What’s New!

Blue-Green Algal Assessments

 

Rhithroecology now has a BBE Algal Torch

The algal torch  uses fluorescence to measure chlorophyll content in water.  This technique has been used for many years as a laboratory method, the Algal Torch allows it to be done in the field.

Because different algal groups have different forms of chlorophyll which fluoresce at different wavelengths, the algal torch can assess both the total amount of chlorophyll present (an indicator of total phytoplankton biomass) and also the amount of blue-green algal chlorophyll present.

Measurements take about 30 seconds, with an instant result. So we can take many measurements at the surface and at depths up to 10m to give an on-the-spot assessment of the blue-green algal concentrations. The most common previous techniques required samples to be returned to the laboratory, and algae to be enumerated which could take several days.  This method allows and instant assessment and action to be taken immediately to protect public health where necessary.

Talk to us now about how this technique can help you!

 

 

TDS and Conductivity

There are many field instruments which provide readouts of electrical conductivity (EC µS/cm) and Total Dissolved Solids (mg/L).  All of these instruments measure conductivity and then calculate the TDS value using the conductivity result.  However the relationship between conductivity and TDS depends on the mixture of salts present. Whether the ions are divalent (e.g. Ca ²+) or monovalent (e.g. Na +).  Australian inland waters generally differ from those in Europe and North America in that they are usually dominated by sodium and chloride rather than calcium, magnesium and carbonate.  Because the meters are designed predominantly for European an North American use, the calculated TDS values are incorrect for most Australian waters.  This can be an important issue where a discharge is close to the maximum salt concentration permitted for a particular receiving water.  I have developed a simple spreadsheet calculator which uses the formula from Bayly and Williams book (Inland Waters and their Ecology, Longmans, 1973) which was developed for Australian waters.  Just enter your conductivity measurement and the water temperature into the table you can find here TDS from conductivity table. 

 

Dissolved Oxygen Percent Saturation

The solubility of oxygen in water varies greatly depending on temperature, salinity of the water and altitude.  Of these temperature is the most critical in most lowland freshwaters.  You can convert dissolved oxygen from concentration (mg/L) to percent saturation using the excel spreadsheet here