The underwater life of the harbour

City ecologist and port biologist Martin Melchers has come across several exotic passers-by in the 65 years that he has been strolling through the port of Amsterdam. The latest special finds were the American blue sea crab, Japanese brush crabs and the South American brackish water horn. They probably ended up in the Amsterdam harbour 'by accident' via ballast water.

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Commissioned by the port authority, Melchers investigates biodiversity in the port of Amsterdam. He goes along with professional fishermen to study the animals under and above water. What about biodiversity in the port? Do we have enough sea bass and glass eels in the water?

Amsterdam Wildlife

''The number of sea bass is increasing,'' says Melchers. "Normally they reproduce in the south of England, but we see that they are now doing so in the Western Harbours as well. The harbours are full of griffon fish and glass eels." The city ecologist is currently working on a sequel to the film Amsterdam Wildlife, in which he follows the journey of the elvers, among other things. The route through the Nieuwe Zeesluis lock to Halfweg, where there is a stream of fresh water. There, they grow up to become eels.

Impact new sea lock

The arrival of the new sea lock is also an interesting aspect of the research. Melchers cannot yet say with certainty whether the largest sea lock in the world will affect nature. He does know from experience that living and working do not always have a positive effect on biodiversity. "Where there are people, nature is subordinate. However, fallow land or close to the frayed edges of the city are good areas for nature. The fringes of the city are the richest for nature. A lot grows and blossoms here! You can also see this in the harbour."

Mini-evolution behind the station

The harbour is a special and fun area to investigate, Melchers believes. "Ships take various animal species from all over the world with them. With the arrival of exotic species, the underwater world is changing rapidly. Whereas Darwin wrote in his books that evolution takes thousands of years, we see the opposite happening in the IJ. For example, behind the central station, I discovered a mini-evolution of the American long-legged rib jellyfish. The DNA of this jellyfish is different from that of its congeners."