Abstract

A multidisciplinary approach was used to study the impact of fish farming

on coastal bacterial communities in the inner part of the Bay of Piran (northern

Adriatic). Differences in bacterial abundance, production and the occurrence of selected

bacterial groups were studied in the water column around the cage and at different

distances from the centre of the fish cage towards the open water, i.e., reference marine

station. We also examined the effect of fish feeding on the surrounding system

in a short-term in situ experiment based on the simultaneous collection of seawater

samples from different locations around the fish cage before and after feeding of

fish. Our study suggests that fish feeding has a moderate short-term effect on water

column parameters, including bacterial abundance and production, only at a limited

distance from the fish cages. The nitrifying, ammonia-oxidizing bacterial groups, as

determined by the fluorescent in situ hybridization method, were represented at a

higher percentage in the seawater samples in the middle and around the fish cages.

β- Proteobacteria , γ- Proteobacteria and the Cytophaga-Flavobacterium group were

represented to a higher percentage at sampling sites in the middle of the Bay of Piran

and at the reference marine station. The Vibrio group was detected at all sampling

sites. The accumulation of organically enriched fish food and waste products released

into the seawater during the short-term experiment resulted in a significant increase

in particulate matter, orthophosphate and ammonium. In response to the increase in

inorganic nutrients, we observed a significant increase in bacterial production, while

no significant differences were observed in bacterial abundance in such short time.

Keywords

aquaculture, bacterial abundance, bacterial community composition, bacterial production, fluorescent in situ hybridisation, pollution

Abstract

Authors present data regarding the presence of the invasive blue crab

Callinectes sapidus Rathbun, 1896 (Brachyura: Portunidae) based on records gathered

from local fishermen. This alien species was firstly recorded in Slovenian coastal

waters in March 2019 and it was subsequently found in six other cases in 2019, 2020

and 2021. Crabs were collected or sighted in shallow coastal areas along the Slovenian

coast. In addition, authors discussed about the status of the blue crab in marine and

coastal habitats of Slovenia.

Keywords

Adriatic Sea, Callinectes sapidus Rathbun, 1896, invasive species, presence, Slovenia

Abstract

In many European counties artificial underwater reefs (AUR) are well

established means to increase local biodiversity. In Slovenian part of Adriatic Sea the

idea of establishing an artificial reef system was first brought to light 25 years ago. So

far, despite strong evidence on the benefits to the local environment and biocenosis

brought by AUR in the Italian part of Gulf of Trieste, due to various reasons we are

still waiting for the first AUR in Slovenian part of Northern Adriatic Sea. We believe

that such a structure would be an important center for the repopulation of local habitats

after mass mortality due to the hypoxic or anoxic conditions that occasionally occurs

at the benthic communities.

Keywords

artificial underwater reef, benthos, biocenosis, hipoxy, repopulation

Abstract

A specially constructed enclosure in the lagoon environment (Lagoon of

Strunjan, Gulf of Trieste, northern Adriatic Sea) received sewage daily while another

was kept clean and used as a reference. Nutrients and community production changes

were monitored approximately bimonthly over a year. Nutrients introduced by the

sewage discharges and diluted by tides were immobilized by enhanced community

production, in particular benthic macroalgae. The dead organic matter afterwards

settled and decomposed producing anoxic conditions and high levels of dissolved and

suspended organic nutrients in the water and total nitrogen in the sediments. The daily

mean gross community production showed no quantitative differences between the

two enclosures during the study. Differences arose in the temporal succession of the

studied events. An intensive nutrient recycling emerged from this study.

Keywords

carbon, lagoons, nutrients, northern Adriatic, oxygen, production