent" over a longer period of time. In this study, we investigated the effect of sampling frequency on coastal water quality assessment. The study was conducted during the 2021 bathing season in 5 areas along the coast of Croatian Adriatic. A total of 27 bathing sites were included in the study, of which 14 bathing sites were rated as "excellent" over a longer period of time, and 13 bathing sites with variations in water quality. Samples were taken weekly at all bathing sites by official laboratories conducting official monitoring and by the Institute of Oceanography and Fisheries, which conducted sampling in Kaštela Bay. Both fecal indicator bacteria, E. coli and intestinal enterococci, were determined using the membrane filtration method, ISO 7899-2:2000 for intestinal enterococci and the temperature modified method ISO 9308-1:2014 for E. coli. All FIB counts were converted to log10 values and processed in accordance with Annex II of the BWD. Of the total 13 bathing sites with quality variation, seven had the same quality regardless of whether sampling was every two weeks or every week (three excellent, two good and two poor). At five bathing sites, water quality was poorer when sampling was weekly. At two sites the quality changed from excellent to good and at three from good to poor. All 14 excellent quality bathing sites had the same water quality regardless of sampling frequency (13 excellent and one poor). Based on the preliminary results, it appears that increasing the sampling frequency at bathing sites with variable water quality would improve the health protection of bathers. There does not appear to be any reason to increase the number of samples at sites that have been classified as "excellent" over a longer period of time.

Ekologija u brojkama daje pregled klasičnih ekoloških modela kojima je zajednički nazivnik konzervacijska biologija/ekologija, odnosno ekološki principi na kojima se temelje promišljanja o strategijama zaštite vrsta, iskorištavanih populacija, staništa, ekosustava i krajobraza, te održivog upravljanja prirodnim resursima. Ovako koncipirana knjiga namijenjena je studentima i znanstvenicima, posebice onima koji se bave problemima kao što su zaštita vrsta i staništa, kontrola štetnih vrsta, gospodarenje živim resursima u ribarstvu, lovstvu, šumarstvu i sl. Predstavljeni modeli u pravilu imaju heurističku prirodu i njihova glavna uloga je edukacijska budući da predstavljaju moćan alat za bolje razumijevanje ekoloških procesa, te mogu biti poticajni za osmišljavanje istraživanja i definiranje novih problema. Knjiga pokriva široki spektar problema poput populacijskog rasta ; strukture populacija temeljene na starosti i stadijima razvitka ; definiranje reproduktivne vrijednosti, osjetljivosti i elastičnosti populacija koje omogućavaju donošenje važnih konzervacijskih odluka (koji dio populacije izlovljavati a da se ne ugrozi njen opstanak, koji dio populacije eliminirati s ciljem što boljeg suzbijanja štetočina ili kakvu strukturu populacije unijeti u novo stanište s ciljem da se populacija što prije poveća) ; koje mjere zaštite koristiti u gospodarenju populacijama koje se izlovljavaju ; kako procijeniti vjerojatnost preživljavanje dane populacije kroz određeno vremensko razdoblje, te brzinu i raspone širenja populacije ; kako utvrditi ključne faktore koji reguliraju promjene veličine populacije ; koja je uloga sržnih i rubnih staništa u regulaciji ukupne populacije i koje su ekološke zamke ; interakcije između populacija koje uključuju kompeticiju, predaciju, odnos domaćina i parazitoida, kao i model infekcije (danas aktualna tema zbog epidemije Covidom 19) ; o čemu ovisi optimalan izvor hrane ili plijena kod konzumenata ; o čemu ovisi dinamika metapopulacija ; kako odrediti širinu ekološke niše i preklapanje niša između različitih vrsta ; o čemu ovisi proces naseljavanja organizama u pojedina staništa ; kako veličine staništa i njihove međusobne udaljenosti utječu na ravnotežni broj vrsta (biološku raznolikost) ; koja je optimalna veličina uzorka za prihvatljivo dobru procjenu broja vrsta ; kako prognozirati vremenske promjene u sastavu vrsta u zajednici (sukcesije) ; kako odrediti prioritetne vrste i staništa za zaštitu (trijaža) ; o čemu treba voditi računa prilikom oblikovanja rezervata i zaštićenih područja ; kako intervencije u prirodnim staništima utječu na rasprostranjivanje vrsta i odvijanje njihovih životnih ciklusa. Sastavni dio knjige su 34 interaktivna modela koja korisniku omogućavaju samostalno istraživanje ekoloških procesa koje ovi modeli tretiraju, mijenjanje varijabli modela i opažanje efekata tih promjena na rezultatima modela (rezultati su uvijek prikazani grafički što olakšava njihovo praćenje), što će dodatno pomoći boljem razumijevanju ekoloških koncepata i procesa.

Responsible managing of marine ports in the Adriatic Sea is of utmost importance to address environmental issues. Most of these ports are small ports, supporting different activities such as boat services, fishing, sports, tourism and recreation. They play an important role in the community, not only economic but also social and environmental. As places where a large number of different activities meet, that can potentially have a negative impact on the environment, thus coordinated and responsible management is very important. A relatively large number of ports and port berths in two countries with the longest Adriatic coast, Italy and Croatia, combined with growing nautical tourism, makes this semi-closed sea very vulnerable to potential negative effect to its well-preserved environment. Microbiological contamination is just one of the possible consequences of irresponsible management of ports and boats they host and service. Although the microbiological quality of seawater in ports is not regulated by legislation, the possibility of introducing periodic or regular controls should be considered for several reasons: • This would help the local authorities and community to have an insight into how the port owner/concessionaire manages the port, • This would help the port owner/concessionaire to have an insight into whether port users are behaving responsibly, • This would help concessionaires of neighbouring beaches to ensure better protection of bathers’ health. To assess the potential impact of small ports on the microbiological quality of seawater in the port themselves and adjacent areas, we established the monitoring program in two small ports (marinas) in the area of Split, marina Špinut and marina Strožanac. Marina Špinut is located in the north of Split, under the hill of Marjan and next to the protected forest park Marjan. Marina has about 950 berths of which 350 for small boats less than 6 m, and the remaining for boats 6-15 m. Due to its location in semi-closed Kaštela bay and the proximity to adjacent beach Prva voda, the marina presents a potential risk for pollution of the area. Marina Strožanac is located in the south of Podstrana, next to the mouth of the river Žrnovnica. Marina has approximately 320 berths for different boat sizes. Since on both sides of the marina there are very popular and frequented public beaches, it is very important to monitor its potential negative impact on these beaches. Monitoring was carried out for two years, from April 2019 to February 2021. Sampling was organized once a month by collecting seawater samples for the determination of indicator bacteria, Escherichia coli and intestinal enterococci. Both indicator bacteria were determined by membrane filtration method, ISO 7899-2:2000 for intestinal enterococci and alternative, temperature modified ISO 9308-1:2014 method for E. coli. All samples were collected from 30 cm depth, at 6 sampling sites in both marinas, with one additional reference site at both areas. At the beach next to the marina Špinut and at both beaches (western and eastern) next to the marina Strožanac two sampling sites per beach were also included in monitoring to assess the potential effect of marina water on the beach water quality. Additionally, we analysed riverine water to assess potential faecal material load from Žrnovnica River. Since there are no legal criteria and standards for water quality in marinas, water quality was assessed following Croatian national regulation for coastal bathing water quality, using 90th and 95th percentile values of both indicator bacteria. When analysing the data obtained during two bathing seasons (May-September), all sites in the marina Špinut were of excellent quality. When included the data obtained during the whole year, five of six sites were excellent and one site was of good quality. No negative impact of the marina to the adjacent beach and area was recorded. Seawater quality in the marina Strožanac was excellent at five and good at one site during the bathing season. When included the data obtained during the whole year, four of six sites were excellent and two sites were of good quality. Seawater quality at two sites at the western beach, which is between the marina and the mouth of river Žrnovnica, was poor, both during the season and throughout the year. By analysing riverine water, the river was confirmed as the main source of faecal contamination of the area. The additional source of faecal material contributing to the contamination of the water is seagull droppings since huge numbers of seagulls gather at the area of the mouth of the river. As a result, no negative impact of the marina on the surrounding area was recorded, but on the contrary, the water from the river and river mouth had a negative impact on the water in the marina and the beach between the river mouth and marina. Thanks to the favourable direction of sea currents, no negative impact of contaminated water on the quality of bathing water at the eastern beach was found. Two monitored marinas in the Split area showed at least good quality of seawater, with a dominant number of sites with excellent quality. Anyhow, seawater in both marinas met the set requirements, to be of at least good quality.

Knjiga se na popularan način bavi odnosom između živog svijeta i neživog okoliša, utjecajem ekoloških faktora na živi svijet, te prilagodbama koje su organizmi razvili kako bi opstali u svojem okolišu.

The presence and spatial patterns of aerobic anoxygenic phototrophs were investigated, for the first time, in the Adriatic Sea. Also, the spatial patterns of the whole picoplankton community as well as the environmental factors that potentially influence these patterns were highlighted. Aerobic anoxygenic phototrophs abundances ranged from 10 x103 to 240 x 103 cells mL-1 and their proportion in total bacteria abundances ranged from 2.49 to 19.89%. These values are in the upper range of aerobic anoxygenic phototrophs abundances observed in marine environments. Aerobic anoxygenic phototrophs seem to be more abundant in mesotrophic coastal and estuarine waters than in the oligotrophic open sea implying their clear preference for higher trophic environments. Multivariate analyses proved that environmental factors influenced the picoplankton community interdependently. Chlorophyll a was the main driving factor for the picoplankton community, accounting for 33.3% of picoplankton community variance, followed by NO2 (17.9% of variance explained) and temperature (14.2% of variance explained). Chlorophyll a showed stronger correlation with aerobic anoxygenic phototrophs, non-pigmented bacteria and picoeukaryotes than with cyanobacteria. Abundance of cyanobacteria was more correlated to salinity and the N:P ratio than to nutrient concentrations.

Viruses are the most abundant and ubiquitous component of marine microbial plankton. To understand their dynamics, experiments on viral production, viral decay, and the percentage of lytic and lysogenic bacterial cells among the total number of bacterial cells were carried out at two stations in trophically different areas. Additionally, we gave the insight of the nutrient enrichment in the studied area with dissolved organic matter by viral lysis. Viral production was higher at the coastal station (0.75 ± 0.44 × 106 vlp mL-1 h-1) than at the open-sea station (0.49 ± 0.26 × 106 vlp mL-1 h- 1). Viral decay rates were also higher at the coastal sea station (0.25 ± 0.08 × 106 vlp mL-1 h-1) than in the open-sea station (0.14 ± 0.03 × 106 vlp mL-1 h-1), and were partially responsible for the reduction in produced viruses at both investigated stations (43.15 ± 25.19% at the coastal and 36.34 ± 21.91% at the open-sea station). The percentage of lysogenic bacteria was lower than that of lytic bacteria, which indicates the prevalence of the lytic cycle at both stations. Viruses had a significant influence on the mortality of bacterial cells in the coastal (78.81 ± 31.54%), and open-sea station (63.75 ± 8.80%), and thus contributed to the restoration of dissolved organic carbon, nitrogen and phosphorus into the microbial loop. All the abovementioned suggest that viruses are important part of the microbial food web and are an extremely important factor in the control of bacterial populations within the study area.

Along the eastern Adriatic coast sea surface temperature (SST) increased by an average of 1.03 °C during the period from 1979 to 2015, while in the recent period, starting from 2008, a strong upward almost linear trend of 0.013 °C/month was noted. During this period, SST increased by 1.25 oC. In the present study, Self-Organizing Map (SOM) procedure was used in analyzing time series (1997-2015) of a number of microbial parameters at two stations with different trophic status in the central Adriatic Sea. The rise in temperature was associated with: (1) the increasing importance of microbial heterotrophic activities and (2) the increasing importance of autotrophic picoplankton (APP) in the MFW. The temperature increase was accompanied with increase of bacterial growth, bacterial biomass turnover, bacterial predator abundances (particularly HNF) and grazing on bacteria, suggesting strong top-down control and increase in the proportion of bacterial carbon channelled to higher trophic levels. Simultaneously, autotrophic picoplankton (APP) biomass (including Synechococcus, Prochlorococcus and picoeukaryotes) significantly increased with temperature, suggesting that APP have a great potential as an additional carbon biomass that can be channelled towards higher levels in the warming conditions.

The new Bathing Water Directive (2006/7/EC) specifies two reference methods for the enumeration of E. coli in bathing water samples: ISO 9308-3 (miniaturized most probable number method), and ISO 9308-1 (membrane filtration method ) which was applied on the Croatian Adriatic coast from 2009 to 2014. Due to the low selectivity of Chromogenic coliform agar, a revised edition of ISO 9308-1 (2014) does not include the matrix of surface water in its scope, thus questioning the use of this method in the monitoring of bathing water quality. To reduce the growth of background bacterial flora and extend the scope to coastal bathing water, we modified reference method by changing the incubation temperature to 44 °C after the 4-hour resuscitation period at 37 °C. Reference method, ISO EN 9308-1:2014 against alternative, temperature modified ISO EN 9308-1:2014 method was compared according to ISO 17994:2014. The study area covered the entire Croatian Adriatic coast. Eight laboratories participated in the study, with more than 430 of paired data collected from more than 100 sampling sites. Increased incubation temperature significantly suppressed the growth of thermo-intolerant bacteria, including thermo-intolerant coliform bacteria. The reduction of non-E. coli coliforms was 47 %, while the reduction of all non-E. coli bacteria was 90 %. This made the reading of the plates significantly easier and faster. Based on the results of equivalence testing and criteria set by ISO 17994:2014, the methods were evaluated as “not different”, allowing the use of the alternative method for enumerating E. coli in coastal waters.

Aerobic anoxygenic phototrophs (AAP’s) have drawn much attention as they use carbon to sustain their metabolism and growth, but can derive a portion of their energy requirements by harvesting light using pigment bacteriochlorophyll a. Typically they account for 1-7% of total bacteria in the euphotic zones of the world’s oceans. Infrared epifluorescence microscopy was used to determine distribution of AAP’s along a trophic and vertical gradient in central Adriatic Sea during April and June 2016. AAP abundances ranged from 0.44 to 23.45 x 104 cells mL-1, with highest values on the stations with riverine influence. In general, the abundances decreased with depth. The proportion of AAP’s in total heterotrophic bacteria ranged from 6.84% in June to 13.03%. in April. Generally, AAP cell length was higher during warmer period, but the highest value was measured in colder period. Biomass contribution of AAP’s increased distinctly along the trophic gradient. In this survey AAP’s average biomass ranged from 4.38 to 31.85 µgCL-1. However, in our previous studies AAP’s were overlooked when calculating heterotrophic biomass. We observed that AAP bacteria thrive better in warmer period and also in more eutrophic areas, which suggests positive effects of temperature and nutrients as influencing factors in the Adriatic Sea. The data from our survey indicate an important contribution of AAP’s to carbon flow through microbial food web. In addition, the data allow preferably more accurate estimation of carbon flow through heterotrophic bacteria in the Adriatic Sea.

Planktonic ciliates, as well as the entire microzooplankton size-fraction represent the important components of the planktonic food webs, characterised by high biomass and intensive population dynamics. Due to their ability to adapt rapidly to ecosystem changes, small-sized zooplankton can act as good indicators of the marine ecosystems trophic state. After the activation of new modern sewage system in the eastern part of Kaštela Bay in November 2004, the potential changes in microzooplankton community composition, quantitative structure and seasonal variability were studied for more than a decade. Samples were collected seasonally during three periods: before (2001-2004), after (2005-2008) and ten years after the activation of new sewage system (2015-2017). The changes were best reflected in nonloricate and tintinnid ciliates, evident in the considerably reduced variability of their abundances and increased tintinnid biodiversity in the period after 2004. However, the absence of ciliate summer peaks and reduction of average abundances were statistically significant only at the larger time scale (ten years after). This indicated that apart from the changed trophic state, other environmental parameters affected the microzooplankton community in the period 2015-2017. Changes in seasonal dynamics of the target microzooplankton groups, particularly of ciliates, were confirmed by the Self Organising Map analysis. Further multi-annual investigations (from 2001 onwards) of the trophic relationships within the planktonic food web and the assessment of importance of abiotic parameters are needed for better understanding of the small- sized zooplankton response to environmental changes in this enclosed coastal location.

Ciliates represent the important component of the microbial food web, characterised by high biomass and intensive population dynamics, which enables them to adapt rapidly to ecosystem changes. Beside the changes in the community composition and trophic relationships this study also investigated the impact of temperature rise on microbial carbon fluxes in the experimental conditions. Dilution experiments were used for simultaneous estimations of protozoan grazing on picoplankton (bacteria, Prochlorococcus, Synechococcus and picoeukaryotes) under in situ and 3°C above in situ temperature. Picoplankton mortality was primarily caused by predation, especially in cold season, while viral lysis was of less intensity. The contribution of heterotrophic nanoflagellates to total grazing on picoplankton was higher than contribution of ciliates. However, direct ciliate grazing on Prochlorococcus and Synechococcus exceeded heterotrophic nanoflagellates grazing in most cases. Ciliates satisfied their carbon demand dominantly through the grazing on heterotrophic nanoflagellates and bacteria, and the role of autotrophic picoplankton as their prey increased significantly in the cold months. Differences in the pray composition were related to the ciliate community composition and the size categories of ciliate cells. Under the warm condition, the amount of picoplankton biomass transferred to protozoan predators exceeded the lysed biomass. The relative contribution of these loss factors for microbial mortality is crucial for a better understanding of the carbon fluxes in marine environments, suggesting that global warming could further increase picoplankton carbon flow toward higher trophic levels in the Adriatic Sea, which consequently affects the ecology of microbial food webs and functioning of the marine ecosystem.

Knjiga obrađuje problematiku ekologije najviših sustava ekološke hijerarhije - zajednice i ekosustava. Obrađuje se problematika strukture i razvitka zajednice, ekološke niše, koncepta biološke raznolikosti, trofičke strukture ekosustava, protoka energije i kruženja elemenata, regeneracije hranjiva, te regulacije funkcija ekosustava.

Viruses are an important and dynamic component of the marine microbial community. They are shaping microbial populations by lysing the host cells and thus are changing the biogeochemical nutrient cycling. The rise of sea surface temperature caused by the global warming could have a significant effect on viral population and their interaction with the marine microbial community. This could affect the way carbon is exported through the microbial food network. Modified laboratory dilution experiments that allow estimates of viral lysis on marine picoplankton (bacteria, Prochlorococcus, Synechococcus, picoeukaryotes) under in situ and 3°C above in situ temperatures were performed at seasonal scale. Viral lysis removed 14-94% day-1 of bacterial standing stock, 3-135% day-1 of Prochlorococcus standing stock, 0.9-30% day-1 of Synechococcus standing stock, and 0.2-17% day-1 of picoeukaryote standing stock. Rates of viral lysis on picoplankton were more pronounced in the warmer months (July and November), particularly for the autotrophic picoplankton groups (especially Synechococcus and picoeukaryotes) that were significant hosts for viral infection. However, the largest part of the total picoplankton biomass loss through the viral lysis was related to bacteria (48-98%). A rise in temperature of 3°C increased the both, picoplankton biomass production and the amount of lysed picoplankton biomass, especially autotrophic hosts. These results suggest that the global warming could increase the virus- mediated flux of picoplankton carbon toward the pool of dissolved organic matter.