The environmental DNA (eDNA) has been adopted as a tool for biodiversity studies in marine and fresh waters. However, to evaluate marine community composition avoiding false assignments, eDNA dynamics and transport must be considered. We investigated the level of Salmo salar (Atlantic salmon) DNA transport in two sites selected in a bay in the West of Ireland, and seawater was sampled in early November 2023. Site A was in an aquaculture site around a cage hosting 20000 adults of S. salar; site B was on a rocky beach 500 m far from the cages. 5L of surface water was filtered on 0.45 μm mixed cellulose ester (MCE) and 2 μm glass fiber (GF) filters in triplicates. At the same time, a metaprobe (Maiello et al, 2022) was deployed on both sites in duplicates to compare active and passive sampling. DNA from filters and roll-gauzes was extracted with Blood & Tissue (B&T) and Power Water (PW) kits (Qiagen). The DNA library was prepared with a two-steps PCR targeting the 12s rRNA gene. Samples were pooled after indexing, and sequenced on MiSeq Illumina (2X250PE). The demultiplexed sequences were processed with the ObiTools pipeline launched in Galaxy.eu. S. salar DNA was detected in site A successfully in MCE and roll-gauzes extracted with both B&T and PW kits and in GF filters extracted with B&T. The Relative Reads Abundance (RRA) of the Atlantic salmon averaged 81% due to its high abundance in the area. Conversely, only 16% RRA was observed in site B for a replicate of the MCE filter extracted with B&T, while no records were reported from other filters and roll-gauzes. Therefore, one could hypothesize that B&T extraction method is more sensitive, but further investigations are needed. This study suggests that despite the large presence of S. salar in the study area, the DNA decreased significantly at only 500 m from the source. Considering this, eDNA transport should be investigated further by sampling at intermediate distances from the source at different tidal conditions.
How far can eDNA travel into marine waters? Dynamics revealed by opportunistic water sampling
Giulia Mariani;Ludovica Di Renzo;
2024-01-01
Abstract
The environmental DNA (eDNA) has been adopted as a tool for biodiversity studies in marine and fresh waters. However, to evaluate marine community composition avoiding false assignments, eDNA dynamics and transport must be considered. We investigated the level of Salmo salar (Atlantic salmon) DNA transport in two sites selected in a bay in the West of Ireland, and seawater was sampled in early November 2023. Site A was in an aquaculture site around a cage hosting 20000 adults of S. salar; site B was on a rocky beach 500 m far from the cages. 5L of surface water was filtered on 0.45 μm mixed cellulose ester (MCE) and 2 μm glass fiber (GF) filters in triplicates. At the same time, a metaprobe (Maiello et al, 2022) was deployed on both sites in duplicates to compare active and passive sampling. DNA from filters and roll-gauzes was extracted with Blood & Tissue (B&T) and Power Water (PW) kits (Qiagen). The DNA library was prepared with a two-steps PCR targeting the 12s rRNA gene. Samples were pooled after indexing, and sequenced on MiSeq Illumina (2X250PE). The demultiplexed sequences were processed with the ObiTools pipeline launched in Galaxy.eu. S. salar DNA was detected in site A successfully in MCE and roll-gauzes extracted with both B&T and PW kits and in GF filters extracted with B&T. The Relative Reads Abundance (RRA) of the Atlantic salmon averaged 81% due to its high abundance in the area. Conversely, only 16% RRA was observed in site B for a replicate of the MCE filter extracted with B&T, while no records were reported from other filters and roll-gauzes. Therefore, one could hypothesize that B&T extraction method is more sensitive, but further investigations are needed. This study suggests that despite the large presence of S. salar in the study area, the DNA decreased significantly at only 500 m from the source. Considering this, eDNA transport should be investigated further by sampling at intermediate distances from the source at different tidal conditions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
