Presentation on theme: "Assessing Ecological Changes in Freshwaters using Statistical Models Claire Ferguson Adrian Bowman, Marian Scott Laurence Carvalho (CEH, Edinburgh)"— Presentation transcript:
Assessing Ecological Changes in Freshwaters using Statistical Models Claire Ferguson Adrian Bowman, Marian Scott Laurence Carvalho (CEH, Edinburgh) A Case Study of Loch Leven
Loch Leven Dataset Length of dataset: variables measured, covering… Physics Lake chemistry Lake biology Weather Sampling frequency: weekly to monthly Gaps in data: 1984,
Loch Leven – Trends trend – a pattern in the long run average over time
Loch Leven – Seasonality seasonality – a yearly cyclic pattern in monthly data
For each key variable: Model: Correlated Errors (V ) based on AR(1) correlation. Circular smoother incorporated for month term (month 12 effect joins up smoothly with month 1 effect). Additive Models
Log SRP p-value = 4.0 x p-value = 0
Log NO 3 -N p-value = 0.011p-value = 0
Log Chlorophyll a p-value = 6.0 x p-value = 9.5 x 10 -7
Conclusions Additive and nonparametric regression models – Flexible tools for modelling Non-parametric trends and seasonality simultaneously with correlated errors. Changes in seasonality throughout time. Nonparametric trends within each season. Methodological modifications are required including circular smoothers and correlated errors.
Other Work Modelling chlorophyll a in terms of nutrients, water temperature and Daphnia. To explore: Lagged relationships Effects of covariates Changing relationships over time Modelling multiple responses of chlorophyll a and Daphnia to incorporate feedback relationships.