- Title
- The ecological effects of wrack harvesting in the Tuggerah Lakes, New South Wales
- Creator
- Casey, Karla J.
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2003
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- This study examined the effects of using an aquatic-based wrack harvester in the Tuggerah Lakes, New South Wales. A long-term monitoring program was designed to assess whether harvesting operations affected certain ecological components. These were the seagrass, Zostera capricorni, fish and infaunal macro-invertebrate assemblages. Over the three years of sampling, there were no significant effects of harvesting shown for any of these ecological components. Shorter-scale studies on the immediate effects of harvesting on Z. capricorni, infaunal and epifaunal macro-invertebrates, and water quality indicators were also examined. The aim of this section was to ascertain whether the harvesting disturbance was affecting these ecological components at a level not measurable in the longer-scale examinations. It was found that there were no short-term effects of harvesting on Z. capricorni, infaunal or epifaunal macro-invertebrate populations. However, harvesting did affect some water quality indicators. Turbidity, total phosphorus and ortho-phosphates increased significantly after harvesting. Although, these increases were short-lived, with values returning to those measured pre-harvest within one hour. Thus, the effects of harvesting at this scale were also deemed minimal. The material being collected and removed from the estuary was also examined. It was shown that the target material, sloughed seagrass leaves and macroalgae, was collected in the highest proportions, compared to small amounts of live Ruppia megacarpa, Z. capricorni and Halophila ovalis. Faunal bycatch estimates were also taken and results revealed that fish and invertebrate removal was low, especially for commercially important species such as prawns and fish. To ascertain whether wrack removal rates were detrimental to the Tuggerah Lakes system, the net loss of wrack was compared to the gain of seagrass material via growth. This involved calculation of the quantities of wrack removed via harvesting, evaluated against the primary productivity rate of Z. capricorni. Summer months were found to be five times more productive than winter months, with wrack harvesting more intensive during summer. From this, it was estimated that harvesting removed less than 3.24 % of the Z. capricorni standing stock biomass and productivity during summer. Even less was removed during winter. Therefore, the extraction of wrack at the current level should not have detrimental, long-term consequences on the estuary, as primary productivity was replacing a greater amount of organic material than that removed by harvesting. In conclusion, the effects of wrack harvesting, at the current level, in the Tuggerah Lakes was not significantly affecting any of the major ecological components investigated. These results will be used to make governmental decisions on the benefits of harvesting operations in New South Wales' waterways. It is suggested that future research should include location-specific investigations into spatial and temporal variations, as well as the scale of operations relative to the areal extent of harvesting. This will enable the determination of whether different harvesters working in different estuaries are affecting the major ecological components particular to that system.
- Subject
- wrack harvesting; ecological effects; Tuggerah Lakes, N.S.W.; estuaries
- Identifier
- http://hdl.handle.net/1959.13/1043182
- Identifier
- uon:14179
- Rights
- Copyright 2003 Karla J. Casey
- Language
- eng
- Full Text
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| View Details Download | ATTACHMENT02 | Thesis | 7 MB | Adobe Acrobat PDF | View Details Download |