Mechanisms of UV radiation tolerance displayed

Lehigh University
Lehigh Preserve
Theses and Dissertations
2004
Mechanisms of UV radiation tolerance displayed
by benthic stream mayfly nymphs
Laura J. Shirey
Lehigh University
Follow this and additional works at: http://preserve.lehigh.edu/etd
Recommended Citation
Shirey, Laura J., "Mechanisms of UV radiation tolerance displayed by benthic stream mayfly nymphs" (2004). Theses and Dissertations.
Paper 860.
This Thesis is brought to you for free and open access by Lehigh Preserve. It has been accepted for inclusion in Theses and Dissertations by an
authorized administrator of Lehigh Preserve. For more information, please contact preserve@lehigh.edu.
Shirey, Laura J.
Mechanisms of
UV Radiation
Tolerance
Displayed by
Benthic Stream
Mayfly Nymphs
May 2004
Mechanisms ofUV radiation tolerance displayed by benthic stream mayfly nymphs
By
Laura J. Shirey
A Thesis
Presented to the Graduate and Research Committee
of Lehigh University
in Candidacy for the Degree of
Master of Science
III
Earth and Environmental Sciences
Lehigh University
April 30, 2004
ACKNOWLEDGEMENTS
I would like to acknowledge the following people for their support
during this project:
Dr. Craig Williamson, for his advice, patience and contagious
motivation,
Dr. Donald Morris and Dr. Richard Weisman, for their feedback and
enthusiasm for the project,
Danielle Powers, for tirelessly assisting in the field and laboratory,
Dr. Gabriella Dee, Sandra Cooke, Shawna Gilroy and Sandi Connelly,
Dr. Bruce Hargreaves and George Yasko for constant support and advice,
Nancy Roman and Laura Cambiotti, who guided me through my
graduate career,
Dr. David Mitchell who provided and analyzed DNA dosimeters,
Amanda Ault, Yen Tang, Patrick Belmont, Sandra Cooke and Dani
Frisbee for field and laboratory assistance,
My family and friends, who have always supported me.
This project was funded by the EPA Star (Science to Achieve Results)
Grant # R829642.
111
TABLE OF CONTENTS
Certificate of Approval.
.ii
Acknowledgements
.iii
List of Tables
v
List of Figures
vi
Abstract.
1
Part I: Introduction and Literature Review
2
Part II: Methods
11
Part III: Results from Experiments
17
Part IV: Discussion
28
Literature Cited
36
Appendix I
40
Appendix II
43
Appendix 111.
45
Appendix IV
'"
46
Appendix V
49
Curriculum Vitae
52
IV
LIST OF TABLES
Table 1. GPS coordinates of sampling sites
16
Table 2. Percent ofirradiance of wavelength 320 nm remaining at 10 em
20
Table 3. Biological, chemical and physical characteristics of sampling sites.21
Table 4. Mayfly characterization
22
Table 5. Experimental phototron data
.22
Table 5. 305 nm absorbance coefficients for each stream and method
.42
Table 6. 320 nm absorbance coefficients for each stream and method
.42
Table 7. 380 nm absorbance coefficients for each stream and method
.42
Table 8. PAR nm absorbance coefficients for each stream and method
.42
Table 9. Physical characteristics of Monocacy Creek
.43
Table 10. Physical characteristics of Saucon Creek
.43
Table 11. Physical characteristics of Little Lehigh Creek
.43
Table 12. Physical characteristics of Switzer Creek
.43
Table 13. Physical characteristics of Sand Spring Creek
.44
Table 14. Physical characteristics of Choke Creek
.44
Table 15. Physical characteristics of Ash Creek
.44
Table 16. Leaf area index
45
Table 17. LE50 of additional organisms tested with phototron
Table 18. DNA dosimeter data
.46
50
LIST OF FIGURES
Figure 1. Layers ofUV interception
.10
Figure 2. Percent of irradiance at 320 nm remaining at depth of
site vs. LE50 (PRR+) of dominant mayfly from native site
23
Figure 3. Endpoint phototron data for Monocacy experiment.
24
Figure 4. Endpoint phototron data for Saucon experiment.
24
Figure 5. Endpoint phototron data for Little Lehigh experiment.
.25
Figure 6. Endpoint phototron data for Switzer experiment.
25
Figure 7. Endpoint phototron data for Sand Spring experiment.
26
Figure 8. Endpoint phototron data for Choke experiment.
26
Figure 9. Endpoint phototron data for Ash experiment..
27
Figure 10. Endpoint phototron data for Hydropsyche experiment..
.47
Figure 11. Endpoint phototron data for Psephenidae experiment.
47
Figure 12. Endpoint phototron data for Chironomidae experiment..
.48
ABSTRACT
Little or no infonnation is available on the mechanisms of UV tolerance
exhibited by stream macroinvertebrates. This study used a standard UV exposure
apparatus (UV phototron) to examine the UV tolerance of several species of
mayfly nymphs. The UV phototron separates UV tolerance into two component
mechanisms of defense: photoenzymatic repair (PER) and dark repair and
photoprotection (DRPP). Nymphs of the dominant mayfly species were collected
from seven study streams with varying UV transparencies from the Lehigh River
watershed. Organisms were exposed to multiple levels of UV in the phototron in
the presence and absence of photorepair radiation (PRR). UV tolerance in all
mayfly species was substantially greater than the tolerance of zooplankton
collected from lakes in the same geographic region. Tolerance was not, however,
related to the UV transparency of the stream. Of the five species for which the
mechanisms of UV tolerance were examined, none appear to use PER. This is in
contrast to many tested lake species that depend heavily on PER. This is the first
study to document the effect of photorepair radiation in benthic
macroinvertebrates in streams. Even with the substantial levels of DRPP used by
some benthic macroinvcrtebrates, mayflies are likely to incur UV damage in the
absence of behavioral avoidance of full solar UV in the benthos of streams.
PART 1: INTRODUCTION AND LITERATURE REVIEW
INTRODUCTION
With reported ozone depletion, the amount of UV-B radiation (280-320
nm) reaching the Earth's surface has increased (Stolarski et al. 1992). This
radiation can penetrate freshwater and marine systems, potentially damaging
aquatic organisms at the cellular level. While considerable research has been done
on UV interactions with lake and marine invertebrates (Dey et al. 1988; Leech
and Williamson 2000; Williamson et al. 2001), less is known about UV as it
relates to the biota of streams and rivers.
In some ways, studying impacts on rivers can be more difficult than on
lakes because of their extremely dynamic nature. However, UV may play an
important role in the ecology of streams due to their shallow nature.
Characteristics like canopy cover, land use, nutrient inputs and sediment loads can
vary within a single stretch of stream. Some of these factors contribute to the
several layers that may intercept UVR before it can damage DNA of a stream
benthic organism (Figure 1).
UV -ABSORBING PROPERTIES OF TIlE
SlREAM ENVIRONMENT
Ozone provides the primary layer of interception of shorter, high-energy
wavelengths of UVR. It absorbs virtually all of the most potentially damaging
wavelengths in the UV-C range (200-290 nm). It is less effective at filtering UVB wavelengths (290-320 nm). which can also be potentially damaging to
organisms. Longer wavelength UV-A radiation (320-400 nm) readily passes
through ozone and can produce either positive or negative effects on an organism.
Stream systems additionally may have a canopy cover that intercepts a
portion of the incoming UVR. While this second layer is not generally important
in larger lake systems, the UV environment in low-order streams can be highly
dependent on this variable characteristic. The impact of canopy cover on the UV
environment can be influenced by the percent of open sky blocked by canopy and
the placement of the canopy in relation to the sun's angle and path across the sky.
In aquatic systems, water chemistry and clarity can control how much
damaging UV reaches the organisms. Dissolved organic carbon (DOC)
compounds, composed of humic substances in the water column, have been
shown to be an important external regulator of UV transparency of lakes. The
chromophoric dissolved organic matter (CDOM), the colored subset of DOC,
absorbs and thus decreases the amount of UV in greater depths of the water
column (Morris et al. 1995; Scully and Lean 1994). DOC concentration can be
generally correlated to the transparency of the system. However, processes acting
upon the DOC molecules in the system, like photobleaching and
photodegradation, reduce the UV-absorbing capabilities of DOC (Morris and
Hargreaves 1997).
UVR-f:',1)UCED DNA DAMAGE
The organism itself can provide several methods of protc{;tion from DNA
damage by UVR. As a primary layer within the organism, pigments may absorb
3
some radiation before it reaches the DNA. Various pigments including
mycosporine-like amino acids and carotenoids have been shown to be effective in
lake zooplankton, and may be produced within an organism or obtained from its
diet. These techniques, although energetically costly, are effective for
photoprotection (Cockell and Knowland 1999).
If UVR reaches the DNA of a cell, it is capable of causing biological
damage. Lesions in DNA are produced when high-energy, shorter wavelength UV
is absorbed by the molecule. While the peak absorbance wavelength of a DNA
molecule is 260 nm, wavelengths in the UV-C range are absorbed by the ozone
layer. However, of the wavelengths that reach Earth's surface, UV-B can also
produce DNA damage.
DNA damage may be repaired through molecular processes over short
time scales. Two common methods of DNA repair are nucleotide excision repair
(NER), and photoenzymatic repair (PER). NER, or "dark repair" is available to all
taxa and uses multiple proteins to repair damaged regions of DNA. NER is not
specific to repair of UVR-induced DNA damage (Mitchell and Karentz 1993).
Conversely, PER is only available to some organisms, and uses longer UV-A
wavelengths (320-400 nm) to activate the enzyme photolyase, that can repair UVB induced lesions (Sancar 1994; Zagarese and Williamson 1994). The availability
of these defense mechanisms to organisms can depend on both the taxa and the
developmental stage (Grad and Williamson 2001).
4
RESPONSE OF LAKE AND STREAM INVERTEBRATES TO UVR
Zooplankton have been shown to use three types of UV-mediation
techniques. Behaviorally, lake zooplankton can avoid UV by migrating to deeper
waters during peak light hours. Many zooplankton are phototactic and at least
some species, such as Daphnia, are capable of detecting and avoiding UV (Leech
and Williamson 2001). Secondly, pigments in the organism can provide
photoprotection by absorbing the UV before it reaches DNA. Finally, some lake
zooplankton have molecular mechanisms to repair DNA damaged by UV-B such
as dark repair and the light-mediated DNA repair process PER (Grad and
Williamson 2001; zagarese and Williamson 1994).
Stream invertebrates may have many of the same UV avoidance
mechanisms possessed by lake zooplankton. Unlike lake ecosystems, the primary
level of UV-interception in streams is the tree canopy cover in the riparian zone.
Both systems, however, contain DOC that attenuates UV over short depths.
The behavior of benthic invertebrates is a complex interaction between
light, predator avoidance and food forage behavior. In lake zooplankton this
behavior may be manifested as diel vertical migration. In streams this behavior
may consist of changes in drift or migrating under rocks or into the sediments to
avoid UV exposure. In both systems, the behaviors may reduce the organisms'
potential exposure levels to UV. While this study will focus primarily on
biological UV tolerance of invertebrates, it is important to acknowledge that
behavioral differences exist and can strongly impact the amount of UV to which
they arc exposed.
5
Some benthic invertebrates, including many mayfly larvae, have been
shown to be negatively phototactic (Giller and Malmqvist 1998), and a parallel
behavior of diel vertical migration of lake zooplankton may be the tendency to
spend daylight hours under rocks. Several species have been shown to use UV-A
as a trigger for behavioral avoidance (Bothwell et al. 1994; Kelly and Bothwell
2002b; Larow 1971). The behaviors enable them to avoid the more harmful UV-B
wavelengths. In a colonization experiment, Kelly and Bothwell (2002b)
manipulated a stream using UV filters. One treatment allowed the full spectrum to
penetrate, another screened only UV-B, and the third screened both UV-A and
UV-B. While there was no significant difference in the final biomass of
Dicos11l0eCllS sp. between the UV-B-filtered area and the unfiltered area, there
was a significant increase in Dicos11l0eCllS biomass in areas screened from both
UV-A and UV-B. This suggests that the species is able to detect and avoid UV-A
radiation. Similar results have been found for blackflies, Clzaoboms and
ClzirOl1011lidae larvae (Kelly and Bothwell 2002b).
A common paradigm with benthic invertebrates is that they spend a
significant portion of time under rocks and are not generally exposed to UVR.
The biological relevance of testing their UV tolerance therefore, would seem
negligible. It has been shown that many invertebrates exhibit these behaviors in
an effort to avoid predation (Peckarsky 1996). However, exceptions are frequently
made by individuals. Drift of benthic invertebrates, frcquently resulting from
anthropogenic stresses like acidification or othcr pollutants (Courtney and
Clemcnts 1998: Hall ct a1. 1980) can additionally expose im'crtcbratcs to UV.
6
While there is generally a nocturnal periodicity of mayfly drift, drift can occur
during the day. Waters (1972) placed invertebrate drift into three main categories:
(1) catastrophic, where invertebrates enter drift due to a physical disturbance,
unusually fast current, or in response to pollutants, (2) behavioral, where drift is
due to normal activities like food searching, normally higher at night, and (3)
constant, which is the low numbers of organisms found in drift that is unrelated to
stressors or time of day (Waters 1972) .
The first and third drift types suggest that the organisms could be
potentially exposed to UV light at any time of day. Catastrophic drift can occur as
a result of stresses like low oxygen or cold temperatures (Lowell and Culp 1999;
Rahel and Kolar 1990). In these conditions, catastrophic drift will cause
invertebrates to be exposed to UV when they are already under stress. The second
type, behavioral drift, is more prevalent at night, but it can still occur during the
day due to individual needs. Hunger levels could cause a mayfly to drift more
frequently between patches in search of food. Baetidae mayflies, in particular,
frequently swim from patch to patch in search of better food. This exposes them
not only to UV, but makes them more at risk for fish predation and to the water
current. In addition to drift, mayflies can crawl on top of rocks when avoiding a
predator, searching for food, etc. They sometimes congregate on sunny patches of
rocks in order to feed on periphyton growing on the rocks (Cushing and Allan
2001).
As an example of how behavior can cause different exposures to UV, we
can compare two families of mayfly n)mphs. Hcptagcniidac and Bactidac. The
7
two families are frequently found in the same streams, but because of behavioral
differences, can be exposed to very different amounts of UV. Heptageniidae, a
common "clinging" larva, possesses a dorsoventrally flattened morphology and
clings to the substrate. They are scrapers, feeding on algae and the biofilm
attached to the substrate. While grazing requires moving around on the substrate's
surface, they are potentially able to spend the majority of their time under rocks,
out of UV light, and rarely enter drift (Wilzbach et al. 1988). Baetidae, however,
have "swimming" larvae that possess a streamlined morphology. They are
gathering-collectors, feeding on patches of fine particulate organic matter.
Baetidae cling to the substrate between frequent but short durations of swimming
or drifting to new patches (Cushing and Allan 2001; Giller and Malmqvist 1998),
thereby potentially exposing the mayflies to short periods of UV.
Baetidae mayfly nymphs, in addition, have been shown to be positively
phototactic and therefore occupy areas exposed to high levels of light and UV
(Giller and Malmqvist 1998). Drift of Baetidae mayflies has been experimentally
shown to be stimulated by UV (Kiffney et a1. 1997).
BIOLOGY OF EPHEMEROPTERANS
Mayflies are small to intermediate sized insects found around the world in
areas with bodies of freshwater. Undergoing incomplete metamorphosis, the egg
is deposited in freshwater, in lakes, ponds or streams, depending on the species.
The egg hatches into the first instar of the nymph stage. typically at less than one
mm in length. The nymph continues to grow. molting multiple times: in some
S
species, over 40 molts occur. In the final nymph stage, the mayfly, usually
between 1-3 cm in length, emerges from the water in a winged, but sexually
immature, subimago stage. The mayfly then molts a final time, revealing the
exoskeleton and becoming the adult imago. The adult stage generally lasts only
several days, but in a few species, the adult stage may last as little as minutes or
as long as months. Cool and wet conditions allow the adults to persist longer in
the environment. During this short adult stage, the individuals mate and deposit
eggs in the water. The length of the life cycle varies; several generations may
occur in one year (as in Baetis), one generation may occur in one year, or one
cycle may require 2 to 3 years to complete, depending on species (Pennak 1978).
OBJECTIVES OF mE STUDY
This study acknowledges the potential for land use patterns to influence
the UV penetration in a system. For example, heavily forested areas limit the
amount of UV reaching the streams more than an agricultural stretch containing
little to no riparian buffer. A low-gradient, wetland-fed stream may contain more
UV-absorbing DOC than a stream with steeper slopes and no wetlands. These
land use patterns, combined with the shallow nature of streams, provide an
environment where the benthic invertebrates could be particularly vulnerable to
UV-induced damage. This study examines the UV tolerance of a common order
of stream benthic invertebrates, Ephcmcroptcra, as well as the mechanisms of
UV-mediation used by these invertebrates in a series of watersheds with varying
land uses. To do this. we used a UV-lamp phototron initially to manipulate the
9
total irradiance exposed to the organisms. The phototron also was used to separate
out the effects of shorter UV-B wavelengths from potentially beneficial longer
UV-A wavelengths. By observing the organism's response to the radiation in both
the presence and absence of UV-A, we can determine its overall tolerance to UV
and its ability to repair UV-incurred damage.
Figure 1. Layers of UV interception. Size of arrows represents intensity of UVR.
Layer 1: Ozone
+
Layer 4: Biological and Behavioral Strategies
10
PART II: METHODS
Stretches 5-10 m long in each of seven streams within the Lehigh River
watershed were chosen as study sites. The watershed covers over 2100 square
miles containing parts of both the Appalachian Plateau in its upper stretches and
the Lehigh Valley in the lower sections before it feeds into the Delaware River.
The study sites are low-order streams within small subwatersheds that have not
been substantially impacted by industrial or commercial growth. Sites were
chosen for availability of benthic invertebrates, representation of a range of UV
exposure levels, and accessibility. GPS coordinates are given in Table 1.
SITE CHARACTERIZATION
At each site, the amount of UV reaching the stream bottom was
characterized by measuring the attenuation coefficient of the water at baseflow
conditions, and by the depth of the stream. Measurements were made on July 1819,2003. The attenuation coefficient (KJ) of the water column was measured
using a submersible UV-PAR radiometer (BIC, Biospherical Instruments, Inc.,
San Diego, CA, USA), and the absorption coefficient (a), a correlate to KJ. was
measured using a mathematical model from a laboratory measurement of
dissolved absorbance (Appendix 1).
To determine the KJ. the submersible UV-PAR was lowered and raised in
the slowest and deepest region of the stream within 20 meters of the invertebrate
collection point. The radiometer records irradiance values at wavelengths of 305.
II
320,380 nm and PAR wavelengths (400-700 nm) and has a full width at half
maximum response of 8-10 nm. The attenuation coefficient (~) was calculated
using a regression between the natural log of the irradiance at a specific
wavelength verses the depth (m). Two profiles were taken at each stream. The
profile yielding regressions with the largest coefficient of determination (r-square)
values were used for analysis in the paper (Appendix II).
Laboratory measurements of absorbance were made using a Shimadzu
UV-1601 Spectrophotometer. Water samples were filtered through GFIF glass
fiber filters to remove particles within one day of sampling. An air-to-air baseline
and a blank with deionized water in a lO-cm cuvette was used to correct for
scattering by all factors other than dissolved substances in the sample. Filtered
samples were then scanned for absorption by wavelengths between 200 nm and
800 nm. Absorption coefficient (a) was calculated with the following equation:
a =(A sample - A blank)
* In (10) I path length (m).
where (Asamplc - Ablank) is the absorption as measured by the spectrophotometer.
The path length is the optical path length and in this case is 0.10 m (Kirk 1994).
Depth was measured in a systematic grid of 25 points within the riffle
where the invertebrates were collected. Measurements were taken at five evenly
spaccd intervals across the width of the stream. This was repeated in four
additional rows which were spaced evenly across the length of the riffle strctch.
The avcrage of thcse 25 points is reported as the average depth.
12
Further sampling was conducted at three times in summer 2003: June 18,
July 18-19 and September 10. On these dates, sites were further characterized by
their water chemistry and the presence of invertebrates. Dissolved oxygen, pH
and temperature were measured using the hydroprobe datasonde at baseflow
conditions. Dissolved organic carbon (DOC) was measured from filtered samples
using a Shimadzu TOC-5000. Quantitative invertebrate samples were taken at
each site by taking three I-square-foot invertebrate samples using a Surber
sampler in the riffle habitats. These individual samples were combined and
counted as a single sample for each stream. Sampling was conducted twice during
the summer of 2003. Samples were counted, and the most populous mayfly
species is reported as the dominant. Species were identified and classified
according to Needham et a1. (1935).
EXPER~NTALPROTOCOL
Benthic invertebrates were collected during the day using a 500 J,lm mesh
kick net at each of the seven sites. The invertebrates were transported to a
laboratory in coolers where the healthy nymphs of the dominant mayfly species
were isolated in filtered spring water. All isolated individuals were similar in size
and their lengths were measured after the experiment. Individuals were incubated
at 10 degrees Celsius overnight. The following morning treatment groups were set
up by placing five individuals in each of five replicate quartz dishes (1.8 cm deep,
4.6 cm inside diameter, -30 mL capacity) with filtered spring water. Dishes were
covered with quartz lids.
13
Organisms were exposed to UVR using a UV-lamp phototron
(Williamson, 2001) at several treatment levels. A UV-B lamp (Spectronics
XXI5B) was suspended 24 cm above a rotating wheel of 40 spaces for quartz
dishes. A piece of cellulose acetate was placed on the UV-B lamp to better
simulate solar radiation by cutting off wavelengths shorter than 295 nm. UV-B
exposure levels were varied by placing mesh screens on the dishes. Enclosed
beneath the wheel were lamps emitting photorepair radiation (PRR) consisting of
visible, UV-A, and a small amount of UV-B radiation. Presence or absence of
PRR was controlled with an opaque, black disk placed under the quartz dishes.
The entire phototron was contained within a temperature-controlled chamber.
Exposure levels ranged between no exposure (the control group) and an
upper value ranging between 39-103 kJ/m 2, depending on preliminary data of
species-specific tolerance to UVR (upper values for each site in kJ/m2: Ash, 39;
Sand Spring and Switzer, 64; Choke and Little Lehigh, 80; Monocacy, 87). Five
replicates of each exposure level, including a control group were exposed to the
UV lamp for 12 hours. Immediately following the 12-hour cycle, each dish was
removed from the phototron and living organisms were counted. Dead individuals
were removed. Dishes were returned to the lO-degree chamber and were kept in
the dark. The counting procedure was repeated once every 24 hours until the
endpoint, defined as five days after the exposure or when survival in the control
set fell below 90%, whichever came first.
STATISTICAL METHODS
14
Endpoint survival from the phototron was log transformed and then
analyzed by regression against exposure level to determine the LE50. Endpoint
survival was also arcsine square root transformed for use in ANaVA to determine
the significance of PER.
Regression analysis was used to determine if the LE50 of an organism
group was related to UV-transparency of its native stream.
15
r SI'tes.
T abie 1 GPS coord'mates 0 f sam Jimg
Stream
Monocacy
Saucon
Little Lehigh
Switzer
Sand Spring
Choke
Ash
latitude
(degrees N)
longitude
(degrees W)
40.414
40.525
40.496
40.662
41.174
41.162
41.218
75.215
75.451
75.646
75.7
75.597
75.603
75.551
16
elevation
(feet)
accuracy
(feet)
417.7
391.5
597.3
1569
1628
1519
74
28.1
25.3
44.8
21.4
72
51.1
PART III: RESULTS
SITE CHARACTERIZAnON
The study streams showed a 6.5 fold difference in the percent of irradiance
at 320 nm remaining at a 10 cm depth between the most transparent and least
transparent stream (Monocacy
=81.2%; Ash =12.4%) as estimated by the
dissolved absorbance (Table 2). Percent irradiance values, as estimated using the
submersible radiometer, gave similar values as those estimated by dissolved
absorbance from the same day of sampling. (Table 2). Both methods yield the
same rank order when streams are ordered by the transparency. Other methods to
estimate the percent of surface irradiance reaching 10 cm were used, but large
sources of error prevented the data from being relevant (Appendix I).
The average depths of the sites ranged from 11 cm to 23 cm (Table 3).
Depths within a single riffle were fairly uniform, yielding standard errors for
individual streams less than 3 cm.
Dissolved organic carbon concentrations varied by >2-fold, yielding
values between 1.24 in Monocacy Creek and 2.89 in Ash Creek. Stream pH
varied from 4.35 in Choke Creek, the most acidic stream, to 7.77 in Saucon
Creek, the most basic. All streams with pH <7 are located in the
P~ono
Plateau
(Sand Spring. Choke and Ash Creeks) while streams with pH >7 are locatcd
lowcr in the watershed in the Lehigh Valley (Monocacy, Saucon, Little Lehigh
and Switzcr Crecks). Dissolvcd oxygen concentrations ranged from 7.39 in
Switzer Creek to 9.74 in Sand Spring Creek. with the three streams in the Pocono
17
Plateau having the three highest DO concentrations and the lowest temperatures.
Individual measurements of these parameters are reported in Appendix n.
While the canopy cover was not fully characterized, initial data suggests
that the canopy is extremely variable both between and within sites (Appendix
ill). Ash and Saucon Creeks are the most open while the Little Lehigh and
Monocacy have the highest canopy cover.
Three genera of Ephemeroptera represented the dominant mayfly nymphs
in the study streams: Baetidae Leptophlebiidae, Baetidae Baetis and
Heptageniidae Stenonema. These mayflies were identified to species as shown in
Table 4. In all sites, the species labeled as dominant contained a greater number
of individuals than any other single species. In most cases, the dominant species
contained more than 50% of the total number of mayflies in the sample.
EXPERIMENTAL RESULTS
UV Tolerance ofmayfly nymphs
Experiments from four sites resulted in a significant exposure-response
within each experiment (Table 4, Figures 3-9). Mortality rate responses to each
exposure of UV-B radiation in Switzer, Monocacy and Choke were significantly
different than the response to other exposures within the same experiment (pvalues of <0.001). The Choke. Sand Spring. Little Lehigh and Ash experiments
did not show significant differences between exposures (p-values of 0.053.
0.0823.0.66 and 0.44 respectively).
IS
LE50 in the presence of the long wavelength photorepair radiation of the
dominant mayfly species of each stream is reported in Table 4. The most UV
tolerant species tested in this set of experiments was Paraleptophlebia moerens
from Choke Creek and Saucon Creek (LE50s of 71 and 62 kJ/m2 respectively).
The least UV tolerant species are Baetis cingulatus from Monocacy (LE50 of 56
kJl m2) and Baetis intennedius (LE50s of 52 kJ/m
2
)
from Switzer.
Mechanisms of UV-mediation
The LE50 calculated for the -PRR treatment was subtracted from the
LE50 calculated for the +PRR treatment. The difference is reported in Table 4.
No experiments gave conclusive evidence to support that the mayflies tested can
use photoenzymatic repair. The effect of PER was not examined in Choke or Ash
creek due to a limited number of organisms. In these experiments, organisms were
only run in the presence of photoenzymatic repair.
Environmental Correlations
The LE50 did not significantly correlate to the percent of 320 nm
wavelength light reaching the average depth of their native streams (p-value =
0.85, R-square =0.014, Figure 1).
19
Table 2. Percent of irradiance of wavelength 320 nm remaining at 10 em. Data in parentheses are
standard error. Only one measument of dissolved absorbance was made for Monocacy, so no
standard error is available. Average % irradiance values are calculated from samples from July
18, 2003 an d September 10, 2003
Stream
Monocacy
Saucon
Little Lehigh
Switzer
Sand Spring
Choke
Ash
% Irradiance320 at 10 cm
18vl103 from
Average from
diss. abs.
dissolved absorbance
18vil03 from
stream profile
90.7
61.3
60.7
46.7
35.2
15.7
14.1
81.2
63.3
63.4
53.3
43.4
16.8
14.6
20
81.2 (N/A)
61.7 (j-0.6)
57.3 (j-3.9)
51.8 (j-0.2)
41.7 (j-1.3)
17.0 (j-2.8)
12.4 f:r1.8)
Table 3. Biological. chemical and ohvsical ch
Stream
Dominant
Mayfly Species
B. cingufatus
P. moerens
~aucon
Little Lehiah S. femora tum
B. parvus, brunneicofof
Switzer
Sand Spring B. intermedius
P. moerens
Choke
B. cingufatus
Ash
Monocacy
N
......
---- - - - - - - - - - -
Avg Depth
(em)
23 (j-2.S)
15 (j-1.3)
13 (+1.B)
11 (j-1.9)
14 (j-1.7)
23 (:fO.S)
18 (j-O.S)
--f ------
r
----
-----
%320 at depth
of site using
Stream Profile data
80
48
52
43
23
1
3
Avg [DOC]
(ppm)
avg pH
1.24
7.49.
7.77
7.41
7.06
5.61
4.35
6.56
1.38 (j-O.OB)
1.39 (j-0.16)
1.65 (+0.19)
1.56 (j-0.14)
2.72 (j-0.31)
2.89 (j-0.26)
Avg
DO
-7.42
7.81
7.39 .
9.74
9.38
8.58
Temperature in
C at time of DO
measurement
-18.75
19.02
20.97
14.9
15.18
15.54
Table 4. Mayfly characterization and experimental phototron data. Data in parentheses of LE50 (+PRR) column are p-values denoting the
significance of the LE50 value. Data in parentheses of Effect ofPRR column are p-values denoting the significance of a difference between the
+PRR and the -PRR treatments
% of total
Dominant Mayfly
Average length
mayflies
of experimental
represented by
Stream
genus
organisms (mm)
this species
family
species
Monocacy
Sauoon
Little
Lehigh
Switzer
Sand
Spring
N
N
Choke
Ash
Baetidae
Leptophlebiidae
Baetis
Paraleptophlebia
cingulatus
moerens
3.9
6.0
97
56
Heotageniidae
Stenonema
7.7
48
Baetidae
Baetis
femoratum
parvus,
brunneicofor
5.2
84
Baetidae
Leptoohlebiidae
Baetidae
Baetis
Parafeptophfebia
Baetis
intermedius
moerens
cingufatus
3.8
3.2
3.1
63
71
70
Table 5. Experimental phototron data. P-values for +PRR and -PRR columns denote significance of a difference
between exposure levels within the treatment. Value and p-value of PER column denotes the contribution of PER
-_. d the significance of the difference between the +PRR and -PRR treatment
-PRR
+PRR
Monocacv
Saucon
Little Lehiah
Switzer
Sand Sprina
Choke
Ash
PER
LE50
p
LE50
p
value
p
56
62
58
52
57
71
80
<0.001
0.053
0.450
0.347
0.980
<0.001
0.446
53
0.003
3
0.872
n/a
n/a
32
55
20
0.770
<0.001
0.029
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
Figure 2. % of irradiance at 320 nm remaining at depth of site vs. LE50 (PRR+) of dominant
mayfly from native site.
LESO vs. % 320 Irradiance
70
•
60
-~40
-
50
y = 0.0514x + 44.587
R~
•
•
~ 30
= 0.0138
•
w
.J
20
10
o
o
20
40
60
80
%320 nm irradiance, based on stream profile, at depth of site
23
100
Figure 3. Endpoint phototron data for Monocacy experiment.
Monocacy Creek B. cinguiatus
Percent survival vs exposure
100 - , - - - - - - - - - - - - - - ,
-co
.~
60 --i----~~_t_-----___I
~
40--i-----~-f-'Io,.---'l!'---------I
cfl.
20 -t------t--~~---___I
80-t---~----------I
o -f-----,---r-----.,.-
o
25
50
-.-PRR+
. _. PRR-
r------l
75
100
125
Exposure level (kJ/m2)
Figure 4. Endpoint phototron data for Saucon experiment.
Saucon Creek P. moerens
Percent survival vs exposure
100
-co 80
.2: 60
c=
::3
en 40
~
0
20
0
-.-PRR+
. - - PRR-
III
~ -=...-.
T
"'1
0
I
I
25
50
I
75
100
Exposure level (kJ/m2)
24
125
Figure 5. Endpoint phototron data for Little Lehigh experiment.
Little Lehigh Creek S. femoratum
Percent su rvival vs exposu re
100
->cu
.~
::s
(/)
~
0
80
60
40
•
PRR+
- - - PRR-
I~
~ .1
20
~.
0
0
25
50
75
100
125
Exposure level (kJ/m2)
Figure 6. Endpoint phototron data for Switzer experiment.
Switzer B. parvus, brunneicolor
Percent survival vs exposure
100 - - . - - - - - - - - - - - - - - - ,
80 - I - - -.... . - - t - - - - " F - - - - - - - - - J
60
+-----'---1r--...--------j
40
+------+-.-------j
20
- I - - - - - -......F - - - - - - - J
o +,--~-__r_--.,....---_,...._-~
o
25
50
75
100
Exposure level (kJ/m2)
25
125
~
~
Figure 7. Endpoint phototron data for Sand Spring experiment.
Sand Spring B. intermedius
Percent survival vs exposure
100
as 80
.-> 60
c:
;j
UJ 40
-
~
0
fI
20
0
0
____ PRR+
I
- - - PRR-
, I
,
r
I
I
I
I
25
50
75
100
125
Exposure level (kJ/m2)
Figure 8. Endpoint phototron data for Choke experiment.
Choke Creek P. moerens
Percent su rvival vs exposu re
100 --.----------------,
-
80-l-----"l"""-:---------l
.~
60 -+----~~-----_i
~
40-f------~---------j
cfl.
20
co
-l--------"F----l
o +,
--.,----.,....-----r---..,....---~
o
25
50
75
100
Exposure level (kJ/m2)
125
Figure 9. Endpoint phototron data for Ash experiment.
-as
.~
c=
::s
m
~
0
Ash Creek B. cingulatus
Percent survival vs exposure
100
80
60
40
20
0
~
____ PRR+
h~1
0
- - - PRR-
I
I
I
25
50
75
100
Exposure level (kJ/m2)
27
125
PART IV: DISCUSSION
While many studies have been conducted on the role of visible light on
benthic macroinverebrates, only a few have considered the role of short
wavelength UVR. The studies that have been done on UV are typically related· to
drift behavior or UV interactions with chemical toxins (Kiffney et al. 1997;
Duquesne and Liess 2003). Results from many of these experiments do not
address the direct impact of UV on the organism. In order to have a better
understanding of these more complex interactions, we can first examine the UVspecific biological processes relating to benthic invertebrates. This study
considers one of the most widespread invertebrate taxa in stream communities,
the mayfly nymph. While this study does not directly explain what happens in
nature, it determines if UV does have a biological impact on the organism tested,
investigates the mechanisms of mediation and determines if one population of
organisms is more or less sensitive to UV than a population of a different species
or a different habitat.
This study shows that mayfly species vary in their tolerances to UVR. The
lethal exposure for 50% of the sample population (LE50) values for the mayflies
2
tested ranged from 56 to 80 kJl m • Hickey et al. (2002) report the LE50 of
Dclcatidiu11I sp. of mayfly to be 44.4 kJ/m 2, a value slightly lower than those of
the species shown in this study.
In response to UVR stressors, organisms used a combination of
photocnz)matic repair (PER) and dark repair and photoprotection (DRPP). None
28
of the organisms tested for the effect of photorepair radiation (PRR) had an ability
to use PER. No discernible trends were detected relating the mechanism of
protection and repair to either the organism species or to its habitat (Figure 2).
Based on evidence that some species increase the concentration of sunscreen
pigments, especially micosporine-like amino acids, when
acclim~ted to
increases
in UVR, we would expect a greater tolerance in mayflies found in more
transparent systems (Garcia-Pichel et al. 1993). However, the lack of trend
suggests that characteristics of an individual that can reduce UV damage are
independent of the individual's habitat.
It is clear from drift, foraging and other behaviors, that mayflies have the
potential to be regularly exposed to UVR. The overall behavioral differences
between the taxa used in the experiment, however, do not seem to relate to their
UV tolerances. If drift is considered to be the primary method of UV reaching the
organism, then it seems that Heptagelliidae mayflies would be the least exposed.
However, the tolerance of Heptagelliidae mayflies appears to be in the middle of
the tolerances observed by the different mayflies. Therefore, either behavior does
not ultimately control how much light reaches the organism, or the exposure
levels in nature do not dictate how tolerant an organism is to the stressor. With
the current research, it is not known if one species regularly receives a higher
nature exposure of UVR due to behavioral differences.
Differences in size of tested invertebrates could also confound the
relationship. While organisms of the same ta:'{a were similar in size, the large
number of instars makes it impossible to use the same instar across all treatments.
29
If UV tolerance varies with developmental stage, a tolerance relationship with UV
exposure could be hidden.
An alternative explanation is that the role of canopy is a more important
regulator of UV exposure than suggested in this project. For example, water
transparency alone would predict that organisms from Choke Creek would be
more UV tolerant. Choke Creek has a relatively light canopy cover (Appendix ill)
which may have increased the UV exposure in the stream. However, the role of
canopy is not at this time fully characterized, so it cannot be accepted as a
definitive explanation.
While direct effects of UVR do not dictate what type of organisms live in
a stream or the invertebrate's UV tolerance, indirect effects from UV could
complicate the relationship. Because the mayfly nymphs are sensitive to UV, it is
possible that the UV impacts the behavior. If the UV is causing them to alter the
amount of time under rocks verses in the water column, this could have impacts
on their access to food or exposure to predators.
In addition, effects of UV exposure on other trophic levels could indirectly
impact the benthic macroinvertebrate population. UV has been shown to cause
deleterious effects on several life stages of fish. Experiments have demonstrated
that UVR causes mortality due to DNA damage in fish eggs and larvae (Bell and
Hoar 1950; Kouwenberg et al. 1999; Wi11iamson et al. 1999). Adult fish can also
be damaged by UV-induccd lesions which lead to a greatcr susceptibility for
infection (Bul1ock 1982: Nowak 1999). Adult and juvenile fish also behaviorally
30
avoid UV (Kelly and Bothwell 2002a). The physical and behavioral effects on
fish could reduce predation pressures and create a refuge for mayflies.
UV may also playa role in the trophic level below benthic
macroinvertebrates. While UV has been shown to disrupt algal photosynthesis
and damage algal DNA, Bothwell et al. (1994) found that diatom biomass
increased under extended exposure to UV when in the presence of chironomids,
an important grazer. The discrepancy was found to be an indirect effect of the
higher UV sensitivity of the chironomid. If UV dose in the natural streams are
high enough to reduce chironomid populations, then increased algal biomass
would provide more food and less competition for the more UV tolerant mayflies.
UV tolerance in the presence of PRR in all tested mayfly nymphs was
substantially greater than the tolerance of zooplankton collected from lakes in the
same geographic region. LE50 of the lake cladoceran Daphnia is -15 kJ/m2 and
the LE50 of Asplanc1l1la is -20 kJ/m2. The LE50 of the mayfly nymphs tested
here are higher with values ranging from 53-80 kJl m2• Preliminary experiments
with the phototron on other stream benthic invertebrates suggest that the tolerance
of other organisms varies greatly, and that the UV sensitivity is at an intermediate
level in comparison to other popular organisms. Chironomids tend to be more
sensitive than mayflies while stoneflies and water pennies are extremely tolerant
of UV. A caddisfly (Trichoptera:HydropsychidaelHydropsyche) appears to show
a similar sensitivity to the tested mayflies (Appendix IV).
E~l'ERThI.E~lAL DESIG~
31
The invertebrates we used for this investigation were chosen primarily for
their tolerance to the collection and transportation process, survivorship in control
treatments and availability. Abundance was important because of the large
numbers of invertebrates needed for use in the phototron. However, larger
abundances of organisms could be an indication that the abundant species are
tolerant of the stressors present in nature and that, by default, the organisms that
are most sensitive to the stressor would not be tested.
Organisms within the same insect order were chosen for this set of
experiments to better allow comparisons to be made between streams. This was
not an attempt to explain why certain species lived in specific streams. Instead, it
was an attempt to examine mayflies from a gradient of natural UV exposure
levels to attain the highest likelihood of observing a variety of UV-mediation
mechanisms.
Several specific concerns arise when considering the experimentation
phase. The individuals were not fed after collection from the stream. This added
stress may have affected how well the individuals can handle an additional
stressor like UV. Although every individual was treated in the same manner, it is
possible that different individuals of the same species or those of different species
would react differently to shortage of food. Healthier individuals at the time of
collection may be able to handle the UV stress better than those who were
underfed or injured. An attempt was made to avoid the inclusion of unhealthy
individuals in the analysis by running the experiment the day after collection and
isolations. This way. each individual could be inspected just before the
32
experiment and only robust individuals would take part. Those who had already
died or who appeared weak or injured were not used.
STREAM CHARAClERIZAnON
In an effort to collect invertebrates from a representative sample of
streams throughout the Lehigh River watershed, streams were chosen based on
several characteristics. All streams in the study were low-order streams found
throughout the watershed in northeastern Pennsylvania. The heterogeneity of the
watershed contributes to a system of streams with variable water source types,
underlying geologies and riparian land coverages. Some streams have been
impacted by agricultural runoff, often having little to no riparian buffer, but
industrial or commercial development upstream of the collection location was
negligible.
Because the purpose of this study was to investigate how benthic
rnacroinvertebrates handle stresses from UVR, the streams were characterized
mainly by the potential for UV to penetrate the system. Water transparency was
used as the primary method of characterizing the UV environment of the streams
because it is one of the most stable UV-regulating conditions in a stream over a
large stretch. The sources of water and land coverage of the riparian zone heavily
affect the color, and therefore the transparency, of the water. Streams originating
in wetlands arc often rich in dissolved organic carbon (DOC), a reliable correlate
to water transparency (Morris et al. 1995: Pace and Cole 2002). Sand Spring.
Choke and Ash creeks. all located on the Appalachian Plateau were fed by DOC-
33
rich wetlands. The remaining four streams were located in the Lehigh Valley, did
not come from wetland sources, and had lower DOC concentrations. DOC
concentration varied by more than two-fold between the streams of the extreme
values. Other sources of transparency discrepancies were due to allochthonous
DOC from the vegetation type in the drainage basin and by contributions of
autochthonous algal DOC.
The transparency of the water column could have been correlated to the
DOC concentration or modeled by laboratory measurements of the absorption
coefficient (a) by the dissolved and particulate components of the water (Morris et
al. 1995). Instead, the vertical attenuation coefficient (Kd) as measured by using
the submersible radiometer was used to directly determine water transparency in
this study. The radiometer can measure the rate at which damaging 320-nm
wavelength light and other wavelengths attenuate in the water. The attenuation
coefficient allows for comparison between sites.
To estimate how much light was reaching the benthos and potentially the
organisms living there, the attenuation coefficient was used in conjunction with
the average depth of the streams. The challenge of this approach was quantifying
the depth of the stream. An individual stream could vary in depths from less than
6 cm to more than 1 meter within a 50-meter stretch. However, because the
invertebrates being tested live primarily in fast-moving, riffle areas, the
measurement recorded depths only on the riffle stretches. This reduced the
standard error within each stream to less than 3 cm and allowed comparison
between streams. The diffcrence in thc avcrage depth between streams was never
34
more 12 cm. However, because of the high UV absorbance capabilities of some of
the streams, a 12-cm difference could potentially playa role in regulating UV
attenuation. For this reason, it was important to include the depth in the
calculation of the amount of light reaching each stream's benthos.
Other UV-regulating characteristics like canopy cover may significantly
contribute to the regulation of UV reaching the benthos of the stream. An effort
was made to characterize the canopy in each of these streams; however, due to the
high variability within each site and the limitations of the interpretation of the
data, the percent canopy cover was not used in analysis. This patchiness of the
canopy cover, complicated with the unrelated patchiness of the stream depths,
made characterization of the role of canopy on the stream invertebrates beyond
the scope of this project. Preliminary measurements, however, show high
variability with standard errors ranging from 0% in Ash Creek to 21 % in the Little
Lehigh (Appendix III).
CONCLUSIONS
All of the tested invertebrates are susceptible to DNA damage by UVR
and are able to mediate damage entirely through DRPP. This is in stark contrast to
most tested lake invertebrates that rely heavily on PER. Relative LE50 values are
related to taxa, but the UV environment of the organisms' native stream does not
appear to directly influence tolerance. Although direct effects of UVR do not
seem to be important in regulating UV tolerance. feedbacks from UV interactions
with other trophic levels could be affecting mayflies indirectly. In comparison to
35
other tested macroinvertebrates, mayflies are more tolerant to UV than most lake
invertebrates taken from the same geographical region. However, compared with
preliminary experiments with other stream invertebrates, mayflies have an
intermediate sensitivity. This study provides the framework for studying the
effects of UV on stream benthic invertebrates. Because of the demonstrated
sensitivity to UV, further research is needed to determine in UV is regulating the
behavior of the organisms.
36
REFERENCES
BELL, G. M. AND W. S. HOAR. 1950. Some effects of UVR on sockeye salmon
eggs and alevins. Canadian Journal of Research 28: 35-43.
BOTIIWELL, M. L., D. M. J. SHERBor, and C. M. POLLOCK. 1994. Ecosystem
response to solar ultraviolet-B radiation: Influence of trophic-level
interactions. Science 265: 97-100.
BULLOCK, A.M. 1982. The pathological effects of ultraviolet radiation on the
epidermis of teleost fish. Proceedings of the Royal Society of Edinburgh.
81B: 199-210
CELLor, B. 1996. Influence of side-arms on aquatic macroinvertebrate drift in a
main channel of a large river. Freshwater Biology 35: 149-164.
COCKELL, C. S., and 1. KNOWLAND. 1999. Ultraviolet radiation screening
compounds. Biological Review 74: 311-345.
COURTNEY, L. A., and W. H. CLEMENTS. 1998. Effects of acidic pH on benthic
macroinvertebrate communities in stream microcosms. Hydrobiologia
379: 135-145.
CUSHING, C. E., and J. D. ALLAN. 2001. Streams: Their Ecology and Life.
Academic Press.
DEY, D. B., D. M. DAMKAER, and G. A. HERON. 1988. UV-B Dose/dose-rate
responses of seasonally abundant copepods of Puget Sound. Oecologia 76:
321-329.
DUQUESNE, S., AND M. LIESS. 2003. Increase sensitivity of the macroinvertebrate
Paramorea walkeri to heavy-metal contamination in the presence of solar
UV radiation in Antarctic shoreline waters. Marine Ecology Progress
Series 255: 183-191.
GARCIA-PICHEL, F.. C. Wl1\GARD AJ'ID R.W. CASTENHOLZ. 1993. Evidence
regarding the UV sunscreen role of a mycosporine-like compound in the
cyanobacterium Gloeocapsa sp. Applied and Environmental Microbiology
59: 170-176.
37
Gn..LER, P. S., and R. N. B. CAMBELL. 1989. Colonization patterns of mayfly
nymphs (Ephemeroptera) on implanted substrate trays of different size.
Hydrobiologia 178: 59-71.
Gn..LER, P. S., and B. MALMQVIST. 1998. The Biology of Streams and Rivers.
Oxford University Press.
GRAD, G., and C. E. Wn..LIAMSON. 2001. Zooplankton survival and reproduction
responses to damaging UV radiation: A test of reciprocity and
photoenzymatic repair. Limnology and Oceanography 46: 584-591.
HALL, R. 1., G. E. LIKENS, S. B. FIANCE, and G. R. HENDREW. 1980. Experimental
acidification of a stream in the Hubbard Brook Experimental Forest, New
Hampshire. Ecology 61: 976-989.
HICKEY, C.W., E.E. LITTLE, L.A. GOLDING. 2002. Sensitivity of native freshwater
fish and invertebrate species and the role of photoprotectant slime. In: UV
radiation and its effects: an update 2002: Proceedings of a workshop,
Christchurch, March 2002, pp. 58-61. RSNZ Miscellaneous Series No. 60.
Royal Society of New Zealand, Wellington.
KELLY, DJ. AND M.L. BOTHWELL. 2002a. Avoidance of solar ultraviolet
radiation by juvenile coho salmon (Oncorhynchus kisutch). Canadian
Journal of Fish and Aquatic Sciences. 59(3): 474-482.
KELLY, D. 1., and M. L. BOTHWELL. 2002a. Effects of solar UV radiation on
shallow stream invertebrates. National Institute of Water and Atmospheric
Research.
K!FFNEY, P. M., E. E. LITTI.E, and W. H. CLEMENTS. 1997. Influence of
ultraviolet-B radiation on the drift response of stream invertebrates.
Freshwater Biology 37: 485-492.
nd
KIRK, J.T.O. 1994. Light and photosynthesis in aquatic ecosystems. 2 ed.
Cambridge.
LARow, E. 1. 1971. Response of Chaoborus (Diptera: Chaoboridae) larvae to
different wavelengths of light. Ann. Ent. Soc. Amer 64: 461.
KOUWENBERG, J. H. M., H. I. BROWMAN, J. A. RUNGE, J. J. CULLEN, R. F. DAVIS,
AI'oTI J.F. ST-PIERRE. 1999. Biological weighting of ultraviolet-B induced
mortality in marine zooplankton and fish. 2. CalaTlllS fi1l1Tlarchiclis
(Copepoda) eggs. Marine Biology. 134: 285-293.
38
LEECH, D. M., and C. E. WILLIAMSON. 2000. Is tolerance to UV radiation in
zooplankton related to body size, taxon, or lake transparency? Ecological
Applications 10: 1530-1540.
---.2001. In situ exposure to ultraviolet radiation alters the depth distribution of
Daphnia. Limnology and Oceanography 46: 416-420.
LoWELL, R. B., and 1. M. CULP. 1999. Cumulative effects of multiple effluent and
low dissolved oxygen stressors on mayflies at cold temperatures. Canadian
Journal of Fisheries and Aquatic Sciences. 56: 1624-1630.
MITCHELL, D. L., and D. KARENIZ. 1993. p. 345-377. In A. R. Young, Bjorn,
L.O., Moan, J. & Nultsch, W. [ed.], Environmental UV Photobiology.
Mitchell, D. L., and R. S. Nairn. 1989. The Biology of the (6-4) photoproduct.
Photochemistry and Photobiology. 49: 805-819.
MORRIS, D. P., and B. R. HARGREAVES. 1997. The role of photochemical
degradation of dissolved organic carbon in regulating the UV transparency
of three lakes on the Pocono Plateau. Limnology and Oceanography 42:
239-249.
MORRIS, D. P. and others 1995. The attenuation of solar UV radiation in lakes and
the role of dissolved organic carbon. Limnology and Oceanography 40:
1381-1391.
NEEDHAM, J.G., J. R. TRAVER, AND Y. H. Hsu. 1935. The Biology of Mayflies
with a Systematic Account of North American Species. Ithaca: Comstock
Publishing Company.
NOWAK, B.F. 1999. Significance of environmental factors in aetiology of skin
diseases of teleost fish. Bulletin of the European Association of Fish
Pathologists. 19: 290-292.
PACE, M. L., and J. J. COLE. 2002. Synchronous variation of dissolved organic
carbon and color in lakes. Limnology and Oceanography 47: 333-342.
PECKARSKY, B. L. 1996. Alternative predator avoidance syndromes of streamdwelling mayfly larvae. Ecology 77: 1888-1905.
PE~'NAK,
R.W. 1978. Freshwater Invertebrates of the United States. New York:
Wiley-Interscience Publication.
RAHEL. F. 1.. and D. S. KOLAR. 1990. Trade-offs in the response of mayflies to
low oxygen and fish predation. Oecologia 84: 39-44.
39
SANCAR, A. 1994. Structure and Function of DNA photolyase. Biochemistry 33:
2-9.
SCULLY, N. M., and D. R. S. LEAN. 1994. The attenuation of UV radiation in
termperate lakes. Arch. Hydrobiol. 43: 135-144.
STOLARSKI, R., R. BOJKOV, L. BISHOPH, S. ZEREFOS, J. STAEHELIN, and 1.
ZAWODNY. 1992. Measured trends in stratoshperic ozone. Science 256:
342-349.
WATERS, T. F. 1972. The drift of stream insects. Annu. Rev. Entomol. 17: 253272.
WILLIAMSON, C.E., B.R. HARGREAVES, P.S. ORR, P.A. LoVERA. 1999. Does UV
playa role in changes in predation an zooplankton community structure in
acidified lakes? Limnology and Oceanography 44(3 part 2): 774-783.
WILLIAMSON, C. E., O. G. OLSON, S. E. LoTI, N. D. WALKER, D. R. ENGSTROM,
and B. E. HARGREAVES. 2001. Ultraviolet radiation and zooplankton
community structure following deglaciation in Glacier Bay, Alaska.
Ecology 82: 1748-1760.
WILZBACH, M. A., K. W. CUMMINS, and R. A. KNAPP. 1988. Toward a functional
classification of stream invertebrate drift. Verh. Internat. Verein. Limnol.
23: 1244-1254.
ZAGARESE, H. E., and C. E. WILLIAMSON. 1994. Modeling the impacts of UV-B
radiation on ecological interactions in freshwater and marine ecosystems.,
p. 315-328. III R. H. Biggs and M. E. B. Joyner [eds.], Stratospheric
Ozone Depletion! UV-B Radiation in the Biosphere. Springer-Verlag.
40
/.~
ApPENDIXI: OPTICALDATA
The attenuation coefficient for the water column at each site was used as
an indicator of the amount of UV reaching the bottom of the stream. In situ
analysis of the water was conducted at each on July 17 and 18,2003 for each site
except Monocacy Creek. Monocacy Creek was added to the experimental set in
early September, and was sampled on September 10, 2003. Water was also
collected in I-liter Nalgene bottles from each site for laboratory analysis on these
dates. All sampling dates were at baseflow conditions.
The attenuation coefficient was calculated using three methods: dissolved
absorbance, an in-stream UV-PAR profile and with a calculation using measured
irradiance at two discrete depths in a stream-side bucket. Data recorded by each
method is reported in Tables 5-8.
Bucket-depth interval calculation
The submersible UV-PAR radiometer was placed in a large bucket filled
with water from each stream. The radiometer measured irradiance at two depths
from the bucket surface. Attenuation coefficient for the depth interval was
calculated using:
ln~(
K __
d -
where Z is the depth interval.
;.-,;;;:-.:....J
z
~
is the irradiance at the shallower depth. and Ez is
the irradiance at the deeper depth.
41
The bucket method generally overestimates the attenuation coefficient
(Tables 1-4). This is likely due to a shadowing effect of the bucket walls. The
effect is more pronounced in the clearer systems (Monocacy, Saucon, Little
Lehigh and Switzer), a pattern consistent with expected behavior from a shadow
effect.
42
Table 5.305 run absorbance coefficients for each stream and method.
Kd 305
Kd 305
Kd 305
Stream
based on
based on best
based on 2nd
dissolved abs stream profile
streamprofile
Monocacy
2.4
3.1
Saucon
6.1
6.6
6.6
Little Lehigh
6.1
5.8
5.1
Switzer
7.7
8.5
8.8
Sand Spring
12.8
10.8
11.9
Choke
19.0
21.9
17.5
Ash
24.6
24.4
24.6
Table 6. 320 run absorbance coefficients for each stream and method.
Kd 320
Kd 320
Kd 320
Stream
based on
based on best
based on 2nd
dissolved abs stream profile
stream profile
Monocacy
2.1
1.0
Saucon
4.6
4.9
4.9
Little Lehigh
4.6
5.0
4.2
Switzer
6.3
7.6
7.7
Sand Spring
8.3
10.5
9.8
Choke
17.8
18.5
14.7
Ash
19.3
19.6
21.3
Table 7. 380 nm absorbance coefficients for each stream and method.
Kd 380
Kd 380
Kd 380
Stream
based on
based on best
based on 2nd
dissolved abs stream profile
stream profile
Monocacy
0.7
0.8
Saucon
2.4
1.8
2.3
Little Lehigh
1.8
2.7
1.8
Switzer
2.5
2.3
2.9
Sand Spring
3.5
5.0
4.7
Choke
6.0
7.6
10.6
Ash
8.0
9.0
8.9
Kd 305
based on
bucket interval
3.1
8.6
9.2
11.8
12.5
20.4
25.9
Kd 320
based on
bucket interval
2.5
6.9
7.4
7.8
10.0
16.6
21.3
Kd 380
based on
bucket interval
0.9
3.2
4.9
3.8
4.2
7.3
9.9
T abl e 8 PAR wave engths absorbance coe ffi'
IClents ~or cac h Strcam an d met hod
Kd pAR
Kd pAR
Kd pAR
i'd . "
:',~';cd ('11
Stream
based on best
based on 2nd
based on
di~~~·~cl\'t:d ~lh~;
stream profile
stream profile
bucket interval
Monocacy
1.5
3.7
Saucon
"
0.5
0.6
0.1
.. \
Little Lehigh
0.4
2.8
0.3
..
Switzer
0.4
0.9
0.7
"
Sand Spring
0.9
0.6
0.8
Choke
1.3
4.4
1.3
Ash
1.6
1.4
1.6
I'.
43
ApPENDIX II: PHYSICAL STREAM CHARACTERISTICS
Sites were characterized by data collected at three times during the
summer of 2003. Values collected on multiple days were reported in the paper as
the average of the three samples. Individual values are reported in Tables 9-15.
Table 9
Monocacy
Sampling Date
18-Jun-03
18-Jul-03
1G-Sep-03
dlssabs
a320
stream prof
Kd 320
rOOC]
temp
DO
--
---
---
.-
-.
--
..
2
2.08 0.98 (R =0.62)
1.24
17.2
---
pH
7.49
---
Table 10
Sampling Date
18-Jun-03
18-Jul-03
1G-Sep-03
dlss abs
a320
6.00
4.58
I
Saucon
stream prof
Kd 320
.--
rOOC]
1.49
1.21
2
3.92 4.93 (R =0.93)
1.43
temp
18.75
19.10
18.60
DO
7.42
---
pH
7.77
-.-
Table 11.
Sampling Date
18-Jun-03
18-Jul-03
1G-Sep-03
dlss abs
a320
6.53
4.57
I
Little Lehigh
stream prof
Kd 320
..
--
[DOC]
1.44
1.11
2
5.63 5.00 (R =O.90)
1.68
temp
19.02
19.30
18.80
DO
7.81
.-
--
pH
7.41
_.
_.
Table 12
Switzer
Sampling Date
18-Jun-03
18-Jul-03
1G-Sep-03
Table 13.
dlss abs
a320
6.51
6.34
I stream
prof
Kd
...
2
320
6.91 7.69 (R =O.97)
[DOC]
1.40
1.55
2.02
temp
20.97
21.30
19.40
DO
7.39
_.
--
pH
7.0E
..
--
Sand S)ring
Sampling Date
18-Jun-03
18-Jul-03
1O-Sep-03
dlss abs
a320
11.18
8.39
I stream prof
Kd 320
---
rOOC]
1.84
1.41
2
6.64 10.45 (R =0.98)
1.45
temp
14.90
15.30
14.50
DO
9.74
--
--
pH
5.61
---
Table 14.
Choke
Sampling Date
18-Jun-03
18-Jul-03
1O-Sep-03
dlss abs
a320
23.30
14.90
I stream
prof
Kd
---
320
2
15.00 18.54 (R =0.98)
rOOC]
3.17
2.12
2.87
temp
15.18
16.70
16.40
DO
9.38
--
--
pH
---
4.35
Table 15.
Ash
Sampling Date
18-Jun-03
18-Jul-03
1o-Sep-03
dlss abs
a320
24.38
19.40
I stream
prof
Kd
---
320
2
18.77 24.4 (R =0.95)
45
[DOC]
3.13
2.36
3.17
temp
15.54
15.70
15.90
DO
8.58
---
pH
6.56
---
ApPENDIX III: PERCENT CANOPY COVER
Leaf Area Index is used as an estimate of percent canopy cover and was
measured with a l80-degree image captured with a CI-110 Digital Plant Canopy
Imager. Measurements were taken at the site of collection, 10 m upstream and 20
meters upstream of the collection site. The average percent canopy cover of the
three locations is reported (Table 16). This method is not meant to fully
characterize the canopy cover; the heterogeneity of the study streams and an
inadequate amount of time prevented the canopy from being fully characterized.
46
ApPENDIX IV:
UV TOLERANCE OF OTHER STREAM BENTillC INVERTEBRATES
Experiments using the phototron were conducted during the summers of
2002 and 2003 to provide preliminary evidence of UV-sensitivity of a variety of
benthic stream invertebrates.
Data for a caddisfly (genus: Hydropsyche), a waterpenny (family:
Psephenidae) and a chironomid (order: chironomidae) were obtained through
phototron experiments according to the protocol outlined in the Methods section
above. LE50 (when available) and endpoint phototron data are shown below.
Other organisms were tested with only 10-20 individuals, and therefore data are
not statistically viable.
In the planaria experiment, 3 organisms were placed in each of three
dishes and were exposed to 0, 31, and 40 kJ/m2 of UV-B radiation in the presence
of PRR. A 12-hour exposure resulted in 100% mortality of the planaria in both the
31 and 49 kJ/m2 treatments, with 100% surviving in the controls.
One stonefly (Plecopteran) was placed in each dish. Five replicate dishes
were exposed to each of five UV-B treatments between 28 and 102 kJ/m 2, all in
the presence of PRR, plus a dark control group. A 12-hour exposure resulted in a
100% survivorship in every treatment.
T :lhI e 17 LE50 o f :l dd"·
IlIOn:! orgamsms lesl cd wlI. h Piholotron.
Organism (OrderlFamily/Genus)
Planaria
Chironomidae
TrichopteralHydropsychidacIHydropsYche
ColcoptcralPscphenidae
PIccoptcra
47
LE50 (+PRR treatement)
(k.J/m2)
<31
40
55
>102
>102
Figure 10. Endpoint Phototron data for Hydropsyche preliminary experiment.
Percent survival vs. exposure
Hydropsyche
100 - - . - - - - - - - - - - - - - - - - - ,
CO
80
+-------------j
.~
60
-4-----.1.------------1
~
40
-t-----~--------j
cfl.
20
-t-------1
o
-t----..,---.,....-----r---,.....----i
o
25
50
75
100
125
Exposure Level (kJ/m2)
Figure 11. Endpoint phototron data for Psephenidae experiment
Percent survival vs exposure
Coleoptera:Psephenidae
100
.->
80
60
~
40
'#.
20
CO
~
o
-.
~
I
o
I
I
I
25
50
75
100
Exposure level (kJ/m2)
48
125
Figure 12. Endpoint phototron data for Chironornidae experiment.
-co
.-E:::>
:::J
en
~
0
Percent survival vs exposure
Chironomidae
100
80
~
..
60
40
20
0
0
~
,-
•
PRR+
- - - PRR-
I
I
I
I
25
50
75
100
Exposure level (kJ/m2)
49
125
ApPENDIX V: DNA DOSIMETER DATA
Direct damage to DNA from UV-B radiation usually occurs in the
formation of DNA dimers, which can create biological damage as serious as cell
death. Dimers are created with a link forms between adjacent pyrimidine
nucleotide bases. While two types of dimers can be formed, cyclobutane
pyrimidine dimers (CPDs) account for 80-90% of all dimers (Mitchell and Nairn
1989).
The maximum amount of DNA damage that UV-B could incur without the
presence of repair stratigies was tested for each of the study streams. The
dosimeters consisted of a clear vial containing a solution of DNA extracted from
salmon testes in a 1 x SCC buffered solution (10 x:SCC buffer: 44.5 g citric acid
trisodium salt and 90 g NaCL). Dosimeters were prepared and analyzed by Dr.
David Mitchell (University of Texas, M.D. Anderson Cancer Center, Smithville,
TX), according to a protocol developed by Dr. Wade Jeffery (University of West
Florida, Center of Environmental Diagnostics and Bioremediation). Two
dosimeters were placed approximately 15 cm below the stream surface in a pool
of each site after sunset on July 1,2003 and were collected after sunset on July 2,
2003. Depth was recorded at the times of placement and collection, and the
average depth is reported below. Samples were analyzed and the concentrations
of CPDs arc reported below.
In general. the number of CPDslmegabase decreases with increasing
attenuation coefficient. This experiment was designed to ensure that the amount
50
of UV-B radiation reaching a typical depth found in a riffle (15 cm) was enough
to incur DNA damage. However, the canopy and water interception layers filtered
a large proportion of harmful UV-B. A set of control dosimeters were placed on
the roof of Williams Hall for the same period of time and incurred 1293 and 1466
CPD/megabase with standard deviations of 54 and 90.9 respectively.
1 the attenuatIOn coe ffi'
Tbl18DNAd'
a e
OSlmeter data. Las t co umn d'lSpJays
lClent ~or companson.
Depth of
Kd320 based
dosimeter
on best
placement
Average
Standard
stream
(em)
profile
Site
CPD/megabase
Deviation
4.9
Saucon
14
32.6
3.7
41.6
8
5.0
Little Lehigh
1.2
13
34.7
Switzer
12
Sand Spring
14
Choke
Ash
13.5
15
30
28.8
28.9
40.2
40.2
22.9
28.5
20.5
15.5
3.6
2.4
0.7
8.3
11.6
2
8.9
1.3
4.7
7.6
10.5
18.5
19.6
Based on the number of CPDs/megabase, the DNA damage caused by UV
in the rooftop control groups was 33-90 times higher than the DNA damage in the
stream groups. Therefore, the environmental layers of interception, including
canopy cover and CDOM, reduced the amount of biologically damaging UV to 13% of full sunlight damage.
51
Laura J. Shirey
1132 Furnace Street
Hellertown, Pennsylvania 18055
610-838-1498
las8@lehigh.edu
Background:
Born in Clarion, Pennsylvania on May 10, 1980 to George P. and Josephine F. Shirey
Education:
•
•
Lehigh University, College of Arts and Sciences
Bethlehem, PA
June 2002-May 2004
Earth and Environmental Sciences, M.S.
"Mechanisms ofUV radiation tolerance displayed by benthic stream mayfly nymph"
Funding: EPA Grant, National Center for Environmental Research, STAR Program
Pennsylvania State University, Eberly College of Science
State College, PA
Major: Science, B.S.
1998-2002
Minor: English
Professional Experience:
•
Lehigh University, Research Assistant
2002-present
Conducted experiments relating to ultraviolet radiation and aquatic organisms
Performed lake, stream and wetland fieldwork
Processed water samples for optical and chemical properties and nutrient content
•
The Pennsylvania State University, Laboratory Assistant
Invertebrate Zoology Laboratory
Sorted and identified marine invertebrate samples from collection
•
The Pennsylvania State University, Teaching Assistant
Fall 2001
Biology 435, Aquatic Ecology
Assisted in creating and grading papers and exams
Delivered one lecture
Collaborated with professor to improve curriculum and classroom atmosphere
•
Bureau of Land Management, Eugene, Oregon
Summer 2001
Intern. Fisheries Department
Conducted stream inventories and executed spawning ground counts
Determined and identified fish populations by electroshocking and snorkeling
Sampled streams for macroinvertebrates
•
True Value Hardware. Sales Clerk
Spring 2002
1995-2000
Activities:
•
•
•
•
•
Clearview Elementary School. Voluntccr Educator for "Earth Day 2003"
June 2003
Taught students in grades K-2 basic principles of aquatic ecology
January 2000-May
Phi Sigma Pi Honor Fraternity
2002
Held executive position as initiate advisor
Regularly modified chapter bylaws
Spring 2001
Penn State Student Admissions Voluntccr
September 1999-May 2000
TIle Daily Collegian
General Assignment Reporter. Science and Research Beat
Summers 1998-1999
Continuing Education. Clarion University of Penns)-lvania.
Group leader of Thc.1tre Workshop for grades 1-3
52
END OF
TITLE