COST 832

Quantification of the Agricultural Contribution to Eutrophication.

Minutes of the 1st Meeting of Working Group 4

"Impact of Diffused Phosphorus on Water Quality"

Greenmount College, Antrim UK, 15 - 16 June 1998.


Particip ants



























Van Liere







United Kingdom



United Kingdom




Monday 15th June




Plenary session-Introduction to COST Action 832 by the President, Paul Withers


Working group session 1


-Technical aspects of the WG4 by the co-ordinator, S. Orfanidis


-Introduction of participants


Working group session 2-discussion on three different topics


-Fate of P in waters (introduction by P. Boers)


-Bioavailability of P (introduction by P. Ekholm)


-Methods for estimating the impact of P in coastal waters (introduction by S. Orfanidis)


Tuesday 16th June



Working group session3-development of workplans


Plenary session-presentation of workplans by the co-ordinators, final discussions


Working Group 4, Session 1

The participants in Working Group 4 each delivered a short introductory account of their particular research expertise. The complex dynamics of different forms of phosphorus in water and the impact of these on aquatic ecosystems were discussed.

The group discussed phosphorus spiraling in rivers; feedback mechanisms from river and lake sediments; phosphorus reduction responses; phosphorus flows through sediments, plants and fish; and the development of models for P retention in canal feeder ditches in the Netherlands.

The bioavailability of different phosphorus forms was discussed and a difficulty regarding the standardization of bioassay methodologies was identified. Statistical correlation's between physico-chemical and biological factors leading to the formulation of phosphorus criteria for salmonid waters in Ireland were described.

Biological responses to nutrient load manipulation in an Italian lagoon were described. The compilation of a comprehensive database of chemical and biological indicators for rivers in north central Spain and attempts to utilize macrophyte species to control eutrophication in that country were outlined. The group was advised of the significant contribution of agriculture to eutrophication in Finland and the blue green algae problems, which exist in lakes now also, extend to the Baltic Sea.

The group heard how tourism contributed significantly to eutrophication problems in Austria in the 1960s but restoration measures have successfully restored many waters to oligotrophic status.

The complexity of defining impacts and threshold levels for flowing waters at headwaters, lowland reaches, estuaries and the sea was described. It was agreed this is a universal problem. Furthermore it was generally agreed that ecologically waters respond in a stepwise fashion to nutrient loading as thresholds for different biological communities are exceeded. The possibility of establishing a single critical level for phosphate with Europe-wide application appears remote, having regard to the wide range of impacted waters from mildly enriched to hyper-eutrophic which currently exist. This concept may apply to each category of water fresh (river, lakes) and saline (estuaries/lagoons and full seawater).

Having regard to the achievable, desirable and potential, responses to nutrient reduction measures it may be more meaningful, using ecological quality objectives, to set out a range of phosphorus criteria for each water type. Very low phosphorus concentrations necessary for salmonid rivers and lakes will be extraordinarily difficult to achieve in some hyper-eutrophic systems in Continental Europe. Indeed this may be impractical and unnecessary in many waters. Furthermore, critical loads to them or concentrations within are also affected by non-agricultural activities. In addition climatic influences across Europe will influence ecological responses to discreet nutrient levels.

It was considered that separate issues arise in respect of rivers, lakes, estuaries and the sea. Few participants had expertise in the marine area and it was hoped that delegates from other countries who did not attend might be able to help in this aspect. It was also recognized that it would be essential to take cognizance of the proposed EU Framework Directive on Water Policy and to work within this.


Working Group 4, Session 2

Three short presentations were given.

(1) The Fate of Phosphorus in Freshwater was described by P. Boers. This included TP and Chlorophyll correlation in cyanobacteria (blue green algal) blooms, biodiversity loss, increased turbidity; covered the basic components of phosphate chemistry and relevant biological and chemical processes; phosphorus "pools" in lakes and sediment/water exchange mechanisms; microbiological, chemical and transport mechanisms of phosphorus in sediments. While Dutch lakes retain up to of the external loading, internal loading from sediments is also possible in summer and in this way winter particulate P inputs may be remobilize in summer. He showed the implications of TP for water management and a small table of items of significance for Cost 832.

(2) The bioavailability of Agricultural sourced Phosphorus was described by P. Ekholm. He described rapid planktonic uptake of dissolved orthophosphate but published studies suggest that the mean availability of particulate P varies from 4% in Finland to 30% Norway and 40% Sweden. It was evident from these studies that intercalibration of methodologies for bioassay was necessary. Unfiltered phosphorus was not a good indicator of bioaccumulation in Finland. Discussion followed on other factors influencing such as the physiological state of cells used in bioassay, the nutrient state of the innoculam and differential uptake by different algae used in assay.

(3) Methods for estimating the impact of P in Coastal Waters were introduced by S. Orfanidis. Monitoring the community structure of macro algae in small test areas can be used to assess species composition; frequency of occurrence; extent of coverage; biomass and spatial distribution. Impact on the community functions can be assessed using field enclosures, bags, bell jars, nets, etc. There is an urgent need to identify bio-indicators for coastal waters. How to ascertain the status of the community before disturbance occurred will be difficult, especially in the North European coasts.

Discussions followed on the composition of the macro-invertebrates communities as eutrophication indicators such as is evident in Irish rivers where difficulties exist for some sensitive species (stoneflies) even before problems develop due to diurnal variation in oxygen. Ongoing work by the EA in UK of a macrophyte bio-indicator system for freshwater was referred to. However, a disadvantage with bio-indicators is separating impacts due to other substances from those resulting from eutrophication.


Working Group 4, Session 3

On Tuesday morning discussion centered on the development of work plans for WG4. The complexity of the phosphorus cycle was evident because of the number of other relevant studies, which should be considered, and monitored e.g. Eurowater network; Harp Workshop; OSPAR / PARCOM. Mention was made also of a monograph on eutrophication which is being compiled by WRC and NERI for the European Environment Agency. It is understood that the proposal is to establish pristine/high ecological quality using hind casting and this will be compared with the current load.

On the question of Bioavailability, istinction must be made between potential and actual and the interrogation of existing databases would be essential.

The initial impacts of phosphorus inputs are localised but extend due to the spiralling of phosphorus along a system from headwaters through lowlands, the estuary and the sea. It will be important to consider stream ordinancing regarding the impacts of agricultural P on aquatic ecosystems. It was suggested that a small group might be formed to review, collect and collate available information. Reference was made to "SCOPE" a UNESCO review of the subject.

It was decided that each participant should compile 1 or 2 paragraphs to put a document together for circulation by way of information. A small organizing committee should meet to synthesize the documentation in order to get a key agenda together for the Working Group. Such a group would be necessary to even define the sets of data quantitative or otherwise submitted by people.

It is accepted that gaps exist in our knowledge of impact data for estuaries and coastal waters and different critical levels of phosphorus and/or nitrogen which may apply in these systems.

There was a general acceptance of a stepwise approach and critical levels / loads for specific water types and uses. At the post plenary session mention was made of eutrophication of Fen ecosystems receiving ground water, which is a problem in Belgium and perhaps elsewhere.


Objectives of the Working Group 4

The main objective of the WG4 "Impacts of diffused phosphorus on water quality" is to identify potential methodologies for quantifying the impact of agriculturally-derived phosphorus on water quality. This objective will be achieved by comparing existing and new methodologies for measuring different forms of transported phosphorus, the bioavailability of the different forms and the potential impacts on aquatic organisms. The feasibility of developing a unified approach to assessing impacts on different water bodies will be investigated.

WG4 have discussed the main objective and have identified two topics to meet the objective.

a) Fate of agricultural derived P in the water, with particular reference to the aspects of:

- different forms of P

- bioavailability of diffused P in the water

Goal: presentation of a model and test existing and new methodologies.


b) Critical loads/levels and impact of P in different aquatic ecosystems, in order to avoid proliferation of micro- and macro-algae, with particular reference to the aspects of:

- P concentrations / loads

- bio-indicators of eutrophication (e.g. macro-algae)

It is concluded that the study of critical levels/loads and P impact be carried out separately for the various types of water bodies of interest, namely: rivers, deep lakes, shallow lakes (fresh water), lagoons and coastal seas (salt water). Also, although the Action is concerned with agricultural derived P, it is recommended that not only this kind of P be considered when estimating the critical loads.

Goal: presentation of a model and test existing and new methodologies.

Due to the absence of a significant part of the work group members (about 50 %), the results of the present discussion can be modified to a certain extent to include specific issues from the absent members.


Place and date of next meetings and workshops

WG4 decided the following meetings for the years 1998-2000.

1. A small (5 persons) meeting is planned for the middle of October 1998 to be held in Kavala (Greece) in order to prepare the next working group meeting to be held in Aberdeen (UK) in November or December 1998. Participants: S. Orfanidis (local organizer), Paul Boers, T. Edwards, S. Leaf, T. Champ, M. McCarrigle.

2. A Working Group meeting is proposed for the November or December 1998 to be held in Aberdeen (UK) in order to discuss the working plan of WG4 in more details. Local organizer T. Edwards.

3. A Working Group meeting is proposed for the spring 1999 to be held in Finland in order to discuss the bioavailability of diffused P in the water. Local organizer P. Ekholm.

4. A Working Group meeting is proposed for the spring 2000 to be held in Greece on the bio-indicators of eutrophication in the water. Local organizers S. Orfanidis, N. Stamatis.

5. A Working Group meeting is proposed for the autumn 2000 to be held in The Netherlands on desired P levels in aquatic systems. Local organizers Paul Boers, L. van Liere.


T. Champ, Assistant Secretary
A. Balzano, Secretary
S. Orfanidis, Coordinator.