Silicon Retention in River Basins: Far-reaching Effects on Biogeochemistry and Aquatic Food Webs in Coastal Marine Environments

Humborg, Christoph; Conley, Daniel J.; Rahm, Lars; Wulff, Fredrik; Cociasu, Adriana; Ittekkot, V.

doi:10.1639/0044-7447(2000)029[0045:srirbf]2.0.co;2

Cited by 108 publications

(156 citation statements)

References 30 publications

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“…Some of these changes are driven by P availability, as the relative availabilities of N and P can select for domination by different primary producers. For example, high levels of P can encourage domination by some undesirable macro-algal species in the benthos (Conley 2000). Other changes are driven by Si availability, since Si is required by diatoms but not other types of phytoplankton.…”

Section: Planktonic Nitrogen Fixationmentioning

confidence: 99%

“…The loss of diatoms has a profound effect on energy flow through the food web, as diatoms are relatively high in food quality (Turner et al 1998). This shift may also favor harmful algal blooms (Smayda 1997;Conley 2000;Cloern 2001). Once Si is depleted, high levels of inorganic P may further promote harmful algal blooms, including Phaeocystis and many species of dinoflagellates, particularly when the N : P ratio is low (Glibert and Pitcher 2001;Cugier et al 2005).…”

Section: Planktonic Nitrogen Fixationmentioning

confidence: 99%

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Nitrogen as the limiting nutrient for eutrophication in coastal marine ecosystems: Evolving views over three decades

Howarth

Marino

2006

Limnology & Oceanography

1,156

731

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The first special volume of Limnology and Oceanography, published in 1972, focused on whether phosphorus (P) or carbon (C) is the major agent causing eutrophication in aquatic ecosystems. Only slight mention was made that estuaries may behave differently from lakes and that nitrogen (N) may cause eutrophication in estuaries. In the following decade, an understanding of eutrophication in estuaries proceeded in relative isolation from the community of scientists studying lakes. National water quality policy in the United States was directed almost solely toward P control for both lakes and estuaries, and similarly, European nations tended to focus on P control in lakes. Although bioassay data indicated N control of eutrophication in estuaries as early as the 1970s, this body of knowledge was treated with skepticism by many freshwater scientists and water-quality managers, because bioassay data in lakes often did not properly indicate the importance of P relative to C in those ecosystems. Hence, the bioassay data in estuaries had little influence on water-quality management. Over the past two decades, a strong consensus has evolved among the scientific community that N is the primary cause of eutrophication in many coastal ecosystems. The development of this consensus was based in part on data from whole-ecosystem studies and on a growing body of evidence that presented convincing mechanistic reasons why the controls of eutrophication in lakes and coastal marine ecosystems may differ. Even though N is probably the major cause of eutrophication in most coastal systems in the temperate zone, optimal management of coastal eutrophication suggests controlling both N and P, in part because P can limit primary production in some systems. In addition, excess P in estuaries can interact with the availability of N and silica (Si) to adversely affect ecological structure. Reduction of P to upstream freshwater ecosystems can also benefit coastal marine ecosystems through mechanisms such as increased Si fluxes.

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Section: Planktonic Nitrogen Fixationmentioning

confidence: 99%

Section: Planktonic Nitrogen Fixationmentioning

confidence: 99%

Nitrogen as the limiting nutrient for eutrophication in coastal marine ecosystems: Evolving views over three decades

Howarth

Marino

2006

Limnology & Oceanography

1,156

731

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“…Some consequences of altered discharge in rivers are subtle and interfere with the biogeochemical cycle and hence only become evident at long timescales [Friedl and Wüest, 2002]. Notably, damming might interfere physicobiogeochemically by causing (1) water temperature changes resulting from hydropower operations [Preece and Jones, 2002;Meier et al, 2003;Bartholow et al, 2005], (2) nutrient retention [Humborg et al, 2000;Friedl et al, 2004], and (3) hydrological pattern changes and reductions in suspended particle loads [Vörösmarty et al, 2003;Teodoru and Wehrli, 2005;McGinnis et al, 2006].…”

Section: Introductionmentioning

confidence: 99%

Effects of upstream hydropower operation on riverine particle transport and turbidity in downstream lakes

Finger

Schmid

Wüest

2006

Water Resources Research

131

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[1] Retention in upstream storage dams results in modified riverine water and particle discharge patterns. Particularly, suspended solids input and intrusion dynamics in downstream lakes are affected by dam operations. In a case study, size-dependent particle budgets for peri-alpine Lake Brienz (Switzerland), downstream of major hydropower installations, were determined for a recent 8-year period (1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)) and compared to hypothetical no-dam scenarios based on numerical simulations. For this purpose, current tributary particle loads, as well as lake-internal sedimentation and turbidity dynamics, were assessed with in situ measurements. The analysis shows that hydropower damming drastically diminishes particle fluxes and minimizes (short-term) peak discharges. Reductions of high-flow events substantially cut the number of deep intrusions increasing particle supply to the lake surface layer. Furthermore, these hydropower operations shift particle inputs from summer to winter. As a consequence, such peri-alpine lakes become more turbid during winter and less turbid during summer, influencing the seasonal light regime and subsequently the dynamics of phytoplankton growth.

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“…Agriculture residuals (NIXON, 1995) and sewage input in coastal environments (CARPENTER et al, 1998) are the main anthropogenic cause of water enrichment and the increase of phytoplankton biomass. The control of the freshwater flow (PETERSEN et al, 2008;DYNESIUS;NILSSON, 1994) and river damming (NIXON, 2003) often disrupt the spatial distribution, temporal patterns and community structure of phytoplankton by leading to changes in river-coast chemistry (HUMBORG et al, 2000). Thus, estuaries where human occupation is intense will benefit from monitoring programs that include the observation of phytoplankton dynamics.…”

Section: Introductionmentioning

confidence: 99%

Temporal variability of chlorophyll-a in the São Vicente estuary

et al. 2012

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A B S T R A C TEstuaries are extremely dynamic environments that are vulnerable to anthropogenic alterations. Thus, monitoring phytoplankton abundances and composition is an essential tool for the prediction of eutrophication and its effects on coastal ecosystems. Phytoplankton biomass, as chlorophyll-a, in the São Vicente estuary (Brazil) varies in response to tidal cycles and seasonal rainfall. Objectives. To present two datasets designed to assess the relationship between chlorophyll-a and changes in water turbidity driven by tide and rain. Methods. Weekly observations were made in the shallow embayment (February to September 2008; site 1) and observations recorded on alternate days (summer 2010, site 2). Results. At site 1, turbidity differed between high and low tides, but on most days was over 3000 RU, maintaining moderate chlorophyll-a levels (4 mg.m -3 ) and only two blooms developed during low turbidity. Site 2 mean turbidity was 1500 RU, nutrient level was higher during neap tides and phytoplankton blooms were mainly observed at the end of neap tides at 15-day intervals, dominated by chain-forming diatoms and occasionally flagellates and pennate diatoms. Conclusions. Taxonomic composition of the blooms was different and their frequency altered by events characterized by intense freshwater discharges from the Henry Borden Hydroelectric Dam (> 9*106.m 3 ), inhibiting phytoplankton accumulation during neap tide periods. R E S U M OEstuários são ambientes dinâmicos e susceptíveis a alterações antropogênicas. Nesses ambientes, torna-se imprescindível monitoramento do fitoplâncton na previsão da eutrofização e de seus efeitos para o ecossistema. No estuário de São Vicente (Brasil) a biomassa fitoplanctônica, como clorofila-a, varia sazonalmente em resposta às chuvas e marés. O presente estudo visa apresentar dois programas de monitoramento para detectar florações fitoplanctônicas em relação a turbidez da água guiada pelas marés e chuvas. Métodos. As observações foram semanais na porção rasa (Fevereiro a Setembro de 2008; área 1) e observações em dias alternados no canal (verão de 2010; área 2). Os resultados mostram que a área 1, turbidez acima de 3000 RU manteve níveis de clorofila-a médios (4 mg.m -3 ) e duas florações ocorreram apenas em baixa turbidez, sendo esta diferente entre marés alta e baixa. Na área 2, a turbidez manteve-se entre 1500 RU, os nutrientes foram maiores durante as marés de quadratura, e as florações tiveram frequência de aproximadamente 15 dias, no final da quadratura, predominando diatomáceas em cadeia e eventualmente flagelados e diatomáceas penadas. A composição taxonômica variou entre florações e o padrão quinzenal foi significativamente alterado durante eventos com alta descarga de água doce oriundos da usina hidroelétrica Henry Borden (> 9*106.m 3 ) o que impediu o acúmulo de fitoplâncton no período das quadraturas.

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Silicon Retention in River Basins: Far-reaching Effects on Biogeochemistry and Aquatic Food Webs in Coastal Marine Environments

Cited by 108 publications

References 30 publications

Nitrogen as the limiting nutrient for eutrophication in coastal marine ecosystems: Evolving views over three decades

Nitrogen as the limiting nutrient for eutrophication in coastal marine ecosystems: Evolving views over three decades

Effects of upstream hydropower operation on riverine particle transport and turbidity in downstream lakes

Temporal variability of chlorophyll-a in the São Vicente estuary

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