Managing saline lagoons - Section 3.3

Section 3.3 of the Saline Lagoon Guide includes the following:

• 3.3.1 Management of salinity;
• 3.3.2 Management of size, shape and depth;
• 3.3.3 Management of the substratum;
• 3.3.4 Vegetation encroachment;
• 3.3.5 Managing islands for nesting birds.
  

Key management points highlighted by the Guide are:

1. The salinity should approach sea-water levels, but range predominantly between 15% and 40%;
2. A freshwater supply is not necessary to a saline lagoon;
3. Some input of saline water is vital; this should on balance be greater than the freshwater input. Removal of excess freshwater in periods of high rainfall is essential for the maintenance of a saline lagoon habitat;
4. Salinity gradients or patchiness will increase habitat diversity;
5. The inlet/outflow of a lagoon should offer only restricted access to water exchange, it should be able to rapidly release the freshwater at peak input, and allow sufficient sea-water supply to counter a threat of greatly reduced salinity;
6. The horizontal level of the inlet/outlet bed (e.g. weir) should be a little below high water neap level;
7. Lagoons with no seawater exchange are difficult for marine organisms to colonize, can drift outside ideal limits for water conditions (for example, salinity) and have low diversity communities. Such lagoons may provide important bird nesting areas if salinities and water levels can be controlled;
8. Shallow, low salinity lagoons with a predominantly freshwater supply can be managed to provide bird feeding areas;
9. Lagoons with high exchange and little residual water at low tide are inappropriate to lagoonal specialists.