Prepared in cooperation with the New York State Department of Environmental Conservation

Response of Periphyton Fatty Acid Composition to 

Supplemental Flows in the Upper Esopus Creek,

Catskill Mountains, New York

Scientific Investigations Report 2015–5161

U.S. Department of the Interior

U.S. Geological Survey
1

2

3

Cover. Background photograph: Waters from the Shandaken portal entering the upper Esopus Creek in August 2009.

1. Filtering equipment used for collecting quantitative periphyton standing crop samples.

2. Periphyton growing on a rock from the upper Esopus Creek, New York.

3. Qualitative periphyton samples for fatty acid analysis.
Response of Periphyton Fatty Acid 

Composition to Supplemental Flows in the 

Upper Esopus Creek, Catskill Mountains, 

New York

By Scott D. George, Anne G. Ernst, Barry P. Baldigo, and Dale C. Honeyfield

Prepared in cooperation with the

New York State Department of Environmental Conservation

Scientific Investigations Report 2015–5161

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Director

U.S. Geological Survey, Reston, Virginia: 2016

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Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

George, S.D., Ernst, A.G., Baldigo, B.P., and Honeyfield, D.C., 2016, Response of periphyton fatty acid composition to 

supplemental flows in the upper Esopus Creek, Catskill Mountains, New York: U.S. Geological Survey Scientific 

Investigations Report 2015–5161, 22 p., with appendixes, http://dx.doi.org/10.3133/sir20155161.

ISSN 2328-0328 (online)
iii

Acknowledgments

The authors extend appreciation to Alexander J. Smith, Larry Abele, and Walter Keller (retired) 

of the New York State Department of Environmental Conservation; Tyler J. Ross of Cornell 

University; and David A. Winkler of Rensselaer Polytechnic Institute for their contributions to the 

completion of this project.

Field support was also provided by Tia-Marie Scott of the New York Water Science Center of 

the U.S. Geological Survey, and laboratory support was provided by Stephanie Sweet of the 

Northern Appalachian Research Laboratory of the U.S. Geological Survey.

v

Contents

Acknowledgments........................................................................................................................................iii

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Fatty Acids..............................................................................................................................................3

Study Objective and Design Concepts..............................................................................................3

Purpose and Scope ..............................................................................................................................4

Methods...........................................................................................................................................................4

Study Scope and Area .........................................................................................................................4

Periphyton Sampling ............................................................................................................................4

Fatty Acid Analysis ...............................................................................................................................5

Standing Crop and Diatom Analysis ..................................................................................................6

Water Quality.........................................................................................................................................6

Statistical Analysis ...............................................................................................................................6

Results .............................................................................................................................................................7

Fatty Acids..............................................................................................................................................7

Water Quality and Fatty Acid Relations ............................................................................................7

Standing Crop......................................................................................................................................10

Diatoms.................................................................................................................................................12

Response of Periphyton Fatty Acid Composition to Supplemental Flows..........................................12

Spatial Patterns...................................................................................................................................12

Seasonal Differences.........................................................................................................................13

Limitations of Study and Recommendations for Future Work .............................................................15

Summary........................................................................................................................................................15

References Cited..........................................................................................................................................16

Appendix 1. Fatty Acid Composition of Periphyton at Sites Sampled on the Main Stem and 

Tributaries of the Upper Esopus Creek, New York....................................................................20

Appendix 2. Water-Quality Parameters and Daily Stream Discharge Collected between 

August 26 and November 3, 2009, at Six Sites on the Upper Esopus Creek, 

New York..........................................................................................................................................21

Appendix 3. Chlorophyll a, Ash-Free Dry Mass, and Diatom Assessment Profile Score for 

Sites Sampled on the Main Stem and Tributaries of the Upper Esopus Creek, 

New York..........................................................................................................................................22
Figures

1. Map showing location of 20 sampling sites on the main stem and tributaries of the

upper Esopus Creek in the Catskill Mountains, southeastern New York ............................2

2. Nonmetric multidimensional scaling ordination based on arcsine-square-roottransformed proportion data of periphyton fatty acid content collected during 

August 2009 from sites upstream or downstream from the Shandaken portal, or 

on a tributary of the upper Esopus Creek, New York..............................................................9

3. Nonmetric multidimensional scaling ordination based on arcsine-square-roottransformed proportion data of periphyton fatty acid content collected during 

August and November 2009 from sites on the upper Esopus Creek upstream or 

downstream from the Shandaken portal, New York.............................................................10

4. Nonmetric multidimensional scaling ordination based on square-root-transformed

species abundance data of diatom assemblages collected during August 2009 from

sites upstream or downstream from the Shandaken portal, or on a tributary of the

upper Esopus Creek, New York ................................................................................................13

5. Nonmetric multidimensional scaling ordination based on square-root-transformed

species abundance data of diatom assemblages collected during August and

November 2009 from sites on the upper Esopus Creek upstream or downstream

from the Shandaken portal, New York ....................................................................................14

Tables

1. Stream name, site identification number, drainage area, and location of 20 sampling 

sites along the main stem and tributaries of the upper Esopus Creek, New York.............5

2. Summary of one-way analysis of variance results comparing the relative

abundance of individual fatty acids and summary metrics for periphyton from 

sites along the main stem and tributaries of the upper Esopus Creek, New York.............8

3. Summary of one-way analysis of variance results comparing periphyton standing

crop, diatom community integrity, and water-quality parameters from sites along

the main stem and tributaries of the upper Esopus Creek, New York ...............................11

vi
vii

Conversion Factors

International System of Units to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square kilometer (km2) 247.1 acre

square kilometer (km2) 0.3861 square mile (mi2)

Volume

liter (L) 33.82 ounce, fluid (fl. oz)

Flow rate

cubic meter per second (m3/s) 35.31 cubic foot per second (ft3/s)

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

Surface density

milligram per square centimeter (mg/cm2) 0.000227573 ounce per square inch (oz/in2)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as

°F = (1.8 × °C) + 32.

Datum

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Supplemental Information

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius 

(μS/cm at 25 °C). Suspended sediment concentrations are given in milligrams per liter (mg/L). 

Nephelometric turbidity unit (NTU) is a measure of turbidity in a water sample, roughly 

equivalent to the formazin turbidity unit (FTU) and Jackson turbidity unit (JTU).
viii

Abbreviations

AFDM ash-free dry mass

ANOSIM analysis of similarity

ANOVA analysis of variance

chl a chlorophyll a

DAP diatom assessment profile

FAME fatty acid methyl esters

MDS nonmetric multidimensional scaling

MUFA monounsaturated fatty acid

NTU nephelometric turbidity units

PUFA polyunsaturated fatty acid

SAFA saturated fatty acid
Response of Periphyton Fatty Acid Composition to 

Supplemental Flows in the Upper Esopus Creek, 

Catskill Mountains, New York

By Scott D. George, Anne G. Ernst, Barry P. Baldigo, and Dale C. Honeyfield

Abstract

Fatty acid analysis of periphyton is an emerging tool for 

assessing the condition of a stream ecosystem on the basis 

of its water quality. The study presented in this report was 

designed to test the hypothesis that periphyton communities 

have a fatty acid profile that can detect excessive turbidity and 

suspended sediment. The fatty acid composition of periphyton 

was assessed during two seasons upstream and downstream 

from an underground aqueduct that provides supplemental 

flows, which are a potential source of turbidity and suspended 

sediment on the upper Esopus Creek, New York. These data 

were compared with measurements of periphyton standing 

crop, diatom community structure and integrity, and basic 

water-quality parameters. Periphyton standing crop and 

diatom community integrity indicated little evidence of 

impairment from the supplemental flows. The relative 

abundances of two physiologically important fatty acids, 

γ-linolenic acid (18:3ω6) and eicosapentaenoic acid (20:5ω3), 

were significantly lower downstream from the supplemental 

flows and multivariate analyses of fatty acid profiles 

identified significant differences between sites upstream and 

downstream from the supplemental flows. Individual fatty 

acids and summary metrics, however, were not significantly 

correlated with turbidity or suspended sediment. Together, 

these results indicate that the supplemental flows may cause 

some measurable effects but they do not constitute a major 

disturbance to the periphyton community on the upper Esopus 

Creek. Fatty acid analysis may have potential as a tool for 

monitoring changes in periphyton nutritional composition that 

may reflect water quality and ecosystem health but needs to be 

further evaluated around a more definitive source of waterquality impairment.

Introduction

The U.S. Geological Survey and the New York State 

Department of Environmental Conservation used fatty 

acid analysis of periphyton to characterize the local water 

quality and ecosystem condition of the upper Esopus Creek, 

New York (fig. 1) in August and November 2009. The study 

detailed in this report evaluated the hypothesis that periphyton 

communities (composed of benthic algae and microorganisms) 

have a fatty acid profile that allows for the detection of waterquality impairment, specifically from excessive turbidity and 

suspended sediment. Periphyton fatty acid composition and 

standing crop (ash-free dry mass [AFDM] and chlorophyll 

a [chl a]), structure and integrity of diatom communities, 

and water-quality parameters were analyzed and compared 

upstream and downstream from the Shandaken portal, 

New York (fig. 1), which provides supplemental flows to the 

upper Esopus Creek that are sometimes turbid in nature.

The portal is the terminus of a 29-kilometer (km) 

underground aqueduct, the Shandaken Tunnel, which diverts 

water from the Schoharie Reservoir in the Mohawk River 

drainage into the upper Esopus Creek as part of the New 

York City water supply system. Discharge from the portal can 

increase natural flows on the upper Esopus Creek by a factor 

of two or more (Burns and Gazoorian, 2015) and is often more 

turbid than ambient receiving waters. The portal is a source of 

controversy among local residents and anglers who perceive 

it as delivering turbid water that degrades the aesthetic and 

biological integrity of the stream (Cornell Cooperative 

Extension of Ulster County and others, 2007). Assessments of 

diatoms and macroinvertebrates conducted by the New York 

State Department of Environmental Conservation, however, 

have produced inconsistent results concerning the effect of 

the portal on these assemblages (Bode and others, 1995, 

2001; Smith, 2013). Consequently, the overall effect of the 

altered suspended sediment and flow regimes on aquatic biota 

remains unclear. The contents of this report will help bridge 

this knowledge gap by analyzing the fatty acid content of 

periphyton, which comprises the base of the aquatic food web, 

throughout the watershed.

The condition of aquatic ecosystems is often assessed 

by using various biological components of the food web, 

such as invertebrates or fish (Barbour and others 1999; 

Moulton and others, 2002). Although these methods are 

very useful for predicting water quality, such assemblages 

are only surrogates for the essential nutrients present in the 
2 Response of Periphyton Fatty Acid Composition to Supplemental Flows in the Upper Esopus Creek, New York

2 4 6

2 4 6

8 MILES 0

8 KILOMETERS 0

EXPLANATION

Tributary sampling site and identification numberUpstream sampling site and identification numberDownstream sampling site and identification number

* Sampled during August and November 2009

D–4

U–0

T–8

T–7

T–0

T–9

T–5

T–1

T–3

T–2

T–6

T–4

D–6*

U–3*

U–2*

D–4a*

D–3b*

U–3a*

D–5

D–4b

74°10' 74°20' 74°30'

42°10'

42°

ULSTER CO

ULSTER CO

DELAWARE CO

DELAWARE CO

GREENE CO

GREENE CO

Base from U.S. Geological Survey digital data, 1:150,000Transverse Mercator projection, zone 18N

Shandaken

portal

T–1

U–0D–4 Ashokan Reservoir

Shandaken Tunnel

Fox Hollow 

Creek

Birch Creek

Esopus

Creek

Little Beaver Kill

Beaver Kill

S ot ny C ol

ve Creek

B or ads rt eet Hol ol

w Brook

B or ads rt eet Hol ol

w Brook

Bushnellsville CreekBushnellsville Creek

ce P Hk woll o ce P Hk woll o

Woodland Cree k

Esopus Creek

 Creek

Boiceville

Study area

Winnisook

Lake

NEW YORK

Figure 1. Location of 20 sampling sites on the main stem and tributaries of the upper Esopus Creek in the Catskill Mountains, southeastern New York. Sites indicated with U are upstream from the Shandaken portal, New York, D are downstream from the portal, and T are at tributaries of the upper Esopus Creek.
Introduction 3

system. A nutrient is considered essential to an organism 

when it cannot be synthesized internally and must be obtained 

from an external source (Arts and others, 2001; Hill and 

others, 2011) and each biological entity within the food web 

has specific nutritional requirements. If required essential 

nutrients are not produced by another organism, such as a 

primary producer, or if production of the essential nutrient is 

constrained by the physical habitat or anthropogenic factors, 

then the species will not be present.

Fatty Acids

Polyunsaturated fatty acids (PUFAs) are an example of 

essential nutrients for consumers, and primary producers are 

a key source of these essential fatty acids. Fatty acids are long 

amphipathic molecules composed of a carboxyl head and an 

aliphatic tail that, in aquatic organisms, generally ranges from 

12 to 24 carbon atoms in chain length (Napolitano, 1999). 

Fatty acids can be divided into the following classes based 

on the number of double bonds in the carbon chain: saturated 

fatty acids (SAFAs) contain no double bonds between carbon 

atoms, monounsaturated fatty acids (MUFAs) contain one 

double bond in the carbon chain, and PUFAs contain more 

than one double bond in the carbon chain. Several of the 

PUFAs such as α-linolenic acid and linoleic acid (and their 

elongation products), are considered to be dietary essential 

fatty acids for most consumers (Arts and others, 2001; 

Parrish, 2009; Hill and others, 2011). Herein however, 

essential fatty acids will be referred to as physiologically 

important to avoid confusion between an indispensable and 

conditionally indispensable fatty acid (Cunnane, 2003).

Advances in fatty acid analysis that allow for separation, 

identification, and quantification of individual long-chained 

fatty acids have enabled the use of fatty acid analysis in 

many biological and ecological applications. For example, 

identifying bacterial species using fatty acid methyl esters 

(FAME) is now a routine methodology (Moss, 1981; 

Miller, 1982; Miller and Berger, 1985; Welch, 1991). Fatty 

acids have been used successfully to describe food-web 

dynamics (Alfaro and others, 2006) and to determine the diet 

of top predators (Budge and others, 2006). Knowledge of 

the fatty acid composition of algal taxa is also being used to 

optimize production in aquaculture (Patil and others, 2007).

The use of fatty acid analysis of periphyton in 

freshwaters is emerging as a tool for assessing algal 

community structure and ecosystem health on the basis 

of water quality. McIntire and others (1969) provided one 

of the first lotic freshwater studies linking proportions of 

individual fatty acids to specific components of the periphyton 

community. The presence and relative abundance of different 

algal classes can now be determined using associated fatty 

acid biomarkers (Napolitano, 1999). For example, palmitic 

acid (16:0), palmitoleic acid (16:1ω7), and eicosapentaenoic 

acid (20:5ω3) are considered to be markers of diatom 

dominance, and α-linolenic acid (18:3ω3) is a marker of 

green algae dominance (Napolitano, 1999; Hill and others, 

2011). Because algae are the main source of physiologically 

important fatty acids in aquatic ecosystems (Parrish, 2009), 

and because water quality strongly influences the health and 

diversity of the algal community (Collins and Weber, 1978; 

Barbour and others, 1999; Larned, 2010), it follows that 

impaired water quality should lessen the diversity and quality 

of fatty acids available to consumers. Napolitano and others 

(1994) determined that chlorine-polluted streams had an 

altered fatty acid profile that indicated a shift in dominance 

from diatoms to green algae. Two recent studies were also 

completed on the response of periphyton fatty acid profiles 

in acid mine streams. Genter and Lehman (2000) determined 

that the fatty acid profiles of periphyton communities were 

different upstream and downstream from point-source metal 

inputs because of decreases in particular fatty acids. Similarly, 

Honeyfield (Dale C. Honeyfield, U.S. Geological Survey, 

unpub. data, 2010–14) determined that acid mine streams 

contained a limited number of individual fatty acids and either 

none or extremely inadequate amounts of physiologically 

important fatty acids compared with unaffected trout streams, 

which contained two to three times the number of fatty acids 

and included the entire physiologically important omega-3 

and omega-6 fatty acid families. Together, these investigations 

suggest that fatty acid analysis of periphyton can be 

used to assess water quality, although the sensitivity, and 

therefore overall utility of this method remains understudied 

and unclear.

Study Objective and Design Concepts

The primary objective of this study is to determine 

whether water delivered through the Shandaken portal has a 

deleterious effect on the nutritional quality of the food-web 

base (primary producers) in the upper Esopus Creek. It was 

hypothesized that if the portal is adversely affecting aquatic 

biota, then the fatty acid profile of periphyton downstream 

from the portal would reflect this impairment. Additionally, 

major tributaries to the upper Esopus Creek have a wide 

range of suspended sediment concentrations. If turbidity 

or suspended sediment affects the nutritional quality of 

periphyton, then changes in the proportions of physiologically 

important fatty acids may exist across a gradient of suspended 

sediment concentrations. This impairment, whether 

attributable to waters entering the upper Esopus Creek through 

the portal or to a general gradient of suspended sediment 

throughout the basin, could result in reduced diversity 

of periphyton fatty acids or a shift in fatty acid structure 

indicative of an altered periphyton community. Although the 

relation between suspended sediment and periphyton fatty 

acid composition has not been investigated, some studies have 

assessed the effect of different light levels on the fatty acid 

profile of periphyton. Cashman and others (2013) determined 

that greater light caused an increase in the proportions 

of MUFAs and short-chain PUFAs and a decrease in the 
4 Response of Periphyton Fatty Acid Composition to Supplemental Flows in the Upper Esopus Creek, New York

proportions of SAFAs and long-chain PUFAs. Somewhat 

in contrast, Hill and others (2011) determined that greater 

light levels caused an increase in the proportions of SAFAs 

and MUFAs and a decrease in the proportions of PUFAs. 

Because reduced penetration of light is considered the primary 

effect of suspended sediment on periphyton (Newcombe 

and Macdonald, 1991), periphyton fatty acid composition 

at the most turbid sites in this study might be expected 

to respond similarly to the low-light conditions in one of 

these experiments. 

Purpose and Scope

The purpose of this report is to provide data for SAFAs, 

MUFAs, and PUFAs detected in periphyton at 20 sites 

sampled in August 2009 and at 6 sites sampled in November 

2009. Diatom identifications and two measures of periphyton 

standing crop are also reported along with limited data 

for five water-quality parameters. Results are presented 

from univariate and multivariate statistical tests assessing 

spatial and temporal differences in periphyton communities. 

Limitations of the study and recommendations for future work 

are also presented.

Methods

Study Scope and Area

The upper Esopus Creek is in the Catskill Mountain 

region of southeastern New York and follows a 41.8-

km semicircular clockwise course from its headwaters at 

Winnisook Lake to its impoundment downstream from 

Boiceville, where it forms the Ashokan Reservoir (fig 1). The 

watershed of the upper Esopus Creek drains 497.3 square 

kilometers, much of which is rugged and mountainous 

terrain (Cornell Cooperative Extension of Ulster County 

and others, 2007). Nine major tributaries deliver waters 

to the upper Esopus Creek in addition to the Shandaken 

portal, which enters the upper Esopus Creek approximately 

20 km upstream from the Ashokan Reservoir. The portal’s 

contribution to the overall sediment load in the upper Esopus 

Creek is considered minimal (Cornell Cooperative Extension 

of Ulster County and others, 2007) because the portal is not 

operated during storm events, during which time tributaries 

supply high sediment loads (McHale and Siemion, 2014). 

Under base flows, however, waters from the portal are often 

more turbid than the receiving waters of the upper Esopus 

Creek. For example, the median turbidity value observed at 

the portal from 1987 to 2005 of 8.8 nephelometric turbidity 

units (NTU) was the highest in the basin (Cornell Cooperative 

Extension of Ulster County and others, 2007).

Periphyton samples were collected at 20 sites in the 

watershed (fig. 1; table 1) in August 2009. Ten sites were on 

the main stem of the upper Esopus Creek, with four upstream 

and six downstream from the portal. Ten other sites were on 

nine major tributaries to the upper Esopus Creek (two were 

on Stony Clove Creek [fig. 1]). To provide information on 

seasonal changes, six main stem sites—three upstream and 

three downstream from the portal—were sampled again in 

November 2009. Throughout this report, the six sites sampled 

during both periods are referred to as seasonal sites, the main 

stem sites upstream from the portal are referred to as upstream 

sites, and the main stem sites downstream from the portal are 

referred to as downstream sites.

Periphyton Sampling

Collection of periphyton samples was similar to that 

described in the U.S. Environmental Protection Agency 

periphyton protocols for sampling single habitats (Stevenson 

and Bahls, 1999). Periphyton samples were collected 

exclusively from riffles using rocks with flat surfaces that were 

classified as large cobble or boulder using the Wentworth scale 

(Cummins, 1962). A single, pooled qualitative periphyton 

sample that was representative of the entire stream channel 

was collected at each site for fatty acid analysis. Periphyton 

was scraped from sets of three rocks that were collected 

from the left, right, and center thirds of the streambed for 

a total of nine rocks per pooled sample. Each sample was 

stored in an 0.53 L Nasco Whirl-Pak bag and kept in the 

dark on ice until the sample could be frozen and stored at 

-80 degrees Celsius (°C).

At the same time and sites where fatty acid samples 

were collected for qualitative analysis, quantitative 

periphyton samples were collected to determine standing crop 

(chl a and AFDM) and to identify attached diatoms. Three 

replicate samples (replicates) were collected at each site by 

combining the scrapings from a delineated area of the surface 

of three rocks from one stream third (left, right, and center). A 

fourth replicate was collected for diatom identification during 

the August 2009 survey at each site using one rock from each 

stream third. The volume of slurry from each replicate was 

measured, and subsamples were taken for determination of 

chl a and AFDM and for diatom identification. For chl a and 

AFDM, the sample was mixed thoroughly with an electric 

mixer, and a 5-milliliter (mL) subsample was vacuumed 

through an Advantec Grade GF-75 glass fiber filter. Each filter 

was placed in a petri dish, covered with aluminum foil, and 

kept on ice until the filter could be frozen in the laboratory. 

For diatom identification, the sample was mixed using an 

electric mixer and a 20-mL subsample was pipetted into a 

glass vial and preserved with formalin. The scraped area of 

each rock was outlined in chalk and photographed with a 

wire screen overlain of known mesh size. Area was calculated 

from these photographs using Analyzing Digital Images 

software (Pickle, 2008).
Methods 5

Table 1. Stream name, site identification number, drainage area, and location of 20 sampling sites along the main stem and tributaries 

of the upper Esopus Creek, New York.

[Sites identified as U–[X] are upstream of the entrance of the Shandaken portal, which diverts waters from the Schoharie Reservoir to the upper Esopus Creek; 

sites identified as D–[X] are downstream of the portal; sites identified as T–[X] are on tributaries to the Esopus Creek. * indicates sites that were sampled in 

both August and November 2009. Latitude and longitude are in decimal degrees and are from the North American Datum of 1983. ID, identification number; 

km2, square kilometer]

Stream name Site ID Drainage area

(km2

) Town/village Latitude Longitude

Upper Esopus Creek U–0 30.3 Oliverea 42.0656 -74.4606

Upper Esopus Creek U–2* 111.9 Big Indian 42.1042 -74.4367

Upper Esopus Creek U–3* 152.0 Shandaken 42.1194 -74.3975

Upper Esopus Creek U–3a* 165.0 Allaben 42.1143 -74.3666

Upper Esopus Creek D–3b* 181.0 Allaben 42.1134 -74.3619

Upper Esopus Creek D–4 215.7 Upstream of Phoenicia 42.0922 -74.3364

Upper Esopus Creek D–4a* 357.4 Phoenicia 42.0819 -74.3119

Upper Esopus Creek D–4b 365.2 Phoenicia 42.0636 -74.3064

Upper Esopus Creek D–5 373.0 Mount Pleasant 42.0467 -74.2803

Upper Esopus Creek D–6* 497.3 Boiceville 42.0039 -74.2683

Beaver Kill T–0 64.7 Mount Tremper 42.0474 -74.2762

Birch Creek T–1 32.4 Big Indian 42.1076 -74.4504

Broadstreet Hollow T–2 23.7 Allaben 42.1126 -74.3585

Bushnellsville Creek T–3 29.5 Shandaken 42.1209 -74.3989

Fox Hollow T–4 10.3 Allaben 42.1161 -74.3806

Little Beaver Kill T–5 42.7 Beechford 42.0195 -74.2697

Peck Hollow T–6 12.3 Allaben 42.1180 -74.3783

Stony Clove Creek T–7 80.0 Chichester 42.1020 -74.3109

Stony Clove Creek T–8 83.9 Phoenicia 42.0831 -74.3148

Woodland Creek T–9 53.4 Phoenicia 42.0813 -74.3317

Fatty Acid Analysis

The FAME analysis is a three step process: gravimetric 

extraction, derivatization, and quantification on a gas 

chromatograph. A subsample of freeze-dried periphyton was 

extracted three times by grinding freeze-dried materials with 

a Teflon mortar in a glass tube to which a 2:1 chloroformto-methanol solution was added (Folch and others, 1957). 

After centrifugation at 600 times gravity centrifugal force 

to remove most nonlipid material, the supernatant was 

transferred to acid-washed 15-mL centrifuge tubes and rinsed 

with the chloroform-to-methanol solution. This procedure 

was followed by a salt wash (0.9 percent aqueous sodium 

chloride solution) to remove lipophilic proteins before the 

samples were evaporated to 2 mL using a stream of nitrogen 

gas. From this volume, duplicate 0.2-mL aliquots (10 percent 

of the sample extract) were weighed on an electronic 

microbalance (0.001 milligrams) to provide a gravimetric 

measurement of total lipid concentration (lipid mass per 

dry-weight tissue extracted). The remaining 1.6 mL of each 

extract was evaporated to dryness with nitrogen gas, tightly 

capped, and stored at -80 °C for later gas chromatography 

analyses of FAME. A synthetic lipid (cholestane), detectable 

by gas chromatography analysis along with FAME, was 

added to all samples as an internal standard to determine 

extraction efficiency (Sigurgisladottir and others, 1992). 

Immediately prior to derivitization, samples were removed 

from the -80 °C freezer and warmed to room temperature 

in the dark. Hexane (2 mL) was added to redissolve the 

extract. Derivitization of FAME was based on the sulfuric 

acid methanol method of Schlechtriem and others (2008). 

Gas chromatograph separation and quantification of fatty 

acids employed an Agilent 6890N gas chromatograph fitted 

with a Supelco SP–2560 (Bellefonte, PA) 100-meter × 

0.25-millimeter-internal diameter × 0.20-micrometer-thick 

film. The oven temperature of the gas chromatograph was set 

at 100 °C for 1 minute before increasing by 5 °C per minute 

to 240 °C, which was held for 31 minutes; helium carrier 

gas flow rate was set at 20 centimeters per second; peak 

detection was by flame ionization with detector temperature 
6 Response of Periphyton Fatty Acid Composition to Supplemental Flows in the Upper Esopus Creek, New York

set at 260 °C; injector temperature was set at 260 °C; and 

total run time was 60 minutes per sample. Docosapentaenoic 

acid (Supleco #47563–U) was added to the 37-component 

FAME standard (Supelco #47885–U). The identity of eluted 

peaks in samples was determined by comparing sample peak 

retention times with retention time of the FAME standards. A 

four-point standard calibration curve was used to quantify the 

concentration of each fatty acid peak identified.

The area under each fatty acid peak was calculated as 

a percentage of the total area of all fatty acid peaks in the 

chromatogram and quantitatively as micrograms of fatty acid 

per milligram of periphyton. Both measurements gave similar 

results (coefficient of determination [r2] = 0.95); therefore, 

only the percentage data are presented in this report. Fatty 

acids are reported in the shorthand form x:aωb, where x is the 

number of carbons in the acyl chain, a is the total number of 

double bonds, and b is the position of the first double bond 

from the methyl end of the molecule (Allan and others, 2010); 

the suffix c or t indicates the cis or trans isomer, respectively, 

where applicable. In addition to calculating the relative 

abundance of each fatty acid, the following summary metrics 

were also calculated: sum of SAFAs, sum of MUFAs, and 

sum of PUFAs.

Standing Crop and Diatom Analysis

Total chl a was determined using standard methodology 

for fluorometric determination of chl a with a pheophytin a

correction (Rice and others, 2012). The hold time for chl a

samples was 470 days for samples from August 2009 and 

398 days for samples from November 2009, which exceeded 

the advised hold time. Therefore, the utility of the chl a data 

is only to identify relative differences within the study area. 

Filters for AFDM were oven dried at 100 °C for 24 hours, 

weighed, ashed at 500 °C for 2 hours, and reweighed to 

determine AFDM (Steinman and others, 1996), which was 

calculated as the difference between the dried weight and the 

ashed weight of each replicate. 

Periphyton samples for identification of diatoms 

were shipped to the Rhithron Associates, Inc. laboratory 

in Missoula, Montana and identified to the lowest possible 

taxonomic resolution (generally to species). Diatoms were 

identified because of their role in the biological assessment 

of surface waters in New York State. The New York State 

Department of Environmental Conservation has developed 

several diatom-based community metrics to assess waterquality conditions (Passy and Bode, 2004; New York State 

Department of Environmental Conservation, 2012). Therefore, 

it was important to derive a connection between the fatty 

acid content of the periphyton community and the diatom 

assemblages used in the assessment of surface waters in New 

York State. Permanent diatom slides were prepared from acidwashed subsamples from each replicate at each site. A transect 

was scribed on each slide, and the first 600 valves along the 

transect line were identified.

Water Quality

Average daily stream discharge for each seasonal site was 

obtained from existing U.S. Geological Survey streamgages 

or, in the absence of streamgages, estimated by a drainagearea adjustment of nearby observed discharges. Additionally, 

a limited number of suspended sediment, turbidity, and water 

chemistry samples were collected at the seasonal sites for an 

independent project beginning in August 2009. Water samples 

were collected on three occasions: August 26–27, September 

23, and November 3 (the date of fatty acid sampling), 

meaning that three samples were collected at each site during 

a 2 to 3 month period immediately before the collection 

of the November fatty acid samples. Because insufficient 

water-quality data were available before the August fatty 

acid sampling, relations between water-quality parameters 

and fatty acids were only evaluated for the November 

samples, and only the fatty acids that were detected from 

at least three of these sites were included. Pearson productmoment correlations (r) were used to identify significant 

relations between mean water-quality parameters from each 

site and the relative abundance of individual fatty acids and 

summary metrics.

Statistical Analysis

The hypothesis that the fatty acid content and 

standing crop of periphyton differed by location (upstream, 

downstream, and tributary) was evaluated using one-way 

analysis of variance (ANOVA) with Tukey’s test of multiple 

comparisons. The fatty acid dataset was tested using 

percentages of individual fatty acids and summary metrics 

from the pooled samples, whereas standing crop was tested 

using the mean values of chl a and AFDM from the three 

replicates collected at each site. Samples from each period 

were tested separately, which enabled the use of the tributary 

data in the August dataset. A one-way ANOVA was also 

used to identify differences in the fatty acid and standing 

crop datasets between the August (excluding tributaries) and 

November samples. All subsequent analyses between seasons 

also exclude tributaries; thus, 10 sites are considered in August 

and 6 sites are considered in November.

Fatty acid composition was also evaluated using 

nonmetric multidimensional scaling (MDS) ordinations 

(Shepard, 1962; Kruskal, 1964) with Primer-E version 

6 software (Clarke and Gorley, 2006). The raw data (as 

proportions) were arcsine-square-root-transformed, and BrayCurtis similarities were used to form a resemblance matrix 

comparing all samples (Clarke and Warwick, 2001). Analysis 

of similarity (ANOSIM) was applied to the resemblance 

matrix to test the null hypothesis of no difference between the 

fatty acid composition of sites grouped by location (upstream, 

downstream, and tributary) or season (August or November). 

Although the ANOSIM test produces a P value, the R-test 

statistic is considered more informative and is interpreted as 
Results 7

follows: R > 0.5 indicates separate but overlapping groups 

and 0.75 < R < 1 indicates strong separation between groups 

(Clarke and Warwick, 2001; Ramette, 2007). Two ANOSIM 

tests were performed: a two-way crossed analysis of a 

combined dataset (upstream and downstream for August 

and November) that excluded tributaries and a one-way 

analysis of the August dataset (upstream, downstream, and 

tributary) alone.

The condition of the diatom community (as an indicator 

of water quality) was assessed using an index of biological 

integrity, the diatom assessment profile (DAP; New York 

State Department of Environmental Conservation, 2012). A 

DAP score was produced for each sample at each site, and a 

one-way ANOVA with Tukey’s test of multiple comparisons 

was used to test for differences in mean DAP score between 

locations and seasons. Diatom community structure was 

also assessed using MDS ordinations in order to identify 

sites (or groups of sites) with distinctive relative abundances 

of species. Identification results (species counts) for all 

replicates from each site were combined to obtain the most 

representative sample. The data were square-root-transformed 

to reduce the influence of highly abundant taxa, Bray-Curtis 

similarities were used to plot the MDS ordination (Clarke 

and Warwick, 2001), and ANOSIM tests were performed, 

as described above, to determine if assemblages differed by 

location or season.

Results

Fatty Acids

Percentages of individual fatty acids and summary 

metrics at each site are presented in appendix 1. The fatty 

acids 21:0, 14:1ω5, and 17:1 as well as the trans isomers 

18:1ω9t and 18:2ω6t were not detected in any sample and 

therefore are not included in any tables or analyses. When 

all sites and both seasons were considered, the fatty acid 

indicators of diatom dominance (16:0, 16:1ω7, and 20:5ω3) 

accounted for an average of 60.3 percent (range of 35.5 to 

77.9 percent) of the fatty acids present, and the three major 

classes of fatty acids occurred in similar mean abundances: 

SAFA, 37.9 percent; MUFA, 32.4 percent; and PUFA, 

29.7 percent.

When samples from August 2009 were considered alone, 

summary metrics did not differ significantly by location; 

however, the percentages of some individual fatty acids did 

differ significantly by location. Percentages of the PUFAs 

18:3ω6 and 20:5ω3 differed significantly (P < 0.001 and 

P = 0.019, respectively), and each was more abundant at 

upstream sites than at downstream sites (table 2). The PUFA 

22:5ω3 also differed significantly by location (P = 0.013), 

with greater abundance at tributary sites than at downstream 

sites. Differences in the relative abundance of 22:6ω3 also 

approached significance (0.05 < P < 0.1) with no presence 

at downstream (0.00 percent) sites and low abundance at 

upstream (0.28 percent) and tributary (0.21 percent) sites. 

The only SAFA to differ significantly by location was 14:0 

(P = 0.025), which was more abundant at tributary sites than 

at upstream sites. No MUFA varied significantly by location, 

although differences in 22:1ω9 and 24:1ω9 each approached 

significance (0.05 < P < 0.1). When samples from November 

2009 were considered alone, neither summary metrics nor 

any individual fatty acids differed significantly by location 

(table 2). The relative abundance of fatty acids changed little 

between sampling seasons; thus, tabular results of those 

comparisons are not presented. None of the summary metrics 

differed significantly between seasons, and only one individual 

fatty acid, 22:5ω3, differed significantly (P = 0.033) between 

samples from August (mean 0.14 percent) and November 

(mean 0.59 percent). Additionally, the PUFA 22:6ω3 was only 

detected at 2 out of 10 main stem sites in August, whereas 

it was present at 5 out of 6 main stem sites in November; 

however, these differences were not significant.

Results from the multivariate analyses indicate that the 

portal may have had an effect on the fatty acid composition 

of periphyton. When samples from August were analyzed 

alone, sites clustered weakly by location (fig. 2). A one-way 

ANOSIM test indicated that upstream sites were significantly 

different from downstream (R = 0.492, P = 0.010) and 

tributary (R = 0.451, P = 0.020) sites while tributary and 

downstream sites were not significantly different (R = 0.086, 

P = 0.208). When both periods (excluding tributaries) were 

analyzed together, the samples again clustered weakly by 

location (fig. 3), and the two-way ANOSIM test indicated 

that fatty acid composition of upstream and downstream 

sites was significantly different (R = 0.372, P = 0.008). Sites 

downstream from the portal clustered more tightly while a 

few upstream sites exhibited distinctive fatty acid signatures. 

The two-way ANOSIM test also indicated that samples from 

August and November did not differ significantly (R = 0.156, 

P = 0.168), although samples from November, with the 

exception of site U–2, appeared to group more closely in the 

ordination (fig. 3).

Water Quality and Fatty Acid Relations

Water-quality parameters from samples at individual sites 

did not exhibit much variability during the collection period 

(August 26 to November 3, 2009; appendix 2). As expected, 

however, waters downstream from the portal were generally 

more turbid and contained higher concentrations of suspended 

sediment than upstream sites during stable flows. Mean values 

of turbidity ranged from 1.3 NTU at site U–3a to 5.0 NTU at 

site D–3b, the sampling site immediately downstream from 

the portal, and mean turbidity at downstream sites (4.0 NTU) 

was significantly greater (P = 0.012) than that of upstream 

sites (1.5 NTU; table 3). Mean values of suspended sediment 

ranged from 0.7 milligrams per liter (mg/L) at site U–3a to 
8 Response of Periphyton Fatty Acid Composition to Supplemental Flows in the Upper Esopus Creek, New York

Table 2. Summary of one-way analysis of variance results comparing the relative abundance of individual fatty acids and summary 

metrics for periphyton from sites along the main stem and tributaries of the upper Esopus Creek, New York.

[Samples are from upstream, downstream, and tributary sites during the August 2009 survey and upstream and downstream sites during the November 2009 

survey. Significant P values are shown in bold; the significant groupings are denoted by letters (groups that do not share a letter are significantly different). 

n, number of samples; SD, standard deviation; <, less than]

Fatty 

acid

August November

Upstream sites

(n = 4)

Downstream sites

(n = 6)

Tributary sites

(n = 10)

Upstream sites

(n = 3)

Downstream sites

(n = 3)

Mean SD Mean SD Mean SD P value Mean SD Mean SD P value

Saturated fatty acids

12:0 0.18 0.37 0.00 0.00 0.00 0.00 0.134 0.00 0.00 0.00 0.00 1.000

14:0 5.88 a 1.23 6.55 ab 1.10 7.96 b 1.39 0.025 7.00 1.79 7.23 1.52 0.875

15:0 0.07 0.14 0.00 0.00 0.03 0.09 0.477 0.24 0.23 0.00 0.00 0.150

16:0 23.13 1.99 27.04 2.22 26.73 3.05 0.069 23.88 3.73 23.24 1.91 0.805

17:0 0.42 0.38 0.35 0.18 0.31 0.29 0.832 0.58 0.08 0.63 0.27 0.745

18:0 5.24 3.35 3.64 0.48 3.55 0.83 0.190 7.91 5.63 4.28 0.95 0.333

20:0 0.11 0.23 0.19 0.15 0.36 0.17 0.059 0.37 0.40 0.00 0.00 0.184

22:0 0.05 0.10 0.09 0.10 0.07 0.10 0.783 0.21 0.23 0.07 0.13 0.425

23:0 0.09 0.18 0.00 0.00 0.00 0.00 0.134 0.05 0.09 0.00 0.00 0.374

24:0 0.08 0.16 0.00 0.00 0.00 0.00 0.134 0.00 0.00 0.00 0.00 1.000

Total 35.25 1.94 37.87 3.49 39.01 3.95 0.228 40.23 2.91 35.47 3.43 0.140

Monounsaturated fatty acids

15:1 0.10 0.20 0.05 0.13 0.05 0.15 0.855 0.00 0.00 0.21 0.37 0.374

16:1ω7 23.61 12.06 27.71 6.85 26.85 7.25 0.728 17.36 5.94 27.79 8.96 0.168

18:1ω9c 5.50 1.88 5.15 0.61 5.08 0.97 0.809 8.41 5.19 5.71 1.37 0.434

20:1ω9 0.19 0.13 0.23 0.16 0.27 0.29 0.844 3.16 5.06 0.09 0.16 0.353

22:1ω9 0.54 0.28 0.34 0.05 0.37 0.09 0.080 0.26 0.23 0.49 0.30 0.351

24:1ω9 0.05 0.10 0.18 0.14 0.33 0.23 0.056 0.16 0.14 0.27 0.24 0.526

Total 29.98 12.16 33.66 6.86 32.95 6.93 0.766 29.35 5.17 34.57 8.00 0.396

Polyunsaturated fatty acids

18:2ω6c 4.75 2.02 5.74 1.26 5.34 1.77 0.666 5.48 1.63 4.21 0.82 0.294

18:3ω3 13.48 7.85 13.23 6.62 9.73 4.45 0.406 10.50 6.90 9.54 4.82 0.853

18:3ω6 1.07 a 0.26 0.61 b 0.05 0.89 a 0.15 <0.001 0.77 0.40 0.72 0.10 0.845

20:2ω6 1.49 1.14 0.99 0.17 1.34 0.31 0.318 1.46 0.75 1.65 0.29 0.707

20:3ω3 0.12 0.14 0.55 0.09 0.04 0.09 0.448 0.14 0.13 0.07 0.12 0.508

20:3ω6 0.05 0.09 0.05 0.12 0.01 0.03 0.575 0.00 0.00 0.00 0.00 1.000

20:4ω6 0.80 0.64 0.61 0.22 0.81 0.24 0.512 0.68 0.38 0.53 0.34 0.622

20:5ω3 12.20 a 3.74 6.78 b 1.52 8.94 ab 2.70 0.019 8.41 5.02 12.23 6.00 0.445

22:2ω6 0.29 0.24 0.35 0.02 0.42 0.11 0.222 0.22 0.20 0.42 0.03 0.161

22:5ω3 0.25 ab 0.18 0.07 a 0.10 0.32 b 0.16 0.013 0.79 0.81 0.38 0.18 0.440

22:6ω3 0.28 0.32 0.00 0.00 0.21 0.19 0.072 1.97 2.71 0.22 0.20 0.327

Total 34.77 10.96 28.48 6.31 28.04 5.99 0.290 30.42 7.92 29.96 5.10 0.937
Results 9

U–0

U–2

U–3

U–3a

D–3b

D–4

D–4a

D–4b

D–5

D–6

T–0

T–1

T–2

T–3

T–4

T–5

T–6

T–7

T–8

T–9

2D Stress: 0.11

One-way ANOSIM test

 Global: R = 0.282, P = 0.017

 U vs. T: R = 0.451, P = 0.020

U vs. D: R = 0.492, P = 0.010

 D vs. T: R = 0.086, P = 0.208

Tributary sampling site

Upstream sampling site

Downstream sampling site

EXPLANATION

Figure 2. Nonmetric multidimensional scaling ordination based on arcsine-square-root-transformed proportion data of periphyton fatty 

acid content collected during August 2009 from sites upstream or downstream from the Shandaken portal, or on a tributary of the upper 

Esopus Creek, New York. Site locations and identification numbers are identified in table 1. Results of the one-way analysis of similarity 

(ANOSIM) test show the significance of the three levels of the location factor. Two-dimensional (2D) stress is a measurement of the 

goodness of fit of the arrangement of points in the ordination. U, upstream; T, tributary; D, downstream; vs., versus.

4.0 mg/L at site D–3b, and differences in mean suspended 

sediment at upstream sites (0.9 mg/L) and downstream 

sites (2.8 mg/L) approached significance (0.05 < P < 0.1). 

Each parameter peaked immediately downstream from the 

portal and decreased moving downstream. Mean specific 

conductance, pH, and stream discharge were also significantly 

higher (P < 0.05) at downstream sites, whereas differences in 

nitrate were not significant.

Relations between mean water-quality parameters and 

individual fatty acids or summary metrics were generally 

weak. None of the individual fatty acids or summary metrics 

were significantly correlated with turbidity or suspended 

sediment. The correlations between suspended sediment and 

22:1ω9 (r = 0.75, P = 0.087) and 20:5ω3 (r = 0.72, P = 0.108) 

were the closest to reaching significance, but most correlations 

between fatty acids and suspended sediment or turbidity 

did not exceed r = 0.5. Nitrate was significantly correlated 

with 17:0 (r = 0.91, P = 0.012), pH was significantly 

correlated with 22:2ω6 (r = 0.83, P = 0.041), and there were 

no significant correlations with specific conductance or 

stream discharge.

Although turbidity, specific conductance, and pH were 

all significantly greater at downstream sites than at upstream 

sites, water-quality parameters generally exhibited low 

variability during the study and did not reach levels that would 

be expected to cause impairment to the periphyton community. 

For example, the highest mean turbidity value recorded 

was only 5.0 NTU (at site D–3b) which was well below 

most thresholds for impairment of lotic biota (Lloyd, 1987; 

Ryan, 1991). As a result, water-quality parameters generally 

did not explain much variation in the fatty acid dataset from 

November and there were no significant correlations between 

fatty acids and turbidity or suspended sediment. Additionally, 

the significant correlations identified with nitrate and pH may 

not be biologically meaningful because of the low variation 

in these parameters. It is noteworthy that mean daily stream 
10 Response of Periphyton Fatty Acid Composition to Supplemental Flows in the Upper Esopus Creek, New York

U–0

U–2

U–3

U–3a

D–3b

D–4

D–4a

D–4b

D–5 D–6 U–2n

U–3n

U–3an

D–3bn

D–4an

D–6n

2D Stress: 0.08

Two-way ANOSIM test

U vs. D: R = 0.372, P = 0.008

 August vs. November: R = 0.156, P = 0.168

Upstream sampling site

Downstream sampling site

EXPLANATION

Figure 3. Nonmetric multidimensional scaling ordination based on arcsine-square-root-transformed proportion data of periphyton 

fatty acid content collected during August and November 2009 from sites on the upper Esopus Creek upstream or downstream from the 

Shandaken portal, New York. Site identification numbers ending with n denote samples from November. Site locations and identification 

numbers are identified in table 1. Results of the two-way analysis of similarity (ANOSIM) test show the significance of the two factors 

(location [upstream or downstream] and season [August or November 2009]). Two-dimensional (2D) stress is a measurement of the 

goodness of fit of the arrangement of points in the ordination. U, upstream; D, downstream; vs., versus.

discharge across the 70-day period before the November 

survey increased from 2.2 cubic meters per second at site 

U–3a to 8.9 cubic meters per second at site D–3b, an increase 

of approximately 300 percent in less than 1 km (primarily 

because of inputs from the portal). In contrast, mean discharge 

at site D–6 (approximately 17 km downstream from the portal) 

during the same period was only 63 percent greater than at 

site D–3b. This observed increase in discharge between sites 

U–3a and D–3b is consistent with results from a recent study 

indicating that under low and moderate flows, the portal 

generally increased natural flows on the upper Esopus Creek 

by more than 100 percent (Burns and Gazoorian, 2015). 

These results indicate that supplemental flows from the portal 

contribute substantially to the discharge at all downstream 

sites and that any differences in periphyton between upstream 

and downstream sites cannot simply be attributed to normal 

longitudinal changes.

Standing Crop

The chl a and AFDM data were significantly correlated 

(r = 0.91; P < 0.001) and are presented in table 3 as the results 

of the one-way ANOVA and in appendix 3 as the means of 

all three samples (left, right, and center of stream). The chl a 

data differed significantly by location when August samples 

were analyzed alone (P = 0.019). Mean chl a at tributary 

sites (5.38 micrograms per square centimeter [μg/cm2]) 

differed (P < 0.05) from that of upstream (2.57 μg/cm2

) and 

downstream (2.93 μg/cm2) sites (table 3). Although samples 

from upstream and downstream sites were not significantly 

different (P > 0.05), chl a dropped sharply from 

4.53 μg/cm2

 at site U–3a (immediately upstream from the 

portal) to 1.97 μg/cm2 at site D–3b (immediately downstream 

from the portal) and remained low at sites D–4 and D–4a. In 

November, chl a data from upstream and downstream sites 
Results 11

Table 3. Summary of one-way analysis of variance results comparing periphyton standing crop, diatom community integrity, and water-quality parameters from sites along the main stem and tributaries of the upper Esopus Creek, New York.[Samples are from upstream, downstream, and tributary sites during the August and November 2009 surveys and for water-quality parameters and daily stream discharge at upstream and downstream sites during the 70 days before the November 2009 survey. Significant P values are shown in bold; the significant groupings are denoted by letters (groups that do not share a letter are significantly different). n, number of samples; SD, standard deviation; --, not available]

August November

Upstream sites

(n = 4)

Downstream sites

(n = 6)

Tributary sites

(n = 10)

Upstream sites

(n = 3)

Downstream sites

(n = 3)

Mean SD Mean SD Mean SD P value Mean SD Mean SD P value

Chlorophyll a, in micrograms per square 

centimeter

2.57 b 1.52 2.93 b 1.17 5.38 a 2.18 0.019 12.26 0.92 12.84 7.24 0.897

Ash-free dry mass, in milligrams per square 

centimeter

1.00 0.58 1.06 0.55 1.03 0.28 0.979 2.62 0.31 3.75 2.12 0.412

Diatom assessment profile score 7.19 0.16 7.02 0.27 6.95 0.36 0.450 6.35 0.13 6.43 0.37 0.735Nitrate, in micromoles per liter -- -- -- -- -- -- -- 7.4 0.6 7.1 1.3 0.785pH -- -- -- -- -- -- -- 7.05 0.05 7.19 0.03 0.021Specific conductance, in microsiemens per 

centimeter at 25 degrees Celsius

-- -- -- -- -- -- -- 50.3 2.5 60.1 2.7 0.010

Stream discharge, in cubic feet per second -- -- -- -- -- -- -- 68.7 13.3 420.4 99.5 0.004Total suspended sediment, in milligrams per liter -- -- -- -- -- -- -- 0.9 0.2 2.8 1.2 0.051Turbidity, in nephelometric turbidity units -- -- -- -- -- -- -- 1.5 0.2 4.0 1.0 0.012
12 Response of Periphyton Fatty Acid Composition to Supplemental Flows in the Upper Esopus Creek, New York

(mean values of 12.26 and 12.84 μg/cm2, respectively) were 

also not significantly different (P = 0.897; table 3), but a spike 

from 13.10 to 20.77 μg/cm2 was observed between sites U–3a 

and D–3b. The chl a data did differ significantly (P < 0.001) 

between seasons (excluding tributaries) irrespective of 

location: mean chl a in August was 2.79 μg/cm2

 compared to 

12.55 μg/cm2 in November.

The AFDM data had a similar pattern to that of the chl a

data but did not differ significantly by location during August 

(P = 0.979). Mean AFDM in August was 1.00 milligrams per 

square centimeter (mg/cm2) at upstream sites, 1.06 mg/cm2

at downstream sites, and 1.03 mg/cm2 at tributary sites 

(table 3). Similar to chl a, AFDM decreased by more than 

50 percent between sites U–3a and D–3b and remained low 

until site D–5. During November, mean AFDM was not 

significantly different (P = 0.412) at upstream (2.62 mg/cm2

) 

and downstream (3.75 mg/cm2; table 3) sites but did increase 

sharply from 2.95 to 5.98 mg/cm2 between sites U–3a and 

D–3b. The AFDM data did differ significantly (P = 0.001) 

between seasons as mean AFDM was 1.03 mg/cm2 in August 

compared with 3.19 mg/cm2 in November.

Diatoms

Diatom identifications were used to produce a DAP score 

at each site. When August sites were considered alone, DAP 

scores at the three locations were not significantly different 

(P = 0.450). The mean DAP score was 7.19 at upstream sites, 

7.02 at downstream sites, and 6.95 at tributary sites (table 3). 

Unlike measurements of standing crop, the DAP score did 

not drop sharply between sites U–3a and D–3b. In November, 

the mean DAP score was 6.35 at upstream sites and 6.43 

at downstream sites and also did not differ significantly 

(P = 0.735). However, the DAP score did differ significantly 

between seasons (P < 0.001) as sites sampled in August had a 

mean DAP score of 7.09 compared with 6.39 in November.

Results of the diatom identifications were also expressed 

as MDS ordinations. When sites sampled in August were 

analyzed alone (fig. 4), downstream sites grouped tightly and 

were significantly different from upstream sites (R = 0.567, 

P = 0.005) and tributary sites (R = 0.331, P = 0.009) whereas 

upstream and tributary sites were not significantly different 

(R = -0.039, P = 0.538). Community structure was most 

variable at tributary sites. When main stem sites from both 

periods were analyzed together (fig. 5), the samples clustered 

significantly by location (R = 0.595, P = 0.001) and by season 

(R = 0.989, P = 0.001). Species assemblages from all sites 

sampled in August and November were at least 60 percent 

similar to each other (fig. 5); however, no single pair of 

November and August assemblages reached this degree 

of similarity.

Response of Periphyton Fatty Acid 

Composition to Supplemental Flows

The primary purpose of the study presented in this 

report was to gain a more comprehensive understanding of 

how waters diverted from the Schoharie Reservoir through 

the Shandaken Tunnel affect periphyton in the upper Esopus 

Creek. Measurements of periphyton standing crop and fatty 

acid composition, diatom community structure and integrity, 

and basic water-quality parameters were characterized 

upstream and downstream from the portal during two seasons 

and at tributary sites during one season. This combination of 

spatial and seasonal measurements helped to determine the 

effect of supplemental flows from the portal on the fatty acid 

composition of periphyton, assess the utility of fatty acid 

analysis as a tool for evaluating ecosystem condition, and 

explore spatial and temporal differences in the periphyton 

community.

Spatial Patterns

The effects of waters from the portal on periphyton 

communities were not as pronounced as anticipated. Overall, 

measurements of standing crop and multivariate analysis of 

diatom assemblages provided little evidence that the inflow of 

portal waters affected periphyton. A comparison of standing 

crop measurements at the sites immediately upstream (U–3a) 

and downstream (D–3b) of the portal indicates that the portal 

may have locally affected standing crop differently during 

each season. The chl a and AFDM values decreased sharply 

between sites U–3a and D–3b in August but each increased 

sharply between sites U–3a and D–3b in November. However, 

these effects were observed primarily at the sites nearest to 

the portal, and mean AFDM, chl a, and DAP score did not 

vary significantly upstream and downstream from the portal 

during either season. In contrast, multivariate analysis of the 

diatom identifications lent stronger support to a portal-driven 

influence. Analyses of the August and combined datasets each 

indicated that diatom community structure at upstream sites 

was significantly different from that of downstream sites.

The minor effect of the portal on periphyton communities 

and water-quality parameters during the study period 

provided a poor opportunity to test the hypothesis that 

fatty acid analysis of periphyton is sensitive to differences 

in water quality or ecosystem condition. A few analyses, 

however, did detect changes in the fatty acid composition 

of periphyton downstream from the portal during August. 

Multivariate analysis indicated that fatty acid composition 

differed significantly between upstream and downstream sites. 

It is also noteworthy that the sum of PUFAs decreased from 

42.4 percent at site U–3a to 27.4 percent at site D–3b, and 

some individual PUFAs were more abundant upstream from 

the portal than downstream. Within the omega-6 family of 

fatty acids, 18:3ω6 was significantly more abundant upstream 
Response of Periphyton Fatty Acid Composition to Supplemental Flows 13

Tributary sampling site

Upstream sampling site

Downstream sampling site

T–2

T–0

T–1

T–3

T–4

T–5

T–6

T–7

T–8

U–0

U–2

U–3a

U–3

D–3b

D–4a

D–4

D–4b

D–5

D–6

T–9

2D Stress: 0.14 One-way ANOSIM test

 Global: R = 0.228, P = 0.019

 U vs. T: R = -0.039, P = 0.538

U vs. D: R = 0.567, P = 0.005

 D vs. T: R = 0.331, P = 0.009

EXPLANATION

Figure 4. Nonmetric multidimensional scaling ordination based on square-root-transformed species abundance data of diatom 

assemblages collected during August 2009 from sites upstream or downstream from the Shandaken portal, or on a tributary of the upper 

Esopus Creek, New York. Site locations and identification numbers are identified in table 1. Results of the one-way analysis of similarity 

(ANOSIM) test show the significance of the three levels of the location factor. Two-dimensional (2D) stress is a measurement of the 

goodness of fit of the arrangement of points in the ordination. U, upstream; T, tributary; D, downstream; vs., versus.

from the portal than downstream, and the physiologically 

important 20:4ω6 (arachidonic acid), which is the elongation 

product of 18:3ω6, was also more abundant (although not 

significantly) upstream from the portal. Within the omega-3 

family, 20:5ω3, 22:5ω3, and 22:6ω3 were detected in 

greater relative abundances upstream from the portal than 

downstream, although not all differences were significant. 

Brett and Müller-Navarra (1997) determined that the 

nutritional quality of periphyton can be evaluated by the 

abundance of particular PUFAs and specifically, that the 

availability of 20:5ω3 and 22:6ω3 in primary producers is 

critical to the growth and condition of associated consumers. 

Therefore, these findings suggest the nutritional quality of 

periphyton may be higher upstream from the portal than 

downstream, and in turn may explain why the New York State 

Department of Environmental Conservation determined that 

diatom and macroinvertebrate assemblages upstream from the 

portal were healthier than those downstream from the portal in 

some years (Bode and others, 2001; Smith, 2013).

Seasonal Differences

Although spatial variation in the periphyton community 

was less than expected, significant seasonal changes 

were observed in the periphyton community between the 

August and November samples. Mean chl a increased 

from 2.79 μg/cm2 in August to 12.55 μg/cm2 in November, 

and mean AFDM increased from 1.03 mg/cm2 in August 

to 3.19 mg/cm2 in November. These significant increases 

in standing crop coincided with a significant decrease in 

mean DAP score from 7.09 in August to 6.39 in November. 

The increase in standing crop and decrease in DAP score 

are all consistent with the results of a companion study 

(George and Baldigo, 2015) that identified the bloomforming diatom Didymosphenia geminata in significantly 

greater densities during November. During August, D. 

geminata was not detected upstream from the portal and had 

a mean cell density of 51 cells per square centimeter at sites 

downstream from the portal. In contrast, the mean cell density 
14 Response of Periphyton Fatty Acid Composition to Supplemental Flows in the Upper Esopus Creek, New York

60 percent

similarity

U–0

U–2

U–2n

U–3a

U–3an U–3

D–3b

D–3bn

U–3n

D–4a

D–4an

D–4

D–4b

D–5 D–6n D–6

2D Stress: 0.08 Two-way ANOSIM test

U vs. D: R = 0.595, P = 0.001

 August vs. November: R = 0.989, P = 0.001

EXPLANATION

Upstream sampling site

Downstream sampling site

Figure 5. Nonmetric multidimensional scaling ordination based on square-root-transformed species abundance data of diatom 

assemblages collected during August and November 2009 from sites on the upper Esopus Creek upstream or downstream from the 

Shandaken portal, New York. Site identification numbers ending with n denote samples from November; bubbles indicate 60 percent 

similarity. Site locations and identification numbers are identified in table 1. Results of the two-way analysis of similarity (ANOSIM) test 

show the significance of the two factors (location [upstream or downstream] and season [August or November 2009]). Two-dimensional 

(2D) stress is a measurement of the goodness of fit of the arrangement of points in the ordination. U, upstream; D, downstream; 

vs., versus.

of D. geminata in November was 8 cells per square centimeter 

upstream from the portal and 1,352 cells per square centimeter 

downstream from the portal. Streams with severe blooms of 

D. geminata often exhibit vast increases in algal standing 

crop (Spaulding and Elwell, 2007; Kilroy and others, 2009). 

This phenomenon may explain the large increase in chl a

and AFDM observed in the Esopus Creek between August 

and November. Diatom species ordinations showed strong 

clustering by season (fig. 5), and assemblages at all sites 

sampled in November were at least 60 percent similar to each 

other, yet no single pair of November and August assemblages 

reached this degree of similarity. This result strongly indicates 

that seasonal influences on the diatom community exceeded 

any effects from the supplemental flows from the portal.

Despite these notable changes between the August and 

November samples, fatty acid analysis failed to differentiate 

between the two sampling seasons. None of the summary 

metrics differed significantly by season, and only the relative 

abundance of the PUFA 22:5ω3 differed significantly between 

August (0.14 percent) and November (0.59 percent) samples. 

Multivariate analysis of fatty acid assemblages also indicated 

that the August and November groups were not significantly 

different. Honeyfield and Maloney (2014), however, 

recently reported seasonal changes in the fatty acid content 

of periphyton in six Pennsylvania streams that included 

significant differences between summer and fall samples. The 

reason that the fatty acid data from the upper Esopus Creek 

did not differentiate by season is unknown but it is likely that 

changes in other components of the periphyton community 

that were not directly assessed, such as filamentous algae, 

also affect the proportions of available fatty acids in the upper 

Esopus Creek.
Summary 15

Limitations of Study and 

Recommendations for Future Work

Several limitations of this initial study should be 

considered and may benefit future research in this emerging 

field. Although results of this study did not indicate a direct 

relation between turbidity or suspended sediment and 

individual fatty acids or summary metrics, the values of these 

parameters were low for all samples. In studies with known 

impairment of water quality, such as acid mine drainage 

(Genter and Lehman, 2000) or chlorine-contamination 

(Napolitano and others, 1994), a link between water quality 

and fatty acid composition of periphyton has been noted. To 

identify a similar relation between fatty acids and turbidity or 

suspended sediment (if it exists), future studies will require 

a greater range in the measured values of these parameters. 

Additionally, periphyton communities have been observed to 

exhibit patchiness (Kawata and others, 2003) similar to that 

observed in terrestrial plant communities. This patchiness 

may explain why fatty acid composition was so distinctive 

at a few of the sites presented in this report. To overcome 

the problem of patchiness, periphyton samples should be 

collected following the U.S. Geological Survey protocol 

(Moulton and others, 2002) or a similar robust methodology 

that will account for spatial variability in community types. 

Additionally, a complete assessment of the algal community 

should be performed rather than an assessment of diatoms 

alone. A complete taxonomic assessment of the benthic algal 

community might have improved the interpretation of the fatty 

acid dataset in this study. Despite the limitations of the initial 

study in this report, fatty acid analysis may have potential 

as a tool for the assessment of water quality and aquatic 

ecosystem health.

Summary

The U.S. Geological Survey and the New York State 

Department of Environmental Conservation used fatty acid 

analysis of periphyton to characterize the local water quality 

and ecosystem condition of the upper Esopus Creek, New 

York in August and November 2009. The Schoharie Reservoir 

is in the Mohawk River drainage and provides supplemental 

flows to the upper Esopus Creek through a 29-kilometer 

underground aqueduct known as the Shandaken Tunnel as 

part of the New York City water supply system. The terminus 

of the Shandaken Tunnel is the Shandaken portal which has 

been the focus of controversy among local residents and 

anglers because the supplemental flows are sometimes turbid 

and are thought by some to negatively affect the aesthetic 

and biological integrity of the stream. Because the perceived 

effects of these supplemental flows are speculative, however, 

the overall effect of the altered suspended sediment and 

flow regimes on aquatic biota remains unclear. The study 

detailed in this report evaluated the hypothesis that periphyton 

communities have a fatty acid profile that allows for the 

detection of excessive turbidity and suspended sediment. To 

this end, periphyton fatty acid composition and standing crop 

(ash-free dry mass and chlorophyll a), structure and integrity 

of diatom communities, and water-quality parameters were 

analyzed and compared upstream and downstream from the 

Shandaken portal.

The fatty acid composition of periphyton in the upper 

Esopus Creek was assessed during two seasons upstream and 

downstream from the portal. These data were compared with 

measurements of periphyton standing crop, diatom community 

structure and integrity, and basic water-quality parameters. 

Periphyton samples were collected at 20 sites in the watershed 

in August 2009 and at 6 sites in November 2009. This 

combination of spatial and seasonal measurements helped to 

determine the effect of supplemental flows from the portal 

on the fatty acid composition of periphyton, assess the utility 

of fatty acid analysis as a tool for evaluating ecosystem 

condition, and explore spatial and temporal differences in the 

periphyton community.

 The effects of the supplemental flows from the portal on 

periphyton communities of the upper Esopus Creek were not 

as pronounced as anticipated. Measurements of periphyton 

standing crop and diatom community integrity indicated little 

evidence of impairment from the supplemental flows. The 

relative abundances of two physiologically important fatty 

acids, γ-linolenic acid (18:3ω6) and eicosapentaenoic acid 

(20:5ω3), however, were significantly lower downstream from 

the portal. Multivariate analyses of fatty acid profiles indicated 

significant differences between sites upstream and downstream 

from the portal, but individual fatty acids and summary 

metrics were not significantly correlated with turbidity or 

suspended sediment. Comparisons between seasons indicated 

differences in periphyton standing crop and diatom community 

structure and integrity, although the fatty acid profiles did not 

detect temporal changes.

Turbidity, specific conductance, and pH were all 

significantly greater at downstream sites than at upstream 

sites; however, none of the water-quality parameters reached 

levels that would be expected to cause a measurable response 

from the periphyton community. The minor effect of the 

portal on water-quality parameters during the study period 

provided a poor opportunity to test the hypothesis that fatty 

acid analysis of periphyton is sensitive to excessive turbidity, 

suspended sediment, or general changes in water quality. 

Despite this, a few analyses did detect changes in the fatty acid 

composition of periphyton downstream from the portal.

The study described herein provides only limited 

evidence that periphyton communities are responding to 

some characteristic of waters from the portal. Although some 

differences between upstream and downstream sites can 

be attributed to portal inflows, and the nutritional quality 

of periphyton may be slightly poorer downstream from 

the portal, the results in this report generally indicate that 

the Shandaken portal was not a source of impairment to 
16 Response of Periphyton Fatty Acid Composition to Supplemental Flows in the Upper Esopus Creek, New York

periphyton in the upper Esopus Creek during the study period. 

Although results of this study did not identify a direct relation 

between turbidity or suspended sediment and individual fatty 

acids or summary metrics, the values of these parameters were 

low for all samples. Despite the limitations of this initial study, 

fatty acid analysis may have potential as a tool to monitor 

periphyton nutritional composition that may reflect water 

quality and ecosystem health but needs to be further evaluated 

around a more definitive source of water-quality impairment.

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Appendixes

Appendix 1. Fatty Acid Composition of Periphyton at Sites 

Sampled on the Main Stem and Tributaries of the Upper 

Esopus Creek, New York

Appendix 2. Water-Quality Parameters and Daily Stream 

Discharge Collected between August 26 and November 3, 

2009, at Six Sites on the Upper Esopus Creek, New York

Appendix 3. Chlorophyll a, Ash-Free Dry Mass, and 

Diatom Assessment Profile Score for Sites Sampled on the 

Main Stem and Tributaries of the Upper Esopus Creek, 

New York
20 Response of Periphyton Fatty Acid Composition to Supplemental Flows in the Upper Esopus Creek, New York Table 1–1. Fatty acid composition of periphyton at sites sampled on the main stem and tributaries of the upper Esopus Creek, New York. [Fatty acid composition is in percent of contribution. Site identification numbers and locations are listed in table 1. --, not detected] Fatty acid Sites sampled in August 2009 Sites sampled in November 2009 U–0 U–2 U–3 U–3a D–3b D–4 D–4a D–4b D–5 D–6 T–0 T–1 T–2 T–3 T–4 T–5 T–6 T–7 T–8 T–9 U–2 U–3 U–3a D–3b D–4a D–6 Saturated fatty acids 12:0 -- 0.7 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 14:0 6.3 4.4 5.6 7.3 8.6 6.4 6.7 6.1 6.3 5.3 6.4 9.8 8.8 8.5 8.5 9.7 7.0 8.5 5.8 6.7 4.9 8.1 8.0 8.6 7.5 5.6 15:0 -- -- -- 0.3 -- -- -- -- -- -- 0.3 -- -- -- -- -- -- -- -- -- 0.5 0.3 -- -- -- -- 16:0 21.8 22.1 26.1 22.5 29.8 25.8 27.8 23.9 26.0 29.1 29.7 26.2 21.5 28.1 25.8 30.3 22.4 27.1 30.2 26.0 20.7 22.9 28.0 24.4 21.0 24.3 17:0 0.8 0.2 -- 0.6 0.5 0.4 0.4 -- 0.4 0.4 0.3 -- -- 0.7 0.6 0.5 -- 0.5 -- 0.6 0.6 0.7 0.5 0.9 0.6 0.4 18:0 5.7 9.7 1.9 3.7 4.4 3.2 3.7 3.1 3.8 3.6 2.5 3.7 2.8 4.4 3.6 3.7 2.2 3.9 4.9 3.7 14.4 5.0 4.3 5.3 4.2 3.4 20:0 0.5 -- -- -- 0.4 -- 0.3 -- 0.3 0.3 0.2 0.4 0.4 0.5 0.4 0.3 -- 0.5 0.6 0.4 0.8 -- 0.3 -- -- -- 22:0 -- 0.2 -- -- -- 0.2 0.2 0.2 -- -- 0.1 -- -- -- -- -- -- 0.1 0.3 0.2 0.5 -- 0.2 0.2 -- -- 23:0 -- 0.4 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 0.2 -- -- -- -- -- 24:0 -- 0.3 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- Total 35.1 38.0 33.5 34.4 43.6 35.9 39.0 33.3 36.8 38.6 39.5 40.1 33.3 42.3 38.9 44.5 31.6 40.6 41.7 37.6 42.5 37.0 41.3 39.4 33.4 33.6 Monounsaturated fatty acids 15:1 -- -- 0.4 -- -- -- 0.3 -- -- -- -- -- -- -- -- 0.5 -- -- -- -- -- -- -- -- 0.6 -- 16:1ω7 18.5 17.4 41.7 16.9 21.7 35.8 34.2 29.5 26.8 18.4 41.8 17.6 31.4 17.6 28.1 24.2 32.0 28.4 23.6 23.8 11.2 17.9 23.0 18.2 36.0 29.1 18:1ω9c 7.7 3.1 5.6 5.7 6.2 4.9 5.0 5.3 5.2 4.3 3.6 4.2 7.1 4.7 5.4 4.6 6.2 5.0 5.1 4.9 14.4 5.6 5.2 7.3 4.9 5.0 20:1ω9 0.3 0.3 -- 0.2 0.5 0.3 0.2 0.2 -- 0.3 -- 0.7 -- 0.7 0.2 0.5 -- 0.3 0.3 -- 9.0 0.2 0.2 -- -- 0.3 22:1ω9 0.5 0.9 0.3 0.5 0.4 0.3 0.3 0.3 0.3 0.3 0.2 0.4 0.4 0.5 0.4 0.4 0.4 0.4 0.4 0.3 -- 0.5 0.3 0.8 0.4 0.3 24:1ω9 -- 0.2 -- -- 0.3 0.3 0.3 -- -- 0.2 0.2 0.7 -- 0.6 -- 0.4 0.4 0.4 0.5 0.3 0.2 0.3 -- -- 0.4 0.4 Total 27.0 21.9 47.9 23.2 29.0 41.6 40.2 35.4 32.3 23.5 45.7 23.7 38.8 24.0 34.1 30.5 39.0 34.5 29.9 29.3 34.8 24.5 28.8 26.4 42.4 35.0 Polyunsaturated fatty acids 18:2ω6c 7.7 3.9 3.1 4.3 6.5 5.0 3.8 5.5 6.3 7.4 2.4 9.0 5.6 7.2 4.6 5.3 4.4 4.5 5.6 4.7 7.2 3.9 5.4 4.2 3.4 5.0 18:3ω3 16.1 16.8 1.9 19.2 9.9 7.5 6.9 15.2 15.3 24.5 2.8 17.0 6.4 14.8 8.4 10.2 5.7 8.1 9.7 14.1 2.7 15.7 13.2 6.0 7.6 15.0 18:3ω6 0.9 1.4 0.9 1.0 0.6 0.6 0.7 0.7 0.6 0.5 0.7 0.8 1.1 0.8 0.8 0.8 1.1 0.9 0.9 1.1 0.3 1.1 0.8 0.8 0.6 0.8 20:2ω6 2.7 -- 1.4 1.8 1.1 0.9 1.2 1.1 1.0 0.7 1.0 1.2 1.3 1.6 1.6 1.2 2.0 1.1 1.2 1.2 1.1 2.3 1.0 2.0 1.5 1.5 20:3ω3 0.2 -- -- 0.3 0.2 -- -- -- -- 0.2 -- -- -- 0.2 -- -- -- -- -- 0.2 -- 0.3 0.2 -- -- 0.2 20:3ω6 -- 0.2 -- -- 0.3 -- -- -- -- -- 0.1 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 20:4ω6 0.7 0.4 1.7 0.4 1.0 0.6 0.5 0.5 0.5 0.5 0.7 0.9 1.3 0.6 1.0 0.6 0.9 0.8 0.8 0.5 1.1 0.4 0.6 0.9 0.3 0.4 20:5ω3 8.8 16.5 9.4 14.1 7.3 7.4 7.3 8.0 6.9 3.8 6.4 5.9 11.6 7.2 9.6 6.2 14.3 8.9 9.1 10.4 3.6 13.6 8.0 19.0 10.2 7.6 22:2ω6 0.6 -- 0.2 0.4 0.3 0.3 0.4 0.4 0.4 0.3 0.2 0.4 0.4 0.5 0.5 0.3 0.6 0.4 0.4 0.6 -- 0.4 0.3 0.4 0.5 0.4

22:5ω3 0.3 0.4 -- 0.4 0.2 0.2 -- -- -- -- 0.2 0.6 -- 0.5 0.3 0.2 0.4 0.3 0.4 0.3 1.7 0.4 0.3 0.6 0.3 0.322:6ω3 -- 0.5 -- 0.6 -- -- -- -- -- -- 0.2 0.5 -- 0.4 0.4 0.3 -- -- 0.4 -- 5.1 0.5 0.3 0.4 -- 0.3

Total 38.0 40.1 18.6 42.4 27.4 22.5 20.8 31.3 30.9 37.9 14.7 36.2 27.8 33.7 27.0 25.1 29.4 24.9 28.4 33.1 22.8 38.6 29.9 34.2 24.3 31.4
Appendixes 21

Table 2–1. Water-quality parameters and daily stream discharge collected between August 26 and November 3, 2009, at six sites on 

the upper Esopus Creek, New York.

[Number of samples (n) = 3 for water-quality parameters at all sites except for site U–3 where n = 2. Site identification numbers and locations are listed in 

table 1. SD, standard deviation]

Parameter

Site identification number

U–2 U–3 U–3a D–3b D–4a D–6

Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD

Nitrate, in micromoles per liter 7.5 4.7 7.9 5.3 6.7 3.5 8.4 2.9 7.3 1.4 5.7 0.5

pH 7.00 0.29 7.06 0.28 7.10 0.19 7.16 0.15 7.18 0.18 7.22 0.21

Specific conductance, in 

microsiemens per centimeter at 

25 degrees Celsius

49.3 10.7 48.4 7.6 53.1 8.8 61.6 14.2 56.9 13.3 61.7 12.2

Stream discharge, in cubic meters 

per second

1.5 1.6 2.1 2.1 2.2 2.3 8.9 3.0 12.3 6.5 14.5 9.2

Total suspended sediment, in 

milligrams per liter

1.0 0.9 1.0 0.0 0.7 0.3 4.0 4.4 2.7 1.2 1.7 1.2

Turbidity, in nephelometric 

turbidity units

1.4 0.7 1.7 0.2 1.3 0.3 5.0 5.0 4.1 1.2 3.0 1.2
22 Response of Periphyton Fatty Acid Composition to Supplemental Flows in the Upper Esopus Creek, New York

Table 3–1. Chlorophyll a, ash-free dry mass, and diatom assessment profile score for sites sampled on the 

main stem and tributaries of the upper Esopus Creek, New York.

[Number of samples per site (n) = 3 except diatom assessment profile scores in August where n = 4. Site identification numbers 

and locations are listed in table 1. μg/cm2, microgram per square centimeter; mg/cm2, milligram per square centimeter; SD, standard deviation]

Site

identification 

number

Chlorophyll a, 

in μg/cm2

Ash-free dry mass,

in mg/cm2

Diatom assessment

profile score

Mean SD Mean SD Mean SD

Sites sampled in August 2009

U–0 0.82 0.23 0.36 0.12 7.23 0.25

U–2 2.50 1.77 0.80 0.39 7.03 0.33

U–3 2.43 1.62 1.08 0.81 7.09 0.31

U–3a 4.53 3.04 1.75 1.21 7.39 0.25

D–3b 1.97 0.35 0.78 0.13 7.20 0.34

D–4 1.84 1.01 0.67 0.26 6.50 0.24

D–4a 1.80 0.45 0.47 0.06 7.07 0.53

D–4b 4.22 1.12 0.96 0.33 7.25 0.36

D–5 3.81 1.84 1.62 0.33 7.04 0.20

D–6 3.95 0.18 1.85 0.78 7.05 0.27

T–0 4.06 1.97 1.05 0.36 7.24 0.14

T–1 5.93 2.77 1.40 0.63 6.83 0.14

T–2 9.63 1.14 1.37 0.13 7.21 0.29

T–3 3.16 1.67 0.77 0.25 6.72 0.41

T–4 6.15 3.55 1.33 0.71 6.61 0.28

T–5 6.48 2.86 0.92 0.34 6.76 0.09

T–6 3.36 0.43 0.73 0.09 7.13 0.23

T–7 2.67 0.16 0.62 0.08 7.36 0.22

T–8 7.45 3.49 1.18 0.31 7.35 0.14

T–9 4.87 0.91 0.89 0.17 6.30 0.37

Sites sampled in November 2009

U–2 11.27 5.80 2.59 1.28 6.36 0.18

U–3 12.40 1.94 2.33 0.16 6.48 0.20

U–3a 13.10 3.48 2.95 0.95 6.21 0.24

D–3b 20.77 6.66 5.98 2.54 6.51 0.31

D–4a 11.15 3.43 3.49 1.01 6.03 0.16

D–6 6.59 1.49 1.78 0.24 6.76 0.33
For additional information write to:

Director, New York Water Science Center

U.S. Geological Survey

425 Jordan Road

Troy, NY 12180-8349

Email: dc_ny@usgs.gov

Information requests:

(518) 285-5602

or visit our Web site at:

http://ny.water.usgs.gov

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George and others—Response of Periphyton Fatty Acid Composition to Supplemental Flows in the Upper Esopus Creek, New York—SIR 2015–5161

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20155161