- Title
- Factors influencing phytoplankton production in four coastal lagoons in NSW, Australia
- Creator
- Kneeshaw, Samantha Mary
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2009
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Eutrophication, the enrichment of water by nutrients and organic matter, causing an increase in primary production (PP), is one of the key environmental issues facing Australian estuaries (Parslow 1997). This issue is a relatively recent problem in Australia compared to other developed countries. Currently, around 50% of Australia's estuaries remain classified as pristine. Patterns of European settlement in Australia concentrated most of the eutrophic pressures around the urban centres of the south-east and eastern regions of Australia. However, recent population trends towards counterurbanisation have led to increased and changing pressures upon a greater number of estuaries, some of which had previous little disturbance. Coastal lagoons (or Intermittently Closed and Open Lakes and Lagoons (ICOLLs)) are common water bodies along the Australian coast and were the focus of this study due to their high susceptibility to catchment nutrient inputs. Phytoplankton PP is the dominant water column process by which light energy and nutrients are assimilated. Compared to biomass (Chl α), measures of primary productivity allow greater understanding of the dominant factors driving NSW coastal lagoons. From May 2001 to April 2003, near-monthly measurements of PP rates and associated variables were determined in four NSW coastal lagoons which vary in catchment disturbance from highly disturbed to relatively pristine. Lake Illawarra has the most disturbed catchment (63% developed), followed by Narrabeen Lagoon (50% developed), Burrill Lake (45% mainly to pasture land), and lastly, Durras Lake, a near-pristine system with 96% of native bushland remaining. To assess smaller-scale spatio-temporal variability in PP, four 2-week long experiments, with near-daily sampling, were conducted in Narrabeen Lagoon in the summer, autumn, winter, and spring of 2002. PP rates reflected the degree and type of catchment development and ranged from 123 gCm-2y-1 in the near-pristine lagoon to 367 gCm-2y-1 in the lagoon with the most modified catchment. Relative to a global range of coastal and marine systems, annual PP in NSW coastal lagoons exhibited intermediate rates. Systems with comparable levels of catchment disturbance showed similar rates to those observed in this study; for example, the lowest rates were similar to the coastal lagoon, Estero de Punda Banda, U.S.A., which had no urban or industrial development (Montes-Hugo et al. 2004). The highest PP rates were similar to systems with disturbed catchments, such as the anthropogenically-pressured Great South Bay, U.S.A. and the Thau lagoon, France (Lively et al. 1983, Plus et al. 2006). On average, 13,319 tonnes of carbon were assimilated annually in the largest and most developed coastal lagoon, Lake Illawarra. Appling the Redfield Ratio, this would require the annual uptake of 2345 and 325 tonnes of N and P, respectively. Based on modeled catchment loads (Baginska et al. 2004), nutrient inputs contributed on average only 7% of required and 10% of required P to support the estimates of annual PP in the four coastal lagoons. Despite low catchment inputs, relative to phytoplankton demand, coastal lagoons sustain high PP rates, presumably due to internal nutrient cycling. The main factors driving PP in NSW coastal lagoons are temperature and nutrients. Annual variation in PP generally followed a seasonal progression that paralleled the annual cycle of irradiance and temperature including reduced PP in winter. However, nutrient availability was the most important factor determining the level of biomass and PP the coastal lagoons were able to sustain. Nutrient inputs, coupled with poor flushing rates, ensures high retention of material transported into lagoons (SKM 1997), irrespective of entrance status, and makes coastal lagoons highly sensitive to changes in nutrient loading. This sensitivity to inputs calls for careful monitoring and management of coastal lagoons and their catchments. Understanding the eutrophic status of coastal lagoons and estuaries in Australia has been limited by a lack of long-term phytoplankton production data. This study allowed the development of a PP model, which could be used to predict PP using the easily measured surrogate, Chl α, and thus facilitate the use of many long-term Chl α data sets. With further testing, a eutrophic classification system, specifically for NSW coastal lagoons, could be developed.
- Subject
- phytoplankton growth; phytoplankton (N. S. W.); lagoon ecology; coastal ecology; THESIS 3532
- Identifier
- http://hdl.handle.net/1959.13/1479711
- Identifier
- uon:50352
- Rights
- This thesis © 2009 by Samantha Mary Kneeshaw is licensed under CC BY-NC 4.0: https://creativecommons.org/licenses/by-nc/4.0/ Unless otherwise noted, any third-party material reproduced within is © the respective owner and is excluded from this licence.
- Language
- eng
- Full Text
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