Future research

Although this study was limited by a lack of replication at the estuary level it has provided some valuable information on the distribution patterns in

estuarine macrofauna and the effects of natural variation between and within mesotidal river estuaries and open barrier estuaries in Tasmania. This study has also provided information on the response of macrofauna to nutrient loading in mesotidal river estuaries.

One of the problems with the investigation of nutrient loads in mesotidal river estuaries was the lack of estuaries from the eastern parts of the north coast of Tasmania. Only one estuary was represented (Pipers River) and as a

consequence it is unclear whether the differences detected in the macrofaunal assemblages are a consequence of nutrient loading or simply geographical differences. To improve the effectiveness of this design a survey with greater replication of estuaries spanning the entire north coast would be necessary. A survey of this nature would greatly improve the statistical power to detect anthropogenic impacts on macrofaunal assemblages in Tasmanian mesotidal river estuaries and would also greatly assist in determining the geographical differences, if any, between these estuaries. One positive aspect of this study was the use of pore water salinity instead of water column salinity. It was found to be far less variable and provide a true indication of the salinity in the benthos.

As most agricultural activity in Tasmania occurs in the north of the state, and with plans in place to expand these activities, a monitoring program urgently needs to be implemented. There is a great opportunity to examine the effects of nutrient loads in Tasmanian mesotidal river estuaries as northern Tasmania has many estuaries that would be suitable for a similar study. Also a larger study would greatly assist with the development of suitable biotic indices of anthropogenic disturbance and potential indicator species of pollution.

One area of research in estuarine ecology that greatly needs attention is determining how environmental variables effect macroinvertebrates

(Snelgrove and Butman, 1994, Edgar and Barrett, 2002). This is largely achieved through manipulation experiments where the level of anthropogenic impact (e.g. nutrients) is measured independently of changes in physical factors. Understanding biological responses to nutrient enrichment under different environmental conditions is integral for the effective management of eutrophication in estuaries (Posey et al., 1999, Posey et al., 2006, O'Brien et al., 2010).

4.3 Conclusions

The investigation into anthropogenic impacts on estuarine benthic macrofauna requires careful consideration of natural variation in the distribution patterns of macrofauna. The distribution of macrofaunal communities are driven primarily by sediment and salinity gradients, which are in turn driven by

geomorphological and hydrological forces. A consequence of the strong relationship between macrofauna and the environment can make the

detection of anthropogenic impacts difficult as the impacts inevitably covary along a sediment and salinity gradient. This can be overcome by examining the effects of anthropogenic activities on macrofauna along salinity and sediment gradients using multivariate techniques and having sufficient replication at the within estuary scale. Understanding these processes is essential if the environmental impacts of anthropogenic activities are to be determined and managed effectively.

Clearly, this study has markedly advanced our knowledge of the key environmental drivers in the distribution of benthic macroinvertebrates in Tasmanian mesotidal river estuaries and open barrier estuaries. The impacts on benthic macrofauna as a consequence of nutrient and sediment loading from catchment land use activities were evaluated in mesotidal river estuaries, providing valuable information on where the impacts in these estuaries are likely to occur. This information will prove invaluable to resource managers in reducing the impacts of catchment land use activities and developing cost effective monitoring programs targeting the problem areas in these estuaries that were flagged in this study. Also the methodology developed in this study

can be applied elsewhere and could prove particularly effective in sampling small to medium sized estuaries, similar to those surveyed in Tasmania.

References

ADAMS, S. M. 2005. Assessing cause and effect of multiple stressors on marine systems. Marine Pollution Bulletin, 51, 649-657.

ANDERSON, M. J. 2001. A new method for non-parametric multivariate analysis of variance. Austral Ecology, 26, 32-46.

ANDERSON, M. J. 2008. Animal-sediment relationships re-visited:

Characterising species' distributions along an environmental gradient using canonical analysis and quantile regression splines. Journal of Experimental Marine Biology and Ecology, 366, 16-27.

ANDERSON, M. J., GORLEY, R. N. & CLARKE, K. R. 2008. PERMANOVA+ for PRIMER: Guide to Software and Statistical Methods. PRIMER-E: Plymouth, UK.

ANDERSON, M. J. & WILLIS, T. J. 2003. Canonical analysis of principal coordinates: A useful method of constrained ordination for ecology. Ecology, 84, 511-525.

BALDÓ, F., CUESTA, J. A., FERNÁNDEZ-DELGADO, C. & DRAKE, P. 2005. Effect of the regulation of freshwater inflow on the physical-chemical characteristics of water and on the aquatic macrofauna in the

Guadalquivir estuary. Efecto de la regulación del caudal del Río Guadalquivir sobre las características fisicoquímicas del agua y la macrofauna acuática de su estuario, 31, 467-476.

BARROS, F., HATJE, V., FIGUEIREDO, M. B., MAGALHÃES, W. F., DÓREA, H. S. & EMı´DIO, E. S. 2008. The structure of the benthic macrofaunal assemblages and sediments characteristics of the

Paraguaçu estuarine system, NE, Brazil. Estuarine, Coastal and Shelf Science 78, 753-762.

BARTON, J. L., POPE, A. J., QUINN, G. P. & SHERWOOD, J. E. 2008. Identifying threats to the ecological condition of Victorian estuaries. Department of Sustainability and Environment Technical Report. BASNYAT, P., TEETER, L. D., FLYNN, K. M. & LOCKABY, B. G. 1999.

Relationships between landscape characteristics and nonpoint source pollution inputs to coastal estuaries. Environmental Management, 23,

539-549.

BILKOVIC, D. M., ROGGERO, M., HERSHNER, C. H. & HAVENS, K. H. 2006. Influence of land use on macrobenthic communities in nearshore estuarine habitats. Estuaries and Coasts, 29, 1185-1195.

BIRD, F. L., FORD, P. F. & HANCOCK, G. J. 1999. Effect of burrowing macrobenthos on the flux of dissolved substances across the water- sediment interface. Marine and Freshwater Research, 50, 523-532. BROAD, S., CORKEY, R. & COTCHING, W. 2010. Estimating Nutrient Loads

and Turbidity for Tasmanian Catchments. Hobart: Tasmanian Institute of Agricultural Research and CSIRO ecosystem sciences.

BROAD, S. T. & CORKREY, R. 2011. Estimating annual generation rates of total P and total N for different land uses in Tasmania, Australia. Journal of Environmental Management, 92, 1609-1617.

BROWN, S. S., GASTON, G. R., RAKOCINSKI, C. F. & HEARD, R. W. 2000. Effects of sediment contaminants and environmental gradients on

macrobenthic community trophic structure in Gulf of Mexico estuaries. Estuaries, 23, 411-424.

CAREY, J. M. & KEOUGH, M. J. 2002. Compositing and Subsampling to Reduce Costs and Improve Power in Benthic Infaunal Monitoring Programs. Estuaries, 25, 1053-1061.

CATFORD, J. A., WALSH, C. J. & BEARDALL, J. 2007. Catchment

urbanization increases benthic microalgal biomass in streams under controlled light conditions. Aquatic Sciences, 69, 511-522.

CLARKE, K. R. & GORLEY, R. N. 2006. PRIMER V6: User Manual/Tutorial. PRIMER-E, Plymouth, UK.

CLOERN, J. E. 2001. Our evolving conceptual model of the coastal eutrophication problem. Marine Ecology Progress Series, 210, 223- 253.

COMELEO, R. L., PAUL, J. F., AUGUST, P. V., COPELAND, J., BAKER, C., HALE, S. S. & LATIMER, R. W. 1996. Relationships between

watershed stressors and sediment contamination in Chesapeake Bay estuaries. Landscape Ecology, 11, 307-319.

DAUER, D. M. 1993. Biological criteria, environmental health and estuarine macrobenthic community structure. Marine Pollution Bulletin, 26, 249- 257.

DAUER, D. M., WEISBERG, B. & RANASINGHE, J. A. 2000. Relationships between benthic community condition, water quality, sediment quality, nutrient loads, and land use patterns in Chesapeake Bay. Estuaries, 23, 80-96.

DAVIS, J. R. & FARLEY, T. F. N. 1997. CMSS: policy analysis software for catchment managers. Environmental Modelling & Software, 12, 197- 210.

DEEGAN, B. M., LAMONTAGNE, S., ALDRIDGE, K. T. & BROOKES, J. D. 2010. Trophodynamics of the Coorong. Spatial variability in food web structure along a hypersaline coastal lagoon. . CSIRO: Water for a Healthy Country National Research Flagship.

DEFEW, E. C., TOLHURST, T. J. & PATERSON, D. M. 2002. Site-specific features influence sediment stability of intertidal flats. Hydrology and Earth System Sciences, 6, 971-982.

DETHIER, M. N. & SCHOCH, G. C. 2005. The consequences of scale:

assessing the distribution of benthic populations in a complex estuarine fjord. Estuarine, Coastal and Shelf Science, 62, 253-270.

DIAZ, R. J. & ROSENBERG, R. 1995. Marine benthic hypoxia: a review of its ecological effects and the behavioural responses of benthic

macrofauna. Oceanography and Marine Biology Annual Review, 33,

245-303.

DORSEY, J. H. 1982. Intertidal Community Offshore from the Werribee Sewage-treatment Farm: an Opportunistic Infaunal Assemblage. Australian Journal of Marine and Freshwater Research, 33, 45-54. DYE, A. H. & BARROS, F. 2005. Spatial patterns of macrofaunal

assemblages in intermittently closed/open coastal lakes in New South Wales, Australia. Estuarine, Coastal and Shelf Science, 64, 357-371. EDGAR, G. J. & BARRETT, N. S. 2000. Effects of Catchment Activities on

Macrofaunal Assemblages in Tasmanian Estuaries. Estuarine, Coastal and Shelf Science, 50, 639-654.

EDGAR, G. J. & BARRETT, N. S. 2002. Benthic macrofauna in Tasmanian estuaries: scales of distribution and relationships with environmental variables. Journal of Experimental Marine Biology and Ecology, 270, 1- 24.

EDGAR, G. J., BARRETT, N. S. & GRADDON, D. J. 1999a. A classification of Tasmanian estuaries and assessment of their conservation significance using ecological and physical attributes, population and land use.

Hobart: Marine Research Laboratories - Tasmanian Aquaculture and Fisheries Institute, University of Tasmania.

EDGAR, G. J., BARRETT, N. S., GRADDON, D. J. & LAST, P. R. 2000. The conservation significance of estuaries: a classification of Tasmanian estuaries using ecological, physical and demographic attributes as a case study. Biological Conservation, 92, 383-397.

EDGAR, G. J., BARRETT, N. S. & LAST, P. R. 1999b. The distribution of macroinvertebrates and fishes in Tasmanian estuaries. Journal of Biogeography 26, 1169-1189.

ENGLE, V. D. & SUMMERS, K. J. 2000. Biogeography of benthic

macroinvertebrates in estuaries along the Gulf of Mexico and western Atlantic coasts. Hydrobiologia, 436, 17-33.

EYRE, B. D. 1998. Transport, retention and transformation of material in Australian estuaries. Estuaries, 21, 540-551.

FAIRWEATHER, P. G. 1999. Determining the 'health' of estuaries: priorities for ecological research. Australian Journal of Ecology, 24, 441-445. FLEEGER, J. W., CARMAN, K. R. & NISBET, R. M. 2003. Indirect effects of

contaminants in aquatic ecosystems. Science of the Total Environment, 317, 207-233.

FUJII, T. 2007. Spatial patterns of benthic macrofauna in relation to

environmental variables in an intertidal habitat in the Humber estuary, UK: Developing a tool for estuarine shoreline management. Estuarine, Coastal and Shelf Science, 75, 101-119.

GALE, E., PATTIARATCHI, C. & RANASINGHE, R. 2007. Processes driving circulation, exchange and flushing within intermittently closing and opening lakes and lagoons. Marine and Freshwater Research, 58, 709- 719.

GASTON, G. R., RAKOCINSKI, C. F., BROWN, S. S. & CLEVELAND, C. M. 1998. Trophic function in estuaries: response of macrobenthos to natural and contaminant gradients. Marine and Freshwater Research, 49, 833-846.

GRAY, J. S. 2002. Species richness of marine soft sediments. Marine Ecology Progress Series, 244, 285-297.

GRAY, J. S., WU, R. S. S. & YING, Y. O. 2002. Effects of hypoxia and organic enrichment on the coastal marine environment. Marine Ecology

Progress Series, 238, 249-279.

HALE, S. S., PAUL, J. F. & HELTSHE, J. F. 2004. Watershed landscape indicators of estuarine benthic condition. Estuaries, 27, 283-295. HASTIE, B. F. & SMITH, S. D. A. 2006. Benthic macrofaunal communities in

intermittent estuaries during a drought: Comparisons with permanently open estuaries. Journal of Experimental Marine Biology and Ecology, 330, 356-367.

HIRST, A. J. 2004. Broad-scale environmental gradients among estuarine benthic macrofaunal assemblages of south-eastern Australia:

implications for monitoring estuaries. Marine and Freshwater Research, 55, 79-92.

HIRST, A. J., ALPINE, J. & CRAWFORD, C. M. 2006. Survey of benthic invertebrate communities from high conservation value Thirsty and Little Thirsty Lagoons, Cape Barren Island. Proceedings of the Royal Society of Tasmania, 140, 17-24.

HIRST, A. J. & KILPATRICK, R. 2007. Spatial and temporal variation in the structure of estuarine macroinvertebrate assemblages: implications for assessing the health of estuaries. Marine and Freshwater Research, 58, 866-879.

HIRST, A. J., KILPATRICK, R., GUEST, M. A., PROBST, T. & CRAWFORD, C. 2007. Determining the ecological health of estuaries in NW

Tasmania: A case study assessing the status of the Duck, Montagu, Detention and Black River estuaries. Marine Research Laboratories - Tasmanian Aquaculture and Fisheries Institute, University of Tasmania. HIRST, A. J., KILPATRICK, R., MOUNT, R., GUEST, M. A. & CRAWFORD,

C. 2005. Biodiversity and degredation of estuaries in north-western Tasmania. Hobart: Marine Research Laboratories - Tasmanian Aquaculture and Fisheries Institute, University of Tasmania.

HOLLISTER, J. W., AUGUST, P. V. & PAUL, J. F. 2008. Effects of spatial extent on landscape structure and sediment metal concentration relationships in small estuarine systems of the United States' Mid- Atlantic Coast. Landscape Ecology, 23, 91-106.

HOULAHAN, J. E. & FINDLAY, C. S. 2004. Estimating the 'critical' distance at which adjacent land-use degrades wetland water and sediment quality. Landscape Ecology, 19, 677-690.

JASSBY, A. D. & POWELL, T. M. 1994. Hydrodynamic Influences on

Interannual Chlorophyll Variability in an Estuary: Upper San Francisco Bay-Delta (California, U.S.A.). Estuarine, Coastal and Shelf Science, 39, 595-618.

JONES, A. R. 1987. Temporal Patterns in the Macrobenthic Communities of the Hawkesbury Estuary, New South Wales. Australian Journal of Marine and Freshwater Research, 38, 607-624.

JONES, A. R., WATSON-RUSSELL, C. J. & MURRAY, A. 1986. Spatial Patterns in the Macrobenthic Communities of the Hawkesbury Estuary, New South Wales. Australian Journal of Marine and Freshwater

Research, 37, 521-543.

KANANDJEMBO, A. N., PLATELL, M. E. & POTTER, I. C. 2001. The benthic macroinvertebrate community of the upper reaches of an Australian estuary that undergoes marked seasonal changes in hydrology. Hydrological Processors, 15, 2481-2501.

KATRAK, G. & BIRD, F. L. 2003. Comparative effects of the large

bioturbators, Trypaea australiensis and Heloecius Cordiformis, on intertidal sediments of Western Port, Victoria, Australia. Marine and Freshwater Research, 54, 701-708.

KENNISH, M. J. 2002. Environmental threats and environmental future of estuaries. Environmental Conservation, 29, 78-107.

KENNISH, M. J., BRICKER, S. B., DENNISON, W. C., GLIBERT, P. M., LIVINGSTON, R. J., MOORE, K. A., NOBLE, R. T., PEARL, H. W., RAMSTACK, J. M., SEITZINGER, S., TOMASKO, D. A. & VALIELA, I. 2007. Barnegat Bay-Little Egg Harbour estuary: case study of a highly eutrophic coastal bay system. Ecological Applications 17, supplement: s3 - s16.

KINNE, O. 1964. The effect of temperature and salinity on marine and

brackish water animals: II. Salinity and temperature - salinity relations. Oceanographic and Marine Biology Annual Review, 2, 281-339.

LENIHAN, H. S. & PETERSON, C. H. 1998. How habitat degradation through fishery disturbance enhances impacts of hypoxia on oyster reefs. Ecological Applications, 8, 128-140.

LERCARI, D. & DEFEO, O. 2006. Large-scale diversity and abundance trends in sandy beach macrofauna along full gradients of salinity and

morphodynamics. Estuarine, Coastal and Shelf Science, 68, 27-35. EVI , . A., OES H, D. F., OVI H, A., DAHM, ., ERS US, C., EWEL,

K. C., KNEIB, R. T., MOLDENKE, A., PALMER, M. A., SNELGROVE, P., STRAYER, D. & WESLAWSKI, J. M. 2001. The Function of Marine Critical Transition Zones and the Importance of Sediment Biodiversity. Ecosystems, 4, 430-451.

LIGHT, B. R. & BEARDALL, J. 1998. Distribution and spatial variation of benthic microalgal biomass in a temperate, shallow-water marine system. Aquatic Botany, 61, 39-54.

LONERAGAN, N. R., POTTER, I. C., LENANTON, R. C. J. & CAPUTI, N. 1987. Influence of environmental variables on the fish fauna of the deeper waters of a large Australian estuary. Marine Biology, 94, 631- 641.

LONG, E. R. 2000. Degraded sediment quality in US estuaries. Ecological Applications, 10, 338-349.

LORENZEN, C. 1967. Determination of chlorophyll and pheopigments: spectrophotometric equations. Journal of Limnology and

Oceanography, 12, 343 - 346.

MACKAY, F., CYRUS, D. & RUSSELL, K. L. 2010. Macrobenthic invertebrate responses to prolonged drought in South Africa‟s largest estuarine lake complex. Estuarine, Coastal and Shelf Science, 86, 553-567.

MACLEOD, C. K. & HELIDONIOTIS, F. 2005. Ecological status of the Derwent and Huon estuaries. Hobart: Tasmanian Aquaculture and Fisheries Institute, University of Tasmania.

MACLEOD, C. K., MOLTSCHANIWSKYJ, N. A. & CRAWFORD, C. M. 2008. Ecological and functional changes associated with long-term recovery from organic enrichment. Marine Ecology Progress Series, 365, 17-24. MAGNI, P., COMO, S., MONTANI, S. & TSUTSUMI, H. 2006. Interlinked

temporal changes in environmental conditions, chemical characteristics of sediments and macrofaunal assemblages in an estuarine intertidal sandflat (Seto Inland Sea, Japan). Marine Biology, 149, 1185-1197. MARSTON, F., YOUNG, W. & DAVIS, R. 1995. Nutrient Data Book, second

ed., Canberra, CSIRO.

MARTINETTO, P., TEICHBERG, M. & VALIELA, I. 2006. Coupling of estuarine benthic and pelagic food webs to land-derived nitrogen

sources in Waquit Bay, Massachusetts, USA. Marine Ecology Progress Series, 307, 37-48.

MCCLELLAND, J. W. & VALIELA, I. 1998 Linking nitrogen in estuarine producers to land-derived sources. Limnology and Oceanography, 43,

577-585.

MONTAGNA, P. A. & KALKE, R. D. 1992. The effect of freshwater inflow on meiofaunal and macrofaunal populations in the Guadalupe and Nueces estuaries, Texas. Estuaries, 15, 307-326.

MORRIS, L. & KEOUGH, M. J. 2002. Organic pollution and its effects: A short-term transplant experiment to assess the ability of biological endpoints to detect change in a soft sediment environment. Marine Ecology Progress Series, 225, 109-121.

MOVERLEY, J. & HIRST, A. J. 1999. Estuarine Health Assessment Using Benthic Macrofauna. Museum Victoria. LWRRDC Occasional Paper 18/99 (Urban Subprogram, Report #11).

.

NETO, J., M., TEIXEIRA, H., PATRICIO, J., BAETA, A., VERISSIMO, H., PINTO, R. & MARQUES, J. 2010. The Response of Estuarine

Macrobenthic Communities to Natural- and Human-Induced Changes: Dynamics and Ecological Quality. Estuaries and Coasts, 33, 1327- 1339.

NIXON, S. W., BUCKLEY, B. A., GRANGER, S. L., ENTSUA-MENSAH, M., ANSA-ASARE, O., WHITE, M. J., MCKINNEY, R. A. & MENSAH, E. 2007. Anthropogenic enrichment and nutrients in some tropical lagoons of Ghana, West Africa. Ecological Applications 17, supplement: s144 - s164.

NYBAKKEN, J. W. 2001. Marine Biology: an Ecoogical Approach, Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.

O'BRIEN, A. L., MORRIS, L. & KEOUGH, M. J. 2010. Multiple sources of nutrients add to the complexities of predicting marine benthic

community responses to enrichment Marine and Freshwater Research, 61, 1388-1398.

PAUL, J. F., COMELEO, R. L. & COPELAND, J. 2002. Landscape metrics and estuarine sediment contamination in the mid-atlantic and southern New England regions. Journal of Environmental Quality, 31, 836-845. PEARSON, T. H. & ROSENBERG, R. 1978. Macrobenthic succession in

relation to organic enrichment and pollution on the marine environment. Oceanography and Marine Biology: An Annual Review, 16, 229-311. PHILLIPS, J. & LAVERY, P. S. 1997. Waychinicup Estuary, Western

Australia: the influence of freshwater inputs on the benthic flora and fauna. Journal of the Royal Society of Western Australia, 80, 63-72. POORE, G. C. B. 1982. Benthic Communities of the Gippsland Lakes,

Victoria. Australian Journal of Marine and Freshwater Research, 33,

901-915.

POSEY, M. H., ALPHIN, T. D. & CAHOON, L. 2006. Benthic community responses to nutrient enrichment and predator exclusion: Influence of background nutrient concentrations and interactive effects. Journal of Experimental Marine Biology and Ecology, 330, 105-118.

POSEY, M. H., ALPHIN, T. D., CAHOON, L., LINDQUIST, D. & BECKER, M. E. 1999. Interactive effects of nutrient additions and predation on infaunal communities. Estuaries, 22, 785-792.

QUINN, G. P. & KEOUGH, M. J. 2002. Experimental Design and Data Analysis for Biologists, Cambridge, Cambridge University Press. RABALAIS, N. N., TURNER, R. E., SEN GUPTA, B. K., PLATON, E. &

PARSONS, M. L. 2007. Sediments tell the history of eutrophication and hypoxia in the northern Gulf of Mexico. Ecological Applications 17,

supplement: s129 - s143.

RAKOCINSKI, C. F., BROWN, S. S., GASTON, G. R., HEARD, R. W.,

WALKER, W. W. & SUMMERS, J. K. 1997. Macrobenthic responses to