Calcite deposition in karst waters is promoted by leaf litter breakdown andvice versa

Abstract

-Plant litter breakdown, an important process for energy and matter flows in freshwater ecosystems, has been extensively studied except in the karst (and calcite depositing) habitats. The aim of this paper was to answer three questions regarding the breakdown of leaf litter in calcite depositing environment: (i) Does leaf decomposition hinder calcite deposition and vice versa?; (ii) What role do other environmental factors play?; and (iii) How long does leaf litter persist in these habitats? Leaves of beech (Fagus sylvatica) and butterbur (Petasites hybridus) were exposed for 8 weeks in 8 microhabitats: 2 calcite deposition rates r 2 flow velocities r 2 seasons. A linear model was better at predicting leaf litter persistence but only for the period after the extreme loss of leaf mass occurring during the initial leaching of highly hydrosoluble compounds in the first week (11.6% of beech and 54.2% of butterbur regardless of the studied environmental factors). Higher flow velocity and calcite deposition rates stimulated the breakdown of both leaf species. During summer, breakdown was accelerated for butterbur leaves only. Since breakdown rates of both litter types were faster at high calcite depositing sites, it can be concluded that the breakdown process is not hindered by calcite deposition in general. The amount of deposited calcite per gram of leaf litter increased linearly over time (after the first week of exposure) on both leaf species. More calcite was deposited on the fast-decomposing butterbur leaves than on beech leaves.

Effects of flow scarcity on leaf-litter processing under oceanic climate conditions in calcareous streams

“…This, as Casas and Gessner (1999) pointed out, may simulate siltation or burying of materials leading to delay leaf-litter processing. However, in our case, a different trend arises, being enhanced leaf-litter processing in spite of the lower density of principal benthic macroinvertebrate consumers as in karstic streams with a discontinuous travertine layer (Carter and Marks, 2007;Miliša et al, 2010). In the present study, the most suitable explanation is that the fauna find a food substrate in bags less affected by calcite precipitation, as the ratio of invertebrates in bags to invertebrates in benthos was highest in this stream.…”

“…In fact, in some calcareous streams a travertine precipitation may occur resulting in a layer that covers the stream bottom and the standing substrates. This feature influences litter decomposition, enhancing the process when the travertine deposition is not continuous (Carter and Marks, 2007;Miliša et al, 2010) or slowing down when a compact and continuous layer happens (Casas and Gessner, 1999). In this kind of systems the effects of droughts have been studied, but mainly focused on structural attributes as fauna (Agnew et al, 2000;Boulton, 2003), lacking information about the effects on a functional attribute as leaf litter decomposition.…”

Environmental drivers influencing stonefly assemblages along a longitudinal gradient in karst lotic habitats

“…P. auberti, L. prima, L. pusilla, Taeniopteryx hubaulti) (Graf et al, 2009(Graf et al, , 2017, relating to favourable environmental conditions (i.e. low water temperature and high oxygen concentration; Hynes, 1976;Fochetti and Tierno de Figueroa, 2008;Zwick, 2011) and the wide range of suitable habitats (Riđanović and Božićević, 1996;Miliša et al, 2010). The differences in abundance and taxa richness between the two studied years could be attributed to the variability of environmental conditions, especially water temperature and discharge, as already shown in some other studies (Zwick, 2011;Ivković et al, 2012Ivković et al, , 2014Vilenica et al, 2017a).…”

Emergence patterns and ecological associations of some haematophagous blackfly species along an oligotrophic hydrosystem

“…Given sufficient food, lakes can support dense, rapidly growing populations of filter-feeding simuliid larvae (Wotton, 1988;Richardson & Mackay, 1991). The largest blackfly populations were found at the tufa barriers of Labudovac (BL) and Kozjak-Milanovac (BKM), probably because the lakes above these barriers were richer in organic matter than were the lower lakes above the tufa barrier Novakovića Brod (BNB) (Špoljar et al, 2007;Miliša et al, 2010). That the numbers of blackflies found in 2008 were lower than those found in 2007 at all locations except the Korana River site (KS) may be attributable to higher discharge rates (numbers are lower when discharge prior to the period of emergence is higher).…”