1a. The science of the relationships between organisms and their environments. Also called bionomics.
1b. The relationship between organisms and their environment.

2. The branch of sociology that is concerned with studying the relationships between human groups and their physical and social environments. Also called human ecology.

3. The study of the detrimental effects of modern civilization on the environment, with a view toward prevention or reversal through conservation. Also called human ecology.

[German Ökologie : Greek oikos, house; see weik-1 in Indo-European roots + German -logie, study (from Greek -logi, -logy).]

I only use the word with sense 1a, and deeply dislike 1b. I think it sounds much better to say ‘X and Y affect the riparian ecosystem’ than ‘X and Y affect the ecology of…’, argh! I had never heard or read about sense 3 before.

If you are really serious about ecology as a science, you’ll probably read things like Ecology, TREE  (Trends in Ecology and Evolution), Conservation Ecology and the myriad of other journals on the topic.