Large-scale Environmental Effects and Ecological Processes in the Baltic Sea Research Programme for the Period 1990—1995 and Background Documents Large-scale Environmental Effects and Ecological Processes in the Baltic Sea Research Programme for the Period 1990-1995 and Background Documents Fredrik Wulff (project leader and editor) Lennart Balk Gunnar Bergvall Åke Hagström Ingrid Jansson (secretary) Per Larsson Lars Rahm Contents INTRODUCTION 5 BACKGROUND DOCUMENTS 9 /. Modelling the biogeochemkal cycles of the Baltic Sea 9 Wulff. F.. A Sligebrandt. A 2. Meteorological forcing functions 19 Omsttrdt. A., (liistafsson. S.. A Mfuller. L 3. Loading related to meteorology 27 (inmat. I. 4. Loading related to hydrology and land use 49 Bergström. S 5. Trend analysis and source division of the load of eutrophying substances 61 (irimvall. A ft. Loading related to the exchange between the coastal zone and the open sea 75 Jansson, H-O.. A Engqvist. A 7. Organic pollutants, load and critical processes 95 Järnmark. C., Larsson. P.. Broman. I).. Näf. C A Lexén, K S. Critical processes in transformation of nitrogen and phosphorus in the pelagic ecosystem 123 Hagström. A., Norrman. B., A Horrigan, S 'A Total amounts of critical compounds in the sediments and processes relating to sediment-water exchange 145 Koop. K 10. Food web analysis of the Baltic ecosystem 167 l-llmgren, H.. Aneer. (i., A Hansson, S 11. Tota] amounts of nutrients in the watermass and interpolation routines 187 Rahm, 1... A Wulff, f- 12. A dispersion model for the Baltic Sea 205 Ciidhagen, I, /.?. A database and its tools 217 Wulff. E. A Rahm. I, INTRODUCTION Background regulate the concentrations and distributions of these substances should then be combined with these budgets in models of the biogcochcmical During recent decades, large-scale effects of cycles that can be used for prognoses of the future pollution on the entire seas surrounding Sweden have become apparent. The prevalence of anoxic development at different levels of loading. deep basins, the disappearance of the large popu- lation of gray seals in the Baltic and toxic phylo- Ecological risk assessment and evaluations of planklon blooms in the Kattcgat-Skagcrrak are ail the overall consequences will then be initiated and examples ot phenomena governed by large-scale carried out with the aid of these prognoses. Scien- processes. Marine resources, like fish for consump- tifically motivated measures can then be taken. tion are also endangered due to overall high levels of toxic substances and overfishing. II we can achive these aims, we will have created forceful arguments which can be used in international com entions. The present state of the Most studies have so far been concentrated Baltic Sea and its endangered future makes it nec- on local recipients in the coastal /ones and our essary to set high standards for this programme. understanding of the factors controlling large-scale The research strategy li >r this project area is formu- effects are limited. It is now obvious that these lated with the insight that models comprise an effects arise as a result of a complex interplay important and necessary but far from infallablc between loading of pollutants from all Ihe sur- instrument. However, budget and model calcula- rounding countries and biogeochcmical. hydrologi- tions is »superior way to formalize and lest knowl- c.il and ecological mechanisms. I^irge-sc.ile. inter- edge about a complt. \ ecological system. disciplinary effort., on an international level are noxv needed in order to understand and remedy these effects. The Swedish Environmental Protec- tion Agency (SNV) has therefore initiated a new- research project area, motivated by the need to Programme structure understand large-scale environmental changes occuring in the Baltic Sea . In the plannini; \<\ this programme some Swedish scicnii: is familiar with the tasks were asked The objective of this programme is to to specify the different research objectives. The re- stregthen the scientific base for interna- sults from these studies are presented in 13 back- tional negotiations concerning the pro- ground documents presented below. The common tection of our marine environment. objectives lor all these tasks have been: Assessments show that both eulrophying and Describe state of the art and current ac- toxic substances are increasing in the Baltic ami tivities relevant ft >r the Hallie Sea. measures must be prescribed to reduce the loads to levels where these trends are reversed. At the same Describe infomuition needed in terms of time, the costs of different measures should be nen research, evaluation of existing data weighted up against the results achieved Demands and as dala from other research and moni- on strong arguments increase when international toring programmes. measures need to be motivated. F.s;ahlish the necessary national and in- Budget calculations of the critical substances ternational contact* needed for this pro- should be the first step toward such considerations. gramme and suggest specific projects. Descriptions of large-scale critical processes which In order to optimize resources nn ecological 2 - Coastal-offshore interactions important large scale questions, only substances which arc well defined chemically and ecologically Most pollutants initially enters Ihe coastal and have a high priority as dangerous 10 the Baltic /one and even if we can quantitatively estimate environment, are studied. Thus, the project area these amounts.»»: must also understand how much lotuses on cutrophying substances (nitrogen, of these that eventually are incorporated into the phosphorus, silicate, organic material; ind on a overall biogeochemical cycles of the Baltic. lew toxic substances which, like nutrients, aie pos- Docs the coast.d /one act as a filler or an sible to model (PCB. Lindane. PAH). additional source for pollutants' L.ind rise and erosion of shallow sediments, resuspension and The aim of the project is not to chemically transports of organic and inorganic particles are identity yet unknown toxic substances, nor to de- some processes of great importance as well as the velop new ecotoxicological effect-tests. The proj- understanding of hydrodynamic and biological trans- ect should not study coastal recipients or effect of port processes. The relative importance of these pollutants if they are of only local interest. In processes are likely to vary regionally, i.e. between Sweden, such studies have already a high priority the open shallow coast in the southeastern Baltic within several other research programmes and are and the extensive archipelagoes further north. It is also followed in national monitoring programmes. important that these studies are made in such a way that trrj quantitative importance of the entire coastal The specific research objectives can be grouped zones of the Baltic basins can be estimated (Chap- into five major parts: ter 6). 1 - The load of nutrients and toxic 3 - Nutrients and toxic substances substances in the Baltic What quantities of eutrophying and toxic How large amounts of eutrophying and toxic substances are discharged into the Baltic Sea? Which substances are there in the ecosystem? How much are the transport mechanisms? What importance is there in the water mass, in the sediments, in the do the different sources have'.' These topics are dis- biota? cussed in Chapters 2-7. In order lo set up budgets, construct models Present calculations show that nearly a quar- and make predictions it is important that total ter of the nitrogen input to the Baltic Sea is in the amounts are compiled for all components in the lorn of precipitation (Chapter 3). The contribu- ecosystem of the Baltic £ea and Kattegat. As a first tion of toxic substances from the atmosphere, as step contents in the water phase (soluble and sus- well as from most other sources, is inadequately pended) and in the sediment have to be deter- known (Chapter 7). mined (Chapter'), 11). At another stage a more de- tailed division should be made. How much of the Weather (precipitation, temperature) affects substances are there in detritus, plankton, bottom to a large degree the supply of nutrients between fauna, fish etc (Chapter 10). For organic toxic years as well as seasonally. It is essential to relate substances, new information from most compo- pollutant to sources in order to evaluate the effi- nents of the ecosystem is required (Chapter 7). ciency of various actions to reduce t he load (Chap ter 5). The effects in terms of inputs lo the marine It is important th.it measurements of concen- environment will also vary in relation to character- tration; are done in such a way that the total istics of the drainage basin. Models which describe amount can he calculated (Chapter 11). Fo. nutri- how the supply depends on different types ol sources, ents, a method has been developed using measured ground characteristics, hydrology and meteorology concentrations from a large number ol stations and are therefore essential (Chapter 1 and 4). the corresponding volume estimations. While com- prehensive data materials for nutrients alreiidy exists, Thus there arc uncertanilies in estimating the our knowledge of dissolved and suspended materi- importance of the various forms of deposition, the als, sediment and biota is very limited, both where geographical differences as well as the meteoro- eutrophying substances and toxic substances arc logical mechanisms. In order to develop and verily concerned. modds it is of grea' importance that ihe temporal variations of the loading are described. 4 - Critical processes of carbon, several nut-ients ami possibly, toxic substances limits the resolution in terms of the Which mechanisms and processes are essen- number of compartments .ir.u in time and space. At tial to understa-J and explain the observed distri- the s;itr.e ti.nc. the models must take into account bution of criticj! substances in time and »pace? variables and critical pro-vsse* with a resolution that makes it possible to u.rierstanu and model Assimilaiu .