Bathymetric distribution and growth patterns of Bathypterois mediterraneus from the north-western Mediterranean Sea

Bathypterois mediterraneus was collected on 148 bottom trawls between 147 and 2251 m depth in the north-western Mediterranean. The species appeared below 700 m, its relative abundance and biomass increased progressively and reached its maximum at 2100-2300 m. A total of 1913 specimens were measured, ranging from 4 to 20 cm standard length ( L _s). The size composition with depth did not show any specific trend, and no modal progression could be distinguished in the length frequency distribution by cruise, with dominance of large fish (13-15 cm L _s) and a unimodal size pattern. The otoliths of 173 specimens were examined and showed the ring pattern common to teleost fishes. The age ranged between 0 and 15 years, although specimens of 4-12 years old were the most abundant. The growth parameters and the growth curve obtained from the interpretation of the growth rings in otoliths showed a low growth rate.     

Genetic differentiation of white sea bream within the Lion's Gulf and the Ligurian Sea (Mediterranean Sea)

An allozymic study was conducted on 190 individuals of white sea bream, Diplodus sargus sampled on five locations throughout the Lion's Gulf and the Ligurian Sea (Mediterranean Sea), in order to identify genetic structure. Electrophoretic surveys carried out on muscle and liver tissues identified 25 loci of which 12 were polymorphic ( P 0.95). G -test analysis shows significant differences on allelic frequencies between the five stations at six loci. Examination of the spatial structure was performed using Nei's distances and F statistics, and indicated significant genetic differences between three groups. A group which clustered Blanes (Spain), Marseille (France) and Livorno (Italy) where the absence of genetic difference can be explained by migration of larvae and adults along a coastal 'continuum'. The Elba sample (Italy) shows genetic divergence from other samples and this difference may result from isolation due to limited migration of larvae and adults. Banyuls (France), differs from all other stations. Several hypotheses are proposed to explain genetic patterns including local current systems, larval dispersal, geographic isolation and historical effects, and variation in the size classes of sampled individuals between sites.     

Biological Aspects of Medorippe lanata (Linnaeus, 1767) (Brachyura: Dorippidae) from the Eastern Ligurian Sea (Western Mediterranean)

The aim of the present study is to investigate the demographic structure and to identify some aspects of the biology of an exploited population of Medorippe lanata (Brachyura: Dorippidae) in the eastern Ligurian Sea, western Mediterranean. 1364 specimens (639 males and 725 females) of M. lanata were collected on a monthly basis from January to December 2001, in a wide area of the eastern Ligurian Sea usually exploited by the Viareggio ‘rapido’ trawl fleet. M. lanata represented an important fraction of the discard, both in weight and in number of individuals. Maximum abundance of this species occurred in late summer-early autumn (up to 3369 ind. km⁻² and 50.6 kg km⁻² in August). The overall females:males sex-ratio was 1.13:1, while the monthly sex-ratio did not differ statistically from 1:1 in all months, except in September and October, when females significantly outnumbered males. The sampled population was composed of two cohorts from November to April. Sizes ranged from 10 to 29 mm carapace length (CL) for females and from 9 to 29 mm CL for males. The von Bertalanffy growth curve, computed for both sexes, gave a higher growth rate in males than in females. Recently moulted males and females were observed throughout the year, except in summer, when the highest number of ovigerous females was present. Females with external eggs were collected from March to November, with peaks in August and September. The monthly evolution of the ovarian maturity stages showed no clear temporal trend. At 21 mm CL, 50% of females were ovigerous or showed macroscopically mature ovaries. According to the dimorphism in chelae size, the presence of adult males (post-puberty stage) was observed all year round, from 18 to 29 mm CL, without evident temporal trends.     

Biomass seasonality of Caulerpa taxifolia in the Mediterranean Sea

The biomass of the introduced and invasive alga Caulerpa taxifolia was measured monthly over one year at four different sites along the French Mediterranean coast at depths of 5 and 20 m in a sheltered and an exposed area. At the 5 m depth, C. taxifolia mean biomass ranged from 203 to 518 g dry wt. m⁻², while at the 20 m depth, it ranged from 62 to 466 g dry wt. m⁻². The study clearly shows that a major characteristic of C. taxifolia is its perennial life cycle with relatively high biomass values throughout the year, in different biotopes. This could be a factor in the broad ecological impact of C. taxifolia.     

Small-scale distribution of macroplankton and micronekton in the Ligurian Sea (Mediterranean Sea) as observed from the manned submersible Cyana

A series of eight submersible dives (the MIGRAGEL I cruise)was made during late April 1986 using the French submersibleCyana to investigate macrozooptankton in the upper 400–700m of the water column. Paired day and night dives were madeat stations 3, 6, 13 and 23 nautical miles off Cape Ferrat,near Villefranche-sur-Mer, France; the distances represent differentareas in the frontal system of the Ligurian Sea. Detailed day/nightvertical distribution data are shown for the most abundant species;these include the narcomedusa Solmissus albescens, teleost fishCyclothone spp., small appendiculanans (primarily Oikopleuraalbicans), large appendicularians (an undescribed oikopleurid),diphyid siphonophores (mostly Chelophyes appendiculata) andan abundant lobate ctenophore. Salps, pyrosomes, amphipods (Phroniumasedentaria), pteropods (Cavolinia inflexa), macroscopic ‘star-like’protozoa and marine snow are also briefly discussed. The coastalzone was dominated by small appendicularians in the upper layers,with other filter feeders including large appendicularians indeeper water—these just above a non-migratory populationof carnivorous Cyclothone. The carnivorous medusa Solmissusalbescens moved throughout the upper 600 m in the course ofits diel vertical migration. Offshore, carnivores were dominantthroughout the water column, with numerous diphyid siphonophoresin the upper layers, and Cyclothone, lobate ctenophores andmacroprotozoa abundant in deeper water. Solmissus was also present,and was more numerous offshore than in the coastal zone.     

Seasonal dynamics of zooplankton community in four Mediterranean reservoirs in humid area (Beni Mtir: north of Tunisia) and semi arid area (Lakhmes,Nabhana and Sidi Saâd: center of Tunisia)

The zooplankton community was studied in four Mediterranean reservoirs to assess the relative importance of environmental factors as determinants of zooplankton dynamic in the four seasons. The water temperature and hydrology variations affect the distribution of zooplankton. A positive correlation was established between the total zooplankton and the water temperature (r=0.9, n=9, p<0.05). Fourteen zooplankton species were identified. Seasonal changes in the density (ANOVA, F=3.7, d.f=36, p<0.01) and the biomass of total zooplankton (ANOVA, F=4.4, d.f=36, p<0.001) were observed. Our results suggest that planktivorous fish may not modify the zooplankton dynamics in Beni Mtir reservoir (oligotrophic). On the contrary, in Sidi Saâd reservoir (mesotrophic), fish predation has major effects on seasonal zooplankton dynamics.     

Benthic communities on a sandy Ligurian beach (NW Mediterranean)

The different components of the benthic community of a sandy microtidal beach (Arenzano) in Liguria (NW Mediterranean) were investigated during late spring (May) 2002 and 2003. Sampling was carried out in two transects, chosen in order to represent the characteristics of the entire beach and their eventual spatial variations. Each transect included two stations: one placed in the swash zone (SW) and one in the surf zone (SF). Although no significant differences were found in the sediment texture over the 2 years (t-tests p > 0.1 for all the granulometric fractions), notwithstanding an increase in the mean grain size (from 0.8 to 1.1 mm) between the sampling periods, 2002 was characterised by a higher quantity of organic matter (on average 14.4 vs. 3.6 gC m⁻² for the sum of proteins, carbohydrates and lipids) and higher bacterial biomass (on average 1.9 vs. 0.9 gC m⁻²). The metazoan assemblages (meiofauna and macrofauna) were also richer (density = 2.9 × 10⁵ vs. 1.0 × 10⁵ ind. m⁻², biomass = 0.09 vs. 0.03 gC m⁻² for meiofauna; density = 1988 vs. 739 ind. m⁻², biomass = 0.14 vs. 0.03 gC m⁻² for macrofauna) in 2002. A significant quantitative reduction (t-test for proteins, carbohydrates and lipids, at least p = 0.004) in the food supply in 2003 affected the abundance of the metazoans, as confirmed by a multivariate analysis that clearly differentiated the 2 years, and seemed to inhibit their relationships within the benthic food web. The bacterial biomass was always dominant, even under the least favourable trophic conditions, due to the ability of bacteria to adapt to a very harsh environment. Our results suggest that the food supply played an important role in the benthic community structures of the beach during late spring, bacteria being the key organisms within the benthic system. The communities seemed to be bottom-up controlled, while predation seemed to be irrelevant.     

Annual cycle and diversity of species and infraspecific taxa of Ceratium (Dinophyceae) in the Ligurian Sea,northwest Mediterranean1

We examined the well‐documented and species‐rich dinoflagellate genus Ceratium Schrank in the northwest Mediterranean Sea as a possible model for marine phytoplankton diversity and as a biological indicator of global climate change. First, we investigated the influence of counting effort; we then documented temporal changes in Ceratium specific and infraspecific taxa over 2 years (2002 and 2003) in the Villefranche Bay based on a monthly net sampling. Finally, we tried to identify factors associated with shifts in biodiversity. The calculation of taxonomic diversity, regularity, and richness were highly dependent on counting effort. We determined that a minimal sample volume of ～70 L was needed to obtain a good estimation of species richness. The annual cycle was characterized by a seasonal trend of high winter species richness followed by low spring biodiversity. Infraspecific variability not only appeared to depend on water temperature but also seemed to be influenced by bottom‐up control and was strongly affected by top‐down control. Thus, the occurrence of high concentrations of salps (Thalia democratica) and copepods larger than 2 mm (Calanus helgolandicus) coincided with a drastic decrease of Ceratium abundance and diversity during spring 2003. Ceratium is sensitive to both abiotic and biotic factors and could prove to be a good candidate as a biological indicator of global change.     

Enzymatic Activity on Sandy Beaches of the Ligurian Sea (NW Mediterranean)

Enzymatic activity was measured on two beaches of the Ligurian Sea (NW Mediterranean) during late spring and summer 2003. The detected activities (leucine aminopeptidase, β-glucosidase, α-glucosidase, and β-N-acetylglucosaminidase) were related to the available organic substrates (proteins and carbohydrates) and to the bacterial community (expressed in terms of abundance, biomass, and frequency of cell division). The very low chlorophyll a concentrations (never higher than 40 ng g⁻¹) suggested that heterotrophic microorganisms play a major role in the beach ecosystem. Enzymatic activities devoted to organic matter degradation were lower in the emerged part of the beaches and higher in the sites covered, permanently or temporarily, by seawater, suggesting that sea action enlivens the degradation processes. Leucine aminopeptidase ranged from 0.26 to 13.02 nmol g⁻¹h⁻¹, and β-glucosidase (the most expressed glycolytic enzyme) from 0.03 to 4.51 nmol g⁻¹h⁻¹. Strong changes in the proteolytic/glycolytic activity ratio were observed, with a sudden rise in glycolysis during summer, leading to ratio values from about 30 down to 1. Thus, beaches were identified as preferential degradation sites, where very refractory compounds such as cellulose may also be efficiently processed.     

Vegetation dynamics in north-western Mediterranean regions: Instability of the Mediterranean bioclimate

Abstract

Pollen and plant macrofossil records from a selection of sites in Spain, France and Italy are used to explore the origin and the development of the Mediterranean vegetation. The role of evergreen and summergreen taxa is discussed. The expansion of sclerophyllous trees during the Pleistocene interglacials is well correlated with the orbital forcing. During the Holocene, the large number of data illustrates latitudinal and longitudinal differences in vegetation dynamics. Multidisciplinary studies identify short terms climatic fluctuations. The debate is still open between those who attribute an increase of sclerophyllous forests during the late Holocene to a trend toward aridity and those who consider this dynamic as human-induced.     

渤海浮游动物群落生态特点Ⅲ.部分浮游动物数量分布和季节变动

用1959年全国海洋普查中网浮游动物标本,分析渤海水母类,枝角类,糠虾,毛虾和幼虫类的数量分布和季节变化,结果表明,水母类以近岸低盐种为主,主要出现在莱州湾,渤海湾和辽东湾近岸水域,冬季出现的种类较少,优势种为八斑芮氏水母;夏季种类较多,优势种为半球杯水母和嵊山多胃水母等,鸟喙尖头蚤为近岸高温低盐种,主要出现在莱州湾,数量在6月份达到最大值,箭虫是海主要肉食性种类之一,其数量高峰期出现在9月份,长住囊虫的季节变化呈双峰型变化,第1次数量高峰出现在5月份,第2次数量高峰出现在8月份。该种大部分时间主要分布在莱州湾,渤海湾和辽东湾近岸水域,渤海出现的糠虾有长额刺糠虾和漂浮囊糠虾,其中长额否则糠虾受温度的影响较小,在春,夏秋,各有一个数量高峰;漂浮囊糠虾在秋末数量明显增加,这两种糠虾主要分布在渤海湾和辽东湾近岸水域。／三叶针尾涟虫属于低温种类,主要出现在秋季和冬季,细长脚绒属夏季高温种,在6,7月份数量较高,该种的分布受盐度影响比较大,主要出现在受黄海海流影响的谪盐水域,数量较大的幼虫有桡足类的六肢幼体,多毛类海稚虫科的幼体,以壳类幼体和腹足类幼体,其中桡足类六肢幼体和海稚虫科的幼体在5月份出现较多,腹足类幼体在6．7月份数量较高,双壳类幼体在8月份数量较高。     

First record of Cephalopholis taeniops (Valenciennes) in the Mediterranean Sea

Two specimens of African hind Cephalopholis taeniops (Valenciennes, 1828) are recorded for the first time in the Mediterranean Sea, in the coastal area of Gulf of Syrte, Libya. This finding represents an additional case of a tropical species of fish of West African origin in the Mediterranean Sea.     

南黄海、东海鲐鲹鱼索饵场浮游动物生态特征

本文采用比较的方法,研究了黄海南部东海北部和东海中南部两个鲐鲹鱼索饵场浮游动物生态特征。结果表明,南部渔场生物量的极差、变异系数小于北部渔场。若扣除个别站位的影响,则南部渔场的平均值高于北部渔场。北部渔场群落多样度、均匀度、丰富度、单纯度较高,南部渔场则相反。北部渔场浮游动物优势种较少,且大多数种具有较高的聚集强度;而南部渔场优势种较多,优势度低,聚集性差。     

Age estimates derived from hard parts of swordfish Xiphias gladius from the north-western Mediterranean Sea

Accurate age estimates for fish are critical for properly understanding stock dynamics and health; this is particularly true for larger billfishes. Here we determined the most accurate aging estimation methods for swordfish (Xiphias gladius). We compared age estimates obtained from fin-ray sections, otolith sections, whole otoliths, and vertebrae collected from 87 swordfish off the east coast of Corsica. Age estimates from otolith sections were most consistently estimated across different readers (lowest average percentage error), followed by fin-ray sections, third vertebrae, and whole otoliths. When the age estimates from the otolith sections were compared with the other three age sclerochronological methods, we found the average percentage error to be lowest between the otolith section and fin-ray methods. However, age estimates from fin rays proved most useful for estimating swordfish younger than 6 years, as the fin ray-based age diverged from that of the otolith sections as the swordfish aged. Combining fin ray and otolith section techniques, we estimated the growth parameters of 1–12-year-old females (L_∞ = 259.412, k = 0.113, t₀ = −2.499) and 1–7-year-old males (L_∞ = 175.543, k = 0.202, t₀ = −2.239). We found that females grew significantly faster than males after 3 years and remained larger thereafter. Our calculated growth rates for this region of the north-western Mediterranean Sea were lower than those of the Atlantic, Pacific, and eastern Mediterranean Sea swordfish populations, and similar to growth rates recorded for the western Mediterranean Sea populations. Our study provides critical knowledge on biological-related parameters to serve as a guide for preserving the swordfish population in the Mediterranean Sea.     

Contribution of copepods,cladocerans and cirripeds to phosphatase activity in mediterranean zooplankton

The hydrolysis of dissolved phosphoric esters by zooplankton was studied in Toulon seaport (N.W Mediterranean Sea, France). Zooplankton was collected on 90 m filters. The enzyme reaction was studied using paranitrophenyl phosphate (p-NPP) dissolved in sea water. The particulate material activity was expressed as V _max (reaction rate when the enzyme is saturated with substrate) using Eadie-Hofstee plots. The activity per L. was high in spring and decreased from summer to winter. Biomass and zooplankton abundance varied also widely during the year. There were significant correlations between activity per L. and the cirriped cyprid abundance. In contrast, during periods when cyprids were absent, positive correlations with copepod and cladoceran abundance were found. Specific activity varied also during the year, with high values in spring and low values in winter. This activity was positively correlated with cyprid abundance, but not with total zooplankton, copepod or cladoceran abundance. These results indicated that copepods and cladocerans contributed to the overall enzyme production, and that cirripeds could be responsible of high specific activities.     

Changes of zooplankton communities in the Gulf of Tigullio (Ligurian Sea, Western Mediterranean) from 1985 to 1995. Influence of hydroclimatic factors

Year-to-year variations in abundance and composition of zooplanktonwere studied in the Ligurian Sea at a station sampled two timesa month between 1985 and 1995. As a break of 2 years (April1989–December 1990) occurred in the time series, the STATISmethod was chosen instead of time series analysis. Each of thenine sampled years was a single table of monthly or seasonalaverage densities of 26 plankton taxa. STATIS allowed (i) estimationof similarity between each yearly table, (ii) visualizationof the trajectories of both species and observations (seasons)from one year to another, and (iii) associations of particularspecies, which showed similar temporal variations, to be determined.A strong seasonal variation was evident for most species, andyears 1987, 1992 and 1994 were different from the others. Trajectoriesindicated which species were stable and which were characterizedby small or large fluctuations during the nine years. Five differenttaxa associations were detected. For each association, the mostrepresentative period was identified, where each period wasa group of months obtained by clustering on species abundances.Taking into account hydro-climatic factors in the representativeperiods, a contingency discriminant analysis allowed us to identifyand characterize the most discriminant environmental parametersassociated with each group of species. Environmental factorsthat best discriminated the different representative periodswere atmospheric pressure, current speed and direction, andwater temperature.     

Reproduction of macrourids in the upper slope of the north-western Ionian Sea

Aspects of reproduction of macrourid fish in the north-western Ionian Sea are reported. Data were collected during 12 trawl surveys carried out between 1993 and 1995. Mature and running ripe females of Coelorhynchus coelorhynchus, Hymenocephalus italiens and Nezumia sclerorhynchus were found all year round. Mature females of Trachyrhynchus trachyrhynchus were found mainly in August.     

流溪河水库湖泊区浮游动物大小分布特征

于2001年4月至2002年12月调查了流溪河水库湖泊区浮游动物大小分布特征。轮虫在粒径大小范围为50～160μm内,生物量随着粒径的增大而降低;枝角类(100～512μmESD(等效球体直径))的生物量谱呈‘单峰型’,最大生物量出现在中等大小的粒径组(200～256μm)。桡足类的生物量大约占浮游动物生物量的60%,为水库浮游动物最重要的组成部分;粒径分布范围较宽,覆盖了轮虫和枝角类。总体而言,水库湖泊区浮游动物的生物量谱是一个线性谱,浮游动物生物量随着等效球体粒径的增大而上升,表明在食物链能量流动过程中,大个体比小个体消耗了更多的能量。     

Vertical distributions of zooplankton across the Almeria-Oran frontal zone (Mediterranean Sea)

The vertical distribution of zooplankton in the upper 700 mof the water column was investigated across the Almeria–Oranfront (Alboran Sea) during winter 1997/98 (Almofront 2 cruise).Eight sites corresponding to three hydrodynamic structures (theAtlantic jet, an anticyclonic gyre and the surrounding Mediterraneanwaters) were explored, by day and at night, using multiple-netsampling. Results are presented for the major species of copepods(>500 µm), macroplankton and microplankton. Speciesinhabiting the surface layer or occupying it at night extendeddeeper in the gyre. On the other hand, mesopelagic species (e.g.Pleuromamma borealis, Pleuromamma abdominalis, Euphausia krohniand Cyclothone braueri) were found to live deeper, at leastby day for the migrants, in the Mediterranean waters comparedwith the two other structures. These changes in preferentialdepths across the front are discussed in relation to environmentalfeatures, such as light level, abundance of food and mixed layerdepth. This study also documented the vertical distributionof some overwintering copepod species (Calanus helgolandicus,Eucalanus hyalinus and Eucalanus monachus).