Izvorni znanstveni članak
IMPACT OF SALMON FARMING ON WATER QUALITY
Damir Kapetanović
; Institut Ruđer Bošković, Zagreb, Hrvatska
Marija Tomec
; Institut Ruđer Bošković, Zagreb, Hrvatska
Emin Teskeredžić
; Institut Ruđer Bošković, Zagreb, Hrvatska
Zlatica Teskeredžić
; Institut Ruđer Bošković, Zagreb, Hrvatska
Sažetak
Aquaculture production is undergoing a rapid expansion including an increasing interest and concern for their potential impact on the environment. Salmon fish farming releases a substantial amount of organic matter in to the water. High protein fish food and fish excretion affecting the quality of water used in fish farming. Bacteria play the major role in decomposition of the organic matter. Excessive enrichment of nutrients leads to oxygen depletion in the oxidation of the organic matter. Such conditions have negative effects on aquatic environment. The aim of this study was to estimate the impact of salmon farming on the water quality, on the basis of bacterial population and phytobenthos monitoring in relation to physico-chemical water characteristics (temperature, dissolved oxygen, pH etc.).
The investigation was carried out on a rainbow trout fish farm with an annual trout production of 100 tons, and water flow of 300 l/s. Water samples for microbiological and phytobenthos analyses were collected at eight locations. Physico-chemical parameters were measured by an electrosonde at the same time. Sampling locations were determined to include all stages of salmon production: entry to the fish farm, four locations on the fish farm at different stages of salmon production, outflow from the fish farm, and locations upstream and down stream from the fish farm. Water samples for the heterotrophic bacteria enumeration (cfu) were serially diluted with Ringer solution pH 6.0 (Pliva) and inoculated by spread plate method on the solid medium according to EN ISO 6222:1999. After
incubation at 22 °C for five days colonies were counted and results expressed for 1 ml of water (cfu/ml). Samples for benthos analysis were collected in the bottles and conserved with 4 % formaldehyde. Samples were examined under ‘’Opton’’ light microscope with magnifications 12.5x10; 12.5 x 25 and 12.5 x 40 in the laboratory. Relative phytobenthos assemblage determination from 1 to 7 was performed according to Knöpp (1954), and saprobity measures of indicators species according to Wegl (1983). Index of saprobity was determined according to Pantle-Buck (1955). Examined locations were classified according to ‘’Uredba o klasifikaciji voda’’ (1998) on the basis of the obtained water quality values. Physico-chemical water characteristics were without significant differences on examined locations. Density of the heterotrophic bacteria showed progressive changes on the locations within the fish farm which was consistent with nutrient enrichment. The most frequent species in the phytobenthos were diatoms and Bacillariophyceae, which are typical forms of phytobenthic community. More than 50 % of all determined species belonged to saprobity indicators. Indicator species were characteristic for oligosaprobic and betamesosaprobic water. Saprobity indexes were 1.7 at locations upstream and downstream of the fish farm. At the escit from 2nd and 3rd pool, with consumer fish, saprobity indexes were 1.8. These the values of P-B saprobity index indicate first and second degree water quality of the examined locations. The results of these microbiological and phytocenological examinations lead to the conclusion that fish production has insignificant local impact on the water quality.
Ključne riječi
rainbow trout; water quality; bacteria; phytobentos
Hrčak ID:
26473
URI
Datum izdavanja:
21.12.2006.
Posjeta: 1.924 *