Land-Sea Interactions in Punta China(Baja California,Mexico):Addressing Anthropic and Natural Disturbances in a Retrospective Context

摘要

In extensive SCUBA-diving surveys of kelp forests along 350 km of the Baja California peninsula coastline from the US-México borderline to Sacramento Reef, benthic species richness has been satisfactorily explained by environmental structural features such as bottom rugosity. However, values at Punta China embayment (PCE) departed significantly from the model whereas the adjacent Santo Tomás cove (STC) did not. In addition, in August 20, 2011, visibility was under 1 m at PCE and over 10 m at STC;these conditions presumably reflect the influence of the limestone extraction industry located on land. In order to investigate the case allowing for temporal comparisons, we set a regional research scenario similar to a 1993 pioneer study, comprising PCE and two contrasting sites (STC to the North, and San José embayment, SJE, to the South). Land and sea side were addressed separately, and a 1950-2012 time-span period was set in order to perform the analysis of retrospective data. Our results suggest that the current scenario results from the combined influence of a local, anthropic and chronic land-based disturbance represented by the progressive expansion of limestone extraction industry, and the episodic influence of a natural, large scale and acute disturbance represented by the 1982-83 and 1997-98 El Nino events. The influence of both driving forces, however, is not necessarily equally distributed in space, yielding a regional mosaic of natural and social conditions. Our results confirm and expand previous knowledge in the area, and may contribute to?future basic and applied research.