Assessment of the ecological impact of the extreme storm of Sant Esteve’s Day (26 December 2008) on the littoral ecosystems of the north Mediterranean Spanish coasts. CSIC-PIEC 200430E599.
Preface
On 26th December 2008 an exceptionally severe easterly storm, the strongest recorded during the last half century, hit the Catalan coasts (Spanish NW Mediterranean). The storm caused three dead people and severe damage in public and private facilities and goods in a number of seaport municipalities. Wind gusts reached 100 km/h and waves over 14 m were recorded.
A number of first observations provided a body of evidences pointing to possible severe and large scale impacts in natural coastal benthic communities as well as in coastal fish populations. Abundant debris of algae, seagrasses, and dead fishes could be seen on the beaches of the central and northern areas of the Costa Brava. A particularly conspicuous case was that of the beach of L’Estartit. The atypically high sea water levels and high waves resulted in the seawater flooding the lowest stretch of the Ter River causing a massive mortality of freshwater fish and crabs. Once the storm died down, the heavy rains flushed the dead fish into the sea that were finally washed ashore by the residual high waves. The result was an unprecedented mix of freshwater and marine dead animals together with abundant macrophyte-derived debris lying on the neighbouring beaches.
After some first dives in the Medes Islands and Montgrí coasts by scientific divers of the “Parc Natural del Montgrí, les Illes Medes i el Baix Ter”, the Spanish National Research Council (CEAB and CMIMA), and the Ecology Department of the University of Barcelona, it could be established that the impact in the coastal marine benthos ranged from negligible to very severe. The magnitude of the impact depended on the type of community, exposure to the storm (orientation and depth), type of bottom (rock, cobbles, sand), and latitude (north, central, and south of the Catalan coast). An indisputable measure of the extreme intensity of the forces applied in the benthos during the storm was given by the observation of big rocks, several tonnes of weight, that had been turned upside down or rolled around the bottom. Broken or detached soft corals, rocky bottom seascapes totally denuded of their algal cover, seagrass meadows buried in sand or uprooted, detached fan mussels or date mussels, or missing rocky fish populations, were some of the most notorious impacts observed.
Owing to its exceptionality and ‘sensationalist’ potential, the phenomenon captured the attention of the local, regional, and national media who begun to make a series of scattered interviews in order to gather information about it. The extent and severity of the impacts declared was notably biased depending on the interests and background of the various sectors interviewed (scientists, administrations, underwater sports associations, tourist industry), triggering a considerable controversy.
Because of the unprecedented severity of the storm (the last similar one was recorded 61 years ago), it was soon made evident that this was the first opportunity to assess the effects of an extreme large scale meteorological perturbation on the structure and dynamics of coastal marine ecosystems using a wealth of human and technological resources. Besides, the initiative could benefit from the availability of a number of long-term data series of several benthic communities that are being monitored over the years by many researchers working in the area. This data series would allow for invaluable “before vs. after the storm” comparisons and for the correction for trends or cyclic patterns.
In view of the above, the uniqueness of the storm, and of the debate raised, the Research Group “Diversity and ecology of the marine benthos: from molecules to ecosystems” of the Centre for Advanced Studies of Blanes (CEAB-CSIC), elaborated an action plan to make a rigorous and multidisciplinary assessment of the impact caused by the storm on the various natural coastal communities. The plan included experts in benthic ecology of the Ecology Department of the University of Barcelona and of the Institute of Marine Sciences (ICM-CSIC), hydraulic engineers from the Polytechnic University of Barcelona (Laboratory of Marine Engineering) and from the University of Cantabria (Institute of Environmental Hydraulics), and experts of the Parc Natural del Montgrí, les Illes Medes i el Baix Ter (Generalitad de Catalunya). The initiative has been supported by around 50 participants (tenured, PhD students, and technicians), and has involved individuals and associations of professional fishermen and underwater sportsmen (spear fishermen and divers).
The plan of action was proposed for funding to the Spanish National Research Council (CSIC co-financed Special Intramural Projects) and granted only a few weeks later (Assessment of the ecological impact of the extreme storm of Sant Esteve -26 December 2008- on the littoral ecosystems of the north Mediterranean Spanish coasts. CSIC-PIEC 200430E599). The final report of this joint effort follows. In it we present an unprecedented compilation of the effects of an extreme meteorological event in the natural communities of coasts of the Mediterranean Sea.
The undersigning want to acknowledge and thank the outstanding enthusiasm and generosity shown by all the participants. Only their joint effort has made it possible to carry on with this unprecedented and, hopefully, useful initiative.
Miguel Ángel Mateo Mínguez
Antoni Garcia-Rubies
(Blanes, April 2012)