Morphometry and growth of sea pen species from dense habitats in the Gulf of St. Lawrence, eastern Canada

Abstract

We examined four species of sea pen (Anthoptilum grandiflorum, Halipteris finmarchica, Pennatula aculeata and Pennatula grandis) collected from the Gulf of St. Lawrence and mouth of the Laurentian Channel, eastern Canada. An exponential length-weight relationship was found for all four species, where growth in weight was progressively greater than growth in length with increasing colony size. Halipteris finmarchica, P. grandis and P. aculeata presented the better allometric fits, explaining over 80% of the variance. In addition, a count of growth increments visible in transverse sections in 86 A. grandiflorum and 80 P. aculeata samples was made. Presumed ages ranged between 5 and 28 years for A. grandiflorum and 2 and 21 years for P. aculeata. Radiocarbon assays were inconclusive and could not be used to confirm these ages; further age validation is required. Radial growth of the rod is slow during the first years, increasing at intermediate sizes of the colony and slowing down again for large colonies. Similar results were obtained from the relationship between colony length and number of growth increments where a logistic model was the best fit to the data. On average Spearman's rank correlations showed 11% of shared variance between sea pen length or weight and environmental variables. Bottom temperature and salinity, depth and summer primary production were significantly correlated to sea pen size for most species. ARTICLE HISTORY

Size metrics, longevity, and growth rates in Umbellula encrinus (Cnidaria: Pennatulacea) from the eastern Canadian Arctic.

“…Our results indicate a longer delay in the 14 C intake by the skeleton of the studied colonies, when compared with 14 C values obtained from the proteinaceous portions of skeletons of other deep-water corals in the NW Atlantic (Sherwood et al 2008). Radiocarbon analyses from the axis of the sea pen P. aculeata from the Gulf of St. Lawrence (NW Atlantic) yielded very depleted 14 C values, which did not help to validate age in the specimens studied by Murillo et al (2018). In contrast, the 14 C curve for the U. encrinus samples in this study is quite comparable to that of the calcite in the gorgonians K. grayi and P. resedaeformis, in which growth rings were confirmed to be formed annually (Sherwood et al 2008).…”

“…Although larger colonies do have larger peduncles, percentage of peduncle tended to decrease with colony height. This negative relationship was already reported for other sea pens (Baillon et al 2016;Murillo et al 2018). From a growth perspective, it suggests that as a colony becomes larger over time, peduncle growth rates seem to be reduced.…”

“…In both studies, the trace element analysis was applied to detect patterns that could indicate cyclicity in the axis chemical composition. This could have value in elucidating ring formation periodicity, considering the challenges involved in validating frequency of ring formation in deep-water sea pens (Wilson et al 2002;Neves et al 2015;Murillo et al 2018). In U. encrinus, the number of trace element ratio peaks was comparable to the number of rings visually determined in most samples, as was also observed for Halipteris finmarchica (Sars, 1851) (Neves et al 2015(Neves et al , 2018.…”

“…Average number of rings and radial growth rates (i.e., 0.067 mm year −1 ) were comparable to those estimated for other sea pen species (Birkeland 1974;Wilson et al 2002;Neves et al 2015), although linear growth rates were more similar to Halipteris spp. (Wilson et al 2002;Neves et al 2015) than to the feathershaped Ptilosarcus gurneyi (Gray, 1860) (Birkeland 1974) and P. aculeata (Murillo et al 2018), which might be related to the whip-like morphology of the former, which like U. encrinus have elongated, thin, and potentially tall bodies (both >2 m in height). To our knowledge, the colony showing 75 rings represents the oldest sea pen recorded so far.…”

Towards Non-Invasive Methods to Assess Population Structure and Biomass in Vulnerable Sea Pen Fields

“…Despite the recognized ecological importance of pennatulaceans, little is known about their biology and ecology, and their vulnerability to human pressures has been assessed under a precautionary approach [21]. Destructive sampling is still needed to estimate the biomass of a sea pen field, as well as to collect information on colonies’ size, population structure, and dynamics, in order to assess the main features of the population and to establish its need for protection.…”