Helgoland Roads Research Articles

Ecological long-term research at Helgoland (German Bight, North Sea): retrospect and prospect?an introduction

This paper summarizes and evaluates ecological long-term observations at the island of Helgoland (German Bight, North Sea). It is an introduction to a series of seven contributions to an issue of Helgoland Marine Research (vol. 58, no. 4) dealing with observations on the physico-chemical environment and the local biota (pelagic bacteria, phytoplankton, zooplankton, macroalgae, macrozoobenthos). More than 150 years of research at Helgoland (at the Biologische Anstalt Helgoland, BAH, since 1892), and particularly the Helgoland Roads time-series which started in 1962, has provided a multitude of data which represents a valuable basis for analysing past changes, evaluating the present status and predicting future changes in ecosystem parameters. Predicting the consequences of the recent rapid ecological change on regional and global scales requires increased efforts of focus on long-term ecological observations. Future efforts in this field will rely on the application of innovative advanced technology and on the concerted activities of a large number of institutions which only collectively can establish the large-scale patterns of temporal and spatial change in ecosystem functions.

Helgoland Roads meso- and macrozooplankton time-series 1974 to 2004: lessons from 30 years of single spot, high frequency sampling at the only off-shore island of the North Sea

The Helgoland Roads meso- and macrozooplankton time-series 1974 to 2004 is a high frequency (every Monday, Wednesday and Friday), fixed position monitoring and research programme. The distance to the coastline reduces terrestrial and anthropological disturbances and permits the use of Helgoland Roads data as indicators of the surrounding German Bight plankton populations. The sampling, determination and IT methodologies are given, as well as examples of annual succession, and inter-annual population dynamics of resident and immigrant populations. Special attention is given to the phenology and seasonality of zooplankton populations. The influence of winter sea surface temperature on the seasonality of spawning of the common sole Solea solea is given as an example for merozooplankton populations.

40-year long-term study of microbial parameters near Helgoland (German Bight, North Sea): historical view and future perspectives

Since 1873, the waters at Helgoland Roads (sampling station “Kabeltonne”) have been sampled daily to determine temperature and salinity. In 1962, microbiological parameters were determined for the first time to establish microbiological long-term studies on marine bacteria, starting with the colony-forming units (CFU). In the following years, several other microbiological parameters were integrated for different periods of time (e.g. activity parameters like ATP and ectoenzymatic activity, marine yeasts, oil-degrading bacteria, flagellates and molecular methods like PCR followed by denaturing gradient gel electrophoresis). To date, the total count of bacteria, flagellates and viruses have been acquired using fluorescent DNA dyes and epifluorescence microscopy. Here we present both a historical overview of the methods used and examples of results obtained over the past 40 years. Furthermore, we try to evaluate challenging new methods for marine microbial ecology, appropriate for long-term studies of marine bacteria.

Pseudoalteromonas spp. phages, a significant group of marine bacteriophages in the North Sea

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 27:233-239 (2002) - doi:10.3354/ame027233 Pseudoalteromonas spp. phages, a significant group of marine bacteriophages in the North Sea Antje Wichels*, Gunnar Gerdts, Christian Schütt Alfred-Wegener-Institut für Polar- und Meeresforschung, Biologische Anstalt Helgoland, 27498 Helgoland, Germany *E-mail: awichels@awi-bremerhaven.de ABSTRACT: The occurrence and distribution of specific bacteriophages of marine Pseudoalteromonas spp. in the North Sea (North Sea phages) and their genetic relationship to several previously isolated marine phage species from waters of the Helgoland Roads (German Bight, Helgoland phages) were investigated. During 3 cruises from the Elbe estuary to western Norwegian waters, phages were concentrated by ultrafiltration. Detection and isolation of North Sea phages were performed by plaque assay, with 70 host bacteria of the genus Pseudoalteromonas. The genetic relationship between North Sea phages from different stations and Helgoland phages, formerly described as Pseudoalteromonas spp. phages, was assessed by DNA-DNA hybridization. DNA probes were prepared using whole phage DNA derived from 13 Helgoland phages. This approach provides the first information on the distribution of specific Pseudoalteromonas spp. phage-host systems (PHS) in the North Sea. The occurrence of Pseudoalteromonas spp. phages, which are specific for the tested Pseudoalteromonas spp. host bacteria, was restricted to a narrow geographical region of the German Bight between 53°30¹ and 57°00¹N latitude. Most of the previously isolated Helgoland phages were highly host specific (54%), whereas this was true for only some of the 39 North Sea phages (16%). The most common Pseudoalteromonas spp. phage species found in the North Sea belong to the virus family Siphoviridae (species H103/1). Several phage strains within this phage species displayed different host sensitivity patterns. KEY WORDS: Marine phages · Pseudoalteromonas · Phage DNA probes · North Sea Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 27, No. 3. Online publication date: April 16, 2002 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2002 Inter-Research.

Analysis and interpretation of recurrent spatio-temporal patterns in zooplankton dynamics: a case study on Noctiluca scintillans (Dinophyceae) in the German Bight (North Sea)

Data from the Helgoland Roads time series and from two series of quasi-synoptical zooplankton surveys in 1979 and 1984 were analysed with respect to recurrent patterns of dynamics of the dinoflagellate Noctilucascintillans. Based on a Lotka–Volterra model, the patterns were interpreted in terms of potential interactions. The work was conducted as a comparative analysis consisting of spatial, temporal moving window correlations and cross-correlations. In a reverse of the principle of space-for-time substitution in ecosystem analysis, space-and-time concordance of results was applied to indicate the relevance of interactions in time and space. A time series model on intra-annual dynamics significantly reproduced the dynamics of N. scintillans in 1979 and 1984. Results indicate that the dynamics of N. scintillans populations were linked to the population dynamics of Pleurobrachiapileus(Ctenophora), Sagitta spp. (Chaetognatha), hydromedusae, especially Rathkeaoctopunctata and Lizziablondina, and copepod nauplii. Evaluation of historical data sets from the Wadden Sea and the Bulletin Trimestrial series supported the statistical analysis. A food web model for the postulated relationships is discussed. The statistical method did not allow us to distinguish between predatory or competitive interactions.

Predicting the seasonality of North Sea zooplankton

Phenology and seasonality of the population response patterns of marine Zooplankton provide a measure of the impact of climatic forcing upon the ecosystem, as most metazoans in the sea are periodically planktonic, usually in their propagative phase. The global warming expectancy suggests intensified consideration of this aspect of ecosystem research. On the basis of the “Helgoland Roads Zooplankton” time-series, such population specific investigations have been carried out. They suggest that temperature and wind stress modify the beginning, end, length and intensity of the seasonality of Zooplankton populations. Climatic forcing and solar irradiation forcing of the production driven trophic cycles are basically independent of each other. The response patterns vary, depending on the life-cycle strategy of each population. Positive and negative correlation with water temperature occur, as well as larger or smaller deviations from multi-annual means, and distances from the times of greatest temperature impact and population responses. Examples are given for the different kinds of response. The results are discussed with respect to the influx of the NAO and to the annual recruitment of marine metazoans.

Reproductive cycles of dominant calanoid copepods in the North Sea

The seasonal cycles of reproduction of the dominant copepods Acartia clausi, Temora longicornis, Centropages hamatus, C. typicus and Pseudocalanus spp. were studied at Helgoland Roads, southern North Sea. Egg production rate, clutch size, number of spawning females and pro- some length were compared with temperature and phytoplankton concentration. Female A. clausi, T. longicornis and Pseudocalanus spp. were present all year round. T. longicornis and Pseudocalanus spp. bred continuously throughout the year, although egg production rates and the proportion of spawning females were low in winter. A. clausi did not spawn between the end of September and the end of January. Female C. hamatus were absent from the water column from November to May, and C. typicus from February to August. As the latter 3 species spawn year round in warmer regions, low temperature inhibition of reproduction is suggested for Helgoland, where winter temperatures are below 0°C. Maximum egg production was observed in all species, except the late-arriving C. typicus, in April/May, when females were largest. Significant correlations were only obtained between clutch size or egg production rate and prosome length, which in turn was correlated with temperature. It is therefore concluded that for Helgoland waters temperature controlled egg production by its effect on prosome length, and that food conditions were not limiting.

Competition between different groups of phytoplankton for nutrients in the southern North Sea

Abstract A simple numerical model for the simulation of nutrient competition of two pelagic phytoplankton groups is discussed by which the indirect effect of silicate availability to flagellate biomass is examined. The model consists of six state variables: two nutrients (phosphate and silicate), two functional groups of phytoplankton (diatom biomass and flagellate biomass), detritus and benthos. The model is forced with a 9 component spectral model for solar radiation, with a seasonal cycle in water temperature, variable cloudiness with a periodicity of 5 days and turbulent mixing by tidal stirring and wind. The considered processes are primary production, using the Monod-Michaelis-Menten uptake kinetics and Steele's light function, respiration, mortality, detrital and benthal remineralization. A fixed Redfield ratio of C : Si : P of 106 : 16 : 1 is used. The system is computed with a Lagrangian model, using dynamically passive, but interactive tracers. The behaviour of the autonomous system is discussed and the effect of eutrophication is investigated in different runs with increasing phosphate concentration, with decreasing silicate concentration and both. A comparison with the measurements of Helgoland Roads shows a qualitative and quantitative good agreement. The annual net primary production is also in good agreement with observations. The simulation with increasing phosphate concentration only affects an increase of flagellate biomass due to the silicate limitation of the spring bloom of diatoms. A combination of phosphate increase and silicate decrease, however, leads to a shift in composition of functional groups with decreasing diatom biomass and increasing flagellate biomass. These results suggest that the indirect effect of silicate reduction in coastal waters favours strong flagellate bloom because of higher availability of riverborne nutrient loads.

Detecting relationships between the interannual variability in ecological time series and climate using a multivariate statistical approach‹a case study on Helgoland Roads zooplankton

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 10:179-191 (1998) - doi:10.3354/cr010179 Detecting relationships between the interannual variability in ecological time series and climate using a multivariate statistical approach--a case study on Helgoland Roads zooplankton Hauke Heyen1,*, Heino Fock2, Wulf Greve2 1GKSS Institut für Gewässerphysik, Max-Planck-Straße, D-21502 Geesthacht, Germany 2Forschungsinstitut Senckenberg, Notkestraße 31, D-22607 Hamburg, Germany *E-mail: heyen@gkss.de ABSTRACT: A multivariate statistical approach is presented that allows a systematic search for potential relationships between the variability in ecological time series and climate records. In this study, interannual variability in large- and mesoscale climate variables in the North Sea region is compared with variability in local zooplankton observations from Helgoland. The species Noctiluca scintillans (Protozoa), Temora longicornis and Acartia sp. (Copepoda), and spionid larvae (Polychaeta) are examined. The multivariate model detected several high correlations between zooplankton abundance and winter climate. Based on these correlations, complementary hypotheses about the causal relationships are discussed using available local data. KEY WORDS: Zooplankton · Climate · Variability · North Sea · Empirical Orthogonal Functions · Canonical Correlation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 10, No. 3. Online publication date: December 10, 1998 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 1998 Inter-Research.

A multiannual outbreak of the turbellanan Alaurina composita Mecznikow 1865 in the German Bight

The plankton time series of ‘Helgoland Roads’ has shown a multiannual population change in the abundance of the turbellarian Alaurina composita Mecznikow 1865. From the 1970s to the mid-1980s, the summer population increased by two orders of magnitude; since then, it has fallen by about one order of magnitude. As limnetic investigations in related species show, A.cornposita must be considered a key predator of the North Sea pelagial. Knowledge regarding the biology and ecology of the species is only rudimentary.

The human impact in the German Bight: Eutrophication during three decades (1962–1991)

The human impact in the German Bight, in the form of anthropogenic eutrophication, has been documented by a 30-year time-series measurement near the island of Helgoland. Since 1962, the Biologische Anstalt Helgoland has measured inorganic nutrients and phytoplankton abundance from daily samples at Helgoland Roads, a position 60 km off the main source of eutrophication, the River Elbe. Since the early sixties, phosphate concentrations rose for about a decade, levelling off to about twice the former concentrations for another decade, and then decreasing (since 1982) as a result of phosphate-reducing measures. Nitrate concentrations, however, have only increased since 1980/81, following Elbe river flood events. In 1987, three times the former concentrations were reached. A decrease has been observed only since 1991. This different development of phosphorus and nitrogen eutrophication led to a shift of inorganic N/P-ratios in the German Bight. The phosphate increase was more pronounced in the late summer “regeneration mode” conditions, the nitrate increase in the winter months. The eutrophication is not restricted to the inner German Bight and coastal waters of a salinity of <33, but has also occurred in more saline waters at S>33 psu (practical salinity unit), as characteristic for the outer German Bight. In this more saline water, phosphate and nitrate maximum levels occurred three years later, compared with the average Helgoland data, which are more representative of the inner German Bight. It is suggested that suspended particulate organic matter, as a long-distance carrier of nutrients, might have caused this delayed eutrophication in the outer German Bight waters. While the human impact is obvious as to nutrient concentrations, it is less obvious in phytoplankton stock enhancement. A general increase in phytoplankton biomass (about 3–4 times) was found, but this was mainly due to unidentified nanoflagellates of unknown trophic state, and subject to methodological errors. The causal relationships of phytoplankton stocks and eutrophication are not clearly understood, as natural variability is large and hydrographical factors possibly dominate. Additional nutrient input by Elbe river floods did not always result in elevated phytoplankton stocks near Helgoland, while extended periods of vertical density stratification of the German Bight water caused large plankton blooms.

Gymnodinium blooms in the Helgoland bight (North Sea) during August, 1968

1. As in other parts of the North Sea, dinoflagellate red tides occurred in Helgoland waters in August, 1968. Measurements of plankton, and physical and chemical water properties at the permanent station “Helgoland Roads” were analyzed to describe the blooms. In addition, planktological and hydrographical investigations at three areas south, southwest and northwest of Helgoland on 27 and 28 August, as well as at two drifting stations off the mouths of the Elbe and Eider rivers on 6 and 8 August, were used for this work. 2.Gymnodinium sp. was abundant at all these localities, forming blooms near Helgoland from 14 to 30 August, with a maximum of 3 to 3.25 × 106 cells/l (and 18 to 19µg chlorophylla/l) on 28 and 30 August at Helgoland Roads. The primary production was as high as 0.98 mg C/l in 6 hours in a suspension of 3.7 × 106 Gymnodinium/l, where diatoms had been removed. This means that one millionGymnodinium produced 0.265 mg C in 6 hours. At Helgoland Roads nitrate and nitrite were depleted at times, but not phosphate. 3. About 3 × 106 Gymnodinium sp./l were found in the upper 16.5 m of water investigated around Helgoland on 27 and 28 August (maximal 7.8 × 106 cells/l at 3 m). There was a marked vertical stratification ofGymnodinium with a concentration towards the surface during the day. This was particularly the case in the turbid water off the Elbe estuary, where numbers up to 0.3 × 106/l were counted.Gymnodinium sp. formed 96 to 99 % of the phytoplankton biomass during maximal development. The chlorophylla content of one millionGymnodinium was only 3.5µg. An extinktion of E=0.083/1 m was measured in a suspension of 106 Gymnodinium/l in samples with minimal other plankton and detritus. 4. The water masses containingGymnodinium blooms, which reached Helgoland after a change of wind direction, were characterized by lower salinity and higher temperature. This indicates that blooms developed in the coastally influenced water masses east of Helgoland. The red tides occurred during a period of minimal discharge of Elbe river water and of relatively high salinity of the coastal water in the Inner German Bight. They developed after a long period of calm winds. There were no records of reported fish or shellfish poisoning.

Parasites in larvae of the herring (Clupea harengus L.) fed with wild plankton

In winter 1965/66 larvae of Downsherring were reared in aquaria at the Marine Station of the Biologische Anstalt Helgoland. They were fed with wild plankton caught on Helgoland Roads. About 10% of the actively feeding larvae were lost due to two endo-parasites and two ecto-parasites. The endoparasites are: a nematode (Contracoecum sp.) which is taken in by the larvae with the food and enters the host's body cavity from the gut, and a cestode (Scolex pleuronectis) which is found in the posterior part of the gut. The ecto-parasites are: a copepodite stage of a lernaeocerid, which attaches itself preferably close to the anus area of the herring larvae, and the copepode Caligus rapax. The nematode and copepodite were observed when the larvae had reached a total length of 9 to 13 mm. The cestode was found for the first time in larvae of 15 to 18 mm, and Caligus rapax in larvae of 20 to 25 mm total length.