Investigations concerning the hydrology, sedimentology and floristics of seasonal freshwater rockpools in the Maltese island

Abstract

A monitoring study on temporary Mediterranean rock-pools was conducted to the north of Malta, an island in the central Mediterranean region. The study, covering a period of 182 days focused on the wet cycle (autumn through winter) of rock-pools found on the garrigue at San Pawl tat-Targa, Naxxar. Several factors were studied, including climate, geomorphology, hydrology and percent vegetative cover. Climate was typically Mediterranean, with mean air temperatures reaching 17.8 ± 4.03° C (min and max for period being l0°C and 26 °C respectively), mean wind speeds 4.5 on the Beaufort scale (min and max for period being 2 and 8 respectively), and a total precipitation of 108.7mm. Rock-pools showed a wide variation in respect of volume, surface area, sediment and water level inundation. Variances obtained for geo-morphological and hydrological measurements were high and revealed the need for better pre-selection criterions and indicators for categorization of the pools in future studies. One of the indicators may possibly be relevant for Malta, was likely to be the Water to Sediment Ratio, (hereby termed WSR), since values relating to mean water level, hydrology and hydro-period did not provide enough evidence for correlations with mean Percent Vegetative Cover (PVC<moanJ) ( r1= 0.0703, P=0.0031) However, fairly significant correlations for PVC (mo••> were obtained with pool depth (r2= 0.715, P=0.0001), pool volume ( r1= 0.405, P= 0.003), sediment depth (r2= 0.582, P = 0.001), soil saturation levels (r2= 0.596, P= 0.0012). Statistical correlations with mean Percent Vegetative Cover (PVC<mo••>) with WSR gave inconclusive results(r2 =- 0.024, P=0.002); whereas correlations with maximum Percent Vegetative Cover PVC <max> were significantly positive ( r1= 0.310, P=0.002), indicating that must be some optimal value for WSR. In conclusion, the research study reveals that more research is required, to disclose and uncover, the underlying and intricate inter-relationships between biotic and abiotic elements, that help shape and configure, these unique ecosystems.