Mussel farming as a nutrient reduction measure in the Baltic Sea: consideration of nutrient biogeochemical cycles

Nutrient loads from the land to the sea must be reduced to combat coastal eutrophication. It has been suggested that further mitigation efforts are needed in the brackish Baltic Sea to decrease nutrients, especially in eutrophic coastal areas. Mussel farming is a potential measure to remove nutrients directly from the sea. Mussels consume phytoplankton containing nitrogen (N) and phosphorus (P); when the mussels are harvested these nutrients are removed from the aquatic system. However, sedimentation of organic material in faeces and pseudo-faeces below a mussel farm consumes oxygen and can lead to hypoxic or even anoxic sediments causing an increased sediment release of ammonium and phosphate. Moreover, N losses from denitrification can be reduced due to low oxygen and reduced numbers of bioturbating organisms. To reveal if mussel farming is a cost-effective mitigation measure in the Baltic Sea the potential for enhanced sediment nutrient release must be assessed.     

Nutrient budgets for European seas: a measure of the effectiveness of nutrient reduction policies

Socio-economic development in Europe has exerted increasing pressure on the marine environment. Eutrophication, caused by nutrient enrichment, is evident in regions of all European seas. Its severity varies but has, in places, adversely impacted socio-economic activities. This paper aims to evaluate the effectiveness of recently adopted policies to reduce anthropogenic nutrient inputs to European seas. Nitrogen and phosphorus budgets were constructed for three different periods (prior to severe eutrophication, during severe eutrophication and contemporary) to capture changes in the relative importance of different nutrient sources in four European seas suffering from eutrophication (Baltic Proper, coastal North Sea, Northern Adriatic and North-Western Black Sea Shelf). Policy success is evident for point sources, notably for P in the Baltic and North Seas, but reduction of diffuse sources has been more problematic.     

A simple method for confidence rating of eutrophication status classifications

We report the development of a methodology for assessing confidence in ecological status classifications. The method presented here can be considered as a secondary assessment, supporting the primary assessment of eutrophication or ecological status. The confidence assessment is based on scoring the quality of the indicators on which the primary assessment is made. This represents a first step towards linking status classification with information regarding their accuracy and precision. Applied to an existing data set used for assessment of eutrophication status of the Baltic Sea (including the Kattegat and Danish Straits) we demonstrate that confidence in the assessment is Good or High in 149 out of 189 areas assessed (79%). Contrary to our expectations, assessments of the open parts of the Baltic Sea have a higher confidence than assessments of coastal waters. We also find that in open waters of the Baltic Sea, some biological indicators have a higher confidence than indicators representing physical-chemical conditions. In coastal waters, phytoplankton, submerged aquatic vegetation and indicators of physical-chemical conditions have a higher confidence than indicators of the quality of benthic invertebrate communities. Our analyses also show that the perceived weaknesses of eutrophication assessments are due more to Low confidence in reference conditions and acceptable deviations, rather than in the monitoring data.     

Oxygen depletion off the Changjiang (Yangtze River) Estuary

In a survey on the Yellow Sea and the East China Sea on August 20-30 of 1999, we found a hypoxic zone (<2 mg/L) of 13700 km² with an average thickness of 20m at the bottom of the Changjiang (Yangtze River) Estuary, with an oxygen minimum value of 1 mg/L. The extension of the dissolved oxygen deficiency extended to the 100m isobath in a southeastward direction along the bottom of the continental shelf of the East China Sea. During the last two decades, the minimum dissolved oxygen values in the low oxygen region of the Changjiang Estuary have decreased from 2.85 mg/L to 1 mg/L. In the hypoxic zone, the apparent oxygen utilization (AOU) was 5.8 mg/L and the total oxygen depletion approximately 1.59 × 10⁶t. The strong halocline above the hypoxic zone, as a result of affluent water from the Changjiang, Taiwan Warm Current (TWC), and the high concentrations of particle organic carbon (POC) and nitrogen (PON) are the major factors causing the formation of the hypoxic zone. The POC: PON ratios and nutrient concentration distributions in the hypoxic zone suggest that the oxygen deficiency in the bottom water during the summer in the East China Sea off the Changjiang is the result of organic carbon production enhanced by nutrients from the Changjiang and fluvial organic matter input, followed by a shift in regeneration of nutrients in the East China Sea.     

HELCOM Baltic Sea Action Plan - A regional programme of measures for the marine environment based on the Ecosystem Approach

The Helsinki Commission (HELCOM) Baltic Sea Action Plan, adopted by the coastal countries of the Baltic Sea and the European Community in November 2007, is a regional intergovernmental programme of measures for the protection and management of the marine environment explicitly based on the Ecosystem Approach. The Action Plan is structured around a set of Ecological Objectives used to define indicators and targets, including effect-based nutrient input ceilings, and to monitor implementation. The Action Plan strongly links Baltic marine environmental concerns to important socio-economic fields such as agriculture and fisheries and promotes cross-sectoral tools including marine spatial planning. Due to complementarities with the European Union (EU) Marine Strategy Framework Directive, the Action Plan is in essence a pilot for this process without neglecting the important role of the Russian Federation - the only Baltic coastal country not a member of the EU.     

Eutrophication assessment of the Baltic Sea Protected Areas by available data and GIS technologies

Concerning increased degradation of marine ecosystems, there is a great political and institutional demand for an array of different tools to restore a good environmental status. Thereby, eutrophication is acknowledged as one of the major human induced stressors which has to be monitored and reduced. The present study concentrates on an assessment of the eutrophication status of the Baltic Sea Protected Areas by use of available data and GIS technologies. Two geodata layers were used for analysis: (1) a map on the eutrophication status of the Baltic Sea generated by the Helsinki Commission applying the HELCOM Eutrophication Assessment Tool (HEAT), and (2) modelled data on atmospheric nitrogen deposition made available by the European Monitoring and Evaluation Programme (EMEP). The results yielded comprehensive and conclusive data indicating that most of the BSPAs may be classified as being ‘affected by eutrophication’ and underlining the need to decrease the overall emissions of nutrients.     

Eutrophication assessment of the Baltic Sea Protected Areas by available data and GIS technologies

Concerning increased degradation of marine ecosystems, there is a great political and institutional demand for an array of different tools to restore a good environmental status. Thereby, eutrophication is acknowledged as one of the major human induced stressors which has to be monitored and reduced. The present study concentrates on an assessment of the eutrophication status of the Baltic Sea Protected Areas by use of available data and GIS technologies. Two geodata layers were used for analysis: (1) a map on the eutrophication status of the Baltic Sea generated by the Helsinki Commission applying the HELCOM Eutrophication Assessment Tool (HEAT), and (2) modelled data on atmospheric nitrogen deposition made available by the European Monitoring and Evaluation Programme (EMEP). The results yielded comprehensive and conclusive data indicating that most of the BSPAs may be classified as being 'affected by eutrophication' and underlining the need to decrease the overall emissions of nutrients.     

Cultural eutrophication of shallow coastal waters: Coupling changing anthropogenic nutrient inputs to regional management approaches

Coastal waters comprise only about 15% of the world's ocean area, yet account for nearly half of its primary and secondary production (Wollast 1991). This disparity can in part be traced to anthropogenic nutrient, specifically nitrogen (N), loading. Regionally, N-sensitive coastal waters are experiencing unprecedented nutrient-driven eutophication, deteriorating water quality (i.e. hypoxia, anoxia, toxicity), habitat loss and declines in desirable fish stocks and yields. In most coastal regions externally-supplied “new” nutrient inputs are growing, diversifying and changing as a result of urbanization, industrial and agricultural development. In some cases (e.g. Eastern Europe), declining economic condition shave led to a reversal of this scenario. A need exists to identify key nutrient sources (and changes therein) supporting eutrophication and its socio-economic consequences. While we are addressing and managing terrestrial (i.e. point and non-point source runoff) “new” nutrient inputs, key “out of sight out of mind” anthropogenic nutrient sources and their effects on eutrophication remain poorly understood and managed. These include atmospheric deposition and groundwater, which can account for as much as half the “new” N entering North American (U.S. Atlantic East Coast) and European (Baltic Sea) coastal waters. Here, I will examine these emerging nutrient sources and their roles in shallow coastal biogeochemical and trophodynamics alterations. Technological and conceptual tools and approaches aimed at improving our functional understanding of these and other “new” nutrient-eutrophication interactions are discussed.     

Polycyclic aromatic hydrocarbons in water and sediment of the Baltic Sea

Between 1992 and 1994, the distribution of 15 polycyclic aromatic hydrocarbons (PAHs) was investigated in seawater and surface sediments of the Baltic Sea. The analysis of PAHs in seawater is very difficult due to the low concentration. High separation capability is required. A method for analysing very low concentrations of PAHs is presented. The method is based on the high-performance liquid chromatography (HPLC) with fluorescence detection. The concentrations of PAHs in seawater are discussed in relation to water depth. A seasonal variation of PAHs in seawater was observed, with lowest concentrations occurring in summer and generally higher concentrations occurring in November. According to the regional distribution, elevated concentrations of PAHs were found in coastal regions of the Baltic Sea. The regional distribution of PAHs in surface sediments of the Belt Sea and the Arkona Basin were also investigated. The relationship between the content of PAHs and the percentage of total organic carbon in sediments is discussed.     

南亚热带典型调水型水库—广东大镜山水库的富营养化特征分析

调水型水库是一种以抽水入库为主要来水水源的水体,是沿海地区重要的供水水源地.为了解这类水库的富营养化特点,于2005年全年每月2次对地处我国南亚热带地区(广东珠海市)的大镜山水库进行采样和监测.监测和测定指标主要包括氮、磷营养盐浓度、水温、透明度及叶绿素a浓度等,结合水库水文数据对水库富营养化特征和主要的影响因素进行分析.结果表明,2005年,大镜山水库的富营养化状态TSI_M指数在45-53之间,水库处于中富营养状态,多数时间处于富营养状态.水体富营养化主要参数表现出明显的季节变化,即叶绿素a浓度和富营养化状态指数在早春和晚秋出现两个峰值,明显地与温带富营养化水体在夏季出现单个峰值的特征不同.调水入库增加了水库营养盐负荷的同时,也在很大程度上影响了水库水动力学过程,与夏季的集中强降雨一起成为影响该水库富营养化的关键因素,这些因素改变了浮游植物群落对营养盐的直接响应,导致叶绿素a浓度与总磷、总氮浓度之间呈弱相关关系,降水和调水量在时间上相对配置重要性决定了叶绿素a浓度与营养盐浓度的关系.     

Changes in the seasonal cycles of inorganic nutrients in the coastal zone of the southeastern North Sea from 1960 to 1997: effects of eutrophication and sensitivity to meteoclimatic factors

A long-term analysis of seasonal cycles of inorganic nutrients by means of a seasonal index is presented for the German Bight and the southern Wadden Sea (SE North Sea). Multivariate analysis for the German Bight data series revealed dependence of ammonium and phosphate index time series on dissolved inorganic nitrogen concentrations and riverine nutrient loads. Both indices are assumed to reflect seasonal dynamics of remineralisation processes associated with increased supply of organic matter. Temporal analysis revealed breaks in nutrient dynamics in 1970/1972 and 1979/1980. After 1970/1972, an unprecedented increase in the summer concentrations of mineralisation endproducts with correspondingly low index values were observed, which further declined after 1979/1980. Further breaks for Wadden Sea data series were identified in 1985 and 1988/1989. The indicative value of the temporal breaks with respect to eutrophication is discussed against the background of changes in meteoclimatic factors and local environmental conditions. Collated information on eutrophication effects was consistent with the observed breaks. It is suggested that the break in 1970/1972 in the German Bight was the first sign of ecosystem response to eutrophication in the SE North Sea.     

The Odra Estuary as a Filter and Transformation Area

The Odra Estuary is one of the most polluted coastal waters of the southern Baltic. To investigate how and whether the estuary acts as a filter and transformation area for the fluviogenic material, different models were developed and an intensive monitoring programme was carried out. Summarizing different methodological approaches, it could be shown that the total system filter capacity reaches 2...5% for nutrients and 10...15% for some heavy metals related to the current mean annual input. In the western part of the estuary, the retention is more important and amounts to 10...40% of the annual nutrient yield. Carbon flux studies revealed that both a reduction of the inputs and more internal and external nutrient sinks are needed to reverse the anthropogenic eutrophication process.     

Seasonal nitrogen and phosphorus dynamics during benthic clam and suspended mussel cultivation

Effects of suspended mussel and infaunal clam cultivation on sediment characteristics, and benthic organic and inorganic nitrogen and phosphorus fluxes were compared in a shallow coastal lagoon. The two species had different impacts on sediment features, but both created “hotspots” of nutrient fluxes with annual N and P regeneration rates being 4.9 and 13.5 (mussel) and 4.5 and 14.9 (clams) fold greater than those of unfarmed control sediments. Mussel farming also caused considerable nutrient regeneration within the water column with the mussel ropes contributing ∼25% of total inorganic N and P production and at times dominating the sediments (e.g. 95% of SRP production in summer and 45% of DIN production in winter). Such nutrient regeneration rates seriously question the proposal that suspension-feeding bivalves act as a eutrophication buffer, especially during summer when nutrient regeneration rates are maximal, but other nutrient sources (freshwater run-off and unfarmed sediments) are at their lowest.     

Exploitation of biological resources of the Baltic Sea by estonia in 1928–1995

The main exploitable biological resources in the Estonian zone of the Baltic Sea are fish stocks. Fishes of marine origin constitute the main bulk (on the average 91%) of catches. Some freshwater and migratory fishes, having usually only marginal role in the total weight of fish landings, are of special importance for local fishermen in certain regions. Other living resources — red algae and seals-have been exploited in rather small amounts.The main factors having controlled changes in the condition of fish stocks and catches are natural conditions, marine pollution, eutrophication and exploitation rate.     

Eutrophication—The future marine coastal nuisance?

Increased inputs of nutrients to marine coastal areas over the last decades have created a basis for eutrophication of the waters surrounding Sweden. In combination with relatively low water exchange in these vertically stratified and almost non-tidal waters, local and regional effects of increased macro-algal biomass, and decreased oxygen concentrations in bottom water leading to mortalities of benthic animals and decreased fish catches have at times been observed. The effects were first noted in the Baltic, but are now obvious also in Swedish and Danish coastal areas in the Kattegat and the Belt Sea. Similar symptoms have recently also been recorded off the Danish North Sea coast. Other shallow coastal and shelf areas, where stratification occurs, can be regarded as potentially eutrophic risk areas.     

Eutrophication,risk management and sustainability. The perceptions of different stakeholders in the northern Baltic Sea

The environmental condition of the Baltic Sea is not only of concern for natural scientists. The awareness of the deteriorating state of the ecosystem has become an issue of interdisciplinary interest, and the amount of organizations with the marine environment and ecosystem health on the agenda is large. To present holistic and sustainable solutions and results of the actions taken, an active cooperation between all stakeholder groups and levels are needed. How different stakeholders in the northern Baltic Sea perceive the structures and assessments of the eutrophication were analyzed by semi-structured interviews with 17 stakeholders representing authorities, scientists, NGOs and national interest organizations. The focus was the view of the governance structures, risk assessment, management and communication. There was an overall consensus that eutrophication is a serious problem. Still variations in the opinions both within and between the stakeholder groups were seen. The scientists were most divergent from the rest.     

Finnish strategies for reduction and control of effluents to the marine environment--examples from agriculture,municipalities and industry

The most serious environmental problem encountered in the Baltic Sea is eutrophication. Finland finalised in spring 2002 its national Programme for the Protection of the Baltic Sea. The programme contains more than 30 measures for improving the state of the Baltic Sea and protecting the marine environment. Total national investments during the next 10-15 years will amount to EUR 300-370 million. The highest annual cost will be environmental support to agriculture. The bulk of the rest of the money will be used for nitrogen purification of municipal wastewater, improvement of water protection in dispersed settlement areas, and investments to improve maritime safety and decrease the risks of oil spills.     

Plankton of the Baltic estuarine ecosystems with emphasis on Neva Estuary: a review of present knowledge and research perspectives

Different levels of eutrophication and pollution in the Baltic coastal waters in general, and in estuaries particularly define variations in the buffering capacity of ecosystems of these important filter zones between rivers and the adjacent Baltic Proper. Phyto- and zooplankton in the estuaries form important components of the pelagic food webs that participate in producing and structuring the matter, energy, and information fluxes in the ecosystems. Due to salinity gradients, estuaries provide a large variety of aquatic habitats for native populations of marine, brackish and fresh water plankton species. Non-indigenous planktonic species that expand their bio-geographical range and invade the Baltic coastal ecosystems also find favourable environments, establish permanent populations there, and impact aboriginal ecosystems. The dynamics of abundance, species diversity, population structure, productivity of planktonic communities, and peculiarities of trophic interactions in different Baltic estuaries are influenced by a number of common environmental factors. Being measured on the unified basis and monitored, changes (or stability) of structural and functional parameters of plankton communities can serve as indicators of alterations to the ecosystems. Comparative analyses and quantitative estimates of long-term changes in phyto- and zooplankton can contribute to evaluation of functional response of Baltic coastal ecosystems to anthropogenic stress. Both theoretical (modeling) and empirical studies of interactions within plankton communities aimed at the assessment of the role of planktonic organisms in water quality regulation, and applicability of these data for the evaluation of the status of ecosystems and their management can be considered as major goals for the future investigations in Baltic estuaries.     

Nutrient source attribution: Quantitative typology distinction of active and legacy source contributions to waterborne loads

Distinction between active and legacy sources of nutrients is needed for effective reduction of waterborne nutrient loads and associated eutrophication. This study quantifies main typological differences in nutrient load behaviour versus water discharge for active and legacy sources. This quantitative typology is used for source attribution based on monitoring data for water discharge and concentrations of total nitrogen (TN) and total phosphorous (TP) from 37 catchments draining into the Baltic Sea along the coastline of Sweden over the period 2003–2013. Results indicate dominant legacy source contributions to the monitored loads of TN and TP in most (33 of the total 37) study catchments. Dominant active sources are indicated in 1 catchment for TN, and mixed sources are indicated in 3 catchments for TN, and 4 catchments for TP. The TN and TP concentration contributions are quantified to be overall higher from the legacy than the active sources. Legacy concentrations also correlate well with key indicators of human activity in the catchments, agricultural land share for TN (R² = 0.65) and population density for TP (R² = 0.56). Legacy-dominated nutrient concentrations also change more slowly than in catchments with dominant active or mixed sources. Various data-based results and indications converge in indicating legacy source contributions as largely dominant, mainly anthropogenic, and with near-zero average change trends in the present study of catchments draining into the Baltic Sea along the coastline of Sweden, as in other parts of the world. These convergent indications emphasize needs to identify and map the different types of sources in each catchment, and differentiate strategies and measures to target each source type for possible achievement of shorter- and longer-term goals of water quality improvement.