Taxonomic and morphological descriptors reveal high benthic temporal variability in a Mediterranean marine submerged cave over a decade

Abstract

The effectiveness of monitoring programs in the marine environment is often limited by the scarcity of information concerning medium/long-term time series observations (years-decades) in complex and variable systems. Marine submerged caves, in particular, have received relatively low research effort, as they are confined and difficult to access ecosystems. In this study, we describe the spatio-temporal variations of sessile benthic assemblages along the exterior-interior axis of the Cerro-Gordo submarine cave (Granada, Spain), from 2007 to 2016 using taxonomic (e.g., major taxonomic groups) and morphological (i.e., growth forms) descriptors. In contrast to our initial expectations (higher stability in the inner cave sector), significant temporal variations of sessile community structure and morphology occurred in both external and internal cave sectors. In addition, higher spatial differences were encountered among opposite cave walls in the inner dark sector, which is probably explained by small-scale variability in topography and siltation rate. In the outer semi-dark sector, community structure was more heterogeneous, although generally similar between opposite walls. Among the descriptors used, the morphological one was able to detect greater spatio-temporal variation in the outer semi-dark sector, while the taxonomic descriptor was more suitable in the inner dark sector. These results could provide a basis for future monitoring programs.