Two Special Features on integrated coastal zone management, especially along the Mediterranean Sea, result from a MEDCOAST conference held in Hammamet (Tunisia), 20–25 October 2001. In this first Special Feature some papers are presented on ecological and biological research related to integrated coastal zone management. All over Europe coastal environments are threatened by human activities such as urbanization, industrial development, fisheries, aquaculture, recreation and tourism. Research has to be developed that can be applied to similar case studies in different countries. Methods of monitoring are necessary and baseline data have to be available in order to judge the significance of changes in the abiotic and biotic environment. Examples of studies included in this Special Feature are mainly from southern banks of the Mediterranean Sea but there is also an example from Estonia and one from the Canary Islands.

Detailed analysis of the land cover of the Estonian coastal zone is presented based on Estonian laws on coastal zone management, the CORINE Land Cover (CLC) system, the status of protected areas, and administrative division data of Estonia. By law the coastal zone is defined as a 200-m wide zone landward from the mean sea level line. The length of the Estonian coastline (including the islands) is 3794 km. The 200-m zone of the Estonian coast is very diverse. Out of the 34 CORINE land cover types represented in Estonia 30 are found in the coastal zone. Three dominating land cover types in the coastal zone of Estonia are inland marshes, coniferous forest and semi-natural grassland. Their total share is 47%; the other 27 land cover types represented here cover 53% of the coastal zone. The Estonian coastal zone is generally in a good natural condition. The proportion of artificial surfaces throughout the zone is merely 4.7%, while agricultural landscapes cover only ca. 10%. Land cover data for the coastal zone are also presented by county. Of the 200-m coastal zone 24% is under protection, which is more than twice the value for Estonia as a whole (11%). Legislative protection of the coastal zone is presently satisfactory. The use of the CORINE Land Cover system enables comparisons with other European regions since CLC data have been compiled for most of Europe.

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This study forms part of the Action Plan for the Conservation of Marine Vegetation in the Mediterranean Sea (United Nation Environmental Program). It was carried out in June 2000 in the Farwà Lagoon, Libya. The mapping of the main benthic vegetation was achieved by compiling the field observations (transect method), and remote sensing of SPOT satellite images. The phytobenthos in the Farwà lagoon covers an area of 1820 ha (65%). Three benthic macrophyte species dominate, namely the marine phanerogams Cymodocea nodosa and Posidonia oceanica, and the alga Caulerpa prolifera.

Dead Posidonia oceanica leaves (litter) form veritable mounds in the vicinity of the openings leading to open sea. These leaves, which come from the coastal sea, are brought into the lagoon by currents and tides; their decomposition will lead to high oxygen consumption and the release of hydrogen sulphide.

The phenological data of Posidonia oceanica shoots sampled in the lagoon are similar to those from other stations in the Mediterranean.

Conversely, the lepidochronological parameters of shoots sampled in the central part of the lagoon exhibit values that are substantially higher than those generally recorded in the Mediterranean. The mean number of leaves produced annually is 9.9 (mean value for the Mediterranean: 7.5) and the rhizome growth rate is of 35.7 mm.yr⁻¹ (mean value for the Mediterranean: 7.5 mm.yr⁻¹). This hypersaline environment would seem to provide optimum growth conditions for the species Posidonia oceanica.

The macro-algae communities observed in the south lake of Tunis are characterized by the predominance of nitrophilous algae which are in the order of biomass importance: Ulva, Cladophora and Enteromorpha. We have noted seasonal changes of alga distribution. The wind appears to be one of the most important factors influencing this distribution. The total biomass reaches a maximum in the spring. Rapid decomposition of the biomass leads to a severe ecological imbalance, resulting in crises of anoxia and fish death.

A restoration project has already started. It aims at removal of contaminated muds and the introduction of a new circulation system.

The main objectives of this work were to collect information on the distribution and biomass of the phytobenthic communities as a first step in the constitution of a database for further comparison.

This work deals with the biodiversity and distribution of benthic macrophytes in the Ghar El Melh lagoon, a Mediterranean coastal lagoon located in the North of Tunisia. An inventory was made of the benthic flora and submerged macrophyte communities were mapped during two successive campaigns (the summer of 1999 and the winter of 2000). The following 24 macrophyte species were identified: seven red algae, two brown algae, 11 green algae, and four marine angiosperms. The results were compared with available data from the literature.

Ruppia cirrhosa is the most dominant species. It is found in all lagoon parts, except in the west sector. Ruppia beds are usually associated with Cladophora forming heterogeneous communities. During summer Ruppia cirrhosa shows a large distribution, covering an area of ca. 21.4 km², with dense, extensive beds covering 80–100%. In winter, several Cladophora species have a very large distribution as well, covering nearly an area of 28.5 km² with an average cover of 46%. The green algae Caulerpa prolifera is confined to the eastern part of the lagoon which is mainly affected by seawater.

In comparison with previous situations, many transformations were observed in biodiversity and spatial distribution of the dominant communities. Thus, Cymodocea nodosa and Zostera beds, which dominated in the 1970s, were replaced by Zostera and Caulerpa prolifera in the 1980s and are currently succeeded by Ruppia cirrhosa and Cladophora.

Restoration of the Ghar El Melh lagoon will enable an increase in the exchange with the open sea and the circulation of water, in particular in the confined zones. This should considerably improve the water quality and would positively influence the phytobenthic communities.

The aim of this study was to investigate the distribution of mercury compounds in marine sediments and mussel tissues collected in the lagoon of Bizerte, Tunisia, during two seasons (summer and winter). Inorganic mercury (Hg² ) concentrations in sediments were found to be highly variable, ranging from 0.04 nmol.g⁻¹ to 3.22 nmol.g⁻¹ (dry weight) with a mean value of 0.52 nmol.g⁻¹. Anthropogenic sources of Hg² , most probably metallurgy or tire production industries, have been evidenced. The mean concentration of monomethylmercury (MeHg ) in the surface sediments is 2.32 pmol g⁻¹ ranging from below the detection limit (0.45 pmol.g⁻¹) to 14.6 pmol.g⁻¹. No significant variation was observed between winter and summer seasons for both mercury species concentration in the sediments. The Hg² concentrations in mussel tissues are also variable, ranging from 0.007 to 1.347 nmol.g⁻¹ (dry weight). The mean concentration is 0.70 nmol.g⁻¹. In these tissues, Hg² is generally the major compound, making up ca. 88% of total mercury concentrations. However, methylmercury concentrations are significant and homogeneous, ranging from 62 to 121 pmol.g⁻¹ (mean 96 pmol.g⁻¹). The results suggest that a fraction of the inorganic mercury load in the sediments of the lagoon undergoes methylation pathways. MeHg produced is assimilated in the mussels more readily than Hg² .

The aim of this paper is to give an overview of the use of indicators and indices for the evaluation of the status of the marine environment. This procedure represents a new integrated approach, where the coastal marine environment is considered as a complex ecosystem, to be studied in all its components. Recent national and international legislation introduces this new concept of environmental quality, while requiring data and information on parameters which were not evaluated in the past. Until now, monitoring and control programmes for the marine environment focused mainly on the chemical status of coastal waters. However, aspects of the biological quality are fundamental for the description of the ecological status; the need for the development of biological indicators and indices provides a challenge for the scientific and technical community managing the marine environment. Living organisms represent the most appropriate indicators for the environmental quality of a water body, as they integrate biotic and abiotic components through their adaptive response. The available information on the current use of biological indicators and indices are illustrated and suggestions and examples on the Mediterranean sea environment are discussed.

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Interannual changes in the shoot density, biomass and leaf length of the seagrass Cymodocea nodosa and two descriptors of the associated fish communities (total fish abundance and species richness) were evaluated at Playa Blanca (Lanzarote, Canary Islands) from March 2001 to April 2002 to provide evidence for responses to the impact of a marina construction. The seagrass bed under influence, as well as a control location, were sampled using an experimental design which consisted of three sites nested within each of these two locations. We tested the null hypothesis that these parameters would not change over time as a result of this construction.

A three-way mixed and symmetrical ANOVA detected significant ‘Time of sampling × Control vs Impact’ interactions for the shoot density, biomass and leaf length. The same interactions were observed for the descriptors of the fish communities using a two way orthogonal ANOVA. We detected an initial fast increase in the mean leaf length as a possible morphological response to a reduction in the amount of light at the bottom. Furthermore, a significant decrease was obtained for the penetration of light into the water column in the perturbed bed. Therefore, we obtained significant evidence to reject the null hypothesis offered by our study.

Two species of the green alga genus Caulerpa are considered as invasive in Tunisia: Caulerpa racemosa and C. taxifolia. C. racemosa is found in a many new localities at the central and southern Tunisian coast, and even in the North of the country in colder water. These new observations lead to the hypothesis of the multiplicity of the origins of the introduction of the species and suggest possible invasive potentialities. The general thallus, and more particularly the number, the shape as well as the arrangement of ramelli on fronds allowed us to identify four morphologically different groups. These groups could be either different systematic entities or polymorphic variations of the same taxon due to different ecological conditions. Caulerpa taxifolia was observed for the first time in Tunisia at the roadstead of Sousse in the beginning of the year 2000. It is recognized as identical to that found in the other Mediterranean localities (GenBank number AJ228960). Up to the end of March 2000, a submarine prospecting campaign revealed an affected area of about 350 ha in front of 2 km of coast. Colonies of Caulerpa taxifolia disseminating in this area appear in isolated spots. form, In the growing stage, they form surfaces varying between 0.5 to 6 m² and located 20 to 100 m from each other. The total covered surface was estimated to be between 0.5 and 1 ha.

The coastline of South Africa is characterized by extensive dune fields which are threatened by development, and thus the demand of stabilization of drift sand will increase. The non-invasive alien grass species Ammophila arenaria is at present the dominant sand stabilizer. Due to its foreign origin and invasiveness in North America its use was criticized and indigenous sand-binding species would be preferred. The germination requirements of the native Arctotheca populifolia, Ipomoea pes-caprae, Myrica cordifolia and Scaevola plumieri were investigated. The results showed that for all four species the total germination time and germination phase could be shortened and germination success (number of germinated seeds) improved. The different scarification and stratification treatments broke the dormancy of I. pes-caprae, M. cordifolia and S. plumieri, whereas the seeds of A. populifolia were not dormant. Seeds of I. pes-caprae and M. cordifolia had induced an innate dormancy, respectively, whereas the type of dormancy in seeds of S. plumieri dormancy processes remained unknown.

Nomenclature: Arnold & De Wet (1993)

We studied the impact of livestock grazing on the distribution of Branta bernicla berniclam (Dark-bellied Brent goose) in the Dutch Wadden Sea during spring. It was hypothesized that livestock facilitate short-term (within-season) grazing for geese as well as long-term (over years). Therefore we measured grazing pressure by geese in salt marsh and polder areas that were either grazed (spring-grazed) or ungrazed during spring (summer-grazed). Additionally, we carried out a preference experiment with captive geese to test the preference between spring-grazed and summer-grazed polder swards. We furthermore compared patterns of use by geese between long-term ungrazed and grazed salt marshes.

In May, there is a difference in grazing pressure by geese between polder pastures that are grazed or ungrazed during spring. In this month, the ungrazed polder pastures are abandoned and the geese shift to either the grazed polder pastures or to the salt marsh. Vegetation in the polder that had been spring-grazed had a lower canopy height and a higher tiller density than summer-grazed vegetation. The captive geese in the preference experiment showed a clear preference for vegetation that had been spring-grazed by sheep over ungrazed vegetation. Goose grazing pressure was negatively correlated to canopy height, both on the polder and on the salt marsh. Within the plant communities dominated by Festuca rubra and Puccinellia maritima, marshes that were intensively grazed by livestock generally had higher grazing pressure by geese than long-term ungrazed or lightly grazed salt marshes.

Nomenclature: van der Meijden (1990).