What is biological monitoring

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Extra keywords: biological monitoring, freshwater, tropical Australia, water quality.


The use of biological indicators in water quality monitoring in Australia is a comparatively new field as opposed to the traditional monitoring of chemical and physical properties in water quality. It only came about in the late 1970's and slow to gained acceptance due to some misconceptions and legislative shortfall (Maher and Norris, 1990). Some of these misconceptions were that the use of biological monitoring would take more time, costlier, and complex to interpret while the more traditional methods of chemical and physical properties were more than adequate as a proxy for measurement of biological changes (Cullen, 1990). Moreover, there was no requirement in the water quality associated legislations at that time for the conduct of biological assessment when evaluating a water body in Australia (Maher and Norris, 1990). In time it has been proven that many of these conceptions were wrong and at present biological monitoring is an important part of the Australian and New Zealand Guidelines for Fresh and Marine Water Quality (Cullen, 1990; ANZECC, 2000). The main biological assessment tool adopted by all Australian States and Territory is the Australia River Assessment Scheme (AUSRIVAS), a tool to assess the health of rivers and streams by studying at the invertebrate community structure at family level (Parsons et al., 2004). This tool was developed after the establishment of the National River Health Program (NRHP) in 1992, in response to the declining condition of rivers in Australia (Smith et al., 1999). The scope of this paper is the review of application of biological monitorings in water quality assessments in Australia, in particular the northern tropical region. This paper aimed to provide some general information on the biological monitoring of freshwater quality in the Australian context, the related studies that had been conducted in the tropical region and the evaluation of the effectiveness of the biological monitoring in those studies.

What is biological monitoring?

Biological monitoring is a branch of the water quality assessment that measures the whole organism or community responses to changes in the environment (ANZECC, 2000; Allan et al., 2006). Biological assessments are intended to detect significant changes in the organisms or whole communities from the undisturbed state, where changes can be in the forms of species richness, community compositions/structure, abundance or distribution of specific species, and altercation in the physical, chemical or biological aspect of the whole ecosystem process (ANZECC, 2000). The monitoring element requires repetitive observations, in accordance to the predefined objectives and conducted in scheduled time and space, separating it from environmental surveys (Cullen, 1990). The main biological indicator of water quality in use in Australia involves the application of water quality indices and sampling of benthic organisms (Dixon and Chiswell, 1996). Most of these indices involve monitoring of benthic macroinvertebrates and AUSRIVAS, SIGNAL and ISI (Invertebrate Species Index) are such examples (Haase and Nolte, 2008). AUSRIVAS is based on the prediction of assemblages of freshwater invertebrates families from abiotic variables in an undisturbed stream, SIGNAL applies the arithmetic mean of family scores while ISI uses benthic macroinvertebrates information at the species level (Haase and Nolte, 2008). Other biomonitoring techniques include biomarkers, whole organism bioassays and biological early warning system (BEWS) (Allan et al., 2006). Biomarkers are agents such as Cytochrome P450, lysosomes and paraoxonase that are used to detect changes in biological responses when an organism is exposed to toxic effects of environmental chemicals, whole organism bioassays measure various biological responses of specific organisms to a mixtures of contaminants in a standardised and controlled environment while BEWS is based on toxicological response of organisms to a contaminant or mixture of contaminants in real time systems (Allan et al., 2006).

Why use biological monitors?

The traditional way of water quality monitoring which uses spot samplings and instrumental analytical measurement are limited in their capacities to provide information on bioavailability of pollutants in water and costly to conduct in larger temporal and spatial scale (Allan et al., 2006). Furthermore, the high variability in hydromorphological and hydrological conditions, intermittent release of pollutants from point source and bed-sediment resuspension of toxicants often generate inconsistencies in chemical and physical based of water monitoring (Allan et al., 2006). Water chemistry analyses often provide underestimated or overestimated values because of the high variability in the freshwater environment and do not consider the synergistic and antagonistic relationships between contaminants and the surrounding environment (Maher and Norris, 1990; Hoang et al. 2001). In retrospect, most water quality problems are often biological in nature, be it the treat of toxic algal bloom due to nutrient enrichment or fish kill due to toxic release from human activities as we are more concerned with the impact of pollution on organisms rather than some particular level of a contaminant in the environment (Cullen, 1990).

Biological indicators are capable of measuring the synergistic and antagonistic relationships between the contaminants and organisms, able to indicate biological acceptance level of toxicants below that of chemical or physical detection limits, able to integrate post effects of short term pollution events and has proven to be on similar with other types of water quality monitoring in term of cost and effort (Maher and Norris, 1990; Hoang et al. 2001). However, biological monitoring should not be considered as the definite solution to water quality monitoring as it is still susceptible to environmental heterogeneity, the application of biological indices requires a certain level of taxonomic knowledge in identification of biota and the considerable size of reference collection often required (Cullen, 1990; Maher and Norris, 1990).

The tropical Australia scenario?

The condition of rivers and streams in tropical Australia is quite different from its temperate region counterparts down south. Most of the rivers in tropical northern Australia are short in length, located near coastal catchment areas where rainfall rates are higher than inland, have high seasonal flow and subject to monsoonal climate and El Nino Southern Oscillation influences (Hamilton and Gehrke, 2005). However, majority of the rivers are still relatively unmodified, unlike their southern cousins and retained their natural flow regimes (Leigh and Sheldon, 2008). Catchment areas in this region consisted of dry forest, savana woodland, monsoon forest and some rainforest patches (Hamilton and Gehrke, 2005). In term of diversity, the tropical wetlands and rivers system harbour higher diversity of flora and fauna than temperate regions, due to its climatic stability and geomorphic variability (Leigh and Sheldon, 2008). In the coastal wetland, seasonal flooding periods plays a crucial role in the ecosystem processes and food web structures (Douglas et al., 2005). River systems in tropical Australia contribute an estimated 70% of the continent's surface water runoff and provide a relatively underdeveloped resource for future expansion (Hamilton and Gehrke, 2005). Major land uses near the freshwater systems in this region are dominated by agriculture and pastoral activities, posing potential treats of various types of pollution problems and natural resource modifications (Cavanagh et al., 1999; Cox et al., 2005). Salinisation of freshwater resources poses a growing problem here as elsewhere in Australia, and during dry periods, seawater intrusions from the coast may extend deep into upsteam rivers (Hodge et al., 2005; Dunlop et al., 2008). A legacy of past interglacial periods, acid sulphate soils scattered around the lowlands especially in mangroves and coastal swamps that pose a treat to water resource use when disturbed (Gosavi et al., 2004; Hamilton and Gehrke, 2005). Thus, monitoring of freshwater resources in these unique situations would require specific methods that are customised to the surrounding tropical environment.

Biological assessments of water quality in tropical Australia

Generally most of the freshwater quality studies conducted in the tropical region in Australia were not for monitoring purposes but rather uses bioindicators as their study tools. In addition, the number of researchs done in this field is relatively low and mostly concentrated in the sub-tropical region of south east Queensland, creating a sizeable knowledge gap in the understanding of the tropical freshwater river system in Australia (Hamilton and Gehrke, 2005). Most data collection work was done by the Department of Natural Resources and Mines but scientists were fortunately able to utilise the database for various form of analyses (Horrigan et al., 2005). Some of the recent studies applying the bioindicator concepts are described as follow. Haase and Nolte (2008) promoted the use of species level biotic index to assess stream health in south east Queensland and found that some invertebrate species commonly associated with pristine condition in that region can thrive on polluted waters in temperate waters, suggesting that species indicators are localised to a certain degree and interpretation of water quality based on family level indices may not be as accurate. Horrigan et al. (2005) studied the relationship between macroinvertebrates and salinity increases in the streams of Queensland and found changes of community structure at very low salinity level. The study utilised the Artificial Neural Network (ANN) model method that were able to detect subtle changes in the relationship which otherwise missed by more traditional statistical methods (Horrigan et al., 2005). Another study by Humphrey et al. (2007) focused on the use of a suite of biomarkers as chemical contaminants indicators in barramundi (Lates calcarifer) along a perceived pollution gradient in five North Queensland estuaries. The study was able to demonstrate the usefulness of biomarkers in pollution studies in conjunction with more traditional methods (Humphrey et al., 2007). Van Dam et al. (2002) proposed a monitoring and research program for assessing the treat of contamination from the uranium mining activities in Alligator Rivers Region using a suite of freshwater organisms at different trophic levels and habitats.

Guidelines in conducting biological monitoring

As with other forms of environmental monitorings, biological monitoring must be conducted for specific aims and would be able to gather a variety of information, such as the ambient conditions, current trends and violation of regulatory thresholds (Dixon and Chriswell, 1996). Different goals in a biological monitoring require different approaches, and monitoring modes can be separated into surveillance monitoring (long term changes in water quality, baseline information), operational monitoring (focusing on high risk area) and investigative monitoring (assessing the cause of impacted area) (Dixon and Chriswell, 1996; Allan et al., 2006). The objectives for biological monitoring programs can be the long term changes in the environments, baseline conditions in undisturbed areas, detection of pollutants, quality assurance of a resource (such as drinking water) or to study the impact of a unusual ecological event (such as drought, climate change, forest fire, pest infestation)(Cullen, 1990). When designing a sampling program for biological monitoring purposes, practical aspects such as size of samples, access to sites, sampling frequency, cost and choice of indicators and level of complexity must be taken into account for the monitoring program be conducted smoothly and without much alteration (Dixon and Chiswell, 1996). For the successful implementation of a biological monitoring program, the Australian and New Zealand Guidelines for Fresh and Marine Water Quality has laid out some detailed instructions on the necessary steps to be undertaken (Figure 1).

Assessing the results from monitoring programs and provide feedback to management

Determine key decision criteria and threshold limit (acceptable level of changes, statistical sensitivity)

Formation of suitable experimental design based on the selection of indicators.

Selection of indicators and protocols to meet predefined objectives.

Identification of objectives for protection of water resources.

Definition of primary management aims, level of protection desired and the management goals.

Steps in conducting a successful biological monitoring program (modified from ANZECC, 2000).

In summary, biological monitoring is an important component of the freshwater quality management but its application in the tropical region in Australia is still not wide spread and heavily depended on the work of the authorities. The freshwater drainage system receives significant influences from agricultural and cattle ranching industries but few scientific studies were conducted to measure the impact of such activities on the river system. As freshwater supply issues become more pressing in the future and Australia turn to the northern region for its naturally abundant freshwater resources, proper and continuous monitoring must be in place to ensure sustainability of the water supply and maintenance of the health of the rivers and streams.