Abstract
In extensive SCUBA-diving surveys of kelp forests along 350 km of the Baja California peninsula coastline from the US-Mexico 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 adja- cent Santo Tomas 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 ex- traction industry located on land. In order to investigate the case allowing for temporal compari- sons, we set a regional research scenario similar to a 1993 pioneer study, comprising PCE and two contrasting sites (STC to the North, and San Jose 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 com- bined influence of a local, anthropic and chronic land-based disturbance represented by the pro- gressive 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 influ- ence of both driving forces, however, is not necessarily equally distributed in space, yielding a re- gional mosaic of natural and social conditions. Our results confirm and expand previous know- ledge in the area, and may contribute to future basic and applied research. * Corresponding author.
Highlights
The analysis of retrospective data is a well-established procedure for tracking and organizing the ecological and social events that occur in a given area of interest in space and time
For the 1950-2012 period, a coastal scenario encompassing three embayments that display the combined yet uneven influence of a local, anthropic and chronic land-based disturbance represented by the progressive expansion of limestone extraction industry, and the episodic influence of natural, large scale and acute disturbances represented by the 1982-83 and 1997-98 El Niño events, yielding a regional mosaic of natural and social conditions
We posed two basic research questions: what elements would be necessary to explain quite different visibility at two embayments only few km apart? How would this be related to the fact that one site fitted the rugosity-species richness model whereas the other did not? This in turn brought to mind a 1993 pioneer survey [4] in which a gradient of CaCO3 in sediments, as well as changes in algal abundance and species composition occurred in Punta China embayment (PCE) according to the influence of sediments originated at the barge-loading and deposit sites of the limestone extraction industry located on land, whereas contrasting values occurred at Santo Tomás cove (STC) to the North, and San José embayment, SJE, to the South (Figure 3)
Summary
The analysis of retrospective data is a well-established procedure for tracking and organizing the ecological and social events that occur in a given area of interest in space and time. Understanding processes underlying observed patterns is challenging in coastal scenarios, where land uses are mainly associated with the solid face and the liquid face is associated with the arrival of natural and man-made items from the adjacent land In such a context, the systematic analysis of retrospective data is relevant in order to address the chain of causal relationships between human activities and changes in the ecological system, in order to identify and organize the state of physical and biotic elements of the territory, as well as social factors acting to provide goods and services, or, in a management-oriented approach, in order to organize all the former and encourage conflict resolution and sustainable use projection [2] [3].
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