After 100 years: Seahorses back in the German Wadden Sea

About 100 years ago, the short-beaked seahorse (“Hippocampus hippocampus”) disappeared from the German Wadden Sea. In the 1930s, a fungal infection wiped out almost all the seagrass meadows, meaning the adorable aquatic creatures’ habitat was destroyed almost overnight.

But now the seahorses seem to be back in the North Sea: in the past two years alone, seventy beach finds of washed-up seahorses were registered in the database of the “Beach Explorer” portal. For comparison: from 1949 to 2019 there were only 12 reports.

The discoveries of the rare animals still puzzle researchers. It is not yet clear where the animals come from and whether there may be permanent populations in the German North Sea. “The finds show that seahorses are becoming increasingly common in the flushing areas of the Wadden Sea,” says Hans-Ulrich Rösner, head of the WWF Wadden Sea office. “Even though the animals are still rare, it is still a cause for joy.

However, it is still unclear whether there is already a permanent population in the North Sea: “We do not yet know whether the seahorses have already settled in our Wadden Sea or whether they are being driven away by storms from other coasts,” Rösner explains.

The researchers therefore hope for further discoveries of seahorses, so that they can improve vague data and make comprehensive statements about the occurrence of the aquatic animals. The seahorses’ habitat actually consists of meadows with seaweed, algae or seagrass that are constantly flooded with water. Such habitats are currently not known in the German Wadden Sea, but are located off the Dutch coast and in the English Channel.

One theory from the researchers is therefore that the animals drifted from there and washed up on the German coast. This is also supported by the fact that only young male animals have been found so far, Wiggering said. If there were a permanent population, older or female animals would also have to be discovered over time.

Another theory is that in addition to seagrass meadows, other new habitats for the animals are also created. For example, bladderwrack is found on the foundations of offshore wind turbines and seahorses can also live there. The researchers also want to observe the extent to which warming of the North Sea can influence the occurrence. “We hypothesize that climate change could have a positive effect on the occurrence of seahorses,” explains Benedikt Wiggering, a biodiversity expert at the Lower Saxony Wadden Sea National Park Management in Wilhelmshaven. (pre)