Historically, limnological and paleolimnological research has focused on large and typically deep lakes but in the last two decades there has been a growing interest in smaller and shallowerwaterbodies. Shallowlakesarejustifiablyconsideredasa separatelaketype, distinguishedphysicallyfromdeeperwaters by the fact that they are permanently mixed (polymictic) with a consequent lack of stratification of temperature or oxygen and with increased potential for nutrient recycling and redistribution of seston by physical water circulation patterns (Carrick et al., 1994). Whilst this is a useful distinction, there is no single definition of a shallowlake (Padisak & Reynolds, 2003). Scheffer (1998), inhisclassictextbook, acknowledgedafundamental difference in the behavior, ecological functioning, and bioticcommunities of shallow waters andarbitrarily selected a meandepthoflessthan3mtodefineshallowness. Forthepurposes of this chapter we have chosen to adopt this definition and thereby to focus on lakes where, under a favorable light climate, benthic algae and/or rooted submerged macrophytes mayoccupythemajorityofthelakebed (seealsoJeppesenetal., 1997). Under enriched conditions, however, the mechanisms that stabilize the macrophyte communities of shallow lakes may often break down and a transition to pelagic production with phytoplankton dominance occurs (Scheffer et al., 1993; Vadeboncoeuretal., 2003). Importantly, becauseofthesecharacteristics, shallowlakesare, forthemostpart, morevulnerable to a given pollutant load than large lakes. Shallow lakes can be either artificial in origin, for example farm ponds and ornamental lakes, or natural, for example floodplain lakes and shallow depressions in glaciated and polar regions (see Douglas & Smol, this volume). They are ubiquitous features of lowland landscapes and there are