Phosphorus is a critical element in the biosphere, limiting biological productivity and thus modulating the global carbon cycle and climate. Fluxes of the global phosphorus cycle remain poorly constrained. The prehuman reactive phosphorus flux to the ocean is estimated to range from 0.7-4.8 x 10 12 g/yr. Uncertainty in the reactive phosphorus flux hinges primarily on the uncertain fate of phosphate adsorbed to iron oxyhydroxide particles which are estimated to constitute 50% or more of the chemically weathered-phosphorus river flux. Most reactive phosphorus is initially removed from seawater by burial of organic matter and by scavenging onto iron-manganese oxide particles derived from mid-ocean ridge (MOR) hydrothermal activity. Calculation of the oceanic phosphorus burial flux is complicated by early diagenetic redistribution of both oceanic and terrestrial phosphorus. Increased phosphorus input during periods of warm, humid climate is offset to some degree by increased burial rate as productivity shifts to expanded shallow-water estuary and shelf areas where phosphorus is rapidly decoupled from organic matter to form phosphorite. Phosphorus scavenging is greater if high sea levels are associated with increased MOR hydrothermal activity such as during the Late Cretaceous. Less phosphorus is derived from weathering during cool, dry climatic periods but a more direct transportation of phosphorus to the deep ocean, and a shift of productive upwelling regions to deeper water areas allows more phosphorus to be recycled in the water column. Lowered sea level results in less effective trapping of phosphorus in constricted estuary and shelf areas and in an increase in the phosphorus flux to the deep ocean from sediment resuspension. A decrease in MOR spreading rates and the resulting decrease in phosphorus scavenging by iron-manganese oxide particles would result in more phosphorus for the biosphere. Orogeny and glaciation may accelerate chemical weathering of phosphorus from the continents when the increased particle flux is exposed to warm and humid climate. Large, reworked phosphorite deposits may proxy for short-term organic carbon burial and correspond to periods of increased reactive phosphorus input that cannot be accommodated by longterm organic matter and iron-oxide particulate burial.
We document here the threat of large scale destruction (collapse) of barrier islands based on the study of many cores taken along the Outer Banks and in Pamlico Sound, North Carolina.Around 1,100 cal yr BP, probably as the result of hurricane activity, portions of the southern Outer Banks must have collapsed to allow normal salinity waters to bathe southern Pamlico Sound for several hundred years. Such collapse could occur again during our current regime of global warming, rising sea level and increased tropical cyclone activity. The economic effect of barrier island break collapse on Outer Banks communities would be devastating.
Luminescence ages from a variety of coastal features on the North Carolina Coastal Plain provide age control for shoreline formation and relative sea-level position during the late Pleistocene. A series of paleoshoreline ridges, dating to Marine Isotope Stage (MIS) 5a and MIS 3 have been defined. The Kitty Hawk beach ridges, on the modern Outer Banks, yield ages of 3 to 2 ka. Oxygen-isotope data are used to place these deposits in the context of global climate and sea-level change. The occurrence of MIS 5a and MIS 3 shorelines suggests that glacio-isostatic adjustment (GIA) of the study area is large (ca. 22 to 26 m), as suggested and modeled by other workers, and/or MIS 3 sea level was briefly higher than suggested by some coral reef studies. Correcting the shoreline elevations for GIA brings their elevation in line with other sea-level indicators. The age of the Kitty Hawk beach ridges places the Holocene shoreline well west of its present location at ca. 3 to 2 ka. The age of shoreline progradation is consistent with the ages of other beach ridge complexes in the southeast USA, suggesting some regionally contemporaneous forcing mechanism.
The parasitic protozoon Trichomonas vaginalis produces multiple forms of cysteine proteinase (CP). The molecular basis for this has now been examined by cloning DNA fragments encoding CPs. Using generic degenerate oligonucleotide primers based on two well-conserved regions within the central region of all eukaryotic CPs, several polymerase chain reaction fragments were isolated from T. vaginalis genomic DNA and shown to encode different CPs. One fragment with a well-represented sequence was used as a general probe to screen a T. vaginalis cDNA library at moderate stringency and five different cDNA clones were isolated. Preliminary sequencing showed that they encoded similar but distinct CPs. In the process of confirming the 5' end of one of these cDNA clones using RACE-PCR (rapid amplification of cDNA 5' endspolymerase chain reaction), an additional sequence encoding a different CP was identified. The corresponding clone (TvCP3) and the three longest clones from the library screen (TvCPI, TvCP2 and TvCP4) were characterized further. TvCPl and TvCP2 were full-length and TvCP3 and TvCP4 were apparently slightly less than full-length. Comparison of the predicted amino acid sequences of the four clones showed that TvCPl and TvCP4 are related (72 YO identity). TvCP2 is closer to TvCPl (60%) and TvCP4 (65%) than is TvCP3, which has 53%, 59% and 56% identity to TvCPI, TvCP2 and TvCP4, respectively. Comparison with the sequences of other known CPs indicated that the T. vaginalis gene products all belong to the cathepsin Ucathepsin H/papain branch of the papain superfamily. The TvCPI, TvCP2 and TvCP4 sequences are related (3845 O/ O identity) to those of CP2 of Dictyosfelium discoideum, human cathepsin L, three CPs from lobster and CPs from black gram, oilseed rape and rice (oryzains a and B). TvCP3 shows less identity to the other eukaryotic CPs but is most similar to D. discoideum CP2 (38%). The four predicted amino acid sequences share some features distinct from the majority of CPs, which suggests they might have had a common evolutionary origin. The most striking feature of sequences TvCPI, TvCP2 and TvCP3 is the apparent lack of a pre-sequence (signal sequence) for TvCPl and very short pre-sequences for TvCP2 and TvCP3. Southern analysis indicated that the organization of the genes corresponding to the TvCP cDNAs differs. The TvCPI, TvCP2 and TvCP3 genes are single-copy, whereas the TvCP4 gene appeared to be multiple-copy. Similarly sized, single abundant transcripts were present for all four sequences. Overall, the data show that we have identified a family of genes in T. vaginalis which encode a number of CPs. In total, seven distinct sequences have been recognized. This suggests that the multiplicity of CP activities seen
The Outer Banks barrier islands of North Carolina, USA, contain a geologic record of inlet activity that extends from ca. 2200 cal yr BP to the present, and can be used as a proxy for storm activity. Optically stimulated luminescence (OSL) dating (26 samples) of inlet-fill and flood tide delta deposits, recognized in cores and geophysical data, provides the basis for understanding the chronology of storm impacts and comparison to other paleoclimate proxy data. OSL ages of historical inlet fill compare favorably to historical documentation of inlet activity, providing confidence in the technique. Comparison suggests that the Medieval Warm Period (MWP) and Little Ice Age (LIA) were both characterized by elevated storm conditions as indicated by much greater inlet activity relative to today. Given present understanding of atmospheric circulation patterns and sea-surface temperatures during the MWP and LIA, we suggest that increased inlet activity during the MWP responded to intensified hurricane impacts, while elevated inlet activity during the LIA was in response to increased nor'easter activity. A general decrease in storminess at mid-latitudes in the North Atlantic over the last 300 yr has allowed the system to evolve into a more continuous barrier with few inlets.
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