PP31C-1155:
Diatoms as Proxies for Abrupt Events in the Hudson River Estuary
Abstract:
The Hudson River estuary has been subject to many abrupt events throughout its history including hurricanes, droughts and pluvials. Hurricanes in particular are rare, discrete events that if fingerprinted can be used to develop better age models for Hudson River sediments. Proxies use observed physical characteristics or biological assemblages (e.g. diatom and foraminiferal assemblages) as tools to reconstruct past conditions prior to the modern instrumental record. Using a sediment core taken from the Hudson River (CDO2-29A), in New York City, drought and pluvial layers were selected based on Cs-137 dating while hurricane layers were determined from occurrences of tropical to subtropical foraminifera.Contrary to previous studies (Weaver, 1970, Weiss et al, 1978), more than sixty different diatom species have been identified using a scanning electron microscope (SEM). Cosmopolitan, hurricane and drought assemblages have begun to be identified after observing multiple layers (Table 1). Tropical foraminifera dominated by Globigerinoides ruber pink were also found in a hurricane layer that we infer was deposited during Hurricane Belle in 1976. More diatom abundance analyses and cataloged SEM pictures will provide further insight into these proxies.
Table 1
Diatom Genera and Species |
Environment |
Clarification |
Cyclotella caspia |
Planktonic, marine-brackish |
Cosmopolitan |
Karayevia clevei |
Freshwater |
Cosmopolitan |
Melosira sp |
Planktonic, marine |
Cosmopolitan |
Thalassiosira sp |
Marine, brackish |
Cosmopolitan |
Staurosirella leptostauron |
Benthic, freshwater |
Cosmopolitan |
Actinoptychus senarius |
Planktonic or benthic, freshwater to brackish |
Hurricane and pluvial layers |
Amphora aff. sp |
Benthic, marine or freshwater |
Hurricane layers only |
Nitzschia sp |
Benthic, marine or freshwater |
Hurricane layers only |
Gomphonema sp |
Freshwater |
Hurricane layers only |
Surirella sp |
Marine-brackish |
Drought layer only |
Triceratium sp |
Marine |
Drought layer only |
Other Genera and species |
Environment |
Clarification |
Globigerinoides ruber pink |
Tropical |
Hurricane layers only |
Silicoflagellate sp |
Planktonic, marine |
Hurricane layers only |