Rusty rock • Hildenbrandia rubra
Identification
This red alga adheres so closely to the rocks on which it grows that it often looks like a rusty stain on rock and could be easily overlooked. It is a thin (0.3 mm thick), rose to brownish-red, uncalcified, and sometimes translucent crust. See the AlgaeBase species page for more photos.
Habitat
This species is found year-round throughout the intertidal of protected to exposed habitats, including the shallow subtidal and upper, emergent intertidal rocks. It is especially common in protected rock crevices and tidepools, though it will also grow on exposed rock surfaces. Its range stretches along both east and west coasts of the North Pacific, and is found as far south as China and Panama. It is also found on coastlines of the Arctic Ocean, Chukchi Sea, the Galapagos Islands, the North Atlantic, the North Sea, and the Baltic Sea.
Similar Species
This is one of the two most common crusts in the Pacific Northwest. The easiest way to distinguish rusty rock from the crustose form of Turkish washcloth (Mastocarpus papillatus) - the other common crust - is by thickness and opacity: rusty rock is thin and semi-transparent while Turkish washcloth is thick and opaque (see comparison in left photo). Hildenbrandia occidentalis is also found in the Pacific Northwest but appears to be less common. It is thicker and reddish-black.
Intriguing Info
Rusty rock grows very slowly - sometimes only 1.2 mm per year. It also appears to only rarely produce young individuals. See the E-Flora species page for further information on growth and ecology.
iNaturalist
https://www.inaturalist.org/taxa/183033-Hildenbrandia-rubra
This red alga adheres so closely to the rocks on which it grows that it often looks like a rusty stain on rock and could be easily overlooked. It is a thin (0.3 mm thick), rose to brownish-red, uncalcified, and sometimes translucent crust. See the AlgaeBase species page for more photos.
Habitat
This species is found year-round throughout the intertidal of protected to exposed habitats, including the shallow subtidal and upper, emergent intertidal rocks. It is especially common in protected rock crevices and tidepools, though it will also grow on exposed rock surfaces. Its range stretches along both east and west coasts of the North Pacific, and is found as far south as China and Panama. It is also found on coastlines of the Arctic Ocean, Chukchi Sea, the Galapagos Islands, the North Atlantic, the North Sea, and the Baltic Sea.
Similar Species
This is one of the two most common crusts in the Pacific Northwest. The easiest way to distinguish rusty rock from the crustose form of Turkish washcloth (Mastocarpus papillatus) - the other common crust - is by thickness and opacity: rusty rock is thin and semi-transparent while Turkish washcloth is thick and opaque (see comparison in left photo). Hildenbrandia occidentalis is also found in the Pacific Northwest but appears to be less common. It is thicker and reddish-black.
Intriguing Info
Rusty rock grows very slowly - sometimes only 1.2 mm per year. It also appears to only rarely produce young individuals. See the E-Flora species page for further information on growth and ecology.
iNaturalist
https://www.inaturalist.org/taxa/183033-Hildenbrandia-rubra
References
Lindberg, M. and Lindstrom, S. (2010). Hildenbrandia rubra. Seaweeds of Alaska. Accessed 17/11/2014.
O'Clair, R. and Lindsrom, S. Hildenbrandia rubra (Sommerfelt) Meneghini 1841. In Klinkenberg, Brian. (Ed.). E-Flora BC: Electronic Atlas of the Plants of British Columbia. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. Accessed 17/11/2014.
Authors and editors of page
Joel White, Kelly Fretwell, and Brian Starzomski (2014).
Lindberg, M. and Lindstrom, S. (2010). Hildenbrandia rubra. Seaweeds of Alaska. Accessed 17/11/2014.
O'Clair, R. and Lindsrom, S. Hildenbrandia rubra (Sommerfelt) Meneghini 1841. In Klinkenberg, Brian. (Ed.). E-Flora BC: Electronic Atlas of the Plants of British Columbia. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. Accessed 17/11/2014.
Authors and editors of page
Joel White, Kelly Fretwell, and Brian Starzomski (2014).