Algae

Enteromorpha intestinalis

A filamentous green algae (light olive green) which floats in the shallows or over seagrass beds during the whole of the year, but with reduced vigour during mid-summer. The plant is supported by gases trapped within its hollow fronds. At times thick growths of Enteromorpha extend continuously over areas of the lake such as Windang Peninsula and Koona Bay. An algae harvester is used to collect the decaying Enteromorpha to alleviate odour problems around the lake.

Chaetomorpha linum

A treadilike filamentous green algae (deep green), with filaments unbranched 5 to 10 m long. It is very coarse to touch. In May to August thick growths of Chaetomorpha mixed with Enteromorpha cover large area along the shallows of Windang peninsula. These nuisance blooms are collected by a floating algae harvester around the lake.

Formanifera

Ammonia becarii

A species of Formanifera which are unicellular, predominantly marine organisms. Forams are among the largest of the single-celled protozoans and normally posses a lobed skeleton ('test') making them easy to identify as a group. The size of this species is from 0.25-0.35 mm in diameter and it lives for about 2-3 months. They feed generally on dissolved organic materials, diatoms and algae. This species is common in Lake Illawarra.

Phytoplankton

Nitzschia seriata

This species has spindle-shaped siliceous (silicon) cells, 80-150 um long 6-8 um wide with pointed ends. They forms chains of 20 to 30 cells long by over lapping their ends. A cosmopolitan species in Australian waters.

Coscinodiscus spp.

Disc-shaped siliceous cells, 50 to 60 um diameter, and 25 um in thickness. Each cell is formed of two encasing valves. The surface of the valves has very minute perforations of various shape. Several species has been identified in the lake. The conclusive identification of these delicate cells usually requires electron microscope examination.

Gymnodinium sanguineum

Gymnodinium sanguineum is a dinoflagellate (microscopic plant). Dinoflagellates occasionally multiply rapidly to create blooms when conditions are favourable. These blooms include the 'red tides' that are capable of killing fish and other marine life. Red tides are so named because of the high density of cells loaded with the red photosynthetic pigment beta-carotene. Red tides have been recorded in Lake Illawarra in the past, causing the death of some fish and eels. Excessive nutrients may be to blame for the blooms, as well as the input of humic material to the lake during storms.