Slatkovodne dijatomeje (Bacillariopbyceae) Hrvatske

In this paper, a check-list of freshwater diatoms (Diatomeae, Bacillariophyceae) of Croatia is presented for the first time, using the available literature published in the period from 1900 to 1995. Degree of saprobity is included for all indicator species. A total of 530 taxa has been established: 378 species, 139 varieties, 13 forms grouped in 45 genera. Species indicators of o, o-ß, and ß-mesosa- probity are predominant (86% ). The most common species in the biotopes investigated such as lakes, rivers, natural and artificial accumulations, and hot springs were: Fragilaria capucina, F. croto- nensis, Synedra ulna, Diatoma vulgare, Navícula lanceolata, N. cryptocepbala, N. gracilis, Nitzschia palea, Gomphonema olivace- um, Cymbella ventricosa, Meridion circulare, and Cocconeis placen- tula. Fresh diatom flora provides six endemic species of Croatia: Achnantbes plitvicensis, Cyclotella plitvicensis, C. pevaleki, C. juri- Ijii, Navícula jakovljevici, and N. plitvicensis.Na osnovi dostupnih literaturnih podataka, objavljenih u razdoblju od 1900 do 1995. godine, iznosi se po prvi puta sustavni popis slatkovodnih alga kremenjašica Hrvatske (Diatomeae; Bacillariophyceaé). Analizom podataka utvrđeno je 530 taxona: 378 vrsta, 139 varijeteta i 13 formi, grupiranih u 45 roda. Dominiraju dijatomeje indikatori o, o-ß, i ß- mezo- saprobnog stupnja (86% ). U svim istraživanjima biotopima redovito su prisutne vrste: Fragilaria capucina, F. crotonensis, Synedra ulna, Diatoma vulgare, Navícula lanceolata, N. cryptocephala, N. gracilis, Nitzschia palea, Gomphonema olivaceum, Cymbella ventricosa, Meridion circulare i Cocconeis placentula. Utvrđeno je i šest vrsta dijatomeja karakterističnih isključivo za područje Hrvatske (Achnanthes plitvicensis, Cyclotella plitvicensis, C. pevaleki, C. ju- riljii, Navícula jakovljevici i N. plitvicensis)

Microphytobenthic communities in the fresh water of Trsteno Arboretum (southern Croatia)

The microphytobenthos from the fresh water of Trsteno Arboretum consisted of 84 species, mostly diatoms (55 species). There were 15 representatives of Chlorophyceae and 10 Cyanobacteria, as well as scattered representatives of Schizomycetes, Xanthophyceae and Mycota. Five diatoms were present throughout the research period: Achnanthes affinis Grun., A. microcephala Grun.. Cocconeisplacentula Ehr., Synedra ulna Ehr., and Gomphonema dichotomum Kiitz. The maximal number of species was detected during the winter and spring, and the minimum number in autumn. The saprobic index, based on the characteristic species determined in the benthic community (ranging from 1.7 to 2.2) indicated moderate impurity

Microphytobenthic communities in the fresh water of Trsteno Arboretum (southern Croatia)

The microphytobenthos from the fresh water of Trsteno Arboretum consisted of 84 species, mostly diatoms (55 species). There were 15 representatives of Chlorophyceae and 10 Cyanobacteria, as well as scattered representatives of Schizomycetes, Xanthophyceae and Mycota. Five diatoms were present throughout the research period: Achnanthes affinis Grun., A. microcephala Grun.. Cocconeisplacentula Ehr., Synedra ulna Ehr., and Gomphonema dichotomum Kiitz. The maximal number of species was detected during the winter and spring, and the minimum number in autumn. The saprobic index, based on the characteristic species determined in the benthic community (ranging from 1.7 to 2.2) indicated moderate impurity

Effect of current velocity on diatom colonization on glass slides in unpolluted headwater creek

Abstract Background and Purpose: The goal of this study was to determine the effect of current velocity on diatom colonization rate during the first 30 days of artificial substrate (glass slides) exposure. Materials and Methods: From autumn 1990 to summer 1993 artificial substrates were submerged in an unpolluted mountain stream. The parallel oriented glass slides (against the surface) were placed 10 cm beneath thewater 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 collected seasonally. To define diatom colonization, a nonlinear regressive analysis of empirical data was performed. Results: A total of 71 diatom species were found. Species Cocconeis placentula, Surirella ovata, Gomphonema olivaceum, and Navicula gracilis were the most abundant, depending on different current velocity. Conclusions: The time needed for reaching the equilibrium progressively increased with the current velocity (F= 16.7; P< 0.01). In the summer and autumn, the time needed for the stabilization of diatom flora was longer than in spring and winter. Concerning species abundance, Cocconeis placentula, and Navicula gracilis were independent of the current velocity, while Surirella ovata was abundant at lower (≤30 cm s–1) and Gomphonema olivaceum at higher (≤60 cm s–1) current velocities

The first report on periphytic diatoms on artificial and natural substrate in the karstic spring Bunica, Bosnia and Herzegovina

This study presents investigations of the periphytic diatoms on artificial (glass slides) and natural substrates in the karstic, limnocrene spring of Bunica situated in the south of Bosnia and Herzegovina. Investigations were performed in summer 2010. Samples were collected every seven days for eight weeks. Physical and chemical characteristics of water, temperature, oxygen saturation, dissolved oxygen, electric conductivity and nutrients as well as flow velocity at sample site, were measured simultaneously with each sampling. Physical and chemical characteristics showed low temperature oscillations, good aeration and oligotrophic conditions. In general, greater diatom diversity was noted on natural substrate. A total of 104 diatom species were found on natural substrate and 82 on glass slides. The best represented genera on both types of substrate were Gomphonema and Navicula (each with eight species), Nitzschia (with six species), and Cocconeis (with five species). Achnanthidium exiguum, Achnanthidium minutissimum, Amphora pediculus, Cymbopleura amphicephala and Surirella minuta were recorded in all samples of natural substrate and Gomphonema minutum in artificial substrate samples

Dominantne vrste mrežnog fitoplanktona u Visovačkom jezeru, NP Krka

Species composition of the net-phytoplankton assemblage and seasonality of the dominant species were investigated in the travertine monomictic stratified riverine Lake Visovac in relation to the environmental variables. The one year investigation was based on monthly sampling from April 1995 to March 1996 at the two deepest vertical profiles, with a maximum depth of 25 m. Diatoms, especially Asterionella formosa Hass. dominated net-phytoplankton assemblages except in late summer and autumn when dinoflagellate species Ceratium hirundinella (O. F. Müller) Bergh became the dominate form. The effects of the short term dynamics of environmental factors on the algal growth in the barrage lenitic area of the calcareous river stressed several variables as important factors controlling annual net-phytoplankton distribution. Temperature was the variable that most affected species abundance, changes in dominance and species composition (Primer 5, BIO-ENV; http://www.primer-e.com/). CCA analysis performed on abundance dataset and environmental variables confirm the importance of temperature but also highlighted total phosphorus, conductivity and silica.Tijekom jednogodišnjeg razdoblja od travnja 1995. do ožujka 1996. istraživana je, u jednomjesečnim intervalima, vertikalna i sezonska distribucija mrežnog fitoplanktona u lenitičkom području Visovačkog jezera. Naglasak tijekom istraživanja bio je na sastav vrsta te povezanost dominantnih vrsta i okolišnih čimbenika. Najzastupljenija vrsta tijekom kasnog proljeća je dijatomeja Asterionella formosa Hass, dok ljeti i u jesen dominaciju preuzima dinoflagelat Ceratium hirundinella (O. F. Müller) Bergh. Od mjerenih ekoloških parametara, temperatura vode najznačajnije je utjecala na promjene u sastavu vrsta, njihovu zastupljenost i dominaciju (Primer 5, BIO-ENV). CCA analiza dobivena na osnovi zastupljenosti fitoplanktonskih stanica i praćenih ekoloških čimbenika potvrdila je znatan utjecaj temperature vode, kao i ukupnog fosfora, provodljivosti i silicija

Algal assemblages in springs of different lithologies (ophiolites vs. limestone) of the Konjuh Mountain (Bosnia and Herzegovina) - Online supplement

The biodiversity of algal communities and environmental conditions were investigated in the springs of Mt. Konjuh. The assemblages of 20 springs emerging from different lithologies (limestones and ophiolites, respectively) comprised 234 algal taxa. Diatoms and cyanobacteria were the most species-rich groups. The most common alkaliphilic, circumneutral, and eutraphentic diatoms were represented by the genera Gomphonema, Nitzschia, Navicula, Cymbella, and Achnanthidium, and by the cyanobacterial genus Phormidium. Hierarchical clustering and SIMPROF analysis based on relative algal abundance clustered springs into six groups, separating them mainly according to spring type and lithology. Indicator species for groups and springs on different lithological substrata were singled out, revealing 33 taxa with preferences for ophiolites, and 20 taxa with preferences for carbonates. The values of the Shannon-Wiener diversity index were moderately high per spring location, and similar for the two groups of springs on different lithologies. A higher similarity in species composition was noted between springs on ophiolites and limestones than between springs on ophiolites and other types of siliceous substrata. The present study suggests that algal assemblages in springs emerging from ophiolites, even those made up by a preponderance of silicates, should be analyzed separately from those related to springs on other siliceous substrata. The results obtained showed that most of the springs studied are affected by anthropogenic impacts and morphological alterations leading to the dominance of highly ompetitive meso- and eutraphentic algal species, thus emphasizing the importance of further investigation and conservation of these habitats

Microbial mats as shelter microhabitat for amphipods in an intermittent karstic spring

Microbial mats represent complex communities where cyanobacteria and diatoms as key organisms provide shelter for diverse assemblages of aquatic invertebrates, like the small stygophilous amphipod Synurella ambulans. Studies addressing such communities in the karst springs have rarely examined springheads, and have ignored intermittent springs. During high flow conditions the stygophilic crustaceans are flushed to the surface of a temporary stream Krčić where microbial mats prevent their drift and enables their successful retreat into underground in the periods of drought. The objective of this study was to characterize the microbial mat community of the Krčić Spring as a shelter for S. ambulans during strong current and high water level. Representative samples for diatom and cyanobacterial species identification and composition, as well as the fresh mat material for potential animal activity and cyanobacterial phylogenetic analysis were collected. The most dominant diatom was Achnanthidium minutissimum, whilst Fragilaria capucina, Meridion circulare, Navicula cryptocephala and Nitzschia palea had abundance greater than 0.5%. Morphological observations of cyanobacteria revealed that Phormidium favosum was the most dominant, with Hydrocoleum muscicola as a subdominant. Cyanobacterial phylogenetic relationship revealed two distinct clusters: (i) &quot;Phormidium cluster&quot;, confirming morphological observations in both winter and spring samples, and (ii) &quot;Wilmottia cluster&quot;, a first report for Croatia and found exclusively in the winter sample. Laboratory observations revealed a small stygophilic amphipod S. ambulans, hiding and feeding inside the pockets of fresh microbial mat. The intermittent Krčić Spring as a predator-free and competitor-free ecosystem provides a spatiotemporal conformity between microbial mat and stygophilous amphipod