Long Term Trophic Trends – A Look at 45 Years of Monitoring in Severn Sound

Session: 32. - Long-Term Monitoring: Achievements, Challenges, and Solutions

Aisha Chiandet, Severn Sound Env. Assoc., [email protected]
Keith Sherman, prev. Severn Sound, Environmental Association, [email protected]

Abstract

As a former Great Lakes Area of Concern initially listed due to eutrophication, Severn Sound has a long record of water quality monitoring. 2017 marked 45 years of biweekly data collection in the open waters during the ice-free period. Five locations have been consistently sampled - one in each bay of Severn Sound, and one in the open waters. In addition to physical measurements of Secchi depth, temperature and oxygen, nutrients, algae and zooplankton have also been sampled. Over this period, there have been some changes in sample collection and analysis methods, the implications of which will be discussed. Trends were analyzed using the non-parametric Mann-Kendall trend test. Trends will be discussed in relation to changes in watershed management (e.g. point and non-point source nutrient load reduction) as well as environmental changes (e.g. dreissenid mussel infestation, water level fluctuations). Key trends include a reduction in total phosphorus and algal biovolume, a shift in water clarity following mussel colonization, and an increase in nitrate in bays with higher surrounding population density.

1. Keyword
nutrients

2. Keyword
algae

3. Keyword
monitoring

4. Additional Keyword
long term trends

5. Additional Keyword
Severn Sound

6. Additional Keyword
Georgian Bay