Final answer:
Tidal saltwater marshes are primarily influenced by salinity and nutrient levels, which dictate the adaptations and survival of the organisms in these brackish water environments. Thus, the correct option is B.
Step-by-step explanation:
The two major chemical factors that influence tidal saltwater marshes are nutrient levels and salinity. Tidal saltwater marshes, which are a type of estuarine system, exist where fresh water from rivers meets the salt water of the ocean, creating a brackish water environment.
The fluctuating salinity levels can cause physiological stress to both plants and animals, and halophytic plants and certain animals have adapted to tolerate these salty conditions. Nutrient levels in these ecosystems can dictate the type and abundance of plants and animals as they provide essential resources for growth and development.