Which biome is characterized by constant water movement of rivers or streams flowing into the ocean?

The estuary biome is defined by the unique environment where freshwater from rivers and streams meets and mixes with saltwater from the ocean. This mixing zone is dynamic, characterized by constant water movement, which influences various ecological processes. The influx of nutrients from both freshwater and saltwater contributes to high productivity, making estuaries rich in biodiversity. They serve as crucial habitats for numerous species, including fish, birds, and invertebrates, and are essential for many marine life cycles, such as spawning and nursery grounds for young fish.

In contrast, the other options refer to different aspects of aquatic habitats and do not represent the specific characteristics of an estuary. The pelagic zone pertains to open ocean regions away from the coast, while the photic zone refers to surface areas of water that receive sufficient light for photosynthesis, usually found within the ocean and other large bodies of water. The benthic zone, on the other hand, describes the bottom ecosystem of oceans or lakes, encompassing the sediments and living organisms found there. Each of these areas plays a distinct role in the aquatic environment but lacks the specific components of constant water movement between freshwater and saltwater that define an estuary.