The antropogenic effects in the temporal affection of the structural complexity of the abrasion vermetid platforms

Abstract

The diversity of an ecosystem has two main characteristics to be considered: The specific richness and the relative abundance of each species. According to Whitaker, diversity can be considered within 3 scales: alpha, beta and gamma; defined the α-diversity the diversity of each “sample” by itself and β-diversity as a measure of the variation between samples. These parameters can give information of the ecological status of an ecosystem, and so, may be very interesting to quantify from the point of view of management. In this study, we have studied the diversity changes in a typical warm Mediterranean seascape, easily accessible for its study, the abrasion platforms. During this work, we focused in 3 locations with abrasion platforms through the coast of Alicante with different levels of anthropogenic pressure caused by the sewage outfall of Rincon de Leon, as the outflowing water carry a huge nutrient load that might enrich the environment; The Cabo de las Huertas, The beach of Agua Amarga and the Cabo de Santa Pola. At each location we differentiated 3 littoral zones (according to the distance to the outer margin of the platform) in order to evaluate the pattern of specific composition regarding the diversities (α and β) between locations and littoral zones. The results showed clear differences between the outer margin and the inner zones of the platform, at the same time as Santa Pola performed a lesser grade of diversity probably caused by the high sediment load. On the other hand, the algae communities of Agua Amarga, the closer location to the sewage outfall, were composed mainly by opportunistic and stress-tolerant species.