No abstract

Desde la década de 1960, se han realizado estudios para comprender el proceso de calcificación que llevan a cabo los corales hermatípicos y conocer los factores que limitan su crecimiento. Wells (1963) determinó que los parámetros de crecimiento coralino guardan una relación directa con las variaciones estacionales en las condiciones ambientales. Calcification of the main reef-building coral species on the Pacific coast of southern Mexico Calcificación de las principales especies de corales constructoras de arrecifes en la costa del Pacífico del sur de México

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Coral growth is an important metric of coral health and underpins reef-scale functional attributes such as structural complexity and calcium carbonate production. There persists, however, a paucity of growth data for most reef-building regions, especially for coral species whose skeletal architecture prevents the use of traditional methods such as coring and Alizarin staining. We used structure-from-motion photogrammetry to quantify a range of colony-scale growth metrics for six coral species in the Mexican Caribbean and present a newly developed workflow to measure colony volume change over time. Our results provide the first growth metrics for two species that are now major space occupiers on Caribbean reefs, Agaricia agaricites and Agaricia tenuifolia. We also document higher linear extension, volume increase and calcification rates within back reef compared to fore reef environments for four other common species: Orbicella faveolata, Porites astreoides, Siderastrea siderea and Pseudodiploria strigosa. Linear extension rates in our study were lower than those obtained via computed tomography (CT) scans of coral cores from the same sites, as the photogrammetry method averages growth in all dimensions, while the CT method depicts growth only along the main growth axis (upwards). The comparison of direct volume change versus potential volume increase calculated from linear extension emphasizes the importance of assessing whole colony growth to improve calcification estimates. The method presented here provides an approach that can generate accurate calcification estimates alongside a range of other whole-colony growth metrics in a non-invasive way.

The discovery of alternating growth bands in the skeletons of massive corals led to the possibility of using them as environmental indicators. However, skeleton formation is the result of the growth of thousands of polyps depositing millimeter-sized CaCO 3 structures, called corallites. Nevertheless, the orientation of the corallite trajectories and their position with respect to the colony could be altering the information obtained from the skeleton. In this sense, to obtain reliable information from coral skeletons, it is necessary to understand how polyp population growth influences coral growth rates. For this reason, we present a study that combines computed tomography image segmentation, optical densitometry, and demographic equations to follow the trajectory of corallites in order to model coral growth from the replication of its corallites and understand the responses in terms of their growth. We observed that both corallite replication and skeletal growth characteristics vary significantly according to the position they occupy within the colony. The central zone of the colony promotes corallite replication, and it is in this zone that we measured the highest values of extension and calcification. These variations in vegetative and skeletal growth are possibly in accordance with the variability of available resources and environmental stimuli in different zones of the skeleton. This approach will allow us to explore future lines of research associated with the size limits of different coral species and to observe how different drivers modulate polyp budding.