Three types of recent carbonate precipitates from the River Krka, Croatia, were analysed: (1) bulk tufa from four main cascades in a 34 km long section of the river flow through the Krka National Park; (2) a laminar stromatolite-like incrustation formed in the tunnel of a hydroelectric power plant close to the lowest cascade; and (3) recent precipitates collected on artificial substrates during winter, spring and summer periods. Stable isotope compositions of carbon (d 13 C) and oxygen (d 18 O) in the carbonate and organic carbon (d 13 C org ) were determined and compared with d 18 O of water and d 13 C of dissolved inorganic carbon (DIC). The source of DIC, which provides C for tufa precipitation, was determined from the slope of the line ( (Sayles & Curry, 1988). The d 13 C value of added DIC was )13AE6&, corresponding to the dissolution of CO 2 with d 13 C between )19AE5 and )23AE0& Vienna Pee Dee Belemnite (VPDB). The observed difference between the measured and calculated equilibrium temperature of precipitation of bulk tufa barriers indicates that the higher the water temperature, the larger the error in the estimated temperature of precipitation. This implies that the climatic signals may be valid only in tufas precipitated at lower and relatively stable temperatures. The laminar crust comprising a continuous record of the last 40 years of precipitation shows a consistent trend of increasing d 13 C and decreasing d 18 O. The lack of covariation between d 13 C and d 18 O indicates that precipitation of calcite was not kinetically controlled for either of the elements. d 13 C and d 18 O of precipitates collected on different artificial substrates show that surface characteristics both of substrates and colonizing biota play an important role in C and O isotope fractionation during carbonate precipitation.

An improved understanding of the anchialine ecosystem and geology warrants a redefinition of the term 'anchialine.' Originating from subareal biological observations, the term anchialine now encompasses chemical, physical, geological and biological elements within the subterranean realm. We propose a more accurate definition of the term anchialine as 'a tidally-influenced subterranean estuary located within crevicular and cavernous karst and volcanic terrains that extends inland to the limit of seawater penetration.' This subterranean estuary is characterized by sharp physical and chemical stratification and merges with a marine system at the coast and a groundwater system inland. The anchialine ecosystem supports a relatively diverse biotic assemblage of stygobiotic species of marine origin dominated by members of Crustacea, both numerically and by species richness.

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