Estuaries and coastal waters: research and management - Introduction
Erdal Özhan
Chairman, MEDCOAST, Middle East Technical University, 06531 Ankara, Turkey;
Tel. +90 312 2105429; Fax +90 312 2101412; E-mail ozhan@metu.edu.tr
The Second International Conference on the Mediterranean Coastal Environment, MEDCOAST 95, 2427 October 1995, Tarragona, Spain, which focused on the conservation and sustainable development of the coastal and marine areas of the Mediterranean and the Black Sea, was organized jointly by the MEDCOAST Secretariat (Middle East Technical University, Ankara, Turkey) and the Local Organizing Committee, led by the Laboratori d'Enginyeria Maritima (Universitat Politecnica de Catalunya, Barcelona, Spain).
The conference addressed three ma or subject areas, namely: 'Physical, ecological and conservation issues', 'Integrated coastal and sea resource management and development', and 'Coastal engineering, modeling and data management'. The papers were presented in four parallel sessions, which had the following themes:
Keynote session; Coastal and marine ecosystems; Ecological issues; Ecosystem management; Integrated ecosystem management and conservation; Coastal and marine conservation; Biochemical issues; Protected areas; Historical and archaeological issues; Tourism; Beach and dune management; Coastal planning; National and regional CZM practices; Socio-economical aspects; Social issues; Education; Legislation and legal issues; International cooperation; Deltas; Lagoons; Coastal processes; Human impact; Coastal erosion and control; Sediment transport; Beaches; Sea level rise and consequences; EIA; Remote sensing; Data management and GIS; Water quality issues; Water pollution; Pollution assessment; Coastal and marine pollution; Coastal water quality management; Hydrodynamic modeling; Transport processes and modeling; Physical oceanography and climatology; Coastal engineering; Marinas; Harbours and navigation; Wind waves; Wind wave modeling and Climatology.
170 participants from 26 countries, representing various disciplines and affiliations, attended the Conference. 163 papers which were received by the MEDCOAST Secretariat before the deadline, were included in a three-volume conference proceedings (1997 pages + indices) (Özhan 1995a). Many of the papers present original work which is significant or specific for the Mediterranean and Black Sea. This special issue of the Journal of Coastal Conservation contains eight selected papers on several issues relevant to Mediterranean coastal management.
The MEDCOAST international conference is organized in a different Mediterranean or Black Sea town every two years. The third conference, MEDCOAST
97, was organized in Qawra, Malta from 11 - 14 November 1997 jointly by the MEDCOAST Secretariat (Ankara, Turkey) and the Euro-Mediterranean Center for Insular Coastal Dynamics (ICOD) (Valetta, Malta). Another special volume of JCC which will include several selected papers from the MEDCOAST 97 proceedings is in preparation. The fourth MEDCOAST conference will be organized jointly with the fourth conference on the Environmental Management of Enclosed Coastal Seas (EMECS) in Antalya (Turkey) dur
ing 2-6 November 1999. This joint conference is expected to be a major world congress focusing on the management of coastal and sea areas of enclosed basins.
Summary of the papers in this Special Feature
In a conceptual paper on the definition of budget models for the evolution of deltas, Capobianco et al. call attention for the vulnerability of low lying deltaic areas to global climatic change and to human activities including 'construction of dams and other flood protection structures, hydrocarbon and groundwater extraction, uncontrolled land reclamation, large scale dredging, inadequate land use planning'. The authors briefly mention the problems of three main Mediterranean deltas, namely Po, Ebro and Rhone They stress the importance of the capability to indicate the proper management of deltas and the sustainable use of the deltaic resources. Morphological evolution and ecosystem functioning of deltas are affected by natural or anthropogenic changes in the 'budgets' of sediment, water and salt. The authors discuss the problem of space and time scales for complex large systems, interrelationship between the model resolution and predictability at small and large scales. They further describe the concept of 'physiographic unit modeling', and provide a classification system for identifying physiographic units. Capobianco et al. conclude that for complex systems like deltas, modeling is first of all a problem of organization, rather than the definition of the dynamics in a strict sense, and point out the use of Geographic Information Systems (GIS) together with models to form 'Geographically referenced environmental information systems' for managing deltaic areas.
Palanques & Guillén illustrate some of the concepts exposed in the paper by Capobianco et al. by presenting a historical account of the changes which took place in the Ebre Delta over a century, mainly due to extensive damming of the river and its tributaries. The data presented by the authors show that the regulated water discharge decreased by a factor of 1/3, and the sediment input to the coast dropped to 1/200 of the value in 1880. The deterioration of the water quality due to increased wastes resulting from concentrated human activities along the river and the reservoirs, mainly from urban, industrial and agricultural developments, is pointed out. The authors mention the modified regime of salt water (wedge) intrusion along the river due to regulated water discharge. The wedge which could move significantly upstream and could even get completely washed out when the river discharges showed drastic seasonal changes prior to the construction of the dams, is now more or less stabilized, its head reaching 14 km upstream when the river discharge is regulated in the range of 150 - 400 m3/s. The authors discuss the sediment transport along the coast of the Ebre Delta, which is a micro-tidal and wave-dominated (short period and medium intensity) coast. The longshore sediment transport is bi-directional which is usually typical of eroding mature delta coasts. The authors provide data on the annual erosion (accretion) rates along the delta coast and on the change of the mean grain size, as well as qualitative information on the change of the morphological features during stormy periods. In conclusion, Palanques and Guillén list the important environmental issues presently prevailing on the Ebre Delta coast, and the economical sectors which are negatively affected. They also refer to various schemes which are considered to decrease (manage) the erosion of the delta coast.
Day et al. report on the results of a two-year project on the study of the accretionary response of the Venice Lagoon wetlands and the effectiveness of a number of management approaches for protecting wetlands at present and in the case of sea level rise expected in the future, due to subsidence and eustatic rise. The divergence of the Brenta and Piave Rivers to discharge directly to the Adriatic Sea and the reduction of the marine sediment input through the inlets due to construction of long jetties, resulted in a negative sediment budget for the lagoon at the annual rate of 1.1 x 106 m3/yr. The salt marshes of the Lagoon have decreased over the century from 12 000 ha to 4 000 ha due to erosion, reclamation and subsidence. In their study, the authors selected six sites (50 in x 50 in in size) with variable environmental conditions, to study the sedimentation rates at various time scales. Accretion over a period of 2 - 4 weeks was measured by collecting material on horizontal test surfaces, whereas the seasonal and annual accretion were measured by the change in surface elevation with respect to man-made marker horizons. The results show great variability in the scale of the sedimentation process at six test sites, the annual accretion rates ranging from 0.2 to 2.3 cm/yr. The authors argue that if the relative sea level rise increases to ca. 4 mm/yr as predicted by IPCC, the accretion rate at only one of the six studied sites will offset such a high water level rise, and all the other parts will suffer from the loss of marshes. Fencing of the marsh area was observed by the authors to increase the sedimentation rate significantly on one hand, and to enhance vegetation spread on the other. Day et al. discuss several management measures for long term protection of the Venice lagoon wetlands, including measures for decreasing wave energy and increasing sediment input, and point out the need for a holistic and integrated approach for water and sediment management.
Kitsiou & Karidis, in their paper on categorical mapping, report on a methodology for quantitative assessment of eutrophication based on the spatial distributions of concentrations of four parameters: phosphate, nitrate, ammonia, and phytoplankton cell number. The authors use the data for these four parameters obtained from measurements taken at 20 stations in the Saronicos Gulf (Greece) during the months from April to September between 1980-1982. The first step in the proposed method is to obtain the maps showing the aerial concentration distribution of each of the four selected parameters by using the measured values and an interpolation method. Then, the study area is subdivided into a number of cells and the average concentrations of four parameters for each cell are calculated. Later, a multiple criteria evaluation method (the regime method) is used. The overall ranking of each cell with respect to the level of eutrophication was calculated from the average concentrations of the four indicator parameters. Finally, the results were compared with pre-assigned critical concentrations of each of the four indicator parameters in order to decide if the level of the organic enrichment in each cell falls into one of the following categories: oligotrophic, lower-mesotrophic, upper-mesotrophic and eutrophic. A spatial map showing the state of eutrophication was prepared. The results of Kitsiu and Karidis show that the northern tip of the Gulf (five cells) which gets affected from the waste discharge of the sewage outfall of the metropolitan area of Athens, is eutrophic, whereas most of the cells in the studied area are found to be in the lower-mesotrophic scale.
Camiñas et al, in their paper on 'Ecomálaga', describe a comprehensive multi-disciplinary data base for the continental shelf of the Alborán Sea, which characterizes the transition from Atlantic to Mediterranean conditions. The data base which contains physical, chemical, biological and sedimentological data including temperature, salinity, pH, dissolved oxygen, chlorophyll a, nitrate, nitrite, phosphate, silicate, zooplankton biomass, ichthyplankton, species composition and sediment characteristics, was created by using the measurements taken in nine quarterly surveys covering a period of slightly more than two years (October 1992 - December 1994). The authors, in addition to describing the main features of the data base, briefly summarize the results deduced from the measured data which include the seasonal change of the general circulation pattern, the occurrence of the upwelling phenomenon and the Atlantic influence.
The use of remote sensing for deriving scientific information to support coastal management practices is discussed by Barale & Larkin. The authors utilize the Coastal Zone ColourScanner (CZCS) images which were originally obtained from 1979 to 1985, and were archived in the framework of the Ocean European Colour Archive Network (OCEAN) project (1990) for the European seas for studying the typical patterns of near coastal features. Individual images of pigment concentration were generated for each available day, which were then analyzed on a pixel-by-pixel basis, to obtain monthly, seasonal and annual composite images. The authors argue that on the basis of the sea surface colour field, the Mediterranean is divided into two parts: the eastern and the western basins, in other words the border line connecting the Sicilian Channel, the Strait of Messina, and the Strait of Otranto and the Adriatic being a western sub-basin. Colour features similar to the western Mediterranean are also observed for the northern Aegean. The authors attribute this similarity to the runoff from the northern continental basin and to the river run-offs. They further note the Alborán gyre, the filament at Capo Passero at the southern tip of Sicily, and the Rhodes gyre core as the other permanent features of the Mediterranean pigment field. The composite images also illustrate the distinct, permanent plumes of the main rivers, including the Ebre, Rhone, Po and Nile, all discharging into the Mediterranean. However, the authors warn that it is impossible to distinguish the biogenic pigments from the dissolved and suspended materials present within the plumes, and call attention to the more significant temporal (seasonal) variability in the western basin with enhanced patterns and higher concentrations in late winter to early spring. The authors conclude that optical remote sensing techniques have a great potential for the Mediterranean due to low cloudiness, availability of historical data, and dominance of the ,case I waters' in which planktonic pigments govern the optical properties. They finally mention the strong correlation between the basin-wide seasonal patterns and the annual climatic cycle of the Mediterranean, and point out the strong role which could be played by atmospheric forces over the Mediterranean continental margins over the spatial and marginal distributions of water constituents.
The use of aerial photography for the mapping of ,meadows' of Posidonia oceanica, a phanerogam endemic to the Mediterranean, is discussed by Pasqualini, et al. Posidonia oceanica is a protected marine plant species in France since 1988. Posidonia meadows play an important role in marine ecology and coastal stability. In their study, the authors use analog colourphotos scale 1/20 000 and additional photos scale 1/25 000. Scanning of the photos resulted in digital data having a pixel resolution of 5 m, which were assembled to form a mosaic of the study area. These data were used to prepare the map of benthic assemblages for the whole study area which extended about 100 km in length and 0 to 20 m water depth across the coast. The authors pay attention to the variation of the colourresponse of a certain bottom type at different water depths and used a differentiation scale for diagnosis which varied with water depth. They further utilized already published data and occasional data from divers to extend their mapping all the way up to the depth which marks the limit of the Posidonia area. This limiting water depth changed from 17 m to 38 m, with a mean value of 32 to 35 m for the entire length of the coastline. They found out that the onshore limit of the Posidonia bed in front of the river mouths was at relatively shallower depths. This was attributed to the sensitivity of the plant to the reduced salt content. The authors estimate the area covered by Posidonia meadows in depths greater than 20 m, which is twice the area at depths less than 20 m. The extensive occurrence of the grass beds along the Corsican coast is linked by the authors to the low level of human activity along the coast.
In the final paper of this Special Feature, Manzanera et al. present the results of an experimental study on seagrass mortality. A number of anthropogenic activities in the coastal zone change the sedimentation patterns and rates which pose a potential danger for the burial and mortality of benthic communities. The authors conducted field experiments at two Posidonia meadows along the Catalan coast (Spain) at the depths of 4 m, 5 m, and 13 m. Extra sedimentation was applied to the plants by filling vertically placed PVC pipes at four levels: (1) no sediment addition -reference data-,
(2) 5 - 7 cm, (3) 9 - 10 cm, and (4) 13 - 14 cm thick sediment burials. The authors found that the mortality rate of the shoots was not site dependent. It increased with the depth of burial and the 15 cm sedimentation was seen to be the critical value which caused mortality of all shoots within the experimental period.
Management aspects
This Special Feature focuses on several issues of coastal management in the Mediterranean. One of them is the management of special areas such as deltas, wetlands and lagoons. The ecological (and economical) significance and values of these special areas as life support systems are well understood worldwide. Significant interest has been shown by researchers in recent years for investigating the natural functioning of such systems and their responses to antropogenic alterations with the aim of managing such coastal areas in a better way (Bach et al. and Runca et al. in Özhan 1993a; Arnoux-Chiavassa et al., Bettinetti et al., Comin et al. in Özhan 1995a; D'Alpagos et al., Day et al. (a), Ergun et al., 1995, Ibanez, et al., Jimenez et al., Menendez et al. and Sanchez-Arcilla et al. Özhan 1995b; Breber and Capobianco & Otter in Özhan 1996a; Breber and Fer & Kapdasli in Özhan 1997a). Deltas, wetlands and lagoons have been lost or degraded at an alarming rate over the last century due to economical development at such coastal areas -mainly urbanization, agriculture, tourism, industry, transportation and groundwater/hydrocarbon extraction - and along the river banks damming of rivers, urbanization and agriculture (Capobianco et al. and Palanques & Guillén, this issue). Presently, the anticipated sea level rise imposes further problems and management issues as discussed by Day et al. (this issue) (see also: Hulsbergen et al. and SanchezArcilla et al. in Özhan 1993b; Capobianco et al. and Day et al. (b) in Özhan 1995a; Blasi in Özhan 1997b). Deltas, wetlands and lagoons which often form the integral parts of large and complex systems (both physical and ecological) need to be managed with a holistic and integrated approach (Day et al., this issue). The historical data on natural and antropogenic changes (negative in almost all cases) on such systems provide valuable guidance (serving as a framework: 'do not' or 'do with care') for planners and managers (Palanques & Guillén, this issue). Water, sediment and salinity budgets are the key factors for managing the deltaic or lagoonal systems (Capobianco et al., Day et al., this issue). Negative water and sediment balances are the prime reasons for endangering the physical integrity of such coastal units. Changes in the salinity budget, in addition to those of water and sediment, affect the functioning and eventually the composition of these most valuable coastal ecosystems. Many physical and ecological phenomena taking place in the deltaic/lagoon systems have a wide range of spatial and temporal scales. Any investigation (such as modeling) and management efforts should take these scale differences into account (Capobianco et al., this issue). As the scale of a phenomenon gets larger (in both spatial and temporal terms), it is far more difficult to understand the dynamics which govern the phenomenon, and the uncertainty and risk which is inherent to management options and practices become greater. For a, wider context of deltas and coastal wetlands, their most important steering processes, engineering and climate change; see also van der Linden et al. (1987), Day (1992) and Jeftic et al. (1992). Two recent more general English studies on coastal environments and problems are Carter (1988) and Viles & Spencer (1995).
The second important aspect of the Mediterranean coastal management which is dealt with in this Special Feature is the illustration of the potential uses of modern tools and instruments such as mapping (Kitsiou & Karidis, this issue), reliable and comprehensive data bases (Camiñas et al., this issue), and the remote sensing through satellite or aircraft (Barale & Larkin, Pasqualini et al., this issue). The pollution from land based sources and nutrient enrichment of coastal waters are among the topics which have been dealt with extensively in the context of the Mediterranean Action Plan since its inception in the year of 1975 (Bou-Franch in Özhan 1996b). Although a great part of the Mediterranean basin (especially the eastern sub-basin) is oligotrophic, many embayments, bays and gulfs have been excessively polluted by the land-based sources (mainly by domestic and agricultural wastes) up to the eutrophic level. Indeed, two of the first four 'priority action projects' which were carried out in the framework of the Mediterranean Action Plan during 1987-1989 dealt with the state of pollution and the management of water quality in Kastella (Croatia) and Izmir (Turkey) Bays. Monitoring of water quality in such problematic areas should be an integral part of the management efforts. The qualitative assessment and mapping of the overall nutrient enrichment level on a spatial basis as described by Kitsiou & Karidis (this issue), is a valuable support to guiding management decisions. The comprehensive coastal data bases as described by Carniflas et al. provide many opportunities for elaboration and analysis of data with the purpose of obtaining valuable information for management (See also: Darras et al. in Özhan 1995b).
Many of the coastal management issues which arise either from natural causes or from human activities have a large spatial scale. Remote sensing can provide reliable and relatively cheap data and information in a short time, and its potential use is becoming more and more evident. The usefulness of various types of images from satellites to study coastal phenomena have been well demonstrated (Barale & Larkin, this issue; Barale and Folving and Maktav & Kapdaşlı in Özhan 1993b; Dreoni et al. in Özhan 1995b; Assendorp et al., Barale & Zin, Minacapilli et al. and Pasqualini et al. in Özhan 1997b). As demonstrated by Pasqualini et al. (this issue) aerial photography, and more recently the digital aerial photography (Edwards et al. in Özhan 1996b; Curr et al. in Özhan 1997b) have a great potential for precise mapping of coastal resources and development, and for contributing to coastal GIS, both of which will no doubt be very useful tools for the technical side of decision making in the process of coastal management (see also Askne 1995).
During the last decade, a good deal of scientific interest has been shown to the understanding of the biology of Posidonia oceanica, a marine plant endemic to the Mediterranean, and to the management of this valuable resource (Manzanera et al., Pasqualini et al., this issue; see also Mazzella et al. and Augier et al. a, b in Özhan 1993a; Pergent-Martini & Pergent in Özhan 1995a; Pasqualini et al. and Pergent & Pergent-Martini in Özhan 1996; Mendez et al., Pasqualini et al. and Venturi et al. in Özhan 1997a). In many Mediterranean countries however, this plant has not yet been included in the list of protected species (unlike France), and the Posidonia meadows are threatened by human activities including industrial pollution (such as in the case of Gulf of Gabes, Tunisia), dredging of sea bottom, sedimentation, etc.
Acknowledgements. I thank Çiğdem Gencel of the MEDCOAST Secretariat for assisting in the preparation of this Special Feature, and the following referees for reviewing the papers: Prof. T. Balkaş Dr. V. Barale, Dr. A. Baric, Dr. A. Bernstein, Mr. M. Capobianco, Prof. H. Coccossis, Dr. J.W. Day Jr., Dr. O.E. Frihy, Dr. S. Ylkay, Dr. J.A. Jimenez, Dr. 1. Kayan, Dr. A. Koh, Dr. D. Maktav, Dr. R.J. Nicholls, Prof. E. Özsoy, Dr. C. Pergent-Martini, Dr. A. Pavasovic, Dr. N.P. Psuty, Dr. M. Rairnondi, Dr. E. Runca, Prof. C. Saydam, Mr. 1. Trumbic, Prof. A. Vallega, Dr. S. Vallerga, Mr. J. van der Weide, Prof. P. Vellinga, Prof. A.T. Williams. The publication of this Special Feature is partly sponsored by the Mediterranean Action Plan, Priority Actions Program Regional Activity Center. The interest and support of Mr. Ivica Trumbic is kindly acknowledged.
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