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Location: Fraser Valley, Cultus Lake Project Summary
SUMMARY Initiate a nutrient monitoring program to develop a watershed loading model and identify sources of nutrients to Cultus Lake, with the ultimate goal of developing a nutrient abatement and management strategy with management authorities to protect endangered sockeye salmon rearing habitat. The project includes First Nations and Community engagement, training, and capacity building along with public outreach. DESCRIPTION Ongoing research has established that Cultus Lake is undergoing cultural eutrophication, the enrichment of nutrients (phosphorus and nitrogen) resulting from human activities within the watershed. Available evidence indicates this nutrient loading is rapidly degrading the Cultus aquatic ecosystem, which is the only freshwater nursery habitat for a genetically distinct, low-abundance population of sockeye salmon (Oncorhynchus nerka), listed as endangered in 2002 by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC 2003). Additionally, Cultus Lake hosts an endemic and unique, SARA-listed, threatened species, the Cultus Pygmy Sculpin, that faces similar freshwater stressors. Cultus Lake is also a prized recreation destination located near Vancouver, logging 3 million visitors annually (FVRD traffic counts, 2009). The Cultus Lake Planning Strategy (FSWP funded project in 2010) has identified that nutrient loading is not only a serious ecological issue, but a significant social concern for both residents and users of the watershed, as population densities and development continue to increase. A critical willingness to tackle nutrient abatement amongst diverse user groups exists, making now the time to capitalize upon social inertia, volunteerism, and engaged scientific expertise, to establish a comprehensive nutrient budget that identifies the fluxes and major sources of nutrients to Cultus Lake. The decline in Cultus Lake sockeye salmon has been attributed to several external factors including over-exploitation in mixed-stock fisheries, poor marine survivals, and parasite-induced pre-spawn mortality (CSRT 2009). With depressed spawning numbers, and hatchery supplementation measures underway (but being scaled back), habitat quality becomes very important to the persistence of Cultus Lake sockeye salmon (CSRT 2009). In our work, we propose to monitor the tributaries to Cultus Lake and its outlet (Sweltzer Creek) to assess the major temporal and spatial trends in inter- and intra-annual nutrient loading. This work compliments ongoing lake monitoring by DFO (Cultus Lake Salmon Research Laboratory). Furthermore, by capturing the majority of surface nutrient loading to Cultus Lake, in conjunction with ongoing nutrient monitoring in the lake, we can assess the general importance of diffuse sources (e.g. bird guano, groundwater discharge). We also propose to analyze paired near-shore soil (porewater) and lake water samples for nutrients and bacteria (fecal coliforms, E. coli) in both residential and non-residential areas to identify the likelihood of septic leachate reaching Cultus Lake. Ultimately, the data generated from this project will be useful in the development and refinement of planning strategies for land use and nutrient management in the Cultus Lake watershed. Our approach is consistent with the recommendations of the Cultus Sockeye Recovery Team (2009), in that it targets sound scientific evidence necessary for the mitigation of freshwater habitat degradation, and promotes stewardship and public awareness through volunteer stakeholder engagement in on-the-ground in sample collection and consultation. Our intention to partner with government agencies (DFO Science Branch; local and provincial government officials and residents (incl. First Nations) will aid in quality sample processing, data analysis, and interpretation. Our project contributes to the Fraser Salmon and Watersheds Program foci of governance, broad community involvement and First Nations engagement. It supports the protection, enhancement and rehabilitation of Pacific salmonids and their habitat.
METHODS To capture the major temporal and spatial patterns in annual nutrient loading to Cultus Lake BC, we propose to collect water chemistry samples and hydrological measurements on the major inlets and the outlet of Cultus Lake (Fig. 5) over the course of two years (first year funded by FSWP). Stream sampling will be conducted twice monthly with replicate analyses of total dissolved (TDP) and soluble reactive phosphorus (SRP), ammonium (NH4+), nitrate/nitrite (NO3-/NO2-), and dissolved organic nitrogen (DON) to quantify seasonal and watershed-specific nutrient export in the major tributaries to Cultus Lake. Stream staff gauges and flow measurements will be used to calculate discharge. Where appropriate and secure sampling sites are available, auto-samplers and flow sensors on loan from DFO will be installed to better quantify stream discharge-nutrient relationships with high-resolution sampling. Similar methods will be used on the Sweltzer Creek outlet stream. A weather station installed at the DFO Cultus Lake Salmon Research Laboratory will provide daily precipitation data and rainfall nutrient samples to calculate atmospheric loading to Cultus Lake. Avian nutrient inputs to Cultus Lake will be assessed using known guano excretion rates and nutrient concentrations for herring gulls and Canada geese. Enumeration of bird colonies will be conducted under the guidance of the Canadian Wildlife Service of Environment Canada. All field locations are readily accessible by road or boat. All field equipment (water chemistry, hydrology) will be supplied by DFO’s Lakes Research and Fish-Forestry programs. All sample collection and preparatory processing (e.g. filtering) will be conducted by DFO technical staff and the SFU graduate student following standard methods. Nutrient analyses will be conducted at the DFO Low-Level Nutrient Chemistry Laboratory located at the Cultus Lake Salmon Research Laboratory. Data analysis and report writing will be led by the SFU graduate student, as part of thesis research, and will be supervised by DFO/SFU research personnel. It is anticipated that the data and analyses generated in this project will be published in primary research publications and used in future ecosystem-based studies Cultus Lake. The contributions of the FSWP will be acknowledged in all publications and media relations concerning this work. All publications will be distributed to the FSWP, relevant municipal, provincial and federal regulatory agencies, and interested stakeholders. The success factors of community engagement include environmental, inclusion, good process/structure, communication, purpose, and resources. CLASS has an excellent track record of bringing people together and bringing the human element to the science so we are all engaged in caring for Cultus Lake. BENEFITS Cultus Lake sockeye salmon have declined to a relict population (CSRT 2009; Figs. 1 & 4), and the pressures on the Cultus watershed have grown substantially over the past several decades. Given the prized recreation opportunities within the system, and projected increases to the population base within the lower Mainland (Fig. 6), nutrient pressures on Cultus are likely to continue to increase along a similar trajectory evidenced in the paleolimnological record (Fig. 1). Moreover, this project will bring awareness and build capacity within an increasingly engaged community struggling with environmental stewardship. By integrating the science with community involvement, and the ongoing Cultus Planning Strategy, we put the focus on sustainability for the Cultus watershed.
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