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| The sea raspberry |
The sea raspberry, Gersemia (Eunephthya) rubiformis (Ehrenberg, 1834), is one of a number of anthozoans (sea anenomes, corals, sea pens and sea whips; phylum Cnidaria) found in Alaska waters. These animals are predators, feeding on small plankton that they may capture while suspension feeding. Unlike the stony and reef-building corals so many people are familiar with, soft corals do not build a hard, calcium carbonate skeleton. Soft coral have a soft, leathery surface and build irregular, often branched colonies. Sea raspberries are generally small colonies and their color ranges from light pink to red. Sea raspberries in Alaska are actually two known species: Gersemia rubiformis and Gersemia fruticosa.
The sea raspberry has long been known to inhabit US Arctic waters and is found throughout the Bering and Chukchi Seas and has been noted in publications as recent as 2009 (MacGinitie, 1955; Sparks and Pereyra, 1966; Feder et al., 2005; Bluhm et al., 2009; RACE database: http://www.afsc.noaa.gov/RACE/groundfish/survey_data). The sea raspberry is a circumboreal species found throughout cold waters of the northern hemisphere and noted along the northeastern Pacific coastline from California to the Chukchi Sea. We find it to be broadly distributed in the Chukchi but generally, colonies occur in low densities overall offshore.
Epifaunal organisms (animals living on the sediment surface) have a range of life habits from sessile suspension-feeding animals such as sea squirts (ascidiaceans) to highly mobile predators such as crabs. Epifaunal communities include a number of animals that build colonies extending into the water column and thus, creating microhabitat. These include sponges, sea squirts, bryozoans, and many others. Colonial epifauna may require hard substrates for settlement and growth but some can establish themselves in soft sediments.
In the northeastern Chukchi Sea, hard substrates are less common offshore so the colonial organisms requiring such habitat are less common. As a colonial epifaunal species , the sea raspberry attaches to hard surfaces such as rocks and the shells of large animals. Thus, although regularly captured during sampling and ubiquitous across the Bering and Chukchi seas, the sea raspberry is habitat limited offshore. Corals are usually associated with rich ecosystems with many animals dependent on the corals for food and protection. Being small colonies in the Chukchi (usually on the order of 10 to 20 cm), these organisms wouldn't provide the microhabitat for other species often provided by large corals and dense epifaunal assemblages.
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| Epifauna on snail shell |
Talk about recycling, the snail shell to the left is occupied by a hermit crab and has a chiton, some barnacles, a sea raspberry, and other colonial epifauna attached.
See also the webpage at http://www.afsc.noaa.gov/groundfish/HAPC/SeaRaspberry_synopsis.htm for more information.
References:
Barnes, R.D. 1987. Invertebrate Zoology, Fifth ed. Suanders College Publishing, Philadelphia.
Bluhm, B.A., Iken, K., Mincks Hardy, S., Sirenko, B. I., and Holladay,
B. A., 2009. Community structure of the epibenthic megafauna in the Chukchi
Sea. Aquatic Biology 7, 269-293.
Feder, H.M., Jewett, S.C., Blanchard, A. 2005. Southeastern Chukchi Sea (Alaska) epibenthos. Polar Biology, 28:402-421.
Kesseler, D. W., 1985. Alaska's Saltwater Fishes and Other Sea Life. Alaska Northwest Publishing Co., Anchorage, AK.
MacGinitie, G.E. 1955. Distribution and ecology of the invertebrates of Point Barrow, Alaska. Smithsonian Misc Collection 128:1-201.
Sparks, A.W., Pereyra, W. T. 1966. Benthic Invetebrates of the Southeastern Chukchi Sea. In Wilimovsky, N. J., Wilfe, J. N (eds). Environment of Cape Thompson Region, Alaska. United States Atomic Energy Commission.
Ushakov, P. V., 1955. Atlas of the Invertebrates of the Far Eastern Seas of the USSR. Israel Program from Scientific Translations, 1966
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