Distribution of Pseudomonas fluorescens and Aeromonas hydrophila Bacteria in a Recirculating Aquaculture System during Farming of European Grayling (Thymallus thymallus L.) Broodstock

Katarzyna Glińska-Lewczuk,Iwona Gołaś,Jacek Potorski,Anna Gotkowska-Płachta,Mariusz Szmyt,Michał Łopata

doi:10.3390/w11020376

Katarzyna Glińska-Lewczuk, Iwona Gołaś + Show 4 more

Open Access

https://doi.org/10.3390/w11020376

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Journal: Water	Publication Date: Feb 21, 2019
Citations: 22	License type: CC BY 4.0

Affiliation: University of Warmia and Mazury in Olsztyn

Abstract

Pseudomonas fluorescens and Aeromonas hydrophila bacteria are opportunistic pathogens that occur naturally in the aquatic environment and in the gut flora of healthy fish. Both species can pose a serious threat for fish that are highly sensitive to water pollution. The aim of this study was to determine the extent to which the amount of administered fish feed and fish biomass affect the distribution and abundance of Ps. fluorescens and A. hydrophila bacteria in a recirculating aquaculture system (RAS) during farming of European grayling (Thymallus thymallus L.) broodstock. A total of 68 water samples from the inflow, two rearing tanks and the outflow as well as 17 feed samples were collected and analyzed separately. Bacterial populations were analyzed by the culture-dependent method and a molecular method (fluorescence in situ hybridization, FISH) to detect culturable strains and viable but non-culturable strains, respectively. Fish biomass, feed and 16 water quality parameters (temperature, pH, concentration of dissolved oxygen, oxygen saturation, five-day biochemical oxygen demand (BOD5), total phosphorus, total organic phosphorus and nitrogen, orthophosphates, total nitrogen, nitrite and nitrate nitrogen, ammonia nitrogen, ammonium nitrogen, total suspended solids, and total organic carbon) were the explanatory factors. Statistically significant differences (RM-ANOVA, p ≤ 0.05) were stated in bacterial abundance in samples from the inflow, rearing tanks and the outflow. Water samples from the RAS were abundantly colonized by non-culturable Ps. fluorescens and A. hydrophila bacteria. Feed was not a source of bacteria, but a redundancy analysis (RDA) revealed that the amount of feed, fish biomass, BOD5, and total suspended solids and total organic carbon were positively correlated in both Ps. fluorescens and A. hydrophila. These parameters also influenced the distribution of both potentially pathogenic bacterial populations and contributed to the bacterial contamination of water in the RAS. Our results are particularly valuable for aquacultures that help to replenish wild stocks and rebuild populations of threatened species in natural aquatic environments.

Highlights

IntroductionIn most commercial recirculating aquaculture system (RAS), the safety of the production process and the well-being of fish and other aquatic organisms is controlled based on the physicochemical parameters of water (temperature, pH, and oxygen and ammonia content) and the growth performance of fish (body weight gain, relative growth rate, relative biomass, and changes in total body length)
In most commercial recirculating aquaculture system (RAS), the safety of the production process and the well-being of fish and other aquatic organisms is controlled based on the physicochemical parameters of water and the growth performance of fish
The counts of Ps. fluorescens and A. hydrophila bacteria determined with the use of culturedependent and culture-independent methods had mainly relationships with the amount of feed administered to European graylings (Thymallus thymallus L.), fish biomass and increasing water pollution (BOD5, total suspended solids (TSS), and total organic carbon (TOC) concentrations) in the RAS

Summary

Introduction

In most commercial RAS, the safety of the production process and the well-being of fish and other aquatic organisms is controlled based on the physicochemical parameters of water (temperature, pH, and oxygen and ammonia content) and the growth performance of fish (body weight gain, relative growth rate, relative biomass, and changes in total body length). The significance of microbiological analyses of the aquatic environment, aquatic organisms, and feeds is often under-appreciated. Microbiological assays are not performed even when the first worrying physical or behavioral symptoms are observed in aquatic organisms. This negligence often stems from the lack of awareness that aquatic microbiota can have a greater influence on the health and growth of fish than feed microbiota [1,2,3]. From the environmental and epidemiological point of view, the increase in the abundance and activity of heterotrophic and potentially pathogenic microbiota in aquatic environments can pose a serious threat for human and animal health [4,5,6]

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