🪸 In my hand, I’m holding a piece of bladderwrack (Fucus vesiculosus), a seaweed commonly found along the Wadden Sea coast. The small, round bladders are not fruits but flotation organs. They help the seaweed stand upright in the water so its flat fronds can catch as much sunlight as possible. This is essential for photosynthesis – the process of turning light energy into nutrients.

🌊🫧 The bladders are filled with a mixture of gases. This is mainly oxygen, which the seaweed produces during photosynthesis, and nitrogen, which diffuses in from the surrounding seawater. Carbon dioxide, which the seaweed needs to grow, is almost absent because it is used up immediately. Thanks to this high oxygen content, the bladders provide enough buoyancy to keep the seaweed floating, allowing it to capture as much light as possible even at high tide or in murky waters.

🧫🔬 From a biological point of view, Fucus vesiculosus is a brown alga. It belongs to a group called the Fucales within the family Fucaceae. Even though it looks like a plant and makes its own food through photosynthesis, it is classified in a broader group called Stramenopiles, which also includes diatoms (tiny plankton) and some organisms that don’t photosynthesise at all. How exactly brown algae fit into the tree of life is still being studied, and researchers continue to discuss their relationship to other algae and to the ancestors of land plants.

🤗 For a more nuanced discussion, please feel free to use the comments section, private messages or the anonymous contact form on my website.

🤔 What do you think I’m holding in my hand?

🔍 If you’re thinking of a seaweed, you’re already halfway there! But apart from its branching structure, there’s not much of the seaweed left to see. That’s because it has been colonized and completely covered by a colony of tiny animals! These are moss animals (bryozoans), more specifically Electra pilosa.

🏘🦠 Moss animals usually form colonies (zoaria) made up of many individual animals (zooids). Each zooid consists of a soft body and a protective shell.

🪸🤝🪸 Within colonies, there is a division of labor. Strongly reduced individuals form stalk segments, tendrils, or root-like filaments. Other zooids produce reproductive cells – still others become "nurse" zooids or develop into bird’s-head-shaped avicularia or vibracularia, which prevent other organisms from settling on the colony. In these specialized zooids, both the tentacle crown and usually the gut are reduced.

🏡🦠 In short: the seaweed is mainly just living space for Electra pilosa, not a partner. For the seaweed itself, it is usually more of a burden than a benefit.

⛴️🪸 Moss animals can cause damage or maintenance costs to ships, harbor structures, and water management facilities through heavy growth.

💉🧫 On the other hand, they produce chemical compounds that are the subject of medical research, including the potential anti-cancer agent bryostatin 1.

🤗 For a more nuanced discussion, please feel free to use the comments section, private messages or the anonymous contact form on my website.