Saline lakes: integrating ecology into their management future

Defining the key temporal scales of variability in ecological processes is fundamental to saline lake management because the physical, chemical and bi ological characteristics of saline lakes undergo fluctuations at different time scales, compared to those of freshwater lakes. A long-term study of La ke Gallocanta (25 km(2) area inland saline lake in NE Spain) provides the e cological basis for its management. The coupling of the administrative fram ework with its ecological processes is examined. Limnological and climatolo gical parameters were measured using standard methods during 1977-1995. Com plete desiccation of the lake occurred in 1983-86 and in 1994-95. Water lev el fluctuations were strongly correlated with meteorological events, partic ularly rainfall for seasonal and decadal time scales. The relationship betw een salinity and water volume follows the typical model described for playa lakes. However, the intensity and frequency of the salinity and water volu me fluctuations in Lake Gallocanta also change over time. Most species show pulsing population dynamics at the larger time scales (annual, decadal). H owever, many of these show a continuous population development at shorter t ime scales. Examples are provided for several phytoplankton and zooplankton species. Fluctuations in water level also influence phyto and zooplankton community structure. The combination of the number of species, S, and the n umber of individuals, N, as K=log S/log N indicates that the community stru cture also fluctuates at different time scales. Most of the present laws es tablished for the management of saline lakes are centered on the conservati on of waterfowl. Although some generic laws attempt to preserve the overall natural ecosystem, only those dealing with the protection of wild flora an d fauna, and threatened species, are implemented. However, ecological knowl edge now suggests that the major objective for the conservation of saline l akes should be to preserve the fluctuation of the hydrological balance, avo iding groundwater extraction in the catchment area and surface water. Gener ic laws regulate water use in Spain and in many other countries. These laws are not useful for saline lake management because they do not offer soluti ons to the frequent conflicts arising between the water demand for intensiv e agriculture and nature conservation, which are common in the semi-arid zo nes where saline lakes are located. Integrated management of the land and w ater resources in the catchment area is required to preserve saline lake ch aracteistics. Recent legislation aims to promote such management. A model o f conservation and development of the overall ecosystem is presented.