Figure 5-8: Diagram of complex
interactions between climate change, watershed and lake processes, and water clarity
of a eutrophic lake [modified from Lathrop (1998) and information in Lathrop et
al. (1999)]. The left panel diagrams a warmer, dryer climate with less wind; the
right panel diagrams a warmer, windier, and wetter climate with more extreme rain
events. In both cases, the altered climate would be expected to change the water
quality of the lake, but the complexity of relations leads to uncertain future
water clarities. A "+" means an increase and a "-" means a
decrease in the condition or process; a "?" means conflicting expectations.
Greater blooms of phytoplankton lead to lower water clarity, and reduced blooms
lead to greater clarity. Blooms depend on external and internal loading of phosphorus
(P). Dryer climates lead to less external loading, whereas wetter climates or
more episodic rains lead to more external loading. Warmer climates lead to warmer
surface waters and increased vertical stability in the water column, thus less
mixing and internal loading. Warmer waters also allow potential invasion by warmer
loving, zooplaktivorous fish that can reduce zooplankton species that in turn
reduce algal populations. Windier climates result in increased vertical mixing,
thus greater internal loading.
