Soca River Research Articles

Morphological variation in hybrids between Salmo marmoratus and alien Salmo species in the Volarja stream, Soca River basin, Slovenia

Morphological variation in hybrids between Salmo marmoratus and alien Salmo species in the Volarja stream, Soca River basin, Slovenia

The genetic diversity of native, stocked and hybrid populations of marble trout in the Soca river, Slovenia.

The marble trout (Salmo marmoratus) is an endangered species in Slovenia (and in Italy, Croatia and Albania) because of hybridization resulting from intensive stocking. Eleven populations of trout from the Soca river basin (Slovenia) were analysed using 31 presumptive enzyme loci. Three European control samples representing the main European genotypes of brown trout were also analysed. This analysis confirmed the existence of extensive hybridization in the main river, resulting in an equal mixture of alleles belonging to marble trout, and Danubian and Atlantic brown trout (Salmo trutta). Despite the high level of introgression observed in the main Soca River, nearly pure populations of marble trout were found in the headwaters of five tributaries. The five stations with pure marble trout will be the basis of a rehabilitation programme. Hardy-Weinberg and linkage disequilibria were observed and hypotheses are discussed to explain this. A scenario for the colonization of the Adriatic region is proposed.

Mercury Biogeochemistry in the Idrija River, Slovenia, from above the Mine into the Gulf of Trieste

The Idrija Mine is the second largest Hg mine in the world which operated for 500 years. Mercury (Hg)-laden tailings still line the banks, and the system is a threat to the Idrija River and water bodies downstream including the Soca/Isonzo River and the Gulf of Trieste in the northern Adriatic Sea. A multidisciplinary study was conducted in June 1998 on water samples collected throughout the Idrija and Soca River systems and waters and sediments in the Gulf. Total Hg in the Idrija River increased >20-fold downstream of the mine from <3 to >60 ng liter−1 with methyl mercury (MeHg) accounting for ∼0.5%. Concentrations increased again downstream and into the estuary with MeHg accounting for nearly 1.5% of the total. While bacteria upstream of the mine did not contain mercury detoxification genes (mer), such genes were detected in bacteria collected downstream. Benthic macroinvertebrate diversity decreased downstream of the mine. Gulf waters near the river mouth contained up to 65 ng liter−1 total Hg with ∼0.05 ng liter−1 MeHg. Gulf sediments near the river mouth contained 40 μg g−1 total Hg with MeHg concentrations of about 3 ng g−1. Hg in sediment pore waters varied between 1 and 8 ng liter−1, with MeHg accounting for up to 85%. Hg methylation and MeHg demethylation were active in Gulf sediments with highest activities near the surface. MeHg was degraded by an oxidative pathway with >97% C released from MeHg as CO2. Hg methylation depth profiles resembled profiles of dissolved MeHg. Hg-laden waters still strongly impact the riverine, estuarine, and marine systems. Macroinvertebrates and bacteria in the Idrija River responded to Hg stress, and high Hg levels persist into the Gulf. Increases in total Hg and MeHg in the estuary demonstrate the remobilization of Hg, presumably as HgS dissolution and recycling. Gulf sediments actively produce MeHg, which enters bottom waters and presumably the marine food chain.

Možnosti nadaljnjega sonaravnega razvoja ob treh sosednjih južnoalpskih rekah: Piavi, Tilmentu in Soči

Članek prinaša glavne rezultate primerjalne študije o treh juznoalpskih rekah (Piavi in Tilmentu v Italiji ter Soci v Sloveniji), ki so si po naravnih znacilnostih zelo podobne, zaradi razlicne rabe pa se po moznostih nadaljnjega sonaravnega razvoja med seboj zelo razlikujejo, saj sta Piava in Tilment skoraj v celoti izrabljena za pridobivanje elektricne energije, Soca pa je ostala v razmeroma naravnem stanju.

Seasonal and inter-annual plankton variability in the Gulf of Trieste (northern Adriatic)

Seasonal and inter-annual variability of environmental characteristics and of plankton were analysed based on monthly surveys of the physical structure of the water column, nutrients, phytoplankton, and zooplankton biomass and abundance in the Gulf of Trieste (1989-1995). Seasonal plankton dynamics were related to Soca River run-oV, the main freshwater source, and peaks of autotrophic biomass were associated with extended periods of high freshwater inflow. Our results indicate that the freshwater discharge during spring was more important for annual phytobiomass than total yearly input. In 1993, which was characterized by a relatively high total annual freshwater input but by a dry spring, the lowest average chlorophyll biomass (0.85 Ig l 1 ) and cumulative monthly mesozooplanktonic biomass (123 mg AFDW m 3 ) were observed over the entire period. Annual peaks of phytoplankton biomass were mainly due to increases in diatom abundance, while small-sized cells (microflagellates, coccolithophores) dominated during periods of low Chl a concentrations. Consumer community patterns followed autotrophic biomass evolution with high abundance of herbivores and mixed feeders in spring, and fine-filter feeders and planktonic protists during summer. A large inter-annual variability emphasizes the importance of long-term monitoring in areas like the Gulf of Trieste for distinguishing anthropogenic trends from natural variations of plankton. ? 1998 International Council for the Exploration of the Sea

Crayfish of the Upper Soca and Upper Sava rivers, Slovenia

Crayfish biogeography of northwestern Slovenia was studied in the Upper Soca River (Mediterranean drainage) and the Sava Dolinka River (Danubian drainage). The Mediterranean drainage has white-clawed crayfish <i>(Austropotamobius pallipes)<i/> and the Danubian drainage has stone crayfish <i>(A. torrentium)<i/> . Morphological data of these <i>A. pallipes <i/> suggest that the Slovenian white-clawed crayfish belong to the <i>Austropotamobius pallipes italicus<i/> complex. The biogeographic and morphological data support the present general knowledge that in Slovenia the white-clawed crayfish belongs to a Po-Adriatic fauna and the stone crayfish to a Danubian fauna. A third species, the noble crayfish <i>(Astacus astacus)<i/>, was found in Danubian waters, but its biogeographic meaning may not be significant because the species is present in, and has been introduced into, waters of both the Mediterranean and Danubian drainages. The noble crayfish from a Slovenian lake, Blejsko jezero, has certain morphological characteristics that require additional investigations before its taxonomic position can be clarified. The stone crayfish of the Sava Dolinka now survives in only a few sites, relics of a former wider distribution destroyed by human activities. On the other hand, the white-clawed crayfish of the Soca is still distributed widely. But it is timely to consider their protection because the Soca region is now under major tourist development pressure.

Il genere Sesleria quale indicatore di fattori climatici nell’Isontino

BIOGEOGHAPH/A - vol. X/II — 1987 Biogeografia delle A/pi Sud—Orienta/i Il genere Seslez/222 quale indicatore di fattori climatici nell’Isontino VINKO STRGAR UIzz&#39;vei*5z&#39;tzid2&#39; Ljubljkzm, Dzpmfi/72e1zt0 dz‘ Biologizz della Facoltci Bz&#39;0tecm&#39;ca e Istzmto di Biologzkz delZ’U72z&#39;vem&#39;tz2 SUMMARY We deal with the central Posoeje in a submediterranean vegetation regione approximately between the towns of Solkan and Plave, which lie in—between Gorica and Tolmin. The area is about 9 km long and 2 to 4 km wide. The lowest point is 60 m above sea level in the valley of the Soca river and the highest is 609 rn above sea level on the top of Sabotin. The Sofia flows here across the last kilometres of a narrow valley which is squeezed between 682 m high Sv. Gora (Skalnica) in the northeast and 609 m high Sabotin in the southwest. The habitats are rocky or stony, consisting of dolomite or limestone. Due to the special geographical situation of the area and its extreme orographical diversity, there are Considerable differences in microclimatic conditions here. The influence of a warm mediterranean climate from the sea about 20 km away spreads from the west and the south. There is the influence of a cold alpine climate coming from the north as well. Besides warmth, air humidity is also an important factor here: it is specially high in the gorge of the Soca, on the northwestern hillside of the mountains above the 50521 and on their ridges. Each climate has a prevailing influence at the extreme points: the rnediterranean one on the ridge and hillsides of Sabotin, the alpine one in the Soea valley. The characteristics of an intermediate climate are very obvious on the ridge above Plave northwest of Sabotin. Because of the temperature inversion the highest temperatures are on the ridge and hillsides of the higher regions of Sabotin, which is under the strongest mediterranean influence. For the same reason the lowest temperatures are in the Soca valley where cold air is retained. Intermediate conditions occur in the ridge and hillside above Plave, wich are a little farther from the warm Mediterranean and from the cold Soca valley. Four species of genus Serlerizz grow in this area. Serleria am‘zz/mzalis (Scop.). F. W. Schultz from the section Argenteae and S. kalzzziee/zsir ]av., S. mzgz/rtzfolia (Hackel et Beck) Deyl and S. zzlbiamr Kit. (=S. mzria Jacq.) from the section Calcariae. The species S. azt/zz/27/mlis is a thermophyle one with different requirements than the other three species regarding air humidity and it is not to be compared with the others. That is the reason why we do not deal with S. azztz//zzmzlir here. The knowledge of the general spread of the other three species shows that the most thermophyle species is S. lzalzzilaeizrir, S. albiczz/2: is non-thermophyle and S. mzgzz.rtz_&#39;fo[z&#39;a fits somewhere in-between. All three species require humid air for good growth. They cannot be differentiated regarding air humidity. The geographical spread of the three named species of the genus Sexleria in the central Posocje matches very well with their generally known thermal requirement. The most demanding species concer- ning warmth is S. /ealzzzkeizsis, which overgrows the ridges of Sabotin and their northeastern hillside (above the Soca) from an altitude of approximately 200 m above sea level up to the top of the ridge. The least demanding species regarding warmth is S. albzbaizr, which overgrows rocks and stony habitats in the Sofia valley up to an altitude of approximately 150 In above sea level. S. aizgz/rhfolzkv, which is an interme- diate species concerning warmth, grows on the ridge and hillside above Plave. INTRODUZIONE Si desume dal titolo che dalla distribuzione delle specie del genere Sexle- rzkz dovremmo venire a conoscenza d1 dati concreti in rnerito alle condizioni 411