Water temperature has significant and systematic effects on biological processes at all levels of organization, from phytoplankton to whole ecosystems. In addition to its own effects, temperature influences several other parameters and can alter the physical and chemical properties of water such as dissolved oxygen and photosynthesis production. Some organisms, particularly aquatic plants, flourish in warmer temperatures, while some fishes such as trout and salmon prefer colder streams.
A significant factor in species distribution and survival is the quality of their habitat. Engineering structures, land use practices and the physical diversity of waterbody can create stresses on habitats and adversely affect the survival of species. Environmental managers identify the critical habitats for the species and propose alternatives for their restoration. EEMS can be used to support environmental managers in identifying these critical habitats in a natural system, and evaluate the alternatives to address the stresses that are affecting these habitats.
Instream habitat suitability studies are required for a wide variety of planning applications where aquatic organisms are an important consideration in the decision-making process. At certain flows, for example, the water may be too fast for juvenile fish or velocities may be too high for fish to spawn. At other flows, the water may be too shallow for spawning or suitable spawning gravel may not be covered by water.
Salinity intrusion is of growing concern in many regions where natural fresh water flows are impacted because of direct human activity such as urbanization and dam construction, and sea-level rise due to climate change. Estimating and evaluating the nature of the salinity intrusions on a seasonal and multi-year basis is a complicated process for which numerical modeling can bring great benefits.
Offshore energy activities can pose significant risk to the environment as demonstrated by Deepwater Horizon and many other historic oil spills. These spills can kill marine mammals and fish and contaminate their food supply for extended periods of time. Determining the transport and fate of spilled oil and/or oil spill responsiveness planning is a pressing need.
Submerged aquatic vegetation (SAV) are marine, estuarine, and riverine angiosperms, and macrophytes. These are grasses that grow to the surface of shallow water and only emerge from the surface at low tide. They serve vital ecosystem services in the shallow waters by providing refuge for small fish and shellfish from larger predators.
The US EPA describes nutrient pollution as “one of America’s most widespread, costly and challenging environmental problems.” This issue is of significant concern world-wide, with considerable resources now being committed in Asia and Europe to study eutrophication in streams, rivers, lakes, bays and coastal waters and related economic, environmental and human health issues.