Biodiversity, DNA barcoding data and ecological traits of caddisflies (Insecta, Trichoptera) in the catchment area of the Mediterranean karst River Cetina (Croatia)

The environmental and faunistic research conducted included defining the composition and distribution of caddisflies collected using ultraviolet (UV) light trap at 11 stations along the Cetina River, from the spring to the mouth, and also along its tributaries the Ruda River and the Grab River with two sampling stations each, and the Rumin River with one station. The research was conducted in the period from August 2004 until August 2005 on the Cetina and the Ruda rivers, and from April 2007 to September 2007 on the Grab and the Rumin rivers. A total of 71 caddisfly species and 10,048 individuals were recorded in the study area. Results of the composition and structure of caddisflies were processed with statistical methods using the NMDS analysis. There were differences in the composition of caddisflies in the upper, middle and lower reaches. The paper also presents some ecological features of caddisflies, such as seasonal dynamics and diversity of caddisflies communities. Results of this work contribute to faunistic and ecological knowledge of Croatian caddisflies.

Characteristic features of the structure and spatial distribution of phytoplankton in the Sotka river in the State nature reserve «Pinezhskii»

На территории Пинежского природного заповедника впервые исследован фитопланктон основного водотока ООПТ - карстовой р. Сотка. Приведены данные таксономического состава альгофлоры по основным ее отделам и данные анализа видового богатства. Установлено, что видовой состав фитопланктона представлен 56 таксономическими единицами, в том числе 46 диатомовыми, 6 зелеными, 2 эвгленовыми, 1 золотистой и 1 сине-зелёной. Для фитопланктонного сообщества р. Сотка характерны зональность и мозаичность распределения численности и биомассы, необычные для полугорных рек, к которым относится водоток. Отмечена неоднородность видового состава и комплекса доминант, наблюдаемая по всей исследованной акватории. Очевидно, это результат комплексного воздействия специфических экологических характеристик реки и в первую очередь - высокого уровня минерализации. В целом р. Сотка можно отнести к флористически обедненным олиготрофным водоемам со значительным преобладанием диатомовых водорослей, низкими количественными показателями численности и зонально-высокими значениями биомассы. Экологическое состояние водотока оценивается как хорошее, с умеренным содержанием органических веществ в воде. Phytoplankton of the main watercourse of the Pinezhsky Nature Reserve, the karst river Sotka, was studied for the first time. Taxonomic composition of the algal flora and the analysis of species richness are presented. The species composition of phytoplankton is represented by 56 taxonomic units, including 46 diatoms, 6 green, 2 euglena, 1 golden and 1 cyanobacteria. For the phytoplankton community of the river Sotka is characterized by zoning and mosaic distribution of abundance and biomass, unusual for semi-mountain rivers, to which the watercourse belongs. The heterogeneity of the species composition and complex of dominants, observed throughout the studied water area, was noted. Obviously, this is the result of the complex impact of the specific ecological characteristics of the river and, first of all, the high level of mineralization. In general, river Sotka can be attributed to floristically depleted oligotrophic water bodies with a significant predominance of diatoms, low quantitative indices of abundance and zonal high values of biomass. The ecological state of the watercourse is assessed as good, with a moderate content of organic matter in the water.

Sr isotope fractionation in a karst river: case study of Krka, Croatia

<p>Precipitation of calcite from water fractionates strontium (Sr) isotopes because of preferential incorporation of light (<sup>86</sup>Sr) isotopes into the solid phase, making continental carbonates one of the most <sup>88</sup>Sr depleted reservoirs. It was suggested that carbonate precipitation is the most likely process controlling <em>δ</em><sup>88/86</sup>Sr composition of karst water. Therefore, the <sup>88</sup>Sr enrichment of river water could be used for the estimation of Sr and carbonate precipitation at catchment scale.</p><p>In the present study, we report on trace element partitioning and Sr isotope fractionation between tufa and water in the groundwater fed karst river Krka (Croatia). Water and tufa along with samples of bedrock and soil as the main contributors of dissolved and particulate Sr at seven main waterfalls and cascades along a 33 km section of the river were analysed for trace element and Sr isotope composition (<em>δ</em><sup>88/86</sup>Sr).</p><p>The highest δ<sup>88/86</sup>Sr values were measured in soils and in siliciclastic rocks, while in limestone, the <em>δ</em><sup>88/86</sup>Sr values were similar to those of old tufa precipitated in the period between 96 and 141 ky BP. Recent tufa, however, was considerably depleted in <sup>88</sup>Sr. The isotope fractionation between water and recent tufa varied a lot and was inversely correlated with Mg and Sr partitioning coefficients, while correlations with precipitation rates and temperature were rather weak. The <em>δ</em><sup>88/86</sup>Sr of recent tufa was strongly correlated with the stable isotope composition of organic carbon, which indicates that apart from hydrochemical, hydraulic parameters and temperature, plants and microbial communities that knowingly stimulate the tufa formation also affect the isotope fractionation of Sr.</p>

Simulating streamflow in a temporary karst river system

<p>Most of the basins in the Mediterranean Region are characterized by a large spatial gradient in rainfall and temperature and heterogeneity in lithology, soil, and land use. Such environmental factors determine a specific hydrological regime of the river systems that generally includes periods of absence of flow and flash flood events.</p><p>In the past decades, several countries in South Europe did not invest resources for the monitoring of the intermittent river systems. Currently, several basins have limited time series of streamflow and water quality data. In addition, it is not rare the case of climate stations not well distributed in the basin as well as the presence of several gaps in the time series.</p><p>The lithology and geological features are among the main factors affecting the flow regime, playing a crucial role in groundwater and surface-water interaction and water exchange for which the flow may appear and disappear along with the river network. In such a complex environment, the hydrological and water quality model set up and run may be challenging.</p><p>Through a case study, this work aims to face some challenges and to define problem-solving in simulating hydrology in Mediterranean basins. The area is characterized by (i) heterogeneity in lithology with karst areas, (ii) limited flow data availability for calibrating the model, (iii) flow intermittence in the river network. The Soil and Water Assessment Tool (SWAT) was applied to the Canale D’aiedda  (Puglia, Italy), a temporary karst river basin under the Mediterranean climate and with limited data availability. Different solutions were tested to simulate the hydrological processes in the karstic areas including both GIS elaborations and model parameters settings and modifications. Among the main parameters, infiltration and transmission losses and soil hydraulic parameters resulted in the most relevant in simulating hydrology in the karst areas. To calibrate the model, a split-in-space procedure was adopted to overcome the limited streamflow measurement availability. Finally, a zero-flow threshold was introduced to predict the number of zero-flow days in the intermittent river reaches, simulating accurately the flow intermittence and the extreme low flow.</p><p>The results show that by using specific strategies in setting-up and calibrating the model, the SWAT model is able to simulate daily streamflow with acceptable performances in complex river basins.</p>

Assessing the effects of oxidation of pyrite and reducing nitrogen fertilizer on chemical weathering and the carbon cycles in a karst river system by using multiple isotopes

<p>Pyrite is the most common sulfide mineral occurring in sedimentary and igneous rocks and globally contributes a greater flux of sulfate. Large quantity of reactive nitrogen as fertilizers for agricultural production has been released into the environment in China over recent decades. Sulfuric acid formed by oxidative weathering of pyrite (OWP) and nitric acid formed by oxidation of reducing nitrogen fertilizer (ONF) through neutralization with carbonate minerals can counteract CO<sub>2</sub> drawdown from chemical weathering. Here, we use the multiple isotopes (<sup>13</sup>C-DIC, <sup>34</sup>S and <sup>18</sup>O-SO<sub>4</sub><sup>2–</sup>, <sup>15</sup>N and<sup> 18</sup>O-NO<sub>3</sub><sup>–</sup>, and <sup>18</sup>O and D-H<sub>2</sub>O) and water chemistry, as well as historical hydrochemical data to assess the roles of strong acids in chemical weathering and the carbon cycle in a karst river system (Chishui River, southwestern China). The variations in alkalinity and the δ<sup>13</sup>C-DIC along with theoretical mixing models demonstrate the involvement of strong acids in carbonate weathering. However, the strong acid weathering flux determined by δ<sup>13</sup>C-DIC and mixing models is considered to be overestimated due to the effects of photosynthesis and degassing of CO<sub>2</sub> on δ<sup>13</sup>C-DIC signal. The protons liberated from OWP and ONF can be constrained by water chemistry and isotope techniques with the use of a Bayesian isotope mixing model. The strong acid weathering flux determined using proton information is higher that determined by δ<sup>13</sup>C-DIC and mixing models. This suggests that the additional protons derived from OWP and ONF might be consumed in other ways without affecting the δ<sup>13</sup>C-DIC signals, such as the neutralization of acidic waters. These results indicate that OWP and ONF coupled with carbonate dissolution significantly enhanced the coupling cycles of carbon, nitrogen and sulfur in this river system.</p>

Impact of large human constructions on a karst river hydrology: Case of the Cetina river (Dinaric karst)

The paper studies drastic hydrological changes caused by construction of five reservoirs and six hydro-electric power plants (HEPP), built mostly in the 1960s, along the watercourse of the karst river Cetina, located in deep and well-developed Dinaric karst. The total river length from its spring to mouth in the Adriatic Sea is about 105 km. Discharges are monitored at nine gauging stations and then compared using statistical methods. Discharges measured before construction of hydraulic structures were compared with discharges measured afterwards. Analysis of the results determined that the complex natural hydrologic regime has been completely destroyed. The hydrology of the upper river, from the spring to the Prančevići Dam (length of about 65 km), is changed by the development and operation of the Peruča Reservoir and the Peruča HEPP, as well as the Lipa and the Buško Blato Reservoirs and Buško Blato and Orlovac HEPPs. Water diversion from the Prančevići Reservoir through two tunnels and pipelines to power the Zakučac HEPP has dangerously altered hydrological regime of the Cetina River’s 40 km-long downstream section. In the 65 km-long upstream section, instantaneously after the Peruča Reservoir putting in operation. In the downstream section the majority of natural flow is lost. The mean annual discharges dropped from more than 100 m3 s-1 to less than 10 m3 s-1. Due to HEPPs operation, minimum annual discharges have drastically and dangerously decreased.