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Transitional waters: A new approach, semantics or just muddying the waters?
Estuarine, Coastal and Shelf Science 71 (2007) 359e363 www.elsevier.com/locate/ecss
Editorial
Transitional waters: A new approach, semantics or just muddying the waters?
Abstract Estuarine, Coastal and Shelf Science has throughout its history considered a diverse range of habitats including estuaries and fjords, brackish water and lagoons, as well as coastal marine systems. Its articles have reflected recent trends and developments within the estuarine and coastal fields and this includes the changing use of well-accepted terms. The term ‘‘transitional waters’’ first came to prominence in 2000 with the publication of the Water Framework Directive of the European Communities [European Communities, 2000. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy. Official Journal of the European Communities 43 (L327), 75 pp.], where ‘‘transitional waters’’ are defined as ‘‘bodies of surface water in the vicinity of river mouths which are partially saline in character as a result of their proximity to coastal waters but which are substantially influenced by freshwater flows’’. The inclusion of the term transitional waters in our own aims and scope reflects the evolution of language in this subject area, encompassing tidal estuaries and non-tidal brackish water lagoons. This article reflects on some of the difficulties posed by the use of the term and its attempts to be inclusive by incorporating fjords, fjards, river mouths, deltas, rias and lagoons as well as the more classical estuaries. It also discusses the problems of including in the term river mouths discharging either into predominantly brackish areas such as the Baltic Sea, or into freshwater-poor areas bordering the Mediterranean. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: transitional waters; estuaries; brackish waters; coastal waters; definitions
1. Introduction Regular readers of Estuarine, Coastal and Shelf Science may have noticed that the term ‘‘transitional waters’’ has recently been added to the list of research areas included in the aims and scope of the journal. The term ‘‘transitional waters’’ first came to prominence in 2000 with the publication of the Water Framework Directive of the European Communities (European Communities, 2000) as a means of completing the continuum between freshwaters and coastal waters. It is assumed here that the term was coined in order to retain a simple distinction of surface waters into freshwaters, intermediate waters and coastal waters. The Water Framework Directive (WFD) provides an integrated Europe-wide policy to improve the ecological quality in Community surface waters. The Directive has the aim of providing common principles and an overall framework for action throughout the member states of the European Community, and of improving the aquatic environment in the Community. This requires that the development of measures for 0272-7714/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.ecss.2006.08.025
ensuring good quality be established within a scheme for integrated river basin management (e.g. DEFRA, 2005). To achieve these aims, common definitions on the chemical and biological status of water in terms of quality should be established and environmental objectives need to be set to ensure that good status is achieved throughout the Community. Pollution from various sources is to be controlled and monitored and hydro-morphological changes are to be determined and where possible remedied with the aim of maintaining or where necessary improving water body status. The main goal of the WFD is to achieve good ecological status and good chemical status across European waters by 2015. By taking such a wideranging approach, the Ecosystem Approach will be implemented for European waters which will include an analysis of drivers and pressures affecting each water body (Apitz et al., 2006; Borja et al., 2006), hence the importance of correctly defining a water body and determining the natural and anthropogenic characteristics of that water body. The Directive recognises the different characteristics of different water bodies and so the first challenge was to define the
360
Editorial / Estuarine, Coastal and Shelf Science 71 (2007) 359e363
different types (or in WFD language, erroneously, typologies), to then set reference conditions for each type and then bring in programmes of measures to ensure that the water body has reached or can be managed to reach those good status conditions. In this process, the WFD somewhat mirrors the implementation of the Clean Water Act in the US (McLusky and Elliott, 2004). Accordingly, this whole sequence relies on the adequate definition of the types of water bodies and the placing of each geographic area into a given typology. The WFD defines ‘‘transitional waters’’ as ‘‘bodies of surface water in the vicinity of river mouths which are partially saline in character as a result of their proximity to coastal waters but which are substantially influenced by freshwater flows’’ (European Communities, 2000). For completeness, ‘‘coastal waters’’ are defined as ‘‘surface water on the landward side of a line, every point of which is at a distance of one nautical mile on the seaward side from the nearest point of the baseline from which the breadth of territorial waters is measured, extending where appropriate up to the outer limit of transitional waters’’. As far as can be seen, the term transitional waters has not yet entered the water management, administration and legislation of areas other than the European Union. While US and Australian legal acts and documents talk about wetlands and waters which are transitional, they do not use this term. The US Federal Water Pollution Control (Clean Waters) Act 1977 and the Estuaries and Clean Waters Act 2000 tend to merely refer to estuaries. The latter are then simply defined as ‘‘that part of a river or stream or other body of water having unimpaired connection with the open sea, where the sea water is measurably diluted with fresh water derived from land drainage. The term includes estuary-type areas of the Great Lakes’’ (US Code Collection, 2006). South Australia, an area with arguably as complex a set of estuarine areas as anywhere else, also avoids the use of the term transitional waters and keeps to the definition of an estuary as ‘‘A partially enclosed coastal body of water, including its ecosystem processes and associated biodiversity, which is either permanently, periodically, intermittently or occasionally open to the ocean within which there is a measurable variation in salinity due to the mixture of seawater with water derived from on or under the land’’ (DEH-GSA, 2006). The obvious first question to Estuarine and Coastal Scientists is, are transitional waters the same as or different from estuaries and how does the definition cope with lagoons which are clearly not open coastal waters but at the same time may not be measurably diluted by freshwater run-off? The principal definitions of estuaries, as we reviewed earlier (Elliott and McLusky, 2002), have all emphasised the dilution of seawater by freshwater, and in most cases have emphasised the role of the tides. Fairbridge’s definition, for example, defines an estuary as ‘‘an inlet of sea reaching into a river valley as far as the upper limit of tidal rise.’’ (Fairbridge, 1980). Other definitions, such as the Venice System (1958) on the classification of brackish waters have covered all brackish waters. As Elliott and McLusky (2002) noted, the term brackish has a wider meaning than estuarine and all waters with salinities between
those of sea and fresh water can be called brackish, whether they be large seas (e.g. Baltic or Caspian), closed lagoons or tidal estuaries. Thus, all estuaries by definition are brackish, but not all brackish waters are estuarine. Furthermore, as estuarine plumes can extend far into adjacent coastal waters, brackish waters can be away from land. The problem for European Community legislators is that there is full range of brackish water habitats from tidal estuaries to closed brackish lagoons to large brackish seas present in the member states of the European Community (Table 1). European estuaries, as defined by the principal definitions, are effectively confined to the Atlantic coast from mid-Norway at 60 N to southern Portugal at 37 N. These regions represent all European estuarine systems possessing predictable and pronounced influence from semi-diurnal tides, and generally have substantial intertidal habitats with an extensive benthic fauna and flora. But there are other parts of the European coastline, such as the coasts of Denmark, Sweden and the Baltic states which experience brackish water without any substantial tidal influence, so that Conley et al. (2000) working in Danish estuaries chose to define an estuary as ‘‘a partially enclosed body of water open to saline water from the sea and receiving freshwater from rivers, land run-off or seepage’’, noting the lack of tides as well as the broader range of freshwater inputs. Similarly on the margins of the Mediterranean Sea, despite the absence of tides, some river mouths are commonly called estuaries. There are also many non-tidal brackish water lagoons on the Mediterranean coast as well as on the Atlantic coast. Where there is an extended period of dry weather in the summer, coupled with varying rainfall during the winter, longshore drift at the seaward end may close a tidal estuary from its connection with the open sea for months at a time, creating so-called ‘‘temporary’’ estuaries. The term ‘‘transitional Table 1 Main physiographic forms to be included under the term transitional waters Type
Characteristics
Classical estuary
Tidally dominated at the seaward part; salinity notably reduced by freshwater river inputs; riverine dominance inward Land freshwater seepage or markedly seasonal riverine inputs; limited tidal influence; stratified; long narrow, glacially eroded sea inlet, step sided, sill at mouth Limited exchange with the coastal area through a restricted mouth; separated from sea by sand or shingle banks, bars, coral, etc., shallow area, tidal range 50 cm As above but with tidal range 50 cm Drowned river valley, some freshwater inputs; limited exchange Glacially carved embayment, sea inlet, smaller than fjord; limited freshwater inputs River outlet as well-defined physiographic coastal feature Low energy, characteristically shaped, sediment dominated, river mouth area; estuary outflow Outflow of estuary or lagoon, notably diluted salinity and hence differing biota than surrounding coast
Fjord
Lentic non-tidal lagoon
Lentic microtidal lagoon Ria Fjard River mouth Delta Coastal freshwater/ brackish water plume
Editorial / Estuarine, Coastal and Shelf Science 71 (2007) 359e363
waters’’ is thus intended as a simple term that can encompass all these habitats, most commonly tidal estuaries and non-tidal brackish lagoons, and might be easily understood by legislators in all countries. 2. Usage of the term transitional waters The WFD (European Communities, 2000) gives definitions for the ecological status of transitional waters, ranging from high to good to moderate status, with anything below moderate being classified as poor or bad. The definitions are by their nature very broad based, and member states are required to define the status of their own transitional waters. Much effort has been expended in defining the ‘‘typology’’ of the transitional waters in each member country of the European Community. This is necessary so that a baseline of current conditions can be determined (the so-called ‘‘reference conditions’’) and an appropriate monitoring regime can be developed, against which future improvements can be measured. The monitoring includes the chemical and biological elements (e.g. Apitz et al., 2006; Borja et al., 2006; Ferreira et al., 2006). The EC has provided guidance (European Commission, 2003) on the application of the WFD to transitional and coastal waters. The report recommends that transitional and coastal water bodies include the intertidal areas from the highest to the lowest astronomical tides, and gives detailed guidance on the designation of surface water categories (e.g. transitional water), surface water types (e.g. North Sea Muddy estuary) and surface water bodies (e.g. transitional water good status). It emphasises that the setting of boundaries between transitional waters, freshwaters and coastal waters must be ecologically relevant. For the purposes of the Directive, the main difference between transitional and coastal waters is the inclusion of the abundance and composition of the fish fauna in the list of biological quality elements for transitional waters. To select the seaward boundaries of transitional waters, member states are required to choose the most ecologically relevant method for their own state, which may commonly be a salinity limit (the lack of freshwater influence), a physiographic feature (Table 1) or based on modelling (an area with salinity substantially less than that of adjacent coastal water). For example, the United Kingdom has pragmatically used geographic features such as the lines of discontinuity reflecting the change from the open coast to the inside of an estuary. To define the freshwater boundary of transitional waters, member states can choose either a tidal limit or a fresh/salt boundary, but whichever method is chosen there should be no section unassigned. There is no guidance on the minimum size of any transitional water body, provided that every discrete body of water is assigned as a surface water body. Each country has had to interpret these guidelines, and some examples of these can be mentioned. In a recent paper in Estuarine, Coastal and Shelf Science, Ferreira et al. (2006) review the process of the definition of typologies and water bodies within the transitional water category. They give a methodology for evaluating natural
361
characteristics (such as classifications based on morphology or salinity) as well as human dimensions (such as pressures, loads and state). By applying the principles to three Portuguese transitional waters (Mondego estuary, Sado estuary, Ria Formosa) they show that although a final definition of water bodies will usually be a policy decision, a scientific approach for the division of transitional water systems into management units can usefully inform the decision-making process. The United Kingdom initially used a mechanistic approach to defining its typologies under the WFD using GIS and multivariate analyses of the variables mentioned in the WFD such as salinity, mixing, exposure, residence time, and substratum (http://www.wfduk.org/). The analysis, for all 179 UK estuaries, indicated the problems of pigeon-holing areas which essentially represent a continuum. It produced two major groups and several other small groups of transitional waters. One main group represented estuaries that were generally partly mixed or stratified, and which had a tendency to be mesohaline or polyhaline. The other major group of estuaries were fully mixed, polyhaline or euhaline estuaries which were sheltered, generally had a sand or mud substratum and tended to have extensive intertidal areas. The mechanistic approach was followed by an attempt using biological validation to determine differences in the groups and eventually, several (up to five) distinct types of TW were identified based on biological features such as biotopes. Casazza et al. (2003) indicate that the WFD legislation represents a new concept in Italian law by presenting an integrated approach where all water bodies are considered as complex ecosystems and the concept of the environmental quality of the water body based on its ecological and chemical status has been introduced. As expected, for transitional water bodies in Italy, the law also needs to take account of the specific characteristics of the Mediterranean Sea. Basset et al. (2006) and Tagliapietra and Ghirardini (2006) have further developed the criteria for the characterisation and classification of transitional waters, especially lagoons, in the Mediterranean area but their analyses also show the difficulty in using a single term across wide geographical areas and bio-geographic regions. Tagliapietra and Ghirardini (2006) discuss the difficulty of including Mediterranean lagoons in the term transitional waters as they are often not substantially influenced by any freshwater run-off. Also, for this and other reasons, they prefer the terms transitional environments and transitional habitats rather than transitional waters. Basset et al. (2006) subdivide Mediterranean transitional waters (for France, Greece and Italy) into running waters (as deltas and river mouths) and lentic (non-moving) ones. The latter were then mostly regarded as coastal lagoons which were subdivided into tidal and non-tidal areas and then each of these were subdivided by size. For Germany, Carstens et al. (2004) have described the development of a sampling programme for the Elbe estuary, designed to monitor the physico-chemical, hydro-morphological and biological characteristics of the Elbe’s transitional waters as basic information required under the WFD. They have found that helicopter monitoring will provide a sound basis
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for their surveillance monitoring, coupled with biological quality monitoring. Given the definition of transitional waters (at the start of this article), the greatest challenge to the use, and indeed perhaps misuse, of the term TW lies within the Baltic Sea area, much of which is both brackish and enclosed (depending on scale). Schernewski and Wielgat (2004) discuss river mouths rather than estuaries and highlight that each Baltic country has adopted a slightly different approach, but that most do not appear to be designating any TW. The countries instead discuss their coastlines in terms of salinity classes, even using the Venice System. Finland and Estonia with wholly Baltic coasts do not appear to have TW nor does Sweden which attempts to overcome problems in designating TW by even suggesting a further category, that of enclosed, brackish coastal types. The North Sea and Baltic coasts of Denmark have no TW, whereas Germany has designated TW for its North Sea estuaries (the Weser, Elbe, etc.) but not for its Baltic Sea estuaries and lagoons. In contrast, Lithuania and Latvia will consider the Curonian and other lagoons as TW, as well as the outlet of these to the Baltic and also the Daugava River. Poland has designated as its transitional waters the entire areas of the Szczecin Lagoon, Vistula Lagoon and a part of the Gulf of Gdansk (the inner Puck Bay) as well as parts of the Gulf of Gdansk and Pomeranian Bay where riverine plumes occur (Krzyminski et al., 2004). Finally, to show the further confusion, Lithuania and Poland have also included coastal areas receiving riverine/lagoonal plumes into the open Baltic as TW.
appear to be few tangible repercussions of defining an area as coastal when in fact it may be transitional. One is that one of the biological elements (estuarine fishes) is not monitored in coastal areas but is monitored in transitional and freshwaters e hence reducing the degree of monitoring required. If estuaries were to be subjected to a greater degree of water quality management than coasts, then the misclassification would have repercussions. For example, if a water body of given characteristics is defined as a transitional water body by one country but as coastal waters by another, then this may lead to different degrees of management and controls on activities. This problem was encountered with an earlier European Directive, the Urban Waste-water Treatment Directive, which stipulated the degree of sewage treatment required should be based on a water body’s sensitivity to showing the effects of eutrophication. Coastal areas were perceived as being less sensitive, given their higher assimilative capacity, whereas estuaries were deemed sensitive. It required several European member states to be subject to legal infraction proceedings before the Directive was clarified. Estuarine, Coastal and Shelf Science has throughout its history considered a diverse range of habitats including estuaries and fjords, brackish water and lagoons, as well as coastal marine systems, so the inclusion of the term transitional waters in our aims and scope reflects the evolution of language in this subject area, encompassing tidal estuaries and non-tidal brackish water lagoons. If ECSS readers wish to offer their views on the use of the term transitional waters they are invited to submit such comments to the editors.
3. Conclusions References It is of note that within a 6-year period, estuarine scientists and managers in Europe have got used to the term transitional waters and now, despite differences between countries, both use it freely and, at least individually, understand what they mean by it. It becomes useful shorthand but, as with many definitions, can mean different things to different workers. There will always be the problem of defining types within a continuum and it remains to be seen whether the differences in use will have any repercussions e whether legal, administrative or environmental. As shown here, the term is still not applied consistently throughout the European states and it remains to be seen whether it becomes adopted in other frameworks worldwide. The term is sometimes not being used as defined in the Water Framework Directive but is used more loosely and pragmatically as ‘‘aquatic areas which are neither fully open coastal nor enclosed or flowing freshwater areas’’; their boundaries may still be defined by physiographic features and discontinuities, or by salinity or any other hydrographic feature. Given that one of the aims of the WFD is to provide an integrated and seamless management of the catchment from headwaters through rivers and estuaries to the coasts, if the Directive is implemented fully it should not make any difference whether an area is defined as one water body or another. At present, given the infancy of the WFD implementation, there
Apitz, S.E., Elliott, M., Fountain, M., Galloway, T.S., 2006. European environmental management: moving to an ecosystem approach. Integrated Environmental Assessment & Management 2, 80e85. Basset, A., Sabetta, L., Fonnesu, A., Mouillot, D., Do Chi, T., Viaroli, P., Giordani, G., Reizopoulou, S., Abbiati, M., Carrada, G.C., 2006. Typology in Mediterranean transitional waters: new challenges and perspectives. Aquatic Conservation: Marine and Freshwater Ecosystems 16, 441e455. doi:10.1002/aqc.767. Borja, A., Galpasoro, I., Soluan, O., Muxika, I., Tello, E.M., Uriarte, A., Valencia, V., 2006. The European Water Framework Directive and the DPSIR, a methodological approach to assess the risk of failing to achieve good ecological status. Estuarine, Coastal & Shelf Science 66, 84e96. Carstens, M., Claussen, U., Bergemann, M., Gaumert, T., 2004. Transitional waters in Germany: The Elbe estuary as an example. Aquatic Conservation: Marine and Freshwater Ecosystems 14 (Suppl. 1), S81eS92. Casazza, G., Silvestri, C., Spada, E., 2003. Classification of coastal waters according to the new Italian water legislation and comparison with the European Water Directive. Journal of Coastal Conservation 9, 65e72. Conley, D.J., Kaas, H., Møhlenberg, F., Rasmussen, B., Windolf, J., 2000. Characteristics of Danish estuaries. Estuaries 25, 820e837. DEFRA (Department for Environment, Food and Rural Affairs, UK), 2005. Water Framework Directive e summary of reports of the Article 5 analysis reported to the Commission in March 2005. http://www.defra.gov.uk/environment/water/wfd/article5/index.htm. DEH-GSA (Department of Environment and Heritage, Government of South Australia), 2006. Draft Estuaries Policy & Action Plan. http://www.environment.sa.gov.au/coasts/estuaries.html (revision 21.02.06).
Editorial / Estuarine, Coastal and Shelf Science 71 (2007) 359e363 Elliott, M., McLusky, D.S., 2002. The need for definitions in understanding estuaries. Estuarine, Coastal & Shelf Science 55, 815e827. European Communities, 2000. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy. Official Journal of the European Communities 43 (L327), 75 pp. European Commission, 2003. Common implementation strategy for the Water Framework Directive (2000/60/EC) guidance document number 5. Transitional and coastal waters. Typology, reference conditions and classification systems. Office for Official Publications of the European Communities; Luxembourg, 116 pp. ISBN 92-894-5125-4; ISSN 1725-1087. Fairbridge, R.W., 1980. The estuary: its definition and geochemical role. In: Olausson, E., Cato, I. (Eds.), Chemistry and Geochemistry of Estuaries. John Wiley, New York, pp. 1e35. Ferreira, J.G., Nobre, A.M., Simas, T.C., Silva, M.C., Newton, A., Bricker, S.B., Wolff, W.J., Stacey, P.E., Sequeira, A., 2006. A methodology for defining homogeneous water bodies in estuaries e application to the transitional systems of the EU water Framework Directive. Estuarine, Coastal & Shelf Science 66, 468e482. Krzyminski, W., Kruk-Dowgiallo, L., Zawadzka-Kahlau, E., Dubrawski, R., Kaminska, M., Lysiak-Pastuszak, E., 2004. Typology of Polish marine waters. In: Schernewski, G., Wielgat, M. (Eds.), Baltic Sea Typology. Coastline Reports 4. ISSN: 0928-2734, 39e48. McLusky, D.S., Elliott, M., 2004. The Estuarine Ecosystem: Ecology, Threats and Management. Oxford University Press, Oxford, 214 pp. Schernewski, G., Wielgat, M., 2004. A Baltic Sea typology according to the EC-Water Framework Directive: integration of national typologies and the water body concept. In: Schernewski, G., Wielgat, M. (Eds.), Baltic Sea Typology. Coastline Reports 4. ISSN: 0928-2734, 1e26.
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Tagliapietra, D., Ghirardini, A.V., 2006. Notes on the coastal lagoon typology in the light of the EU Water Framework Directive: Italy as a case study. Aquatic Conservation: Marine & Freshwater Ecosystems 16, 457e467. US Code Collection, 2006. Title 16. Conservation, Chapter 33. Coastal Zone Management: Definitions. Cornell Law School, Legal Information Institute. http://www.law.cornell.edu/uscode/html/uscode16/usc_sec_16_ 00001453----000-.html (revision 19.06.06). Venice System, 1958. Symposium on the classification of brackish waters. Venice, April 8e14, 1958. Archives for Oceanography and Limnology 11 (Suppl.), 1e248.
D.S. McLusky* Editor Ardoch Cottage, Strathyre, Callander, Scotland FK18 8NF, UK *Corresponding author. E-mail address: [email protected] M. Elliott Member of Editorial Board Institute of Estuarine and Coastal Studies, University of Hull, UK E-mail address: [email protected] Available online 10 October 2006
Editorial
Transitional waters: A new approach, semantics or just muddying the waters?
Abstract Estuarine, Coastal and Shelf Science has throughout its history considered a diverse range of habitats including estuaries and fjords, brackish water and lagoons, as well as coastal marine systems. Its articles have reflected recent trends and developments within the estuarine and coastal fields and this includes the changing use of well-accepted terms. The term ‘‘transitional waters’’ first came to prominence in 2000 with the publication of the Water Framework Directive of the European Communities [European Communities, 2000. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy. Official Journal of the European Communities 43 (L327), 75 pp.], where ‘‘transitional waters’’ are defined as ‘‘bodies of surface water in the vicinity of river mouths which are partially saline in character as a result of their proximity to coastal waters but which are substantially influenced by freshwater flows’’. The inclusion of the term transitional waters in our own aims and scope reflects the evolution of language in this subject area, encompassing tidal estuaries and non-tidal brackish water lagoons. This article reflects on some of the difficulties posed by the use of the term and its attempts to be inclusive by incorporating fjords, fjards, river mouths, deltas, rias and lagoons as well as the more classical estuaries. It also discusses the problems of including in the term river mouths discharging either into predominantly brackish areas such as the Baltic Sea, or into freshwater-poor areas bordering the Mediterranean. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: transitional waters; estuaries; brackish waters; coastal waters; definitions
1. Introduction Regular readers of Estuarine, Coastal and Shelf Science may have noticed that the term ‘‘transitional waters’’ has recently been added to the list of research areas included in the aims and scope of the journal. The term ‘‘transitional waters’’ first came to prominence in 2000 with the publication of the Water Framework Directive of the European Communities (European Communities, 2000) as a means of completing the continuum between freshwaters and coastal waters. It is assumed here that the term was coined in order to retain a simple distinction of surface waters into freshwaters, intermediate waters and coastal waters. The Water Framework Directive (WFD) provides an integrated Europe-wide policy to improve the ecological quality in Community surface waters. The Directive has the aim of providing common principles and an overall framework for action throughout the member states of the European Community, and of improving the aquatic environment in the Community. This requires that the development of measures for 0272-7714/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.ecss.2006.08.025
ensuring good quality be established within a scheme for integrated river basin management (e.g. DEFRA, 2005). To achieve these aims, common definitions on the chemical and biological status of water in terms of quality should be established and environmental objectives need to be set to ensure that good status is achieved throughout the Community. Pollution from various sources is to be controlled and monitored and hydro-morphological changes are to be determined and where possible remedied with the aim of maintaining or where necessary improving water body status. The main goal of the WFD is to achieve good ecological status and good chemical status across European waters by 2015. By taking such a wideranging approach, the Ecosystem Approach will be implemented for European waters which will include an analysis of drivers and pressures affecting each water body (Apitz et al., 2006; Borja et al., 2006), hence the importance of correctly defining a water body and determining the natural and anthropogenic characteristics of that water body. The Directive recognises the different characteristics of different water bodies and so the first challenge was to define the
360
Editorial / Estuarine, Coastal and Shelf Science 71 (2007) 359e363
different types (or in WFD language, erroneously, typologies), to then set reference conditions for each type and then bring in programmes of measures to ensure that the water body has reached or can be managed to reach those good status conditions. In this process, the WFD somewhat mirrors the implementation of the Clean Water Act in the US (McLusky and Elliott, 2004). Accordingly, this whole sequence relies on the adequate definition of the types of water bodies and the placing of each geographic area into a given typology. The WFD defines ‘‘transitional waters’’ as ‘‘bodies of surface water in the vicinity of river mouths which are partially saline in character as a result of their proximity to coastal waters but which are substantially influenced by freshwater flows’’ (European Communities, 2000). For completeness, ‘‘coastal waters’’ are defined as ‘‘surface water on the landward side of a line, every point of which is at a distance of one nautical mile on the seaward side from the nearest point of the baseline from which the breadth of territorial waters is measured, extending where appropriate up to the outer limit of transitional waters’’. As far as can be seen, the term transitional waters has not yet entered the water management, administration and legislation of areas other than the European Union. While US and Australian legal acts and documents talk about wetlands and waters which are transitional, they do not use this term. The US Federal Water Pollution Control (Clean Waters) Act 1977 and the Estuaries and Clean Waters Act 2000 tend to merely refer to estuaries. The latter are then simply defined as ‘‘that part of a river or stream or other body of water having unimpaired connection with the open sea, where the sea water is measurably diluted with fresh water derived from land drainage. The term includes estuary-type areas of the Great Lakes’’ (US Code Collection, 2006). South Australia, an area with arguably as complex a set of estuarine areas as anywhere else, also avoids the use of the term transitional waters and keeps to the definition of an estuary as ‘‘A partially enclosed coastal body of water, including its ecosystem processes and associated biodiversity, which is either permanently, periodically, intermittently or occasionally open to the ocean within which there is a measurable variation in salinity due to the mixture of seawater with water derived from on or under the land’’ (DEH-GSA, 2006). The obvious first question to Estuarine and Coastal Scientists is, are transitional waters the same as or different from estuaries and how does the definition cope with lagoons which are clearly not open coastal waters but at the same time may not be measurably diluted by freshwater run-off? The principal definitions of estuaries, as we reviewed earlier (Elliott and McLusky, 2002), have all emphasised the dilution of seawater by freshwater, and in most cases have emphasised the role of the tides. Fairbridge’s definition, for example, defines an estuary as ‘‘an inlet of sea reaching into a river valley as far as the upper limit of tidal rise.’’ (Fairbridge, 1980). Other definitions, such as the Venice System (1958) on the classification of brackish waters have covered all brackish waters. As Elliott and McLusky (2002) noted, the term brackish has a wider meaning than estuarine and all waters with salinities between
those of sea and fresh water can be called brackish, whether they be large seas (e.g. Baltic or Caspian), closed lagoons or tidal estuaries. Thus, all estuaries by definition are brackish, but not all brackish waters are estuarine. Furthermore, as estuarine plumes can extend far into adjacent coastal waters, brackish waters can be away from land. The problem for European Community legislators is that there is full range of brackish water habitats from tidal estuaries to closed brackish lagoons to large brackish seas present in the member states of the European Community (Table 1). European estuaries, as defined by the principal definitions, are effectively confined to the Atlantic coast from mid-Norway at 60 N to southern Portugal at 37 N. These regions represent all European estuarine systems possessing predictable and pronounced influence from semi-diurnal tides, and generally have substantial intertidal habitats with an extensive benthic fauna and flora. But there are other parts of the European coastline, such as the coasts of Denmark, Sweden and the Baltic states which experience brackish water without any substantial tidal influence, so that Conley et al. (2000) working in Danish estuaries chose to define an estuary as ‘‘a partially enclosed body of water open to saline water from the sea and receiving freshwater from rivers, land run-off or seepage’’, noting the lack of tides as well as the broader range of freshwater inputs. Similarly on the margins of the Mediterranean Sea, despite the absence of tides, some river mouths are commonly called estuaries. There are also many non-tidal brackish water lagoons on the Mediterranean coast as well as on the Atlantic coast. Where there is an extended period of dry weather in the summer, coupled with varying rainfall during the winter, longshore drift at the seaward end may close a tidal estuary from its connection with the open sea for months at a time, creating so-called ‘‘temporary’’ estuaries. The term ‘‘transitional Table 1 Main physiographic forms to be included under the term transitional waters Type
Characteristics
Classical estuary
Tidally dominated at the seaward part; salinity notably reduced by freshwater river inputs; riverine dominance inward Land freshwater seepage or markedly seasonal riverine inputs; limited tidal influence; stratified; long narrow, glacially eroded sea inlet, step sided, sill at mouth Limited exchange with the coastal area through a restricted mouth; separated from sea by sand or shingle banks, bars, coral, etc., shallow area, tidal range 50 cm As above but with tidal range 50 cm Drowned river valley, some freshwater inputs; limited exchange Glacially carved embayment, sea inlet, smaller than fjord; limited freshwater inputs River outlet as well-defined physiographic coastal feature Low energy, characteristically shaped, sediment dominated, river mouth area; estuary outflow Outflow of estuary or lagoon, notably diluted salinity and hence differing biota than surrounding coast
Fjord
Lentic non-tidal lagoon
Lentic microtidal lagoon Ria Fjard River mouth Delta Coastal freshwater/ brackish water plume
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waters’’ is thus intended as a simple term that can encompass all these habitats, most commonly tidal estuaries and non-tidal brackish lagoons, and might be easily understood by legislators in all countries. 2. Usage of the term transitional waters The WFD (European Communities, 2000) gives definitions for the ecological status of transitional waters, ranging from high to good to moderate status, with anything below moderate being classified as poor or bad. The definitions are by their nature very broad based, and member states are required to define the status of their own transitional waters. Much effort has been expended in defining the ‘‘typology’’ of the transitional waters in each member country of the European Community. This is necessary so that a baseline of current conditions can be determined (the so-called ‘‘reference conditions’’) and an appropriate monitoring regime can be developed, against which future improvements can be measured. The monitoring includes the chemical and biological elements (e.g. Apitz et al., 2006; Borja et al., 2006; Ferreira et al., 2006). The EC has provided guidance (European Commission, 2003) on the application of the WFD to transitional and coastal waters. The report recommends that transitional and coastal water bodies include the intertidal areas from the highest to the lowest astronomical tides, and gives detailed guidance on the designation of surface water categories (e.g. transitional water), surface water types (e.g. North Sea Muddy estuary) and surface water bodies (e.g. transitional water good status). It emphasises that the setting of boundaries between transitional waters, freshwaters and coastal waters must be ecologically relevant. For the purposes of the Directive, the main difference between transitional and coastal waters is the inclusion of the abundance and composition of the fish fauna in the list of biological quality elements for transitional waters. To select the seaward boundaries of transitional waters, member states are required to choose the most ecologically relevant method for their own state, which may commonly be a salinity limit (the lack of freshwater influence), a physiographic feature (Table 1) or based on modelling (an area with salinity substantially less than that of adjacent coastal water). For example, the United Kingdom has pragmatically used geographic features such as the lines of discontinuity reflecting the change from the open coast to the inside of an estuary. To define the freshwater boundary of transitional waters, member states can choose either a tidal limit or a fresh/salt boundary, but whichever method is chosen there should be no section unassigned. There is no guidance on the minimum size of any transitional water body, provided that every discrete body of water is assigned as a surface water body. Each country has had to interpret these guidelines, and some examples of these can be mentioned. In a recent paper in Estuarine, Coastal and Shelf Science, Ferreira et al. (2006) review the process of the definition of typologies and water bodies within the transitional water category. They give a methodology for evaluating natural
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characteristics (such as classifications based on morphology or salinity) as well as human dimensions (such as pressures, loads and state). By applying the principles to three Portuguese transitional waters (Mondego estuary, Sado estuary, Ria Formosa) they show that although a final definition of water bodies will usually be a policy decision, a scientific approach for the division of transitional water systems into management units can usefully inform the decision-making process. The United Kingdom initially used a mechanistic approach to defining its typologies under the WFD using GIS and multivariate analyses of the variables mentioned in the WFD such as salinity, mixing, exposure, residence time, and substratum (http://www.wfduk.org/). The analysis, for all 179 UK estuaries, indicated the problems of pigeon-holing areas which essentially represent a continuum. It produced two major groups and several other small groups of transitional waters. One main group represented estuaries that were generally partly mixed or stratified, and which had a tendency to be mesohaline or polyhaline. The other major group of estuaries were fully mixed, polyhaline or euhaline estuaries which were sheltered, generally had a sand or mud substratum and tended to have extensive intertidal areas. The mechanistic approach was followed by an attempt using biological validation to determine differences in the groups and eventually, several (up to five) distinct types of TW were identified based on biological features such as biotopes. Casazza et al. (2003) indicate that the WFD legislation represents a new concept in Italian law by presenting an integrated approach where all water bodies are considered as complex ecosystems and the concept of the environmental quality of the water body based on its ecological and chemical status has been introduced. As expected, for transitional water bodies in Italy, the law also needs to take account of the specific characteristics of the Mediterranean Sea. Basset et al. (2006) and Tagliapietra and Ghirardini (2006) have further developed the criteria for the characterisation and classification of transitional waters, especially lagoons, in the Mediterranean area but their analyses also show the difficulty in using a single term across wide geographical areas and bio-geographic regions. Tagliapietra and Ghirardini (2006) discuss the difficulty of including Mediterranean lagoons in the term transitional waters as they are often not substantially influenced by any freshwater run-off. Also, for this and other reasons, they prefer the terms transitional environments and transitional habitats rather than transitional waters. Basset et al. (2006) subdivide Mediterranean transitional waters (for France, Greece and Italy) into running waters (as deltas and river mouths) and lentic (non-moving) ones. The latter were then mostly regarded as coastal lagoons which were subdivided into tidal and non-tidal areas and then each of these were subdivided by size. For Germany, Carstens et al. (2004) have described the development of a sampling programme for the Elbe estuary, designed to monitor the physico-chemical, hydro-morphological and biological characteristics of the Elbe’s transitional waters as basic information required under the WFD. They have found that helicopter monitoring will provide a sound basis
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for their surveillance monitoring, coupled with biological quality monitoring. Given the definition of transitional waters (at the start of this article), the greatest challenge to the use, and indeed perhaps misuse, of the term TW lies within the Baltic Sea area, much of which is both brackish and enclosed (depending on scale). Schernewski and Wielgat (2004) discuss river mouths rather than estuaries and highlight that each Baltic country has adopted a slightly different approach, but that most do not appear to be designating any TW. The countries instead discuss their coastlines in terms of salinity classes, even using the Venice System. Finland and Estonia with wholly Baltic coasts do not appear to have TW nor does Sweden which attempts to overcome problems in designating TW by even suggesting a further category, that of enclosed, brackish coastal types. The North Sea and Baltic coasts of Denmark have no TW, whereas Germany has designated TW for its North Sea estuaries (the Weser, Elbe, etc.) but not for its Baltic Sea estuaries and lagoons. In contrast, Lithuania and Latvia will consider the Curonian and other lagoons as TW, as well as the outlet of these to the Baltic and also the Daugava River. Poland has designated as its transitional waters the entire areas of the Szczecin Lagoon, Vistula Lagoon and a part of the Gulf of Gdansk (the inner Puck Bay) as well as parts of the Gulf of Gdansk and Pomeranian Bay where riverine plumes occur (Krzyminski et al., 2004). Finally, to show the further confusion, Lithuania and Poland have also included coastal areas receiving riverine/lagoonal plumes into the open Baltic as TW.
appear to be few tangible repercussions of defining an area as coastal when in fact it may be transitional. One is that one of the biological elements (estuarine fishes) is not monitored in coastal areas but is monitored in transitional and freshwaters e hence reducing the degree of monitoring required. If estuaries were to be subjected to a greater degree of water quality management than coasts, then the misclassification would have repercussions. For example, if a water body of given characteristics is defined as a transitional water body by one country but as coastal waters by another, then this may lead to different degrees of management and controls on activities. This problem was encountered with an earlier European Directive, the Urban Waste-water Treatment Directive, which stipulated the degree of sewage treatment required should be based on a water body’s sensitivity to showing the effects of eutrophication. Coastal areas were perceived as being less sensitive, given their higher assimilative capacity, whereas estuaries were deemed sensitive. It required several European member states to be subject to legal infraction proceedings before the Directive was clarified. Estuarine, Coastal and Shelf Science has throughout its history considered a diverse range of habitats including estuaries and fjords, brackish water and lagoons, as well as coastal marine systems, so the inclusion of the term transitional waters in our aims and scope reflects the evolution of language in this subject area, encompassing tidal estuaries and non-tidal brackish water lagoons. If ECSS readers wish to offer their views on the use of the term transitional waters they are invited to submit such comments to the editors.
3. Conclusions References It is of note that within a 6-year period, estuarine scientists and managers in Europe have got used to the term transitional waters and now, despite differences between countries, both use it freely and, at least individually, understand what they mean by it. It becomes useful shorthand but, as with many definitions, can mean different things to different workers. There will always be the problem of defining types within a continuum and it remains to be seen whether the differences in use will have any repercussions e whether legal, administrative or environmental. As shown here, the term is still not applied consistently throughout the European states and it remains to be seen whether it becomes adopted in other frameworks worldwide. The term is sometimes not being used as defined in the Water Framework Directive but is used more loosely and pragmatically as ‘‘aquatic areas which are neither fully open coastal nor enclosed or flowing freshwater areas’’; their boundaries may still be defined by physiographic features and discontinuities, or by salinity or any other hydrographic feature. Given that one of the aims of the WFD is to provide an integrated and seamless management of the catchment from headwaters through rivers and estuaries to the coasts, if the Directive is implemented fully it should not make any difference whether an area is defined as one water body or another. At present, given the infancy of the WFD implementation, there
Apitz, S.E., Elliott, M., Fountain, M., Galloway, T.S., 2006. European environmental management: moving to an ecosystem approach. Integrated Environmental Assessment & Management 2, 80e85. Basset, A., Sabetta, L., Fonnesu, A., Mouillot, D., Do Chi, T., Viaroli, P., Giordani, G., Reizopoulou, S., Abbiati, M., Carrada, G.C., 2006. Typology in Mediterranean transitional waters: new challenges and perspectives. Aquatic Conservation: Marine and Freshwater Ecosystems 16, 441e455. doi:10.1002/aqc.767. Borja, A., Galpasoro, I., Soluan, O., Muxika, I., Tello, E.M., Uriarte, A., Valencia, V., 2006. The European Water Framework Directive and the DPSIR, a methodological approach to assess the risk of failing to achieve good ecological status. Estuarine, Coastal & Shelf Science 66, 84e96. Carstens, M., Claussen, U., Bergemann, M., Gaumert, T., 2004. Transitional waters in Germany: The Elbe estuary as an example. Aquatic Conservation: Marine and Freshwater Ecosystems 14 (Suppl. 1), S81eS92. Casazza, G., Silvestri, C., Spada, E., 2003. Classification of coastal waters according to the new Italian water legislation and comparison with the European Water Directive. Journal of Coastal Conservation 9, 65e72. Conley, D.J., Kaas, H., Møhlenberg, F., Rasmussen, B., Windolf, J., 2000. Characteristics of Danish estuaries. Estuaries 25, 820e837. DEFRA (Department for Environment, Food and Rural Affairs, UK), 2005. Water Framework Directive e summary of reports of the Article 5 analysis reported to the Commission in March 2005. http://www.defra.gov.uk/environment/water/wfd/article5/index.htm. DEH-GSA (Department of Environment and Heritage, Government of South Australia), 2006. Draft Estuaries Policy & Action Plan. http://www.environment.sa.gov.au/coasts/estuaries.html (revision 21.02.06).
Editorial / Estuarine, Coastal and Shelf Science 71 (2007) 359e363 Elliott, M., McLusky, D.S., 2002. The need for definitions in understanding estuaries. Estuarine, Coastal & Shelf Science 55, 815e827. European Communities, 2000. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy. Official Journal of the European Communities 43 (L327), 75 pp. European Commission, 2003. Common implementation strategy for the Water Framework Directive (2000/60/EC) guidance document number 5. Transitional and coastal waters. Typology, reference conditions and classification systems. Office for Official Publications of the European Communities; Luxembourg, 116 pp. ISBN 92-894-5125-4; ISSN 1725-1087. Fairbridge, R.W., 1980. The estuary: its definition and geochemical role. In: Olausson, E., Cato, I. (Eds.), Chemistry and Geochemistry of Estuaries. John Wiley, New York, pp. 1e35. Ferreira, J.G., Nobre, A.M., Simas, T.C., Silva, M.C., Newton, A., Bricker, S.B., Wolff, W.J., Stacey, P.E., Sequeira, A., 2006. A methodology for defining homogeneous water bodies in estuaries e application to the transitional systems of the EU water Framework Directive. Estuarine, Coastal & Shelf Science 66, 468e482. Krzyminski, W., Kruk-Dowgiallo, L., Zawadzka-Kahlau, E., Dubrawski, R., Kaminska, M., Lysiak-Pastuszak, E., 2004. Typology of Polish marine waters. In: Schernewski, G., Wielgat, M. (Eds.), Baltic Sea Typology. Coastline Reports 4. ISSN: 0928-2734, 39e48. McLusky, D.S., Elliott, M., 2004. The Estuarine Ecosystem: Ecology, Threats and Management. Oxford University Press, Oxford, 214 pp. Schernewski, G., Wielgat, M., 2004. A Baltic Sea typology according to the EC-Water Framework Directive: integration of national typologies and the water body concept. In: Schernewski, G., Wielgat, M. (Eds.), Baltic Sea Typology. Coastline Reports 4. ISSN: 0928-2734, 1e26.
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Tagliapietra, D., Ghirardini, A.V., 2006. Notes on the coastal lagoon typology in the light of the EU Water Framework Directive: Italy as a case study. Aquatic Conservation: Marine & Freshwater Ecosystems 16, 457e467. US Code Collection, 2006. Title 16. Conservation, Chapter 33. Coastal Zone Management: Definitions. Cornell Law School, Legal Information Institute. http://www.law.cornell.edu/uscode/html/uscode16/usc_sec_16_ 00001453----000-.html (revision 19.06.06). Venice System, 1958. Symposium on the classification of brackish waters. Venice, April 8e14, 1958. Archives for Oceanography and Limnology 11 (Suppl.), 1e248.
D.S. McLusky* Editor Ardoch Cottage, Strathyre, Callander, Scotland FK18 8NF, UK *Corresponding author. E-mail address: [email protected] M. Elliott Member of Editorial Board Institute of Estuarine and Coastal Studies, University of Hull, UK E-mail address: [email protected] Available online 10 October 2006