13 May 2022
13 May 2022
Status: this preprint is currently under review for the journal ESSD.

An evaluation of long-term physical and hydrochemical measurements at the Sylt Roads Marine Observatory (1973–2019), Wadden Sea, North Sea

Johannes J. Rick1, Mirco Scharfe, Tatyana Romanova1, Justus E. E. van Beusekom3, Ragnhild Asmus1, Harald Asmus1, Finn Mielck1, Anja Kamp4, Rainer Sieger, and Karen H. Wiltshire1,2 Johannes J. Rick et al.
  • 1Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Wattenmeerstation Sylt, Hafenstraße 43, D-25992 List, Germany
  • 2Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Meeresstation, Biologische Anstalt Helgoland, Kurpromenade, D-27498 Helgoland, Germany
  • 3Helmholtz-Zentrum Hereon, Institute of Carbon Cycles, Department Aquatic Nutrient Cycles, Max-Planck-Straße 1, 21502 Geesthacht
  • 4Hochschule Bremen - City University of Applied Science, Fakultät 5, Abt. Schiffbau und Meerestechnik, Nautik, Biologie, Bionik, Neustadtswall 30, 28199 Bremen
  • deceased

Abstract. The Sylt Roads pelagic time series covers physical and hydrochemical parameters at five neighboring stations in the Sylt-Rømø Bight, Wadden Sea, North Sea. Since the beginning of the time series in 1973, sea surface temperature (SST), salinity, ammonium, nitrite, nitrate and soluble reactive phosphorus (SRP) were measured twice a week. Other parameters were introduced later (dissolved silicate (Si) – since 1974, pH - since 1979, dissolved organic nitrogen (DON) – since 1996, dissolved organic phosphorus (DOP) – since 2001, chlorophyll a – since 1979, suspended particulate matter (SPM) – since 1975) and in case of dissolved oxygen were already discontinued (1979–1983). In the years 1977, 1978 and 1983 no sampling took place. Since the start of the continuous sampling in 1984, the sea surface temperature in the bight has risen by +1.11 °C, with the highest increases during the autumn months, while the pH and salinity decreased by 0.23 and 0.33 units, respectively. Summer and autumn salinities are generally significantly elevated compared to spring and winter conditions. Dissolved nutrients (ammonium, nitrite, nitrate and SRP) displayed periods of intense eutrophication (1973–1998) and de-eutrophication since 1999. Silicate showed significantly higher winter levels since 1999. Interestingly, phytoplankton parameters did not mirror these large changes in nutrient concentrations, as a seasonal comparison of the two eutrophication periods showed no significant differences with regard to chlorophyll a. This phenomenon might be triggered by an important switch in nutrient limitation during the time series: Until 1998, the phytoplankton was probably primarily limited by silicate, and since 1999 SRP limitation became increasingly important. 

Repository-Reference: Rick et al. (2017b–e, 2020a–o) 
doi: 10.1594/PANGAEA.150032, 873549, 873545, 873547, 918018, 918032, 
918027, 918023, 918033, 918028, 918024, 918034, 918029, 918025, 918035, 
918030, 918026, 918036, 918031.

Johannes J. Rick et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on essd-2020-263', Anonymous Referee #1, 15 Sep 2022
  • RC2: 'Comment on essd-2020-263', Anonymous Referee #2, 07 Oct 2022
  • AC1: 'Comment on essd-2020-263', Johannes Josef Rick, 05 Dec 2022

Johannes J. Rick et al.

Data sets

Long-term physical and hydrochemical measurements at Sylt Roads LTER (1973-2013), Wadden Sea, North Sea Rick, Johannes J.; van Beusekom, Justus; Romanova, Tatyana; Wiltshire, Karen Helen

Johannes J. Rick et al.


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Short summary
The Sylt Roads TS (Wadden Sea, NS) is illustrated. Since 1984, the water temperature has risen by 1.1 °C, while pH and salinity decreased by 0.2 and 0.3 units. Nutrients (P, N) displayed a period of high eutrophication till 1998 followed by a decrease since 1999 while silicate showed in parallel an increase. Chlorophyll did not mirror these changes probably due a switch in nutrient limitation: Until 1998, the algae were primarily limited by Si, and since 1999 P limitation became more important.