Summer recreational boating impacts on erosion, turbidity, and phosphorus levels in Canadian freshwater lakes

Abstract

Increases in boat traffic over time can present a risk to the integrity of aquatic ecosystems. In addition to severe environmental degradation or boat-related disturbances, boat wave’s kinetic energy can induce a cumulative impact on freshwater ecosystems. However, seldom data report the impacts of boat waves on shoreline erosion and physico-chemical properties on freshwater lakes. In this study, we monitored shoreline erosion, turbidity, and total phosphorus levels. Wave-induced shoreline erosion was measured through shoreline rebar pin excavation across five lakes in southern Quebec. Sediment resuspension was measured through turbidity sampling in Lake Massawippi over three years. Total phosphorus was also monitored for potential impacts of sediment resuspension. Our study did not detect significant shoreline erosion. However, water turbidity was positively correlated with boat traffic and wind speed and negatively with the littoral slope angle. Moreover, water total phosphorus levels were positively correlated with turbidity. Thus, despite a lack of detectible impact on the shoreline, our results suggest that boat waves can have an impact on freshwater lakes with an increase in sediment resuspension and phosphorus availability. Management agencies could therefore benefit in the long-term from implementing or reinforcing policies aiming to minimize the impact of boats on sediment resuspension.

RESUMÉ

L’accroissement du trafic nautique représente un risque pour l‘intégrité des écosystèmes aquatiques. Parmi différentes perturbations possibles se trouve l’impact cumulatif de l’énergie cinétique des vagues sur le littoral, notamment via l‘érosion des rives et la remise en suspension des sédiments qui peut modifier la physico-chimie des lacs d’eau douce. La présente étude pallie au manque de données sur le sujet en mesurant l‘érosion des rives, la turbidité et le phosphore total dans des lacs sujets au nautisme récréatif. L'érosion a été mesurée dans cinq lacs du sud du Québec par l’excavation de tiges de métal partiellement enfouies. La remise en suspension des sédiments a été évaluée dans le lac Massawippi, sur trois ans, par la mesure de la turbidité en eau peu profonde. Le phosphore total de l’eau a été analysé en parallèle pour identifier des impacts potentiels de la remise en suspension. Aucune érosion des rives n’a été mesurée. En revanche, la turbidité s’est avérée corrélée positivement au trafic et à la vitesse du vent et inversement corrélée à la pente du littoral. Aussi, le phosphore total était positivement corrélé à la turbidité. Ainsi, malgré l’absence d’impact détectable sur les berges, les vagues de bateaux semblent induire la remise en suspension des sédiments et augmenter la disponibilité en phosphore dans les lacs d’eau douce. Les gestionnaires du territoire pourraient donc bénéficier à long terme de la mise en œuvre ou du renforcement de politiques visant à minimiser l'impact des bateaux sur la remise en suspension des sédiments.

KEY POLICY HIGHLIGHTS

• No evidence was found that summer boating causes significant erosion on freshwater lake shorelines.

• Rather, boating seems to resuspend sediments in shallow areas, increasing turbidity and total phosphorus levels.

• These results were obtained in lakes with shoreline speed limit buffers (100 m and 10 km h⁻¹).

Keywords:

• Boating
• erosion
• sediment resuspension
• turbidity
• phosphorus
• lake

Acknowledgements

We are grateful to the lake residents who allowed us to install a camera on their shoreline. We thank Pr Alexander Forrest and two anonymous reviewers for their comments on the manuscript. We thank all students and summer employees who have helped us collect data in the field.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Datasets are currently available upon reasonable request. Requests should be sent to [email protected]. Blue Massawippi intends to make the datasets publicly available upon publication.

Additional information

Funding

This research was mainly funded by a grant to Blue Massawippi from Transport Canada, through the Boating Safety Contribution Program (project number 166389). Funding was completed with private donations to Blue Massawippi. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.