Every reef fish the divers found off Taiwan sat within 165 feet of a turbine leg, and 86 species had packed into that ring of steel on an otherwise empty seabed

A diver drops through 80 feet of green water off the west coast of Taiwan, and the bottom comes up flat, pale and featureless. Sand runs away in every direction with nothing standing on it, which is exactly what the charts said to expect.

Then a shape resolves ahead, a steel leg rising straight out of the seabed, and the water around it is thick with fish. Sixty feet further out there is almost nothing at all, and that contrast is the entire story.

A seabed with nothing to hold on to

The Formosa Wind Farm sits off Miaoli County on Taiwan’s western coast, between 1.2 and 5.9 miles from shore, in water running from 49 to 180 feet deep. The site covers roughly 35 square miles of seafloor.

All of that is soft sediment, sand and mud worked over by the currents, and it is not dead ground whatever the phrase suggests. Worms, clams and burrowing shrimp live down inside it, while flatfish work across the top.

It is simply a different kind of community, one that lives in the sediment rather than on top of it, because there is almost nothing out there that is hard and vertical. A reef fish needs a wall to hold against, and a plain like this offers no wall at all.

Sixty nine legs of steel, driven into sand

Between 2016 and 2021 developers put 69 turbines into that seabed, arriving in two phases, Formosa 1 first and the larger Formosa 2 behind it.

Each machine stands on a steel foundation driven or pinned into the sediment, with rock dumped around the base so the current cannot scour sand out from under it. Engineers call that scour protection and think about it purely as a way of keeping the tower upright, but the rock apron is a small reef in its own right.

The steel above it runs from the seabed to the surface and never moves, which makes each turbine the only vertical structure for miles in any direction. On a plain this flat, that turns a foundation into the only landmark a fish has.

What moved in, and in what order

Colonization follows a sequence predictable enough that biologists can write it down in advance. Barnacles, mussels, hydroids and algae take the bare steel first, and that crust turns a smooth surface into food and cover.

Small crustaceans and juvenile fish move into the crust, predators follow the small fish, and the whole community fills in from the bottom upward without anyone stocking the site or managing it in any way.

A team of Taiwanese fish biologists dove the wind farm in 2017, again in 2018 and once more in 2025, logging 11,552 individual fish across 97 species between them. Pole and line surveys in 2024 and 2025 added another 40, which took the running total to 137 species.

The ring that stops at 165 feet

Here is the figure that describes the shape of the whole effect.

Of everything recorded, 86 species were reef associated fishes, the groupers, snappers and damselfishes that need hard structure for shelter, for spawning or for the prey living on it. Every one of them was found within 165 feet of a foundation, according to the study, and not one turned up in the open sand between the machines.

That is an unusually sharp edge for an ecological effect, and it means the steel never enriched the wind farm as a whole. What it did instead was create 69 small islands on a plain that had none, and the full text shows how tightly bounded every one of them is. Past that edge, the seabed stayed the way it was.

How fast the steel caught up

Taiwan has been sinking purpose built artificial reefs for decades, and the ones nearest this site went down about fifteen years before the turbines did, which handed the researchers a comparison they could actually use.

By 2025 the foundations showed species richness, diversity and trophic structure statistically indistinguishable from those mature reefs. A structure built to make electricity had matched one built specifically to grow fish, having started fifteen years behind it.

Two cautions belong on that, and neither one undoes it. The gain is local and small against 35 square miles of sand, so it is not habitat policy, and the foundations are due to come out at the end of the license, which raises the question of what happens to the reef when the steel goes.

That argument trails a solar site or an offshore project the same way, and operators elsewhere have already begun asking whether the bases should simply be left where they stand. For now the fish are there, and they are staying very close.