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Glossary A – B

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A

Acid sulfate soils

Acid sulfate soils (ASS) are soils and other soft sediments that contain iron sulfides (mostly pyrite (FeS2)) with typically smaller quantities of iron monosulfides (FeS)). More information

Adaptive management

Adaptive management is a systematic process for continually improving management policies and practices by learning from the outcomes of programs in action.

Advection

Advection is transport of substances in a fluid by the flow. An example of advection is the transport of pollutants in a river or the ocean by a current which carries these impurities along with it.

Aeolian

The erosion, transport, and deposition of material by wind, and work best when vegetation cover is sparse, or absent.

Aerobic respiration

Aerobic respiration (a.k.a. oxidative metabolism, cellular respiration, or aerobic metabolism) is a chemical process in which oxygen is used to make energy from carbohydrates. Aerobic respiration and aerobic decay are basically the reverse of photosynthesis. Therefore, phytoplankton with Redfield molar proportions should respire as follows [1]:

C₁₀₆H₂₆₃O₁₁₀N₁₆P₁ + 138 O₂ = 106 CO₂ + 16 NO₃ + HPO₄^2- + 122 H₂O + 18 H⁺ + energy

The function of aerobic respiration is to release the energy and nutrients in organic matter (food) so that they can be assimilated by organisms.

1. Drever, J.I. 1982. The Geochemistry of Natural Waters, Prentice-Hall, Inc., Englewoods Cliffs, N.J., pp. 388.

Algal blooms

Algal blooms are usually naturally occurring algae that for some reason reach high enough concentrations to be a nuisance. More information

Alkalinity

The total alkalinity of a water is the sum of the bases that are titratable with strong acid:

TA = [HCO₃] + 2[CO₃] + [B(OH)₄] + [OH] + [HPO4] + 2[PO₄] + [SiO(OH)₃] + [HS] + 2[S] + [NH₃] - [H] - [HSO₄] - [HF] - [H₃PO₄]^[1]

In seawater alkalinity is roughly equal to the carbonate alkalinity plus borate:

TA = [HCO₃] + 2[CO₃] + [H₂BO₃] ,

In most natural freshwaters total alkalinity is roughly equal to the carbonate alkalinity [2] e.g.:

mHCO₃^- + 2mCO₃^2-

Bicarbonate (HCO₃^-) and carbonate (CO₃^2-) ions are derived from weathering reactions. The hydrolysis of bicarbonate and carbonate helps to buffer (or minimise) pH changes caused by photosynthesis.

1. Lewis, E., and D. W. R. Wallace. 1998. Program Developed for CO₂ System Calculations. ORNL/CDIAC-105. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee.
2. Drever, J.I. 1982. The Geochemistry of Natural Waters, Prentice-Hall, Inc., Englewoods Cliffs, N.J., pp. 388.

Ammonium

Ammonium is a dissolved, reduced form of nitrogen with a chemical formula of NH4+. More information

Anoxia

Anoxia occurs when dissolved oxygen concentrations are approximately zero. More information

Anoxic

The condition of oxygen deficiency or absence of oxygen. Anoxic sediments and anoxic bottom waters are commonly produced where there is a deficiency of oxygen due to very high organic productivity and a lack of oxygen replenishment to the water or sediment, as in the case of stagnation or stratification of the water body.

Aquifer

"An aquifer is best described as a saturated permeable geologic unit that can transmit significant quantities of water under ordinary hydraulic gradients"……"It is used to refer to individual geologic layer, to complete geologic formation, and even to groups of geologic formations" [1].

1. Freeze, R.A., and Cherry, J.A. 1979. Groundwater. Prentice-Hall, Inc., Eaglewood Cliffs, N.J.., pg. 47.

More information

Asset

"The attributes of a system that hold value for the community and about which the community would be concerned if they were lost or degraded." [1]

1. DNRE (2002) 'Healthy Rivers, Healthy communities and Regional Growth: Victorian River Health Strategy.' The State of Victoria, Department of Natural Resources and Environment, 2002.

Aspartic acid racemisation

Amino acid racemisation is a chemical dating method that measures the relative abundance of amino acid isomers preserved within organic materials (expressed as a D/L ratio). It has been successfully applied to the dating of marine and terrestrial molluscs, teeth, bone, and aeolanites [1]. Traditionally, amino acid racemisation has been used in the dating of Quaternary sedimentary successions [2,3]. The fast racemising acid, aspartic acid (Asp) may be applied in the dating of recent sedimentary successions younger than 600 years [4,5,6]. Thus, the racemisation of aspartic acid has the potential to provide a geochronology for Late Holocene sedimentary successions that are otherwise difficult to date using more conventional dating techniques such as radiocarbon dating. Aspartic acid racemisation can provide a chronology for sedimentary successions that are >120 years old, where ²¹⁰Pb has reached its limit, and <600 years old where dating marine and estuarine material with the radiocarbon method is complicated by the marine reservoir effect.

The potential of aspartic acid to provide a chronology for geologically-young sedimentary successions was confirmed by comparing the kinetic trend of Asp observed in laboratory-induced racemisation established by simulated aging (heating) experiments (Fig. 1a) and the degree of Asp racemisation observed in radiocarbon dated fossil specimens of Anadara trapezia. This was achieved using seven fossil samples of A. trapezia that were analysed by the radiocarbon and amino acid racemisation methods (Fig 1b). This permitted a direct comparison between the degree of aspartic acid racemisation under ambient diagenetic temperatures and fossil age established by the radiocarbon dating method (Fig. 1a & b).

Figure 1. The results from the time-series experiments on fossil molluscs, together with the initial modern aspartic acid D/L value, support the apparent parabolic kinetic trend of aspartic acid for A. trapezia (Fig. 1b). The apparent parabolic nature of the time series experiment can also be seen in the relationship between D/L ratios and the square-root of radiocarbon ages which yielded a near-linear relationship within the reaction range (Fig. 1c) [7]. The relatively high R² value of 0.98 indicates that there is only a minor deviation from the trend line. This deviation is partly the result of the small number of analysis, but can also be attributed to natural variations.

Using the fossil time series data for A. trapezia and similar results for the estuarine mollusc Notospisula trigonella, numeric ages based on the degree of aspartic acid racemisation were determined using an apparent parabolic kinetic model [2,7]. Accordingly, for both A. trapezia and N. trigonella, numeric ages based on the degree of aspartic acid racemisation were calculated using the following formula [7]:

t = [(D/Ls - D/Lm) / Mc]²

Where:
t is age;
D/Ls is the average D/L ratio of the sample of unknown age;
D/Lm is the D/L ratio for a modern sample of the same species as D/Ls; and
Mc is the slope.

Using the above formula a total of 28 aspartic ages calibrated by the radiocarbon method were determined to establish a geochronology for the Holocene sedimentary successions of Lake Illawarra (Fig. 2).

Figure 2. Example of the aminostratigraphy of the Holocene sedimentary successions in Lake Illawarra using aspartic acid racemisation.

When examined within a lithostratigraphic framework, racemisation data permit the comparison of pre- and post-European sedimentation rates for Lake Illawarra (Fig. 3a & b). For example, sedimentation rates using the top 50 cm of a core collected from the central lagoon of Lake Illawarra have been calculated using Asp-derived ages obtained from in situ N. trigonella. The results indicate that the rate of sedimentation was ca 0.33 mm/a for 500 years prior to European settlement. The period between 130 and 40 years BP, which corresponds with primary land clearing for agricultural areas, shows an increase in sedimentation rates to 0.66 mm/year. The period from 40 years to the present, corresponding with an increase in urban and industrial development within the Lake Illawarra catchment, shows a dramatic increase in sedimentation rate to 4.5 mm/a, however some of this can be attributed to lower compaction within the upper portion of the core (Fig.3).

Figure 3. Asp D/L ratio and calculated age down core from central lagoon facies, Lake Illawarra.

Using Lake Illawarra on the south coast of New South Wales, Australia, as a case study, this research highlights the potential of aspartic acid for dating the Holocene marginal marine record. Several conclusions have been identified:

1. This study has shown that the application of aspartic acid racemisation dating, in conjunction with more traditionally utilised Holocene dating techniques, can provide a time framework for the Holocene marginal marine record of the Lake Illawarra region. This will enable further study of the Holocene evolution of marginal marine environments by providing a chronology for the lithostratigraphy associated with estuary infill. It should also aid in the investigation of Holocene sealevel fluctuations and their impact on sedimentation within the marginal marine record.
2. This study has also shown that aspartic acid racemisation dating can provide a viable alternative for age determinations of Holocene marginal marine environments, where more traditionally utilised dating techniques have reached their limits. For example, results from this study have shown that aspartic acid racemisation has the ability to date material less than 500 years of age where radiocarbon dating is ineffective due to the marine reservoir effect, and greater than 120 years of age where methods of dating younger material have reached their limit (e.g. ²¹⁰Pb). In essence, aspartic acid racemisation as a dating technique can fill the gap between more traditionally used dating methods, and when used in conjunction with these traditional dating methods, can provide a dating technique that is applicable for the entire Holocene.
3. Results from this study have shown that an aspartic acid-derived chronology on relatively recent sedimentary successions allows the quantification of sedimentation rates, and assists in assessing the impact of anthropogenic activities on sedimentation within estuarine environments. For the Lake Illawarra barrier estuary the results indicate that the sedimentation rate prior to European settlement was less than or equal to ca 1 mm/year or less, and that significant acceleration in sedimentation rates is observed post-European settlement to a rate of ca 4 mm/year.

These results show that the application of aspartic acid racemisation can provide a chronology for Holocene sedimentary successions in the estuarine environments, as well as quantifying sedimentation rates for geologically recent successions. This method provides a framework for the comparison of pre- and post European sedimentation rates in lagoonal successions and can assist in identifying potential adverse affects of urban, industrial and agricultural development on the marginal marine environment.

Acknowledgements

This study constitutes a portion of a PhD degree undertaken by C.R. Sloss in the School of Geosciences at the University of Wollongong. Financial and fieldwork support was provided by the School of Geosciences and the Research Centre for Landscape Change (University of Wollongong); Australian Research Council UOW; the Australian Institute of Geoscientists (AIG); and the Australian Institute of Mining and Metallurgy (AUSIMM).

1. Rutter, N.W., and B, Blackwell., 1995. In Rutter, N.W., and Catto, N.R., (Eds), Dating Methods for Quaternary Deposits, pp. 125-164. Geological Association of Canada, Toronto.
2. Murray-Wallace, C.V., Kimber, R.W.L., 1993. Further evidence for apparent ‘parabolic' racemisation kinetics in Quaternary molluscs. Australian Journal of Earth Sciences, 40, 313-317.
3. Murray-Wallace, C.V., 2000. Quaternary coastal aminostratigraphy: Australian data in a global context. In Goodfriend, G.A., Collins, M.J., Fogel, M.L., Macko, S.A., Wehmiller, J.F. (Eds.), Perspectives in Amino Acids in Amino Acid and Protein Geochemistry, pp.279-300. Oxford University Press, Melbourne.
4. Goodfriend, G.A., Hare, P.E., Druffel, E.R.M., 1992. Aspartic acid racemisation and protein diganesis in corals over the last 350 years. Geochimica et Cosmochimica Acta, 56, 3847-3850.
5. Goodfriend, G.A., Stanley, D.J. 1996. Reworking and discontinuities in Holocene sedimentation in the Nile Delta: Documentation from amino acid racemisation and stable isotopes in mollusk shell. Marine Geology, 129, 271-283.
6. Goodfriend, G.A., Brigham-Grette, J.B., Miller, G.H. 1996. Enhanced age resolution of the marine quaternary record in the Arctic using aspartic acid racemisation dating on bivalve shells. Quaternary Research, 45, 176-187.
7. Mitterer, R.M., Kriausakul, N., 1989. Calculation of amino acid racemisation ages based on apparent parabolic kinetics. Quaternary Science Reviews, 88, 353-357.

Author

Craig Sloss, University of Wollongong.

Assimilation

The utilisation by a living organism of absorbed food materials in the processes of growth, reproduction, or repair

B

Backscatter

Acoustic backscatter refers to the component of sound waves emitted by a sonar that are reflected from the seabed back in the direction from which they came. The intensity of backscattered energy depends on a number of factors including the angle of incidence of the acoustic beam, the acoustic wavelength, and the 'roughness' or scattering properties of the seabed. Backscatter intensity is measured in decibels (dB re 1uPa @ 1 m). In general, a higher backscatter represents a harder or rougher substrate than an area with a lower backscatter. Typically, acoustic backscatter is only useful as a relative measurement, therefore comparison of datasets from different water depths or acquired using different sonar parameters is extremely problematic.

Baffling

A reduction in the energy of flowing water (typically caused by plant material), such that sediment particles may settle from suspension.

Beach

A beach is an accumulation of marine sand that is transported to the coast by waves and currents. More information

Bedload

Sedimentary material subject to transport by flowing water (e.g. currents) which is moved by rolling, pushing, and saltation. The size of particles moved is proportional to the strength of water movement.

Benthic

Pertaining to the seafloor (or bottom) of a river, coastal waterway, or ocean. See more information.

Benthic carbon dioxide flux

The benthic carbon dioxide flux refers to the amount of carbon dioxide (CO2) released from a unit area of sediment over a specific time interval, during the decomposition of organic matter. More information

Benthic invertebrates

Benthic invertebrates are organisms that live on the bottom of a water body (or in the sediment) and have no backbone. More information

Benthic Micro-Algae (BMA)

Microscopic plants, which inhabit the sediment surface (or substrate) including diatoms and dinoflagellates.

Best practice

The term 'Best Practice' asserts that there is a technique, method, process, activity, incentive or reward that is more effective at delivering a particular outcome than any other technique, method, process, etc. The idea is that with proper processes, checks, and testing, a desired outcome can be delivered with fewer problems and unforeseen complications. Best practices can also be defined as the most efficient (least amount of effort) and effective (best results) way of accomplishing a task, based on repeatable procedures that have proven themselves over time for large numbers of people. (Wikipedia, 5/3/2008).

Bioaccumulation

Bioaccumulation is an increase in concentration of a toxicant in organs and tissues in excess of what is normally expected. The toxicant is bioconcentrated if its concentration in organs and tissues exceeds those of the surrounding air or water.

Bioavailability

The degree to which a contaminant or nutrient in an environmental media can be absorbed, transported, and utilised physiologically. Contaminants or nutrients that are readily taken up by organisms are termed 'bioavailable'.

Bio-clastic

Sediments made up of broken fragments of organic skeletal material, e.g. shells.

Biodiversity

Biodiversity refers to the variety of life on three different levels: genetic diversity; species diversity; and ecosystem diversity. More information

Biogeomorphological unit

A major meso-scale biogeomorphological subdivision of a biome that can be easily identified and typically contains distinct biotas e.g. fringing reefs, beaches, tidal flats, mudflats and shallow embayments [1].

1. Butler, A., P. Harris, et al. (2001). An Interim Bioregionalisation for the continental slope and deeper waters of the South-East Marine Region of Australia., National Oceans Office.

Biomagnification

Biomagnification refers to an enhancement of toxicant concentrations in tissues and organs at each successive level in a food chain.

Biomass

Biomass usually refers to the dry-weight of all organic matter contained within plants, animals or micro-organisms.

Bioregions

Figure 1. Australian bioregions used in the ANZECC/ARMCANZ Water Quality Guidelines and in Water Quality Targets Online.

Biotope, primary

A region within a biogeomorphological unit, primary biotopes refer to soft, hard or mixed substrate-based units and their associated biotic assemblages. These are modified by hydrological variables (wave exposure, turbidity, tidal effects and current speed) [1].

1. Butler, A., P. Harris, et al. (2001). An Interim Bioregionalisation for the continental slope and deeper waters of the South-East Marine Region of Australia., National Oceans Office.

Biotope, secondary

A substructural units of a primary biotope, defined by the generalised types of biological and physical substrate within the hard/soft/mixed categories e.g. igneous, calcareous, silts, sands, gravels, seagrasses, sponges [1].

1. Butler, A., P. Harris, et al. (2001). An Interim Bioregionalisation for the continental slope and deeper waters of the South-East Marine Region of Australia., National Oceans Office.

Bioturbation

Are organisms, mainly worms or crustaceans, that disturb the sediment by burrowing or during feeding. Their activities mix the sediment layers and may cause substantial sediment resuspension.

Blueprints

Catchment Management Authorities use Blueprints as a basis from which to develop catchment action plans. The Blueprints contain targets and statements that expressed how communities want natural resources to be managed in their region.

Buffering of pH in natural waters

(1) Carbonic acid formation:

then carbon dioxide (CO₂) enters water, a small amount hydrates to form carbonic acid (H₂CO₃):

CO₂ + H₂O = H₂CO₃

(2) Carbonic acid dissociation:

Some of the carbonic acid then dissociates into bicarbonate (HCO₃^-), carbonate (CO₃^2-) and hydrogen ions (H⁺):

H₂CO₃ = HCO₃^- + H⁺

HCO₃^- = CO₃^2- + H⁺

(3) Hydrolysis of bicarbonate:

Bicarbonate and carbonate ions also dissociate to yield hydroxyl ions (OH^-):

HCO₃^- + H₂O = H₂CO₃ + OH^-

CO₃^2- + H₂O = HCO₃^- + OH^-

Hydrolysis of bicarbonate (and carbonate) gives rise to a pH 'buffering' mechanism in waters that have appreciable bicarbonate concentrations. Hydrogen ions liberated during carbonic acid dissociation (2) neutralise the hydroxyl ions formed during the hydrolysis of bicarbonate (3). However, more hydroxyl ions are quickly produced and pH change is resisted unless the supply of bicarbonate and carbonate ions is exhausted. Bicarbonate and carbonate ions are derived principally from chemical weathering of silicate and carbonate rocks. Sulfate reduction also produces bicarbonate in an equivalent amount to the sulfate reduced.

By-catch

By-catch includes all living and non-living material which is caught incidentally while fishing for a target species.