Distribution of total dissolved and C18 extractable copper and nickel in relation to dissolved organic matter sources, in the Thermaikos Gulf (eastern Mediterranean)

Organically complexed and total dissolved copper and nickel were measured in the Thermaikos Gulf waters during winter 1998. Total concentrations ranged from 1.13 nmol/L to 7.02 nmol/L for copper and from 3.04 nmol/L to 9.50 nmol/L for nickel. The C18 Sep-Pak solid phase extraction technique was used in order to determine the amount of copper and nickel complexed with the hydrophobic component of the dissolved organic matter (DOM). Up to 32.4% of total copper and 4.57% of total nickel were complexed with the DOM extracted by C18. By applying HPLC analysis it was shown that the majority of the organic compounds retained by C18 had intermediate to low polarity. Using the absorbance ratio a₂₅₄/a₄₃₆ it was possible to unravel that humic substances of both terrestrial and marine origin were present in the Thermaikos Gulf and their distribution followed the dilution of riverine waters. Moreover our results indicated that organic binding of both Cu and Ni was stronger with the hydrophobic compounds of terrestrial origin than with those of marine origin.     

Distribution of plankton lipids and their role in the biological transformation of Antarctic primary production

Production and transfer of lipid through the Antarctic food web is reviewed for the Indian Ocean sector. The slow settling fine particles showed a marked inter-annual variability in biochemical composition with an increase in lipid content as % organic carbon. Comparison of the fatty acid spectra of different size categories of organic particles indicated that fine particles are dominated by saturated, monoenoic and branched acids, while larger material (50–100 μm, 200–500 μm net collected fractions) displayed a signature dominated by polyunsaturated acids. Zooplankton taxa displayed different strategies of lipid accumulation. Lipid content was highest in Thysanoessa macrura females and copepodite stages of Calanus propinquus. Relatively low levels were recorded for juveniles and male stages of euphausiids. Reserve lipids varied with species: C. propinquus showed equal content of triglycerides and wax esters, T. macrura showed a dominance of wax esters and Euphausia superba and Themisto gaudichaudii accumulated only triglycerides. Computed as carbon equivalent and integrated over 200 m, lipids in slow settling particles represented 22.6% of annual primary production. Similar computation with mesozooplankton and E. superba data on biomass and population structure from several summer cruises indicated values of carbon accumulation as lipid reserves and egg production of 4.2 and 0.1% of annual primary production for copepods and 4.4 and 3.8% for E. superba. When all trophic levels are considered, the overall mean exceeded 30% of annual primary production.     

Inter-comparing five forecast operational systems in the North Atlantic and Mediterranean basins: The MERSEA-strand1 methodology

The methodology to achieve a real time inter-comparison of five state-of-the-art operational forecast systems for the North Atlantic and Mediterranean basins is presented. All systems provide analysis and near real-time prediction of the three-dimensional ocean through Opendap servers. A standard set of diagnostics called metrics, is described. Definition and examples of metrics are given. An inter-comparison of the five systems is conducted over a 1 year period using those metrics. It is shown that the methodology developed allows a successful inter-comparison. It has been adopted by the GODAE community. It is also shown that the systems are consistent with the current knowledge of the ocean circulation and climatologies. Systems are deficient in the representation of specific water masses characteristics as Mode waters. Data assimilation of vertical profiles of temperature and salinity solve such deficiencies. Metrics also allow a monitoring of the system's North Atlantic overturning stream function and will allow detecting any changes in the coming year system's thermohaline circulation.     

Dynamics of suprabenthos-zooplankton communities around the Balearic Islands (western Mediterranean): Influence of environmental variables and effects on the biological cycle of Aristeus antennatus

Dynamics of suprabenthos and zooplankton were analyzed in two areas located in the NW (off Sóller harbour) and S (off Cabrera Archipelago) of Mallorca (Balearic Islands, western Mediterranean) at depths ranging between 135–780 m. Four stations situated respectively at 150 m (shelf-slope break), and at bathyal depths of 350, 650 and 750 m were sampled at bi-monthly intervals during six cruises performed between August 2003 and June 2004. Suprabenthos showed maximum biomass in both areas from late spring to summer (April to August), while minimum biomass was found in autumn (September–November). Though variable, temporal dynamics of zooplankton showed peaks of biomass in late winter and summer (February and June), while minimals occurred in autumn (August–September) and, at bathyal depths, in April. Suprabenthos (abundance; MDS analyses) showed a sample aggregation as a function of depth (3 groups corresponding to the shelf-slope break, upper slope — over 350 m; and the middle, deeper part of the slope — over 650–750 m), without any separation of hauls by season. By contrast, zooplankton samples were separated by season and not by depth. There was evidence of three seasonal groups corresponding to summer (June 2004–August 2003), autumn–winter (September and November 2003, February 2004), and spring (April 2004), being especially well established off Sóller. In general, suprabenthos was significantly correlated with the sediment variables (e.g. total organic matter content (% OM), potential REDOX), whereas zooplankton was almost exclusively dependent on Chl a at the surface, which suggests two different food sources for suprabenthos and zooplankton. The increase of suprabenthos abundance in April–June was paralleled by a sharp increase (ca. 2.8 times) in the %OM on sediment during the same period, coupled ca. 1–2 months of delay with the peak of surface Chl a recorded in February–March (from satellite imagery data). Suprabenthos biomass was also correlated with salinity close to the bottom, suggesting a link between suprabenthos abundance and changes in the oceanographic condition of water masses close to the bottom. It is suggested that a higher suprabenthos biomass recorded off Sóller in comparison to that off Cabrera in June could, in turn, be related to a seasonal inflow of Levantine Intermediate Water (LIW) in April–June in this area at mid bathyal depths (350–650 m). This trend would be based on: 1) it was evident only at mid-slope depths between 350–750 m, coinciding with the LIW distribution, and 2) it was not recorded among zooplankton (collected throughout the water column). The possible effect of the fluctuations of suprabenthos and zooplankton on higher trophic levels has been explored studying the diet and food consumption rates of the red shrimp Aristeus antennatus, as indicator species by its dominance in bathyal communities. A. antennatus increased its food consumption from February to April–June 2004 off Sóller, which in the case of large (CL > 40 mm) specimens was found in both areas. In addition, there was a shift of diet from winter to spring–early summer. In this last period, A. antennatus preyed upon euphausiids and mesopelagic decapods and fish, while benthos (e.g. polychaetes and bivalves) decreased in the diet. This indicates an increase in the food consumption and probably in the caloric content of the diet in pre-spawning females in April–June 2004, which is synchronized with the period when gonad development begins in A. antennatus females (May–June). Anyway, macrozooplankton, and not suprabenthos, is crucial as a high energetic food source in the coupling between food intake and reproduction in the red shrimp.     

The influence of different turbulence schemes on modelling primary production in a 1D coupled physical–biological model

A one-dimensional (1D) coupled physical–microbiological model has been applied to a site in the central North Sea. The impact of the choice of the turbulence closure scheme on the modelling the primary production has been investigated.The model was run with four different parameterisations of vertical mixing of heat, momentum and dissolved and suspended matters, using M2 tidal forcing and the hourly mean meteorological forcing of 1989 to reproduce the annual thermal structure and primary production. The four mixing parameterisations are: Level 2 turbulence closure scheme [Mellor, G.L., Yamada, T., 1974. A hierarchy of turbulence closure models for planetary boundary layers. J. Atmos. Sci. 31, 1791–1806; Mellor, G.L., Yamada, T., 1982. Development of a turbulence closure model for geophysical Fluid problems. Rev. Geophys. Space Phys. 20 (4) 851–875] using an explicit numerical scheme [Sharples, J., Tett, P., 1994. Modelling the effect of physical variability on the midwater chlorophyll maximum. J. Mar. Res. 52, 219–238]; a version of the Level 2.5 turbulence closure scheme [Galperin, B., Kantha, L.H., Hassid, S., Rosati, A., 1988. A quasi-equilibrium turbulent energy model for geophysical flows. J. Atmos. Sci. 45, 55–62; Ruddick, K.G., Deleersnijder, E., Luyten, P.J., Ozer, J., 1995. Haline stratification in the rhine/meuse freshwater plume: a 3D model sensitivity analysis. Cont. Shelf Res. 15 (13) 1597–1630] simplified to use an algebraic mixing length by Sharples and Simpson [Sharples, J., Simpson, J.H., 1995. Semidiurnal and longer period stability cycles in the Liverpool Bay region of freshwater influence. Cont. Shelf Res. 15, 295–313], also solved explicitly; the same simplified L2.5 scheme with an implicit numerical solution and modified vertical discretisation scheme [Annan, J.D., 1999. Numerical methods for the solution of the turbulence energy equations in the shelf seas. Int. J. Numer. Methods Fluids 29, 193–206]; and another version of the same scheme (but using a different algebraic mixing length) as described by Xing and Davies [Xing, J., Davies, A.M., 1996a. Application of turbulence energy models to the computation of tidal currents and mixing intensities in the shelf edge regions. J. Phys. Oceanogr. 26, 417–447; Xing, J., Davies, A.M., 1996b. Application of a range of turbulence models to the computation of tidal currents and mixing intensities in shelf edge regions. Cont. Shelf. Res. 16, 517–547; Xing, J., Davies, A.M., 1998. Application of a range of turbulence energy models to the computation of the internal tide. Int. J. Numer. Methods Fluids 26, 1055–1084]. Various model outputs at the sea surface and in depth profiles have been compared with data collected in 1989 as part of the North Sea Project [Huthnance, J.M., 1990. Progress on North Sea Project. NERC News, vol. 12, pp. 25–29, UK]. It is shown that the biological results are extremely sensitive to the small changes in the physical conditions, which arise due to the different turbulence schemes tested. The timing of the spring bloom and the maintenance of the midwater chlorophyll maximum all differ greatly between model runs, and the gross primary production varies by a factor of two from the highest to lowest results. The simplified Level 2.5 scheme, implemented using the numerical methods of Annan [Annan, J.D., 1999. Numerical methods for the solution of the turbulence energy equations in the shelf seas. Int. J. Numer. Methods Fluids 29, 193–206], produces results, which give the best agreement with the available data.     

Spatio-temporal variations in deep-sea demersal communities off the Balearic Islands (western Mediterranean)

The spatial and temporal variations of deep-sea megafaunal assemblages from the western Mediterranean are analysed in the present paper. The assemblages from two locations of the Balearic Islands situated 120 km apart were compared using data collected seasonally on a bathymetric stratum covering the 150–750 m depth range during six bottom-trawl surveys. The assemblage structure, in terms of species composition, species dominance and population sizes, was differentially affected by the spatio-temporal variables analysed (depth, location and fishing period). Although depth was the main factor determining the assemblage composition, the differences obtained between the two locations were also relevant. On the upper slope these between-location differences in the dynamics of megafaunal assemblages were found to be related to the effect of fishing exploitation. Population size-based metrics and biomass spectra were good predictors of meso-scale fishing effects, and were mainly reflected by elasmobranchs and demersal teleosts. Nevertheless, the effects of fishing depended on the species considered. Two dominant large-sized fish species found on the upper slope in both localities, Galeus melastomus and Phycis blennoides, had higher biomass values associated with lower fishing effort. Although the mean body weight (MBW) of both species and also the mean maximum body weight (MMBW) of G. melastomus agreed with this pattern, the P. blennoides MMBW did not. This last case could be indicative of natural size-trends such as the bigger–deeper phenomenon which refers to the displacement of large individuals towards the deeper limit of their bathymetric distribution, beyond the maximum depth sampled in this study for this species. By contrast, the target species of the upper slope fishery, the red shrimp Aristeus antennatus, was not negatively affected by the direct impact of fishing activity and other environmental factors, such as the presence of specific water masses could also be important.     

Seasonal and short spatial patterns in European hake (Merluccius merluccius L.) recruitment process at the Balearic Islands (western Mediterranean): The role of environment on distribution and condition

This study evaluates the link between the recruitment process of European hake (Merluccius merluccius L.) of the Balearic Islands (western Mediterranean) and the environmental and physiological conditions. Spatio-temporal variation of abundance and condition of fish were evaluated at two locations each with different oceanographic conditions, one in the north (Sóller, SO) and another in the south (Cabrera, CA) of Mallorca Island. Environmental variables explored were hydrography, sediment characteristics, phytoplankton pigment concentration (ppc) and the trophic resources of hake. Individuals were divided in three life stages: recruits, post-recruits and young adults. Hepatosomatic index (HSI), relative condition index (K_n), gonadosomatic index (GSI) and fullness index (FI) were analysed for the three life stages. Recruitment starts in February with the incorporation of smaller hakes, and it can be followed through spring and early summer with a peak in April. However, some spatial heterogeneity in the recruitment process has been found between north and south of the Island. The main pulse of recruitment occurred at a different time in the two areas. Spatial heterogeneity was also consistent with the condition of hake recruits, with higher values of K_n and HSI at SO than at CA. Maximum values of K_n were found in February at SO and in April at CA, coinciding with the start of the different recruitment pulses to the fishing grounds. Post-recruits and young adults also showed higher condition at SO than at CA. The arrival in spring of the Western Winter Intermediate Waters (WIW) drives the spatial-temporal variation in abundance and condition of hake. Ppc was highly correlated with recruit abundance with a time lag of two months, while for post-recruits the time lag was three months. The observed differences in the condition of hake between areas could be a consequence of the fact that the waters to the north of Mallorca are comparatively more under the seasonal influence of WIW which is formed in more productive areas. Thus, this study characterises the short temporal and spatial variability in the hake recruitment process off the Balearic Islands, both in terms of abundance and fish condition. This pattern is explained on the basis of the mesoscale environmental variability observed between north and south of Mallorca and the ecological adaptive strategy of recruiting in the optimal environmental season.     

Evidence of episodic changes in deep-sea mesozooplankton abundance and composition in the Levantine Sea (Eastern Mediterranean)

Mesozooplankton samples from the 4270-m deep Ierapetra Basin in the oligotrophic Levantine Sea have revealed a strong temporal variability in abundance and composition hitherto unknown for the deep sea pelagic zone. The phenomenon reflected by a survey in June 1993 as compared to January 1987 is assessed by (i) the increase of the mesozooplankton standing crop throughout the water column, (ii) the absence of a decline in mesozooplankton abundance with increasing depth below 1000 m, (iii) the outstanding dominance of two interzonal calanoid copepods at bathypelagic and abyssopelagic depths and (iv) a substantial faunal change due to the codominance of Calanus helgolandicus, which was found for the first time in the area. The underlying hydrographical factors are addressed in the light of the Eastern Mediterranean Transient (EMT). Apart from a possible long-term faunal change, the EMT may exaggerate episodic plankton blooms and surface-abyssopelagic coupling in space and time.     

Hydrographic conditions affecting two fishing grounds of Mallorca island (Western Mediterranean): during the IDEA Project (2003–2004)

This paper describes the hydrographic conditions observed during six surveys carried out during 2003 and 2004, in the framework of the “IDEA Project” (acronym for “Influence of oceanographic structure and dynamics on demersal populations in waters of the Balearic Islands”). The surveys were developed on the shelf and slope of Mallorca Island, in particular in two fishing grounds at the north and south of the Mallorca channel. Periodic movements of the fishing fleet between these two areas have been regularly reported, suggesting a seasonal variability of the resources which could be in turn associated with the hydrodynamic variability. With this motivation, water masses affecting these grounds have been identified and their seasonal variability has been studied. Different oceanographic and environmental conditions have been found between the two fishing grounds. These differences are related to the presence of mesoscale structures, associated with the Western Mediterranean Intermediate Water (WIW) at the north of the Ibiza channel and big gyres detached from the Algerian Current. The former has been shown to have influence on the regional oceanic circulation and the latter could affect the progress of fresh Atlantic Water (AW) towards the channels and make possible the presence of high salinity values at intermediate waters at the south of Mallorca Island. Historical data from other oceanographic cruises carried out in the region are finally used to discuss the interannual variability of these mesoscale structures.     

Population dynamics of the red shrimp Aristeus antennatus in the Balearic Islands (western Mediterranean): Short spatio-temporal differences and influence of environmental factors

The red shrimp Aristeus antennatus is one of the target species of the bottom trawl fishery of the Balearic Islands. The objective of the present paper is to study the short spatial and temporal differences of this important economic resource between two different locations off Mallorca (Cabrera: CA; Sóller: SO), where a fleet mobility pattern has been detected, and to study the influence of environmental conditions on this species. Six simultaneous bottom-trawl and oceanographic surveys were carried out at these two locations in order to collect data from the demersal species, hydrography (temperature and salinity), trophic resources and sediment characteristics. The commercial fleet from both locations was monitored by monthly on-board sampling, log-books and daily landings obtained from sales slips. Additional data was obtained from other fishing surveys. Short spatial and temporal differences have been detected between both locations. The population at CA was more demographically homogeneous, while that at SO showed important variations, like high abundance of juveniles recruiting to fishing grounds in autumn–winter and high abundance of large females during summer. Several differences have also been found in the biology of the species between locations, such as males were more abundant in SO than in CA. Also, the reproductive period started sooner in SO than in CA, and the condition of pre-spawning females was better in SO. The percentage of total lipids in the hepatopancreas was minimal during the spawning period, showing their importance as a reserve of energy for the ovary ripening. Water masses could play an important role in these differences, the characteristics of water masses being more stable in CA than in SO. Red shrimp adult females seemed to be more correlated with the warmer and more saline Levantine Intermediate Waters, while juveniles (males and females) and adult males were more correlated with the colder Western Mediterranean Deep Waters, detected only in SO during autumn–winter. Two different hypothesis of mobility patterns for the species are discussed in relation to these observed differences.     

Seasonal variability of fractionated phytoplankton, biomass and primary production in the Straits of Magellan

The results on the distribution of phytoplankton biomass (expressed as Chla) and primary production (¹⁴C assimilation), during three oceanographic cruises carried out during Austral spring and at the end of the summer and the autumn in the Straits of Magellan, suggest a strong variability of trophic levels for this ecosystem.Seasonal evolution of the biomass concentration goes from the spring maximum of 2.33 μg/l through a sharp decrease, 0.49 μg/l, observed at the end of summer, until the minimum of 0.24 μg/l measured during the autumn.The trophic conditions are dependent on hydrographic, meteo-climatic and geo-morphological characteristics: at the Atlantic entrance and between the two Angosturas the strong mixing of water column limit the development of phytoplankton; at the Western opening and along the Pacific arm the complex exchange mechanisms with the ocean, the glacio-fluvial contribution and the presence of a thermohaline front near the Isla Carlos III influence both biomass and primary production distributions. The maximum values are reached in the Central Zone (Paso Ancho) characterized by high stability of the water column.Primary production ranged from a minimum of 12.3 to a maximum of 125.9 mgC m⁻² h⁻¹. The overall trend seems to be a progressive and simultaneous increase from the Pacific and Atlantic openings to the Central Zone of Paso Ancho where the maximum value was reached. In general, biomass and primary production distributions correspond quite well except for the area of Isla Carlos III where biological and chemico-physical causes tend to limit ¹⁴C assimilation.Contribution of pico-phytoplankton (< 2 μm) to total biomass appears to be time dependent: in the blooms observed during spring a very modest incidence (< 6%) was observed whereas became more (> 50%) during the summer-autumn seasons when total biomass was decreasing.Within the Straits, at the end of summer, the contribution of pico-phytoplankton primary production is 59%, whereas nano and microplankton contribute 39% and 2%, respectively. At the oceanic external stations the photosynthetic activity of the bigger size-fraction (> 2 μm) is predominant (> 50%).These findings support the hypothesis that the pico-phytoplankton ( < 2 μm) is substantially constant, whereas temporal variations are due to the larger (> 10 μm) cells only.     

仿真在造船企业管子生产物流系统中的应用

以某造船企业管子分厂产能评估为应用背景,针对生产过程为多班制、多工艺、多工序、混合作业的复杂生产方式,将生产物流仿真系统分为输入层、仿真层、输出层三个层次,采用面向对象的仿真技术,把管子生产物流中的各种要素分为不同的类,构建了管子生产物流系统的仿真模型.并对管子分厂生产能力在不同工况条件下,在不同生产调度策略下分别进行了评估.通过仿真评估帮助决策者制定出最佳的决策,提高生产能力.     

The influence of oceanographic scenarios on the population dynamics of demersal resources in the western Mediterranean: Hypothesis for hake and red shrimp off Balearic Islands

The aim of the present paper is to study the relationships between some climatic indices and parental stock, recruitment and accessibility to trawl fishery of hake (Merluccius merluccius) and red shrimp (Aristeus antennatus) off Balearic Islands (western Mediterranean). Available annual catch per unit effort, recruitment and spawning stock biomass have been used as biological data. As environmental data, the meso-scale IDEA index and the large-scale North Atlantic Oscillation (NAO) and Mediterranean Oscillation (MO) indices have been used. To analyze possible links between these indices with the population dynamics of demersal resources, two non-linear approaches have been applied: (i) stock–recruitment relationships from Ricker and Beverton–Holt models, by sequentially incorporating environment factors; (ii) generalized additive modelling, both classical general and threshold non-additive models were considered. The latter simulate an abrupt change in explicative variables across different phases (time periods or climatic index values). The results have shown that two oceanographic scenarios around the Balearic Islands, associated with macro and meso-scale climate regimes, can influence the population dynamics of hake and red shrimp. This is especially true for recruitment, which seems to be enhanced during low NAO and IDEA indices periods. During these periods, colder-than-normal winters generate high amounts of cold Western Mediterranean Intermediate Waters (WIW) in the Gulf of Lions, which flow southwards and reach the Balearic Islands channels in spring, increasing the productivity in the area. This oceanographic scenario could also be favourable to the distribution of hake on the fishing grounds where the trawl fleet targets this species, increasing its accessibility to the fishery. Both spawning stock and abundance of red shrimp seems to be also enhanced by high MO index periods, which could reflect the increased presence of the saline and warm Levantine Intermediate Waters (LIW) in the study area, extending over the fishing grounds of this species. The proposed interactions can be useful to assess and manage these important demersal resources.     

Spatial and temporal variability of size-fractionated biomass and primary production in the Ross Sea (Antarctica) during austral spring and summer

The results of a study on the spatial and temporal dynamics of size-fractionated biomass and production of phytoplankton in the Ross Sea during the austral spring and summer are reported. The spring cruise took place in the offshore Ross Sea from 14 November to 14 December 1994. Sampling was carried out on a transect of 27 stations distributed from 76.5 to 72.0°S along 175°E, and covered the three main Antarctic environments of the polynya open waters, the marginal ice zone and the pack ice area. Three subsystems were identified. The subsystem of the polynya was characterised by the predominance of the micro- and nano-planktonic fractions, chlorophyll (Chl a) concentrations from 69.6 to 164.7 mg m⁻² and production rates from 0.68 to 1.14 g C m⁻² day⁻¹. The second subsystem, the marginal ice zone, showed a relative increase of the micro-planktonic fraction, high biomass levels (from 99.64 to 220 mg Chl m⁻²) and production rates from 0.99 to 2.7 g C m⁻² day⁻¹. The subsystem of the pack ice area had a phytoplankton community dominated by the pico-planktonic fraction and showed low biomasses (from 19.4 to 37.7 mg Chl m⁻²) and production rates (0.28 to 0.60 g C m⁻² day⁻¹). Selective grazing by krill is considered an important factor in determining the size structure of the phytoplankton communities. The summer study consisted of a time series carried out in inshore waters of Terra Nova Bay from 12 January to 8 February 1990. In a well stabilised water column and with high levels of PAR always available, the primary production rates of a community dominated by micro-plankton varied from 0.52 to 1.2 g C m⁻² day⁻¹ (average 0.84). A high P/B ratio, up to 3, and a remarkably elevated mean phaeopigment (Phaeo)/Chl a ratio of 2.4 indicated an active removal of biomass by grazing, confirmed by the presence of faecal pellets in quantities reaching 6000 m⁻³ in the upper 50 m. The peculiarities of the inshore versus offshore environments in terms of community size structure, production processes and their implications as regards the food web are discussed.     

The effect of precession-induced changes in the Mediterranean freshwater budget on circulation at shallow and intermediate depth

The Neogene marine sedimentary record of the Mediterranean basin is characterised by the regular occurrence of organic-rich layers or sapropels. These sapropels are known to correlate with the precession cycle: their deposition coincides with precession minima. This correlation is thought to be caused to a large extent by a precession-induced increase in the amount of freshwater reaching the Mediterranean Sea. In the literature, various sources of this extra freshwater have been identified and different mechanisms as to how this freshwater flux leads to sapropels have been proposed. In this study we investigate the effects of precession-induced changes in the freshwater budget using a regional ocean general circulation model of the Mediterranean Sea. Emphasis is on the effects at the surface and at intermediate depth. The forcing of the ocean model is adjusted to precession minimum conditions on a parameter by parameter basis. Novel to our approach is that the value of the required adjustments is taken from a global coupled climate model with which experiments have been performed for the present day (close to precession maximum) and precession minimum. With the ocean model we focus on the extent to which extra runoff from either south (specifically: the river Nile) or north and changes in net precipitation over the sea itself lead to a more stable stratification; this we judge by the associated reduction of the sea surface salinity and mixed layer depth in the regions of intermediate and deep water formation. Our main finding is that the effects of (1) increased discharge of the rivers coming from the north, and (2) the increase in net precipitation over the sea itself, are of equal or greater importance than that of increase in Nile discharge.     

Vertical profiles of particulate organic matter and its relationship with chlorophyll-a in the upper layer of the NE Mediterranean Sea

Particulate organic matter (POM), nutrients, chlorophyll-a (CHL) and primary production measurements were performed in the upper layer of three different regions (cyclonic, anticyclonic and frontal+peripherial) of the NE Mediterranean Sea in 1991–1994. Depth profiles of bulk POM exhibited a subsurface maximum, coinciding with the deep chlorophyll maximum (DCM) established near the base of the euphotic zone of the Rhodes cyclone and its periphery, where the nutricline was situated just below the euphotic zone for most of the year. Moreover, the POM peaks were broader and situated at shallower depths in late winter–early spring as compared to its position in the summer–autumn period. Under prolonged winter conditions, as experienced in March 1992, the characteristic POM feature disappeared in the center of the Rhodes cyclone, where the upper layer was entirely occupied by nutrient-rich Levantine deep water. Deep convective processes in the cyclonic gyre led to the formation of vertically uniform POM profiles with low concentrations of particulate organic carbon (POC) (2.1 μM), nitrogen (0.21 μM), total particulate phosphorus (PP) (0.02 μM) and chlorophyll-a (0.5 μg/L) in the euphotic zone. Though the Levantine deep waters ascended up to the surface layer with the nitrate/phosphate molar ratios (28–29) in March 1992, the N/P molar ratio of bulk POM in the upper layer was low as 10–12, indicating luxury consumption of phosphate during algal production. Depth-integrated primary production in the euphotic zone ranged from 38.5 for oligotrophic autumn to 457 mg C m⁻² day⁻¹ for moderately mesotrophic cool winter conditions.     

Public Stakeholders' Perception of ICZM and Coastal Erosion in the Mediterranean

The Mediterranean area plays a pivotal role within the definition and implementation of regional strategies for integrated coastal zone management (ICZM). Under the umbrella of the Regional Framework Operation BeachMed-e, a research project was carried out in five Mediterranean EU regions (East Macedonia and Thrace in Greece, Lazio, Liguria, and Emilia Romagna in Italy and Languedoc-Roussillon in France), in order to study the different approaches to ICZM that have been applied and also to test new approaches to these regions. The aim of this article is to present and discuss the results of the common surveys conducted in order to investigate the institutional stakeholders’ perception on ICZM in the five Mediterranean regions considered. The results are presented region by region, while comparisons are carried out among regions. Summarizing the results it can be stated that some differences and common problems affecting the coastal decision-makers of the five Mediterranean regions considered were identified. Particularly, stakeholders involved in coastal management generally perceived a lack of collaboration and a poor information exchange in all the regions, resulting sometimes in a lack of awareness on coastal erosion issues.     

Coastal Crisis: The Failure of Coastal Management in the Spanish Mediterranean Region

It is a fact that coastal zones in the Mediterranean are becoming progressively more seriously degraded. Instrumental to the phenomenon in Spain is the evident failure of the coastal management that the institutions have pursued for over three decades, both under the old, state-centralized model, and the new organizational model with the political division of land into autonomous regions. This failure can in part be explained not only by the inadequate tools the administration possesses to address the dynamism and complexity of the new economic activities that have sprung up along the coast, but also by incoherent sectoral policies. Finally, there has been no all-encompassing political strategy capable of dealing with coastal communities' demands for development and the need for the protection of ecosystems and their natural resources. All this has resulted not only in a deterioration of the area, but also in the discrediting of actions implemented by the institutions, and their plans and programs being perceived as an obstacle to economic development.     

Seasonal and inter-annual variations in the surface freshwater flux in the Mediterranean Sea from the ECMWF re-analysis project

Seasonal and inter-annual variations in surface freshwater fluxes in the Mediterranean Sea are examined. Evaporation and precipitation rates are estimated from ERA15, the re-analysis project carried out at the European Center for Medium-Range Weather Forecasts (ECMWF) for the period 1979–1993. A seasonal cycle of river runoff is computed from a recent historical data set. The climatological mean for precipitation (326 mm/yr) is comparable to previous estimates, whereas that for evaporation (920 mm/yr) is low compared to other independent estimates, but regions of high and low evaporation rates are correctly located. The budget reveals an annual mean freshwater deficit in the Mediterranean of 480 mm/yr, lower than previous estimates because of the lower evaporation rate estimated by ECMWF. Consequently, the flows through the straits of Gibraltar and Sicily, deduced from the freshwater budget, are found to be slightly low.Seasonal and inter-annual variabilities of ERA15 precipitation are consistent with those deduced from independent precipitation estimates obtained with SSM/I observations for the 1988–1993 period. ECMWF and satellite estimates both agree on the amplitude of the seasonal cycle. The seasonal cycle of the river runoff has a globally small contribution to the freshwater budget, but is significant in summer when the precipitation is nearly null. The variability of the freshwater flux for the Mediterranean as a whole shows a strong seasonal cycle (amplitude of 50 mm/month), which seems to be mainly controlled by evaporation. The inter-annual variability of the freshwater flux, however, appears to be governed mainly by precipitation. Its amplitude, which is of the order of 50 mm/yr on average but may reach nearly 150 mm/yr for a particular year, is considered to be large but nevertheless not sufficient to explain differences observed in the estimates of the climatological mean freshwater flux proposed by various authors. The freshwater deficit in the Mediterranean Sea has globally increased by nearly 50 mm, mainly because of a decrease in precipitation over this 15-yr period.     

Isotopic composition of carbon and nitrogen of suprabenthic fauna in the NW Balearic Islands (western Mediterranean)

Stable isotope (δ¹³C and δ¹⁵N) analyses were performed on suprabenthic fauna collected in the western Mediterranean (NW Balearic Islands), at depths ranging between 350 and 780 m. Samples were collected seasonally at bi-monthly intervals during six cruises performed between August 2003 and June 2004, using a Macer-GIROQ suprabenthic sledge (0.5 mm mesh size). Twenty-four separate species (5 mysids, 12 amphipods, 2 cumaceans, 2 isopods, 1 euphausiid, 1 decapod and 1 fish) and bulk copepods were analyzed on a seasonal basis for stable carbon and nitrogen isotopes. Stable nitrogen isotope ratios (δ¹⁵N) ranged from 2.3‰ (the amphipod Lepechinella manco in September 2003) to 13.0‰ (the amphipod Rhachotropis caeca in August 2003). δ¹³C values ranged from − 24.2 (the cumacean Campylaspis sulcata in June 2004) to − 16.1 (the amphipod Bruzelia typica in November 2006). Both δ¹³C and δ¹⁵N values suggest that there are three trophic levels within the suprabenthic community. However, considering the bathymetric range of the species, the results suggest that the deepest assemblage supported only two trophic levels. The stable isotope ratios of suprabenthic fauna displayed a continuum of values and confirmed a wide spectrum of feeding types (from filter-feeders to predators). In general, and in spite of the poor knowledge about diets available for most suprabenthic species, higher δ¹⁵N were found for carnivorous amphipods (e.g. Rhachotropis spp., Nicippe tumida) consuming copepods. Low overlap for δ¹³C and δ¹⁵N values was observed, though δ¹⁵N values where less variable than δ¹³C, which suggests high resource partitioning in this assemblage. Seasonal variations in isotopic composition for both δ¹³C and δ¹⁵N were low (less than 1‰ and 3‰, respectively) and variable depending on species. Low correlations between δ¹³C and δ¹⁵N of suprabenthic fauna were found for all periods studied, though increasing from February 2004 to June 2004 (after the main peak of primary production in surface). C:N ratio (indicator of lipid content) showed higher values in summer than in winter. This suggests that lipid content may explain the seasonal patterns of δ¹³C variability and, due to the increase of storage products in phytoplankton and zooplankton, it possibly indicates the peak of primary production at the surface.