Colony size-frequency distributions of scleractinian coral populations: spatial and interspecific variation

Citation
Eh. Meesters et al., Colony size-frequency distributions of scleractinian coral populations: spatial and interspecific variation, MAR ECOL-PR, 209, 2001, pp. 43-54
Citations number
46
Categorie Soggetti
Aquatic Sciences
Journal title
MARINE ECOLOGY-PROGRESS SERIES
ISSN journal
01718630 → ACNP
Volume
209
Year of publication
2001
Pages
43 - 54
Database
ISI
SICI code
0171-8630(2001)209:<43:CSDOSC>2.0.ZU;2-V
Abstract
Colony size is an important characteristic for clonal modular organisms suc h as corals because life-history processes, e.g. reproduction and mortality , are strongly related to size. These processes are affected by the environ ment, and size-frequency distributions of coral populations provide informa tion on the responses of populations to environmental conditions. We hypoth esised that the size-frequency structure of coral populations in degraded e nvironments would differ from those in a more pristine environment. We used log-transformed colony-size data of 13 coral species from the fringing ree fs of Curacao, Netherlands Antilles. Data were collected at 4 sites. repres enting 2 environments: a heavily urbanised coastal area with degraded reefs , and an upstream control area. Population structure was dependent on speci es and site. Size-frequency distributions of the same species from differen t sites were twice as similar as distributions of different species, indica ting the strong effects of various life-history traits among species. Site effects were indicated by significant differences between distributions of Ii species at 4 sites. Mean colony size Varied up to an order of magnitude between species, and much less between sites; however, in 10 species mean c olony size was also significantly different among the 4 sites. The pattern of the differences was not consistent among species, indicating that mean c olony size in degraded sites was higher for some species and lower for othe rs. Parameters describing the shape of the population appeared to reflect a general response to reef condition. In the degraded area, frequency distri butions tended to show increased negative skewness, occasionally extreme po sitive kurtosis, and smaller standard deviations: II populations were gener ally more negatively skewed, with the bulk of the population concentrated i n the larger size classes; kurtosis was on average higher and extremely pea ked; and standard deviations indicated that colony size varied less. This e vidence suggests lower recruitment and higher partial mortality in larger c olonies in this area. Lower recruitment decreased the influx into the small er size classes of the populations. and higher partial colony-mortality dec reased the proportion of colonies in the higher size classes while simultan eously increasing the proportion of colonies in the medium-sized classes. S pecies that attained large sizes (indicative of great age) appeared to have size-frequency distributions skewed to the left, while small species were more skewed to the right. The data indicate a general dichotomy in coral li fe-history strategies with respect to colony size. with small species gener ally having a shorter lifespan and reproduction being relatively frequent a nd successful. Thus, new input into smaller size classes occurs continuousl y. Species that attain large sizes live longer and are less dependent on fr equent recruitment, and consequently populations tend to become 'impoverish ed' in small colonies, resulting in size-frequency distributions that are s kewed to the left. Based on changes in population structure, this research indicates that some species, such as Colpophyllia natans and Diploria labyr inthiformis, are relatively sensitive to environmental conditions.