An aquatic ecosystem is an ecosystem in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems. Aquatic ecosystems support a wide range of organisms, including microorganisms, invertebrates, insects, plants, and fish. Some hydrologists work in understanding the trophic systems within aquatic ecosystems and their health as a function of environmental conditions such as water temperature and turbidity. Aquatic biodiversity is a major concern in water conservation and restoration projects, as well as water resource management. Concern regarding the biological health of wetlands, rivers, and lakes has led to the idea of ‘ecosystem services’ as a means to quantify or assess the value provided to society by different natural environments, including aquatic environments. While this lens seems biased to the larger species that are of commercial value (i.e. fish), it is understood that healthy waters require the full spectrum of organisms as part of an aquatic ecosystem. The section on aquatic biology provides considerable detail on many of these species.