Temporal Coherence in Limnological Features of Two Southwestern Reservoirs

Abstract

Properties of aquatic ecosystems have recently been considered in a landscape context where lakes in a geographic area are examined to identify common and long-term behavior patterns for one or more variables. Identifying such temporally coherent features should permit generalizations about lake behavior in specific regions and therefore, predictive models based upon such information should have broad applicability within a regional landscape. We considered the temporal coherence of a number of physical, chemical, and biological features of two southwestern reservoirs that differed in age, watersheds, and trophic status to identify common landscape-level predictors of behavior. We found synchronous behavior (temporal coherence) associated with particulate nutrient dynamics (organic carbon, nitrogen and phosphate (PP)), dissolved factors that force plankton dynamics (total dissolved phosphate, reactive phosphate and reactive silicate (SRSi), and with nutrient ratios used as indices of nutrient limitation in the plankton (TDN:TDP, C:P, and N:P). Algal parameters related to biomass (chlorophyll and Simpson's diversity index) did not vary coherently but algal genus richness and bacterial abundance did. Temperature was identified as a forcing function explaining synchronous variability in all cases except SRSi, PP, C:P, N:P, bacteria, and richness. The two systems, although managed for different purposes, behaved similarly with respect to several commonly measured limnological features, most notably, those involving phosphorus. We conclude that it may be possible to use such analysis to establish reference conditions for reservoirs in a given geographic region.

Key Words:

• reservoirs
• synchrony
• nutrients
• models