The question is incomplete and the full version can be found online.
Answer:
The tone of the passage is hopeful and idyllic. It starts with a seemingly bad situation, which is reflected by the words "bewildering" and "discouraging," but then describes a good turn of events, as Calypso is found on a stream, usually a nice location. Words phrases such as "bed of yellow mosses," "small white bulb," and "soft nest" all help depict a dream-like situation, far from the initial one.
With the change proposed, the tone would become grim and unhopeful, mostly due to the phrases "puddle of gray algae," "insignificant bleached bulb," and "tangle of twigs," all of which depict the same image in a way that makes it look like a dire place to be.
Explanation:
The words in bold are: "bed of yellow mosses in which its small white bulb had found a soft nest."
A bed of yellow mosses is more appealing and inviting than a puddle of gray algae. While a small white bulb sounds adorable, an insignificant bleached bulb is a sad image. And a soft nest is likely to be more comfortable than a tangle of twigs.
