The blue green algae Anabaena circinalis was first discovered in Lake Trevallyn in bloom proportions in January 2007. The bloom was the catalyst for the establishment of the Lake Trevallyn Algal Bloom Monitoring Program and Working Group. The group’s aim is to monitor the occurrence of algal blooms in Lake Trevallyn during the peak summer recreational period providing early warning mechanisms to water authorities and to the public. The program also aims to understand the key drivers influencing the outbreaks and to propose various management strategies for adoption.
THE BIG PICTURE
At low numbers, algae cause no problems and are, in fact, a natural part of a water body. Occasionally, however, algae can grow very fast or ‘bloom’ and accumulate into dense visible patches at the surface of the water. Algal blooms can be driven by low water flows and high levels of available nutrients, such as phosphorous and nitrogen, which promote its growth. Algal blooms can become a serious public health and environmental problem in many waterways. Contact with an algal bloom may cause a number of human health problems, including skin rashes, eye irritation, earaches, itchiness, swollen lips and other symptoms. Algal blooms can also cause unpleasant taste and odour compounds in drinking water.
WHY THIS ACTIVITY IS IMPORTANT
The program coordinates monitoring efforts for Lake Trevallyn and provides a centralised data collection point for all stakeholders and an early warning of blooms occurring. It will also increase our understanding of the bloom processes in Lake Trevallyn, to aid in informing management options to address this issue for the long-term.
The monitoring program will allow management agencies to better inform, and communicate with, the public and users of the lake, about when it is safe for use, why blooms are occurring and what is being done to manage them.
WHAT HAS BEEN SOLVED
The first recorded bloom in Lake Trevallyn occurred in the summer of 2007. During 2008/09 a short-lived bloom occurred over two weeks. No blooms were detected in Lake Trevallyn in the 2009, 2010 or 2011 monitoring season due to increased catchment flows and numerous spills over Trevallyn Dam.
As the bloom has not occurred in the last two years efforts will be scaled back to monitor temperature stratification, flows and reduced algal counts which will still allow for an early warning system for the managers of Lake Trevallyn.
WHAT WE HAVE ACHIEVED
Key findings from the Monitoring Program are:
- Water flows are a major controlling factor of blue green algal blooms in Lake Trevallyn. Low residency times (high water flows) during summer may prevent the blooms from becoming established, as seen in the 2009/2010 summer;
- Suitable nutrient concentrations for algal growth are always present;
- Algal blooms persist due to stratification of the water, under the influence of high summer temperatures, which promotes cell growth and surface concentration of cells;
- Anabaena circinalis cells detected in the monitoring program have, to date, all been found to be at non-toxic levels.
A coordinated partnership approach to monitoring has enabled a greater understanding of the drivers of blue green algal blooms in Lake Trevallyn. The program has also allowed for shared resources and information between partners and the public.
Blue green algal blooms in Lake Trevallyn are largely driven by environmental conditions that occur during drought periods
Contact Person: Michael Attard
Title: TEER Scientific and Technical Officer
Business: Tamar Estuary & Esk Rivers Program
Phone: (03) 6333 7773