Molluscan Faunal Distribution in Florida Bay, past and present: An integration of down-core and modern data

[ Disclaimer ]

Introduction and Methods | Modern Field Data | Core Data | Water Quality and Salinity | Vegetation | Diversity and Abundance | Conclusion and Future Directions

Vegetation

[larger image]

Bob Allen moving average Russell moving average Whipray

Comparison of trends in 3 cores in percent abundance of epiphytic molluscs. Data from Bob Allen and Russell was smoothed by a 3-point moving average. Shaded areas illustrate similar trends at the 3 sites. A1 illustrates parallel trend in seagrass specialists; A2, nearly identical trends in SAV generalists at the 3 sites; A3, convergence of trends in specialists at 3 sites. B illustrates a period of divergence in specialists at the 3 sites.

• Steady rise in generalist epiphytes from ~1907-1954
• Corresponding decrease in seagrass-restricted epiphytes
• 1988 seagrass die-off preceded by decline in epiphytal molluscs
• Segment of core from ~1868-1907 similar to 1954-1988 for generalist epiphytes

• Increase in SAV overall from 1920’s to 1965-1975
• Increase in SAV generalists during 20th century
• Decrease in grass epiphytes during 20th century
• Patterns and frequency of change very similar in both cores

Percent abundance of epiphytic molluscs, grouped by species that dwell on grass only, species that dwell on any type of sub-aquatic vegetation (SAV), and the combined groups. Combined data for Russell and Bob Allen was smoothed by a 3-point moving average for comparison to Whipray data, due to the slower sedimentation rate in Whipray basin.

• SAV generalists are increasing relative to seagrass specialists throughout Florida Bay in the later half of the 20th century. This could be indicative of increased macro-benthic algae.
• All sites show periods of fluctuating abundance of seagrass-restricted epiphytes, indicating the presence, and density of seagrass beds fluctuates naturally over time.
• Between 1960 and 1985 all 3 sites in central Florida Bay show a sharp decline in total epiphytic molluscs. Factors affecting SAV health do NOT appear to be site-specific.
• Preliminary spectral analyses indicate Bob Allen and Russell Bank sites are responding to a similar forcing mechanism at about a 15-year frequency.

  ---

Click here for a printable version of this page (note: document will open in a new browser window)

Related information:

SOFIA Project: Ecosystem History: Florida Bay and the Southwest Coast

[ Disclaimer ]