Question

Estuaries & oyster reefs: Explain the role of salinity in shaping the diversity of organisms across an estuary and the role salinity plays in the distribution and survival of oyster reefs.

Answer 1

Spatial distributions of motile organisms are shaped by species‐specific adaptations to different salinity ranges (shrimp) and by behavioral responses to environmental variability.

Estuaries are transitional ecosystems between land and ocean. Their defining feature is the salinity gradient, a spatial pattern in the mixture of water from two distinctly different sources: seawater, and freshwater delivered as land runoff. The salinity gradient is a fundamental reason why the estuary is not just an ecotone—a transitional zone between two separate biomes—but rather an ecosystem class of its own, with unique species assemblages and transport processes. As a result, patterns of water properties and biota along the estuarine axis from freshwater to sea seldom represent the simple passive mixing of two water sources.

Oysters can survive in water that contains 5 to 35 ppt (0.5 percent to 3.5 percent salt by volume).

Oysters abundance can be negatively correlated with salinity. Although species richness is positively correlated with water temperature, species diversity can be positively related to salinity.