Franciscus Colijn

Time series analysis of monthly mean data of temperature, salinity, nutrients, suspended matter, phyto- and zooplankton at eight locations on the northwest european shelf

In this study an overview is given of the time series analysis of monthly mean data of physical, chemical and biological parameters. The time series are available at eight locations on the Northwest European Shelf. The integrated evaluation of those time series gives the opportunity to look for connections between the different parts of the shelf. Temperature and salinity seem to be externally forced. For the nutrients and biological parameters the local forcing is dominating the time series. It is concluded that there are areas that are comparable to each other (freshwater dominated boxes along the Belgian and Dutch coasts and German Bight; Atlantic dominated boxes in the English Channel and off the Scottish coast), although significant cross-correlations are hardly found. The Irish Sea can be regarded as a separate ecosystem.

Comparison of changes in the annual variability of the seasonal cycles of chlorophyll, nutrients and zooplankton at eight locations on the northwest european continental shelf (1960–1994)

Mean seasonal cycles in time series of salinity, nutrients, chlorophyll and Zooplankton at 8 locations on the Northwest-European shelf were analysed in relation to each other and with respect to their timing and magnitude during a period most of the time series overlap (1980–1984). A relatively late spring bloom in April/May with low chlorophyll values (2–4 mg/m3) is observed in the Irish Sea, off the Scottish east coast and the Channel entrance. An early spring bloom in March/April and relatively high chlorophyll values (7–12 mg/m3) are found in the Southern Bight of the North Sea and in the Skagerrak, whereas a late spring bloom in April/May with chlorophyll concentrations of about 23 mg/m3 is found along the Dutch and Belgian coast. The peak of the phytoplankton carbon cycle in the German Bight (Helgoland) occurs during summer. This is caused by the dominance of large dinoflagellates in this period. The peak in the yearly abundance of copepods shifts from May-June in the south to July-August in the north of the shelf. In the Irish Sea and the Channel entrance two seasonal copepods peaks are observed. The January nitrate values in Irish Sea, the Southern Bight and the Skagerrak are, compared to the Atlantic input signal represented by the data from the Channel entrance and east of Scotland, about 20% higher. The values of dissolved inorganic phosphate in January are comparable to those of the Atlantic input signal. However, the Irish Sea forms an exception, here the level is increased by 10–20%. The January values for nitrate and dissolved inorganic phosphate at the Dutch and Belgium coast are about 10 and 4, and in the German Bight (Helgoland) 4 and 3 times higher then the Atlantic input signal. At most sites changes in the seasonal cycles of chlorophyll coincide with changes in nutrient concentrations, whereas the maximum level of the seasonal signal of chlorophyll is related to nutrient levels.

The NOWESP research data base

In the NOWESP project historical data from the Northwest European Shelf were compiled and evaluated to estimate the variability and trends in water movements, concentrations of dissolved and particulate constituents, and fluxes of the relevant substances across the shelf. As an integral part of the project, the NOWESP Research Data Base was created as a research tool to provide the data and data products needed for the analyses within the project. The tasks of the NOWESP Research Data Base group were the acquisition of the relevant data sets, with the intensive support of all partners, organization of the data sets in the NOWESP Research Data Base, merging of the specific data sets for the ten main state variables used in NOWESP, and the provision of data products for analysis within NOWESP. The data compiled during NOWESP represent a unique data set for the Northwest European Shelf. The data set is sufficiently comprehensive to allow the definition of long time series at about 14 sites in eight areas. It further enables the derivation of mean annual cycles of horizontal distributions of nine main state variables. NOWESP thus has provided valuable data sets for estimating budgets and fluxes across the shelf and, in addition, important data sets for the forcing and validation of ecological shelf sea models. An overview of the NOWESP data set is given. The organization of the data base is described in some detail, and examples of the products obtained for NOWESP are displayed.

Defining a good ecological status of coastal waters — a case study for the Elbe plume

The definition of a good ecological status of coastal waters requires a close cooperation between sciences (natural and socio-economic) and decision makers. An argument is presented for the use of ecosystem integrity assessment based on indicators of function and state. Ecosystem integrity is understood to be reflected in exergy capture (here expressed as net primary production), storage capacity (as nutrient input/outut balances for coastal sediments), cycling (turn-over of winter nutrient stocks), matter losses (into adjacent water), and heterogeneity (here the diatom/non-diatom ratio of planktonic algae is used). Its feasibility is assessed using ERSEM, an ecosystem model of the North Sea, for the Elbe plume, after prior satisfactory calibration. Three scenarios were applied corresponding to 80, 70 and 60% reduction of the riverine nutrient load into the German Bight, compared to a reference situation of 1995. The modelling effort suggested that drastic nutrient load reduction from the Elbe alone would have a limited effect on the larger German Bight: even a 60% reduction scenario would only lead to moderate changes in all five indicators. In conclusion, application of functional integrity indicators appears feasible for coastal seas at larger spatial scales (i.e. the German Bight), and, for the coast, would form a useful addition to the indicators presently proposed in the Water Framework Directive (WFD).

North-West European shelf programme (Nowesp): An overview

A concise overview is given of the North-West European Shelf Programme (NOWESP), concentrating on the philosophy of the project and the coherency of the various contributions to reach the objectives of the project. A short reference is made to all papers, mentioning the new findings. Recommendations for future management of large data sets and for future shelf research are made.

The use of ecological risk for assessing effects of human activities an example including eutrophication and offshore wind farm construction in the North Sea

This paper takes the move from the uncertainty surrounding ecosystem thresholds and addresses the issue of ecosystem-state assessment by means of ecological integrity indicators and ‘ecological risk‘. The concept of ‘ecological risk‘ gives a measure of the likelihood of ecosystem failure to provide the level of natural ecological goods and services expected/desired by human societies. As a consequence of human pressures (use of resources and discharge into the environment), ecosystem thresholds can be breached thus resulting in major threats to human health, safety and well-being. In this study we apply the concept of ‘ecological risk‘ to two case-studies in the German exclusive economic zone: eutrophication and construction of offshore wind farms. The effects of different future scenarios for single-uses upon ecosystem integrity are analysed as well as the effects of one combined scenario. We conclude that in the short term construction of offshore wind farms can influence some processes to a much larger degree than eutrophication, however, combined impacts deriving from eutrophication and offshore wind farm construction need a more detailed analysis. Due to non-linear ecosystem processes, effects of combined or multiple uses of marine resources in terms of ‘ecological risk‘, cannot be extrapolated from single-use scenarios.

Future observational and modelling needs identified on the basis of the existing shelf data

NOWESP has compiled a vast quantity of existing data from the north-west European shelf. Such a focused task is without precedence. It is now highly recommended that one, or a few national and international data centres or agencies should be chosen and properly supported by the E. U., where all available observational data, incl. the NOWESP data, are collected, stored, regularly updated by the providers of the data, and made available to the researchers. International agreement must be reached on the quality control procedures and quality standards for data to be stored in these data bases. Proper arrangements should be made to preserve the economic value of the data for their “owners” without compromising use of the data by researchers or duplicating data collecting efforts.