Long-term comparison of macrobenthos within the soft bottoms of the Bay of Banyuls-sur-mer (northwestern Mediterranean Sea)

The macrofauna present at seven of the stations within the Bay of Banyuls-sur-mer (northwestern Mediterranean) initially sampled by Guille during the late 1960s was reassessed in 1994, using the same gear and techniques as those used during the reference study. Results showed an increase both in the number of species and of individuals (all species pooled) per unit of surface area at nearly all stations. This trend was not significant for total biomass. The most important changes were linked to the increase of the polychaete Ditrupa arietina (both within the Spisula subtruncata and the Nephtys hombergii community) and the decrease of the polychaetes Scoloplos armiger and Notomastus latericeus within the Scoloplos armiger community. The possible causes underlying these changes are discussed. The most probable cause is considered to be a slight modification of sediment composition (decrease of fine material in the sediment) within the Spisula subtruncata, the Nephtys hombergii and the Scoloplos armiger communities. Temporal changes in (1) Rhone river input, (2) small coastal river inputs, and (3) frequency of easterly storms may all have contributed to such a decrease.     

Ecological and Life History Characteristics of Botryllus schlosseri Tunicata Populations Inhabiting Undersurface Shallow-Water Stones

Abstract. Populations of Botryllus schlosseri PALLAS 1772. a cosmopolitan colonial ascidian. were examined on the undersurface of stones for the first time in three adjoining localities along the Israeli Mediterranean coast. A two-year study of 1589 stones which were inhabited by 1345 colonies, revealed that colony coverage was < 1.5 % of the total available substrate area; values were highest in spring, lowest in winter. The two years differed significantly in the number of colonies · m ², and these numbers were correlated with mean seawater temperatures. Most of the stones contained 1–5 Botryllus colonies year-round; no significant correlation was found between number and stone size. The brown morph was dominant 80 % at all three localities. The distribution of other colour morphs differed between localities. Reproductive colonies were either hermaphroditic or contained male gonads only. Peak reproduction was in the spring, but did not correlate with seawater temperatures. While colony size ranged between I and 1I55zooids, sexually mature colonies consisted of 171–273 zooids on the average, compared with 37–90 zooids for sterile colonies. The three populations differed significantly in several ecological and life history characteristics. This further confirmed past studies indicating that Botryllus populations are characteristically divided into local subpopulations exhibiting microgeographic differences in life history patterns. The results are compared with the accumulated data on other world-wide Botryllus populations residing in other habitats.     

Biogeographic characterization of Mediterranean and Black Seas faunal provinces using GIS procedures

To identify Mediterranean and Black Seas areas where similar marine faunal provinces occur, geographical distribution maps of 536 species of actual or potential interest to fisheries have been digitized, using GIS software, and three different ecological areas have been delimited by depth, separated by the 200 and 1000 m isobaths. Information on the species ranges was taken mainly from the maps and the texts of the FAO Species Identification Sheets covering the region, and complemented by other sources when necessary. All the distribution maps have then been overlaid by a grid of points at regular intervals every half degree of latitude and longitude. This allowed creation of a matrix of presence or absence of the species at each point from which species richness maps have been generated. The species richness in the Mediterranean proper shows the same negative gradient eastwards that has been observed for nutrients, while the low number of species in the Black Sea could be linked to the fragility and recent fast degradation of this ecosystem. Through the calculation of 65 dissimilarity indices from 50 contiguous points along the coastline and the species richness maps, the region has been divided into nine faunal provinces. These faunal provinces have then been compared with the ten Mediterranean and Black Seas divisions used by the GFCM for statistical purposes, revealing few differences between the two classifications. The definition of faunal provinces in a region when deciding upon Natural Management Areas, and the appropriate GIS approach to be followed, are discussed.     

An Analysis of the Coastal Fish Assemblage of the Ustica Island Marine Reserve (Mediterranean Sea)

A study of the coastal fish assemblages in the marine park of Ustica Island (Southern Tyrrhenian Sea, Mediterranean) was conducted from June 1994 to September 1995 and from June 1996 to September 1997. The principal aims of the research were to: (1) define the faunistic features of local fish communities; (2) assess the effectiveness of the protection regime of the marine park on the fish assemblages ('reserve effect'); (3) provide information on the distribution of some Epinephelus and Diplodus species in the shallowest depth zone of the island. During seasonal surveys, underwater visual censuses were carried out at several sites located in three zones of the island, each with a different level of protection. Observations were made along 250 m² transects at 3–5, 10–15 and 25–30 m depth ranges. Additional surveys were made by SCUBA diving and snorkelling. A statistically significant effect of depth on the fish community parameters was observed, whereas differences linked to protection level, zones, sites and seasons were not significant. The abundance and frequency of occurrence of some species, particularly dusky grouper Epinephelus marginatus , were positively correlated with the degree of protection of the different zones of the marine park. Certain sites of the island are important as nursery areas for three species of the genus Diplodus ( i.e., D. puntazzo, D. sargus and D. vulgaris ).     

Evidences of the Blake and Iceland Basin magnetic excursions in southeastern Iberia and chronological implications for the Padul sedimentary record

The Padul-15-05 sediment core provides an exceptional perspective of the paleoenvironmental and climate change in the Western Mediterranean region for the last ca. 200 kyr. However, even though a robust chronology mainly relying on radiometric dating is available for the last 50 ka, the chronology for the older sediments is not yet fully resolved. Ages for the bottom part of the core (>21 m) were previously inferred from amino-acid racemization dating and sediment accumulation rates. In this work, we provide a more accurate chronology for the older part (>100 kyr) of the Padul-15-05 sediment core record based on the recognition of past Earth's magnetic excursions. We identify an interval prone of reversed polarity samples close to MIS-5e/5 d transition that we correlate to the Blake geomagnetic excursion (116.5 kyr–112 kyr). In addition, we identify an interval of low inclinations and two reversed samples that we interpret as the Iceland Basin geomagnetic excursion (192.7 kyr–187.7 kyr: wide scenario of VGP <40°). Our new results, which include IRM acquisition curves that contribute to understand the magnetic mineralogy, enhances the robustness of the age model for the Padul-15-05 sedimentary sequence by adding an independent age dataset with new accurate tie-points. Our refined age control together with the available paleoenvironmental and paleoclimate multiproxy data provide insightful information to unveil the response of the western Mediterranean environments to regional environmental and climate change.     

Pathlines of pollutant migration in groundwater of the Visakhapatnam urban area,India

The groundwater regime in the north‐western part of the Visakhapatnam urban area was polluted as early as 1981 by discharge of untreated industrial effluent from a Hindustan Polymers Limited (HPL) plant. A total dissolved solids (TDS) concentration of surficial effluent up to 6500 mg/l and of groundwater in the range 3000–4200 mg/l has been reported in the environs of the HPL plant during May 1992. Groundwater occurs under water table conditions. The groundwater flow model was simulated as a single layer aquifer, using MODFLOW and FLOWPATH computer models. Aquifer parameters were estimated and the value of effective porosity assumed. The water table configuration was mapped in May 1981 using 33 observation wells. The calibrated hydraulic head distribution was used to compute the velocity field using the effective porosity values. The flow paths of groundwater migration from the source locations up to 2002 AD were predicted. Pathlines of particles in the groundwater indicated a predominant north‐east and south‐west migration of groundwater pollution in the area. Copyright © 1999 John Wiley & Sons, Ltd.     

Midlittoral polychaete communities in the Eastern Mediterranean Sea: new information from the implementation of the Natural Geography in Shore Areas (NaGISA) protocol and comparisons at local and regional scales

The aim of this study was to attempt to fill current knowledge gaps on midlittoral Mediterranean biodiversity at local and regional scales, by using benthic polychaetes as a model taxon. Two different data sets were analysed: (i) a quantitative data set from the two Natural Geography in Shore Areas (NaGISA) study sites in Crete and (ii) a qualitative data set from multiple sites across the Mediterranean. At the local scale, the results provide evidence that (i) discrete species communities are formed in midlittoral Mediterranean habitats, which vary by geographical location and year, depending on the scale of observation; (ii) macrophyte coverage and Chl‐a are the only environmental variables associated, albeit weakly, with the above pattern; (iii) although naturally disturbed, the Cretan NaGISA sites do not seem to experience any anthropogenic stress; (iv) environmental heterogeneity and history seem to be much less important in shaping the polychaete communities than inter‐specific interactions; however, it is not possible to specify at this stage whether local or regional processes or even their interactions may shape the polychaete communities. At the regional scale, the results indicate that (i) the only factor that seems to be involved in the regional pattern is the identity of the study providing the data sets, which implies variability and bias in how research projects are carried out, from the sampling design through to data collection and analysis; (ii) the Cretan NaGISA sites may be considered as representative of the habitat in the Mediterranean, under certain conditions.     

Seismic indicators of focused fluid flow and cross-evaporitic seepage in the Eastern Mediterranean

We present for the first time a synthesis of the evidence of focused fluid flow in the Eastern Mediterranean, providing an updated record that includes recent and past occurrences through the last ca. 6 My of evolution of the basin. We do this by adding the interpretation of a previously unpublished regional 2D seismic dataset to the existing occurrences of focused fluid flow reported in the literature. Our interpretation shows a high number (141) of focused fluid flow features, which span the stratigraphic interval from late Miocene to Recent. Of these features, (82) are at the seabed, and (59) are buried. The previous published record is more difficult to quantify, but in comparison shows an overwhelming majority of seabed features, with only rare examples of buried features.The spectrum of the buried and seabed features covers pockmarks, pipes, mud volcanoes, clastic intrusions and collapse structures. Clustering of the fluid flow features is observed at different times in specific areas, including the Nile Cone, and the Levant, Herodotus, Cyprus and Latakia basins. With the buried record, we are able to highlight the evolution of the leakage points through time. Focused fluid flow venting has been occurring since the onset of the Messinian Salinity Crisis and the start of basinwide deposition of evaporites. We focus in particular on seismic indicators of leakage through evaporites, and of sub-evaporitic source for fluids and remobilised sediments. We also discuss the role of the evaporites as a seal to ascending fluids, and in which circumstances they can be breached.Fluids (and associated remobilised sediments) are sourced from different intervals, from the sub- and supra-evaporitic section, and possibly within the evaporites. Only a minor proportion of the fluid flow features are certainly sourced from below the Messinian evaporites, and most of them are located in the Nile-Levant-Eratosthenes areas. The few examples of pathways that are able to cross thick, undeformed and well preserved evaporites are typically correlated to overpressure release and hydrofracturing. This confirms that the evaporites do act regionally as a very good seal as expected, while fluids are able to cross the evaporites only in their most extreme expression, i.e. in near-lithostathic overpressure conditions. This is confirmed by our observations made in the Eastern Mediterranean, where in the presence of relatively undisturbed evaporites, cross-evaporite vertical fluid pathways are only observed at the high end of the flux-pressure range, and involve sediment remobilisation. Maps combining these different elements can be used to detect areas potentially more prone to breaching.