d. Both abiotic and biotic factors, from the estuary and the surrounding area
Explanation:
A mouth is a partially closed coastal mass of brackish water with one or more rivers or streams that flow there and have a free connection to the high seas. Estuaries form a transition zone between marine environments and river, which is referred to as ecotones. Estuaries are exposed to both marine influences such as tides, waves and the inflow of salt water as well as river influences such as freshwater and sediment flows. The most important factors to consider are abiotic resources and conditions, biodiversity and biomass: these are considered fundamental for the properties of ecosystems, the spectrum of habitats and sustainability. There are many biotic factors in estuaries. This includes plants and animals such as shrimp, fish and oysters. Abiotic properties in estuaries are, for example, temperature, sunlight and water in estuaries are abiotic factors.
Explanation: biotic factors depend among abiotic factors, meaning that living things need non-living things in order to survive. That also means that biotic factors everywhere including the surrounding area need to be thought of in this sense so that they are able to survive in the environment they are in.
