Measures and Their Implementation 1 Nitrogen controls are essential

The previous expert evaluation of eutrophication in Swedish seas (Boesch et al. 2006) covered the nation’s marine environments, but focused heavily on the Baltic Sea and the coastal environments of the east coast, particularly around Stockholm. The west coast seas and coastal environments were only briefly covered. That panel was unable to resolve the ongoing debate in Sweden regarding the efficacy of controlling nitrogen versus phosphorus inputs to reduce eutrophication. While both the limnologists and oceanographers on the panel could agree that more effort was needed to control phosphorus inputs, the former members held the position that the brackish Baltic ecosystem behaved much like many freshwater lakes in a way that made reduction of inputs of nitrogen ineffective or worse, counterproductive. They posited that whenever nitrogen concentrations were reduced sufficient to limit phytoplantonic growth but light and phosphorus were in sufficient supply, N2-

fixing cyanobacteria would proliferate and alleviate the nitrogen shortage. The oceanographers, on the other hand, were more familiar with estuarine and marine waters where phosphorus is remineralized, nitrogen often depleted and limiting, and limitation by either nutrient can occur over space and time scales. The

oceanographers found evidence of such joint or alternating limitation in the annual dynamics of production in the Baltic Proper and in the response of coastal waters around Stockholm to reductions in phosphorus and nitrogen point sources. Shortly after that evaluation, a multinational group of Baltic scientists published a synthesis that explained how elevated levels of both nitrogen, fueling the spring blooms and hypoxia, and phosphorus, remobilized from internal loads to support blooms of N2-fixing cyanobacteria during the summer, both played a role (Vahtera

et al. 2007). Controls of both nutrients are required, they argued, in agreement with the oceanographers. The SEPA (2006) considered the expert evaluation as well as other evidence in concluding that, although greater emphasis on phosphorus reductions was required, efforts to reverse eutrophication in the Baltic require both nitrogen and phosphorus reductions. The P versus N debate continues, as

exemplified by the recent publication by authors including the same limnologists participating in the 2005 expert evaluation arguing for a phosphorus-only control approach in lakes and even in coastal waters and citing that evaluation to support their case (Schindler et al. 2008).

The earlier expert evaluation panel (Boesch et al. 2006) did, however, conclude unambiguously that reduction of nitrogen inputs to the waters of the Swedish west coast was required to address eutrophication problems there as there were no apparent risks of N2-fixing cyanobacterial blooms to alleviate nitrogen deficiency.

The present evaluation reaffirms that conclusion and provides more detailed analysis of the spatio-temporal interplay of the two nutrients and an explanation of why N2-fixing cyanobacteria are not prevalent in the west coast seas and not likely

to become so if nitrogen levels decline.

6.2.2. Phosphorus reductions produce local benefits

At the same time, the earlier evaluation (Boesch et al. 2006) noted that reductions of phosphorus inputs would also have positive results in west coast waters because of the presently high levels of anthropogenic loading of both nutrients, but only if accompanied by nitrogen reductions. The present evaluation expands on that conclusion by considering phosphorus limitation seasonally and in the vicinity of nitrogen-rich riverine effluents. This explains why phosphorus removal in sewage treatment works discharging to the Göta Älv estuary produce local water quality and ecological benefits, while nitrogen removal would produce no apparent local benefits, but modest distant benefits (Erlandsson and Johannesson 2005; Isæus et al. 2005, Garde et al. 2008). By the same token, continued efforts to constrain or reduce point sources of phosphorus and improve poorly performing household waste treatment systems, and the recent discontinuance of phosphate-based

detergents in Sweden would be expected to result in localized improvements within the coastal zone, but are unlikely to result in greater phosphorus limitation in the open Kattegat or Skagerrak.

6.2.3. Greater reductions of agricultural and atmospheric loads are needed

With very substantial reductions in phosphorus and nitrogen loads from Swedish sewage treatment works having been achieved, most of the remaining reductions required to achieve the Zero Eutrophication objective and its interim targets must come from diffuse land-based sources, particularly agriculture, and atmospheric deposition of nitrogen (Table 5.1, SEPA 2007). Assessment of the effectiveness of the efforts to control these sources is beyond the scope of this evaluation, however it is worthwhile to note that while the inputs of phosphorus fertilizers have declined greatly the use of nitrogen fertilizers is as intense on a per-hectare basis as it was in the 1970s. Most of the decline in nitrogen leaching in agriculture has been due to a contraction in the area of arable land and the agricultural nitrogen surplus (the nitrogen applied in fertilizers and manure less the nitrogen removed in crops) averages 38% (Bernes 2005). This suggests that greater reductions in the nitrogen

leaching from agricultural lands are possible and, in fact, anticipated as a result of both implementation of control measures and changes in the global agricultural economy (SEPA 2007). The SEPA lists an array of proposals for further measures and controls in agriculture: revise the agricultural action programme, reduce soil cultivation, make permanent or increase area used for catch crops, establish 100% of the land in sensitive areas as grassland, establish riparian strips for erosion- sensitive land, increase regionalization of wetland support, use ponds as

phosphorus traps, lime filter drains, regulate drainage, and reduce the phosphorus content of animal feedstuffs. Further reductions in atmospheric emissions of ammonia and nitrogen oxides are anticipated and more aggressive European actions to reduce nitrogen oxide emissions are under negotiation (SEPA 2007).

6.2.4. Multi-national cooperation is required

A significant portion of anthropogenic nutrients that affect the Kattegat and Skagerrak do not originate from Sweden but are transported by currents and outflows from the lower Baltic Sea, from Denmark through the Belt Seas and across the Kattegat, and from the catchments of the large rivers of western Europe, and via atmospheric transport from over an even larger footprint. Clearly Sweden’s actions alone are insufficient to achieve the load reductions and good

environmental status required to meet the Zero Eutrophication objective. Sweden is party to two important regional marine conventions, OSPAR and HELCOM, which provide mechanisms to engage other nations in the necessary cooperative efforts to reduce nutrient inputs. It is in Sweden’s best interest to continue its leadership role as an early adopter of effective nutrient controls and in scientific research and assessment (e.g. the Baltic NEST decision-making tool). Multiple directives from the European Union, including the Nitrate Directive, Habitat Directive, Water Framework Directive and the Marine Strategy Directive, provide both mandates and impetus to achieve the Zero Eutrophication objective. However, it is important that Sweden takes a proactive role in the implementation of these directives to ensure common European standards for achieving ecological quality objectives that are consistent with the national Zero Eutrophication objective.

6.3. Integration of Monitoring, Modeling and