Sea Grapes

Overview

Caulerpa racemosa, commonly known as "Sea Grapes," is a widespread green macroalga found in tropical and subtropical marine environments globally. While it is a valued food source in parts of its native range, certain varieties have become aggressive invasive species in regions like the Mediterranean, where they can significantly alter local benthic communities.

Appearance

This species is characterized by a creeping, root-like stolon that anchors to the substrate, from which short, upright fronds emerge. These fronds feature distinctive, crowded branchlets with oval or spherical tips, giving the alga a bead-like, grape-like appearance. The organism is siphonous, meaning it consists of a single, large multinucleate cell rather than complex tissues.

Distribution & habitat

Native to the Indo-Pacific, it is found across a variety of shallow marine environments, including sandy, muddy, and rocky substrates. It thrives in protected areas with limited wave action and is often observed in intertidal pools and shallow subtidal zones. In non-native regions, it has demonstrated an ability to colonize diverse seabed types, including dead seagrass meadows.

Biology & behavior

Caulerpa racemosa is highly polymorphic, meaning its growth form can change depending on its environment, which often makes identification challenging. It is capable of both sexual reproduction and asexual propagation; even a small fragment of the alga can regenerate into an entirely new organism, a trait that contributes to its success as an invasive species.