Biology Report

Pre-visit Questions – Terrigal Lagoon Wetlands

1. Use the information provided to describe the ecosystem, include location, climate, regional attributes and values, catchment – land use, study site – site map

Terrigal lagoon is one of the four coastal lagoons in the Gosford area. Covering an area of approximately 9.6 square kilometres, it lies between Wamberal lagoon further to the north and Avoca Lake to the south. It is of important recreational use, with two commercial tourist operators using the lagoon – boat hire and sailboard hire. It is also popular for swimming amongst young children.

1. Which of the parameters measured in the Gosford City Council report are abiotic?

Abiotic factors include:

• Water level
• Turbidity
• Temperature
• Light intensity
• Salinity
• pH
• phosphorus
• Soil structure/colour/organic percentage

1. How does the lagoon temperature compare with the air and ocean temperatures? Explain.

The temperature of the lagoon water we recorded were about 23 degrees Celsius – however this can be unreliable as we measured it close to the water’s edge where it is warmer. The air temperature recorded for the lagoon was around 17 degrees.

The lagoon will be affected by weather more so than the ocean. This is because the lagoon is a smaller and shallower body of water.

1. Draw a food web to indicate how energy flows through the Terrigal lagoon ecosystem.
2. What factors influence the availability of dissolved oxygen in the lagoon?

Dissolved oxygen can be influenced by the temperature of the water. The warmer the water the less oxygen, therefore during higher temperature weather the oxygen content will be impacted. Additionally, a higher salinity rate in the lagoon holds less dissolved oxygen than fresh water. Clearing land causes organic matter to move into the lagoon, where microorganisms decompose it, consuming oxygen during the process. This causes oxygen availability to decrease.

1. Describe the inputs and outputs of nitrogen in the lagoon ecosystem.

Nitrogen occurs in natural waters as dissolved gas. Some primitive aquatic organisms can obtain their nitrogen requirements from this dissolved gas, e.g cyanobacteria or blue green algae. Green plants are the only organisms that can use the simple ions to make complex organic molecules. Animals obtain their nitrogen by consuming the complex molecules in the plants.

1. What is meant by ‘eutrophication’ and how might it impact on the flow of energy and the cycling of nutrients in the lagoon?

Eutrophication is the excessive plant or algal growth due to increased availability of one of the factors of photosynthesis such as sunlight, carbon dioxide, etc. It occurs naturally over long periods of time, however human activity has accelerated the rate of eutrophication through nutrients, e.g nitrogen and phosphorus into areas like Terrigal Lagoon.