Zeewieren

Zeewieren, or seaweed, is the collective term for macroscopic, photosynthetic marine algae that grow in coastal waters around the world. They are not true plants, but they perform photosynthesis using seawater and nutrients. Zeewieren comprise several distinct groups, typically categorized as brown, red, and green algae, and they attach to substrates with specialized structures called holdfasts.

Most zeewieren inhabit the intertidal or subtidal zones, from rocky shores to deeper beds. Brown algae include larger kelp species such as Laminaria and Macrocystis, which form long fronds and can create structured underwater forests. Red algae (for example Porphyra and Gracilaria) are common in shallower, often warmer waters, and green algae (such as Ulva) are widespread and tend to be simpler in form. Growth depends on light, nutrients, and stable conditions, with some species capable of rapid expansion in nutrient-rich environments.

Zeewieren are used as food in many cultures, especially in East Asia and increasingly in Europe. They are valued for minerals (notably iodine and calcium), dietary fiber, and vitamins, and they contain various bioactive compounds. In industry, certain seaweeds provide hydrocolloids: alginates from brown algae, and agar and carrageenan from red algae, which act as thickening and gelling agents in foods, cosmetics, and pharmaceuticals.

Cultivation and sustainability efforts focus on farming methods such as longlines, racks, or shallow beds, allowing controlled harvests and regrowth. Seaweed farming can help remove excess nutrients from coastal waters and provide habitat for marine life, contributing to coastal resilience. Careful management is needed to prevent overharvesting, manage potential invasive introductions, and monitor iodine levels in food products.