CHARACTERISTICS AND NEW DATA OF RIVER ILOVA ICHTHYOFAUNA (CENTRAL CROATIA)

U razdoblju od travnja do listopada 2006. obavljeno je istraživanje ihtiofaune rijeke Ilove na području Bjelovarsko–bilogorske županije. Ustanovljena je prisutnost 28 vrsta riba iz 10 porodica. Najbrojnija je porodica Cyprinidae (18 vrsta), a slijede Percidae (3 vrste) i Cobitidae (2 vrste). Prema udjelu u ukupnoj brojnosti najzastupljenije su dvoprugasta uklija (Alburnoides bipunctatus) (17,4%), bodorka (Rutilus rutilus) (15,7%) i babuška (Carassius gibelio) (12,8%). U ukupnoj ihtiomasi najveći udio imaju bolen (Aspius aspius) (28,9%), deverika (Abramis brama) (18,7%) i štuka (Esox lucius) (11,4%). Istraživanjem je zabilježena prisutnost četiriju novih vrsta za rijeku Ilovu, peša (Cottus gobio), potočne pastrve (Salmo trutta), dunavske bjeloperajne krkuše (Romanogobio vladykovi) i linjaka (Tinca tinca).During the research 28 species of freshwater fish were found, belonging to 10 families. Most numerous family was Cyprinidae (18 species), followed by Percidae (3 species) and Cobitidae (2 species). Results showed that the most abundant in species were spirlin (Alburnoides bipunctatus) (17.4%), common roach (Rutilus rutilus) (15.7%) and prussian carp (Carassius gibelio) (12.8%). And in the terms of total fish weight, highest represented were asp (Aspius aspius) (28.9%), bream (Abramis brama) (18.7%) and pike (Esox lucius) (11.4%). Presence of four new fish species has been confirmed in Ilova River: bullhead (Cottus gobio), trout (Salmo trutta), danube whitefinned gudgeon (Romanogobio vladykovi) and tench (Tinca tinca)

Introduced species community over-dominates endemic ichthyofauna of High Lika Plateau (Central Croatia) over a 100 year period

108 years after Trgovčić (1908) authors made a revised list of fish species found in rivers and streams of the Lika region. Throughout the 8 years of investigation a total of 31 species of freshwater fish were recorded, of which only eight are indigenous for this area, for two species the origin is not known, and the remaining 21 species are introduced by anthropogenic activity over the last 100 years. This represents the over-domination of introduced species by the astonishing 300%. All of this increase in numbers causes significant increase in biomass and changes the naturally oligotrophic ecosystem, which might lead to rapid eutrophication and increase of water temperature. Furthermore, induced changes in the system make the habitat more suitable for introduced cyprinid fish, which again causes the increase of biomass production. Endemic fish species are retreating into upper parts of small tributaries and underground cave systems. The present research indicates species Delminichthys jadovensis, D. krbavensis, Telestes fontinalis and T. croaticus as real stygophiles, which makes them unique on the European continent

NEW DATA ON ICHTHYOFAUNA OF RIVER ČESMA (CENTRAL CROATIA)

U razdoblju od travnja do listopada 2006. provedeno je istraživanje rijeke Česme kako bi se upotpunilo poznavanje faune slatkovodnih riba Bjelovarsko–bilogorske županije. Ustanovljena je prisutnost 25 vrsta riba iz osam porodica. Najbrojnije su porodice Cyprinidae sa 16 vrsta i Percidae s tri, dok je preostalih šest porodica zastupljeno samo sa po jednom vrstom. Prema udjelu u ukupnoj brojnosti najzastupljenije su vrste Gobio obtusirostris (13,8%), Rutilus rutilus (12,4%), Rhodeus amarus (11,8%) i Carassius gibelio (11,3%). U ukupnoj ihtiomasi kudikamo najveći udio ima vrsta Carassius gibelio (49,5%), dok mnogo manji imaju vrste Silurus glanis (6,1%), Squalius cephalus (5,4%), Ameiurus melas (4,7%) i Leuciscus idus (4,1%). Zbog nepostojanja starijih literaturnih nalaza sve su vrste prvi put zabilježene za slijev rijeke Česme, dok su jez (Leuciscus idus) i pijor (Phoxinus phoxinus) novozabilježene vrste i za cijelo područje Bjelovarsko–bilogorske županije.During the period between April and October 2006 we conducted extensive research on ichthyofauna of river Česma in order to extent the knowledge of the freshwater fish fauna of Bjelovar–Bilogora county (central Croatia). We confirmed the presence of 25 fish species sorted in 8 families. Most numerous family was Cyprinidae with 16 species and Percidae with 3, while the remaining 6 families were represented by only one species. According to the proportion in the total individual number, the most abundant were Gobio obtusirostris (13.8%), Rutilus rutilus (12.4%), Rhodeus amarus (11.8%) and Carassius gibelio (11.3%). In the terms of total fish weight (ichthyomass), highest represented was Carassius gibelio (49.5%), followed by Silurus glanis (6.1%), Squalius cephalus (5.4%), Ameiurus melas (4.7%) and Leuciscus idus (4.1%). As there are no previously published data, all 25 species have been recorded for the first time for the river ^esma basin, while Leuciscus idus and Phoxinus phoxinus have also been recorded for the first time in Bjelovar–Bilogora county

Do benthic diatom assemblages reflect abiotic typology: a case study of Croatian streams and rivers

Benthic diatoms are widely used in Europe and worldwide to access ecological status of running waters. One of key goals of Water Framework Directive is to classify rivers and streams using biological quality elements and type specific reference conditions. According to system B which incorporates additional abiotic descriptors, there are 24 water types in Croatia. For biological analyses 92 rivers and streams with 140 sampling points were chosen and sampled for benthic diatoms and water chemistry simultaneously. Self organizing map (SOM) analysis was used to define biotypes from species composition and abundance of benthic diatoms. Grouping of samples in SOM resulted in 10 distinctive groups. Based on their geographical position and site characteristics, groups represent sites with similar properties (as waterbed, catchment size, altitude, size of stream) belonging to different ecoregions in Croatia. Analysis of variance revealed statistically significant differences (p<0.05) among SOM groups concerning ammonia, nitrates and total phosphorus. Indicator species analysis (IndVal) singled out species that were significantly characteristic (p<0.05) for SOM and abiotic types. Compared to abiotic groups, in which 7 out of 24 have no indicator species, all SOM groups have one or several characteristic diatom species, thus indicating diatom assemblages as valuable site descriptors. Canonical analysis of principal coordinates analysis also indicated that SOM grouping of samples is statistically reliable. Grouping of similar sites, although placed into different abiotic types, makes SOM groups with its corresponding representative species an easy tool for water quality assessment and description of reference assemblage

Dominantne vrste mrežnog fitoplanktona u Visovačkom jezeru, NP Krka

Species composition of the net-phytoplankton assemblage and seasonality of the dominant species were investigated in the travertine monomictic stratified riverine Lake Visovac in relation to the environmental variables. The one year investigation was based on monthly sampling from April 1995 to March 1996 at the two deepest vertical profiles, with a maximum depth of 25 m. Diatoms, especially Asterionella formosa Hass. dominated net-phytoplankton assemblages except in late summer and autumn when dinoflagellate species Ceratium hirundinella (O. F. Müller) Bergh became the dominate form. The effects of the short term dynamics of environmental factors on the algal growth in the barrage lenitic area of the calcareous river stressed several variables as important factors controlling annual net-phytoplankton distribution. Temperature was the variable that most affected species abundance, changes in dominance and species composition (Primer 5, BIO-ENV; http://www.primer-e.com/). CCA analysis performed on abundance dataset and environmental variables confirm the importance of temperature but also highlighted total phosphorus, conductivity and silica.Tijekom jednogodišnjeg razdoblja od travnja 1995. do ožujka 1996. istraživana je, u jednomjesečnim intervalima, vertikalna i sezonska distribucija mrežnog fitoplanktona u lenitičkom području Visovačkog jezera. Naglasak tijekom istraživanja bio je na sastav vrsta te povezanost dominantnih vrsta i okolišnih čimbenika. Najzastupljenija vrsta tijekom kasnog proljeća je dijatomeja Asterionella formosa Hass, dok ljeti i u jesen dominaciju preuzima dinoflagelat Ceratium hirundinella (O. F. Müller) Bergh. Od mjerenih ekoloških parametara, temperatura vode najznačajnije je utjecala na promjene u sastavu vrsta, njihovu zastupljenost i dominaciju (Primer 5, BIO-ENV). CCA analiza dobivena na osnovi zastupljenosti fitoplanktonskih stanica i praćenih ekoloških čimbenika potvrdila je znatan utjecaj temperature vode, kao i ukupnog fosfora, provodljivosti i silicija

Algal assemblages in springs of different lithologies (ophiolites vs. limestone) of the Konjuh Mountain (Bosnia and Herzegovina) - Online supplement

The biodiversity of algal communities and environmental conditions were investigated in the springs of Mt. Konjuh. The assemblages of 20 springs emerging from different lithologies (limestones and ophiolites, respectively) comprised 234 algal taxa. Diatoms and cyanobacteria were the most species-rich groups. The most common alkaliphilic, circumneutral, and eutraphentic diatoms were represented by the genera Gomphonema, Nitzschia, Navicula, Cymbella, and Achnanthidium, and by the cyanobacterial genus Phormidium. Hierarchical clustering and SIMPROF analysis based on relative algal abundance clustered springs into six groups, separating them mainly according to spring type and lithology. Indicator species for groups and springs on different lithological substrata were singled out, revealing 33 taxa with preferences for ophiolites, and 20 taxa with preferences for carbonates. The values of the Shannon-Wiener diversity index were moderately high per spring location, and similar for the two groups of springs on different lithologies. A higher similarity in species composition was noted between springs on ophiolites and limestones than between springs on ophiolites and other types of siliceous substrata. The present study suggests that algal assemblages in springs emerging from ophiolites, even those made up by a preponderance of silicates, should be analyzed separately from those related to springs on other siliceous substrata. The results obtained showed that most of the springs studied are affected by anthropogenic impacts and morphological alterations leading to the dominance of highly ompetitive meso- and eutraphentic algal species, thus emphasizing the importance of further investigation and conservation of these habitats

Microbial mats as shelter microhabitat for amphipods in an intermittent karstic spring

Microbial mats represent complex communities where cyanobacteria and diatoms as key organisms provide shelter for diverse assemblages of aquatic invertebrates, like the small stygophilous amphipod Synurella ambulans. Studies addressing such communities in the karst springs have rarely examined springheads, and have ignored intermittent springs. During high flow conditions the stygophilic crustaceans are flushed to the surface of a temporary stream Krčić where microbial mats prevent their drift and enables their successful retreat into underground in the periods of drought. The objective of this study was to characterize the microbial mat community of the Krčić Spring as a shelter for S. ambulans during strong current and high water level. Representative samples for diatom and cyanobacterial species identification and composition, as well as the fresh mat material for potential animal activity and cyanobacterial phylogenetic analysis were collected. The most dominant diatom was Achnanthidium minutissimum, whilst Fragilaria capucina, Meridion circulare, Navicula cryptocephala and Nitzschia palea had abundance greater than 0.5%. Morphological observations of cyanobacteria revealed that Phormidium favosum was the most dominant, with Hydrocoleum muscicola as a subdominant. Cyanobacterial phylogenetic relationship revealed two distinct clusters: (i) &quot;Phormidium cluster&quot;, confirming morphological observations in both winter and spring samples, and (ii) &quot;Wilmottia cluster&quot;, a first report for Croatia and found exclusively in the winter sample. Laboratory observations revealed a small stygophilic amphipod S. ambulans, hiding and feeding inside the pockets of fresh microbial mat. The intermittent Krčić Spring as a predator-free and competitor-free ecosystem provides a spatiotemporal conformity between microbial mat and stygophilous amphipod

Succession of Microbial Community in a Small Water Body within the Alluvial Aquifer of a Large River

Nitrogen is one of the essential elements limiting growth in aquatic environments. Being primarily of anthropogenic origin, it exerts negative impacts on freshwater ecosystems. The present study was carried out at the nitrate- vulnerable zone within the alluvial aquifer of the large lowland Drava River. The main aim was to investigate the ecosystem’s functionality by characterizing the bacterial and phytoplankton diversity of a small inactive gravel pit by using interdisciplinary approaches. The phytoplankton community was investigated via traditional microscopy analyses and environmental DNA (eDNA) metabarcoding, while the bacterial community was investigated by a molecular approach (eDNA). Variations in the algal and bacterial community structure indicated a strong correlation with nitrogen compounds. Summer samples were characterized by a high abundance of bloom- forming Cyanobacteria. Following the cyanobacterial breakdown in the colder winter period, Bacillariophyceae and Actinobacteriota became dominant groups. Changes in microbial composition indicated a strong correlation between N forms and algal and bacterial communities. According to the nitrogen dynamics in the alluvial aquifer, we emphasize the importance of small water bodies as potential buffer zones to anthropogenic nitrogen pressures and sentinels of the disturbances displayed as algal blooms within larger freshwater systems