PS 50-170 - Assessing the impact of residential shoreline development on aquatic macrophyte communities in Northern British Columbia with a novel methodology

Background/Question/Methods

Bednesti Lake and Berman Lake in Northern British Columbia have been facing an increase in amount and intensity of residential development. This study examined the impact of type of primary residence (i.e., year-round or seasonal occupation), shoreline vegetation removal, shoreline sediment replacement, bank reinforcement, distance from shore of primary residence, and length of shoreline disturbance, as well as common natural factors (e.g., natural sediment type and shore aspect), on the resulting community of macrophytes. By using waterproof Go-Pro cameras we were able to perform four transects at each of ninety sites over the span of five field days. Transects were performed from an aluminum boat with one boat operator who also measured depth, and one assistant who held a pole with two Go-Pro cameras attached. The use of these cameras allowed the footage to be reviewed immediately to ensure clarity and usability of the footage. Transects were performed from a depth of 0.5 m to a depth of 1.5 m. Presence-absence data was collected at the species level, so species richness was calculated using Chao 2. Logistic regression was used to calculate odd ratios of presence of aquatic macrophyte species.

Results/Conclusions

Significant correlations (α = 0.05) were found between the presence or absence of individual aquatic macrophyte species and several measured variables. Presence or absence was correlated to increasing lengths of disturbance along shoreline, increasing distance between shoreline and primary residential structure, whether or not the primary residential structure was a seasonal dwelling, presence of a lawn at shoreline, lake type (Berman or Bednesti Lake), substrate type of sample site, and the presence or absence of other aquatic macrophyte species. All aquatic macrophyte species that were significantly influenced by an anthropogenic disturbance also significantly influenced the presence of other aquatic macrophyte species. This indicated that while some species may not have been directly influenced by an anthropogenic disturbance, the influence upon one species will impact the entire aquatic macrophyte community. Species richness was not found to be significantly influenced by any predictor variable; however, presence-absence data is not considered as robust for species richness calculation as data that includes abundance. Future studies would be advised to include an abundance measurement. The efficiency of the methodology used in this study would be of great use in monitoring aquatic environments for invasive macrophyte species.