Light thresholds for seagrasses of the GBR: a synthesis and guiding document for managing seagrass
Led by: Dr Catherine Collier, JCU
Light levels (i.e. water quality/turbidity) can be managed to minimise seagrass losses. Recent attempts to define threshold levels of light required to maintain GBR seagrass state has resulted in a spectrum of recommendations with no single definitive source document to guide regulation. We will compile the available information on light thresholds into a guiding document, which will become a key reference for managers and regulators to use in generating relevant water quality guidelines and conditions for developments such as dredging programs. It will also highlight research information needs and provide interim guidelines for immediate management application.
Seagrasses are dependent on light to maintain primary productivity, and when light levels become too low, seagrass loss occurs with considerable flow-on effects for GBR ecosystems (e.g. dugong and turtle mortality). In some cases, light levels (water quality/turbidity) can be managed to minimize seagrass loss. Thus, defining the amount of light (light thresholds) that seagrasses require to maintain their status has been the subject of some research effort over the previous 5 years. However, the range of approaches and methodologies used has resulted in a spectrum of recommendations with no single definitive source document to guide compliance.
How Research Addresses Problem
We will compile the available information on light thresholds into a guiding document, which will become a key reference for managers and regulators and modelers to use in generating relevant water quality guidelines. This will summarise light required to maintain the condition of GBR seagrasses and thresholds known to drive losses. This will consider different species with guidance on how to incorporate risk from cumulative impacts, such as temperature stress. An emphasis will be placed on how to apply and interpret thresholds within a regulatory framework, such as conditions applied to dredging programs and in achieving regional conditions suitable for GBR seagrass recovery.
Light requirements; Seagrass; Dredging; Monitoring; Thresholds.
This project is jointly funded through JCU, GBRMPA, Ports North and the Australian Government’s National Environmental Science Programme.