Ecomare

Many small sand grains, clay particles and flakes of animal wastes drift in the turbulent North Sea. The clay particles and nutrient-rich waste stick together when in contact. This all sinks to the bottom in the areas in the Wadden Sea where the seawater is at rest. In that way, a sandbank is created which is exposed during low tide. These banks, and certainly those banks that are built up of a high percentage of clay, are very rich in nutrients. They form a table of food for benthic animals and sea fish during high tide and for wading birds during low tide.

The channels are those parts of the Wadden Sea that do not dry up during low tide. The ebb and flood currents move through the channels to and from the tidal inlets. The channels are the navigational routes for ships in the wadden region. This is also where benthic animals, marine mammals and sea fish live. The wad fishermen catch shrimp and flatfish here. Mussels are farmed on the edges of sandbanks that remain underwater.

Tidal creeks or gullies are small channels between the sand(wad)banks that are totally dry during low tide. When the water starts to ebb, it flows from the banks via the creeks to the channels. When the bank is exposed, the animals on the banks that have fed on the food follow the creeks to deeper water. During ebb, shrimp have a lot to catch in these creeks.

The bottom of the tidal area is densely populated with all kinds of benthic animals. They feed mostly on phytoplankton or zooplankton, which they filter out of the seawater, and on one-celled algae and animals dwelling on the tidal floor. That small fry is very numerous since it can profit from a continual supply of nutrients via the rivers and from the North Sea. Newly suspended mud and nutrient materials arrive with every high tide, and most of it settles on the flats.

On the tidal flats during low tide, it appears as if the banks are bare of plants. However, it is full of billions of one-celled diatoms. Sometimes (in the spring and summer), there are so many that the banks turn brownish in color. Diatoms are food for periwinkles, laver spire shells and lugworms. Even mussels, cockles, Baltic tellins and gapers can be found on the tidal banks. This abundance in food attracts millions of birds that feed on the shellfish. Black-tailed godwits, curlews, dunlins and various types of plovers are found in large numbers. Eelgrass is the only seed-plant able to grow on the flats.
During high tide, the underwater banks are inhabited by hermit crabs, shrimp and the larger shore crabs. Barnacles are found on hard substances such as poles, shells and stones along the dikes.

Many species of fish are found in the Wadden Sea. Some of them are there for just one stage in their life; others are there permanently. The fatherlasher and the eel-pout spend their whole life span in the Wadden Sea. Flounder, smelt, pipefish and the three-spined stickleback stay there for a season. Plaice, herring, sole and sprat find the Wadden region an ideal nursury.
Tidal banks grow into salt marshes when they are so elevated that they no longer flood daily. A salt marsh only floods during spring tide or storm.