Ocean VL 8 Flashcards
What defines an estuary?
Estuaries are tidal river mouths influenced by both the sea and freshwater input, characterized by strong salinity gradients, high suspended matter, and dynamic environmental conditions (tide).
What are the key characteristics of the Wadden Sea?
The Wadden Sea is a tidal flat area between low tide and spring tide along the southern North Sea. It is highly dynamic, sensitive to sea level changes, and supports rich biodiversity, particularly for migratory birds.
How did the Wadden Sea form?
The Wadden Sea emerged due to post-glacial sea-level rise, which slowed around 7,500 years ago, allowing sediment deposition from the North Sea to form tidal flats and salt marshes.
How have human activities impacted the Wadden Sea?
Human activities like diking, land reclamation, peat mining, and overfishing have significantly altered the Wadden Sea, reducing salt marshes, increasing sedimentation, and affecting species composition.
What is the zonation pattern in the Wadden Sea?
The Wadden Sea shows strong vertical zonation due to variations in flooding duration, sediment composition, and wave action, with distinct zones for species like seagrasses, algae, and benthic invertebrates.
Why is the Wadden Sea ecologically important?
The Wadden Sea is crucial as a nursery for North Sea fish, a resting place for migratory birds, and a site of high benthic-pelagic coupling, with high productivity and organic matter turnover.
How does climate change affect sediment dynamics in the Wadden Sea?
Rising sea levels and stronger storms increase sediment movement, leading to erosion of tidal flats and salt marshes. These changes threaten coastal protection and habitat stability.
What types of fauna dominate the tidal flats in the Wadden Sea?
The tidal flats are dominated by endofauna such as worms, bivalves, and snails.
Species like Arenicola (lugworm) play key roles in bioturbation, supporting a food web critical for migratory birds.
What role do salt marshes play in the Wadden Sea ecosystem?
Salt marshes provide habitat for diverse species, including breeding birds.
They also act as carbon sinks and protect coastal areas by reducing wave energy. However, diking and land use have reduced their extent.
What are the effects of eutrophication in the Wadden Sea?
utrophication from nutrient inputs has led to algal blooms (blanket of death), oxygen depletion (anoxia), and seagrass decline.
While some recovery has occurred since the 1980s, further nutrient reductions are needed for full ecosystem recovery.
Why is the Wadden Sea important for migratory birds?
The Wadden Sea serves as a critical feeding and resting site for millions of migratory birds. Species such as Dunlin and Curlew rely on the rich benthic fauna for food during long-distance migrations.
How does the Wadden Sea contribute to carbon sequestration?
The Wadden Sea’s salt marshes and seagrass beds store significant amounts of carbon. Seagrass meadows, in particular, act as long-term carbon sinks, storing organic matter in low-oxygen sediments.
What are the potential ecological impacts of offshore wind farms in the Wadden Sea?
Wind farms can affect hydrodynamics, sediment transport, and nutrient cycling.
They provide hard substrates for benthic organisms, but are also steppng stones for invasive species and also disrupt local ecosystems through changes in water mixing and habitat structure.
But they may provide refuge for fishes.
How has human settlement influenced coastal defense in the Wadden Sea region?
Settlements on artificial hills (Wurten) and later dike construction have altered natural sediment deposition and increased the risk of flooding. Modern dikes protect against storm surges but limit the natural expansion of salt marshes.
What measures have been taken to restore the Wadden Sea ecosystem?
Efforts include reducing nutrient inputs, protecting salt marshes, and limiting mechanical cockle fishing. Some seagrass recovery has been observed in the northern Wadden Sea, but further action is needed in the southern regions.
