A NEW MONITORING TOOL: AUTOMATIC MEASUREMENTS FROM FERRY BOATS
Friedhelm Schroeder, Wilhelm Petersen, Michail Petschatnikov and Franciscus Colijn
GKSS Research Centre, Institute for Coastal Research
A new operational tool which uses ferry boats as carrier system for automated monitoring equipment has been developed. Such systems can be operated with much less costs than automatic buoys and have better performance with regard to bio-fouling. The "German FerryBox" consists of a fully automated flow-through system with sensors and automatic analyzers for the measurement of oceanographic and chemical parameters, among which are nutrients and algal properties. It provides the possibility of automatic cleaning cycles and position-controlled sampling (GPS). Data can be transferred to shore and the system can be remotely operated by mobile phone. The system has been installed on the ferry Hamburg-Harwich (U.K.) and is under test since November 2001. Results from recent measurements demonstrate the function and applicability of the ferry system.
General Monitoring Aspects
Since some decades the contamination of coastal waters with nutrients and toxic substances is of growing concern in European countries. For an assessment of the water quality of these regions operational monitoring programs had been implemented. In this context the main aims of water quality monitoring are:
・Preventing the potential danger to human health.
・Assessing the impact of anthropogenic substances on aquatic ecosystems.
・Documenting the present state of water pollution.
・Showing the efficiency of water protection measures by means of emission values.
In order to achieve these objectives mainly three different categories of monitoring are defined [EEA]:
・Statutory monitoring by which a state meets its legal obligations arising from EC and national legislation and international agreements.
・Surveillance monitoring through which a broad view and comparison of water resource quality and quantity can be obtained across a State (or across Europe). This type of monitoring is usually used to make spatial and temporal comparisons.
・Operational monitoring which is undertaken to meet the specific business and operational needs of the regulators or users of water. Examples might be the monitoring of specific discharges, clean-up campaigns on specific catchments or monitoring after pollution incidents.
Whereas in the last decades different approaches were used for monitoring of rivers and coastal areas the "European Water Framework Directive" which had been implemented in 2001 now points to an integrated assessment of whole watersheds [EEA]. This aspect is also followed in some running EU projects (e.g., the EUROCAT project: European catchments: Catchments changes and their impact on the coast).
There are three aspects of "integrated monitoring strategies" which are new in comparison to "conventional" monitoring:
1. Different physical, chemical and biological parameters have to be measured simultaneously in order to assess important processes which may influence the water quality.
2. Monitoring, i.e., sampling and in situ measurements, have to be carried out in a dense spatial and temporal grid. This implies that continuous (automatic) measuring stations have to be applied at strategic positions, e.g., river mouths, in order to monitor important short-term events, e.g., fresh water discharges (temporal dense time series). In order to assess spatial distributions (patchiness) remote sensing has to be taken into account, e.g., for algal distributions.
3. Due to high operational costs only few automatic stations can be operated. Therefore, numerical models (physical and ecological models) can be used for spatial and temporal "interpolations".
Another objective of monitoring is to use this as the basis for long-term ecological observations, which can be used as input for ecological models and to understand effects of global change on marine ecosystems.
Automatic Monitoring from buoys
Looking at the practical aspects of physical, chemical and biological monitoring
of rivers, coastal areas and shelf seas it is evident that operational monitoring is mainly carried out
by manual sampling during ship cruises and following analyses in the laboratory. In the "official" monitoring
programs for the North Sea this is carried out three to six times per year, which is not enough to observe
the spatial extensions of phenomena such as algal blooms, which have a typical random short time distribution.
Information about spatial distributions therefore is strongly hampered by a fixed station strategy. (Althuis
et al., 1994
). Whereas sampling is the only feasible method for counting biological species and the
analysis of trace contaminants, e.g., heavy metals or organic micro-pollutants, there are other, complementing
methods for the automatic unattended measurement of standard oceanographic parameters, e.g., temperature,
salinity, currents and in some cases other parameters, e.g., turbidity, oxygen, nutrients and chlorophyll
fluorescence. Mainly these automated measurements are carried out from different types of moored buoys
or other fixed marine stations (Hydes et al., 1998; Knauth
et al., 1996, 1997; Nies et al., 1999; Sanders
et al., 2001
Despite the many advantages of these operational systems from buoys among which are
・The assessment of short-term events (storms, fresh water discharge etc.).
・Production of consistent long-term time series with high temporal density.
There are also some serious disadvantages:
・Only point measurements.
・Often data gaps due to bio-fouling of sensors and maintenance difficulties due to difficult accessibility of stations during bad weather.
・High operational costs due to maintenance by ship cruises.
Automatic Monitoring from ships (Ferry Boats or Ships-of-opportunity)
There are many routes for ferryboats and "ships-of-opportunity" which run quite
frequently. Already 60 years ago the "Continuous Plankton Recorder (CPR)" (Reid
et al., 1998
) followed the idea of using scientific equipment on such ships for continuous recording
of environmental data. This method is now improved and shows an impressive data set of semi-quantitative
phytoplankton data over the world oceans (SAHFOS). Within the last years some more sophisticated systems
had been implemented on ferryboats, which allow more precise measurements of temperature, salinity and
chlorophyll (Althuis et al., 1994
et al., 1997; Harashima and Kunugi, 2000; Koske,
et al., 1998; Ridderinkhof et al., 1999; Swertz
et al., 1999
) and even continuously measurements of some nutrients (Holley
and Hydes, 2000
Applying such measuring systems on ferry boats or ships-of-opportunity has several advantages:
・The measuring system is protected against harsh environment, e.g., waves & currents etc.
・Bio-fouling can be more easily prevented due to inline sensors).
・No energy restrictions in contrast to buoys.
・Easier maintenance when ferry comes back "on one's doorstep".
・Much smaller running costs since the operation costs of the ship have not to be calculated.
・Instead of point measurements (buoys) transects yield much more information a sea area.
Within the GOOS (Global Ocean Observing System) and EuroGOOS Framework we have started initiatives to develop automatic measuring systems for bio-oceanographic parameters. As a measuring platform ferries on regular routes offer a cheap and reliable possibility to obtain regular observations on near surface water parameters. Present activities are both nationally and internationally EU funded.