Pulp and paper technical guidance: criteria and guidance for pronounced eutrophication, chapter 5

Site Specificity and Confounding Factors (Historical Effects)

For mills showing possible eutrophication, more information/consultation could be needed before it can be decided if benthic studies at these locations indicate pronounced eutrophication. Cycle 4 results may help to classify mills with effects shown in one cycle. Mills may also possess information other than EEM study results, which demonstrate eutrophic responses in the receiving environment. Furthermore, certain site-specific, confounding factors may influence the identification of eutrophication at a mill. Final decisions will be made based on consultation with regional offices and the stakeholders.

Some mills have experienced significant accumulations of organic matter in the form of fibre mats. In such circumstances, although the present EEM surveys are showing changes to the benthic invertebrate community, what is actually measured is the recovery from more or less pronounced historical effects. In such cases, EEM results may reflect the recovery from a historical deposition, not the effects of current effluent and therefore future EEM surveys should continue to consider the impact of historical deposits. This should also be taken into consideration during the design and review of EEM studies and methods developed to differentiate between these two situations. Since the causes of eutrophication effects may be very site-specific, investigation of causes and solutions could also be site-specific.