eDNA Water Sampling Simulator (2D)

Deposit & Sample

Time since organism present 0.0 h

Playback speed 4×

Assay parameters

eDNA decay rate 0.12 /h

Plume spread rate 1.1 m/√h

Detection threshold 2,000 copies/L

Sample volume 1.0 L

Live readout

Distance to source

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DNA at sample point

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Detection threshold

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Detection probability

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Sample verdict

place an organism first

Sample log

How it works

Every organism sheds trace DNA (skin, mucus, waste) into the water. That environmental DNA (eDNA) doesn't stay put: its concentration decays over time as microbes and UV break it down, and it dilutes as it spreads outward from where it was shed. A water sample only tests positive if the DNA concentration at that exact place and time is still above the assay's detection threshold.

C(r,t) = C0 · e^(−k·t) · e^(−r²/2σ(t)²),  σ(t) = σ0 + s·√t

Decay rate (k) — how fast DNA breaks down chemically/biologically; higher k means the signal disappears sooner after the organism leaves.
Spread rate (s) — how fast the plume mixes through the water body; faster spreading dilutes concentration at any fixed point sooner.
Detection threshold — the minimum concentration the PCR assay can reliably pick up; a more sensitive assay has a lower threshold.
Sample volume — a bigger water sample captures proportionally more DNA template, effectively lowering the concentration needed to detect.

The key idea: a NEGATIVE result never proves the species was absent — it only proves the concentration at that sample's place and time was below threshold. The species can be truly present and still go undetected.

Click the water to place an organism — it swims through, sheds eDNA, then leaves. Switch to "Move sample" and click anywhere to test the water.

Organism (transient) eDNA plume Sample probe Positive detection Negative / false negative