Impact of global change on coastal oxygen dynamics and risk of hypoxia

Meire, Lorenz; Soetaert, K.; Meysman, F. J. R.

doi:10.5194/bg-10-2633-2013

Cited by 78 publications

(60 citation statements)

References 62 publications

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“…In addition, a reduced ability of ecosystems to remove nitrogen via denitrification and anaerobic ammonium oxidation may be related to hypoxia and could lead to accelerated eutrophication (49). Finally, an increase in water temperature could also decrease the threshold of P concentrations sustaining hypoxia, with more intense stratification, reduced solubility of oxygen at higher water temperatures, and enhanced metabolic rates in warmer bottom waters (51).…”

Section: Discussionmentioning

confidence: 99%

Urban point sources of nutrients were the leading cause for the historical spread of hypoxia across European lakes

Jenny

Normandeau

Francus

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

100

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Enhanced phosphorus (P) export from land into streams and lakes is a primary factor driving the expansion of deep-water hypoxia in lakes during the Anthropocene. However, the interplay of regional scale environmental stressors and the lack of long-term instrumental data often impede analyses attempting to associate changes in land cover with downstream aquatic responses. Herein, we performed a synthesis of data that link paleolimnological reconstructions of lake bottom-water oxygenation to changes in land cover/use and climate over the past 300 years to evaluate whether the spread of hypoxia in European lakes was primarily associated with enhanced P exports from growing urbanization, intensified agriculture, or climatic change. We showed that hypoxia started spreading in European lakes around CE 1850 and was greatly accelerated after CE 1900. Socioeconomic changes in Europe beginning in CE 1850 resulted in widespread urbanization, as well as a larger and more intensively cultivated surface area. However, our analysis of temporal trends demonstrated that the onset and intensification of lacustrine hypoxia were more strongly related to the growth of urban areas than to changes in agricultural areas and the application of fertilizers. These results suggest that anthropogenically triggered hypoxia in European lakes was primarily caused by enhanced P discharges from urban point sources. To date, there have been no signs of sustained recovery of bottom-water oxygenation in lakes following the enactment of European water legislation in the 1970s to 1980s, and the subsequent decrease in domestic P consumption.Anthropocene | lake hypoxia | land cover/uses | meta-analysis | varves C hanges in land cover and land use have been identified as important drivers of phosphorus (P) transfers from terrestrial to aquatic systems, resulting in significant impacts on water resources (1-3). In post-World War II Europe, changes in land cover, land use, and P utilization caused widespread eutrophication of freshwaters (3). Elevated rates of P release from point sources to surface water bodies increased in step with population increases, with the novel use of P in domestic detergents and with enhanced connectivity of households to sewage systems that generated concentrated effluents (4). The intensification of agriculture and drastic increased use of fertilizers from industrial and manure sources resulted in elevated P concentrations in runoff from diffuse sources (4). These trends have now metastasized from Europe and North America to most nations, which explains the almost global development of eutrophication problems in surface waters (1).Much of our understanding regarding the interactions between changes in land cover/use, climate, and lake eutrophication comes from detailed studies of individual lakes (5), modeling exercises (1), and/or regional-scale syntheses of instrumental data (6, 7); these studies are largely based on relatively short time series (8). Depending on the multitudinous local differences in catchment and lake mor...

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Section: Discussionmentioning

confidence: 99%

Urban point sources of nutrients were the leading cause for the historical spread of hypoxia across European lakes

Jenny

Normandeau

Francus

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

100

View full text Add to dashboard Cite

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“…Due to these internal feedback mechanisms, recovery from hypoxia is often slow, hampering management of the problem through reductions in external nutrient loading (Vahtera et al, 2007). Furthermore, global warming is likely to exacerbate the spreading of hypoxia in many regions through enhanced nutrient inputs (linked to increased precipitation and discharge), decreased solubility of oxygen due to increased temperature, and acceleration of internal nutrient cycling (Meier et al, 2011;Meire et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

A 1500-year multiproxy record of coastal hypoxia from the northern Baltic Sea indicates unprecedented deoxygenation over the 20th century

et al. 2018

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Abstract. The anthropogenically forced expansion of coastal hypoxia is a major environmental problem affecting coastal ecosystems and biogeochemical cycles throughout the world. The Baltic Sea is a semi-enclosed shelf sea whose central deep basins have been highly prone to deoxygenation during its Holocene history, as shown previously by numerous paleoenvironmental studies. However, long-term data on past fluctuations in the intensity of hypoxia in the coastal zone of the Baltic Sea are largely lacking, despite the significant role of these areas in retaining nutrients derived from the catchment. Here we present a 1500-year multiproxy record of near-bottom water redox changes from the coastal zone of the northern Baltic Sea, encompassing the climatic phases of the Medieval Climate Anomaly (MCA), the Little Ice Age (LIA), and the Modern Warm Period (MoWP). Our reconstruction shows that although multicentennial climate variability has modulated the depositional conditions and delivery of organic matter (OM) to the basin the modern aggravation of coastal hypoxia is unprecedented and, in addition to gradual changes in the basin configuration, it must have been forced by excess human-induced nutrient loading. Alongside the anthropogenic nutrient input, the progressive deoxygenation since the beginning of the 1900s was fueled by the combined effects of gradual shoaling of the basin and warming climate, which amplified sediment focusing and increased the vulnerability to hypoxia. Importantly, the eutrophication of coastal waters in our study area began decades earlier than previously thought, leading to a marked aggravation of hypoxia in the 1950s. We find no evidence of similar anthropogenic forcing during the MCA. These results have implications for the assessment of reference conditions for coastal water quality. Furthermore, this study highlights the need for combined use of sedimentological, ichnological, and geochemical proxies in order to robustly reconstruct subtle redox shifts especially in dynamic, non-euxinic coastal settings with strong seasonal contrasts in the bottom water quality.

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“…Although hypoxia in the Chesapeake Bay has likely existed since European colonization Brush, 1991, 1993), recent studies have highlighted an accelerated rise in the number and spatial extent of hypoxic, as well as anoxic (DO concentrations < 0.2 mg L −1 ), events in the bay since the 1950s, primarily attributed to increased anthropogenic nutrient input (Hagy et al, 2004;Kemp et al, 2005;Gilbert et al, 2010). These impacts are likely to be exacerbated by future climate change (Najjar et al, 2010;Meire et al, 2013;Harding Jr. et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Challenges associated with modeling low-oxygen waters in Chesapeake Bay: a multiple model comparison

Irby

Friedrichs

et al. 2016

Biogeosciences

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Abstract. As three-dimensional (3-D) aquatic ecosystem models are used more frequently for operational water quality forecasts and ecological management decisions, it is important to understand the relative strengths and limitations of existing 3-D models of varying spatial resolution and biogeochemical complexity. To this end, 2-year simulations of the Chesapeake Bay from eight hydrodynamic-oxygen models have been statistically compared to each other and to historical monitoring data. Results show that although models have difficulty resolving the variables typically thought to be the main drivers of dissolved oxygen variability (stratification, nutrients, and chlorophyll), all eight models have significant skill in reproducing the mean and seasonal variability of dissolved oxygen. In addition, models with constant net respiration rates independent of nutrient supply and temperature reproduced observed dissolved oxygen concentrations about as well as much more complex, nutrient-dependent biogeochemical models. This finding has significant ramifications for short-term hypoxia forecasts in the Chesapeake Bay, which may be possible with very simple oxygen parameterizations, in contrast to the more complex full biogeochemical models required for scenario-based forecasting. However, models have difficulty simulating correct density and oxygen mixed layer depths, which are important ecologically in terms of habitat compression. Observations indicate a much stronger correlation between the depths of the top of the pycnocline and oxycline than between their maximum vertical gradients, highlighting the importance of the mixing depth in defining the region of aerobic habitat in the Chesapeake Bay when low-oxygen bottom waters are present. Improvement in hypoxia simulations will thus depend more on the ability of models to reproduce the correct mean and variability of the depth of the physically driven surface mixed layer than the precise magnitude of the vertical density gradient.

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Impact of global change on coastal oxygen dynamics and risk of hypoxia

Cited by 78 publications

References 62 publications

Urban point sources of nutrients were the leading cause for the historical spread of hypoxia across European lakes

Urban point sources of nutrients were the leading cause for the historical spread of hypoxia across European lakes

A 1500-year multiproxy record of coastal hypoxia from the northern Baltic Sea indicates unprecedented deoxygenation over the 20th century

Challenges associated with modeling low-oxygen waters in Chesapeake Bay: a multiple model comparison

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