Internal Nutrient Fluxes Counteract Decreases in External Load: The Case of the Estuarial Eastern Gulf of Finland, Baltic Sea

Pitkänen, Heikki; Lehtoranta, Jouni; Räike, Antti

doi:10.1639/0044-7447(2001)030[0195:infcdi]2.0.co;2

Cited by 59 publications

(80 citation statements)

References 15 publications

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“…As shown in Figure 5, the MP group was significantly correlated with NH Several mechanisms may lead to high NH þ 4 -N concentration in the river in summer. First, it may be a result of atmospheric load (Pitka¨nen et al 2001). In the present study, the summer is the wet season, which would result in greater N inputs to the river.…”

Section: Discussionmentioning

confidence: 79%

Seasonal dynamics of phytoplankton functional groups and its relationship with the environment in river: a case study in northeast China

Yu¹,

Wu²,

Ma³

et al. 2012

Journal of Freshwater Ecology

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In this study, the concept of functional groups was applied for the first time to the seasonal dynamics of the phytoplankton community of Mudanjiang River (northeast China). The environmental variables as well as the phytoplankton communities were determined in 2007. The river showed strong seasonal fluctuations in water physical and chemical condition. A total of 11 phytoplankton functional groups (C, D, E, J, MP, P, T, T B , W1, X2 and Y) were identified that included 30 species. Groups C (Asterionella formosa and Cyclotella meneghiniana), MP (Cocconeis placentula, Cymatopleara solea, Diatoma vulgare, Ochromonas fragilis, Pinnularia major and Ulothrix variabilis), P (Fragilaria capucina, Fragilaris sp., Aulacoseira granulate and Aulacoseira granulate var. angustissima), T B (Aulacoseira varians and Navicula exigua, Navicula radiosa), X2 (Chlamydomonas sp.) and Y (Chroomonas acuta, Cryptomonas ovata, and Cryptomonas sp.) were the dominant groups during the study period. Mudanjiang River phytoplankton functional groups exhibited a noticeable seasonality in which group Y was predominant in the winter and spring associated with greater soluble reactive phosphorus availability, group MP in the summer associated with ammonium-nitrogen availability, and group P in autumn associated with greater transparency. This study underscores the usefulness of functional groups in studying phytoplankton dynamics in this river, in which phytoplankton dynamics can be significantly affected by tourism.

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Section: Discussionmentioning

confidence: 79%

Seasonal dynamics of phytoplankton functional groups and its relationship with the environment in river: a case study in northeast China

Yu¹,

Wu²,

Ma³

et al. 2012

Journal of Freshwater Ecology

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“…However, only 13 areas (2 open basins and 11 coastal sites) in the Baltic Sea are classified as "areas not affected by eutrophication", whereas 176 areas (15 open basins and 161 coastal sites) remain "areas affected by eutrophication" (HELCOM, 2009). Nutrient input from the sediments ("internal nutrient loading") is also a serious problem and more significant than terrestrial inputs to the Gulf of Finland (Pitkanen et al, 2001) and the Baltic proper (Viktorsson et al, 2013). In addition, projected climatic changes, which are stronger for the Baltic Sea than the global average (BACC, 2008), will affect both the freshwater balance and the seasonal extent of ice cover in the northern part of the Baltic.…”

Section: Open and Shelf Seasmentioning

confidence: 99%

Investigating hypoxia in aquatic environments: diverse approaches to addressing a complex phenomenon

et al. 2014

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Abstract. In this paper we provide an overview of new knowledge on oxygen depletion (hypoxia) and related phenomena in aquatic systems resulting from the EU-FP7 project HYPOX ("In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and landlocked water bodies", www.hypox.net). In view of the anticipated oxygen loss in aquatic systems due to eutrophication and climate change, HYPOX was set up to improve capacities to monitor hypoxia as well as to understand its causes and consequences.Temporal dynamics and spatial patterns of hypoxia were analyzed in field studies in various aquatic environments, including the Baltic Sea, the Black Sea, Scottish and Scandinavian fjords, Ionian Sea lagoons and embayments, and Swiss lakes. Examples of episodic and rapid (hours) occurrences of hypoxia, as well as seasonal changes in bottom-water oxygenation in stratified systems, are discussed. Geologically driven hypoxia caused by gas seepage is demonstrated. Using novel technologies, temporal and spatial patterns of watercolumn oxygenation, from basin-scale seasonal patterns to meter-scale sub-micromolar oxygen distributions, were resolved. Existing multidecadal monitoring data were used to demonstrate the imprint of climate change and eutrophication on long-term oxygen distributions. Organic and inorganic proxies were used to extend investigations on past oxygen conditions to centennial and even longer timescales that cannot be resolved by monitoring. The effects of hypoxia on faunal communities and biogeochemical processes were also addressed in the project. An investigation of benthic fauna is presented as an example of hypoxia-devastated benthic communities that slowly recover upon a reduction in eutrophication in a system where naturally occurring hypoxia overlaps with anthropogenic hypoxia. Biogeochemical investigations reveal that oxygen intrusions have a strong effect on the microbially mediated redox cycling of elements. Observations and modeling studies of the sediments demonstrate the effect of seasonally changing oxygen conditions on benthic mineralization pathways and fluxes. Data quality and access are crucial in hypoxia research. Technical issues are therefore also addressed, including the availability of suitable sensor technology to resolve the gradual changes in bottom-water oxygen in marine systems that can be expected as a result of climate change. Using cabled observatories as examples, we show how the benefit of continuous oxygen monitoring can be maximized by adopting proper quality control. Finally, we discuss strategies for state-of-the-art data archiving and dissemination in compliance with global standards, and how ocean observations can contribute to global earth observation attempts.

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“…Nutrient remobilisation from the sediment due to lower oxygen concentrations in the bottom water are often cited to contribute to ongoing oxygen decline (see e.g. Conley et al, 2002;Pitkänen et al, 2001). At BE, for example phosphate concentrations in the bottom water were elevated during periods of anoxia, but the general trend was significantly decreasing between 1980 and 2013.…”

Section: Observationsmentioning

confidence: 99%

Long-term trends at the Boknis Eck time series station (Baltic Sea), 1957–2013: does climate change counteract the decline in eutrophication?

et al. 2014

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Abstract. The Boknis Eck (BE) time series station, initiated in 1957, is one of the longest-operated time series stations worldwide. We present the first statistical evaluation of a data set of nine physical, chemical and biological parameters in the period of 1957-2013. In the past three to five decades, all of the measured parameters underwent significant long-term changes. Most striking is an ongoing decline in bottom water oxygen concentration, despite a significant decrease of nutrient and chlorophyll a concentrations. Temperature-enhanced oxygen consumption in the bottom water and a prolongation of the stratification period are discussed as possible reasons for the ongoing oxygen decline despite declining eutrophication. Observations at the BE station were compared with model output of the Kiel Baltic Sea Ice Ocean Model (BSIOM). Reproduced trends were in good agreement with observed trends for temperature and oxygen, but generally the oxygen concentration at the bottom has been overestimated.

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Internal Nutrient Fluxes Counteract Decreases in External Load: The Case of the Estuarial Eastern Gulf of Finland, Baltic Sea

Cited by 59 publications

References 15 publications

Seasonal dynamics of phytoplankton functional groups and its relationship with the environment in river: a case study in northeast China

Seasonal dynamics of phytoplankton functional groups and its relationship with the environment in river: a case study in northeast China

Investigating hypoxia in aquatic environments: diverse approaches to addressing a complex phenomenon

Long-term trends at the Boknis Eck time series station (Baltic Sea), 1957–2013: does climate change counteract the decline in eutrophication?

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