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Istraživački pristup u prirodoslovnim predmetima omogućuje razvoj istraživačkih vještina učenika, potiče njihovu želju za učenjem, ali i pobuđuje interes za znanost. Učenici samostalno pristupaju rješavanju problema i stvaraju nove ideje i rješenja. Aktivno sudjeluju u svim istraživačkim procesima od postavljanja ciljeva rada, formuliranja istraživačkog pitanja, prikupljanja rezultata i izvođenja zaključaka. Ovakav način učenja, često u obliku izvanučioničke nastave, pridonosi i lakšem usvajanju nastavnog sadržaja i složenih tematskih cjelina te učenik upoznaje prirodni okoliš, razvija ekološku svijest i vježba snalaženje u prirodi. Primjenom aktivnog poučavanja nastavniku je olakšana korelacija nastavnog sadržaja Biologije sa sadržajem ostalih prirodoslovnih predmeta što pridonosi boljem razumijevanju naučenog. U ovom radu predloženo je istraživanje anatomije, morfologije i ekologije virnjaka s naglaskom na njihovu sposobnost regeneracije kako bi učenici shvatili proces regeneracije oštećenih dijelova tijela kao i uporabu virnjaka kao modela u različitim istraživanjima. Sadržaj ovog rada poslužit će nastavnicima osnovnih i srednjih škola. Samostalnim iskustvenim i istraživačkim učenjem, primjenom metoda suradničkog učenja ili odabirom projektnog učenja, na kreativan se način mogu ostvariti ishodi unutar makrokoncepta prirodoznanstveni pristup u integraciji s ostalim ishodima učenja.

Changes in the functional groups of zooplankton were studied in autumn in a temperate floodplain lake (Lake Sakadaš, Kopački Rit Nature Park, Croatia) and in the Drava River (in the Croatian part of the river). Various abiotic parameters as well as available food sources (phytoplankton and microphytes (algae and cyanobacteria) developing on epixylon, epilithon and artificially introduced microplastics called "plastisphere") were also studied. The lake was hydrologically isolated from the main river during the study, while the water level of the Drava River fluctuated, resulting in larger variations in limnological parameters. Due to stable conditions in the lake, zooplankton abundance, biomass, and species richness were higher than in the Drava River. In both environments, zooplankton species feeding on bacteria, detrital suspensions, and small algae were most abundant, with predators and microfilter-feeders being more abundant in the lake. Microphytes were diverse and mostly small and medium-sized in phytoplankton and all substrate types. Stable lake conditions promoted higher abundance of the zooplankton group, which effectively uses larger algae as a food source. The lower abundance of zooplankton feeding on larger algae and predatory species in the river suggests that the epilithon and plastisphere community was a less mature community compared to the lake, and the heterotrophic component with ciliates and/or other small heterotrophs was not well developed. The importance of plastispheres was particularly evident under the turbid hydrologic conditions that prevailed in the river at the end of the study, when phytoplankton biomass decreased and zooplankton abundance steadily increased, suggesting that microphytes colonised on microplastics were an additional food source for higher trophic levels.

To study the early colonization processes, polyethylene terephthalate (PET) microfragments were immersed in Lake Sakadaš and the Drava River and sampled weekly together with the surrounding biotic communities - phytoplankton, zooplankton, epixylon in the lake and epilithon in the river. At the end of the study, a rise in water level occurred in the river, which altered the environmental conditions and plankton communities. In studied environments, all of the sampled biotic communities were diverse and abundant. Plastispheres formed in both waters by the seventh day of incubation and developed rapidly, reaching a peak in abundance on the last day of the study. Initial colonization was supported equally by planktonic and periphytic taxa in both environments, but after initial settlement, plastisphere assemblages were affected differently in the river and lake. This study suggests that PET microfragments are a suitable substrate for microphyte settlement and may provide an important pathway for their transport in dynamic freshwater floodplains and river systems.

The aim of this study was to determine microcrustacean secondary production (P/B) and a herbivory ratio (ZB:PB) in the River Danube and a floodplain lake to reveal models in plankton food web functioning. P/B was used to assess population variation under different environmental conditions, while ZB:PB provided information on the zooplankton grazing intensity on algae. Seasonal changes, displayed by the hydrological regime, i.e., related water level fluctuation, were expected to explain different plankton patterns between the study sites as a result of unlike community composition and food quality. The structural equation modelling we used identified specific pathways of measured indexes at the individual localities. Although the direct impact of water level fluctuation on the studied communities was low, the following difference in abiotic components might have caused shifts in zooplankton assemblages that changed P/B and ZB:PB ratios. In the floodplain lake, P/B was primarily influenced by biotic components, and herbivory alteration was expressed through top-down control. On the contrary, P/B in the riverine system was controlled by an environmental element and herbivory was driven by the bottom-up resources. The results show the usefulness of the studied indexes in determining variations of zooplankton functional processes in the hydrologically dynamic environments.

Microcrustacean species (Cladocera, Copepoda) as a significant component of the plankton assembly play diverse roles in floodplain ecosystems and cope with the heterogenic environment differently. Since alterations in the hydro regime are considered disturbance events for zooplankton development, we assessed whether and to what extent are Cladocera and Copepoda exposed to disturbances caused by hydro regime alterations in a floodplain lake. To evaluate the disturbance levels for individual microcrustacean assemblage in different water layers and between different hydrological phases, we applied the abundance/biomass comparison (ABC) method. Recorded microcrustacean assemblages highly depended on the hydrological state of the waterbody and diverged accordingly. Cladocera demonstrated to be more sensitive to change in specific environmental parameters like conductivity, temperature and transparency, while Copepoda exhibited no limitation by ecological variables. Although both groups were influenced by the bottom–up and top–down control, different disturbance intensity was recorded for the individual microcrustacean class. An undisturbed condition during isolation of the Lake allowed Cladocera to reach equilibrium while both microcrustacean groups exhibited moderate to high levels of disturbance following inundation. Regarding disturbance intensity, Cladocera expressed a weak distinction following hydro regime and water layer replacement. On the other hand, Copepoda disturbance levels notably depended on the position in the water column within a specific hydrological phase. Results of the ABC analyses gave a good representation of a real community dispersal in the studied Lake. However, more research is needed to re-evaluate here given levels of disturbance properly.

Two calanoid species,Arctodiaptomus laticeps(Sars, 1863) andEurytemora velox(Lilljeborg, 1853), are reported from the Danube River basin in Croatia. Our findings present the first record ofA. laticepsandE. veloxat the territory of Croatia. Both species were found in the lowland floodplain area during the spring-summer inundation throughout the years. Their occurrence in the waterbodies studied has not overlapped, and different environmental parameters characterized the periods of occurrence of the individual species. The existence ofE. veloxin this region seems to be permanent, whereas the appearance ofA. laticepsis rather confounding.

Dissimilar life features of Rotifera, Cladocera and Copepoda enable these organisms to respond differently to changes in the hydrological regime which influence alterations in environmental characteristics. We investigated the effect of habitat heterogeneity (e.g. eupotamal, parapotamal, palaeopotamal) on individual zooplankton group assemblages and biodiversity indices (α, β and γ diversity) during hydro regime change in floodplain waterbodies. Dissolved oxygen and organic nitrogen concentrations changed significantly among hydrological states while water depth was affected by both site and hydro regime replacement. Each studied site supported different zooplankton assemblage that highly depended on species-specific responses to hydro regime change. Also, individual zooplankton groups exhibited different correlations with specific environmental parameters regarding site change. Throughout the study, rotifers′ local (α) and among- community (β) diversities were susceptible to the site and inundation change while the microcrustacean biodiversity pattern diverged. Copepods highly discriminated different habitat types and hydrological phases at the regional scale (γ diversity), while we found a complete lack of biodiversity dependence on both site and hydrology for Cladocera. Our results show that heterogeneous environments support the development of different zooplankton assemblages that express the within-group dissimilarities. They also point to the importance of identifying processes in hydrologically variable ecosystems that influence biodiversity patterns at an individual zooplankton group level. Our results suggest the use of appropriate zooplankton groups as biological markers in natural habitats and stress the importance of proper management in preserving biodiversity in floodplain areas.

Istraživanja zooplanktona na području Parka prirode Kopački rit provođena su rijetko tijekom druge polovice 20. stoljeća. Većina se istraživanja bavila proučavanjem samo jedne skupine, bez prikupljanja većeg broja podataka i istovremenog istraživanja glavnih skupina zooplanktona. Od 2007. godine do danas provodi se kontinuirano istaživanje zooplanktona (Rotifera, Cladocera, Copepoda) u različitim vodenim tijelima Kopačkog rita i glavnome toku Dunava mjesečnom dinamikom. Cilj dugoročnog monitoringa je utvrditi povezanost promjene godišnjih doba i sastava zajednice zooplanktona te utvrditi utjecaj različitih lokaliteta u definiranju strukture zajednice. Također, posebna je pozornost posvećena proučavanju utjecaja hidrologije na razvoj zajednice zooplanktona. Rezultati su pokazali da su vodena tijela unutar poplavnog područja pogodna mjesta za razvoj svih skupina zooplanktona. Suprotno tomu, glavni tok rijeke Dunav pogodan je za razvoj samo kolnjaka i juvenilnih stadija planktonskih rakova koji postižu znatno manju brojnost u usporedbi s vodenim tijelima unutar poplavnog područja. Dugoročno istraživanje područja potvrdilo je da su kolnjaci najbrojnija skupina zooplanktona na području Kopačkog rita tijekom svih godišnjih doba i hidroloških faza. Ipak, različiti lokaliteti unutar poplavnog područja (kao što su jezera i kanali) podržavaju različite zajednice zooplanktona, čak i pri istome vremenu uzorkovanja. Sastav zajednice kolnjaka mijenja su učestalo tijekom izmjene hidroloških faza te se može prilagoditi novim uvjetima okoliša na svim lokalitetima. Za razliku od kolnjaka, veslonošci su iznimno selektivni u odabiru poželjnog okoliša te se ne razvijaju na pojedinim lokalitetima. Tijekom desetogodišnjeg istraživanja utvrđene su dvije nove vrste veslonožaca za faunu Hrvatske: Arctodiaptomus laticeps (Sars, 1863) i Eurytemora velox (Lilljeborg, 1853). Također su pronađene i dvije nove vrste veslonožaca na području hrvatskog dijela Panonske regije: Paracyclops fimbriatus (Fischer, 1853) i Macrocyclops albidus (Jurine, 1820). Dugogodišnje istraživanje pokazalo je da sastav zajednice te odnos pojedinih skupina zooplanktona može ukazivati na trofičko stanje vodenog tijela te može služiti kao pokazatelj njegova ekološkoga stanja.

The aim of this study was to examine for the first time the composition of zooplankton community along the greatest part of the Sava River flow. Eighty two zooplankton taxa were collected at the Sava River in September of 2012, 7 Rhizopoda, 8 Ciliophora, 57 Rotifera, 7 Cladocera, 2 Copepoda, and 1 Bivalvia. The number of zooplankton species found at sampling sites varied between 2 and 30. The most diverse group was Rotifera, which comprised 69 % of the total number of recorded taxa. The abundance of zooplankton was low and the abundance of individual zooplankton communities varied between 1 and 36 ind/L, and these results are in accordance with the results of previous works. The similarity indices (Sorensen’s and Jaccard’s) between the localities studied were rather low, despite relatively close distances between them. The probable reason was that the sites were localized at the sections of the river characterized by different environmental factors.