Background & Rational Peatland disturbance due to climate change and resource extraction destabilizes peatland ecosystems and alters the flow of carbon (C) and nutrients (nitrogen (N) and phosphorous (P)) to inland waters [1, 2]. Northern peatlands comprise 80% of global peatland area and contain approximately 415 Pg C, 10 Pg N, and 0.3 Pg P [3–5]. Pristine peatlands naturally contribute disproportionate amounts of dissolved organic matter (DOM) compared to other ecosystems, and disturbance can further increase DOM export and contribute inorganic nutrients to inland waters. The increased aquatic export of C and nutrients from disturbed peatlands could result in water brownification [6, 7] and eutrophication [8], both of which kill aquatic life, harm local economies, threaten human health, and endanger water security [9]. Efforts to understand the influence of peatland disturbance on downstream water quality are complicated by complex biogeochemical conditions and heterogeneous landscapes. For example, industrial peat extraction may contribute elevated concentrations of DOM and ammonium, but so do neighboring agricultural fields and forestry operations that often occur within the same watershed [10,11] (e.g., Figure 1).
Peatland disturbance often removes vegetation and alters the water table (e.g., drainage or flooding) which changes hydrological flowpaths and disrupts natural C and nutrient cycles. In this study, I will look at C and nutrient concentrations in watersheds affected by peat harvesting in central Alberta. In order to protect aquatic communities, dissolved inorganic nitrogen (DIN) concentrations need to be kept below 2.95 mg/L and total P (TP) needs to be kept below 0.10 mg/L. To maintain aquatic health and suitability for drinking water, DOC levels should be kept below 7.90 mg/L. Peat harvesting may exceed these levels because to harvest peat, vegetation is removed and drainage ditches are dug to artificially lower the water table to allow the exposed to dry. Dried peat is then vacuum harvested from the surface which removes the top few centimeters and the process repeats. Because of the lowered water table and removal of vegetation, this process could lead to greater loss of DOC and dissolved inorganic N (DIN) due to the oxidation of deep peat organic matter that was previously protected by waterlogged conditions [11, 12]. However, P is tightly cycled in the upper peat layers of pristine peatlands and it is uncertain whether harvesting removes those layers [5, 13]. Therefore, this study will measure water quality in watersheds draining harvested peatlands from the headwaters to the catchment outlet to understand the potential downstream impacts. |
Fig. 2 Conceptual diagram of the differences in dissolved organic matter (DOM) export between pristine peatlands (a) and disturbed peatlands (b) and the impact on water quality in mixed-use landscapes.
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Research Questions
- How does peatland disturbance influence catchment DOC and nutrient concentrations from disturbed headwaters to the catchment outlet?
- How does peat harvesting compare to other land-uses in catchments with regards to DOC and nutrient concentrations?
Expected ResultsI expect that DOC and N from disturbed peatlands will be elevated compared to pristine peatlands because of artificially lowered water tables and increased oxidation of deep peat organic matter. However, it could be that deep peat is recalcitrant and resistant to degradation. In this case, I would see less of an increase in DOC and N in streams draining disturbed peatlands. On the other hand, there could be other factors that control DOC and N export that are more important than land cover.
P is a different story because P is tightly cycled in the upper layers of pristine peatlands. In theory, much of this P is removed during harvesting, and so I expect P export to be comparable between disturbed and pristine sites. If P is higher in disturbed peatlands, then this could be indicative that not as much of the upper peat layers were removed as previously thought. These results will help me determine if land cover is an important factor in DOC, N, and P export or if other factors play a greater role. |
Fig. 3 Photo of an algal bloom in the drainage ditch of a harvested peatland near Seba Beach, AB.
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