Guillem X. Pons

Spatial and seasonal variability of the macro-invertebrate community of a rocky coast in Mallorca (Balearic Islands): implications for bioerosion

The number of the main macro-invertebrate species grazing on the microalgal film on rocky coasts was evaluated at six closely located stations on Mallorca (Balearic Islands). The main bioerosive species at the sites studied were Melaraphe neritoides (L., 1758), Patella rustica (L., 1758), Monodonta turbinata (Born, 1780) and Lepidochitona corrugata (Reeve, 1848). The transects considered shared the same general environmental conditions and species pool. The aim of this study was to compare the effects exerted by the vertical gradient with those exerted by other sets of environmental variables. These sets were, namely, (1) inter-seasonal differences, (2) inter-transect differences (comprising degree of wave-exposure and lithological differences) and (3) effects of the micro-morphology (i.e., crevices, basin pools and other small-scale structures). The main null hypothesis verified was that species composition remains constant after assessing the effect of the vertical gradient. This hypothesis is largely rejected here. The main factor modelling the species composition was the vertical gradient (accounting for 31.6% of variability) whereas the percentages of variability yielded by the other sets individually were smaller but significant (P<0.001). Inter-transect differences (including degree of wave exposure and lithology) accounted for 24.9% of the variability. Seasonal differences accounted for 6.3%, small-scale morphology for 4.5%, and wave-height for 1.6%. The main conclusions obtained from these results are that the most basal strip of the coastline undergoes the largest bioerosive rates. Similarly, the sites exposed to wave action will undergo a larger bioerosive impact than the sheltered sites (possibly because they are more damp). These biotic and abiotic effects taken together would result in a maximisation of erosion rates in areas that are porous, exposed and located near the sea.

Exploring rock coast bioerosion: rock fragment intestine transit time and erosion rates computation of the gastropod Monodonta articulata (Lamarck, 1822)

ABSTRACT Vidal, M., Fornós, J.J., Gómez-Pujol, L., Palmer, M., Pons, G.X., Balaguer, P., 2013. Exploring rock coast bioerosion: rock fragment intestine transit time and erosion rates computation of the gastropod Monodonta articulata (Lamarck, 1822) Coastal rock bioerosion research is well established. Otherwise there is the need to improve the way in which bioerosion rates are calculated. Since the findings of McLean (1967), it has been assumed that the dry weight of pellets collected after 24 hours provides an estimate of the amount of organism daily erosion. This is an assumption that relies largely on initial experimental procedures lacking any empirical ascertainment. This paper assess what is the transit time of the rock fragments through the intestine of the gastropod Monodonta articulata, and the implications of applicability of this temporal framework to the computation of a more precise estimation of the bioerosion throughout laboratory experiments. Our results suggest that for the gastropod Monodonta articulata, the major part of the eroded and ingested rock is defecated during feeding time. According to this, the confidence of bioerosion rates values calculated by means of faecal pellet collection based on 24-hour time frame can be concluded. Erosion rates for M. articulata activity in limestone rock samples have been estimated to range between 8.00 mg·ind−1·day−1 to 10.10 mg·ind−1·day−1.

Beaches of Ibiza and Formentera (Balearic Islands): a classification based on their environmental features, tourism use and management

ABSTRACT Roig-Munar, F.X., Mir-Gual, M., Rodríguez-Perea, A., Pons, G.X., Martín-Prieto, J.A., Gelabert, B. and Blázquez, M., 2013. Beaches of Ibiza and Formentera (Balearic Islands): a classification based on their environmental features, tourism use and management, In order to define their character a total of 100 beaches of Ibiza (76) and Formentera (24) are analyzed on the basis of 35 variables of beach use, state and management. We take as a reference a primary classification where three types of beaches have been considered; urban beaches (A), semi-natural beaches with urban features (B), and natural beaches (C). Departing from this scenario, and taking into account the identified variables, statistical analysis (Cluster and PCA analysis) have been done in the sense of identifying the current state of each beach and the differences among them. Currently many of the beaches of Ibiza are urban beaches (A). Furthermore the results suggest a potential trend that some of natural beaches (B-C) can become to A type in the next future. Understanding this classification, and also the recent history of the management applied in the study units, allow predicting trend scenarios. In this sense, management changes should be proposed in order to improve their current situation, and drive them toward a better conservation status.

The Rocky Coasts of Balearic Islands

Balearic Islands are located in the centre of Western Mediterranean and is composed by five major islands (from biggest to smallest): Mallorca, Menorca, Ibiza, Formentera and Archipelago of Cabrera. Mallorca located at the centre of archipelago has an extension of 3,636 km2, Menorca, located at the Northeast, has an extension of 695 km2, Ibiza and Formentera, called Pitiuses Islands and located at the South, has an extension of 572 and 82 km2 respectively. Mallorca is the island which have a higher coastal length with 842 km (including Archipelago of Cabrera), Menorca follows with 433 km, Ibiza has 334 km and Formentera 115 km. These coasts, and specially the rocky shores, are the result of the geological and geomorphological characteristics and modelling processes, as fluvial, karst, bioerosion and mass movements, between others conditioned by maritime climate which have configured the structural units of each island. According to general results for the entire archipelago, the percentage between rocky coasts or coasts formed by cohesive materials and beach coasts or coasts formed by non-cohesive materials is 80–20.

Description of erosion processes in Spratt Bight (San Andrés Island, Colombia) using Sequential End Point Rates (EPR)

ABSTRACT Martín-Prieto J.A., Roig-Munar, F.X., Pons G.X., Rodríguez-Perea A., Alvarado, M. and Mir-Gual M. 2013. Description of erosion processes in Spratt Bight (San Andrés Island, Colombia) using Sequential End Point Rates (EPR). San Andrés is a coral island located in the Colombian Caribbean, 700 km northwest of the main land. Twelve kilometers in length and three kilometers in width, it is one of the most populated islands with 2.612 inhabitants per square kilometer. Its economy is based on tourism. Despite being protected from storms and hurricanes by a chain of reefs that stretches across the north and east of the island, beaches suffer significant erosion. Spratt Bight is the biggest and the most important beach of the island. Temporal evolution of Spratt Bight was analyzed and the End Point Rate for several periods (from the year 1984 to 2010) has been calculated. Although beach nourishment between 1984 and 1990, erosive processes are dominant all over the beach. Erosion rates reach up to 35 m with an average of −1.3 m/year, in its central part. The other erosive sector is placed in the half north of the beach, with a maximum of 20 m and an average of −0.7 m/year. Detected erosion can be attributed to the construction of two perpendicular structures to the shoreline and a promenade located on top of the upper beach. The rigidity of these facilities does not allow the natural evolution of the beach, disconnecting the beach from the dunes and causing significant losses of sand by wind action.