Coral Larvae Dispersal in Ocean Currents

Ocean Current Field

Mean current speed 20 km/day

Current direction 15°

Mesoscale eddy strength 150

Larval Behavior

Turbulent mixing (K) 1.2 km²/day

Dispersal Outcome

Larval age

0.0 d

Settled

0.0%

Lost (mortality / swept out)

0.0%

Pre-competent larva Competent, seeking substrate Settled on reef Dead / lost

How it works

Each larva is tracked as a Lagrangian particle obeying the advection–diffusion equation used in real biophysical connectivity models:

dX/dt = U(X,t) + sqrt(2K)·dW/dt

U = mean current + Σ vortex(x,z)
vortex: v = Γ(−Δz, Δx) / (r² + a²)

The mean current advects every larva at a constant speed and heading. Two mesoscale eddies (rotating vortex fields, strength Γ set by the eddy slider, core radius a) add curl to the flow — this is what lets larvae recirculate back toward the source reef instead of just drifting downstream. The sqrt(2K)·dW term is a random-walk step scaled by the turbulent diffusivity K, representing sub-grid turbulent mixing that real current data can't resolve.

Biology layered on top of the physics:

Pre-competency (age < 2 days): the larva cannot settle even if it drifts over a reef — most broadcast-spawning corals need a minimum development time before their larvae (planulae) can metamorphose.
Competency window (2–20 days): once competent, a larva within capture range of a reef patch settles stochastically at a fixed encounter rate — settlement is a probability per unit time in range, not a certainty.
Mortality: a constant background hazard (predation, starvation) removes a fraction of larvae per day, S(t) = e^(−μt); larvae still drifting after the maximum pelagic larval duration (PLD ≈ 20 days) die of energetic exhaustion.

Real-world relevance: this is the same class of model (Lagrangian particle tracking over a current field, with a PLD competency window) that reef-connectivity studies use to estimate which reefs seed which — critical for designing marine protected area networks so upstream "source" reefs are actually protected.

⚠ Couldn't load the 3D engineThree.js failed to load from the CDN. Check your connection and reload.