Effects of structural factors on upwelling fouling community, Southeast Brazil

Abstract

To assess the successional pattern of fouling organisms three hypotheses were tested: 1) a thermocline is caused by seasonal upwelling events, and therefore, depth influences the successional trajectory of the fouling community; 2) a reduction in the intensity of natural light of the substrate influences the fouling composition and the successional trajectory; 3) fish predation influences the community composition and its successional trajectory. During one year, up-facing and down-facing PVC panels on open, partially caged or fully caged, and placed at depths of 1.5 and 3.5 meters were monthly sampled by digital photograph to determine the community composition and by contact point to estimate the percent coverage of organisms. The upwelling impact provided different water masses, and light intensity was also a determining factor of the overall successional trajectory of the fouling community. After the installation of full and partial cages, differences were identified in the respective successional trajectories. The results of this study suggest that each physical factor or biological process can change the successional trajectory of the community, and the successional model (e.g., convergent, divergent, parallel, or cyclic) depends on the magnitudes of the determinants that act on the community at each stage of its trajectory.

Differential effects of coral-giant clam assemblages on biofouling formation

“…Biofouling formation onto a substrate, its growth rate and the type of species able to colonize this habitat are modulated by various interactions and involve complex biochemical, behavioral or physical mechanisms 9,13 . The external environment plays an important role in the biofouling formation, in particular through physical and chemical conditions 14,15 . For example, the availability of nutrients will play a critical role in the selection of early colonizers and the successive community composition of the biofouling 16 .…”