Blooming blanket weed: managing nuisance algae in UK freshwater bodies

With Hannah Kemp, University of Nottingham.

All seminars online. Please contact sue.davis@nottingham.ac.uk for the link. Subject to change.

Part of the Geosciences Seminar Series.

Across the UK, many standing freshwater ecosystems are experiencing increasingly frequent and widespread blooms of “blanket weed” algae. The formation of thick mats at the lake surface causes major ecological damage by harbouring pathogens and decreasing aquatic plant diversity. Blooms also reduce the amenity value of freshwater bodies because they are unsightly, prevent water-based activities and negatively impact conservation work. Currently the extent, cause and consequences of these blooms are largely unknown.

Clumber Lake, a shallow water body within the National Trust property of Clumber Park (Nottinghamshire), receives nutrient-rich waters from the River Poulter and has had nuisance blanket weed blooms over recent decades. Ongoing limnological monitoring and bioassay experiments at this site aim to understand the causes of blanket weed growth and blooms to inform management. A combination of nutrient and bioassay experiments suggests that both phosphorus and nitrogen are rarely limiting to blanket weed growth, but that light availability is more likely to be the trigger for increased growth and subsequent blooms. Future controlled experiments at the mesocosm scale will investigate this hypothesis.

These preliminary results indicate that abundant nutrients deriving from the River Poulter provide the ideal conditions for a high biomass of blanket weed to develop, but that the timing of bloom occurrence is most likely modified by light availability. Therefore, nutrient control is likely to be the baseline requirement for a blanket weed control programme.