Evaluating Uncertainties in Reconstructing the Pre-eutrophic State of the North Sea

Stegert, Christoph; Lenhart, Hermann; Blauw, Anouk; Friedland, René; Leujak, Wera; Kerimoglu, Onur

doi:10.3389/fmars.2021.637483

Cited by 4 publications

(6 citation statements)

References 61 publications

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“…Using back‐tracking modelling approaches, some studies (e.g. Kerimoglu et al, 2018; Stegert et al, 2021) have shown a much lower phytoplankton biomass in the pre‐industrial nutrient‐poor coastal system. However, this type of approach does not allow the study of the taxonomic composition, and even less functional structure, but instead treats the phytoplankton community as a whole, either using chlorophyll a concentration or total abundance.…”

Section: Discussionmentioning

confidence: 99%

Environmentally induced functional shifts in phytoplankton and their potential consequences for ecosystem functioning

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Wiltshire

McLean

et al. 2022

Global Change Biology

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Phytoplanktonic organisms are particularly sensitive to environmental change, and, as they represent a direct link between abiotic and biotic compartments within the marine food web, changes in the functional structure of phytoplankton communities can result in profound impacts on ecosystem functioning. Using a trait‐based approach, we examined changes in the functional structure of the southern North Sea phytoplankton over the past five decades in relation to environmental conditions. We identified a shift in functional structure between 1998 and 2004 which coincides with a pronounced increase in diatom and decrease in dinoflagellate abundances, and we provide a mechanistic explanation for this taxonomic change. Early in the 2000s, the phytoplankton functional structure shifted from slow growing, autumn blooming, mixotrophic organisms, towards earlier blooming and faster‐growing microalgae. Warming and decreasing dissolved phosphorus concentrations were linked to this rapid reorganization of the functional structure. We identified a potential link between this shift and dissolved nutrient concentrations, and we hypothesise that organisms blooming early and displaying high growth rates efficiently take up nutrients which then are no longer available to late bloomers. Moreover, we identified that the above‐mentioned functional change may have bottom‐up consequences, through a food quality‐driven negative influence on copepod abundances. Overall, our study highlights that, by altering the phytoplankton functional composition, global and regional changes may have profound long‐term impacts on coastal ecosystems, impacting both food‐web structure and biogeochemical cycles.

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Section: Discussionmentioning

confidence: 99%

Environmentally induced functional shifts in phytoplankton and their potential consequences for ecosystem functioning

Pane

Wiltshire

McLean

et al. 2022

Global Change Biology

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“…This study found differences in historical coastal DIP loads (compared to JMP-EUNOSAT) up to ~10%. Stegert et al (2021) used estimates of historical river inputs from both MONERIS and E-HYPE and compared their influence on the nutrient and chlorophyll-a concentrations in the North Sea. They found higher marine nutrient concentrations, particularly in coastal zones, if the E-HYPE values were applied, with coastal zone DIP differences of 40% in the German Bight.…”

Section: Pre-eutrophic Scenariomentioning

confidence: 99%

“…For P loads, E-HYPE percentage results were used for most rivers, but for some rivers alternative estimates were used. Due to large differences between E-HYPE and the finer scale catchment models, and uncertainty in the E-HYPE P load estimation (Donnelly et al, 2013;Stegert et al, 2021), its historic P load percentages were replaced for rivers where alternative, more detailed information was available, as follows. The Danish authorities, basing their estimates on Timmermann et al ( 2021) set their pre-eutrophic P loads at 36% of current day loads for all Danish rivers.…”

Section: Pre-eutrophic Scenariomentioning

confidence: 99%

“…In the past several single model approaches have been used to estimate the pre-eutrophic state of marine systems (Schernewski and Neumann, 2005;Schernewski et al, 2015;Kerimoglu et al, 2018), including using multiple single models to cover a larger area (Desmit et al, 2018). Ensemble modelling addresses the inherent uncertainties in single model results and is increasingly applied in marine response studies (Almroth and Skogen, 2010;Lenhart et al, 2010;Eilola et al, 2011;Meier et al, 2019;Friedland et al, 2021;Stegert et al, 2021) despite the higher efforts involved. These efforts include the necessity to combine a variety of modelling groups and their individual models, as well as agreement to a common protocol to ensure comparable results, agreement on suitable scenarios and to a common analysis of the obtained scenario results.…”

Section: Ensemble Modelling As a Tool For Marine Managementmentioning

confidence: 99%

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Deriving pre-eutrophic conditions from an ensemble model approach for the North-West European seas

et al. 2023

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The pre-eutrophic state of marine waters is generally not well known, complicating target setting for management measures to combat eutrophication. We present results from an OSPAR ICG-EMO model assessment to simulate the pre-eutrophic state of North-East Atlantic marine waters. Using an ecosystem model ensemble combined with an observation-based weighting method we derive sophisticated estimates for key eutrophication indicators. Eight modelling centres applied the same riverine nutrient loads, atmospheric nutrient deposition rates and boundary conditions to their specific model set-up to ensure comparability. The pre-eutrophic state was defined as a historic scenario of estimated nutrient inputs (riverine, atmospheric) at around the year 1900, before the invention and widespread use of industrial fertilizers. The period 2009-2014 was used by all participants to simulate both the current state of eutrophication and the pre-eutrophic scenario, to ensure that differences are solely due to the changes in nutrient inputs between the scenarios. Mean values were reported for winter dissolved inorganic nutrients and total nutrients (nitrogen, phosphorus) and the nitrogen to phosphorus ratio, and for growing season chlorophyll, chlorophyll 90th percentile, near-bed oxygen minimum and net phytoplankton production on the level of the OSPAR assessment areas. Results showed distinctly lower nutrient concentrations and nitrogen to phosphorus ratio’s in coastal areas under pre-eutrophic conditions compared to current conditions (except in the Meuse Plume and Seine Plume areas). Chlorophyll concentrations were estimated to be as much as ~40% lower in some areas, as were dissolved inorganic phosphorus levels. Dissolved inorganic nitrogen levels were found to be up to 60% lower in certain assessment areas. The weighted average approach reduced model disparities, and delivered pre-eutrophic concentrations in each assessment area. Our results open the possibility to establish reference values for indicators of eutrophication across marine regions. The use of the new assessment areas ensures local ecosystem functioning is better represented while political boundaries are largely ignored. As such, the reference values are less associated to member states boundaries than to ecosystem boundaries.

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“…However, Contracting Parties used different approaches in establishing reference conditions to derive these values, leading to variable assessment levels and different outcomes of the eutrophication assessment across national borders (OSPAR, 2003b(OSPAR, , 2008b(OSPAR, , 2017. OSPAR recognized these limitations and requested the ICG-EMO working group to develop a coherent assessment framework across Contracting Parties that share assessment areas (Blauw et al, 2019;Gohin et al, 2019;Stegert et al, 2021).…”

Section: Harmonizing Assessment Levelsmentioning

confidence: 99%

A first ecological coherent assessment of eutrophication across the North-East Atlantic waters (2015–2020)

Devlin,

Prins,

Enserink

et al. 2023

Front. Ocean Sustain.

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This paper presents the outcomes of the fourth application of the Common Procedure for the Identification of the Eutrophication Status of the OSPAR Maritime Area (the “Common Procedure”), conducted for the period 2015–2020 for the North East Atlantic. Previously, OSPAR has assessed eutrophication based on national assessment areas and disparate approaches lacking a transparent and comparable basis. A more harmonized approach has now been achieved through development of ecologically relevant assessment areas defined by oceanographic criteria rather than international boundaries, allowing for consistent assessments across exclusive economic zones and acknowledging that eutrophication is a transboundary problem. Thresholds that were specific for those harmonized assessment areas and eutrophication parameters have been derived primarily from an ensemble modeling approach to determine pre-eutrophic conditions. Common assessment areas and harmonized thresholds have enabled, for the first time, an objective and comparable assessment of the eutrophication status of the whole OSPAR Maritime Area. This establishes a level playing field for managing eutrophication and a solid basis for deriving OSPAR nutrient reduction targets as a prerequisite for targeted and successful regional eutrophication management. This assessment shows that eutrophication problem areas persist, in particular along the continental coasts from France to Denmark/Sweden and in the Greater North Sea and the Bay of Biscay and Iberian coast. The main areas affected by eutrophication are the plumes and adjacent coastal areas in the Greater North Sea and Bay of Biscay/Iberian Coast, with riverine nutrient inputs remaining the major source of nutrient pollution. Approximately 6% (152,904 km2) of the OSPAR Maritime Area is eutrophic, with the impacted area supporting many important ecosystem services. Fifty-eight percent of river plume areas (eight assessment areas out of 14), 22% (five of 27) of the coastal areas and 10% (three of 17) of the shelf areas were classified as problem areas. Application of the current assessment process to historical data from the previous three OSPAR assessment periods shows a gradual improvement since 2000. However, the OSPAR 2010 objective “to combat eutrophication, with the ultimate aim of achieving and maintaining a healthy marine environment where anthropogenic eutrophication does not occur” has not yet been fully achieved. Further measures to reduce nutrient loads are needed to ensure long-term sustainability of our coastal waters.

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Evaluating Uncertainties in Reconstructing the Pre-eutrophic State of the North Sea

Cited by 4 publications

References 61 publications

Environmentally induced functional shifts in phytoplankton and their potential consequences for ecosystem functioning

Environmentally induced functional shifts in phytoplankton and their potential consequences for ecosystem functioning

Deriving pre-eutrophic conditions from an ensemble model approach for the North-West European seas

A first ecological coherent assessment of eutrophication across the North-East Atlantic waters (2015–2020)

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