Processes of Stratification and Destratification During An Extreme River Discharge Event in the German Bight ROFI

Chegini, Fatemeh; Holtermann, Peter; Kerimoglu, Onur; Becker, Marius; Kreus, Markus; Klingbeil, Knut; Gräwe, Ulf; Burchard, Hans

doi:10.1029/2019jc015987

Cited by 14 publications

(21 citation statements)

References 48 publications

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“…S1), however, is a shallow, tidally energetic system, characterized by strong horizontal salinity gradients. It is also subject to intermittent stratification driven by tidal straining (Burchard et al 2008), depending also on the wind direction, phase of the spring-neap cycle and riverine discharge events (Chegini et al 2020). In this highly dynamic area, such short-lived stratification events are not likely to have systematic effects on the nutrient environment of phytoplankton.…”

Section: Discussionmentioning

confidence: 99%

Temporal declines in Wadden Sea phytoplankton cell volumes observed within and across species

Hillebrand

Carvalho

Dajka

et al. 2021

Limnology & Oceanography

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Cell size is a master trait in the functional ecology of phytoplankton correlating with numerous morphological, physiological, and life-cycle characteristics of species that constrain their nutrient use, growth, and edibility. In contrast to well-known spatial patterns in cell size at macroecological scales or temporal changes in experimental contexts, few data sets allow testing temporal changes in cell sizes within ecosystems. To analyze the temporal changes of intraspecific and community-wide cell size, we use the phytoplankton data derived from the Lower Saxony Wadden Sea monitoring program, which comprises sample-and species-specific measurements of cell volume from 1710 samples collected over 14 yr. We find significant reductions in both the cell volume of most species and the weighted mean cell size of communities. Mainly diatoms showed this decline, whereas the size of dinoflagellates seemed to be less responsive. The magnitude of the trend indicates that cell volumes are about 30% smaller now than a decade ago. This interannual trend is overlayed by seasonal cycles with smaller cells typically observed in summer. In the subset of samples including environmental conditions, small community cell size was strongly related to high temperatures and low total phosphorus concentration. We conclude that cell size captures ongoing changes in phytoplankton communities beyond the changes in species composition. In addition, based on the changes in species biovolumes revealed by our analysis, we warn that using standard cell size values in phytoplankton assessment will not only miss temporal changes in size, but also lead to systematic errors in biomass estimates over time.

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Section: Discussionmentioning

confidence: 99%

Temporal declines in Wadden Sea phytoplankton cell volumes observed within and across species

Hillebrand

Carvalho

Dajka

et al. 2021

Limnology & Oceanography

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“…• Horizontal density gradients generated by the river runoff induce periodic stratification that interacts with the tides (Simpson et al, 1990) • (Simpson et al, 2002) • Rhine (Simpson and Souza, 1995) • Elbe-Weser (Chegini et al, 2020) • Baltic Sea…”

Section: Effects Of Underwater Structuresmentioning

confidence: 99%

The Effects of Offshore Wind Farms on Hydrodynamics and Implications for Fishes

Berkel¹,

Burchard²,

Christensen³

et al. 2020

Oceanog

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“…Temporal trends in surface water variables such as temperature, salinity, and NO 3 − were determined along the cruise track. The Elbe system is subject to short-term dynamic extreme events such as heatwaves and heavy rainfall which significantly affect the waters of the southern North Sea (Voynova et al, 2017;Chegini et al, 2020). A total of 730 measurements were performed by the OPUS sensor during the 2-day cruise period.…”

Section: Field Deploymentsmentioning

confidence: 99%

Improved Calibration and Data Processing Procedures of OPUS Optical Sensor for High-Resolution in situ Monitoring of Nitrate in Seawater

et al. 2021

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Nitrate, an essential nutrient for primary production in natural waters, is optically detectable in the ultraviolet spectral region of 217–240 nm, with no chemical reagents required. Optical nitrate sensors allow monitoring at high temporal and spatial resolutions that are difficult to achieve with traditional approaches involving collection of discrete water samples followed by wet-chemical laboratory analysis. The optical nitrate measurements are however subject to matrix interferences in seawater, including bromide, at the spectral range of interest. Significant progress has been made over the last 10 years in improving data quality for seawater nitrate analysis using the ISUS and SUNA (Seabird Scientific, United States) optical sensors. Standardization of sensor calibration and data processing procedures are important for ensuring comparability of marine nitrate data reported in different studies. Here, we improved the calibration and data processing of the OPUS sensor (TriOS GmbH, Germany), and tested five OPUS sensors simultaneously deployed under identical conditions in the laboratory in terms of inter-sensor similarities and differences. We also improved the sampling interval of the OPUS to 3 s in a continuous mode by a custom-built controller, which facilitates the integration of the sensor into autonomous profiling systems. Real-time, high-resolution, in situ measurements were conducted through (1) underway surface measurements in the southeastern North Sea and (2) depth profiles on a conductivity–temperature–depth frame in the tropical Atlantic Ocean. The nitrate data computed from the optical measurements of the sensor agreed with data from discrete water samples analyzed via conventional wet-chemical methods. This work demonstrates that the OPUS sensor, with improved calibration and data processing procedures, allows in situ quantification of nitrate concentrations in dynamic coastal waters and the open ocean, with an accuracy better than ∼2 μM and short-term precision of 0.4 μM NO3–. The OPUS has a unique depth rating of 6,000 m and is a good and cost-effective nitrate sensor for the research community.

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Processes of Stratification and Destratification During An Extreme River Discharge Event in the German Bight ROFI

Cited by 14 publications

References 48 publications

Temporal declines in Wadden Sea phytoplankton cell volumes observed within and across species

Temporal declines in Wadden Sea phytoplankton cell volumes observed within and across species

The Effects of Offshore Wind Farms on Hydrodynamics and Implications for Fishes

Improved Calibration and Data Processing Procedures of OPUS Optical Sensor for High-Resolution in situ Monitoring of Nitrate in Seawater

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