I like this photo for only using black and white colours it's making people more focused on the theme of picture than light, colours etc. One thing that gets me little annoyed is fact that above the turtle is a lot of empty space which doesn't have any affect on the picture and the reflection in water is cropped a little. If not that little mistake it would be wonderful photo.
Anyway you nicely isolated the turtle from a background so viewers are not distracted from the main theme which is a turtle.
You should focus a little more on composition than things about technical aspect of photography as noise, camera setting etc.