RECONSTRUCTING THE PALEOECOLOGY OF HAVERSTRAW TIDAL MARSHLANDS A Final Report of the Tibor T. Polgar Fellowship Program Lucy Gill Polgar Fellow Department of Ecology, Evolution and Environmental Biology Columbia University New York, NY 10027 Project Advisor: Dorothy Peteet Lamont-Doherty Earth Observatory Columbia University Palisades, NY 10964 Gill, L. and D. Peteet. 2018. Reconstructing the Paleoecology of Haverstraw Tidal Marshlands. Section V:1-43 pp. In D.J. Yozzo, S.H. Fernald, and H. Andreyko (eds.), Final Reports of the Tibor T. Polgar Fellowship Program, 2015. Hudson River Foundation. V-1 ABSTRACT Climate change, a timely topic, cannot be understood solely by analyzing modern- day ecosystems. Sediment stratigraphy from tidal marshes is an important source of paleoecological data, as these ecosystems experience high rates of deposition and preserve organic material well. Although Hudson River Valley marshes have been extensively researched, work has focused on the four areas protected by the Hudson River National Estuarine Research Reserve (HRNERR). The marshlands of Haverstraw in Rockland County are comparable to the HRNERR sites in their capacity for biodiversity, carbon sequestration, and other important ecological functions. They are, however, understudied. This study uses loss-on-ignition and macrofossil analysis in combination with X-ray fluorescence spectroscopy to construct a high-resolution paleoenvironmental record. Biotic and geochemical zones have been identified and correlated with archaeological and historical data to assess the influence of anthropogenic activity in the area. The organic:inorganic maxima evidenced likely correspond to a pre- industrial period, characterized by burning events associated with increasing populations and concentrated settlement, as well as agricultural practices. Invasive species are prevalent, but certain key native species, notably Acorus americanus (American Sweet Flag), persist today. Exponential increases in heavy metal concentrations likely result from industry in the area but have declined following cessation of this activity and introduction of unleaded gasoline. Understanding historical human impacts is vital for predicting the ramifications of future development as well as establishing protocols for conservation and restoration. V-2 TABLE OF CONTENTS Abstract ................................................................................................................ V-2 Table of Contents ................................................................................................. V-3 List of Figures ...................................................................................................... V-4 Introduction .......................................................................................................... V-5 Study Site ............................................................................................................. V-14 Methods................................................................................................................ V-16 Results .................................................................................................................. V-20 Discussion ............................................................................................................ V-26 Conclusions .......................................................................................................... V-35 Recommendations ................................................................................................ V-35 Acknowledgements .............................................................................................. V-36 Literature Cited .................................................................................................... V-38 V-3 LIST OF FIGURES Figure 1 – Location of tidal marsh study site ...................................................... V-7 Figure 2 – Approximate range of tidal marshes west of Haverstraw Bay ........... V-15 Figure 3 – Acorus field from which cores were extracted ................................... V-17 Figure 4 – Result of loss-on-ignition analysis for HAV-01 core, 0-95 cm.......... V-20 Figure 5 – Distribution of macrofossils by depth for HAV-01 core .................... V-21 Figure 6 – Unknown Seed A ................................................................................ V-22 Figure 7 – Result of XRF spectroscopy, lead (Pb) and zinc (Zn) levels ............. V-23 Figure 8 – Linear model fitted to express the correlation between [Zn] and [Pb] V-24 Figure 9 – Result of XRF spectroscopy, potassium (K) and titanium (Ti) levels V-25 Figure 10 – Linear model fitted to express the correlation between [K] and [Ti] V-26 Figure 11 – Differences in leaf morphology between Acorus species................. V-31 V-4 INTRODUCTION Paleoecology, the study of past ecosystems, is integral for an understanding of the historical trajectory of biotic and abiotic change (Dodd and Stanton 1990). Because of the geological principle of superposition, the classic axiom describing the positive correlation between age and depth of sediment, it is simple to establish a relative chronology of stratigraphic layers (Harris 1979). Peat coring, the extraction of a thin, cylindrical cross- section of sediment, is an important methodological tool for paleoecologists. Biotic materials can be identified within a sample and, based on their position within the core, a sequence of biota can be created to complement the geologic one. Inorganic materials in stratigraphic order provide clues regarding erosion and source of erosion. Climatic data can be correlated with these biological and geological sequences by reviewing historical records or inferring optimum ranges of temperatures, salinity levels, pH, etc. for the biota found to be present at a particular geologic interval (Dodd and Stanton 1990; Peteet et al. 2006). The confluence of these multiple variables then allows for a multiscalar assessment of historical community dynamics. Establishing the interactions between abiotic factors and living organisms through time and their reciprocal effects is important for predicting the effects of anthropogenic occupation and development (Peteet et al. 2006). In areas with high rates of sediment deposition and a substantive historical and/or archaeological record, it is possible to correlate specific human activities with their environmental consequences (Sritrairat 2012; Pederson et al. 2005). Macrofossil analysis in particular is an important technique in determining biogeographic patterns and historical trends in biodiversity, including both species richness and relative abundances (Carmichael 1980; Goman 2001; Grossman et al. 2013; V-5 Pederson et al. 2005; Peteet et al. 2006; Sritrairat et al. 2012; Sritrairat 2012). This procedure involves selecting fossil seeds, stems, leaves, needles, and other plant or animal remains from depositional layers throughout the core. Seeds are specifically important because they are often diagnostic at the species level, and those deposited in the surface sediment of fluvial and tidal environments have been shown to accurately represent the local mature vegetation (Carmichael 1980; Goman 2001). These materials can therefore provide a record of changing vegetation communities because they are situated within the surface sediment of a particular point in time. Palynology, the study of fossil pollen and spores, can also be used to infer the botanical record of a particular locality. These particulates, however, are much lighter than any macrofossil and are dispersed across a wider range (Birks and Birks 2001). Thus, pollen-based reconstructions are less site specific. For the purpose of this study, macrofossil analysis is more applicable because it allows for the assessment of impacts of specific human activities within a relatively small area, in this case one tidal wetland within the Hudson River Valley that is adjacent to Haverstraw Bay (Figure 1). Wetlands, terrestrial ecosystems that are either permanently, semi-permanently, regularly or seasonally inundated with water, can be important sources of paleoenvironmental data. Sediment deposition in tidal wetlands is at equilibrium with a relative rise in sea level (McCaffery and Thomson 1980). Thus, soil cores extracted from these environments can be used as proxies to examine fluctuations in sea level through time (Sritrairat 2012). This estuarine record is important, especially in today’s warming climate, as estuaries become inundated and soil carbon can be lost. V-6 Figure 1: Location of Haverstraw in relation to entire Hudson watershed (inset) and Hudson River National Estuarine Research Reserve sites (Hudson River Foundation for Science and Environmental Research 1990, modified by the author). V-7 Wetlands are also characterized by high primary productivity and nutrient levels, allowing them to support a diverse array of species (Mitsch and Gosselink 2000; Findlay et al. 2006). In addition, their anoxic environment causes extremely slow decomposition of organic materials, resulting in not only carbon sequestration but also a well-preserved record of historic flora and fauna (Wieski et al. 2010). Macrofossil analysis is therefore particularly well suited to paleoecological research within these ecosystems. The Hudson River Valley, running north to south along the eastern edge of New York, is surrounded by a variety of wetland subtypes. One such ecosystem, the tidal marsh, is characterized by a higher proportion
Details
-
File Typepdf
-
Upload Time-
-
Content LanguagesEnglish
-
Upload UserAnonymous/Not logged-in
-
File Pages43 Page
-
File Size-