icolls - Sustainable Tourism CRC

More documents

Recommendations

Info

ECOLOGY, THREATS AND MANAGEMENT OPTIONS FOR SMALL ESTUARIES AND ICOLLS Title of paper: Predicting responses of New South Wales Coastal Lakes to changing nutrient loads Author: Barbara Robson Author's email: barbara.robson@csiro.au Abstract: The coast of New South Wales is dotted with more than 100 shallow lagoons that receive fresh water from their catchments and have intermittent or permanent connections to the ocean. As the human population continues to expand along the coast, coastal catchments are subject to increasing development pressure, which leads to changes in the quantity and quality of fresh water reaching coastal lagoons. To facilitate management of these ecosystems, there is a need for better understanding of their resilience and likely response to increased nutrient loads. In this study, an ecological box model with input from hydrodynamic and catchment models has been applied to eight New South Wales coastal lakes (Cudgen Lake, Coila Lake, Merimbula Lake, Back Lagoon, Burrill Lake, Narrawallee Inlet, the Myall Lake system and Lake Wollumboola). By applying the model with a range of nitrogen load scenarios, response curves have been generated for each system in terms of macroalgae, seagrass, microphytobenthos and phytoplankton biomass and seasonality. The results highlight the importance of factors such as lagoon area and morphology, residence time and denitrification efficiency in determining the sensitivity of coastal lagoons to changes in nitrogen loads. The study also indicates where more work is needed to fill gaps in essential data for these systems. Title of paper: A comparison of the Hydrodynamics of an Opening Event in two Coastal Lagoons Author: Emma Gale (UWA), Charitha Pattiaratchi (UWA), Roshanka Ranasinghe (DIPNR) Author's email: gale@cwr.uwa.edu.au Abstract: Intermittently Closing and Opening Lakes and Lagoons (ICOLL’s) are an important sub category of lagoons, and are characterised by their intermittent opening events to the ocean. The opening events, usually made artificially, are related to variable rainfall events that, over time, produce super-elevated lake levels that breach the beach berm and release the lake water to the ocean. An opening event introduces appreciable water level fluctuations (1-3m’s) accompanied by large salinity variability’s (7 – 30ppt) on a sub daily time scale and the duration and frequency of the opening may also vary between each ICOLL, from weeks to months, and inter and intra annually, respectively. The opening event for two ICOLLs, located in eastern Australia, Smiths Lake and Wamberal Lagoon, have been examined as a comparative study due to their similar bathymetry’s yet significantly different opening regimes. It has been found that the dominant physical forcing during these events appear to be a combination of low frequency sea level forcing, tidal forcing and an eroding-accreting inlet. The varying nature of these forcings and their interactions generate changes to the dominant processes controlling internal mixing and circulation, allowing the setup and breakdown of stratification, and the potential depletion of dissolved oxygen at depth. This talk shows that defining the hydrodynamics throughout the different stages of the opening event is important in understanding the water quality. Title of paper: Physical Processes of Intermittently Closed and Open Estuaries in South Africa Author: Piet Huizinga, Lara van Niekerk Author's email: p.huizinga@adept.co.za Abstract: The physical processes operating in the temporarily open and closed estuaries, including semi-closed systems will be discussed in the paper, by using examples from several studies of estuaries in South Africa. Approximately 70 per cent of the more than 250 estuaries in South Africa are intermittently closed and open. This aspect has a major influence on the ecological processes of these estuaries. Increases in closed mouth conditions can prevent fish and invertebrate recruitment from the sea into the estuary. Many of the small and very small estuaries in South Africa (often one to five km long) are temporary open and closed, but also some of the largest systems such as St Lucia, Bot and Swartvlei are in this category. The major force keeping the mouth of such an estuary open is the river flow, but large differences in river flow required to keep an inlet open occurs between different estuaries. For two small estuaries of similar size the differences in flow required to keep the inlet open can be twenty times or more. The river flow needed to maintain an open inlet is a major component of the freshwater requirements of estuaries and it is therefore most important that for each estuary this flow is determined. An interesting feature is that sometimes in small estuaries a semi-closed state of the inlet between open and closed can be distinguished. The inlet is then in a perched position on the sand berm and continuous over flow occurs from the estuary to the sea. However, this position can be so high that even at high tide influx of seawater into the estuary does not occur. This results in changes in the physico-chemical characteristics and biota of the estuary. 56
ECOLOGY, THREATS AND MANAGEMENT OPTIONS FOR SMALL ESTUARIES AND ICOLLS Title of paper: Identifying anthropogenic sources of fish assemblage instability in Lake Pontchartrain, Louisiana (USA), a degraded oligohaline estuary Author: Martin T. O'Connell Author's email: moconnel@uno.edu Abstract: Lake Pontchartrain, an oligohaline estuary in southeastern Louisiana (USA), has been subject to numerous anthropogenic impacts over the last half century including urban and agricultural runoff, shell dredging, over-fishing, artificial saltwater and freshwater inputs, shoreline alteration, and industrial discharges. Previous analysis of long-term fish data showed that significant changes in fish assemblages had occurred between 1954 and 2000, with demersal assemblages experiencing more instability during this period than either inshore or pelagic fishes. To assess the current condition of fish assemblages in Lake Pontchartrain relative to multiple ongoing and past environmental stressors, we conducted a three-year (2000-2003) monthly survey of fishes using trawls (8 sites), gillnets (5 sites), and beach seines (5 sites). Because increased fish assemblage variability has been used as an identifiable symptom of perturbed situations, we compared relative multivariate dispersion indices for assemblages representing different sites to determine which region appeared most affected by anthropogenic impacts. Assemblage variability was highest for fishes collected by gillnets and beach seines from a site in southeastern Lake Pontchartrain which is located near an artificial saltwater connection, the Mississippi River Gulf Outlet (MRGO). At this site, the relative dispersion indices for gillnet and beach seine collections over three years were 1.285 and 1.213, respectively (range of relative dispersion indices for other sites = 0.702-1.090). In contrast, demersal assemblages (i.e., fishes collected by trawls) were relatively stable at the MRGO site. This stability, though, is more a reflection of the assemblage being dominated by a single species, the bay anchovy (Anchoa mitchilli): numbers of A. mitchilli were significantly higher at the MRGO site compared to other Lake Pontchartrain sites (Friedman Test, p = 0.001). These results suggest that although most regions of the estuary exhibited habitat degradation to some degree, the greatest ecological instability occurred in an area associated with an artificial saltwater connection. Title of paper: The application of sediment capping agents on phosphorus speciation and mobility in Lake Ainsworth sediments, northern New South Wales Author: Darren Akhurst Author's email: darrenakhurst@hotmail.com Abstract: Experimental sediment cores from Lake Ainsworth were exposed to an induced 46 day, anoxic/oxic cycle in the laboratory, mimicking the seasonal thermal stratification cycle commonly observed in the lakes waters every summer. Under oxic conditions the supply of P and Fe to the overlying water was slow however, induced anoxia led to an enhanced release of P and Fe from the sediments to the water column. An inverse relationship between total P, Fe and redox potential suggests that Lake Ainsworth sediments are redox sensitive. P speciation analysis of Lake Ainsworth sediments revealed the presence of a large pool of reactive Fe-bound P. Two sediment-capping agents, a lanthanum modified bentonite clay and Bauxsol (a waste product from the aluminium smelting industry) were assessed at reducing the levels of P released from Lake Ainsworth sediments over the 46 day, anoxic/oxic cycle. The bentonite clay was highly effective at reducing plant available P in anoxic/oxic conditions, but enhanced levels of dissolved Fe occurred with its use. Whilst Bauxsol’s use to remove plant available P is not recommended in anoxic waters, its use in suspension in oxic waters warrants further study. Title of paper: A depositional record of large-scale oceanic inundation from a coastal freshwater swamp, Killalea Lagoon, New South Wales, Australia Author: Adam D. Switzer, Brian G. Jones, Charles S Bristow, Nupur Saini, Edward A Bryant, Rabea A Haredy and Adriana Garcia. Author's email: ads05@uow.edu.au Abstract: A thin laterally extensive sandy deposit exists in the upper embayment fill of Killalea lagoon, a predominantly freshwater swamp. Coring of the deposit suggests it extends continuously up to 450m inland and tapers landward rising to ~1.6m AHD. The deposit sharply overlies the peaty lagoonal sequence and consists of fine- to medium-grained sand with some organic material dominated by fragments and rootlets of Spinifex grasses. In places the sand is overlain by accumulations of organic-rich silt that contain charophytes suggesting re-establishment of lagoon conditions. Microfaunal investigation was limited by dissolution due to the presence of organic acids associated with the freshwater lagoonal environment. Ground penetrating radar transects of the seaward dune system suggest a penecontemporaneous erosional contact between a series of truncated pre-event dunes and several small overlying post-event dunes. Although somewhat problematic, dates derived from peat taken from just below the sharp contact of the sand sheet all provide a calibrated peak that suggests the sandy deposit occurred around 1500AD. Hypothesis considered for the deposition of the sand sheet are higher Holocene sea-level, storms and tsunami. The silty organic nature of the overlying sediments suggests that the 57
Page 1 and 2:
ECOLOGY, THREATS AND MANAGEMENT OPT
Page 3 and 4:
Page 5 and 6:
Page 7 and 8:
Page 9 and 10:
Chapter 1 ECOLOGY, THREATS AND MANA
Page 11 and 12:
Page 13 and 14: ECOLOGY, THREATS AND MANAGEMENT OPT
Page 31 and 32: Hypseleotris spp. Pseudomugil signi
Page 39 and 40: δ15 δ N (‰) 15N (‰) δ15 δ N
Page 63: ECOLOGY, THREATS AND MANAGEMENT OPT
Page 85 and 86: Research Programs The Sustainable T
show all

icolls - Sustainable Tourism CRC

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?