Abstract Introduction Acknowledgements Material and Methods Results Discussion - Changes in Salinity - Changes in SAV and Benthic Habitats - Other Indicators of Change > Correlation Between Sites Significant Findings, Implications And Future Work References Appendices PDF version

Correlation Between Sites

A number of similar faunal and floral trends occur at the three sites - No Name, Featherbed and Card Banks. These trends allow us to determine regional or bay-wide changes, but variations in timing of events from bank to bank also point out areas of concern in the age models. For example, we would reasonably expect the pollen zones to be synchronous because these assemblages are indicative of regional changes. The same three pollen assemblage zones can be found in the three Biscayne cores and similar trends have been seen in the region. The decrease in Pinus pollen during the 20^th century also has been noted in cores from Florida Bay (Brewster-Wingard and others, 1997; Wingard and others, 1995) and Manatee Bay (Ishman and others, 1998) and reflects urbanization in the Miami/Dade county area. The shift from Zone 1 to Zone 2 is marked by the first occurrence of Casuarina pollen. Since Casuarina was introduced into south Florida around 1900 (Langeland, 1990), this provides another means to check age models. Using this criteria, the No Name and Featherbed Bank (GLW402-FBA) cores appear to have good age models for the upper portion of the cores; the first occurrence of Casuarina is dated at ~1900 in No Name and at ~1905 in Featherbed based on the ²¹⁰Pb ages. Given the error in ²¹⁰Pb models, the uncertainty of the specific year Casuarina was introduced, and the spacing of the pollen samples, these cores appear to have accurate age models. Our age model for Card Bank (GLW402-CBA), however, is much more suspect because the first occurrence of Casuarina does not occur until 1976 based on the ²¹⁰Pb ages.

Pollen data were not obtained for the 1997 Card Bank core, however, a comparison of ostracode assemblages between Card Bank (SEI297-CB1) and the central Biscayne sites illustrates some faunal events that may be synchronous. The local extinction of the rare (in these cores) but distinctive species Peratocytheridea setipunctata and the associated increase in bairdiids at ~1700 in both the No Name and Card Bank (SEI297-CB1) cores is strong evidence that the age models for these two cores are reliable and these regionwide faunal events are nearly synchronous within the resolution of the age models. The increase in Loxoconcha also occurs around 1700 in both No Name and Card Bank (SEI297-CB1) cores.

Further evidence of the correlation between No Name and Featherbed Bank (GLW402- FBB) can be seen by comparing molluscan and foraminifer distributions between the two sites. These comparisons between sites raise two important points: 1) there are bay wide patterns of change in the fauna and flora, indicating change is occurring on a regional scale (not at isolated banks) and 2) the majority of the age models appear to be sound, but further refinement is necessary.