The feeding habits of sand smelt, Atherina boyeri Risso, 1810 in the mouth of the Mala Neretva River were studied by examining the stomach contents of 1236 fishes collected from March 2001 to ...February 2002. Thirteen different food categories were identified. The greatest diversity was recorded in winter, especially in January, when 11 categories were present. The minimum (4) was in September, and was associated with the highest number of empty stomachs. Marine and estuarine species represented the bulk of the prey, while typically fresh-water species (Daphnia spp. and Cyclops spp.) were found only sporadically. Crustaceans were the most common prey and, of these, the most common were copepods (45%), followed by grammarid amphipods (34%), cladocerans (13%), decapod larvae (12%) and mysids (8%). Insects represented 7%. The percentage number of prey showed high seasonal variations. Copepods dominated in autumn and winter, cyclopoids in April, poecilostomatoids and harpacticoids in December, and calanoids in January and February. Decapod larvae dominated in March-May, and mysids in July-August. PCA and clustering analysis was performed on the prey data in order to reveal associations between prey items or seasonal similarities. The opportunistic mode of feeding of the species Atherina boyeri is also discussed.
In this study, the diatoms of three alternative habitats (epilithon, epiphyton and artificial sub-strate) were compared to understand the differences in composition on artificial and natural ...sub-strates. For this purpose, the samples were collected weekly between 11th August and 2nd Septem-ber 2016 at a sampling site in a shallow marine lake, Mrtvo More (Dead Sea) on Lokrum Island near Dubrovnik (South Adriatic, Croatia). In addition to detailed light microscopic analysis, ultrastructural analysis of benthic diatoms from Lake Mrtvo More was performed for the first time using scanning electron microscopy (SEM). A total of 97 taxa were identified in 12 samples. Cocconeis scutellum Ehrenberg and Halamphora coffeiformis (C.Agardh) Levkov were the most frequent taxa in the samples. Shannon-Wiener diver-sity index (H’) values varied from 1.78 (in September on Padina sp.) to 4.52 (in August on glass). According to non-metric multidimensional scaling ordination, there were two groups: epilithon and artificial glass substrate as Group1 and macroalgae as Group2. The results of the analysis showed that the diatom communities developing on artificial sub-strates accurately correspond to the diatom community of a rock substrate and thus can be used as a representative alternative tool for studies of epilithic diatoms in further experiments.
Kako bi se razumjele razlike između naseljavanja na umjetnim i prirodnim podlogama, u ovom istraživanju uspoređivani su sastavi dijatomeja s tri alternativna staništa (epiliton, epifiton i umjetni supstrat). U tu svrhu uzorci su sakupljani tjedno između kolovoza i rujna 2016. na jednoj lokaciji u plitkom morskom jezeru Mrtvo More na otoku Lokrumu kod Dubrovnika (Južni Jadran, Hrvatska). Osim detaljne analize svjetlosnim mikroskopom, po prvi put je provedena i ultrastrukturna analiza bentoskih dijatomeja iz jezera Mrtvo More pomoću elektronske mikroskopije (SEM). U 12 uzoraka identificirano je ukupno 97 vrsta dijatomeja. Vrste Cocconeis scutellum Ehrenberg i Halamphora coffeiformis (C.Agardh) Levkov bile su najčešće vrste u uzorcima. Vrijednosti Shannon-Wiener (H’) indeksa varirale su od 1,78 (u rujnu na vrsti Padina sp.) do 4,52 (u kolovozu na staklu). Prema nMDS ordinaciji, razlikuju se dvije skupine zajednica bentoskih dijatomeja: epiliton i umjetna staklena podloga kao Grupa 1 i makroalge kao Grupa 2. Rezultati analize pokazali su da zajednice bentoskih dijatomeja koje se razvijaju na umjetnim podlogama, odgovaraju dijatome-jskoj zajednici kamene podloge i da se stoga mogu koristiti kao reprezentativni alternativni alat za proučavanje epilitskih dijatomeja u daljnjim eksperimentima.
The initial colonization of bacteria and diatoms on a immersed artificial substrate and the development of diatom assemblages in relation to physico-chemical parameters were investigated on a weekly ...basis at one station in the marine Lake Mrtvo More, South Croatia, from April to October 2016. According to TRIX trophic index, lake showed different trophic character: (i) oligotrophic (at the beginning and the end of the study), (ii) mesotrophic (the end of June to mid-July), (iii)
eutrophic (the end of July to mid-September). Heterotrophic bacteria increased to peak abundances (69,268 cells cm–2) at the beginning of June when the diatoms abundances start to increase. The lake has high diatom species richness (285 diatom taxa within 72 genera), with the highest species diversity index in August. Among diatoms, adnate were the primary colonizers, particularly Cocconeis dirupta W.Gregory var. flexella (Janisch and Rabenhorst) Grunow and Cocconeis scutellum Ehrenberg var. scutellum, while motile taxa joined the fouling communities from July to September. This study showed close relationship
between diatom species composition and changes of physico-chemical parameters, particularly the nutrient concentrations.
The aims of this paper were to describe seasonal changes in the qualitative and quantitative composition of diatom taxa and the potential application of benthic diatoms for ecological status ...evaluation. Diatom indices (IPS and TI) were calculated from data from three different locations along a longitudinal profile of the Bunica, a small karstic river in Bosnia and Herzegovina. A total of 147 taxa were recorded in 12 samples. The most common taxa were Meridion circulare (Greville) C.Agardh and Ulnaria ulna (Nitzsch) Compère. Physical and chemical analyses showed low concentrations of nutrients, good oxygenation, typical pH for carbonate bed/origin and generally oligotrophic conditions and high ecological status. All sites had similar physico-chemical conditions and there were only few seasonal differences. Ordination of the diatom data showed that samples showed neither longitudinal nor seasonal patterns. Median value for IPS (16.8) and for TI (7.3) can be possible ‘‘expected’’ values for ecological status assessment for small karstic rivers in the Mediterranean region. We propose the use of the phytobenthos Intercalibration Common Metric (pICM - an index that combines the IPS and TI) as a national metric for countries developing WFD diatom methods at a late stage. One situation is described, and a solution, which is potentially transferable to other
locations in Bosnia and Herzegovina and also to other countries facing similar challenges.
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
,
,
,
, and
, and by the cyanobacterial genus
. 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.
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 fl ow 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.
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