Helgoland Roads, North Sea: 45 Years of Change

Abstract

The Helgoland Roads time series is one of the richest temporal marine data sets available. Running since 1962, it documents changes for phytoplankton, salinity, Secchi disc depths and macronutrients. Uniquely, the data have been carefully quality controlled and linked to relevant meta-data, and the pelagic time series is further augmented by zooplankton, intertidal macroalgae, macrozoobenthos and bacterioplankton data. Data analyses have shown changes in hydrography and biota around Helgoland. In the late 1970s, water inflows from the south-west to the German Bight increased with a corresponding increase in flushing rates. Salinity and annual mean temperature have also increased since 1962 and the latter by an average of 1.67°C. This has influenced seasonal phytoplankton growth causing significant shifts in diatom densities and the numbers of large diatoms (e. g. Coscinodiscus wailesii). Changes in zooplankton diversity have included the appearance of the ctenophore Mnemiopsis leidyi. The macroalgal community also showed an increase in green algal and a decrease in brown algal species after 1959. Over 30 benthic macrofaunal species have been newly recorded at Helgoland over the last 20 years, with a distinct shift towards southern species. These detailed data provide the basis for long-term analyses of changes on many trophic levels at Helgoland Roads.

Changes in the phytoplankton community at Helgoland, North Sea: lessons from single spot time series analyses

“…These species-comprehensive changes suggest that changes affected the whole habitat, an interpretation that is supported by Wiltshire et al (2008Wiltshire et al ( , 2010, who estimated trends for the habitat from the Helgoland Roads data. The fact that statistically significant shifts of the niche were detected mainly for the second break point indicates that driving mechanisms for these shifts have to be searched within the set of factors causing the later regime shift, that is, water temperature and weather conditions (Weijerman et al 2005).…”

Estimation of the Potential Detection of Diatom Assemblages Based on Ocean Color Radiance Anomalies in the North Sea

“…The literature records show that their occurrence in some locations of the southern North Sea relates to specific environmental conditions (e.g., Edwards et al, 2001;Rousseau et al, 2002;Wiltshire et al, 2010). In fact, the assemblage characterized by Thalassionema nitzschoides is common in high-nutrient conditions in neritic waters (Van Iperen et al, 1993) as is the case in spring and autumn in the southern North Sea (Commission, 2010).…”

High-resolution monitoring of marine protists based on an observation strategy integrating automated on-board filtration and molecular analyses

“…Among them, one long-lasting time series, the Helgoland Roads time series, is maintained by the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research at the island Helgoland in the German Bight (North Sea). The dataset comprises information on abundance of phytoplankton on a daily basis since 1962 (Kraberg et al, 2015;Wiltshire et al, 2009). However, it does not provide information on the abundance of the smallest phytoplankton species and is restricted to one sampling point.…”