Relationships between growth, population dynamics, and environmental parameters in the solitary non-zooxanthellate scleractinian coral Caryophyllia inornata along a latitudinal gradient in the Mediterranean Sea

Abstract

The ecology of scleractinian corals may be understood through comparisons between population demographic data and environmental parameters. Growth (growth constant and maximum size) and demographic parameters (population structure stability, instantaneous mortality rate, average age of individuals, percentage of immature individuals, age at maximum biomass, and average age of biomass) of the solitary, non-zooxanthellate, and temperate coral Caryophyllia inornata were investigated at six sites along an 8°latitudinal gradient of temperature and solar radiation (SR) on the western Italian coasts. Growth parameters were homogeneous among populations across the investigated latitudinal range. While demographic parameters were not correlated with depth temperature, populations were progressively less stable and showed a deficiency of young individuals with increasing SR, likely as a result of the lowered energetic resources due to reduced zooplankton availability. These results contrast with data from another Mediterranean non-zooxanthellate solitary coral, Leptopsammia pruvoti, investigated along the same gradient, which shows no correlation between population demography and temperature or SR.

Inferred calcification rate of a temperate azooxanthellate caryophylliid coral along a wide latitudinal gradient

“…The negative correlation between SR and linear extension rate for immature individuals, confirmed both by the linear and the power function model based on bootstrapped coefficients, may be due to the increasing mean age of immature individuals in the southernmost populations, i.e., the populations with the lowest SR. In fact, the linear extension rate of this species decreases with increasing age (Caroselli et al 2016), and the mean immature age is higher at lower latitudes (Pearson's correlation test, p \ 0.05). Consequently, this result is likely to be biased by the slightly higher age of immature individuals in populations characterized by higher SR.…”

“…In this study, the environmental parameters (DT and SR) for each site were obtained by averaging monthly values that covered the mean turnover time of the populations, found to be 6 yr (Caroselli et al 2016). Thus, 72 monthly values were considered for each site, starting from the sampling month backward.…”

“…The bulk skeletal density (Bucher et al 1998) of each individual was obtained by dividing M by V. The age of each sample was estimated using the von Bertalanffy length-age growth function, previously obtained and based on growth band analysis by means of computerized tomography (von Bertalanffy 1938;Sparre et al 1989;Caroselli et al 2012Caroselli et al , 2016. Using the von Bertalanffy length-age growth function to estimate the age of the polyp, the annual linear extension rate was obtained for each sample (von Bertalanffy 1938;Caroselli et al 2012).…”

“…At each site, samples were collected using transects that consisted of 4-8 square patches of 0.1 m 2 each, 3 m apart (site and number of patches: Genova: n = 4; Calafuria: n = 8; Elba: n = 4; Palinuro: n = 6; Scilla: n = 6; and Pantelleria: n = 7). The sampling was performed within a depth range (11-16 m) known to have high population density and where the reproductive biology (Goffredo et al 2012a), biometry and abundance (Caroselli et al 2015), and growth and population demography have been studied (Caroselli et al 2016). Patches were sampled on the vault of crevices, except at the Elba site, where samples were collected under the wings of a sunken plane wreck.…”

“…Sexual maturity is reached at a size of *6.1 mm (Marchini et al 2015), corresponding to *7-yr-old polyps. Its abundance and age-length relationship are homogenous along the western Italian coast, while demographic parameters indicate less stable populations and juvenile deficits with increasing SR (i.e., going southward; Caroselli et al 2016).…”