original_query: What did MacDonald et al. analyze in their study?
query: What did MacDonald et al. analyze in their studies of the Gulf of Mexico chemosynthetic communities?
answer: MacDonald et al.'s studies analyzed remote-sensing images revealing oil slicks, the role of hydrates in community stability, community types (tube worms, mussels, clams), growth rates of organisms, and the impact of geological events on seep communities.