Primnoa resedaeformis (Gunnerus, 1763)
Primnoa resedaeformis is a deep-sea gorgonian octocoral (a "seafan") reported from North Atlantic, Arctic, and North Pacific waters at depths of 65 to 3200 meters. However, according to Cairns and Bayer (2005), specimens from outside the eastern and western Atlantic apparently do not actually belong to this species. According to their review of the genus Primnoa (which includes technical descriptions and a key to the species), P. resedaeformis is known from the North Atlantic from Virginia Beach to Greenland (91– 548 meters) and from the Eastern Atlantic from Greenland to Scotland (95–1,020 meters). Primnoa resedaeformis has been known for hundreds of years, having been poorly described but remarkably well illustrated as early as 1605 by Clusius (the pioneering Flemish naturalist--in particular, botanist--and horticulturist), and described under at least four different names. This bright pink (in life) coral is one of the most often reported deep-water octocorals, probably because it is found in relatively shallow-water fishing beds and occurs off northern Europe, an active region for early taxonomic descriptions of all kinds. (Cairns and Bayer 2005)
In a study in the Northeast Channel off Nova Scotia, Watanabe et al. (2009) found that P. resedaeformis abundance was greater at sites between 500 and 1000 meters than at shallower depths, peaking between 500 and 650 meters, then declining with greater depth. Abundance was moderately correlated with cover of hard substratum (cobble, boulder, bedrock). Maximum colony height was 125 cm, with much smaller colony heights recorded for depths less than 500 meters.
Primnoa resedaeformis has an arborescent skeleton composed of calcite and gorgonin. Toward the inside of the axial skeleton, gorgonin (a tough, horny protein derived from surface particulate organic matter [POM]) and calcite are deposited in concentric, annually formed growth rings, similar to tree rings. Comparison with ages assesed by radioisotype analysis found that precision of ring counts had an error of less than ± 2 years. (Sherwood et al. 2005a,b) The lifespan of these corals may exceed several hundred years, although in a study by Mortensen and Buhl-Mortensen (2005), the maximum estimated age (based on analysis of annual growth rings) was 61 years. (Risk et al. 2002; Sherwood et al. 2005a and references therein)
Heikoop et al. (2002) investigated the use of P. resedaeformis corals as a source of climate records. They found that the influence of nutrient isotopic composition and climate and productivity variations on the isotopic composition of surface POM may be recorded in gorgonin layers. Given the long lifespans of these corals, the potential exists to obtain extended records of surface productivity, deep ocean temperature, and chemistry that would be of great value to climatologists and fisheries managers. Sherwood et al. (2005a,b) also concluded that useful environmental data are recorded in the organic endoskeletons of deep-sea octocorals. Isotopic signatures from the time of formation are preserved over a time scale of millenia, making these corals excellent candidates for retrospective studies of the surface marine environment. Sherwood et al. suggest that P. resedaeformis could serve as a long-term, high resolution monitor of ocean surface conditions, particularly in temperate and boreal environments where proxy data are lacking.
Conservation and Management
Andrews et al. (2002) collected P. resedaeformis from waters off southeast Alaska with ages estimated over 100 years for sections near the heavily calcified base. Based on validated growth ring counts, growth of these corals ranged from 1.60 to 2.32 cm per year in height and was approximately 0.36 mm per year in diameter. These slow growth rates suggest that the fishery habitat created by these corals is extremely vulnerable to bottom fishing activities and may take over 100 years to recover.
In contrast to the more familiar shallow water reef-forming corals, which obtain energy via photosynthetic symbiotic algae (zooxanthellae), deep-sea corals such as Primnoa resedaeformis live far too deep to receive the light necessary to sustain photosynthesis. Instead, these corals are suspension feeders, sustaining themselves on particles filtered from the water.
Primnoa resedaeformis is believed to have a nonfeeding larval mode (Mercier and Hamel 2011).
Mercier and Hamel (2011) studied reproduction in Primnoa resedaeformis (along with two other deep-sea octocorals, Anthomastus grandiflorus and Keratoisis ornata) off eastern Canada. Primnoa resedaeformis is a broadcast spawner with external fertilization. In contrast to the two other octocorals studied, which showed a clear annual breeding pattern, for P. resedaeformis the authors observed mixed size classes of oocytes (immature eggs) in samples from all months, depths, and locations studied, suggesting continuous oogenesis (oocyte production) or overlapping development of oocyte cohorts. Thus, the gametogenic cycle appears to span more than a year. No evidence of periodicity was found in this species, although it could have been masked by the striking bathymetric (depth) variation in potential relative fecundity (i.e., oocytes per polyp). Unfortunately, no spermatocysts (sperm-producing cells) were observed.
Buhl-Mortensen and Mortensen (2004) surveyed the crustacean fauna associated with P. resedaeformis from samples taken in the Northeast Channel off Nova Scotia. They recorded seven apparently coral-associated species: Enalcyonium cf. olssoni (Copepoda); Ornatoscalpellum stroemii (Cirripedia); Munna boecki (Isopoda); Metopa bruzelii, Proboloides calcarata, and Stenopleustes malmgreni (Amphipoda); and Pandalus propinquus (Decapoda). In addition, they recorded an unidentified cypris larva (Cirripedia) and two species known to be pelagic and not regarded as coral-associated fauna, Sergestes arcticus (Decapoda) and Themisto compressa (Amphipoda).
Krieger and Wing (2002) note that few in situ observations have been made of deepwater corals and, as a consequence, little is known of their ecology. They observed Primnoa from a manned submersible at 11 sites in the Gulf of Alaska from 1989 to 1997 at depths of 161 to 365 meters. They identified 10 megafaunal groups that associate with Primnoa to feed on the coral, use the coral branches for suspension feeding, or for protection. Predators on Primnoa polyps included sea stars, nudibranchs, and snails. Sea stars were the main predators, consuming 45% and 34% of the polyps at two sites. Suspension-feeders included crinoids, basket stars, anemones, and sponges. Most suspension-feeders observed at depths >300 meters were associated with Primnoa. Protection-seekers included rockfishes, crabs, and shrimps. Individuals of six rockfish species were either beneath, among, or above Primnoa. Shrimp were among the coral polyps, and a pair of mating king crabs were observed beneath a Primnoa colony.
- Primnoa reseda (Pallas, 1766) (synonym)