See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/287859196 Effect of current velocity on diatom colonization on glass slides in unpolluted headwater creek Article in Periodicum Biologorum · October 2008 CITATIONS READS 10 101 3 authors: An đ elka Plenkovi ć -Moraj Koraljka Kralj Borojevic University of Zagreb University of Zagreb 52 PUBLICATIONS 607 CITATIONS 24 PUBLICATIONS 302 CITATIONS SEE PROFILE SEE PROFILE Marija Gligora Udovic University of Zagreb 44 PUBLICATIONS 442 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Biological and ecological features of the Ponikve reservoir on the island of Krk View project AQUAHEALTH - Aquatic microbial ecology as an indicator of the health status of the environment View project All content following this page was uploaded by An đ elka Plenkovi ć -Moraj on 04 March 2016. The user has requested enhancement of the downloaded file.
PERIODICUM BIOLOGORUM UDC 57:61 VOL. 110, No 2, ??–??, 2008 CODEN PDBIAD ISSN 0031-5362 Original scientific paper Effect of current velocity on diatom colonization on glass slides in unpolluted headwater creek Abstract AN\ELKA PLENKOVI]-MORAJ Background and Purpose: The goal of this study was to determine the KORALJKA KRALJ MARIJA GLIGORA effect of current velocity on diatom colonization rate during the first 30 days of artificial substrate (glass slides) exposure. Department of Botany Materials and Methods: From autumn 1990 to summer 1993 artificial Division of Biology Faculty of Science, Univesity of Zagreb substrates were submerged in an unpolluted mountain stream. The parallel Rooseveltov trg 6 oriented glass slides (against the surface) were placed 10 cm beneath the wa- 10000 Zagreb, Croatia ter surface (protected from debris) and exposed to different current velocities (10–30 cm s –1 , 40–60 cm s –1 and 80–100 cm s –1 ). The samples were col- Correspondence: lected seasonally. T o define diatom colonization, a nonlinear regressive An|elka Plenkovi}-Moraj Department of Botany analysis of empirical data was performed. Division of Biology Results: A total of 71 diatom species were found. Species Cocconeis Faculty of Science, Univesity of Zagreb placentula, Surirella ovata, Gomphonema olivaceum , and Navicula Rooseveltov trg 6 gracilis were the most abundant, depending on different current velocity. 10000 Zagreb, Croatia E-mail: aplenk @ biol.pmf.hr Conclusions: The time needed for reaching the equilibrium progres- sively increased with the current velocity (F= 16.7; P< 0.01). In the sum- mer and autumn, the time needed for the stabilization of diatom flora was Key words : current velocity, periphyton, longer than in spring and winter. Concerning species abundance, Cocco- diatoms, nonlinear regressive analysis neis placentula , and Navicula gracilis were independent of the current ve- locity, while Surirella ovata was abundant at lower (£30 cm s –1 ) and Gomphonema olivaceum at higher (£60 cm s –1 ) current velocities. INTRODUCTION P eriphyton, with phytoplankton and marcophytic vegetation, is im- portant as energy base in lotic ecosystems (1, 2, 3). Some studies on microdistribution of freshwater periphyton were primarily concerned with the epiphytic algae growing on macrophytes (4, 5, 6), but some also examined local distribution on rocks and artificial substrates (7, 8, 9, 10). Algal flora is an important component of the lotic ecosystem and is essential for the understanding of stream ecology. The studies of Gess- ner (11), Blum (12) and Backhaus (13) imply that water movements are responsible for microdistribution of epilithic algae in streams but they do not explain how current acts to create the observed preferences. Theoretical fluid mechanics can explain the way current influences periphytic algal communities. Horizontal surfaces are under the influ- ence of rather stable, laminar flow while a thin layer of water was sta- Received December 23, 2005. tionary in contact with surface, with a relatively small area exposed to
An|elka Plenkovi}-Moraj et al. The effect of current velocity on diatom colonization the turbulent flow, all depending on current velocity (14). Table 1 The greater the current velocity, the thinner the station- The mean values, standard deviations, variance and coefficient of variance of current velocity in cms –1 dur- ary layer and the larger the area exposed to the turbulent flow. Some studies, especially those conducted in lakes, ing the investigated period (avg.= average, STD= employed vertical orientation to restrict colonization to standard deviation, var= variance, V(%)= coefficient true periphytic species due to reduction of detritus and of variance). settled plankton species accumulation (10, 15). Microhabitat 1 Microhabitat 2 Microhabitat 3 According to Zimmermann (16), the most important Spring 25.00 60.00 90.00 ecological factors for the development of periphyton com- munities in running waters are organic load and current Summer 10.00 40.00 60.00 velocity. Butcher (17) found reduced periphytic densities Autumn 18.00 52.00 92.00 on slides in faster currents and Blum (18) observed that Winter 20.00 45.00 90.00 different diatoms showed different responses to current and concluded that current acted as a distribution gov- avg. 18.25 49.25 83.00 erning factor. Mc Intire (19) found that faster currents STD 5.40 7.53 13.30 apparently retarded the initial attachment of algal cells to var. 29.19 56.69 177.00 glass slides but, after a prolonged period, faster currents V (%) 29.60 15.00 16.00 produced greater biomass. Some studies have shown that early phases of colonization are characterized by rela- tively large araphid and biraphid diatoms (geni Cocco- neis , Fragilaria , Achnanthidium ), later phases with small species and cells were calculated per cm 2 . Current was mono and biraphid diatoms ( Achnanthidium , Navicula ) measured directly above the brick, with a Rost’s hydro- while medium-sized mono and biraphid species domi- metric wing. nate towards the end (20). Some studies also report Cocco- To define diatom colonization in a nonlinear regres- neis and Achnanthidium species as first colonizers, fol- sive analysis of empirical data, the following function lowed by genera with mucilaginous pads or stalks (21) or (27) was used: S (t) = S 0 /1–e –k (t–to) / ( S (t) = number of spe- attachment of horizontally positioned species as Gompho- cies at time t; S 0 = number of species in asymptote; t = nema , Nitzschia and Cymbella (22). Ghosh & Gaur (23) time; t 0 = beginning time of colonization; k = coefficient have shown that the number of cells decreases with in- of colonization current). Stabilization time of diatom crease in current velocity. There are also certain species colonization ( t S ) on artificial substrates, expressed in that prefer lower (e.g. Navicula cryptocephala Kütz.), some days, is the moment when regressive straight line align medium (e.g. Pinnularia gibba Ehr., Gomphonema oli- with values of S 0 –0,1. According to Kvalseth (28), em- vaceum Kütz.) and some tolerate high current velocities piric F-ratio yields validity of regression (95%) like as the (e.g. Rossithidium linearis (W .Sm.) Round & Bukhtiyarova, representation by the coefficient of determination (r 2 ). Gomphonema lanceolatum Ehr., Gomphonema parvulum (Kütz.) Kütz.) (23). The variables calculated from nonlinear regressive analysis and the measured velocities were analyzed by The goal of the present paper was to determine the in- main effects ANOVA with post-hoc Bonferroni tests us- teraction between algal colonization rate and current ve- ing the program Statistica, version 6.0. locity in an unpolluted headwater stream. RESULTS MATERIALS AND METHODS During the research period water velocity was signifi- Experiment was carried out from November 1990 to cantly different among three microhabitats ( Anova , p< August 1993 on a small mountain stream Veliki potok at 0.01) (Table 1). Zagreb, Croatia. Observations were done at shaded spring area. Three different microhabitats were defined with re- A total of 71 diatom species was found on glass slides. gard to the current velocity. Artificial substrates (glass The 12 most abundant species (exceeding 5%) include: slides) were horizontally placed and oriented parallel to Cocconeis placentula Ehr., Cocconeis disculus (Schum.) the current, 10 cm beneath the water surface. The micro- Cleve, Achnanthidium minutissimum (Kütz.) Czarnecki, habitats were made of seven glass slides which were fixed Meridion circulare (Grev.) Agardh, Diatoma vulgare Bory, on the upper side of a brick. Diatoms were identified (24 , Navicula gracilis Ehr., Sellaphora pupula (Kutz.) Me- 25, 26 ) with a Standard 20 light microscope. The abun- reschkowsky, Navicula radiosa Kütz., Eolimna minima dance of species was obtained by counting specimens in (Grun) Lange-Bertalot, Gomphonema olivaceum Kütz., 170 microscope fields, the counting was carried out after Gomphonema parvulum (Kütz.) Kütz., and Surirrela ovata 2, 5, 10, 15, 20, 25 and 30 days of exposure on 3 repetitive Kütz. Of these 12, four species ( Cocconeis placentula Ehr, slides. Microscopic examinations were performed on an Navicula radiosa Kütz., Gomphonema olivaceum Kütz. exposed glass slide as long as the periphyton density al- and Surirella ovata Kütz.) were dominant at different lowed it and periphyton was afterwards scarped off and currentvelocities.Thepioneercolonizationspeciesonglass suspended in a determined volume. A total number of slides, depending on current velocity, were: Cocconeis 2 Period biol, Vol 110, No 2, 2008.
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