Adriatic Ionian Research Articles

Tourist itineraries for Sustainable Mobility: an application in the Salento Area (Italy)

The purpose of this work is to define the design process, implemented through an analytical methodology, of two sustainable mobility tourist routes in a specific area of southern Italy (Salento); methodology applicable to other territorial realities. This design process was developed in the context of the 2014/2020 Interreg V-A Greece-Italy cross-border cooperation strategic project called "AI SMART_Adriatic Ionian Small Port Network". It takes into account the analysis of existing Plans and Programs at different levels (Sustainable Mobility Urban Plans; cycling routes; Territorial Plans, etc.), the analysis of statistical data in the area related to employment and tourism; the interlocution with key stakeholders, the analysis of architectural, landscape and food and wine surpluses. These routes have been defined for the interaction of the port of Otranto with the hinterland territories and with the opposite Ionian coast to promote the sustainable and inclusive transnational tourist fruition of the Apulian territory. The genesis of the two thematic itineraries stems from the need/willingness to valorise some areas of Salento through the connection of significant nodes in terms of landscape, architectural and historical value, which define two routes with Pulsano and Otranto as their vertices. The project brings together the potential of the Salento as an area with a strong tourist value, with the theme of sustainable mobility, suggesting the seasonality of travel of each, to meet the needs of deseasonalization of an area with a high summer and seaside tourism vocation.

Intermodal Passenger Transport after COVID-19 Pandemic Breakout

The current paper is based on data collected within the framework of the Inter-Connect PLUS project, with a focus on incorporating new norms before, during, and after the COVID-19 pandemic. A questionnaire was conducted in four countries of the Adriatic-Ionian (ADRION) Region: Italy, Slovenia, Croatia, and Albania. The collected data from the survey was analyzed to draw conclusions about the travel modes citizens used before, during, and are willing to use after the pandemic. The paper closes with recommendations, in the form of a Roadmap, highlighting the potential positive impact of the pandemic on the future of sustainable mobility.

Sport Tourism as Driving Force for Destinations’ Sustainability

Sport tourism is a fast-growing segment of tourism offering new perspectives and supporting travelers’ behavior shift towards active living that is a boost for sustainable destinations. These interrelations between active living, active travelling, and sport tourism have a powerful environmental, economic, and social impact. Based on the recognized contribution of sport tourism in sustaining destinations, the current paper aims to (a) explore the state of sport tourism in the Adriatic–Ionian Region by identifying existing sport tourism initiatives, (b) analyze the current and future potentials of sport tourism in the area’s sustainable growth, and (c) draw policy recommendations for sport tourism development in the region with a view to support the wider vision of sustainability. The review of existing sport tourism cases, revealing an existing investment towards this tourism form, was followed by a qualitative survey of the area’s tourism stakeholders (Greece, Italy, Slovenia, Croatia, Albania, Montenegro, Serbia). Results reveal that sport tourism is estimated to help in building a unique identity closely linked to sustainability goals—the area represents a great natural and cultural beauty that can be emphasized by sport initiatives, while, once such efforts are incorporated in wider sustainability plans, the destinations’ profiles can be significantly upgraded.

A Methodological Framework for Developing a Smart-Tourism Destination in the Southeastern Adriatic–Ionian Area

This paper presents a methodological framework aiming to support the creation of a smart-tourism destination. Specifically, the study is realised in the frame of NEST, a European Union Interreg project aiming to create a smart-tourism destination in the Adriatic–Ionian area. Therefore, the study focuses on the southeastern Adriatic–Ionian area, as a portion of the European macro-region including the Italian regions of Molise and Apulia and the Balkan countries of Albania and Montenegro. This area presents a clear vocation for tourism, with a distinctive cultural heritage, attractive natural landscapes, and old culinary traditions offering a variety of eno-gastronomic and folk craft products. In the frame of the EU neighbour policies and in coherence with the objectives of the EU smart specialization strategy, several initiatives have been promoted for innovating the tourism offering in this area. Despite this, the full achievement of the creation of an Adriatic–Ionian smart destination calls for the adoption of a multidimensional strategy able to leverage knowledge-intensive dynamics of collaboration. This paper, therefore, aims to highlight the opportunities of adoptions and implications of this methodological framework for the cross-border marketing and management of the Adriatic–Ionian smart destination.

First Documented Uses of Caves along the Coast of Albania by Mediterranean Monk Seals (Monachus monachus, Hermann 1779): Ecological and Conservation Inferences.

Simple SummaryPresent and past information on endangered species distribution, biology and ecology is essential to implement conservation measures. The first documented use of habitat by the Mediterranean monk seal along the coasts of Albania is here presented. This was confirmed through the use of infrared camera traps and by the findings of a seals’ scat, proving the use of two caves in the study area. The results of the analysis of the scat revealed the last meal (three fish species) as well as microplastics and other non-food items. The relevance of this research goes beyond national borders, providing essential upgraded information for the species in Albania, and it also represents important data on an Adriatic–Ionian Basin context for the protection and recovery of the species.Information on the habitat use of the Mediterranean monk seal (Monachus monachus) along the coast of Albania (Adriatic and Ionian Sea) has so far been limited to vague and generalised data. A survey conducted in the National Marine Park Karaburun-Sazan in the summer of 2019 identified two marine caves with morphological characteristics best suited for use by such species. The two caves were subsequently equipped with infrared camera traps in 2020. The recovery of a scat in one of the caves during the 2019 survey and the photographic material obtained confirmed the use of the cave. This research provides the first documentation of marine cave habitat use by the Mediterranean monk seal in Albania. Quantitative and qualitative assessment of specimens frequenting the area could not be performed due to the limited data obtained on seal presence along the Albanian coasts. Nevertheless, the retrieved information is relevant for Albania and for the species conservation. The collected scat was analysed for trophic and anthropogenic contamination data. Three species (gilthead sea bream, European sea bass, and garfish), as well as four anthropogenic items (including a piece of nylon net), were identified. The inferences resulting from the analyses of the data presented in this study provided additional information on the ecology of the species and its conservation priorities, which need to be contextualized at the Adriatic–Ionian regional scale.

Relationship between thermohaline and biochemical patterns in the levantine upper and intermediate water masses, Southeastern Mediterranean Sea (2013–2021)

The relationships between the interannual variations of the Levantine intermediate water (LIW) core properties and the corresponding biochemical variations in the euphotic zone were systematically studied in the Southeastern Mediterranean during 2013–2021 and since 2002 based on a previous study. Salinity and temperature interannual fluctuations in the LIW continue to follow the Adriatic–Ionian Bimodal Oscillating System (BiOS) mechanism, with salinity and temperature peaks in the years 2008–2010, 2014–2015, and 2018–2019 coinciding with periods of anticyclonic circulation of the North Ionian Gyre (NIG). During these anticyclonic periods, the transport of Atlantic Water into the Levant is reduced together with the transport of LIW out of the basin. These interannual fluctuations are superimposed on a long-term warming trend clearly evident from previous studies, showing a maximal temperature in 2018–2019, higher than the previously mentioned temperature peaks by ~0.7°C and ~0.4°C. The enhanced warming in 2018–2019 has caused a decrease in density (sigma) values of the LIW core, which gave way to the shallowest record of this water mass (~110-m depth), bringing it well within the lower photic zone. We suggest that a higher level of nutrients became available, supporting the observed long-term rise of the intergraded chlorophyll a (Chl.a) (0.89 mg m−2 year−1), with a maximum recorded during 2018–2019. The long-term record of the mixed layer depths shows no significant change; thus, the uplift of nutrients during winter mixing cannot support the trend and variations of the integrated Chl.a. Additional biological parameters of specific pico-phytoplankton populations and integrated bacterial production and abundance were measured in 2013–2021, but the measurements were too sparse to follow a clear interannual dynamics. Yet significantly higher average levels for integrated primary production and bacterial abundances were observed during the anticyclonic period (as for Chl.a). The combined impacts of the BiOS mechanism and global warming, and hence the increase in LIW residence time and buoyancy, may impact the primary producers’ biomass at the photic zone. This latter feedback may slightly counter the enhanced oligotrophication due to enhanced stratification.

Card game analysis for fast multi-criteria decision making

Multi-criteria decision methods are very popular in decision-making for many application fields thanks to their versatility and ability to involve qualitative and quantitative data in the analysis. On the other hand, the many of these techniques requires time consuming analysis and the involvement of expert users in the decision-making process. In this paper, a novel method named Card Game Analysis (CGA) is proposed to perform Multi-criteria Decision Making (MCDM) analysis. Such methodology uses a set of cards and a suitable game procedure to perform the analysis, allowing to determine indirectly tabulated weights of involved parameters (criteria, sub-criteria, alternatives, etc.) and obtain the ranking of priorities. The CGA is defined following the footsteps of the ``structuring of the problem’’, typical of the Analytic Hierarchy Process (AHP), and takes inspiration from an evaluation procedure presented in the related literature. In particular, the CGA is composed by the following steps: (1) structuring of the problem, (2) card setting, (3) card game weights evaluation, (4) synthesis of priorities. Finally, a validation through a comparison with the AHP procedure is performed by exploiting 25 case studies regarding the desirability of the enabling technologies of the Industry 4.0 for a set of companies in the Adriatic Ionian area.

Safety guidelines and a training framework for LNG storage and bunkering at ports

This paper summarises the main achievements of the project “Sustainability Performance of LNG-based maritime mobility”- (SUPER-LNG), financed by the Adriatic Ionian Interreg framework. Within this project, guidelines for safety reporting, risk assessment, and emergency planning of small scale LNG facilities and bunkering operations at ports have been developed. The main elements of these guidelines are presented in the article together with the results of their specific application on a small LNG facility, consisting of LNG pressurised tanks, LNG trucks, and a loading arm section. In addition, a training programme has been also created with the aim to promote safety and knowledge transfer on the LNG fuel chain to interested stakeholders, such as port operators, maritime instructors, port authorities, and stakeholders in planning, licensing, and emergency management practices related to LNG handling.

Challenges in Harmonized Environmental Impact Assessment (EIA), Monitoring and Decommissioning Procedures of Offshore Platforms in Adriatic-Ionian (ADRION) Region

A harmonized and integrated approach for monitoring and assessment of contamination, including hydrocarbon exploitation one, is required both by Marine Strategy Framework Directive (MSFD) at EU level and by the Ecosystem Approach (EcAp) program of the Barcelona Convention at Mediterranean level. A broad review of protocols of environmental impact assessment (EIA) procedures, monitoring and decommissioning of offshore platforms adopted by EU and non-EU countries along the Adriatic-Ionian seas was carried out in the framework of the Interreg offshore platforms in Adriatic-Ionian (ADRION) project HarmoNIA (Harmonization and networking for contaminant assessment in the Ionian and Adriatic Seas). The comparison of information provided by six ADRION countries and the application of a harmonized and integrated approach has highlighted specific challenges for managing offshore platform impacts emerged at ADRION level: (i) need of the same legislative level (the Offshore Protocol of Barcelona Convention is not ratified by all countries); (ii) set up of a task force of ADRION experts for discussing critical issues related to impacts of offshore platforms; (iii) harmonization, at the regional level, of EIA procedures, monitoring and decommissioning; (iv) need of an agreed and common list of recommended parameters to monitor in water, sediment and biota for the assessment of impacts due to platform installations and PFW discharges.

Towards a Foresight Methodology for Adriatic-Ionian Port Areas Focusing on the Energy Sector

In the Adriatic-Ionian (ADRION) area, cultural borders and political rifts caused a lack of cooperation and development as well as a weak application of EU policies. This, combined with small dimensions & infrastructural limits of the ADRION ports, made them lose their historical mission as places of exchanges, and suffer from low modernization rate, inadequate smartness level and unsolved issues related to sustainability and urban regeneration needs. On the other hand, ADRION ports are still complex ecosystems, offering the perfect substrate for becoming again actors of the development in this area. In this framework, the project PoWER: “Ports as Driving Wheels of Entrepreneurial Realm”, funded under the INTERREG V B ADRION Programme 1st call, aims to support the evolution of ports into Innovation Hubs, able to act as new “transmission belts” between ports and regions, and to exploit their untapped entrepreneurial potential. To do so, an action-based foresight methodology is proposed, used to smoothen the transition of a total of six (6) ADRION ports into such ‘Innovation Hubs’. This methodology encompasses five (5) interconnected steps, starting at a highest-level planning and ending in the strategic design of a common transition framework. The tools used to support the ports’ transition into innovation hubs do not differ from the common tools used in any other foresight activity, but are highly adjusted to the maritime sector. To this extent, an investigation to set the benchmark was conducted, whose results will be used to nurture a foresight process especially focused on the creation of reference scenarios for orienting the PoWER transition approach. Such framework does thus not only set the ground for a smoother transition of the ADRION ports, but will also support them to predict, pursue, and prepare for the potential opportunities, as well as threats, that the future holds.

The Evolution of Ports into Innovation Hubs: A Proposal for the Adriatic Ionian Area

PoWER - Ports as Driving Wheels of Entrepreneurial Realm is a EU project funded under the INTERREG V B ADRION Programme. It aims at recovering the historic role of Adriatic-Ionian (ADRION) port cities as pivotal centres of development and exchanges, by stimulating their evolution into Innovation Hubs (IHs) to exploit their untapped innovation potential. IHs will strive to establish a holistic and fertile innovation environment purposed to turn actual issues and challenges into shared opportunities as well as to build on them local integrated innovation supply chains. To this extent, the project tests a methodology specifically tailored for the ADRION port cities. It stands out from ongoing trends of the IH realm for a g-local approach aimed to fully leverage on port cities energies and resources in a smart and flexible way as well as to enhance their cross-border cooperation. The final aim of PoWER is the construction of the Innovation Hubs Network, the first network of maritime IHs, where local innovation pathways are shared and merged into a transnational strategy for joint evolution and development. The project is supported by a digital platform, aimed at gathering all members of the Network and to provide them with the necessary tools to implement their strategy. The PoWER Methodology and tools are characterized by a high degree of replicability, so to offer the chance to ADRION port cities to investigate and solve heterogeneous issues in close cooperation with each other.

Dense water formation and BiOS-induced variability in the Adriatic Sea simulated using an ocean regional circulation model

A performance analysis of the NEMOMED8 ocean regional circulation model was undertaken for the Adriatic Sea during the period of 1961–2012, focusing on two mechanisms, dense water formation (DWF) and the Adriatic–Ionian Bimodal Oscillating System (BiOS), which drive interannual and decadal variability in the basin. The model was verified based on sea surface temperature and sea surface height satellite measurements and long-term in situ observations from several key areas. The model qualitatively reproduces basin-scale processes: thermohaline-driven cyclonic circulation and freshwater surface outflow along the western Adriatic coast, dense water dynamics, and the inflow of Ionian and Levantine waters to the Adriatic. Positive temperature and salinity biases are reported; the latter are particularly large along the eastern part of the basin, presumably because of the inappropriate introduction of eastern Adriatic rivers into the model. The highest warm temperature biases in the vertical direction were found in dense-water-collecting depressions in the Adriatic, indicating either an inappropriate quantification of DWF processes or temperature overestimation of modelled dense water. The decadal variability in the thermohaline properties is reproduced better than interannual variability, which is considerably underestimated. The DWF rates are qualitatively well reproduced by the model, being larger when preconditioned by higher basin-wide salinities. Anticyclonic circulation in the northern Ionian Sea was modelled only during the Eastern Mediterranean Transient. No other reversals of circulation that could be linked to BiOS-driven changes were modelled.

Long-term variability of the southern Adriatic circulation in relation to North Atlantic Oscillation

Abstract. The interannual variability of the South Adriatic Gyre and its relation to the wind vorticity and the large-scale climatic pattern (North Atlantic Oscillation – NAO) was studied using the time series of satellite altimetric data and ocean surface wind products. The cyclonic circulation observed in the southern Adriatic area was partly sustained by the local wind forcing, as suggested by the positive correlation between the rate of change of the current vorticity and the wind-stress vorticity. Nevertheless, the influence of vorticity advection from the adjacent area (northern Ionian Sea) cannot be ignored and it is more significant during the anticyclonic phase of Adriatic–Ionian Bimodal Oscillation System. The geostrophic current vorticities of the southern Adriatic and northern Ionian seas are correlated with a time lag of 14 months, which approximately corresponds to an advection speed of ∼ 1 cm s−1. The different wind patterns observed during two NAO phases in the winter revealed a stronger positive vorticity during the negative NAO phase. Conversely, during the wintertime positive NAO phase the wind vorticity is characterized by lower positive or slightly negative values. Despite a statistically significant negative correlation between the NAO index and the wind vorticity, no unequivocal relationship between large climatic system and the interannual variability of the South Adriatic Gyre intensity was found due to additional effects of the vorticity advection from the Ionian. This can be explained by the fact that the Ionian circulation mode does not depend on the NAO variations. Therefore, the main result of this study is that the interannual variability of the southern Adriatic cyclonic circulation is a result of the combined influence of the vorticity advection from the Ionian and the local wind-curl effect.

La mafia albanese nell'Euroregione Adriatico-Ionica

The historical and democratic development of the Balkan area has been surely easier than the Italian one. Nevertheless, the member Countries of the Adriatic Ionian Euroregion share the presence of transnational mafia-type organizations, dedicated to illicit trafficking, limiting their capability to complete a democratic and socio-economic development.

The Adriatic-Ionian Macroregion in the Eurasian Socio-economic Future

This paper discusses the economic and social potential enabled by the Adriatic Ionian Macroregion (AIMr), characterized by a diffuse industrial pattern based on small and medium- sized enterprises, located in a European periphery, logistics and politics. The analyses show a diverse environment, made up of territories and states that move between vitality, modernization, economic backwardness and social inadequacy of infrastructure networks. In reference to the pillars identified by the EU, the ability to develop investments agreements with strategic political partnership between the states are the main instruments to achieve the objectives of modernizing the infrastructure and technology of this new political and economic realities.

Salinity in the Sicily Channel corroborates the role of the Adriatic–Ionian Bimodal Oscillating System (BiOS) in shaping the decadal variability of the Mediterranean overturning circulation

Abstract. Previous studies have demonstrated that the salinity in the Levantine basin depends on the intensity of the Atlantic water (AW) inflow. Moreover, its spreading eastward (to the Levantine basin) or northward (to the Ionian Sea) is determined by the Ionian circulation pattern, i.e. by the Adriatic–Ionian Bimodal Oscillating System (BiOS) mechanism. The aim of this paper is to relate salinity variations in the Levantine basin to the salt content variability in the core of the Levantine Intermediate Water (LIW) passing through the Sicily Channel (SC) and its possible impact on the Western Mediterranean Transition – WMT (i.e. the sudden salinity and temperature increase in the deep layer of the Algero-Provençal subbasin occurring since 2004). From the historical data set MEDAR/MEDATLAS in the Levantine and northern Ionian, we present evidence of decadal occurrences of extreme salinities associated with the varying influx of AW over the last 60 yr. Furthermore, we show that the salinity variations in the two subbasins are out of phase. High-salinity episodes in the Levantine are a pre-conditioning for the potential occurrence of the events like the Eastern Mediterranean Transient (EMT). Cross-correlation between the salinity time series in the Levantine basin and in the SC suggests that the travel time of the LIW is between 10 and 13 yr. Comparing the timing of the salinity increase associated with the WMT and the salinity in the LIW core in the SC, we estimate that the total time interval needed for the signal propagating from the Levantine to reach the deep mixed layers of the Algero-Provençal subbasin is about 25 yr. We also showed that the extra salt input from the eastern Mediterranean contribute up to about 60% to the salt content increase in the bottom layer of the western Mediterranean.

Distribution and bio-ecological features of Posidonia oceanica meadows along the coasts of the southern Adriatic and northern Ionian Seas

An update of the spatial distribution and bio-ecological features of Posidonia oceanica (L.) Delile meadows spread along the coasts of the southern Adriatic and northern Ionian Seas (Apulia region, southern Italy) is reported. Mapping carried out in 2004 indicated a remarkable reduction in the spatial distribution of P. oceanica meadows in the southern Adriatic Sea, mostly northwards of Bari, when compared with 1991 data. By contrast, in the northern Ionian Sea, the spatial distribution seems to be more stable. The P. oceanica meadows covered ∼330 km2 distributed along a total of 320 linear km coastline, mostly on the southern side of Apulia. Within natural variability, the differences in bio-ecological features could be due mainly to the presence of anthropic disturbance (urban, industrial and tourist pressure) rather than a significant geographical gradient between the Adriatic and Ionian Seas. However, the mean density values recorded in almost all the Adriatic stations fall within the ‘lower sub-normal density’ (LSD) range. By contrast, the mean density values observed in the Ionian meadows were generally within the ‘normal density’ (ND) range.

Carbonate metasomatism and CO 2 lithosphere–asthenosphere degassing beneath the Western Mediterranean: An integrated model arising from petrological and geophysical data

We present an integrated petrological, geochemical, and geophysical model that offers an explanation for the present-day anomalously high non-volcanic deep (mantle derived) CO 2 emission in the Tyrrhenian region. We investigate how decarbonation or melting of carbonate-rich lithologies from a subducted lithosphere may affect the efficiency of carbon release in the lithosphere–asthenosphere system. We propose that melting of sediments and/or continental crust of the subducted Adriatic–Ionian (African) lithosphere at pressure greater than 4 GPa (130 km) may represent an efficient mean for carbon cycling into the upper mantle and into the exosphere in the Western Mediterranean area. Melting of carbonated lithologies, induced by the progressive rise of mantle temperatures behind the eastward retreating Adriatic–Ionian subducting plate, generates low fractions of carbonate-rich (hydrous-silicate) melts. Due to their low density and viscosity, such melts can migrate upward through the mantle, forming a carbonated partially molten CO 2-rich mantle recorded by tomographic images in the depth range from 130 to 60 km. Upwelling in the mantle of carbonate-rich melts to depths less than 60–70 km, induces massive outgassing of CO 2. Buoyancy forces, probably favored by fluid overpressures, are able to allow migration of CO 2 from the mantle to the surface, through deep lithospheric faults, and its accumulation beneath the Moho and within the lower crust. The present model may also explain CO 2 enrichment of the Etna active volcano. Deep CO 2 cycling is tentatively quantified in terms of conservative carbon mantle flux in the investigated area.

Body size–abundance distributions of nano- and micro-phytoplankton guilds in coastal marine ecosystems

This study focuses on body size–abundance distributions of nano- and micro-phytoplankton guilds in coastal marine areas of the Southern Adriatic–Ionian region. The aim of the study was to evaluate the occurrence of common patterns of body size–abundance distributions in relation to physical, chemical and biological environmental forcing factors and to taxonomic composition of phytoplankton guilds. This paper is based on data collected during four oceanographic cruises carried out seasonally along the Southern Apulian coast (Adriatic and Ionian Seas, SE Italy) as a part of the INTERREG II Italy–Greece Program. The study was performed at 21 stations located on 7 transects perpendicular to the coastline, with 3 stations per transect at a distance of 3, 9 and 15 NM from the coastline. At each station, profiles of the major physical features of the water were determined and water samples were collected for phytoplankton and nutrient analysis. Overall, 320 nano- and micro-phytoplankton taxa were identified, 76% of which at species level, with phytoplankton cells ranging in size from 0.008 to 4697.54 ng. Body size–abundance distributions showed some common features: they were relatively invariant (average similarity 65%) with respect to taxonomic composition (average similarity 32%), right skewed (90%), leptokurtic (77%) and log normal (76%). Moreover, abiotic, biotic and spatial ecosystem components accounted for up to 75% of body size–abundance distribution variation. The results of this study suggest that body size–abundance distributions are an intrinsic property of marine phytoplankton communities, emphasising functional dependence on ecological constraints related to trophic factors and intra-guild coexistence relationships.

Space–time patterns of co‐variation of biodiversity and primary production in phytoplankton guilds of coastal marine environments

Abstract The relevance of biodiversity to ecosystem processes is a major topic in ecology. Here, we analyse the relationship between biodiversity and productivity of the nano‐ and micro‐phytoplankton guilds in coastal marine ecosystems. The patterns of variation of species richness, diversity and primary productivity (as 14C assimilation) were studied in two marine areas: a eutrophic–mesotrophic area beside the River Po delta (northern Adriatic) and an oligotrophic area around the Salento peninsula (southern Adriatic–Ionian). The study was carried out at 23 sites in the northern area and at 45 sites in the southern area. Sites were arranged on expected spatial and temporal gradients of primary productivity variation, according to distance from the coast, optical depths and seasonal period. 167 taxa were identified in the northern area and 153 taxa in the southern area. In both areas, the taxonomic composition of the nano‐ and micro‐phytoplankton guilds exhibited greater temporal than spatial variation. The latter was much higher in the southern area than in the northern area (average dissimilarity between stations being 70.7±0.8% and 44.7±4.2% respectively). Primary productivity varied in space and time on the gradients considered. Phytoplankton species richness and diversity exhibited significant patterns of variation in space and time; overall, these were inversely related to the primary productivity patterns in the northern area, whereas they were directly related in the southern area. The small individual size and the high turnover rate of phytoplankton are likely to underlie the observed relationships, which emphasized a threshold response to nutrient enrichment in agreement with the ‘paradox of enrichment’. Under resource enrichment conditions, the high turnover of producers leads to hierarchical partitioning of the available resources with an increasing dominance of a few species. Therefore, the relationship observed here seems likely to be explained by the complementarity hypothesis. Copyright © 2003 John Wiley & Sons, Ltd.