The Quaternary period comprises approximately the last two million years of earths history (geologic time), and includes the Pleistocene and Holocene epochs.
A highly resilient mineral based on silica (SiO2). More information
It is possible to identify changes in sedimentation rates, as well as the timing of key historical events, in coastal lake or estuary catchments through measurement of radio-active isotopes. Of these, analysis of lead-210 (210Pb) is the only method capable of providing high-resolution ages for sediments over the last 150 to 200 years. It is thus an ideal technique for those investigating post-colonial anthropogenic impacts in Australia.
Lead-210, which is part of the uranium-238 (238U) decay series, is absorbed onto sediment particles deposited in lakes and estuaries. It consists of both supported and unsupported components. The former refers to that component which is in equilibrium with all members of the decay chain which precede it. It is derived from the in situ decay of radium-226 (226Ra) that has been directly washed into the system as part of eroded material (Figure 1). Unsupported 210Pb is derived from radon-222 (222Rn) which diffuses as gas through the soil interstitial pore space into the atmosphere, where it rapidly decays to 210Pb. The 210Pb then attaches to aerosol particles and settles out of the atmosphere as dry fallout or is washed out in rainfall events. This 'unsupported' 210Pb can fall directly onto the lake sediments or be washed in at a later time from elsewhere in the catchment (see Figure 1). In either event, once deposited and incorporated in the sediment, the activity of unsupported 210Pb will be solely a function of the amount present initially and its half-life (half-life = 22.6 year). Thus, a 210Pb-chronology can be determined for a sediment core by measuring the down-core activities of unsupported 210Pb and comparing these with that measured for the modern sediments at the top of the core. The activity of supported 210Pb can be determined indirectly by measuring the activity of 226Ra using either alpha or gamma spectrometry. Unsupported 210Pb cannot be measured directly and so is inferred from the activity of total 210Pb minus the activity of supported 210Pb. The activity of total 210Pb can be determined by either measuring 210Pb directly using gamma spectrometry or measuring (using alpha spectrometry) the progeny 210Po with which it is assumed to be in secular equilibrium.
Figure 1. Pathways by which 210Pb reaches aquatic sediments (after Oldfield and Appleby, 1984) .
The 'Redfield ratio' or 'Redfield stoichiometry' refers to the molar ratio of carbon (C), nitrogen (N) and phosphorus (P) in phytoplankton (principally diatoms). When nutrients are not limiting, most phytoplankton has the following molar ratio of elements:
C:N:P = 106: 16: 1
The redox potential, Eh, is the energy gained by transferring 1 mole of electrons from an oxidant to H2. It is measured in volts relative to a hydrogen electrode which is at zero. Eh can be calculated from the Nernst equation:
Eh = Eo - RT/nF ln [products]/[reactants]
Eo is the standard potential of the redox reaction in volts;
R is the gas constant (8.3 x 10-3) kJ K-1;
T is the temperature measured in Kelvins (K);
F is Faraday's Constant (96.5 kJ V-1);
n is the number of electrons in half reaction; and
[ ] is the activity of products and reactants.
It is negative in a reducing medium and positive in an oxidizing medium. EH and pE are related by the following:
pE = nF/2.303RT * Eh
At the core of the Oceans Policy is the development of Regional Marine Plans for large marine ecosystems or "Regional Planning Areas". These regions include: South-east, South-west, North-west, north and east. The profiles for these regions will set out the objectives for subsequent work to identify a network of Marine Protected Areas. More information
Report cards rate the overall condition of marine and estuarine areas (or other), as well as aspects of habitat extent and quality. They generally represent the culmination of twelve months of scientific monitoring at sites within a specified jurisdiction.
The average time a hypothetical particle of water spends in solution between the time it first enters and the time it is removed from a coastal waterway.
A measure of the closest distance between two unique identifiable features or the size of the smallest feature that can be mapped or sampled [1,2]. It is often divided into three subcategories:
Resuspension of bed sediments is the process by which currents and turbulence dislodge settled particles and mix them back into the water column. Fine sediments in the bed tend to stick together due to electrostatic forces. This cohesiveness is a property of the sediment mineralogy and also whether the sediment surface is covered by biogenic films or not. Such cohesive sediments may not resuspend until a critical flow speed is exceeded, which may be much higher than for coarser particles. In typical model formulations of the resuspension process, resuspension rates scale as the square of the flow speed so that doubling of flow speeds would quadruple resuspension rates.
Figure 1. Conceptual illustration of the resuspension process (modified after illustration in )
Ian Webster, CSIRO Land & Water
A surface current that is often of short duration and that flows seaward from the shore.
A rip channel is a channel which is formed by the seaward flow of a rip current. They are usually found to cross longshore bars.
The riparian zone is the vegetated corridor along streams and rivers. It serves a number of important functions that bear consideration in terms of farm management. The riparian zone:
Photo 1. Riparian vegetation along Jacqua Creek in Windellama, NSW. (photo courtesy of Upper Shoalhaven Landcare Council)
For more information about the functions and management of the riparian zone, see the Riparian Land Management Technical Guidelines published by the Land and Water Resources Research and Development Corporation, now Land and Water Australia (LWA) in 1999. This comes in two volumes, one on the principals of riparian zone management and relevant legislation, and the second on management tools and techniques. To order a copy, visit the Land and Water Australia website. The rivers through forests parameter is the proposed indicator for riparian zone condition.
Ralph Ogden, CSIRO Land and Water
"Is a combination of the vulnerability of the system and the intensity of the pressure (stressor) on, a system - a highly vulnerable system exposed to a high level of pressure is considered at high risk." 
Rocky reefs feature a hard substrate that may occur at supra-tidal to sub-tidal elevations. Surfaces are generally non-depositional and sometimes erosional, and are usually dominated by epifaunal and algal communities. More information