Fundamental Predictability in Multispecies Competition: The Influence of Large Disturbance

Abstract

Empirical evidence of chaos, or complex behavior, in ecosystems is scarce, presumably due to high system-level noise and/or the rarity of conditions necessary for complex behavior to arise. An alternative explanation might be that complex behavior is fragile and readily suppressed by disturbances that are common in many ecosystems. Here we investigated the role of disturbance frequency and magnitude on complex behavior and focused on population succession trajectories in a plankton system. Because of its prominence in aquatic ecology, we used hydraulic flushing and nutrient loading as disturbances. Our findings from numerical modeling exercises and laboratory microcosm experiments using natural plankton assemblages indicated that one aspect of complex behavior, divergence of nearby trajectories, was suppressed when the magnitude and periodicity of hydraulic flushing and nutrient loading were large. In other words, complex succession became determinable. Divergence of nearby trajectories was relatively robust, however, because pulses of not less than 85% of the total inflow were required to suppress this behavior. Our numerical findings also revealed that large hydraulic disturbances could introduce to the system another aspect of complex behavior, aperiodic succession.

Effect of imbalanced nutrients and immigration on Prymnesium parvum community dominance and toxicity: results from in-lake microcosm experiments

“…Regarding immigration, in theory, initial population densities of competitors can influence the dynamics of phytoplankton assemblages (Huisman & Weissing 2001, Roelke et al 2003. Research focused on spatial ecology in terrestrial systems suggests a complex unimodal relationship between immigration rate and community structure (Loreau & Mouquet 1999, Liebold & Miller 2004.…”

“…Three 28 d experiments were performed in Echo Cove during the fall (initiated on October 25, 2004), winter (initiated on January 11, 2005), and early spring (initiated on March 8, 2005). We used 36 transparent 2 l polycarbonate bottles, and experimental water was collected in the vicinity of Echo Cove at a depth of 0.5 m. To exclude large zooplankton, which may cause bias in small bottle experiments (Sommer 1985, Roelke et al 2003, lake water was filtered Fig. 1.…”

“…This may be especially relevant to species with benthic resting stages (Beltrami et al 2007). Previous theoretical studies have demonstrated that subtle differences in the initial composition of phytoplankton assemblages could have a profound effect on plankton dynamics (Huisman & Weissing 2001, Roelke et al 2003. Immigration, which can change the initial phytoplankton assemblage composition, can alter plankton dynamics at rates as low as 0.1% of the total phytoplankton biomass per day (Roelke & Eldridge 2008).…”

Effects of Nutrient Enrichment on the Stability of Producer Species Under the Pressure of Predation

“…This response is the Holling type II response [22],also it is the widely used functional response. Parameters.The reference parameter values for the nutrient-producer interactions have already been used by Huisman and other authors [11,12,[14][15][16]. According to the references, D=0.25 day [8,20,21,23].…”

Phytoplankton species predictability increases towards warmer regions

“…Indeed, populations' shifts might be acknowledged in advance (Roelke et al 2003). For example, the PEG (Plankton Ecology Group) model predicts, at least for temperate dimictic lakes, that the seasonal succession proceeds from rapidly growing, highly edible colonizing species to more specialized slower growing, less edible species often following a favorable change of the environment (Sommer 1989).…”