Thirty water samples from a cross-section of the Atchafalaya River taken at Morgan City, Louisiana in June 1991, have pollen concentrations on the order of 3500 grains/l. There are only rare grains ...attributable exclusively to long-distance transport from the northern United States, and the assemblage is dominated by species common in the local area. However, the condition of much of the pollen suggests that it is largely reworked.
Point-velocities obtained for each sample vary from 0.58 m/sec to 1.3 m/sec. There are only minor variations among pollen assemblages, with differences in velocity and position (i.e., water surface or deeper in the water column) having only minimal influence on the pollen distribution. It is likely the differences that do exist reflect unmixed waters of drainages which confluence immediately upstream of the sample site.
Compared to 1987 data from the Mississippi River, the June pollen spectra of the Atchafalaya are enriched in the locally abundant Taxodiaceae-Cupressaceae-Taxaceae. While the Mississippi has a June pollen concentration of about 2000 grains/l (approximately half of the Atchafalaya concentration), a higher proportion of the Mississippi pollen was damaged or degraded beyond identifiability. While this may suggest a greater contribution from reworked sediments, it may also be that the nature of the reworked sediment differs - the Atchafalaya may derive its pollen largely from eroded swamp and marsh sediments, in which the previously deposited pollen may be better preserved.
The Mississippi is estimated to supply some 10
19
grains of pollen/year to the Gulf of Mexico; if the contribution of the Atchafalaya is of similar magnitude, then together they supply approximately 2000 grains/cm
2
/year to the Gulf. Information on the taphonomy of pollen grains in these rivers is not only important to analyses of pollen assemblages in sediments from the Gulf of Mexico, but can serve as models of fluvial transport and deposition in large river systems.
Some would maintain that conservation and restoration activities are justified on ethical grounds alone (see review by Brennan and Lo 2008). However, demonstration of the economic benefit of ...ecosystems can help drive social and governmental support for conservation; and restoration and economic limitations could force choices among restoration activities. To aid decision making we need to estimate the values that restored ecosystems will provide for society. But defining these values remains a significant challenge, particularly within the context of restoration in which functions have been impaired and may contribute only incremental services over the varying course of the restoration process. Nonetheless, wetlands have direct and indirect economic value to local communities, and they provide services that benefit society as a whole. The term “ecosystem services” encompasses benefits that have direct economic value and those that have indirect public benefits. Evaluating and quantifying ecosystem services is a challenge regardless of the system status: natural, disturbed, or in various stages of restoration.
Recent archaeological excavations on the heads (i.e., the most elevated and upstream parts) of several large Everglades fixed tree islands may reshape what is understood about the age and formation ...of these landforms, and about the role of humans in the early Everglades wetland, between 3500 and 1000 B.C. Tree islands are patches of high ground, dry enough to support trees, that rise about 1 meter above the surrounding wetland, and those islands termed “fixed” are the large teardrop‐shaped islands thought to have formed over localized high points in the underlying bedrock (Figures 1a and 1b). A hard, cemented carbonate layer perched in the sediments of two tree islands in the southern Everglades was discovered by U.S. National Park Service archaeologists, and penetration of it with a concrete saw revealed that beneath the layer are unconsolidated sediments containing archaeological artifacts dating back to late‐Archaic times (3000–1000 B.C.) Schwadron, 2006.
