zones that unite aquatic and marine environments. Ecological connections among these environments are illustrated in Figure SA-8, which depicts the marine food web.
Dierauf also emphasized the physical connectedness of aquatic and marine environments, which makes it possible for infectious diseases of fish and wildlife to move from freshwater sources to intertidal zones to marine environments, affecting species that may not have encountered these disease agents before. Salmon, for example, hatch in small freshwater streams, travel hundreds of kilometers downstream to the ocean where they live for several years, only to return to the same streams where they hatched to spawn and die shortly thereafter. Thus, she observed, “if the temperature of the streams changes or the fish themselves pick up novel disease agents, because a vector, or an intermediate host, or a disease agent thrives in the new warmer environment, infectious disease may result.”
Evidence-based studies of the effects of climate change on the health of aquatic and marine wildlife are few, Dierauf reported; therefore, current understanding of this topic derives from such sources as historical comparisons (of climatic conditions and of animal health and behaviors), long-term ecological research, correlation studies, and recognition of the physical, chemical, and biological processes governing climate change. Following the flow of water from inland streams to estuaries and into the open ocean, Dierauf considered the possible impacts of climate change in each of the three main elements of the aquatic continuum and how these changes may affect the health of their animal inhabitants.
In freshwater ecosystems, extreme weather events that produce flooding can trigger overwhelming influxes of nutrients into ecosystems. Storms can cause a range of environmental disturbances; Dierauf described the release of Nile tilapia into Mississippi streams from aquaculture facilities damaged by Hurricane Katrina. Several emerging diseases of inland aquatic animals, described and depicted in Box SA-2 in the Summary and Assessment, may also be influenced by climate change.
Intertidal areas, such as salt marshes and estuaries, are essential for maintaining a delicate balance among many complex and interactive variables (such as temperature, light, salinity, wave action, sea level rise, erosion, and sediment deposition) that characterize the transition from freshwater to saltwater environments, Dierauf explained. Storms, such as hurricanes, greatly affect intertidal zones. Heavy inland rainfall increases the speed and volume of the run-off that reaches estuaries, while marine storms drive saltwater and its contents past the intertidal buffer, affecting inland ecosystem health.
Climate change is expected to produce a range of important effects on oceans (as well as on large, deep-water lakes such as the Great Lakes), according to Dierauf. These include increased wave intensity, increased nutrient turnover, changes in nutrients, and changes in the food web. In addition, she noted, higher