NWT RESEARCH DATABASE

Regions: Inuvialuit Settlement Region

Tags: lake productivity, aquatic plants, flooding, hydrological processes, delta floodplain, ecosystem model

Objective(s): Flooding and annual delivery of nutrient rich sediments are perceived to control the productivity of lakes and wetlands associated with the floodplains and deltas of major world rivers. However, there remains limited understanding of hydrologic & biogeochemical interactions between large rivers and lakes within their floodplains, and limited appreciation of their important ecological roles. Least understood are north-flowing ice-covered rivers. If we are to anticipate potential changes to these ecosystems resulting from economic development or from global warming our basic understanding of these systems must be improved. The long-term goal of this research is to develop a model for lakes in the Mackenzie Delta, and ultimately, a more general ecosystem model for lakes in the floodplains & deltas of major world rivers that could help assess the effects of multiple stresses on rivers as a result of global change. and primary productivity of lakes in the Mackenzie Delta region, and ultimately, a more general model for lakes associated with the floodplains and deltas of major world rivers. The shorter range goal is to identify & develop models of critical interlinkages between biogeochemical and hydrologic processes that are important to the ecological characteristics of the Mackenzie Delta Lakes. Specific goals for this field season are provided in the non-technical summary of NWT activities.

Project Description: There are two specific goals for this field season. 1) Evaluation of distributions of aquatic plants & their relation to water clarity and flooding among a set of lakes that range from non-transparent to relatively transparent. This study will improve our understanding of how changes in the delta sedimentation regime could affect the amount of plant growth at the base of the aquatic food chain. The work will be based at the Inuvik Research Centre and will consist of field and laboratory components primarily focused on six to nine small lakes in the Mackenzie Delta just to the north of Inuvik along East Channel. The work will involve mapping distributions of aquatic plants at the lakes, collecting samples of aquatic plants from these lakes about every two weeks, and bringing the samples to Inuvik for laboratory-based measurements of growth rates under similar conditions. 2) Evaluation of how changes in ultraviolet (UV) light affects dissolved organic carbon (DOC) levels and growth of bacteria in Mackenzie Delta lakes. DOC is the main source of water color in this system and is also a natural sunscreen for UV light. This investigation is needed to improve our understanding of how changes in ozone levels in the arctic atmosphere could affect the amount of plant growth at the base of the aquatic food chain in the Mackenzie Delta. Field and lab work will focus mainly on one small lake in the Mackenzie Delta near Inuvik (South Lake). The work will involve measuring how bacteria communities and DOC levels change in response to differing levels of UV light. To achieve this, we proposed to set up a series of enclosures (large plastic bags) in the lake which will have differing transparencies to UV light, and we will add different amounts of DOC to mimic the range of concentrations naturally found in waters across the delta. We will examine levels of DOC and bacteria among lakes with differing levels of suspended sediments by surveying a set of 40 delta lakes near Inuvik late in the summer.