Naslov
Taxonomic composition and seasonality of diatoms in three karstic rivers in Herzegovina (Bosnia and Herzegovina)

Autori
Hafner, Dubravka ; Jasprica, Nenad

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Abstracts of the 4th Central European Diatom Meeting, Reichenau/Bodensee, Germany, March 2010 / Kusber, Wolf-Henning ; Jahn, Regine - Berlin : Botanic Garden and Botanical Museum Berlin-Dahlem, 2010, 24-25

ISBN
978-3-921800-66-9

Skup
4th Central European Diatom Meeting

Mjesto i datum
Reichenau, Njemačka, 12.03.2010. - 14.03.2010

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Diatoms; taxonomy; ecology; karstic rivers

Sažetak
Herzegovina is a karstic region characterized by an average annual rainfall of 1, 500 mm, and a general lack of surface water. Owing to the porous nature of karstic rock, complex sub-surface water circulation patterns appear. In such circumstances, karstic springs are formed, typical small micro-environments of Dinaric karst. Karstic springs represent a very interesting environment with a high variability of ecological factors. In general, the floristic and ecological characteristics of diatoms in Bosnia and Herzegovina have not been adequately researched. An insufficient knowledge of diatoms creates difficulties, particularly in the classification of springs and in the control of water quality, as diatoms are known to be reliable indicators of biological water quality. The aim of the study was to determine the taxonomic composition and seasonality of benthic algae, with a special emphasis on diatoms (Bacillariophyta) in the springs of three karstic rivers in Herzegovina: Bunica (5.8 km long ; average annual flow of the spring is 18.8 m s-1), Buna (9.0 km ; 39.0 m s-1) and Radobolja (6.0 km ; 1.98 m s-1). The rivers are tributaries of the Neretva River (218 km), with a source located deep in the hinterland of Bosnia and Herzegovina. All of these rivers are situated near the capital of Herzegovina – the city of Mostar. Water samples were taken on March 15, May 15, June 20, August 3 and October 27, 1998 from springs and creeks ca. 200-300 m downriver. The main physical-chemical (water temperature, pH, conductivity, concentration of dissolved oxygen and oxygen saturation), and other chemical parameters were analyzed. Laboratory chemical analysis was performed according to APHA (1975). Epilithic samples were scraped from the upper surface of the stones with a metal scalpel. Epiphytic samples were scraped from leaves, stems and roots of higher plants (Agrostis stolonifera, Berulla erecta, Veronica beccabunga, etc.). Rhizoids of mosses (mostly Cinclidotus sp., Fontinalis antypyretica and Platyhypnidium rusciforme) were cut, immersed in some water, shaken vigorously and rubbed gently to remove the attached algal film. In addition, epipelic algae were sampled. All samples were fixed in a 4% formalin solution. The collected samples where prepared for investigation by cleaning frustules using the method described by Hustedt (1930). Examination, identification and counting of diatoms were carried out using the oil immersion lens (100 x) of the Microstar binocular microscope, AO Scientific Instruments. Photomicrographs were taken for the majority of species. The counting method described by Vilbaste (1994) was applied, where 500 valves were counted per sample, while the other valves were also identified and recorded. Altogether, 166 taxa of benthic algae were determined in all three karstic rivers. The highest number of taxa had Bacillariophyta (129 or 78% of the total number of taxa), followed by Cyanobacteria (17 taxa, 13%), Chlorophyta (eight taxa, 4.8%), Conjugatophyceae (five taxa, 3%) and Xanthophyta (four taxa, 2%). Seasonality of the taxonomic groups was similar among the rivers. The highest diatom diversity was found in the Bunica (87 taxa) and Buna (66) rivers, and the lowest in the Radobolja River (55). Only 17 diatom taxa (or 13%) were common for all three springs. Seasonal distribution of diatom taxa was similar in all rivers. A maximum number of taxa was noted in May (19-38 taxa) and the lowest in October (7-19 taxa). In total, 28 diatom genera were recorded. The most common diatom genera were Gomphonema (with 18 species and lower taxa), Navicula (15), Nitzschia (14), Surirella (9), and Achnanthes, Cocconeis and Fragilaria (8). Taxa Cocconeis placentula and Meridion circulare were present in all samples. In comparison to downriver areas, the diversity of diatoms was higher in the springs of the Buna and Bunica rivers. On the contrary, diatom diversity in the Radobolja River was higher in creeks (56 taxa) than in springs (25 taxa). This may be related to specific hydrological regimes. The taxa Encyonema ventricosa and Gomphonema augur were the most abundant taxa at the Bunica and Buna rivers, and Denticula tenuis var. crassula at the Bunica and Radobolja rivers. Oligo- to oligo-mesosaprobic indicators prevailed (60%). The creeks were characterized by lower saprobity index values than in corresponding springs. Due to the specific hydrologic character of Dinaric karstic rivers, forthcoming research should provide more information on the ecology of the diatoms in these variable ecosystems.

Izvorni jezik
Engleski

Znanstvena područja
Biologija

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