Article pubs.acs.org/est
Evaluation of Reaching the Targets of the Water Framework Directive in the Gulf of Finland Jose A. Fernandes,†,* Pirkko Kauppila,‡ Laura Uusitalo,†,‡ Vivi Fleming-Lehtinen,‡ Sakari Kuikka,† and Heikki Pitkan̈ en‡ †
Department of Environmental Sciences, University of Helsinki, Viikinkaari 1. FI-00014 Helsinki, Finland Finnish Environment Institute (SYKE), Mechelininkatu 34a. FI-00251 Helsinki, Finland
‡
ABSTRACT: This paper describes the development of the EU Water Framework Directive central water quality elements from 1970 to 2010 in the Gulf of Finland, a eutrophied subbasin of the Baltic Sea. The likelihood of accomplishing the management objectives simultaneously is assessed using Bayesian networks. The objectives of good ecological status in winter-time total nitrogen and phosphorus, summer-time chlorophyll-a and summer-time Secchi depth have not been met yet. In addition, the results indicate that it is unlikely for them to be achieved in the near future, despite the decreasing trend in nutrient concentrations over the past few years. It was demonstrated that neither phosphorus nor nitrogen alone controls summertime plankton growth. Reaching good ecological status in nutrients does not necessarily lead to good ecological status of chlorophyll-a, even though a dependency between the parameters does exist. In addition, secchi-depth status is strongly related to chlorophyll-a status in three of the four study-areas.
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INTRODUCTION
those that would be present with minimal anthropogenic disturbance. The definition of the kind of community that would occur with minimal anthropogenic disturbance is not a trivial task.8,9 Often there is a lack of data or the areas have specific properties. The Baltic Sea is a shallow, semienclosed brackishwater area characterized by a slow water renewal time and a four times larger drainage basin in relation to its surface water area. Eutrophication in the Baltic Sea10−12 is the result of long human exploitation of natural resources.13,14 Eutrophication has been identified as one of the key pressures on biological communities. For example, summertime cyanobacterial blooms are a regular phenomenon in the Baltic Sea.15 In the Gulf of Finland eutrophication has triggered a self-sustaining “vicious circle” of internal nutrient loading, associated with anoxic bottom sediments and amounts of organic material that can reach a thickness of 10 cm.16−18 Internal loading in the Gulf of Finland appears to counteract decreases in the external loads of phosphorus.19 In Finnish coastal waters, ecological classification has mainly been based on summertime phytoplankton chlorophyll-a (chl-a) levels. Secchi depth and wintertime total nutrients have been used as supporting variables. In the classification
The Water Framework Directive (“Directive 2000/60/EC of the European Parliament and of the Council establishing a framework for the Community action in the field of water policy”), with the EU Marine Framework Directive, is currently the most important legislative framework in the management of water quality in inland and coastal waters of the EU Member States.1 They apply to both the coastal and open sea areas of the pan-European waters.2−4 The Water Framework Directive (WFD5) was adopted in the European Union in October 2000. The stated aim is to reach or maintain good ecological status in all waters by 2015. Ecological status is determined by assessment against defined reference levels in biological, physicochemical, and hydromorphological quality elements. Type-specific reference conditions are established using historical data or modeling tools in order to form a baseline against which the changes can be measured.6,7 Ecological status is divided into five classes or levels (high, good, moderate, poor, and bad). The targeted status to be achieved being at least the boundary between good and moderate status. Due to the diversity of ecosystems, no absolute standards for the good status can be given across all European waters.5 Therefore, the directive only gives guidelines for the definition of the reference condition. This definition must be implemented by each Member state. According to the normative guidelines of the WFD, good ecological status is achieved when biological communities present are close to © 2012 American Chemical Society
Received: Revised: Accepted: Published: 8220
January 12, 2012 July 2, 2012 July 3, 2012 July 3, 2012 dx.doi.org/10.1021/es300126b | Environ. Sci. Technol. 2012, 46, 8220−8228
Environmental Science & Technology
Article
Figure 1. Coastal areas in the Gulf of Finland considered in this work.
conditions of water, exposure, water residence time and duration of ice cover.24,20 These coastal areas (Figure 1) were the Gulf of Finland inner archipelago (“eastern inner”, EI), the Gulf of Finland outer archipelago (“eastern outer”, EO), the Southwestern inner archipelago (“western inner”, WI), and the Southwestern outer archipelago (“western outer”, WO). The Gulf of Finland inner archipelago (EI) is shallow, less than 15 m deep. It is characterized by a mosaic of islands and numerous enclosed bays and estuaries. These features make it sheltered and restrict the water exchange between the inner coastal waters and the open sea. The bottom consists of semienclosed basins limiting horizontal and vertical water exchange. However, small trenches (20 m deep) extend to this area. The water is fully mixed or seasonally stratified. The thermocline in midsummer conditions is at a depth of 10 m. The duration of ice cover varies from 90 to 150 days. The Gulf of Finland outer archipelago (EO) is mainly formed by open water with small scattered islands. The water is moderately exposed with depths ranging between 15 and 30 m. Some of the deeps of the open sea extend into this area. Salinity is below 5 psu and sinks eastwards. The water is seasonally stratified. Residence time is short, measured in days. Ice cover lasts on average 90 days. The Southwestern inner archipelago (WI) west of the Porkkala Peninsula is characterized by (a) coastline with long shallow bays stretching deep into the mainland and large islands, sometimes connected to the mainland, intersected by narrow and shallow sounds. Deeps exceeding 30 m from the more saline waters of the open Gulf of Finland extend as far as the inner archipelago. The morphometry is similar to the Gulf of Finland inner archipelago, but the average salinity is over 5 psu. The Southwestern outer archipelago(WO) is much like the eastern outer archipelago in terms of its depth, island cover and bottom topography. It comprises small islands surrounded by wide stretches of deep open water with occasional shallows and deeper faults. The area is open and exposed. Salinity ranges between 5 and 6 psu.
schemes, the reference values of chl-a have been reconstructed empirically using historical Secchi observations from the early 1900s and present-day monitoring data.20,21 Reference values of total phosphorus and total nitrogen have been estimated by frequency distribution data. Basically, the high/good boundaries have been defined as reference values plus 20%, and the good/ moderate boundaries as high status plus 50%. Chl-a is chosen as a proxy to phytoplankton biomass because it is routinely monitored (quick and easy to measure). Winter nutrients are used due to negligible activity of primary producers in winter season.19,22 Winter nutrients control phytoplankton growth later in spring and summer.23 The likelihood of wintertime nutrients affecting ecological status classification based on chl-a must be quantified for two reasons; (1) to help the planning process in assessing the required reductions of loading in order to meet the environmental quality objectives of the directive; and (2) to give additional information for further indicator development and validation of the classification scheme. In this paper, the ecological status and the trends of summertime chl-a and Secchi depth as well as the wintertime concentrations of total nitrogen and phosphorus in the Gulf of Finland are examined (1970−2010). Using the high/good and good/moderate boundary values defined by the water directive as targets, the achievement of high and good ecological status in different coastal areas of the Gulf of Finland is studied. Finally, using probabilistic models, synchrony of the target levels set for each variable is examined in the Gulf of Finland, that is, the likelihood of reaching the target values of chl-a when the target values of nutrients are met. In particular, the uncertainties of the relationships between levels of nutrients and the other variables levels are evaluated. This uncertainty is crucial in being able to achieve a certain chl-a level by managing nutrient amounts in river basins by the WFD implementation actions.
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MATERIALS AND METHODS The Study Area. The study area (Figure 1) is based on the national coastal areas of Finland. According to the WFD, the areas are characterized by descriptors such as salinity, mixing 8221
dx.doi.org/10.1021/es300126b | Environ. Sci. Technol. 2012, 46, 8220−8228
Environmental Science & Technology
Article
Table I. Definition of Levels or Classes for Each Quality Element and Each Areaa vars.
season
depth
unit
ref
high
good
mod.
poor
bad
Chl-a Secchi Tot-P Tot-N
VII−VIII VII−VIII I−III I−III
0−10 m 0−5 m
μg/L m μg/L μg/L
2 5.5 19 325
4.6 1300
WO area
Chl-a Secchi Tot-P Tot-N
VII−VIII VII−VIII I−III I−III
0−10 m 0−5 m 0−5 m
μg/L m μg/L μg/L
1.6 8.9 18 230
7.4 920
EI area
Chl-a Secchi Tot-P Tot-N
VII−VIII VII−VIII I−III I−III
0−10 m 0−5 m 0−5 m
μg/L m μg/L μg/L
2.6 5.4
4.5
3.2−4.7 4.5−3
4.7−13 3−1.1
13−26 1.1−0.5
>26
