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Sediment accretion and organic carbon burial relative to sea-level rise and storm events in two mangrove forests in Everglades National Park
Both cores examined in this study have a typical exponential decrease in specific excess 210Pb activity moving down core with the exception of the low activity in the near-surface (Fig. 2). Over time the mass accumulation rates have varied considerably from the overall average, a notable example being a substantial increase in the 2000 to 2009 period for both cores (Fig. 3). The mass accumulation rate for this period is 4.4 times greater than the 1924-2000 rate for SH3, and 3.3 times greater than the 1926-2000 rate for SH4. This period of enhanced accumulation increased the long-term mass accumulation rates from 677 g m-2 yr-1 to 903 g m-2 yr-1 for SH3, and 447 to 545 for SH4 (Table 1). The high accumulation rates in the upper sections of each core are accompanied by relatively low organic carbon content (Fig. 4) indicating anomalous sediment input corresponding to the noted near-surface low in specific excess 210Pb.
The accretion rates for each interval (Fig. 5) are similar to mass accumulation rate trends. The average accretion rates for three distinct time periods are shown in Table 1. The 2000-2009 period accretion rate is 1.8 times greater than the 1924-2000 rate for SH3 and 3.1 times greater than the 1926-2000 rate for SH4.
The OC burial rates are both higher and strikingly different for
each core during the 2000-2009 period (260 g m-2 yr-1 at SH3
and 393 g m-2 yr-1 at SH4). In contrast to the surface level rate differences
between the two cores, overall OC burial rates were similar
(151 g m-2 yr-1 at SH3 and 168 g m-2 yr-1 at SH4).