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.
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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.
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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
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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
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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;
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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.
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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).
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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 of herbaceous, compared to woody, plants and has flooding patterns influenced by nearby bodies of water, either oceans or estuaries
(Mitsch and Gosselink 2000). Freshwater tidal marshes have exceptionally high
biodiversity. Due to their proximity to both marine and freshwater environments, they
often are part of seasonal migratory pathways for saltwater species, in addition to hosting
freshwater species year round (Crain et al. 2004). They are also integral to protecting the
surrounding environment from hydrological processes such as erosion, flooding and
drought (Gedan et al. 2010; Mitsch and Gosselink 2000). The dense vegetation of tidal
marshes serves as a barrier against waves from the abutting marine or estuarine area,
preventing shoreline erosion. By trapping sediment, tidal marsh plants trap pollutants
including heavy metals, which tend to adhere to soils (Mitsch and Gosselink 2000).
These particles settle to the bottom of the standing water in the marsh and are held in
place by vegetation. Wetland flora are also sites of high microbial activity (Verhoeven
and Sorrell 2010). These microorganisms convert excess nitrogen and phosphorous to
less harmful forms, preventing toxic elements from traveling into surrounding waterways
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(Mitsch and Gosselink 2000). Tidal marshes also play an important role in regulating
water levels. Marsh soils absorb water during periods of high rainfall or runoff events,
alleviating flash flooding, and this water eventually seeps into the water table (Mitsch and
Gosselink 2000). Because the water table in wetlands is shallow, they are important
resources in times of drought, as groundwater that has accumulated during high fluvial activity can replenish surface water (Mitsch and Gosselink 2000).
Wetlands, specifically tidal marshes, clearly play an irreplaceable role in several cyclical environmental processes. Because they are by definition in close proximity to other bodies of water, often where humans tend to settle, they are also traditionally impacted by human activity (Bromberg Gedan et al. 2009). Due to their biodiversity, humans settling in terrestrial areas along a particular waterway have historically travelled to these ecosystems for hunting purposes and continue to do so in the present day.
Freshwater tidal marshes in particular serve as water sources for terrestrial vertebrates and waterfowl (Turner et al. 2003). Additionally, cattail tubers were an important source of nutrients for the indigenous groups of the Northeast United States, and these peoples gathered them from wetlands (Merwin 2010).
The Hudson River estuary and surrounding area has a long history of human occupation, dating back to the Paleo-Indian period (10,500-8000 BCE; HAA 2008).
Initially, the area was settled by small bands of hunter-gatherers who left few archaeological traces of their inhabitance, due to their nomadic lifeways (HAA 2008).
Beginning in 8000 BCE, however, there is evidence of an increasing population with even more mobility who began to occupy and use a larger portion of the Hudson River landscape (HAA 2008; Merwin 2010). Middens, or trash heaps, of oyster and mussel
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shells have been excavated along the shoreline of Haverstraw Bay (Funk 1976). The bottom layer of one such site, Kettle Rock Point, has been dated via radiocarbon to 5863
BP ± 200 BP, making it one of the oldest shell middens in eastern North America (Funk
1976). These deposits likely represent the shells of consumed mollusks and are a common feature of Archaic North American archaeological sites (Ceci 1984). Several other midden sites have been identified and excavated along Croton Point, the southernmost boundary of Haverstraw Bay on the eastern side of the river, that date to the
Middle and Late Archaic periods (6000-1000 BCE) (Figure 2) (Merwin 2010). Remains of the red-bellied turtle (Pseudemys rubriventris) were identified within one of these
oyster middens and dated to 5850 ± 200 14C years, which is noteworthy given that this
species has been long extirpated from New York (Parris 1987).
The Archaic is followed by the Woodland period (1000 BCE-1600 CE), which in
this region is primarily associated with pre-Haudenosaunee (Iroquois) culture.
Archaeological evidence from this period is considerably more prevalent than the
preceding Paleo-Indian and Archaic because it is characterized by a transition towards
sedentism and corresponding increase in population density (HAA 2008). The site of
Little Wood Creek, located on the east bank of the Hudson in Fort Edward, New York
and excavated as part of a salvage project, provides evidence of extensive Woodland
period anthropogenic activity (Grossman et al. 2013). Semi-permanent and permanent
architectural features, including hearths, prepared floors, and postholes, were encountered
during excavations, indicative of long-term settlement (Grossman et al. 2013). Sedentary
lifeways, in comparison to nomadism, exert greater pressure on the surrounding
environment because, rather than moving as choice resources are depleted, allowing biota
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to replenish, permanent concentrations of relatively larger groups of people are associated with the developments of agriculture and other high-impact practices (Smith 1972).
Palynological evidence of fireweed (Epilobium), suggests that the area may have been
subject to human-induced, periodic fire events as early as 1500 BCE, during the Late
Archaic-Early Woodland Period transition (Grossman et al. 2013). Even at this early
stage of centralization, then, humans were affecting the distributions and abundances of
various species.
The first European settlement at Haverstraw was founded in 1666 and settled by
Dutch farmers, resulting in an exacerbation of human impacts on the region’s tidal
marshes (HAA 2008). The colony of New York was taken over by the English in the late
17th century, but the economy remained predominantly agricultural, although there was a
moderate degree of river commerce along the Hudson (HAA 2008). The shores of
Haverstraw Bay were important Revolutionary War-era sites, including perhaps most
notably the location where Benedict Arnold and John Andre met in 1780 to negotiate
Arnold’s treason (HAA 2008). The first brick manufacturing plant was constructed in
1810 by entrepreneurs from Philadelphia, who recognized these marshlands for their
natural clay and sand resources (HAA 2008). Because of the proximity to the Hudson
River, this site was optimal for transporting the finished products. A railroad and later
roads were built to greater facilitate this haulage. The brick industry remained the
predominant source of employment and economic prosperity of Haverstraw until 1942,
when rock mining operations, primarily gypsum, began to utilize much of the old
brickyard land (HAA 2008).
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At the nearby Piermont and Iona tidal marshes, both part of the Hudson River watershed, similar coring techniques produced evidence of changes in species composition that correlated with dates of European colonization (Pederson et al. 2005;
Peteet 2005). Ambrosia (ragweed) and other weedy species, including Chenopodiaceae
(goosefoot), Plantago (plaintains or fleaworts) and Rumex (docks and sorrels) at
Piermont, and Typha followed by Poaceae (true grasses) and Phragmites (common reed) at Iona, became markedly more abundant following European contact. Pollen evidence from both Piermont and Iona indicates that regionally, these herbaceous plants displaced trees, which were likely felled for timber and to clear land for settlement and agriculture.
Pederson et al. (2005) also examined the rate of sediment deposition at Piermont tidal marsh. This study assumed constant accumulation of sediment at Piermont between accelerator mass spectrometry-dated layers, lessening the precision of these rates. Despite this limitation, however, there was a marked increase in sediment deposition before and after European arrival, dated based on historical information to 1681 CE. From 1418-
1697 CE, sediment accumulated at a rate of 0.11-0.14 cm/yr, whereas from 1697 CE to the present, this value more than doubled to 0.29 cm/yr.
Peteet (2005) performed loss-on-ignition analysis to determine relative proportions of organic and inorganic content at four marshes in the Hudson-Raritan
Estuary: Joco and Yellow Bar (in Jamaica Bay), Saw Mill Creek (on Staten Island) and
Piermont (Figure 1). This ratio is significant because it can be used to make inferences about past anthropogenic activity (Sritrairat 2012; Sritrairat et al. 2012; Peteet et al. 2006;
Peteet 2005; Pederson et al. 2005). Joco, Yellow Bar, and Saw Mill Creek all demonstrate a marked increase in proportional organic material following European
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contact. In actuality, though, the organic mass remains consistent with pre-contact levels, while the inorganic mass declines based on loss-on-ignition analysis. Peteet (2005) postulated that this shift resulted from dam construction on tributaries, which would have prevented passage of heavier inorganic sands and silts, but allowed lighter organics to flow past them (Peteet et al. 2006). However, the Piermont core data presents a more complex history. Like Joco, Yellow Bar, and Saw Mill Creek, inorganic content has declined at Piermont since approximately 653 CE to the present day, with the exception of a unique spike from 1700-1875 CE, immediately following European colonization of the area (Peteet et al. 2006). Peteet et al. (2006) correlated this increase to rapid land clearing, which decreases overall organic content and can cause erosion due to increased susceptibility of upland sediments to water and wind events after the removal of vegetation. Erosion, in turn, can facilitate a rapid deposition of material, which is largely inorganic (Sritrairat 2012). This increased inorganic content could also result from industrialization, which can cause metal pollution due to heavy metals in runoff
(Bromberg Gedan et al. 2009).
Based on these previous studies, there are clearly significant local variations as well as regional patterns in climate, sediment history, biota and human land use within the Hudson River system. By examining the archaeological and historical record, in combination with peat analysis, this study aims to answer the following questions: (1) In what ways and how much has anthropogenic activity altered the tidal marsh ecosystems of Haverstraw?; (2) What shifts in species composition, sedimentation rates, and proportion of organic/inorganic matter are apparent?; and (3) Specifically, does there
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seem to be exacerbated alteration of the ecosystem after European arrival as compared to indigenous impacts?
Through an analysis of sediment cores from the tidal marsh ecosystem of
Haverstraw, New York, bordering the Hudson River Estuary, a high-resolution paleoecological record focused on ratios of inorganic:organic matter and relative abundances of plant species over a temporal scale was constructed. This data set was examined in combination with a chronology of human occupation in the area as evidenced by archaeological sites and historical documentation. By correlating ecological and anthropological data, effects of past anthropogenic activity were assessed, on
Haverstraw specifically, as well as the tidal marsh ecosystem more generally, and ramifications of future development in the area were suggested.
STUDY SITE
Haverstraw Bay, the widest part of the Hudson River, is the northernmost part of the Lower Hudson River Estuary, which extends from Battery Park at the southern tip of
Manhattan. It is bordered to the west by the villages of Haverstraw and Stony Point, New
York. The bay is significant in its own right as an estuary; however, the focus of this research was the tidal marsh ecosystems that surround it, specifically those that comprise the North Rockland waterfront. According to data, from October 2014, Haverstraw Bay had a salinity level of 5.5 parts per thousand, although, since 2006, levels have varied both seasonally and annually from 0.1 to 8.4 parts per thousand, with a mean of 3.1 parts per thousand (Riverkeeper 2015). The majority of these wetlands extend westward from
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Grassy Point to the eastern edge of Lowland Town Park, as well as south to Bowline
Point (Kiviat 2012, Figure 2).
Figure 2: Approximate range of tidal marshes west of Haverstraw Bay (Google Maps, modified by the author).
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Based on past ecological assessments of the area, the Haverstraw tidal marshes are dominated by common reed (Phragmites australis australis). There are also large patches of hybrid cattail (Typha X glauca) and sweetflag (Acorus). Foley and Tauber
(1951) state that P. australis was present but not dominant, whereas purple loosestrife
(Lythrum salicaria), another invasive species, was widespread. Focht (1975) noted the presence of wild rice (Zizania), T. glauca, nut sedge (Cyperus), water barnyard grass
(Echinochloa walter), Scirpus (Scirpus s.l.), Acnida (Amaranthus cannabinus), arrowhead (Sagittaria), arrow arum (Peltandra virginica), Acorus, Polygonums
(Polygonum), swamp mallow (Hibiscus moscheutos) and pickerelweed (Pontederia cordata). Weinstein (1977) encountered many of the same species, including T. glauca,
P. australis, big cordgrass (Spartina cynosuroides), smooth cordgrass (S. alterniflora), P.
virginica and H. moscheutos. Buckley and Ristich (1976) listed 68 plant species occupying Haverstraw Marsh. These included several rare species, including buttonbush dodder (Cuscuta cephalanthi), saltmarsh aster (Symphyotrichum subulatum), catfoot
(Pseudognaphalium helleri micradenium), heartleaf plaintain (Plantago cordata), spongy
arrowhead (S. montevidensis), straw sedge (Carex straminea), Torrey’s rush (Juncus
torreyi) and troublesome sedge (C. molesta; Buckley and Ristich 1976; NYSDEC 2014).
METHODS
Sediment coring
Three cores (HAV-001, HAV-002 and HAV-003) were extracted from the
uppermost northwest corner of the tidal marsh area in Haverstraw, New York in October
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of 2014 using a 10 cm diameter Dachnowski corer. This particular section is dominated
at present by Acorus (Peteet, personal communication) (Figure 3).
Figure 3: Acorus field from which cores were extracted.
In all three cases, 1 m of sediment was retrieved. Each core was individually
wrapped in polyethylene and an outer layer of aluminum foil and then placed in a plastic
tube. Prior to analysis, they were stored horizontally at 40 ºF in the Lamont-Doherty Core
Repository. HAV-001 was used for both macrofossil and loss-on-ignition analysis. Prior
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to processing, it was split vertically, and one half was returned to the Core Repository for archival purposes. The other half was then segmented into 24 sections, each consisting of
4 cm of sediment in depth.
Loss-on-ignition
The percentage of organic matter was calculated using loss-on-ignition (LOI) analysis for each 4 cm section of HAV-001 (Dean 1974). One cc of sediment was extracted from each of these 24 segments and placed in porcelain crucibles. These samples were first weighed while still wet and then dried at 100 ºC for 24 hours. The dry weight was then determined before they were combusted in a muffle furnace at 450 ºC for 2 hours. They were weighed once more post-combustion, and the proportion of organic content was calculated for each sample according to this equation:
Loss-on-ignition (%) = Dry weight – Combusted weight x 100 Dry weight
Macrofossils
After 1 cc was removed from the vertical half of HAV-001 being utilized for analysis to determine loss-on-ignition, the remaining sediment was washed through 0.500 and 0.125 mm screens into a beaker. Seeds, charcoal, insects, foraminifera, leaves, stems, needles, and any other organic material exhibiting symmetry were identified for each 4 cm segment using a dissecting microscope at magnifications of up to 80 X. These objects were picked from the petri dish using tweezers and suspended in vials of distilled water and then kept in a refrigerated environment.
These various macrofossils were identified to the most specific possible taxonomic group using photographs, drawings and descriptions in seed and fruit identification manuals, botanical publications, the United States Department of
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Agriculture’s online PLANTS database, and the Peteet lab’s reference collection and slides (Breggren 1981; Britton and Brown 1970; Fassett 1957; Fernald 1970; Hotchkiss
1970; Katz et al 1965; Knobel 1980; Martin and Barkley 1973; Montgomery 1977;
USDA 2014).
X-ray Fluorescence spectroscopy
Approximately 15 cc of sediment was extracted from each 4 cm section of the remaining half of core HAV-001. It was placed into the core freezer at Lamont-Doherty
Earth Observatory for 3 hours before being freeze-dried at -47 °C. These sediment samples were homogenized using a mortar and pestle cleaned with isopropyl alcohol, and then prepared for X-ray Fluorescence spectroscopy (XRF). They were analyzed for chemical composition using an Innov-X Alpha series 4000 XRF spectrometer, following protocols detailed by Kenna et al. (2011). Each analysis included two 180s measurements using the soil protocol. The samples were first analyzed in standard mode and then using the Light Element Analysis Protocol (LEAP). Reported results for potassium (K) and titanium (Ti) are those obtained with LEAP, as Kenna et al. (2011) found that this protocol produced a higher degree of correlation between instrument response and element concentration than standard mode for these particular elements.
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RESULTS
Loss-On-Ignition (LOI)
LOI analysis suggests relatively constant proportions of organic matter
throughout the depositional history (Figure 4). The mean % LOI calculated over the entire core of HAV-001 is 29% (SD = 9.16). Nineteen of the 24 segments (79%) have organic contents between 21% and 37%. The two zones with the highest % organic matter (52% and 53% respectively) are adjoined, spanning from 64-72 cm in depth.
Figure 4: Result of loss-on-ignition analysis for HAV-01 core, 0-95 cm. Illustrates relatively constant inorganic:organic ratio, with the exception of two pronounced organic maxima, at 68 and 72 cm respectively.
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Macrofossils
Macrofossil analysis has identified many of the same species identified by the floristic surveys of Foley and Tauber (1951), Focht (1975), Buckley and Ristich (1976) and Weinstein (1977). Throughout the core, there is evidence of Boehmeria cylindrica
(smallspike false nettle), Typha (cattail), Scirpus (bulrush), Polygonum (knotgrass),
Carex (sedges, both lenticular and trigonous), Cyperus schweinitzii (Schweinitz’s flatsedge), Acorus americanus and Arabis (rockcress) (Figure 5). Counts of Phragmites australis remain fairly low and are present above 75 cm, whereas Lythrum salicaria
(purple loosetrife) is present only in the top 40 cm. Typha is also only present in the top of the core, occuring above a depth of 45 cm. Unknown Seed A, an approximately 1.0 x
0.5 x 0.5 mm oval fuzzy gray seed, was the most abundant species found in the core and increased in abundance from its first appearance at 45 cm to 15 cm, when it was no longer encountered (Figure 6). Chitin from insect exoskeletons was found throughout the core, and a fish vertebra was identified in Sample 2 (4-8 cm).
Figure 5. Distribution of macrofossils encountered by depth.
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Figure 6: Unknown Seed A.
X-ray Fluorescence spectroscopy
Levels of lead (Pb) and zinc (Zn) mirror each other closely (Figure 7). They have a high positive linear correlation (adjusted R2 = 0.8563, Figure 8). The concentrations of
both elements are relatively consistent from the bottom of the core until the 50-54 cm
interval, ranging from 5-17 ppm and 48-79 ppm respectively. Within these 4 cm at 58
cm, Pb levels almost double, increasing from 17 to 28 ppm. Zn increases considerably as
well, to 93 ppm, well above the previous maximum of 79 ppm. The levels of both
elements continue to rise quickly as depth decreases from 50 to 26 cm and peak at this
point, reaching maximum concentrations of 156 ppm (Pb) and 235 ppm (Zn). All more
recent intervals are characterized by declining levels of these elements. Pb levels have
dropped off more precipitously, though, with a continuous decrease in every interval.
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From the high point of 156 ppm, levels have decreased to 59 ppm at the most recent analyzed point, 4 cm below the surface. This value is only 37.82% of the maximum level within the core. Zn levels, on the other hand, have only declined slightly overall and continue to oscillate. Concentration of this element was measured at 198 ppm 4 cm below surface level, which represents 84.26% of the core maximum.
Figure 7: Result of XRF spectroscopy illustrating lead (Pb) and zinc (Zn) levels with corresponding depth. The graphs illustrate low, constant levels until 58 cm, when the concentrations of both elements begin increasing. Levels of Pb and Zn then began to decline at 25 cm, although Pb has decreased more drastically to the present day.
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Figure 8: Linear model fitted to express the correlation between concentrations of zinc (Zn) and lead (Pb). Adjusted R2 = 0.8563.
Concentrations of potassium (K) and titanium (Ti) mirror each other closely
(Figure 9). They do not, however, share as significant a correlation as Pb and K (adjusted
R2 = 0.5948, Figure 10). Adjusting for log(concentration) did not markedly improve this
correlation (adjusted R2 = 0.6272). They are moderate in the deepest analyzed sample (90 cm), respectively 14,183 ppm and 3532 ppm. Both then increase, to 15,758 (K) and 4965
(Ti) at a depth of 74 cm. This value represents the maximum potassium concentration for the entire core. At this point, they plummet to their lowest depths in the core, 9385 ppm
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and 2762 ppm, before increasing to levels of 14,957 ppm (K) and 5017 ppm (Ti) at a depth of 50 cm. This value represents the maximum titanium concentration for the entire core. These two elements have remained at relatively stable levels between 50 cm and modern ground surface, only oscillating up and down slightly in tandem with each other.
Figure 9: Result of XRF spectroscopy illustrating potassium (K) and titanium (Ti) levels with corresponding depth. Illustrates initially moderate levels, with decline at 65cm and then increase to 50cm. Both elements then oscillate but with overall decline until present.
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Figure 10: Linear model fitted to express the correlation between concentrations of potassium (K) and titanium (Ti). Adjusted R2 = 0.5948.
DISCUSSION
Loss-On-Ignition (LOI)
High LOI values have been reported in other Hudson River marsh cores at
Piermont (Pederson et al. 2005), Iona (Peteet et al. 2006), and Tivoli (Sritrairat et al.
2012). Dates obtained from Accelerator Mass Spectrometry (AMS) radiocarbon dating
situate these maxima within the warm, dry Medieval Warm Period (MWP), which lasted
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from approximately 950-1250 CE (Mann et al. 2009). This correlation is understandable, as organic material is a known indicator of warming events: charcoal evidences fire events, which occur most frequently in warm, dry climates (Maenza-Gmelch 1997a;
Maenza-Gmelch 1997b); however, fire events can also be the result of increased anthropogenic activity, particularly the transition from nomadic lifestyles to sedentism and increasing population densities (Nevle et al. 2011). Rates of sedimentation differ
considerably among marsh ecosystems within the Hudson River area, ranging from 0.1-
0.7 cm/yr (Peteet et al. 2011). It is, therefore, difficult to approximate a chronology for the tidal marshes of Haverstraw without AMS radiocarbon dates. For example, the top
1m of cores from Piermont, Iona, and Tivoli marshes encompass approximately 1580
CE-present (Pederson et al. 2005), approximately 1300 CE-present (Peteet et al. 2006) and 1250±90 CE (Sritrairat et al. 2012) respectively. Based on similarities in the macrofossil record and changes in LOI, as well as local vegetation composition, land-use history and microclimate, it is currently hypothesized that the chronology of Piermont most closely resembles that of Haverstraw (Peteet 2015, personal communication).
Significantly, within both the core extracted from Piermont and HAV-001 (the core extracted from Haverstraw), there is a considerable spike in LOI that spans only a short depth, in both cases approximately 8 cm (Pederson et al. 2005). It is situated between 64 and 72 cm within HAV-001 and corresponds to approximately the same range of depths within the Piermont core (Figure 4, Pederson et al. 2005). The relatively small amount of sediment containing elevated proportional organic content indicates that it is not representative of a large-scale environmental change spanning hundreds of years
(e.g. the MWP). This type of climatic warming is represented by increases in LOI that
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span larger ranges and are less drastic; for example, at Piermont, the MWP roughly corresponds chronologically to approximately 45 cm of sediment rather than 8 cm, and to approximately 40% LOI rather than 52-3% (Pederson et al. 2005). As such, the maxima at Haverstraw probably correspond to more short-term, localized events. This increase may be indicative of a wetter time predating European settlement.
The 4 cm sections of the analyzed core that contained the least proportional carbon matter were located at respective depths of 10 and 76 cm. The former may be a result of anthropogenic activity associated with industrialization, which is known to increase inorganic content of sediment through runoff. At 10 cm below modern ground surface, LOI yielded only 13.259% organic content, representing the minimum organic:inorganic ratio for the core labeled HAV-001. The latter depth, interestingly, immediately predates the spike in organic matter, and this minimum is paralleled in the
Piermont core (Pederson et al. 2005). If the Piermont chronology is used once more as an approximation, it seems to correspond well to the period of European settlement
(Pederson et al. 2005). This event was hypothesized to increase inorganic matter at all three Tivoli coring localities, as well as Piermont, due to erosion from deforestation
(Pederson et al. 2005; Sritrairat et al. 2012). As vegetation is removed, the soil is increasingly exposed to degradation from wind and water, and decaying organic materials are no longer trapped within the sediment (Mitsch and Gosselink 2000). AMS radiocarbon dates are, however, necessary in order to correlate these changes in organic:inorganic ratios with specific environmental events.
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Macrofossils
Based on macrofossil analysis, there is a general floristic trend of increasing invasive species through time, particularly Phragmites australis (common reed) and
Lythrum salicaria (purple loosetrife). The latter, only present towards the top of the core, indicates a relatively recent invasion of the area. This hypothesis is supported by historical records, which document its introduction into estuaries of northeastern North
America by the early 1800s (Thompson et al. 1987). It is hypothesized that Seed A,
which increases drastically in abundance as depth decreases throughout the core, is also
an invasive species introduced from Europe (Figure 6). The seed bears resemblance in color, size and shape to Lythrum (loosestrife), and the possibility is being investigated
that it may be a hybrid of either multiple Lythrum species or a hybrid of loosetrife and
another genus altogether. Schoenoplectus americanus (chairmaker’s bulrush) appears in
very low quantities. Anthropological evidence indicates that this plant was used by
indigenous groups for medicinal, sustenance, basketry, clothing, weaving and fishing
purposes (University of Michigan – Dearborn 2015). It was, therefore, most likely a dominant plant in the northeastern United States at one point in time but was outcompeted by invasives and perhaps disturbed by pollution and habitat destruction.
Future analysis of deeper cores could evaluate this hypothesis.
Certain native plants, however, persevere and are still a dominant presence at
Haverstraw marsh. For example, Acorus americanus remains prevalent throughout the core, and present, informal surveys of the area illustrate its dominance (Figure 3). There are two species of Acorus with distributions in North America, specifically the northeastern United States: A. americanus, a diploid species native to the area; and
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Acorus calamus, a sterile triploid introduced by early European settlers (Thompson
2000). In many floristic surveys and herbaria, however, these two varieties are not distinguished. Some only describe A. calamus, while others synonymize the two (Haines
2000). This distinction is extremely important, though, as one is endemic to the area and the other is not a natural part of the ecosystem.
There are evident differences in leaf morphology between the two species: A.
americanus has one prominent longitudinal midvein and straight leaf margins; whereas A.
calamus has multiple raised veins and wrinkled margins on one or both sides of its leaves
(Thompson 2000, Figure 11). Based on a comparison of these characteristics with living
Acorus plants identified on the surface during the coring fieldwork, Haverstraw appears
to have a substantive population of Acorus americanus rather than Acorus calamus. This
observation is substantiated by the macrofossil record. As A. calamus is sterile, it does
not produce mature fruit or seeds, and Acorus seeds were recovered throughout the core,
even in modern subsections (e.g. 4-8 cm below surface; Haines 2000). Maps of New
York state by county also support the existence of A. americanus rather than A. calamus
in Rockland County, the location of Haverstraw (Weldy et al. 2014). A palynological
analysis of the same core is planned, which would provide additional corroboration of
this identification to the species level. The pollen of A. americanus stains when treated
with aniline blue, while A. calamus pollen does not (Packer and Ringius 1984; Thompson
1987).
The sustained occurrence of A. americanus may have implications for the stability
of other plant communities. In the similar tidal marsh ecosystems of Piermont and Iona,
for example, P. australis has been dominant since the 1960s (Pederson et al. 2005).
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Figure 11: Differences in leaf morphology between Acorus americanus and Acorus calamus, specifically the midvein and margins (Hough 2015).
As it is a dense perennial grass, it maintains a canopy throughout winter, preventing recruitment by annual seedlings and even other perennials (Leck et al. 2009).
A. americanus, however, dies back almost completely in the winter, allowing for more recruitment of non-conspecifics and a more diverse floristic community (Leck et al.
2009). Its presence benefits other trophic levels of the ecosystem as well, as native species that have long relied on A. americanus for food or shelter would still have a viable habitat at Haverstraw. For example, it is an important part of the muskrat diet
(Ondrata zibethicus), so much so that the Cree of Alberta, Canada, referred to it as
Wehkes (muskrat root) (Motley 1994; Rudgley 1998; Takos 1947). It is also an integral ecosystem fixture in that it is capable of holding soil in place, stabilizing banks of ponds or creeks to prevent erosion (Putnam et al. 2013). This plant and its rhizomes were valued by many indigenous groups, and, interestingly, disjunct populations are often found in close proximity to prehistoric settlements, indicating that these peoples likely influenced
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modern A. americanus distribution (Motley 1994; Rudgley 1998). Ethnographic evidence indicates that certain tribes not only utilized, but actively cultivated A. americanus, both
for its medicinal properties and to attract muskrats, a source of fur (Rudgley 1998).
The pervasiveness of this plant at Haverstraw, especially given its absence from
nearby tidal marshes, may indicate the presence of yet undiscovered Native American
archaeological sites in the area. If this is the case, there could be cultural as well as
biological impetus for pursuing conservation of these wetlands. This floristic continuity
in the midst of change is important to acknowledge with regards to conservation efforts in
the area. Ecosystems that have been perturbed by invasives to the point of exclusion of
native species are often seen as lost causes by government officials (Harrop 2007).
Making the case that native species continue to persist in this area alongside invasive
species is vital for persuading government bodies to pass legislation protecting these
marshlands from future development.
X-Ray Fluorescence spectroscopy
The concentration of trace metals, specifically total Pb and Zn, increases after 50
cm in depth (Figure 6). The high correlation between these two elements is expected, as
both are indicative of anthropogenic industrialization (Sritrairat et al. 2012, Figure 7).
During this time period, the brickmaking industry at Haverstraw reached its height of
productivity (HAA 2008). While the first brick kilns were constructed in the area around
1810, the process did not begin to be industrialized until 1852 (HAA 2008). Brickmaking
can involve the additives of ground coal dust and fly ash, both of which are listed by the
Agency for Toxic Substances and Disease Registry (ATSDR) as anthropogenic causes of
zinc pollution (2005). The introduction of the automobile around the turn of the century
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led to the construction of road systems surrounding Haverstraw in order to transport the finished brick products (HAA 2008). Route 9W, still the major thoroughfare running through the town of Haverstraw, was built around 1920 (HAA 2008). Around this time, then, lead pollution would have increased even more as a result of the leaded gasoline in use at the time. Zn concentrations began to increase slightly before Pb concentrations, likey because the former stemmed primarily from the brickmaking process itself, while the latter resulted from transportation necessitated by this booming industry. The increase in Pb could also have resulted from lead paint, which would likely predate the brickmaking industry altogether.
This same pattern of exponential Pb increase is evidenced at Tivoli and corresponds to the early 20th century at that site as well (Sritrairat et al. 2012). Currently, the Environmental Protection Agency (EPA) classifies soil concentrations of Pb less than
400 ppm as safe (2013). This legislation, however, does not imply that such chemistry is natural. XRF spectroscopy clearly illustrates a baseline for Haverstraw of between 5 and
17 ppm, and similar levels (<20 ppm) appear to be consistent with pre-industrial chemistry at Tivoli (Figure 10, Sritrairat et al. 2012). The dramatic increase beyond this point can be clearly correlated to anthropogenic activity. Declining Pb concentration is also associated with human-induced actions, specifically two federal regulations: (1) banning the use of lead-based paint in residences and (2) phasing out of leaded gasoline beginning in 1973. (US EPA 2013). The present Pb concentrations at Haverstraw are only one-third of the elemental maximum, serving as an important reminder that human intervention has resulted in positive actions. Indeed, the introduction of these two acts of
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legislation have drastically improved not only Haverstraw, but the condition of soil throughout the United States (US EPA 2013).
Unlike at Tivoli, however, this increase in trace metal content is not associated with an increase in the lithogenic indicators of potassium (K) or titanium (Ti, Figure 8).
This pattern may be indicative of relatively less deforestation in the area in the late 19th
and early 20th century and, therefore, less erosion and drying of the soils (Sritrairat et al.
2012). The maximum for the entire core of both K and Ti, significantly, occurs
contemporaneously with the increase in proportional inorganic material believed to be
associated with the Revolutionary War (76 cm). In addition to being burned for charcoal,
as previously discussed, trees were felled to create battlegrounds and new settlements, as
the population of various areas grew in direct proportion to increases in the number of
troops stationed there (Cronon 1983; Haagensen 1986). This deforestation would have
resulted in soil erosion and drying, resulting in increases in both K and Ti concentrations.
At Tivoli, interestingly, the Revolutionary War era does not seem to correspond to
elevated levels of either the lithogenic indicators or LOI (Sritrairat et al. 2012). Perhaps,
Haverstraw experienced more significant deforestation and erosion during the late 18th
century, while Tivoli has undergone more extensive such changes more recently. Soil
health is vital for the preservation of a viable ecosystem, as without it, plants often cannot
obtain the necessary nutrients for survival and recruitment (Mitsch and Gosselink 2000).
This deficiency can result in dominance by only a few species that can tolerate these
extreme conditions, which correspondingly decreases overall floristic and even greater
biodiversity (Mitsch and Gosselink 2000). The ability of the Haverstraw tidal marsh
ecosystem to recover from past erosional events, as well as perhaps less anthropogenic-
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induced deforestation in the present, may help to explain the notable presence of native species, such as A. americanus, that are lacking in other similar environments in the
Hudson (Peteet 2015, personal communication).
CONCLUSIONS
Although the floristic composition of Haverstraw Marsh is today characterized by intrusion of invasive species, native species continue to persist and thrive. Acorus americanus in particular, which has been outcompeted by Phragmites australis in other tidal marshes within the Hudson River watershed, seems to persist in a stable population at Haverstraw. Loss-on-ignition analysis suggests a peak in proportional inorganic matter just below the surface at 8-12 cm. This change in composition is likely the result of industrialization which may have polluted the tidal marsh and surrounding watershed with runoff. It also defines two LOI minima which may correspond to European settlement and then industry. XRF spectroscopy illustrates increasing heavy metal pollution, probably also resulting from the industrial era, and the levels of these elements have declined more recently. It additionally indicates a lack of considerable lithogenic changes, contributing to the stability of the ecosystem. This study has implications regarding conservation of these wetlands, as it illustrates the viability of this ecosystem despite the introduction of invasive species.
RECOMMENDATIONS
To learn more about the climatic history of Haverstraw over a longer timescale, it would be advantageous to extract a core that extends to the very bottom of the tidal
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marsh. Once procured, not only could he macrofossils and floristic composition of the marsh since its initial formation be analyzed, but the formation of this ecosystem could also be dated. If it predates any human activity in the region, it would be possible to construct a botanical baseline that eliminates anthropogenic influence. In order to better
understand the paleonenvironment on a regional rather than local scale, palynological
analysis on the same core will be performed. This additional source of information would
also allow for greater facility of comparison and correlation with other tidal marsh cores
in the Hudson River region; one would expect the pollen record to be fairly similar
amongst the sites, enabling investigations of the relationship between micro- and
macroscale environmental changes. Lastly, the results of this study will be shared with
local policymakers to discuss the conservation status of the area, with the hopes of
postively impacting the future of this important ecosystem.
ACKNOWLEDGEMENTS
I would like to thank my mentor, Dorothy Peteet, for sharing her immense breadth
of knowledge regarding macrofossil analysis and the paleoecology of the Hudson River
system. I would also like to profusely thank Tim Kenna and Clara Chang for their
assistance with setting up the XRF and calibrating the data. I am grateful to Jenna
Lawrence, my advisor, and Matt Palmer, my second reader, for their invaluable advice, as
well as the rest of the Ecology, Evolution and Environmental Biology department and the
entire Earth and Environmental Sciences department at Columbia University. By
organizing the research process into helpful stepstones, it has been a much more feasible,
less stressful endeavor. I would also like to thank the Hudson River Foundation for
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awarding me the Tibor T. Polgar Fellowship to continue this research beyond this class.
Lastly, I would like to thank Adam Watson, Nick Dunning and Vern Scarborough for introducing me to the importance of soil coring and paleoecology to archaeological excavations.
V-37
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