Project number: 2014-038
Project Status:
Completed
Budget expenditure: $87,135.40
Principal Investigator: Jeff Ross
Organisation: University of Tasmania (UTAS)
Project start/end date: 1 Jan 2015 - 29 Jun 2015
Contact:
FRDC

Need

Previous research has shown a clear impact gradient associated with cage salmon farming operations, and that presence of bacterial mats (Beggiatoa) and proliferation of opportunistic species are features commonly associated with high levels of organic enrichment (e.g. Pearson & Rosenberg, 1978). The presence of opportunists, such as Capitellid worms, being classified as representative of “unacceptable impact” (Macleod et al., 2004). This premise has been validated in SE Tasmania and underpins regulatory monitoring requirements statewide (DPIPWE, 2004).

The understanding that proliferation of opportunists represents deteriorating conditions was translated to monitoring protocols in Macquarie Harbour, but the relationship between opportunists and the level of enrichment was not explicitly tested in this region. However, video surveys suggest that in Dorvilleid worms rather than Capitellids were the species most indicative of organic enrichment effects(DPIPWE, 2004). Dorvilleids can tolerate anaerobic sediments and high levels of hydrogen sulphide (Levin et al. 2013) and are known to be indicators of the impacts of finfish aquaculture (e.g. Paxton et al. 2010).

However, Macquarie Harbour is ecologically very different to other farming areas in SE Tasmania; the sediments are inherently depauperate, largely epibiotic and spatially patchy. A recent study in Canada has highlighted the need to better understand the relationships and compliance thresholds for established enrichment indicators (i.e. Beggiatoa sp and opportunistic polychaete complexes) in systems where ecological patchiness may occur (Hamoutene et al 2014); suggesting that, where there is significant potential for small scale spatial variability, normal successional responses may not be as reliable. Consequently, the responses may not be consistent with expectations developed from southern Tasmanian regions.

In this context it is important to identify the relationship between Dorvilleids and sediment condition; determining the reliability of this species as an indicator of sediment condition, and characterising the environmental conditions associated with changes in Dorvilleid abundance.

Objectives

1. Review the international literature to establish the current state of knowledge regarding Dorvilleid ecology, and in particular, their response to organic enrichment. This will include a review of their current use as indicator of the impacts of finfish aquaculture.
2. Carry out targeted field survey at selected leases to identify the relationship between Dorvilleids and sediment condition, characterising the environmental conditions associated with changes in Dorvilleid abundance.
3. Based on the finding of 1. and 2. determine the reliability of this species as an indicator of sediment condition in Macquarie Harbour
4. In conjunction with industry and government stakeholders make recommendations on the future use of Dorvilleids in regulatory monitoring of Salmonid aquaculture in Macquarie Harbour

Related research

Industry
Adoption
Environment