Title:

Atlantic Salmon Aquaculture Subprogram: characterising benthic pelagic interactions in Macquarie Harbour - organic matter processing in sediments and the importance for nutrient dynamics

Project Number:

2012-047

Organisation:

University of Tasmania (UTAS)

Project Status:

Completed

FRDC Expenditure:

$209,239.30

Program(s):

Environment

Need

Strategic growth for the Tasmanian Salmonid Industry over the next decade is contingent upon ecologically sustainable development in Macquarie Harbour. In coastal bays and estuaries, it is well known that sediment water column interactions are a major driver of ecosystem condition and health. A key knowledge gap in Macquarie Harbour is a lack of ecological data on the capacity of sediments to process organic matter and nutrients and the influence on bottom waters, particularly in response to increased loads associated with expanded farming. This was acknowledged in the EIS for industry expansion in Macquarie Harbour prepared by the Proponent (the three companies growing salmonids in Macquarie Harbour; Tassal, Huon Aquaculture and Petuna Aquaculture). The work proposed in this study feeds directly into the adaptive monitoring and modelling approach adopted to support decision making for marine farming expansion in Macquarie Harbour, reducing the uncertainty in the environmental model, particularly with respect to bottom water predictions. This will be achieved via the collection of empirical process data and re-calibration and validation of sediment water column interactions in the environmental model. A limited understanding of sediment-water column processes is often lamented in other regions where ecosystem/biogeochemical model outputs are used to help guide environmental management decisions (e.g. trigger levels in the Channel/Huon), and as such, this research is likely to have much broader R & D applications.

Objectives

1. Quantify sediment water column nutrient fluxes at both the farm (local) and harbour (regional) scales

2. Generate sediment nutrient and dissolved oxygen respiration maps of Macquarie Harbour, including the release of nutrients from deposited farm waste

3. Calibration of sediment water column interactions in the Macquarie Harbour environmental model using process information from 1 and 2 above

4. Identify ecologically relevant and practical indicators of key ecosystem processes

Final Report - 2012-047-DLD - Atlantic Salmon Aquaculture Subprogram: characterising benthic pelagic interactions in Macquarie Harbour - organic matter processing in sediments and the importance for nutrient dynamics

Final Report
ISBN:9781862958258
ISSN:
Author(s):
Date Published:August 2015
Principal Investigator: Jeff Ross
 
Keywords: Salmon Aquaculture; Salmo salar; Macquarie Harbour; nutrients; sediment function; benthic processes; modelling; nitrogen; carbon; environmental management
 
Summary: The strategic growth of the Tasmanian Salmonid Industry over the next decade is contingent upon ecologically sustainable development in Macquarie Harbour. In coastal bays and estuaries, it is well known that sediment - water column interactions are a major driver of ecosystem condition and health.
 
A key knowledge gap in Macquarie Harbour was a lack of ecological data on the capacity of sediments to process organic matter and nutrients, and the influence of these on bottom waters, particularly given the expectation of increased localised organic loads associated with expanded farming. This report describes the work conducted to address this knowledge gap.
 
The first part of the study assessed the impacts of organic enrichment from salmon farming on nitrogen cycling processes in the sediments and included an assessment of the sediment’s capacity to recover during fallowing. The information was achieved by conducting a series of incubations, at farm and harbour scales and repeated across seasons and farm production cycles, in which sediment - water column fluxes were measured.
 
The results from the field incubations were used to re-calibrate and validate the sediment - water column interaction terms in the environmental model used in the Macquarie Harbour EIS.