No abstract

The coastal area around the settlement of Stara Baška (Krk Island, NE channel zone of Adriatic Sea) is in a delicate geodynamic balance. The main causes are the geological structure, hydrological and hydrogeological conditions and the direct exposure of the coast to the waves and storm surges. In this paper, the effects of the expected sea level rise on the geological vulnerability of the coast are investigated. Detailed field research was conducted. The complex coastal morphology was surveyed using an Uncrewed Aerial Vehicle (UAV), and the UAV-derived data was used as a 3D point cloud and orthophoto for analysis. In the investigated coastal zone, more resistant Quaternary talus breccias predominate over more susceptible flysch rock mass. One major and two smaller landslides are in a creeping condition and pose a hazard to the surrounding homes. During storm surges, the pocket beaches are completely inundated due to the narrow beach width and waves reach the toe of the slopes. According to the expected sea level rise, coastal processes could become more intense and threaten the current coastal equilibrium. The vulnerability of a large part of the Stara Baška settlement will increase significantly. The conducted research showed the advantages of UAV-derived data for the study of complex rocky coasts and emphasized the need for repeatable UAV surveys.

This paper analyses impacts of climate change and anthropogenic pressure on groundwater resources in the Mirna river catchment used for water supply in Northern Istria (Croatia) up to 2050. Using Regional Climate Models simulations and hydrologic model, the future average annual and the characteristic (in critical period) water resource availabilities were calculated. Current and five future water demand scenarios were analysed. Water Exploitation Index (WEI) and modified Characteristic Water Exploitation Index (CWEI) were calculated. In 2050, the analysed springs will be subject to climate change consequences, with more extreme changes and intense variations. The WEI for average conditions indicates little risk of unmet future water demand. Considering seasonal variability, the future CWEIs indicates strong risk for most future water demand scenarios and overexploitation for water demand increases over 20%. The 2012 drought, more extreme than any considered future scenario, was also examined.

The article presents findings of a two-year systematic study of stable isotope content in two karst groundwater resources in Primorsko-goranska county (Croatia): the Martinšćica wells (MWs) and the Dobrica spring (DBC). The temporal and spatial variation of hydrogen and oxygen isotopes is commonly studied in conjunction with hydrogeological conditions such as groundwater dynamics and discharge conditions. However, since this information was incomplete, we were forced to work with limited data and rely on analyses of stable isotope monitoring results. The obtained results show that winter precipitation is the most common recharge source for the systems, and the average residence time of water in the subsurface is less than a year. Furthermore, the MWs system is a typical dual-porosity system with dominant base flow. The results of the nonparametric regression analysis show that the possibility of seawater intrusion into the spring affecting DBC isotope content cannot be ruled out. We believe that the results presented in the paper demonstrate that when combined with statistical analyses, environmental stable isotopes are a powerful tool for gaining insights in karst hydrogeology.

We conducted an on‐site monitoring study involving seasonal collection of microbial mats samples from the Krčić spring located in the Dinaric karst in Croatia. This intermittent karst spring is characterized by oligotrophic conditions and extreme water regime fluctuations. Extreme conditions at the Krčić included summer drought followed by strong rains in the autumn as well as freezing ambient temperature during winter. By using two phylogenetic markers, 16S rRNA (total Bacteria) and internal transcribed spacer (ITS) region (Cyanobacteria), we aimed to detect the impact of intense seasonal fluctuations of environmental parameters in shaping (and/or selecting) the microbial mat community of the Krčić spring. Microbial mat community was found to harbour bacteria belonging to 11 different phyla with Cyanobacteria making the community core (>50%), followed by Alphaproteobacteria. The most abundant cyanobacterial genera included Microcoleus, Phormidium, and uncultured Antarctic cyanobacterium. In two mat samples, collected during conditions of low temperatures and strong bora wind (winter 2014) and during drought period (summer 2015), Cyanobacteria were diminished within the community. Under the extreme cold populations found to proliferate included Planctomycetes and candidate phylum TM6, found specifically in this sample. Members of the phyla Firmicutes were strictly found during the drought summer period followed by Cytophagia‐Fibrella, Polymorphobacter, Polaromonas, and Massilia. During the event of high water inflow following the drought, Cyanobacteria represented 90% of the community in which specific desiccant‐tolerant Chroococcidiopsis, Calothrix, and Pleurocapsa species appeared having mechanisms for quick recolonization of environments.