Modeling characterization of the vertical and temporal variability of environmental DNA in the mesopelagic ocean

Abstract

Increasingly, researchers are using innovative methods to census marine life, including identification of environmental DNA (eDNA) left behind by organisms in the water column. However, little is understood about how eDNA is distributed in the ocean, given that organisms are mobile and that physical and biological processes can transport eDNA after release from a host. Particularly in the vast mesopelagic ocean where many species vertically migrate hundreds of meters diurnally, it is important to link the location at which eDNA was shed by a host organism to the location at which eDNA was collected in a water sample. Here, we present a one-dimensional mechanistic model to simulate the eDNA vertical distribution after its release and to compare the impact of key biological and physical parameters on the eDNA vertical and temporal distribution. The modeled vertical eDNA profiles allow us to quantify spatial and temporal variability in eDNA concentration and to identify the most important parameters to consider when interpreting eDNA signals. We find that the vertical displacement by advection, dispersion, and settling has limited influence on the eDNA distribution, and the depth at which eDNA is found is generally within tens of meters of the depth at which the eDNA was originally shed from the organism. Thus, using information about representative vertical migration patterns, eDNA concentration variability can be used to answer ecological questions about migrating organisms such as what depths species can be found in the daytime and nighttime and what percentage of individuals within a species diurnally migrate. These findings are critical both to advance the understanding of the vertical distribution of eDNA in the water column and to link eDNA detection to organism presence in the mesopelagic ocean as well as other aquatic environments.

Improved biodiversity detection using a large-volume environmental DNA sampler with in situ filtration and implications for marine eDNA sampling strategies

“…Furthermore, despite a myriad of processes that could potentially blur eDNA signatures in oceanic environments -such as particle sinking, ocean currents, vertical mixing, and biologically-mediated transport such as diel vertical migration, our results and other recent studies indicate that eDNA signatures may remain localized. Our finding that eDNA detected diversity changes on the order of 10s of meters in depth are consistent with modeling results that show midwater eDNA signatures remain within 20 meters of their origin in the vertical direction (Allan et al, 2021), and add to a growing body of field evidence from pelagic systems demonstrating that eDNA can detect biodiversity changes with depth (Canals et al, 2021;Easson et al, 2020;Govindarajan et al, 2021).…”

Environmental DNA persistence and fish detection in captive sponges

“…As for the resident species, sponge nsDNA may pro- When there is no bar at the corresponding time point, it represents that no fish species were detected. Colour codes refer to the experimental fish species for each tank (three species for each tank, two of which ubiquitous) detection (Allan et al, 2021;Canals et al, 2021). Thus, the sessile nature of sponges could more exhaustively track the diel fluctuations and other behaviours of fishes.…”

Environmental DNA persistence and fish detection in captive sponges

“…Our evidence further demonstrates how certain sponges could help monitor these more elusive species (preserving eDNA for longer), which may be missed by other monitoring methods. As for the resident species, sponge nsDNA may provide insightful fish detection compared to aquatic eDNA because spatial and temporal variability of aquatic eDNA may affect species detection (Allan et al, 2021; Canals et al, 2021). Thus, the sessile nature of sponges could more exhaustively track fish’s diel fluctuations and other behaviours.…”