Chapter 9

Maps of Benthic Foraminiferal Distribution and
Environmental Changes in Long Island Sound
between the 1940s and the 1990s


By
Ellen Thomas1, Taras Gapotchenko 1, Johan C. Varekamp1,
Ellen L. Mecray2 and Marilyn R. Buchholtz ten Brink2
 

Table of Contents
Introduction
Methods
Benthic Foraminiferal Distributions
Acknowledgments
References
Figure Captions
Table Captions
Appendix I - SEM Micrographs
Digital Data and Metadata
Back to Table of Contents

INTRODUCTION

Long Island Sound (LIS) is a large, urban estuary with a reduced salinity (22-32 ppt in bottom waters).  The  "quiet water" regions in LIS, especially in the western basins, experience periodic, seasonal bottom water hypoxia (www.epa.gov/region01/eco/lis/hypox.html)  (dissolved O2<3 ml/L) or anoxia (dissolved O2<1 ml/L), with severe consequences to the biota, as described in the Long Island Sound Study (www.epa.gov/region01/eco/lis).  Low-oxygen conditions usually reach their peak in July-August, when thermal stratification is most pronounced (New York State Department of Environmental Conservation And Connecticut Department Of Environmental Protection, 1999).  This pervasive anoxia in the western basin of LIS was first observed in 1971 (Parker and O'Reilly, 1991).  When nutrients are abundant, algal blooms occur during the periods of stratification.  The algal blooms are more intense in western LIS (Sun and others, 1994).  The complex interactive process of oxygen loss in the bottom waters, including the temporal and spatial variations in circulation, mixing, and biological processes, is not well understood.

The health of the LIS ecosystem is further affected by sediment pollution.  Atmospheric deposition and river-borne fluxes of pollutants, both organic and metallic, led to the pollution of the top section of sediments (Mecray and Buchholtz ten Brink, 2000; Varekamp and others, 2000). In addition, some locations became by outflow from sewage treatment plants (Buchholtz ten Brink and others, 2000).
Records of abundant biota which easily fossilize may reflect the effects of anthropogenic and natural environmental changes in LIS. Benthic foraminifera are such biota and are abundant in LIS. A detailed study of LIS benthic foraminifera was conducted in the late 1940s (Parker, 1952), followed by an exhaustive study in the 1960s (Buzas, 1965).  LIS faunas are classified as 'marginally marine' and typically have a low species diversity.  The most abundant species have high tolerances for fluctuations in temperature and salinity, as well as for low oxygen conditions and environmental pollution (Alve, 1995).

We compare data on the composition of benthic foraminiferal assemblages in LIS in 1996/1997 with the data collected in 1948 (Parker, 1952) and the early 1960s (Buzas, 1965).
 

METHODS

We selected 42 samples for foraminiferal analysis.  Our samples cover a depth range between 5-35 m, and a longitudinal range between 72.407 and 73.747 degrees W.  Parker's (1952) data were collected in the eastern part of LIS, between 72.492 and 73.098 degrees W, and between 6.5 and 29 m depth. Buzas (1965) presents the largest data set over a depth range (3- 43 m).  His samples range in longitude between 72.852 and 73.700 degrees W.

The grab samples were processed as described in Mecray and Buchholtz ten brink (2000). Part of the freeze-dried samples was wet-sieved over a 0.062-mm screen for foraminiferal analysis. The complete fraction larger than 0.062 mm was used.  The grab samples were not stained to detect living specimens, so we could only study total faunas (living and dead specimens), and compare these with similar data in Buzas (1965).  At several locations a sub-sample of the grab samples was placed in formaldehyde.  These samples were not buffered for long-term storage, and all carbonate material was dissolved at the time of analysis.  We processed and studied several of these samples in order to determine whether agglutinant specimens had been affected by freeze-drying. We found no differences between agglutinant taxa abundance in the formaldehyde and the freeze-dried samples.  We prepared splits of the samples to contain at least 100 specimens of foraminifera. Specimens were picked from all samples, identified to species level, and stored in foraminiferal slides.  SEM micrographs of selected foraminifera are shown in Appendix 1.
 

BENTHIC FORAMINIFERAL DISTRIBUTIONS

Relative abundances of the most common species of foraminifera are shown in Table 1.  This table may also be viewed or downloaded as a Microsoft Excel file (table1.xls).  Numerical abundances are shown in Table 2 and are also available as a Microsoft Excel file (table2.xls). Benthic foraminifera are useful indicator species for monitoring environmental changes in near-shore, environmentally-stressed regions. We compared faunal and isotope data
Figure 1 - Location of 1996/1997 sampleson benthic foraminifera collected in 1996/1997 with data published on faunas collected in the early 1960s by Buzas (1965) and in the late 1940s by Parker (1952).  Distributional maps and plots show the relative abundances of E. excavatum clavatum (Micrograph 1; Figs. 1, 2), Buccella frigida (Micrograph 2 -ventral view; Micrograph 3 - dorsal view; Figs. 3, 4), Eggerella advena (Micrograph 4; Figs. 5, 6), and Ammonia beccarii (Micrograph 5- ventral view; Figure 7 - Location of samples collected in 1996/1997, 1961/1962 and 1948.Micrograph 6 - dorsal view; Figs. 7, 8) for the late 1940s, early 1960s, and late 1990s.  The low diversity benthic foraminiferal faunas of the 1960s were dominated by Elphidium excavatum clavatum, with common Buccella frigida and Eggerella advena. Elphidium incertum (Micrograph 7) was present in many samples; Trochammina squamata (Micrograph 8 - ventral view; Micrograph 9 - dorsal view) was rare.

The 1996/1997 faunas (Table 1) were still dominated by Elphidium excavatum clavatum and Buccella frigida, and E. incertum was present in many samples, T. squamata was rare.  Eggerella advena, however, was rare in all samples, andFigure 9 - Ammonia-Elphidium index for 1996 samples. species diversity decreased.  Ammonia beccarii was rare (<5%) in 1961, but formed up to 27% of the assemblage in western LIS in 1996/1997. As a result the Ammonia-Elphidium index (Fig. 9), high values of which have been linked to low oxygenation in the Gulf of Mexico (Sen Gupta and others, 1996), increased strongly in western LIS, where seasonal hypoxia is most pronounced (www.epa.gov/region01/eco/lis/lodo.html).  The A-E index shows a strong, positive correlation with counts of the bacterial spore Clostridium perfringens, a sewage outfall indicator (Buchholtz ten Brink and others, 2000).

What caused these dramatic faunal shifts? A comparison of oxygen isotope data for E. excavatum clavatum collected in the 1960s and 1990s (Thomas and others, 2000) suggests no significant salinity changes over this time period.  Carbon isotope data suggest that organic matter oxidation in LIS increased dramatically over the last 35 years, especially in western LIS. Core studies (Varekamp and others, 2000) indicate that the abundance of the sewage indicator spore increased over the last few decades.  Therefore we suggest that both the bloom in A. beccarii (Fig. 9) in western LIS and the lighter carbon isotope values may be related to increased sewage inputs over the last 35 years.

To open georeferenced displays of the distributional themes in ESRI's ArcView program make sure the application is loaded on your computer.  Users should go to the lisound directory located on the top level of this CD-ROM and double click on the lisound.apr project file.  The individual ArcView shapefiles may also be opened directly with any Arc application (e.g. ArcInfo, ArcExplorer) and can also be found on the data page.  Further detailed information can be found on the ArcView Project File page.
 

ACKNOWLEDGMENTS

We thank Zobeida Monserrate-Cruz and Polina Rabinovich for their help in picking and counting benthic foraminifera and in making the SEM micrographs, Judy Commeau for making the SEM micrographs in Appendix 1, and Dan McCorkle for sampling assistance. We are also grateful to Tim White and Copeland McClintock at the Yale University Peabody Museum for their help in access to the foraminiferal collection of Buzas. ET and JCV acknowledge financial support from  the Connecticut Sea Grant College Program (grant nr.DSG443 R/ER-2), from Wesleyan University, and from the U. S. Geological Survey Coastal and Marine Geology Program.
 

REFERENCES

Alve, E., 1995, Benthic foraminiferal responses to estuarine pollution: An overview: Journal of Foraminiferal Research, v. 25, p. 190-203.

Buchholtz ten Brink, M. R., Mecray, E. L. and Galvin, E. L., 2000, Clostridium perfringens in Long Island Sound Sediments: An urban sedimentary record: Thematic Section, Journal of Coastal Research, in press.

Buzas, M. A., 1965, The distribution and abundance of Foraminifera in Long Island Sound: Smithsonian Institution Miscellaneous Collection, v. 149, no.1, p. 1-88.

Mecray, E.L. and Buchholtz ten Brink, M.R., 2000, Contaminant distribution and accumulation in the surface sediments of Long Island Sound: Journal of Coastal Research, Thematic Section, in press.

New York State Department of Environmental Conservation And Connecticut Department Of Environmental Protection, 1999, http://dep.state.ct.us/wtr/lis/tmdl.htm

Parker, F. L., 1952, Foraminiferal distribution in the Long Island Sound - Buzzards Bay area: Bulletin Museum Comparative Zoology, Harvard College, v. 106, no.10, p. 428-473.

Parker, C. A. and O'Reilly, J. E., 1991, Oxygen depletion in Long Island Sound: a historical perspective: Estuaries, v. 14, p. 248-264

Sen Gupta, B. K., Turner, R. E., and Rabalais, N. N., 1996, Seasonal oxygen depletion in continental shelf waters of Louisiana: historical record of benthic foraminifers: Geology, 24, p. 227-230.

Sun, M.-Y.; Aller, R. C. and Lee, C., 1994, Spatial and temporary distributions of sedimentary chloropigments as indicators of benthic processes in Long Island Sound: Journal of Marine Research, v. 52, p. 149-176.

Thomas, E., Gapotchenko, T., Varekamp, J. C., Mecray, E. L., and Buchholtz ten Brink, M. R., 2000, Benthic foraminifera and environmental changes in Long Island Sound: Journal of Coastal Research, Thematic Section, in press.

Varekamp, J. C., Buchholtz ten Brink, M.R., Mecray, E. L. and Kreulen, B.,2000, Mercury in Long Island Sound sediments: Thematic Section, Journal of Coastal Research, in press.
 

FIGURE CAPTIONS

Figure 1. Map of Long Island Sound showing location of the samples collected in 1996/1997 (Thomas and others, 2000), in 1961/1962 (Buzas, 1965) and in 1948 (Parker, 1952). Symbols indicate the year that a sample was collected, colors indicate relative abundance of Elphidium excavatum clavatum (Fig. 2).

Figure 2. Relative abundance of Elphidium excavatum clavatum in samples collected in 1948 (Parker, 1952), in 1961/1962 (Buzas, 1965) and in 1996/1996 (Thomas and others, 2000). The color of the background at various levels corresponds with the color of the symbols in Figure 1.

Figure 3. Map of Long Island Sound showing location of the samples collected in 1996/1997 (Thomas and others, 2000), in 1961/1962 (Buzas, 1965) and in 1948 (Parker, 1952). Symbols indicate the year that a sample was collected, colors indicate relative abundance of Buccella frigida. (Fig. 4).

Figure 4. Relative abundance of Buccella frigida in samples collected in 1948 (Parker, 1952), in 1961/1962 (Buzas, 1965) and in 1996/1996 (Thomas and others, 2000). The color of the background at various levels corresponds with the color of the symbols in Figure 3.

Figure 5. Map of Long Island Sound showing location of the samples collected in 1996/1997 (Thomas and others, 2000), in 1961/1962 (Buzas, 1965) and in 1948 (Parker, 1952). Symbols indicate the year that a sample was collected, colors indicate relative abundance of Eggerella advena. (Fig. 6).

Figure 6. Relative abundance of Eggerella advena in samples collected in 1948 (Parker, 1952), in 1961/1962 (Buzas, 1965) and in 1996/1996 (Thomas and others, 2000). The color of the background at various levels corresponds with the color of the symbols in Figure 5.

Figure 7. Map of Long Island Sound showing location of the samples collected in 1996/1997 (Thomas and others, 2000), in 1961/1962 (Buzas, 1965) and in 1948 (Parker, 1952). Symbols indicate the year that a sample was collected, colors indicate relative abundance of Ammonia beccarii (Fig. 8).

Figure 8. Relative abundance of Ammonia beccarii in samples collected in 1948 (Parker, 1952), in 1961/1962 (Buzas, 1965) and in 1996/1996 (Thomas and others, 2000). The color of the background at various levels corresponds with the color of the symbols in Figure 7.

Figure 9. The Ammonia-Elphidium index (Sen Gupta and others, 1996) for the 1996/1996 samples plotted versus longitude, and compared with the number of spores of Clostridium perfringens, a sewage indicator (Buchholtz ten Brink and others, 2000).
 

TABLE CAPTIONS

Table 1.  Relative abundances of the most common species of foraminifera. A copy of this table (table1.xls) may also be downloaded in Microsoft Excel format format.

Table 2.  Numerical abundances of the most common species of foraminifera. A copy of this table (table2.xls) may also be downloaded in Microsoft Excel format format.
 

APPENDIX I - SEM Micrographs

Micrograph 1.  Elphidium excavatum clavatum
Micrograph 2.  Buccella frigida, ventral view
Micrograph 3.  Buccella frigida, dorsal view
Micrograph 4.  Eggerella advena
Micrograph 5.  Ammonia beccarii, ventral view
Micrograph 6.  Ammonia beccarii, dorsal view
Micrograph 7.  Elphidium incertum
Micrograph 8.  Trochammina squamata, ventral view
Micrograph 9.  Trochammina squamata, dorsal view


1 Wesleyan University, Middletown, CT 06459-0139
2 U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole, MA 02543 [an error occurred while processing this directive]