Swedish Institute for the Marine Environment

Transcription

1 Swedish Institute for the Marine Environment National Centre for Analysis of the Marine Environment CONSULTATION RESPONSE Ref. No Rv The comments have been based on information taken from the EIA Scoping Report, Proposal for environmental investigation programme for the fixed link across Fehmarnbelt (coast-coast) June It is evident from the consultation papers that experience gained in the construction of the Öresund Fixed Link and the Great Belt Fixed Link will be put to use in the preliminary work on a fixed link across the Fehmarn Belt. Extensive and detailed studies on water transport and biology/ecology were made in conjunction with these construction projects. It is necessary for links to be made to these previous studies for continuity and development of the current state of knowledge. What a fixed link may come to mean in terms of changed emissions and discharges from traffic will be elucidated in the new studies. This is an important issue at a time when transport issues are often associated with environmental impact, to a greater extent than when the Öresund Fixed Link, for example, was discussed. It is good for a referral body to have access to substantial data, for example on water depth and flow conditions along the whole route of waterways that may be affected by future construction. The short consultation period, which in addition falls during the summer, means that better documentation would be appreciated to an even greater degree. An example of substandard documentation among the papers concerned is a photocopy of the chart of the Fehmarn Belt which is so blurred that it is not possible to read depth figures. One relevant issue regarding Swedish conditions and the rest of the Baltic Sea area is possible impact on organisms that at some stage migrate between the Fehmarn Belt area and Swedish waters. Another is effects on quality and quantity in the exchange of water between the Kattegat and Skagerrak and the Baltic Sea. It is also important that the current state of knowledge on the environmental impacts of this type of offshore construction

2 is enhanced, and issues concerning study methodology and strategy will therefore be addressed. The Swedish Institute for the Marine Environment considers that knowledge from previous construction projects must be utilised ahead of the preparation of follow-up programmes for the construction of the envisaged Fehmarn Belt Fixed Link. Phenomena that differ in the construction projects can then be highlighted and given extra attention. The Swedish Institute for the Marine Environment has the following comments and proposals. Water transport 70-80% of the water flowing into and out of the Baltic Sea passes through the Fehmarn Belt. It is therefore of key importance to be able to ensure that the exchange of water between the Kattegat and Skagerrak and the Baltic Sea will not be obstructed during and after the construction of the Fehmarn Belt Fixed Link. The bridge option at least a tunnel option located entirely below the present-day seabed level is being discussed may mean both obstruction of water passage and changes in the quality of water passing through. It is apparent from papers sent out that these effects will be monitored both with a number of fixed stations that continuously measure hydrographic variables and with a large number of intermittent, ship-based measurements. As the text of the consultation papers perhaps by necessity is succinct, it is not evident how the actual measurement programme is intended to be designed. Comments are therefore made below on the procedure that should be followed. A choice was made in construction of the Öresund Bridge to carry out compensatory dredging as well as reconstruction around Pepparholm with the aim of approaching a zero solution for water transport to and from the Baltic Sea. The consultation papers do not show an equivalent solution is to be approached for the Fehmarn Belt. However, it is not likely that the problems will be the same in construction of the Fehmarn Belt Fixed Link, partly because the Dars Sill forms a shallow threshold to the rest of the Baltic Sea far to the east of the bridge. Any changes in flow-past both horizontally and vertically may, however, affect the quantity and quality of the water (composition with regard to both salinity and temperature). The measurements to be performed must therefore include profiles with continuous measurements both of flow and of salinity and temperature with high resolution vertically and horizontally. The Swedish Institute for the Marine Environment considers that long-term measurements of water transport and water quality (salinity and temperature)

3 must be performed in representative segments of the whole water mass so that the possibility of devising a zero solution is ensured. Such a measurement programme, and proposals for measures that may need to be implemented, should be presented in detail in the future EIA. Fish Fish spawning with associated spawning migrations of adult fish, hatching success and subsequent transport of juvenile fish are affected by both water movements and physical (to some extent also chemical) disturbances such as turbidity. These issues appear to be on the way to being elucidated according to the consultation papers. With regard to cod, one of the species affected, however, there are a number of issues meriting further attention. Cod in Swedish Baltic waters are divided into western and eastern populations with a north-south dividing line at Bornholm. The pelagic spawning strategy of cod makes the species sensitive to water flows. The western population may have or have had its spawning grounds to a large extent in and around the Fehmarn Belt. There are therefore a number of issues here that need to be addressed: 1. Division between eastern and western populations in the Baltic Sea. This issue has long been the subject of discussion. The populations may be connected through juvenile/larval drift but are kept apart by "natal homing" mechanisms (Svedäng et al. 2010). It can therefore be imagined that the Fehmarn Bridge is also important for the eastern population. 2. The location and size of the spawning grounds in the western Baltic Sea. How import is the Fehmarn Belt area for the western cod population of the Baltic Sea? 3. Possible impact on larval spread (and therefore survival) through a changed flow pattern in the Fehmarn Belt The Swedish Institute for the Marine Environment considers that studies must be performed clarifying the relative significance of the Fehmarn Belt as a spawning ground for cod particularly in the western Baltic Sea population, but also for the eastern population. A knowledge base must be developed ensuring that the construction can be performed without adversely affecting spawning success and larval transport. Sea-birds It is apparent form the consultation papers that extensive studies of bird migration, some using radar, will be carried out. The number of sea-birds close to the water surface is also be measured. There are extensive mussel beds along the Danish side of the Fehmarn Belt that

4 are significant as a foraging ground during the winter for sea-birds with hatching sites adjacent to Swedish waters. It is therefore very important not to damage the large mussel beds located along the Danish side of the Fehmarn Belt. There is obviously previous experience here (for example Hammar et al. 2009) of the effects of dredging and sludging that should be utilised. The EIA Scoping report indicates that consideration has been given to conducting a preliminary study with one visit per year for two years to investigate both the distribution of mussels and seasonal variations in their distribution. The claim that seasonal variations can be measured through one visit per year may be assumed to be a lapse in formulation, but it may also suggest that the issue has not been thought through. It can be imagined that the between-year variation is linked to sea-bird foraging strategy or some other biological or physical factor. Such background data should be developed so that it will be possible to distinguish any effects of the construction. The Swedish Institute for the Marine Environment considers that undisturbed migration and foraging for sea-birds must be ensured. An important element in this work is establishing the seasonal variation in distribution of the blue mussel, which is so important for foraging, before construction begins. This knowledge is an important basis for being able to detect effects of the construction work. Mussels on bridge piers and effects on the plankton community Experience from previous construction of wind-power foundations and bridge piers, for example at the Öresund Bridge and the Great Belt Bridge, suggests that any bridge piers in the Fehmarn Belt may have dense populations of blue mussels. The filtering activity of the mussels reduces the quantity of phytoplankton and therefore also the quantity of nutrients in the water mass. Large-scale effects cannot be expected in view of the fact the surface of the potentially mussel-bearing bridge piers is small compared with the space between the piers. Increasing interest in biomanipulation as a tool for improving water quality, however, justifies attempting to make the surface more effective for the production of blue mussels adjacent to the bridge piers at pilot scale. The studies of the plankton community and of water quality that will be nevertheless be performed could therefore be adapted so that any effects of mussel filtration on the plankton community and therefore on the quantity of nutrients in the water on both sides of the bridge can be measured. The Swedish Institute for the Marine Environment proposes that the measurement programmes for plankton community and nutrients should be designed so that any positive effects of the mussel community in the form of

5 reduced nutrient levels in the water can be measured. General comments on study methodology and ways of detecting changes with the programmes for study of benthic flora and fauna as an example The studies are divided into "Baseline" and "Planned assessments [of impacts]". In purely general terms, these studies are described relatively briefly. In addition, the two elements should be linked more clearly so that information from the former can be explicitly used in the latter. This is in order to increase the opportunities for follow-up and to make optimal use of the available resources. With regard to the "baseline" studies, reference is made to the "MESH guidelines", but as these contain a number of different methods for mapping with fundamentally different points of departure (for example "top-down" classification and predictive modelling), this information is not of great assistance. This needs to be clarified. Another important matter with regard to the "baseline" study is that it must be apparent what precision can be expected from the envisaged study. Given the planned sampling, how well will it be possible to estimate the biomass of benthic fauna, algal coverage and so on? Clear information on these issues is crucial in enabling a position to be taken on whether these "baseline" studies are sufficiently good. There are similar problems with regard to "impact assessment". It is not apparent what effect sizes can be expected to be discovered with acceptable statistical significance, given the planned studies. With what probability can a 5, 10 or 50% reduction in biomass or any other variable be discovered? Acceptable statistical significance requires, on the one hand, having knowledge of natural variation and on the other defining a sampling design, analytical model and specific tests. These are relatively advanced exercises. It must, however, be possible to require a thorough analysis in a project of this importance. Study and analysis methodologies in this field should also be coordinated as far as possible with those used in previous construction projects such as the Öresund Fixed Link and the Great Belt Fixed Link. It is then possible to compare the results, benefit from previous experience and facilitate future meta-analyses to achieve overall understanding of general processes related to this type of construction. The Swedish Institute for the Marine Environment considers that to gather more generally applicable knowledge of environmental effects in offshore construction projects, study and analysis methodology has to be coordinated

6 both within the Fehmarn Belt project and between this project and previous studies in connection with similar projects. Effective follow-up of changes in biological and other variables must also be ensured, through well-defined precision in the estimation of these combined with indications of what effect sizes it is desirable to be able to detect. References Hammar L, Magnusson M, Rosenberg R, Granmo Å (2009), Miljöeffekter vid muddring och dumpning (Enviromental effects in dredging and dumping). Report No. 5999, Marine Monitoring AB, 2009 Svedäng H, Andre C, Jonsson P, Elfman M, Limburg KE (2010), Migratory behaviour and otolith chemistry suggest fine-scale sub-population structure within a genetically homogenous Atlantic Cod population. Environ Biol Fish DOI /s y The individuals below has supplied information that has been incorporated into the text: Bertil Håkansson Swedish Meteorological and Hydrological Institute Lasse Johansson Vattenfall (Worked in connection with the Öresund Fixed Link on water transport issues) Catherine LeGrande Kalmar Sound Laboratory, Linnaeus University Mats Lindegarth Swedish Institute for the Marine Environment Henrik Svedäng Swedish Institute for the Marine Environment Stefan Tobiasson Swedish Institute for the Marine Environment Jonas Nilsson Swedish Institute for the Marine Environment Roland Engkvist Swedish Institute for the Marine Environment