Late in summer 2003, extensive mass mortality of at least 25 rocky benthic macro-invertebrate species (mainly gorgonians and sponges) was observed in the entire Northwestern (NW) Mediterranean region, affecting several thousand kilometers of coastline. We were able to characterize the mortality event by studying six areas covering the main regions of the NW Mediterranean basin. The degree of impact on each study area was quantified at 49 sites by estimating the proportion of colonies affected in populations of several gorgonian species compared with reference data obtained in years without mortality signs. According to these data, the western areas (Catalan coast and Balearic Islands) were the least affected, while the central areas (Provence coast and Corsica-Sardinia) showed a moderate impact. The northernmost and eastern areas (Gulf of Genoa and Gulf of Naples) displayed the highest impact, with almost 80% of gorgonian colonies affected. The heat wave of 2003 in Europe caused an anomalous warming of seawater, which reached the highest temperatures ever recorded in the studied regions, between 1 and 3 degrees C above the climatic values (mean and maximum). Because this exceptional warming was observed in the depth ranges most affected by the mortality, it seems likely that the 2003 anomalous temperature played a key role in the observed mortality event. A correlation analysis between temperature conditions and degree of impact seems to support this hypothesis. Under the present climate warming trend, new mass mortality events may occur in the near future, possibly driving a major biodiversity crisis in the Mediterranean Sea

We present the Wrst study of the eVects of ocean acidiWcation on settlement of benthic invertebrates and microfauna. ArtiWcial collectors were placed for 1 month along pH gradients at CO 2 vents oV Ischia (Tyrrhenian Sea, Italy). Seventy-nine taxa were identiWed from six main taxonomic groups (foraminiferans, nematodes, polychaetes, molluscs, crustaceans and chaetognaths). Calcareous foraminiferans, serpulid polychaetes, gastropods and bivalves showed highly signiWcant reductions in recruitment to the collectors as pCO 2 rose from normal (336-341 ppm, pH 8.09-8.15) to high levels (886-5,148 ppm) causing acidi-Wed conditions near the vents (pH 7.08-7.79). Only the syllid polychaete Syllis prolifera had higher abundances at the most acidiWed station, although a wide range of polychaetes and small crustaceans was able to settle and survive under these conditions. A few taxa (Amphiglena mediterranea, Leptochelia dubia, Caprella acanthifera) were particularly abundant at stations acidiWed by intermediate amounts of CO 2 (pH 7.41-7.99). These results show that increased levels of CO 2 can profoundly aVect the settlement of a wide range of benthic organisms. Communicated by F. Bulleri. M. Cigliano and M. C. Gambi contributed equally.

Late in summer 2003, extensive mass mortality of at least 25 rocky benthic macroinvertebrate species (mainly gorgonians and sponges) was observed in the entire Northwestern (NW) Mediterranean region, affecting several thousand kilometers of coastline. We were able to characterize the mortality event by studying six areas covering the main regions of the NW Mediterranean basin. The degree of impact on each study area was quantified at 49 sites by estimating the proportion of colonies affected in populations of several gorgonian species compared with reference data obtained in years without mortality signs. According to these data, the western areas (Catalan coast and Balearic Islands) were the least affected, while the central areas (Provence coast and Corsica-Sardinia) showed a moderate impact. The northernmost and eastern areas (Gulf of Genoa and Gulf of Naples) displayed the highest impact, with almost 80% of gorgonian colonies affected. The heat wave of 2003 in Europe caused an anomalous warming of seawater, which reached the highest temperatures ever recorded in the studied regions, between 1 and 3 1C above the climatic values (mean and maximum). Because this exceptional warming was observed in the depth ranges most affected by the mortality, it seems likely that the 2003 anomalous temperature played a key role in the observed mortality event. A correlation analysis between temperature conditions and degree of impact seems to support this hypothesis. Under the present climate warming trend, new mass mortality events may occur in the near future, possibly driving a major biodiversity crisis in the Mediterranean Sea.

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SUMMARY: Observations on the reproductive features are provided for three species of Eunicidae (Lysidice ninetta Audouin and Milne Edwards, Lysidice collaris Grube and Nematonereis unicornis (Grube)). They all occur in Posidonia oceanica meadows as borers in the sheaths. The material examined was collected during several studies on P. oceanica meadows conducted at various times of the year and in different years along the coasts of Sardinia and the Ischia islands (Tyrrhenian Sea), and Otranto (Southern Adriatic Sea). All individuals of the three species were measured (width 3 rd chaetiger, diameter of eyes), and checked for presence of gametes. In each of the females recognized, egg diameter was measured. To integrate the observations, living specimens were collected in March 2003 and reared in the laboratory until August 2003 to check for gamete maturation; mature males were fixed for analysis of the structure of the spermatozoa by transmission electron microscopy (TEM). All three species studied are gonochoric. For both species of Lysidice gametes occurred in individuals with a width greater than 0.8 mm. The overall scarcity of mature males and females observed with respect to the total number of specimens collected is probably due to the dimensional constraint exerted by the sheaths. In Lysidice spp. specimens with small developing oocytes were observed in January-February and reached their maximum diameter between June and August (157 μm). Gametes were located mainly in the posterior part of the body, and an enlargement of the eyes (almost doubled in size) characterized mature specimens close to spawning. N. unicornis is a smaller species, and it is less frequent in Posidonia sheaths than Lysidice spp.; individuals with gametes had a width greater than 0.55 mm. A few mature specimens were observed between March and May with a maximum egg diameter of about 155 μm. In this species maturation of the gametes is coupled with a huge enlargement of the eyes (ten-times larger than in immature individuals), while the posterior part of the body is swollen and full of mature gametes, indicating reproduction by schizogamy. Analysis of mature spermatozoa of the three eunicids revealed a similar morphology, which is that of an "ectaquasperm" type, typical of many free-spawning species with external fertilization. The nucleus is round and globose (2.5 μm diameter) and the acrosome, slightly different among the three species, has the general shape of a truncate sub-cone.Keywords: Polychaetes, Eunicidae, Lysidice, Nematonereis, reproductive biology, Posidonia oceanica, Mediterranean Sea. RESUMEN: OBSERVACIONES SOBRE LAS CARACTERÍSTICAS REPRODUCTORAS DE TRES ESPECIES DE EUNICIDAE (POLYCHAETA) ASO-CIADAS A PRADERAS DELA FANERÓGAMA MARINA POSIDONIA OCEANICA EN EL MAR MEDITERRÁNEO. -Se discuten algunas caracteristicas generales de la biología de la reproducción de tres especies de poliquetos Eunicidae (Lysidice ninetta Audouin and MilneEdwards, Lysidice collaris Grube y Nematonereis unicornis (Grube)). Estas especies fueron obte...

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