Influence of submarine groundwater discharge on seawater properties in Rovanjska-Modrič karst region (Croatia)

Abstract

Coastal karst aquifers are dynamic hydrogeological systems with substantial hydrological, geomorphological and ecological impacts on the marine and coastal karst ecosystems, mostly induced by the submarine groundwater discharge (SGD). This paper presents complex hydrogeological settings of the Rovanjska-Modrič coastal karst region on the eastern Adriatic coast characterized by: (1) high temporal and spatial variations in seawater properties; (2) significantly reshaped coastal bottom morphology, and (3) plethora of associated biocenoses from fresh water, brackish, marine and cave assemblages. With the aim of resolving spatiotemporal interconnections of SGD and marine environment changes, we conducted field prospection and seasonal measurements of different water properties on-and off-shore. Obtained results pointed to: (1) the composite recharge system consisting of numerous sinking rivers in the distant hinterland (with different climate settings) and local precipitation input; (2) specific discharge settings highly governed by a complicated karst conduits network, the hydrological situation in the hinterland and local meteorological conditions, i.e. one system that permanently feeds coastal and probably submarine springs, while the other operates periodically; (3) disturbed winter isothermy and threelayered summer stratification of the seawater column, and (4) slightly changed trophic settings. All of that is the consequence of extreme heterogeneity of the coastal karst aquifer, characteristic for the eastern Adriatic coast.

Combining continuous spatial and temporal scales for SGD investigations using UAV-based thermal infrared measurements

“…Focused SGD with an expected circular to elliptical shape as observed by Mallast et al (2014) and Swarzenski et al (2001), are not unequivocally visible from the single frame (one thermal radiance image) only. At the upper and left ends of the single frame (first frame in Fig.…”

“…Once the ascending mixture reaches the lake's surface, it develops a radially orientated flow away from its jet centre, causing a circular-like pattern. These patterns are partially visually observable as shown in Mallast et al (2014) at the Dead Sea and in various other cases (Swarzenski et al, 2001).…”

“…Discharge behaviour in this case depends on the maturity and geometric formation of the conduit network. Following Surić et al (2015) the discharge behaviour is highly anisotropic and heterogeneous, and features a rapid flow. The anisotropic and heterogeneous discharge behaviour is furthermore underlined by the discharge onset and the periodicity that is unequal among the individual spots, even though their spatial location is within 10 m distance (Fig.…”

Bivalve trophic ecology in the Mediterranean: Spatio-temporal variations and feeding behavior

“…Seawater properties in the shallow eastern coastal Adriatic are exposed to high temporal and 99 spatial variations mainly characterized by large temperature fluctuations and freshwater inputs 100 (e.g. Ogrinc et al, 2005;Surić et al, 2015). The intrusion of freshwater is more evident in river 101 mouth areas, where also the incorporation of nutrients and organic matter from terrestrial origin 102 stimulates biological productivity and creates a characteristic fluctuating environment.…”

Groundwater quality in selected caves in Ravni kotari (Croatia)

“…Water in such caves is highly polluted and can cause serious health conditions in humans, either through consumption of such water or through contact of injured skin and water, which enables entrance of bacteria into blood. The study in Modrič Cave (30 km NE of the town of Zadar) showed that the guano deposits are responsible for significantly elevated values of heavy metals (Cu, Cd and Zn) in both cave sediments and percolating water (Miko et al, 2002), and probably in the adjoining sea water (Surić et al, 2015). Humans can also bring bacteria into caves.…”