Biodiversity in Belgian coastal waters has changed fundamentally over the past few decades due to global warming. Typical cold-water species, such as brown shrimp, gobies, and herring/sprat, are now far less abundant, whereas warm-water species (like the venomous lesser weever) and comb jellies are thriving.
This is shown by research conducted by biologist Ward Stellamans (KU Leuven) in collaboration with the Flanders Marine Institute (Vlaams Instituut voor de Zee, VLIZ).
Stinging weever fish
In the past, you could find plenty of brown shrimp in the shallow coastal waters; today, they are teeming with small weever fish, exotic species, and jellyfish. Anyone wading in the shallows along our coast today would do well to be careful, as the venomous lesser weever fish is found in the coastal waters far more often than it was 30 years ago. According to Stellamans, beach fauna has changed drastically.
In other words, Belgium’s shallow surf zone, the so-called “sea’s nursery” between the waterline and roughly hip-deep water, is changing faster and more visibly than the open sea.
“Several species use this zone to grow,” Jan Seys of the VLIZ explains to HLN and VTM. “Yet, it is precisely there that the ecosystem is under pressure from tourism, coastal development, and climate change.”
Comparison
For eleven years, the research team collected data along the coast. Four times a year, volunteers dragged seine nets through the shallow water to see what life they would find.
Their findings were compared with historical data from 1996 and 1997 collected by researcher Bregje Beyst (Ghent University). The results were spectacular, says Jan Seys of the VLIZ.
Impoverished sea
Cold-water species, in particular, are taking a heavy hit. For instance, the grey shrimp population has declined by at least 78 percent. Sea bass and plaice remain stable for the time being, while other species are showing a marked increase.
The lesser weever is actually 24 times more common today than it was in the late 1990s. In addition, two new species also appeared: the American comb jelly and the Atlantic grey swimming crab.
The conclusion is that the sea has become impoverished and warmer, and that it contains far more comb jellies than in the past. These are not dangerous to humans, but they consume vast amounts of plankton, which can lead to a less productive sea.
Warmer seawater
The temperature of the beach water is also a cause for concern. A temperature of 23.4 degrees was recently recorded, which is extremely warm. “Species disappearing from here may be moving to deeper, cooler waters.”
An earlier LifeWatch/VLIZ summary already noted that the North Sea has warmed by about +1.7°C over half a century, roughly twice the global average for oceans and seas.
The European Environment Agency (EEA) puts the Belgian finding in a wider European pattern: in the Greater North Sea and Celtic Seas, warm-favoring fish species have increased to 64% of the species mix, overtaking cold-favoring species since the late 1980s, with a positive correlation to sea-surface temperature.
Sea’s calendar
Scientists have also observed that the sea’s calendar has shifted: some species appear earlier or later than they used to, affecting the delicate balance of the ecosystem. According to the researchers, further monitoring is crucial.
Climate change seems to be an important driver of seawater warming and changes in fauna, but it is not the only factor. Other aspects, such as fishing pressure, predator changes, bycatch, beach nourishment, dredging, port infrastructure, nutrients, plankton shifts, tourism pressure, and invasive species, also matter.
