Do benthic diatom assemblages reflect abiotic typology: a case study of Croatian streams and rivers

Benthic diatoms are widely used in Europe and worldwide to access ecological status of running waters. One of key goals of Water Framework Directive is to classify rivers and streams using biological quality elements and type specific reference conditions. According to system B which incorporates additional abiotic descriptors, there are 24 water types in Croatia. For biological analyses 92 rivers and streams with 140 sampling points were chosen and sampled for benthic diatoms and water chemistry simultaneously. Self organizing map (SOM) analysis was used to define biotypes from species composition and abundance of benthic diatoms. Grouping of samples in SOM resulted in 10 distinctive groups. Based on their geographical position and site characteristics, groups represent sites with similar properties (as waterbed, catchment size, altitude, size of stream) belonging to different ecoregions in Croatia. Analysis of variance revealed statistically significant differences (p<0.05) among SOM groups concerning ammonia, nitrates and total phosphorus. Indicator species analysis (IndVal) singled out species that were significantly characteristic (p<0.05) for SOM and abiotic types. Compared to abiotic groups, in which 7 out of 24 have no indicator species, all SOM groups have one or several characteristic diatom species, thus indicating diatom assemblages as valuable site descriptors. Canonical analysis of principal coordinates analysis also indicated that SOM grouping of samples is statistically reliable. Grouping of similar sites, although placed into different abiotic types, makes SOM groups with its corresponding representative species an easy tool for water quality assessment and description of reference assemblage

Use of Kohonen self organizing maps (SOM) for the characterisation of benthic diatom associations of the River Danube and its tributaries

Benthic diatom flora of the River Danube was investigated along the river from the source streams to the end of the Hungarian stretch during a four-year period. Characteristic diatom community assemblages were established using Kohonen Self-Organizing Map (SOM) algorithm. We found five sample clusters, arranged according to the location. The first three groups are located in the German-Austrian stretch, while the fourth and fifth groups are located in the Slovakian-Hungarian stretch. Characteristic species of the clusters 1 and 2 are Achnanthidium minutisimum (KÜTZ.) CZARNECKI, Denticula tenuis KÜTZ., Nitzschia fonticola GRUN., Psammothidium bioretii (GERMAIN) BUKHT. and ROUND, Melosira varians AG., Planothidium subatomoides (HUST.) BUKHT. and ROUND, character species of cluster 3 is Amphora pediculus (KÜTZ.) GRUN., while character species of the clusters 4 and 5 are Nitzschia dissipata (KÜTZ.) GRUN., Navicula cryptotenella LANGE-BERT., Cocconeis placentula var. euglypta (EHR.) GRUN., Rhoicosphenia abbreviata (AG.) LANGE-BERT., Nitzschia inconspicua GRUN. This arrangement is also well in agreement with the poorer water quality of the lower, and the better water quality of the upper stretch

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

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 competitive meso- and eutraphentic algal species, thus emphasizing the importance of further investigation and conservation of these habitats

Periphyton-based water quality analysis of a large river (River Danube, Hungary): exploring the potential of molecular fingerprinting for biomonitoring

Water quality monitoring based on microscopical analysis of periphytic algae is fundamental to the European Water Framework Directive. However, the outcome of this kind of monitoring is often dependent on the experience of the operating taxonomist and the availability of an electron microscope for fine-scale taxonomic analysis. Furthermore it is hampered by the insufficiencies of the morphology-based diatom taxonomy. Molecular fingerprinting methods have the potential to evade these problems and serve as a complementary tool in biomonitoring studies. To test this concept, periphyton of the River Danube was monitored for a period of six months using microscopical and molecular fingerprinting (terminal restriction fragment length polymorphism) methods in parallel. We identified 120 diatom taxa by light and electron microscopy and diatom-based water quality using Omnidia Version 4 software was found to be good or moderale (IPS value between 12 and 16). The number of operational taxonomic units identified by terminal restriction fragment length polymorphism analysis of the 18S rRNA gene ranged from 7 to 29 for individual samples, and was in total 88 in the MspI digest and 33 in the RsaI digest. The results of both analyses were compared by hierarchical classification and we found good correlation between the two methods. We propose, that after further development of molecular databases and methodology, molecular fingerprinting may have the potential to be implemented for routine biomonitoring purposes

Importance of acidic phosphatase activity in P supply and Gonyostomum semen Ehrenbergh (Raphidophyta) occurrence in a Hungarian peat bog, Keleméri Kis-Mohos (Ne Hungary)

Phosphatase enzymes are capable of releasing phosphate through cleavage of phosphoester bonds. The seasonal importance of this process was examined by using a model substrate paranitrophenylphosphate and the Michaelis-Menten equation to estimate the release rate of PO4-P from phosphomonoesters. The seasonal occurrence of phosphomonoesters and acid phosphatase activity was used to estimate the velocity of phosphate release from these compounds. Filter fractionation of phosphatase activity demonstrated that most activity (>60%) was in size fractions less than 0.45 μm. The release rates were highest in May and June (15 to 25 nmol L–1 min–1) during the Gonyostomum semen (Raphidophyta) bloom and decreased to less than 2 nmol L–1 min–1 in two weeks and remained low throughout the summer and the fall. Fractionation of 32P-H3PO4 labelled dissolved organic phosphorus showed this fraction to vary considerably through the year. Potential phosphate release declined through the summer and into the fall. Significance of the co-occurrence of phosphomonoesters and acid phosphatase activity maxima and Gonyostomum semen (Raphidophyta) bloom is discussed