CONICET | Buscador de Institutos y Recursos Humanos

With increasing global demand for seafood and fish, the aquatic food supply has transitioned from being primarily based on wild capture of fishes to aquaculture. Tenacibaculum maritimum is one of the most important fish pathogens in Singapore, where most marine fish farms operate open cages in coastal waters. Uneaten feed and fish feces tend to aggregate and sink to the bottom of the sea; yet little is known about its impact on sediment-based microbial communities and the ability of pathogens to prevail in sediment-based biofilms. The aim of this work was to assess the fate and transport of T. maritimum, one bacterial and one viral model organisms in sediment-water microcosms and to study the effect of macroaggregates on decay. Outdoor microcosms containing water (200 ml) and sediments (100 g) were inoculated with T. maritimum, Enterococcus faecalis and bacteriophage P22. Triplicate microcosms were spiked with either planktonic cells/phages or with target organisms attached to macroaggregates. Separate controls with unspiked seawater and unspiked macroaggregates were also included. Decay in the aqueous and sediment phases was studied for 14 days. Cultivation-based methods and real-time PCR were used to analyze cultivable cells/particles and DNA levels, respectively. Physicochemical variables (pH, turbidity, dissolved oxygen, temperature, conductivity) were also measured. Decay constants and the time for a one log reduction (T90) were calculated employing a first order decay model. These constants will be used in a mass balance model during flume experiments.Results showed that cells/particles decayed more rapidly than total DNA for all treatments and surrogates, as expected. P22 persisted the longest in both phases and remained infectious to the host organism Salmonella typhimurium during the experiment. Furthermore, target organisms in sediments showed no decay except for T. maritimum which had decay rate constant lower than those in water.