The role of biofilms as potential environment reservoir for pathogens in marine aquaculture is unknown. Biofilms are assemblages of microbial cells that are enclosed in a self--produced matrix of extracellular polymeric substances (EPS). Here, it is proposed that biofilms in marine sediments can act as a reservoir for the retention of aquaculture-related pathogens. We used laboratory based flumes to simulate the sediment-water interface and introduced model microorganisms such as the fish pathogen, Tenacibaculum maritimum and a surrogate fecal indicator, Enterococcus faecium, to conduct a fate and transport study.
The abundance of T. maritimum and E. faecium in sediments was determined by quantitative polymerase chain reactions (qPCR) while their viability in the sediments over time was determined by propidium monoazide qPCR (PMA-qPCR) and Enterolert, respectively. Viable T. maritimum was only detected in sediments from 1 h to 10 h after spiking (Figure 1a). In contrast, viable enterococci were still detected after 24h (Figure 1a). Abundance of T. maritimum remained relatively constant from 1h to 24h followed by a 3-log reduction by Day 3 (Figure 1b). Levels of T. maritimum after Day 3 fell below the qPCR detection limit. Unlike T. maritimum, E. faecium only demonstrated a 2-log reduction from Day 0 to 21 in the spiked flumes. The inability of T. maritimum to persist for prolonged periods in sediments suggests that fish infections related to T. maritimum are unlikely to originate from sediments.