Disturbance frequency and community structure in a twenty-five year intervention study

Area of Science:

• Ecological dynamics
• Community ecology
• Hydrological disturbance

Background:

• Community regulation models often link disturbance gradients with biotic interactions.
• Higher trophic levels are predicted to be more sensitive to intermediate disturbance levels than their prey.

Purpose of the Study:

• To examine the effects of hydrological disturbance frequency on small-fish communities in the Everglades.
• To understand how manipulating drought frequency influences community structure and dynamics.

Main Methods:

• Intervention analysis using hydrological disturbance frequency manipulation.
• Monitoring fish communities at long-hydroperiod, short-hydroperiod, and intervention sites in the Everglades from 1978-2002.
• Analyzing community change, density, relative abundance, and dissimilarity in relation to drying events.

Main Results:

• Intervention to diminish drying frequency caused the intervention site's community dynamics to converge with the long-hydroperiod site.
• Community change occurred within 3-5 years post-drying if inundation persisted; time since last dry and dry period length predicted dynamics.
• Small fish density increased with reduced drought frequency, supporting disturbance-limited community structure.

Conclusions:

• Hydrological manipulation at the landscape scale influences drought patterns and community-level successional dynamics.
• Extended drought return times (beyond 4 years) lead to convergence on specific species compositions.
• Reduced drought frequency results in predator-dominated regulation of small-fish communities in the Everglades.