The Answer to Animal, Plant, Mineral, or Man-Made: #2

The pneumatocyst of brown kelp with a large colony of lacy mat bryozoan growing across it. Image courtesy Emma Bueren

It’s a type of kelp (Phaeophyceae) with the tell-tale crystalline growths of a marine bryozoan!

The degraded remains of kelp blades. Image courtesy Emma Bueren

Kelp is a large type of brown algae, or seaweed, which is found in relatively shallow, nutrient-rich parts of the ocean. Specifically, the mystery picture shows a part of the brown kelp’s pneumatocyst, or gas-filled balloon-like structure, and the remains of the its leaf-like blades. The buoyant pneumatocyst allows the blades to remain within reach of the sunlight, enabling photosynthesis.

The strange crystalline structure is actually the growth of a small aquatic invertebrate animal, a type of bryozoan. There are many diverse types of bryozoa found all over the world, but almost all are colonial animals. This means that an individual bryozoan is unable to live independently and to survive, most group together in large colonies. The bryozoa found on this specific kelp is likely the lacy crust bryozoan.

Although pretty, the lacy crust bryozoan is actually an invasive species which harms local kelp forests. The colonies grow quickly and damage the kelp blades, leading to a reduction of kelp forests which are important habitats for many types of fish and other sea creatures.

Congratulations to Todd Ruston, for being the first to identify both the kelp and the bryozoan!

Runners up: Victoria Assad.

The beautiful, but invasive, colonies of lacy crust bryozoan. Image courtesy Emma Bueren