A comparative study of the two northeastern ports of the Adriatic Sea indicated that the port of Rijeka is microbiologically more loaded than the port of Pula and posing a greater threat to other ...ports through a potential transfer of pathogens by ballast water. Fecal indicator bacteria, Escherichia coli and intestinal enterococci, were investigated seasonally in 2014–2015 in the ports and during the bathing season monitoring in the two bays where ports are located in 2009–2020. In addition, the indicators and pathogens related to human health were determined in the ports’ seawater and sediment. The determined factors contributing to microbiological pollution were higher number of tourists and locals, potential wastewater and ballast water discharge and enclosed port configuration, with high solar radiation and low precipitation reducing the negative effects. Our research points to the necessity of including Clostridium perfringens in monitoring beach sand during the bathing seasons and a wider list of pathogens in port monitoring due to a potential transfer by shipping ballast water.
Commercially available probiotics are routinely administered as feed supplements in aquaculture important species. Among them, the European sea bass (Dicentrarchus labrax) is the most widely reared ...fish in the Mediterranean, whose rearing systems are highly variable between countries, affecting at some level the sustainability of production. After random isolation of autochthonous gut bacteria of the sea bass, their identification and pathogenicity testing, we have selected three potentially probiotic isolates; Pseudoalteromonas sp., Alteromonas sp., and Enterovibrio coralii. Selected isolates were tested and their immunostimulative efficiency was compared with a commercially available Lactobacillus casei isolate, inferring inflammatory, apoptotic and anti-pathogen response of sea bass' peripheral blood leukocytes. Phagocytic activity, respiratory burst, and expression of lysozyme, Mx protein, caspase 3, TNF-α, IL-10 genes was measured 1, 3, 5, and 12 h post-stimulation by four bacterial isolates to evaluate early kinetics of the responses. Best immunostimulative properties were observed in Pseudoalteromonas-stimulated leukocytes, followed by Alteromonas sp. and L. casei, while Enterovibrio coralii failed to induce significant stimulation. Based on such in vitro assay intestinal autochthonous bacterial isolates showed to have better immunostimulative effect in sea bass compared to aquaculture-widely used L. casei, and further steps need to engage tank and field feeding trials to evaluate long-term prophylactic suitability of the chosen isolates. A panel of biomarkers that represent pro-/anti-inflammatory, pro-/anti-apoptotic, and anti-bacteria/viral responses of the fish should be taken into consideration when evaluating the usefulness of the potential probiotic in aquaculture.
Although Aerobic Anoxygenic Phototrophs (AAPs) are widespread in aquatic environments, relatively little is known about their dynamics in the Adriatic Sea. Therefore, we investigated their ...distribution along the trophic gradient from coast to the open sea over a year-round period, for the first time, as well as the factors that influenced the spatio-temporal distribution. AAP abundances varied between 0.26 × 104 at the open sea, and 23.45 × 104 cell mL−1 in the estuarine area, while their relative abundances ranged between 1.13% and 23.88% respectively. The biomass of AAPs ranged between 0.07 and 6.24 μg C L−1; thus, we observed a trend of decreasing abundances and biomass of the studied groups from more eutrophic coastal to the oligotrophic open sea area. AAP biomass exhibited the highest values during summer in the estuarine areas and the lowest during winter in the open sea. The main driving factors for the whole picoplankton community variance were transparency (Secchi disc), chlorophyll and salinity, whereas AAPs were grouped with heterotrophic bacteria, picoeukaryotes and heterotrophic nanoflagellates. Our data indicate that phosphorus limitation in the environment could be an important factor for the AAP growth.
A recent analysis of the Mediterranean Sea surface temperature showed significant annual warming. Since small picoplankton microorganisms play an important role in all major biogeochemical cycles, ...fluxes and processes occurring in marine systems (the changes at the base of the food web) as a response to human-induced temperature increase, could be amplified through the trophic chains and could also significantly affect different aspects of the structure and functioning of marine ecosystems. In this study, manipulative laboratory growth/grazing experiments were performed under in situ simulated conditions to study the structural and functional changes within the microbial food web after a 3 °C increase in temperature. The results show that a rise in temperature affects the changes in: (1) the growth and grazing rates of picoplankton, (2) their growth efficiency, (3) carrying capacities, (4) sensitivity of their production and grazing mortality to temperature, (5) satisfying protistan grazer carbon demands, (6) their preference in the selection of prey, (7) predator niche breadth and their overlap, (8) apparent uptake rates of nutrients, and (9) carbon biomass flow through the microbial food web. Furthermore, temperature affects the autotrophic and heterotrophic components of picoplankton in different ways.
This study defines performance characteristics of the temperature-modified ISO 9308-1 method for E. coli enumeration in bathing water. After a 4-hour resuscitation period at 36 ± 2 °C, the incubation ...temperature was changed to 44 ± 0.5 °C. Elevated incubation temperature significantly suppressed the growth of thermo-intolerant bacteria, and enhanced the selectivity of Chromogenic Coliform Agar (CCA) up to 49.5% for inland and up to 66.0% for coastal water. Consequently, most of the selectivity-related performance characteristics are improved.
Relative recovery was determined by comparing an alternative method against the reference, ISO 9308-1:2014 method, following the criteria set out in ISO 17994:2014. Temperature modification did not significantly alter the results and the methods were evaluated as “not different” for both, coastal and inland waters.
Chromogenic Coliform Agar was assessed as a suitable medium for reliable E. coli enumeration in bathing water when incubated for 17–19 h at 44 ± 0.5 °C after the 4–5 h resuscitation period at 36 ± 2 °C.
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•A resuscitation period was crucial for E. coli recovery by the modified method.•Relative recovery was high for both inland and coastal bathing water samples.•Temperature modification significantly enhanced the selectivity of the method.•All performance characteristics meet the requirements of ISO 13843:2017.•The method was assessed as suitable for E. coli enumeration in bathing water.
The Mediterranean Sea (including the Adriatic Sea) has been identified as a ‘hotspot’ for climate change, with the prediction of the increase in water temperature of 2–4°C over the next few decades. ...Being mainly oligotrophic, and strongly phosphorus limited, the Adriatic Sea is characterized by the important role of the microbial food web in production and transfer of biomass and energy towards higher trophic levels. We hypothesized that predicted 3°C temperature rise in the near future might cause an increase of bacterial production and bacterial losses to grazers, which could significantly enlarge the trophic base for metazoans. This empirical study is based on a combined ‘space-for-time substitution’ analysis (which is performed on 3583 data sets) and on an experimental approach (36 in situ grazing experiments performed at different temperatures). It showed that the predicted 3°C temperature increase (which is a result of global warming) in the near future could cause a significant increase in bacterial growth at temperatures lower than 16°C (during the colder winter-spring period, as well as in the deeper layers).
The effect of temperature on bacterial growth could be additionally doubled in conditions without phosphorus limitation. Furthermore, a 3°C increase in temperature could double the grazing on bacteria by heterotrophic nanoflagellate (HNF) and ciliate predators and it could increase the proportion of bacterial production transferred to the metazoan food web by 42%. Therefore, it is expected that global warming may further strengthen the role of the microbial food web in a carbon cycle in the Adriatic Sea.
•Temperature effect on bacterial growth is more significant at lower temperatures.•Availability of phosphorus doubled temperature effect on bacterial growth.•Bacterial carbon flux towards metazoan food web increases with temperature.•Global warming could strengthen the role of microbial food web in a carbon cycle.
Microbial transformations of toxic monomethylmercury (MMHg) and dissolved gaseous mercury (DGM) at the lower levels of the marine food web are not well understood, especially in oligotrophic and ...phosphorus-limited seas. To examine the effects of probable phosphorus limitation (PP-limitation) on relations between mercury (Hg) fractions and microorganisms, we determined the total mercury (THg), total methylated mercury (MeHg), DGM, and microbiological and chemical parameters in the Central Adriatic Sea. Using statistical analysis, we assessed the potential microbial effects on Hg transformations and bioaccumulation. Only in the absence of PP-limitation conditions (NO–PP-limitation) is MeHg significantly related to most chemical and microbial parameters, indicating metabolism-dependent Hg transformations. The heterotrophic activity of low nucleic acid bacteria (abundant in oligotrophic regions) seems responsible for most of Hg methylation under NO–PP-limitation. Under these conditions, DGM is strongly related to microbial fractions and chlorophyll a, indicating biological DGM production, which is probably not metabolically induced, as most of these relations are also observed under PP-limitation. MMHg biomagnification was observed through an increased bioaccumulation factor from microseston to mesozooplankton. Our results indicate that Hg transformations and uptake might be enhanced under NO–PP-limitation conditions, emphasizing their impact on the transfer of Hg to higher trophic levels.
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We analyzed and discussed bathing water quality at 11 official bathing sites in Kaštela (Croatia) in the period 2009-2022. The results showed spatial and temporal variations in quality. The worst ...bathing water quality was in the eastern part of the area, at beaches Torac, Kamp and Gojača. Levels of indicator microorganisms at identified sources of fecal pollution near these beaches indicate a significant load of fecal material to these areas. The observed decrease in annual fecal indicator bacteria exceedances, while not statistically significant, indicates a trend toward improvement in water quality. The number of sites with worse annual and final assessment showed a decreasing trend only since 2017 and 2020, respectively, which is not a ‘sufficient’ time period to draw a clear conclusion about the trend. The improvements are probably the result of intensive work in recent years to improve the sewage system in the area. In the annual and final assessment, bathing sites from Kaštela with ‘poor’ water quality accounted on average for more than 27% of all waters with ‘poor’ quality in Croatia. This implies that additional efforts are needed to eliminate the sources of fecal pollution in the area.
U ovom smo radu analizirali kvalitetu mora za kupanje na 11 službenih plaža u Kaštelima (Hrvatska) u razdoblju 2009.-2022. Rezultati su pokazali prostorne i vremenske varijacije kvalitete. Najlošija kvaliteta mora za kupanje zabilježena je u istočnom dijelu područja, na plažama Torac, Kamp i Gojača. Razine indikatorskih mikroorganizama na utvrđenim izvorima fekalnog onečišćenja u blizini ovih plaža ukazuju na značajno opterećenje fekalnim materijalom u ovim područjima. Iako trend smanjena broja prekoračenja graničnih vrijednosti indikatorskih mikroorganizama tijekom godine nije statistički značajan, ipak upućuje na poboljšanja. Broj lokacija s lošijom godišnjom i konačnom ocjenom pokazuje trend pada tek od 2017. odnosno 2020. godine, što nije dovoljno vremensko razdoblje da bi se moglo jasno zaključiti o trendu. Poboljšanja su vjerojatno rezultat intenzivnog rada na poboljšanju kanalizacijskog sustava na tom području u posljednjih nekoliko godina. U godišnjoj i konačnoj ocjeni, kaštelanske plaže s nezadovoljavajućom kvalitetom mora u prosjeku su činile više od 27% svih plaža nezadovoljavajuće kvalitete u Hrvatskoj. To ukazuje da su potrebni dodatni napori za uklanjanje izvora fekalnog onečišćenja na cijelom području.
We investigated the effect of intravalvular liquid loss on changes in Escherichia coli (E. coli) levels in mussels (Mytilus galloprovincialis) harvested in different seasons and refrigerated (5°C) ...for 72 hours. A positive effect of seawater temperature at the time of harvesting on intravalvular liquid loss was found. No changes in E. coli levels in mussels (flesh and intravalvular liquid), as the result of intravalvular liquid loss, were observed. Levels of E. coli in the flesh decreased, probably as a result of cells dying off, causing the maintenance of E. coli levels in flesh and intravalvular liquid to be stable throughout storage.
Fungal flora in coastal/inland beach sand and recreational water is a neglected field of study, despite its potential impact on human health. A joint International Society for Human and Animal ...Mycology/European Confederation for Medical Mycology (ISHAM/ECMM) working group was formed in 2019 with the task to set up a vast international initiative aimed at studying the fungal contamination of beaches and bathing waters. Here we review the importance of the topic, and list the main results and achievements from 12 scientific publications. Fungal contamination exists at different levels, and the genera most frequently found were Aspergillus spp., Candida spp., Fusarium spp., and Cryptococcus spp., both in sand and in water. A site-blind median was found to be 89 colony-forming units of fungi per gram of sand in coastal/inland freshwaters. This threshold has been used for the sand quality criterion of the blue flag in Portugal. Additionally, our data were considered pivotal and therefore used for the first inclusion of fungi as a biological taxon of interest in water quality and sand monitoring recommendations of the World Health Organization's new guidelines on recreational water quality (Vol.1-Chap7). The findings of the consortium also suggest how environmental conditions (climate, salinity, soil pH, nitrogen, etc.) influence microbial communities in different regions, and that yeast species like Candida glabrata, Clavispora lusitaniae, and Meyerozyma guilliermondii have been identified as potential fungal indicators of fecal contamination. Climate change and natural disasters may affect fungal populations in different environments, and because this is still a field of study under exploration, we also propose to depict the future challenges of research and unmet needs.
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