Responses of different taxonomic groups to human stressors are expected to contrast, depending on their overall sensitivity and resilience to stress. For example, according to basic ecological principles, phytoplankton and benthic diatoms (ie: primary producers) should respond more rapidly to changes in nutrient concentrations than secondary or tertiary consumers, such as benthic invertebrates or fish.
In the latest revision of environmental classification criteria, limited effort was focused on assessing the response of different organism groups to similar pressures. The main objectives of this work package are to (1) design a robust field assessment of indicator response to selected pressures and (2) to evaluate the precision and sensitivity of different taxonomic groups and functional response variables to selected pressures. This knowledge will be used to better our understanding of stress-response relationships and, subsequently, how this information can be used to design more robust management programs. In addition, data from the field study will be used to validate current classification criteria, and, if necessary, develop and calibrate new pollution-specific metrics.
Three types of stresses will be focussed on, representing important categories of human impact in Sweden: (1) “Nutrient enrichment”, (2) “Hydromorphological alteration” and (3) “Forestry”. Each stressor will be studied in the region and ecosystem type where the expected effects are strongest: Nutrient enrichment will be studied in agricultural regions in middle-south Sweden, in both lakes and streams, whereas forestry will be studied in Norrland. Hydromorphological alteration will be studied in both the north and south, representing the pervasive extent of this impact, though the specific impact may differ (eg: a focus on agricultural channelization in the south and hydropower dams in the north).
For each gradient in each region 9-11 sites will be sampled, with 3-5 reference sites of high to good ecological status, and the remainder representing an increasing gradient of degredation. At each site fish, benthic invertebrates, macrophytes and benthic diatoms/phytoplankton (lakes only) will be sampled during the same year, as will supporting physico-chemical data (water chemistry, habitat characterisation, etc.)
A PhD student linked with WATERS will additionally measure multiple functional response variables in the gradient study streams. Functional variables are direct measures of ecosystem processes, such as algal growth, leaf decomposition, and nutrient uptake, which underpin the delivery of ecosystem services (eg: clean water, food) from streams. Along perturbation gradients, functional response variables provide an additional measure of environmental impact. Specifically, such variables provide a direct measure of how an ecosystem is working (efficiency of nutrient and energy use), as opposed to their community structure (diversity and composition of different taxonomic groups). Functional response variables provide an additional means of validating taxonomic indicators. A key question is whether functional and taxonomic indicators respond with more, less, or equally sensitivity across the gradients.
