Managed hydrochory: A novel process-based restoration approach for submerged macrophytes in regulated rivers

Hydrochory, the dispersal of propagules by water, is a critical process for recovery and resilience of freshwater macrophytes. Dams and other instream barriers fragment river networks, alter flow, and reduce opportunities for propagule movement and settlement, limiting recolonisation and connectivity. Downstream of a large dam in the mid-Brisbane River, south-east Australia, severe flooding has caused extensive scouring and substantial loss of submerged macrophytes that the threatened Australian lungfish relies on for spawning, juvenile refuge, and food resources. The dam inhibits natural hydrochory of macrophyte propagules, therefore active restoration is required to reestablish macrophytes downstream of the dam. We trialled the world’s first process-based restoration of submerged macrophytes through managed hydrochory, manually releasing vegetative propagules of two native species, Vallisneria nana and Myriophyllum verrucosum, just below the dam. Three releases (~50 kg wet weight per release) occurred over three months across a 1.5 km river reach. Wooden stakes were installed and monitored to evaluate propagule retention and establishment relative to local hydrology. Stakes increased retention, with most propagules trapped within the first 300 m, although some travelled the full reach. Establishment of both species was greater in shallow, fast flowing areas. Our approach shows early success and demonstrates that managed hydrochory can provide an effective, low-cost method for restoring submerged macrophyte habitat in regulated rivers following major scouring events.

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Colin Burke, Australian Rivers Institute - Griffith University (colin.burke@griffithuni.edu.au)

Authors:

Colin Burke, Australian Rivers Institute, Griffith University  (colin.burke@griffithuni.edu.au)

Joshua Whiley, Australian Rivers Institute, Griffith University  (joshua.whiley3@griffithuni.edu.au)

David Roberts, Seqwater  (david.t.roberts@seqwater.com.au)

Luke Carpenter-Bundhoo, Australian Rivers Institute, Griffith University  (l.carpenter-bundhoo@griffith.edu.au)

Mark Kennard, Australian Rivers Institute, Griffith University  (m.kennard@griffith.edu.au)