Biology Report

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Eutrophication results in noxious and foul smelling phytoplankton that reduce water clarity. Algal blooms limit light penetration into the water, reducing growth in plants that require the light underwater. High rates of photosynthesis caused by this eutrophication can decrease the inorganic carbon in the water and raise pH, which can cause blindness in organisms.

- What causes turbidity in the lagoons? Comment on the reliability of the turbidity data.

Turbidity values are high when water levels are low, because wind waves re-suspend and move fine bottom sediments. The turbidity data reliability can be questioned, as it is measured by the naked eye and can be subject to human error.

- How often did the faecal coliform levels exceed ANZE guidelines for recreational use (swimming)?

Faecal coliform bacteria are harmless inhabitants of the guts of mammals and birds. The median bacterial content should not exceed 150 organisms per 100ml. The faecal coliform levels from 1996 – 98 stayed steadily around 0 – 700 (over average most of the time) with two high spikes, reaching 2500 organisms/100mL and 3000 organisms/100mL.

- Explain the differences between the salinity values for bottom and surface waters.

On the graph, the two lines for surface and bottom waters follow each other however the salinity of the bottom waters is slightly higher. The salinity value vary with the amount of recent rainfall and drought.

- What times of the year would you predict that the lagoon would have a) highest inflows of water from the catchment and b) lowest inflows?

The lagoon would have the highest inflows around February and the lowest inflows around August.

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