Long-term changes of the annual cycles of meteorological, hydrographic, nutrient and phytoplankton time series at Helgoland and at LV ELBE 1 in the German Bight

Radach, Günther; Berg, J.; Hagmeier, Erik

doi:10.1016/0278-4343(90)90054-p

Cited by 156 publications

(63 citation statements)

References 21 publications

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“…During summer most nutrients are delivered into the coastal zone due to the mineralization of organic matter and continental freshwater inputs (Brockmann and Eberlein, 1986;Beusekom and Diel-Christiansen, 2009). In general, one or two additional diatom blooms occur which are mostly followed up by non-diatom (flagellate) blooms (Radach et al, 1990). In August phytoplankton production reaches another maximum, which is followed by a decrease to lowest production in October-November (Radach et al, 1990;Beusekom and Diel-Christiansen, 1994).…”

Section: Study Sitementioning

confidence: 99%

“…The first spring bloom is dominated by diatoms and is in general limited by the availability of silicic acid in the water column (Beusekom and Diel-Christiansen, 2009). The second spring bloom is dominated by flagellates and its size is regulated by the amount of nitrogen and phosphorus nutrients which are left in the water column after the first diatom bloom (Gieskes and van Bennekom, 1973;Radach et al, 1990;Joint and Pomroy, 1993). During summer most nutrients are delivered into the coastal zone due to the mineralization of organic matter and continental freshwater inputs (Brockmann and Eberlein, 1986;Beusekom and Diel-Christiansen, 2009).…”

Section: Study Sitementioning

confidence: 99%

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Seasonal dynamics of the biogenic silica cycle in surface sediments of the Helgoland Mud Area (southern North Sea)

Oehler

Schlüter

Schückel

2015

Continental Shelf Research

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a b s t r a c tIn coastal waters and the ocean silicic acid (Si(OH) 4 ) is a key nutrient for primary producers (e.g. diatoms) and other siliceous organisms, because it is required for the formation of frustules and other hard parts made of biogenic silica (bSi). Especially in shallow waters like the southern North Sea, dissolution of bSi in surface sediments and the reflux of silicic acid from sediments into the water column is an important feedback mechanism for sustaining primary production. We investigated the temporal variability of benthic silicic acid fluxes and the recycling efficiency of bSi in surface sediments of the Helgoland Mud Area (southern North Sea). For this purpose we used different methods including a benthic chamber lander system for in situ flux studies of Si(OH) 4 , ex situ sediment incubations, pore water studies and sediment analysis. . The relevance of biological mediated transport for the recycling of Si(OH) 4 was underlined by comparing in situ and ex situ sediment incubations, pore water studies, as well as depth profiles of benthic macrofauna. Mass budget calculations indicate that about 1.7-2.2 mol bSi m À 2 settle annually at the seafloor, off which about 60-81% are recycled within surface sediments and transported back into the water column.

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Section: Study Sitementioning

confidence: 99%

Section: Study Sitementioning

confidence: 99%

Seasonal dynamics of the biogenic silica cycle in surface sediments of the Helgoland Mud Area (southern North Sea)

Oehler

Schlüter

Schückel

2015

Continental Shelf Research

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“…Greve et al 1996;Kro¨ncke et al 1998;Edwards et al 1999;Reid and Edwards 2002;Stebbing et al 2002;Loza´n et al 2003) which seems to be more profound and persistent than shifts recorded for earlier decades (e.g. Radach et al 1990;Austen et al 1991;Evans and Edwards 1993).…”

Section: Introductionmentioning

confidence: 94%

Long-term changes in the macrozoobenthos around the rocky island of Helgoland (German Bight, North Sea)

Franke

Gutow

2004

Helgol Mar Res

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The paper briefly summarizes what is known about long-term changes (facts, causes, consequences) in the macrozoobenthos of intertidal and subtidal hardbottom communities around the island of Helgoland (German Bight, North Sea). There is increasing observational evidence that these communities (spectrum and abundances of species) are changing on a long-term temporal scale. The reasons are diverse and mainly anthropogenic. A shift in North Sea climate towards more oceanic conditions may be among the most important factors driving the recent changes in species spectrum. Many of the species which have been recorded as new to the Helgoland area during the past decade are southern (oceanic) species which may be considered as indicators of a warming trend.

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“…Observations of nutrient concentrations in the coastal waters, for instance at Helgoland Roads (German Bight), have shown that the temporal development of riverine inputs was imposed on the receiving coastal waters (Fock 2003). The strong changes of N:P ratios in the sea over the last decades were attributed to the change of nutrient inputs during that time (Radach et al 1990;Hickel et al 1992;Hickel 1998). This had severe consequences for the coastal ecosystem, e.g., a drastic change in algal species composition (Van Beusekom and DielChristiansen 1994).…”

Section: Riverine Inputs In Relation To Other Budget Contributions Tomentioning

confidence: 99%

Variability of continental riverine freshwater and nutrient inputs into the North Sea for the years 1977–2000 and its consequences for the assessment of eutrophication

Radach¹,

Pätsch²

2007

Estuaries and Coasts

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We determined the monthly and annual riverine freshwater, nitrogen (N) and phosphorus (P) loading into the North Sea from Belgium, The Netherlands, and Germany for the years 1977-2000. An average of 133 km 3 yr 21 of the 309 km 3 yr 21 precipitation into the watershed is carried by the rivers into the sea. Total freshwater discharge fluctuates with a strong 6-7 yr periodicity, is strongly correlated with precipitation, and exhibits a slight long-term decrease. The temporal changes of regional patterns of precipitation lead to changing ratios of annual discharge of the western rivers compared to the eastern rivers, varying between 2.2 and 3.5. The long-term oscillations in discharge were more pronounced as discharge increased. The annual means of total and dissolved inorganic N and P loads were estimated to be 722 and 582 kt N yr 21 and 48 and 26 kt P yr 21 , respectively. The monthly N loads were much more strongly correlated with discharge, compared to the monthly P loads. Total N and P as well as dissolved inorganic N also demonstrated a 6-7 yr periodicity. The annual N loads decreased by about 17 kt N yr 21 from 1977 to 2000. The total phosphorus and phosphate loads decreased from about 80 and 50 kt P yr 21 in the 1980s to 25 and 12 kt P yr 21 , respectively, in the 1990s. The western rivers contributed the major part of the nutrient loads. The long-term oscillations in their nutrient loads were much more pronounced, compared to the eastern rivers. The area-specific loading rates estimated for all rivers are comparable to earlier estimates using shorter data records, smaller sample sizes, and a less complete watershed monitoring program. The monthly and annual average N:P ratios and their variability increased considerably for individual rivers during the study interval. These results confirm that the water quality of European continental rivers is strongly influenced by intense land use. They demonstrate the necessity for using long time series monitoring results to assess change and evaluate the effects of climate change on the North Sea coastal ecosystems, using ecosystem models on decadal time scales.

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Long-term changes of the annual cycles of meteorological, hydrographic, nutrient and phytoplankton time series at Helgoland and at LV ELBE 1 in the German Bight

Cited by 156 publications

References 21 publications

Seasonal dynamics of the biogenic silica cycle in surface sediments of the Helgoland Mud Area (southern North Sea)

Seasonal dynamics of the biogenic silica cycle in surface sediments of the Helgoland Mud Area (southern North Sea)

Long-term changes in the macrozoobenthos around the rocky island of Helgoland (German Bight, North Sea)

Variability of continental riverine freshwater and nutrient inputs into the North Sea for the years 1977–2000 and its consequences for the assessment of eutrophication

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