Flow Velocity Effect on Leaf Litter Breakdown in Tufa Depositing System (Plitvice Lakes, Croatia)

Abstract

Considerable amount of riparian leaf litter is annually supplied to the cascade Plitvice Lakes and trapped on tufa barriers where it decays together with aquatic macrophytes. These barriers are the sites of heavy calcite precipitation that can widely differ in terms of current velocity. We conducted a leafbag experiment at sites differing in flow velocity and tufa deposition rate. Decomposition of Petasites spp. and Fagus sylvatica was higher under high current (0.80 m/s) and high tufa deposition areas than in low current (< 0.20 m/s) and low tufa deposition areas (k = 0.085 vs. 0.021 for Petasites spp. and 0.009 vs. 0.002 for Fagus sylvatica). We concluded that although tufa deposition could interfere with decomposition by obstructing physical abrasion and also restricting microbial conditioning, thin calcite crusts developed on the surface of the leaves made them more fragile and thus accelerated their decomposition. High current velocity probably magnified this effect by supporting higher tufa deposition and coarser type of tufa fabrics. IntroductionLeaf litter processing in aquatic ecosystems involves a sequence of processes, from the dissolution of labile organic compounds (leaching), microbial conditioning to mechanical fragmentation by macroinvertebrates (WEBSTER and BENFIELD, 1986) and physical abrasion BOULTON and BOON (1991), especially by current velocity. The rate of litter breakdown is determined by intrinsic differences among leaves, a number of environmental variables, and the feeding activity of detrivores (e.g., ALLAN, 1995;DANGLES and CHAUVET, 2003; FER-REIRA et al., 2006;LEROY and MARKS, 2006;CARTER and MARKS, 2007).Several studies investigated the breakdown of leaf litter in karst systems where tufa precipitates (CASAS and GESSNER 1999;VIVAS and CASAS, 2002;CASAS et al., 2006;CARTER and MARKS, 2007). These studies reported contradictory results: CARTER and MARKS (2007) reported significantly faster breakdown at the tufa site than at the site without tufa precipitation, while CASAS and GESSNER (1999) found tufa precipitation to impair decomposition.

A Multiscale Framework for Sustainable Management of Tufa-Forming Watercourses: A Case Study of National Park “Krka”, Croatia

“…The average pH measured at the selected location was 8.65. The measured pH values were similar in other active tufa-forming systems [22,[62][63][64][65]. No significant seasonal fluctuations in pH were observed.…”

Seasonal patterns of Phragmites australis breakdown in a karstic freshwater system (Doberdò Lake, Northeast Italy) in relation to water level fluctuations, environmental features, and macrobenthic invertebrate communities

“…However, increasing attention has also been directed at decomposition dynamics in temporary freshwater bodies with seasonally fluctuating water levels (Bedford, 2005;Vo ¨llm & Tannenberger, 2014;Gingerich et al, 2015;Bertoli et al, 2016). Studies on litter breakdown in karst systems have been reported: several investigated lotic environments (Tanaka et al, 2006;Martı ´nez et al, 2015) and the relationship between calcite deposition and litter breakdown in travertine systems (Casas & Gessner, 1999;Carter & Marks, 2007;Belanc ˇic ˇet al, 2009;Milis ˇa et al, 2010). Kelley & Jack (2002) carried out the first study within a karst lake in Kentucky (USA) and Dolinar et al (2016) investigated the influence of water level fluctuations on the primary productivity litter decomposition of Phragmites australis and fungal root colonization in an intermittent karst wetland (Cerknica Lake, Slovenia).…”

Seiches in the Plitvice Lakes

“…Špoljar et al, 2007), organisms (e.g. Matoničkin Kepčija et al, 2011;Sertić Perić et al, 2014) and dead-leaf decomposition (Belančić et al, 2009).…”