[elalmhicabalp]

I saw some turtles swimming in a lagoon in Hervey Bay Botanical Gardens, and they had algae on their shells. How and why does it grow there? Also, some of the turtles had longer tails than others, why is this? Do they lose it as they age or are they more likely to lose it through injury?

[Rounteetepehryn]

A good solid substrate, plenty of sunlight, (in otherwise murky water) protection from herbivores, and the generally high nitrogen content of our waterways means algae would be stupid to not grow there.

[venediene]

A good solid substrate, plenty of sunlight, (in otherwise murky water) protection from herbivores, and the generally high nitrogen content of our waterways means algae would be stupid to not grow there.

what DO said,

dunno about the turtles. you might be looking at different species? Every possibility you have short necked and long necked turts there.

short and long necked turts is a bit of a misnomoer as to me they all look like they have long necks. Those kooky common names!

[Quick$bux]

I think tail length depends on the sex of the turtle. In some species (all species?), males have longer tails than females.

Edited to add: Here are some pics.

[Preorbtat]

Algae grows where there is a bit of light and nitrogen as food.