Final answer:
Salt marshes are more productive due, in part, to calmer waters that provide a stable environment for organisms, allowing more sunlight for photosynthesis, and reducing physical disturbances. This stability, along with the adaptations of estuarine organisms, contributes to the higher productivity compared to mud flats.
Step-by-step explanation:
The statement that a salt marsh is more productive than the mud flat because it lies in calmer water can be considered true. Calmer waters in salt marshes provide multiple benefits for the ecosystem. Firstly, it creates a stable environment for organisms to thrive (A). This stability is essential because it reduces the energy that plants and animals must expend in dealing with the fluctuations of water movement and salinity, allowing them to grow and reproduce more effectively.
Additionally, calmer waters allow more sunlight for photosynthesis (C), which is critical for the primary producers in the ecosystem, such as algae and marsh grasses that form the base of the food web. More sunlight and less disturbance from water movement means that these plants can photosynthesize more efficiently, leading to greater productivity.
Lastly, reduced disturbance (D) is beneficial since it minimizes the physical stress on both plant and animal life, allowing for a more consistent and nurturing habitat. Hence, salt marshes often have a higher level of productivity compared to mud flats, which can be subjected to harsher conditions and more extreme fluctuations in salinity and water levels.