Discuss two important causes for the variation in the variation of temperature and/or salinity of an estuary.

1- Drought - Decrease in freshwater flow to estuary or increased influx of ocean water will lead to increased salinity 
1- Rate of evaporation - loss of water due to evaporation increases salt concentration

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Gives full presentation to observe

Although i don't know what is the simulated system, starfish are predators that eat mostly  microalgae,  snails, sponges, bivalves, mussels and other small marine animals. removing starfish from any system would definitely increase this animals that they prey.