Marko Miliša

Seasonal and fine-scale spatial drift patterns in a tufadepositing barrage hydrosystem

We examined seasonal patterns of drifting macroinvertebrates, and transported moss and (in)organic particulate matter at a fine spatial scale within the tufa-depositing barrage hydrosystem of Plitvice Lakes, Croatia. Samples were collected at six sites along a stream reach during autumn, winter, spring and summer. The sampling sites differed in flow velocity, depending on their position within the study reach and distance from tufa barriers and associated waterfalls. Seasonality was pronounced for most physico-chemical measurements. The highest concentrations of transported (in)organic particulate matter, being related to increased amounts of moss in transport, were observed in autumn. Drift densities were highest at tufa barriers that had higher flow velocities. Drift abundance partially followed the seasonal pattern in transported (in)organic matter. Autumn peaks in drift of Oligochaeta, Coleoptera as well as some Diptera and Trichoptera were related to increased moss and particulate matter quantities, while observed increases in drifting Nematoda, Cladocera, Copepoda, Ephemeroptera, Simuliidae and Chironomidae in spring and summer were probably due to distribution shifts of larvae or to higher seston levels originating from the upstream lake. Although we found that faster flowing stream sites generally had higher drift densities, there typically was no significant correlation between flow velocity and the amount of drift. Therefore, our expectation that fine-scale spatial drift patterns primarily depend on flow differences between lotic habitats was not supported for this system. The positive correlation between transported moss and other measured drift parameters, both at the seasonal and fine spatial scale, suggests that drift patterns were influenced by trapping/refuge efficiency of moss-covered tufa substrate and respective seasonal changes in instream vegetation (moss) as linked to hydrochemistry and water temperature.

Simuliid silk pads enhance tufa deposition

Simuliid silk pads and their effect on tufa deposition and biofilm development with respect to current velocity and time of exposure have been studied during the winter on tufa barriers in Plitvice Lakes (Croatia). Analysis of silk pad types on artificial substrates showed that moderate velocity substrates were slightly more favourable for simuliid larvae as landing attachment site, while they strongly preferred high velocity substrates as wandering attachment sites and exclusively as long term attachment sites for feeding. Although silk covered only 0.78% of surface area on glass slides, it accumulated 17% of diatoms and 56% of individual calcite crystals under moderate velocity conditions and 13% of diatoms and 41% of individual calcite crystals under high velocity conditions, thus proving that silk influence periphyton development and serves as biomediator in early stages of tufa formation. Diatom and calcite densities were mainly functions of time, with higher densities of both under moderate velocity. Maximum dimension of calcite crystals wasn’ t affected by the two month time of exposure, with larger crystals found under moderate velocity. We conclude that low winter temperature inhibited intensive calcite precipitation so tufa deposition during winter time happened mainly by trapping and binding microcrystalline calcite. Increased current velocities resulted in a poorer periphyton development and a lesser accumulation of calcite crystals.

Destructive effect of quarry effluent on life in a mountain stream

Quarrying is a widespread method for acquiring construction material. The studies of quarrying effects to date have been conducted mostly in the fields of geology, (hydro)geochemistry and landscape management while ecological studies on effects of quarrying are surprisingly few. The goal of this study was to assess some ecological effects of quarry mining on mountain stream habitats. The study was performed at Bistra Stream on Medvednica Mountain in NW Croatia. The quarry is located 3 km downstream from the spring. Samples were taken at four sites on four dates during the spring of 2006. Standard physico chemical parameters were measured and triplicate benthos samples were taken using a 30 × 30 cm Surber sampler. Turbidity, pH and temperature increased significantly downstream of the quarry. All biocenotic descriptors decreased significantly downstream of the quarry including total taxa (by 60%), total number of individuals (by 85%), diversity index (by 56%). The most important cause of such changes in the macroinvertebrate assemblage structure was the change in pH and turbidity. The magnitude of changes in the macroinvertebrate assemblage structure was due to the extremely long duration of disturbance. However, we believe that the recovery of aquatic assemblages, upon closure of the quarry, would be fast and successful because of nearby streams that may serve as a recolonizing source.

The structure and ultrastructure of the egg capsule of Brachyptera risi (Plecoptera, Nemouroidea, Taeniopterygidae) with some remarks concerning choriogenesis

The organization of the egg capsule of the euholognathan stonefly, which represents the family Taeniopterygidae (Nemuroidea) was investigated using light and electron microscopy techniques. The presence of a complex, multilayered egg capsule, composed of a vitelline envelope, multilayered chorion, and extrachorion is described. The morphology of the eggshell of Brachyptera risi was compared with that of euholognthan and systellognathan egg coverings and the ground plan of the egg capsule in Plecoptera was discussed. Microsc. Res. Tech. 78:180–186, 2015.

Author Correction: A global analysis of terrestrial plant litter dynamics in non-perennial waterways

In the version of this Article originally published, the affiliation for M. I. Arce was incorrect; it should have been: 5Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany. This has now been corrected in the online versions of the Article.

The structure and ultrastructure of the egg capsules of stoneflies of the genus Isoperla (Insecta, Plecoptera, Perlodidae)

The egg capsules of five systellognathan stoneflies species representing the genus Isoperla (Plecoptera, Perlodidae) have been investigated using light and electron microscopes (SEM and TEM). We consider the structural modifications of egg coverings (egg capsules, eggshells) like: a shape of a capsule, presence of structures fixing an egg to the substratum under water, intrachorionic aeropylar system facilitating gas exchange as a factor adapting an egg/embryo to the environment. The structures protecting eggs against desiccation during a female flight before oviposition into water as well as against the dangers of external mechanical injury caused by turbulences in rapid water currents of mountain streams are described and discussed. The ground plan of the egg capsule in arctoperlarian stoneflies is also discussed.

Response of aquatic protists to electric field exposure

Abstract Purpose: To test the effects of short-term exposure of aquatic organisms to electric field (EF) with negligible magnetic component. Materials and methods: We built a plate capacitor that served as a source of EF of strengths that can be found in nature near transmission lines. We exposed two cultured protist species Euglena viridis and Paramecium caudatum to EFs for 24 hours and monitored their abundance, morphology, intracellular superoxide anion (by dihydroethidium [DHE]), hydrogen peroxide by (H2DCF) and lipid peroxidation (MDA) contents, catalase (CAT) and superoxide dismutase (SOD) activity. Results: We found that even short-term exposure to low strength EF causes changes in population abundance, morphology and oxidative stress response in both species. As the EF strength increased, abundance of both species decreased. However, at weaker EFs, fission rates were seemingly promoted. We noted a decrease in size in both organisms in directions perpendicular to their fission planes correlated with EF strength. DHE and H2DCF fluorescence intensity and SOD activity were higher in organisms exposed to the stronger EFs. Conclusions: We suggest that the electric component of the field, rather than the magnetic, is the main cause of all the noted effects. As a result, aquatic organisms should be given greater importance in studies assessing the effects of EMFs in spite of the attenuating effects of water to EF strengths.