Long-term growth rates of four Mediterranean cold-water coral species maintained in aquaria

Abstract

Growth rates of the cold-water corals (CWC) Madrepora oculata, Lophelia pertusa, Desmophyllum dianthus and Dendrophyllia cornigera were measured over 8 mo under controlled conditions (12°C in the dark, fed 5 times a week) by means of the buoyant weight technique. Additionally, linear growth rates were measured in M. oculata and L. pertusa for 2 and 1 yr, respectively. The weight measurements revealed growth rates, expressed as percent growth per day (mean ± SD), of 0.11 ± 0.04 for M. oculata, 0.02 ± 0.01 for L. pertusa, 0.06 ± 0.03 for D. dianthus and 0.04 ± 0.02 % d -1 for D. cornigera. Growth in M. oculata was significantly higher (p < 0.0001) than in the other 3 CWC species. For M. oculata and L. pertusa, also linear growth was recorded. These values (mean ± SD) were 0.014 ± 0.007 and 0.024 ± 0.018 mm d -1 for M. oculata and L. pertusa, respectively. This is the first study that compares the growth rates of 4 different CWC species under the same experimental conditions of water flow, temperature, salinity and food supply. These corals have different growth rates, both in terms of total weight increase and linear increase, and these growth rates can be related to interspecific physiological differences. Data on growth rates are essential to understand the population dynamics of CWC as well as the recovery capacity of these communities after disturbance.

Calcification rates and the effect of ocean acidification on Mediterranean cold-water corals

“…One exception was the size of L. pertusa used in the first open system incubation (table 2) of the present study, as these specimens were as small as the ones used by Orejas et al [20]. The calcification rate of these small fragments was 0.09% d 21 while a rate of 0.02% d 21 was found by Orejas et al [20]. This indicates that the long-term aquarium conditions were less favourable for calcification of L. pertusa of the same size class than were the short-term on-board incubations, while the calcification rates of M. oculata reported by the two studies are in good agreement.…”

“…Also, a 10 per cent bias is relatively small when compared with the large natural variability of CWC calcification, with a coefficient of variation of up to 100 per cent. [20], and 0.01 and 0.02-0.07% d 21 determined by the alkalinity anomaly technique (this study). Interestingly, there seems to be no systematic bias to either higher or lower calcification rates between the methods used, which provides some confidence that all three methods provide similar estimates.…”

“…Interestingly, there seems to be no systematic bias to either higher or lower calcification rates between the methods used, which provides some confidence that all three methods provide similar estimates. The method used by Orejas et al [20] was based on longterm aquarium maintenance (256 days), while the 45 Ca and A T approaches were based on short-term on-board incubations (1 day) with freshly collected colonies. Our results suggest that calcification of L. pertusa and M. oculata is similar.…”

“…So far, only two studies have reported rates of calcification in CWCs. Average calcification rates measured with the buoyant weighing technique ranged between 0.02 and 0.11% d 21 in four Mediterranean species [20]. Maier et al [21] reported average rates of 0.02-0.07% d 21 obtained through labelling of colonies of L. pertusa with the radiotracer 45 Ca.…”

A new approach for assessing cold-water coral growthin situusing fluorescent calcein staining

“…26, 187-196 (2013) various threats, their growth rates remains poorly defined, mainly due to the difficulties of accessing their habitat (Freiwald et al 2004). Growth measurements of L. pertusa and M. oculata were performed in aquaria and revealed mean linear extension rates of 9 to 17 mm y −1 and 3 to 18 mm y −1 , respectively (Mortensen 2001;Orejas et al 2008Orejas et al , 2011, but there are possible artifacts introduced by extrapolating aquarium observations to field growth rates. In situ growth has been inferred from observations of colonies growing on man-made structures such as telegraph cables, oil platforms, long-lines or fishing nets, providing mean linear extension estimations of 6 to 27 mm y −1 for L. pertusa (Bell and Smith 1999;Gass and Roberts 2006;Roberts et al 2009;Gass and Roberts 2011) although no similar work has yet been done in M. oculata.…”