The Helgoland Roads Zooplankton time series was started in 1975 by Wulf Greve, initially at the Biologische Anstalt Helgoland institute and later continued in cooperation with the German Centre for Marine Biodiversity and the Federal Maritime and Hydrographic Agency. It is now managed by the Biological Station Helgoland again.
Every Monday, Wednesday, and Friday two oblique plankton net samples (150 μm, 500 μm) are collected from the monitoring site (54° 11' 18\" N, 7° 54' E). From each sample, almost 400 taxonomic entities of holoplankton and meroplankton (e.g., benthic and fish larvae) are identified and counted for abundance. The purpose of the Helgoland Roads programme is to monitor and document high frequency plankton population dynamics to detect and investigate community dynamics at seasonal and longer time scales and to better understand long-term changes in biodiversity.
","EngDescr":"At the Helgoland Roads sampling site, small copepods, mostly Acartia clausi, Temora longicornis, Pseudocalanus sp., represent a significant fraction of the total zooplankton population. Seasonal and interannual variability in the small copepods are large both in timing as well as in magnitude. Maximum density can be found in most years in the mid-summer, and the 40 year time-series shows clear decadal variability. Starting with a negative phase at the beginning of the times series (1975), copepod abundance increased steadily and was consistently higher than the average during much of the 1980s. After a period of transition (1990-1997), copepod density decreased and has remained in a negative phase where abundances are consistently low.
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The high sampling frequency of the Helgoland Roads time series has provided a unique opportunity to study long-term trends in abiotic and biotic parameters, but also ecological phenomena, such as seasonal interactions between different food web components, niche properties, and the dynamics and timing of the spring bloom. It has also facilitated close examination of the dynamics of new species appearing in the local ecosystem.
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