Seasonal temperature declines do not decrease periphytic surfactant biodegradation or increase algal species sensitivity

Chemosphere, Vol. 35, No. 5, pp. 1143-l 160, 1997 0 1997 Elsevier Science Ltd All rights reserved. Printed in Great Britain 00456535/97 $17.00+0.00

Pergamon

PII: SOO45-6535(97)00169-O

SEASONAL

TEMPERATURE

DECLINES

BIODEGRADATION

DO NOT DECREASE

OR INCREASE

David M. Lee*l, James B. Guckertl,

PERIPHYTIC

SURFACTANT

ALGAL SPECIES SENSITIVITY

Scott E. Belangerl

1The Procter & Gamble Company, Environmental

and Tom C.J. Feijtelz

Science Department,

Ivorydale Technical Center,

Cincinnati, Ohio 45127-1087 (USA) 2The Procter & Gamble Company, European Technical Center, Strombeek-Bever

(Belgium)

(Received in USA 27 January 1997; accepted 26 February 1997)

ABSTRACT The effects sensitivity

of seasonally are reviewed

temperatures

decreasing

on surfactant

studies conducted

ranged from 28 to 0°C over all studies and temperature

over the course of each individual with in-flowing dosed

river water temperature

from four stream mesocosm study.

Mesocosm

periphyton

biodegradation

over a 5-year period.

declines were approximately

were naturally colonized

for 8 to 11 weeks

with

ethoxysulfate

sampling period.

Mineralization

ug/L. @pb) quantities

(AES), C25Eg-alkyl of Cl2-AS

of the surfactants

ethoxylate

sulfate

heterotrophic

of AES increased

the highest

receiving

respiration.

decline. period.

between

surfactant

Mineralization Periphytic

concentration

of AE by periphyton

dose of AES and remained

during periods

dosed with final effluent increased

of seasonal

a positive temperature

slightly over the testing

algal taxonomy and biovolume were evaluated during the AES study. Overall, these tests

showed no increases in species sensitivity that there is no correlation mineralization

and mineralization

over the testing period.

between naturally decreasing

Taken collectively,

seasonal temperatures

these results indicate

and lower rates of surfactant

or increased species sensitivity by naturally acclimated periphyton.

0 1997 Elsevier Science Ltd Key words:

The

Mineralization

constant in streams receiving lower doses. All studies involving surfactant exposure demonstrated correlation

(Cl2-AS),

constant in the control streams.

results from the AE study occurred with an increase in periphyton in streams

Streams were

in the dosed streams generally increased

remained approximately

over the dosing period

9 to 14°C

(AE) or 0 to 13% final effluent during the

and AE by periphyton

over the dosing period while mineralization

Cl2-alkyl

Seasonal

on tile substrata

river water for a period of 3 to 8 weeks prior to the initiation of sampling.

C45E2.17S-alkyl

and algal

periphyton,

alkyl sulfate, alkyl ethoxysulfate,

sewage effluent, cold water, ecotoxicology 1143

alkyl ethoxylate, mesocosm,

artificial streams,

1144

1. INTRODUCTION Integration

of biodegradation

rates for chemicals discharged

sensitivity

to the chemical of concern are key components

materials that may be transported ability of environmental

to environmental

microorganisms

compound to laboratory-cultured

and evaluation

of species

of modem chemical risk assessments.

As such,

compartments

to biodegrade

and/or indigenous

into the environment are routinely

the compound

organisms.

studied with regard to the

and the relative

toxicity

of the

The objective of these tests is to accurately

predict the potential fate and effects of a compound on the aquatic environment. Conclusions

drawn from such environmental

uncertainty

testing data are often made with a degree of uncertainty.

is a result of the fact that the number of physical/chemical

variables

usually quite large and in constant flux [l].

Among these variables, differences

routinely

important

considered

Furthermore, be called

to play a particularly

the ability to extrapolate

into question

due to significant

seasonal

in temperature

role in xenobiotic-environment

laboratory, mesocosm

or field conclusions

differences

This

in the environment

is

have been

interactions

[2-71.

from region to region may

in mean and seasonal

environmental

temperatures. It has long been suspected activity, including

that seasonal

biodegradation.

decreases

in temperature

This temperature-activity

result in reduced

correlation

Q 10 principle, has been supported in a number of studies [4, 5, 8-lo]. been conducted

in the laboratory

and incubated

at temperatures

manipulations

in temperature

mineralization

and thymidine

information

regarding

the characteristics

where environmental different

samples are removed from particular

than those observed

in situ.

in stream seston [lo].

the effect of temperature

and susceptibilities

environments

Peters et al. have reported in significant

changes

that

in glucose

Thus, while these tests provide valuable

on a particular community,

of communities

based heavily on the

However, many of these studies have

as little as *5”C from in situ resulted incorporation

hypothesis,

levels of microbial

they may not accurately

that have naturally

acclimated

reflect

to changes

in

temperature. However,

a number of evaluations

automatically

decline with low or decreasing

that levels of glutamate Furthermore,

have shown that microbial activities,

uptake in Antarctic

has been shown to be especially this understanding

clear at the community

by demonstrating

Antarctic water temperature. water with temperatures biodegradation

resulting

that high levels of microbial

environments,

zones.

of unique adaptation

are not affected

the biodegradation

no correlation

by changes assemblages

While investigating between

to in

of crude oil in sea

of natural bacterial

in faster degradation.

in soils, Knaebel et al. [15] observed

and suggested

In man-made

production

down to 0°C but also showed the capability

ethoxylate

and degradation,

[l 11. This phenomenon

Siron et nl. [14] not only demonstrated

to the oil at these temperatures,

in temperate

isolated from these waters were

level [12]. Bolter and Dawson [13] contributed

that levels of secondary

acclimate

degradation.

to those observed

this work also observed that a number of bacterial organisms

uniquely adapted for growth and survival under cold conditions

do not

Mortia et al. [l l] have demonstrated

seasonal temperatures. waters are comparable

including biodegradation,

microbial

to

alkyl activity

activity may not be required for surfactant

Painter and King [ 161 showed that there was no difference

in floe

1145 formation

or growth when activated sludge is grown at 10 or 20°C.

that lowering

the temperature

(LAS) and alkyl ethoxylate porous pot activated

resulted

in only slightly decreased

(AE) biodegradation

[16].

Evaluating

sludge plants, Birch [17] observed from

9 to 15°C.

ranging

demonstrated

no decrease in linear nonionic surfactant biodegradation

sludge tests with temperatures determined

declining

bacterial

by temperature

community

time.

themselves

Tests conducted

in sediments

Diurnal temperature downstream characteristics temperature

by Kravetz

in continuous

with

et al. [18] who

flow-through

by other environmental

itself, many environmental

activated

factors and are not

variables change seasonally

[19, 201.

with the temperature-related at in situ temperatures

environmental

have suggested

to temperature-dependent

can also be very significant

with river continuum

theory.

parameters

conditions

abundance,

fluctuations

Collectively,

that exist at any

that seasonal temperature

and change predictably

measured or predicted during risk assessments and by other environmental

as a result

Thus, it is likely that the traits of a

role in changes in bacterial production,

as compared

variations

in accordance

in LAS or AE degradation

These data suggest that the levels of activity of

are influenced

with, natural shifts in temperature

may play a subordinate

consumption

sulfonate

of LAS and AE in

alone.

are tightly associated

particular

the biodegradation

were confirmed

from 25 to 8°C.

assemblages

In addition to the effects of temperature of, or in concurrence

results

this study also showed

levels of linear alkylbenzene

no difference

temperatures

natural and man-made

These

Furthermore,

shifts

biomass and oxygen

in organic

carbon

[20].

from river headwaters

these observations

to

suggest that the

are likely to be influenced by seasonal shifts in

that are themselves

altered by natural fluctuations

of

temperature. The following

reports four stream mesocosm

biodegradation

of surfactants

water was evaluated algal species determine

(2 anionic,

studies conducted over a live-year period.

1 nonionic)

by naturally acclimated

during periods of seasonal temperature

sensitivity

to surfactants

if seasonal decreases

was thoroughly

in temperature

declines.

examined.

In each study, the

periphyton

and source river

During the AES study, the level of The objective

of this analysis

result in decreases in surfactant biodegradation

was to

and increases

in algal toxicity.

2. MATERIALS 2.1 Biodegradation

AND METHODS studies - general

Surfactant biodegradation was measured water.

as the mineralization

Periphyton

was obtained

model stream ecosystem channels

studies were carried out from 1991 through of a l4C-labeled

1996. In all studies, biodegradation

tracer surfactant

by mesocosm

from the Procter and Gamble’s Experimental

facility located near Cincinnati,

Ohio, USA.

Briefly, the ESF consists

drawing source water from the Lower East Fork of the Little Miami River.

each channel was lined with terra cotta tile substrata (approximately the lower reaches were lined with trays containing long receiving

periphyton

Stream Facility

and river (ESF), a of eight

The upper reach of

8900 mm2 upper surface area), while

2 cm (average) diameter cobble. Each stream is 12-m

168 L/min and consist of 5 sections [21]: a headbox, a 5.5 m tile-lined reach, a 0.5 m flare, a

1146 5.5 m cobble reach and a 1 m tail pool.

The tile reach is an array of approximately

while the cobble reach is an array of 15 rows x 3 columns. of 3-8 weeks prior to sampling. quantities

of surfactant

characteristics).

All streams were subject to a colonization

At the end of the colonization

or effluent

Biodegradation

(“h) for a period

tests were performed

45 rows x 3 columns period

period, streams were dosed with ug/L

of .8-l 1 weeks

(see below

using tile periphyton

for individual

sampled

study

from the streams at

various times during the dosing period. 2.2 ESF operations

A detailed description

of the Experimental

Stream Facility (ESF), and its source of water, the Lower East

Fork of the Little Miami River, can be found in Belanger et al. [21]. With respect to the studies described here, the ESF channels received identical, untreated water from the Lower East Fork. After passing through a grate to remove large river debris, water from the Lower East Fork is not filtered or altered in any way prior to introduction

into the ESF.

seasonal changes, are maintained ESF is approximately

monitored

light intensity, photoperiod, influenced

between-stream

and air temperature

Natural and seasonal

changes

characteristics

monitors

for temperature,

A complete

description

considerations

were controlled and monitored to minimize system.

such as

between stream and temperature

ESF stream channels

and pH to verify source water

- 1991

to the study procedure

can be found in [22] with surrounding

dodecyl

sulfate) from August

19 to October

tiles were sampled at intervals corresponding

Periphyton

experimental

with approximately

design

= 0.867 cm2/mL).

Triplicate

random

to 0, 7, 14, 28,42 and 56 days after the initiation of Triplicate

and diluted with 0.2 urn filtered

aliquots of tile periphyton

were incubated

2.73 nCi of [ l-14C3 dodecyl sulfate (14C-C 12-AS, specific activity = 10 mCi/g) for 1 to

All incubations

were carried out at ambient

was determined

incubation vessel.

15, 1991 [23].

was scraped and brushed from the tiles, homogenized

control water (final concentration

mineralization

parameters

in [23], [24], [25], [26] and [27]. Briefly, streams were dosed with 0 to 1586 ug/L of Cl2-

alkyl sulfate (Cl2-AS,

6 hours.

[21]. Other environmental

oxygen, conductivity,

Water flow

within strict set points

in Lower East Fork stream water chemistry dissolved

including

time within the

for each stream [21].

2.3 C12-alkyl sulfate mineralization

dose.

variability

all ESF stream channels equally due to the ESF water distribution

have individual

periphyton

Water residence

for each stream channel, and rates were maintained

control to minimize

variability.

and river water characteristics,

the experiment.

4 min, resulting in minimal alterations of in situ river water temperature.

rate was automatically by computer

Thus, natural recruitment

in the facility throughout

by quantitating

Radioactivity

In addition to biodegradation C 12-AS on the mesocosm

was quantitated using liquid scintillation

determinations

community.

bacterial and algal periphyton

river water temperatures.

Radiolabeled

Cl2-AS

14C02 trapped by a KOH saturated wick placed inside the

[22], studies were conducted

counting. to evaluate the overall effect of

These studies evaluated the impact of Cl 2-AS on invertebrates

responses to C 12-AS [28], direct and indirect C 12-AS ecotoxicological

[27] and toxicity as assessed by community

analysis [24].

[26], effects

1147 2.4 ClqE3S-alkyl

ethoxysulfate

mineralization

- 1992

The mineralization

of the anionic surfactant,

14C-Cl4E3S-alkyl

similar procedures

from the CI2-AS

Streams were dosed with AES (average formula - C45E2.17S)

study.

ethoxysulfate

from August 24, 1992 through October 19, 1992. Experimental and [27].

In-stream

concentrations

and diluted as before.

60 pg/L of 14C-Cl4E3S procedure

described

Mineralization

(specific

above

activity

or by adding

aliquots

ESF periphyton

have been extensively

the 56-day exposure

to AES.

structure and function. was employed

studied with respect to algal taxonomy

Taxonomy

analyses were performed

(see [25] for complete

centric, naviculoid,

cymbelloid,

500 cells were enumerated Diatom population

using the

containing

acid.

density multiplied

etc.).

bibliography).

by the average volumetric

density alone [29].

Community

reported here, dominant

algal taxa were classified

(reviewed

unpublished

data from the Little Miami River).

species level), the taxon was excluded

“unclassitied”.

cell

as biovolume

which is the cell

during taxonomic

identifications.

of a population

to the community

present.

than cell

For the purposes

by known seasonal dominance

by [30, 311; supplemented

derived from

by [32-341 and Belanger

If seasonal or thermal preference

of the

and Lowe,

was not known (at the

from the analysis unless the genus as a whole had clear seasonal

Taxa were classified

any preference,

and

Supply, Ipswich, Great Britain).

are expressed

is the sum of all populations

of the literature

methods

counts from the Palmer-Maloney

size of the taxon determined

descriptions

tendencies.

abundances

the potential importance

biovolume

literature

of diatoms were noted (with diatoms being noted as

were calculated based on proportional

describes

and, where

Soft algae were counted using a Palmer-

Diatoms were acid cleaned using standard laboratory

Population

during

community

at the species level for diatoms

after mounting in Naphrax (Northern Biological

abundances

more accurately

and have used near identical

were sampled bi-weekly

browns, and reds). A broad use of current taxonomic

taxonomic

with corrected diatom identifications.

and remained

to vials

Five tiles were selected at random for purposes of investigating

Maloney cell (0.1 mL) volume in which the proportion

demonstrate

was determined

suspension

in [21] and [25]. Stream periphyton

possible, for soft algae (greens, cyanophytes,

preference

Mineralization

of incubated

scraped

algal taxonomy - 1992

methods from 1989-1996 as described

evaluation

tiles were sampled,

incubated with approximately

was then calculated by subtraction.

2.5 Cl4E;1S-alkyl ethoxysulfate

Biovohnne

Randomized

were then individually

= 14.0 mCi/g).

using

details of the dosing can be found in [24]

ranged from 0 to 774 ug/L.

Aliquots of diluted periphyton

(AES), was determined

as spring, summer, fall, or winter species.

it was classified as without seasonal preference. Dominance

was inferred if a population

If a taxon did not

Finally, some taxa lacked data

was >5% of the total biovolume

in

any stream on any week during the study.

2.6 C14E3-alkyl ethoxylate mineralization ESF streams November

were dosed

- I994

with 0 to 760 pg/L of C25E6-alkyl

ethoxylate

1, 1994. Tiles were sampled during the 56-day dosing period.

sealed in foil-lined, 400 mL of respective

heat sealable bags (Kapak Products, Minneapolis,

from September

6 through

Tiles with intact periphyton

Minnesota

were

USA) with approximately

stream water and tracer amounts (0.72-7.20 nCi/mL, specific activity = 14.0 mCi/g) of

1148 14C-Cl4E3

AE.

Foil-lined

and prevent gas-exchange.

bags were used as they exclude light (preventing Incubations

that received source water identical to that sent to the streams. of water were removed from the bags to vials containing the radiolabeled

Periphyton

AE was determined

by difference

by placing intact periphyton

At the end of the incubation

of the radioactivity

Winkler titrations

changes in heterotrophic

on tiles plus approximately

before and after incubation

period, aliquots Mineralization

of

remaining in the base and acid vials.

evaluated

respiration.

Periphyton

400 mL of stream water into heat-

sealable bags. The bags were then incubated overnight at in situ temperatures water bath.

in water tables at the ESF

25% H2SO4 or 0.5 M NaOH.

from this study were also used to determine

was evaluated

algal 14C02 incorporation)

were carried out at ambient temperatures

using a continuous-flow

river

the amount of oxygen used by the

heterotrophs.

2.7 Cl.+E3-alkyl ethoxylate study - 1995-96 ESF streams were colonized filtration)

for 8 weeks with combinations

from the Clermont

Co. Lower East Fork Wastewater

effluent were 0, 5 and 13% effluent. C25E6-AE

(nominal

biodegradation respective

After the colonization

concentrations)

from November

Treatment

Plant.

Final concentrations

of

period, streams were dosed with 0 or 37 ug/L

14, 1995 through

January

9, 1996.

For the

study, random tiles were sampled during the dosing period and incubated with 1500 mL of

stream water and approximately

were taken and tested for biodegradation at approximate aeration.

of river water and final effluent (prior to sand

river water temperature

Mineralization

0.72 nCi/mL of 14C-Cl4E3

AE.

21 days after the cessation of dosing.

was determined

in heat-sealable by quantifying

bags attached

An additional

set of samples

Incubations

were carried out

to a recirculating

chamber

with

the amount of 14C02 retained in two KOH bubble

traps. 2.8 Statistical Analysis

Statistical

analysis

for all measured

analysis of variance (ANOVA) responses

of stream periphyton.

discriminate asterisked

which individual (*) in the figures.

endpoints

were based on untransformed

data.

One-way

parametric

with surfactant exposure level as the treatment variable was used to assess A Least Significant treatments Significance

differed.

Differences

multiple

comparison

test was used to

Algal groups which were significantly

was inferred for all statistical tests at CL= 0.05.

different

are

All data was

analyzed using [35] or [36].

3. RESULTS

AND DISCUSSION

3.1 Seasonal changes in river water temperatures Figure 1 depicts the combined watershed

water temperature

generally begin steadily decreasing

mid-December.

data over the four studies discussed.

about the beginning

The average decrease in temperature

of September

Temperatures

in this

and continue to drop until

over the 1991- 1994 study periods was 12.2”C with an

1149 average final temperature temperature

of 125°C.

The 1995-96 AE study was conducted

had a colder initial value (-1 O’C) and dropped approximately

in the winter and river water

9°C before reaching near freezing

by the middle of the study. These temperature were observed

shifts from the fall to winter seasons in the Lower East Fork of the Little Miami River

to follow similar patterns of decline from 1991-94.

Temperature

1995-96 study indicates that the trend continues to result in water temperatures of the year.

Despite the similarity

marked by increases changing

in trend, each year demonstrates

and decreases

temperature

(decreasing

independent

that are unique to that particular in particular)

data resulting

year.

from the

near freezing prior to the end changes

in temperature

Thus, any effects of rapidly

should be clearly evident in the results of the endpoints

measured. 3.2 ClTalkyl

sulfate mineralization

The mineralization

data from the 1991 C12-AS study can be found in Figure 2.

included for all mineralization

data points to indicate standard deviations.

stream data points are quite small. Rates of CL2-AS mineralization significantly

Error bars have been

Standard deviations

of control

from control stream periphyton

were not

different at the end of the dosing period as compared to those observed at the beginning

study.

The rates of CL2-AS mineralization

study.

Spearman

rank correlation

of the

increased in all of the dosed streams during the course of the

coefficients

increase in overall turnover rates (mineralization

(based on untransformed and assimilated

dose (pcO.05, data not shown) [22]. There were no overall decreases of the streams over the dosing period and corresponding

data) also demonstrated

radiolabel)

was positively

in the levels of mineralization

river water seasonal temperature

that the

correlated

decline.

with in any

Details

are available in [22]. Previous studies have shown CL2-AS to have typically faster rates of mineralization As such, C 12-AS mineralization of mineralization

than AES or AE [37].

had the greatest potential for decrease with temperature.

In fact, a leveling

rates was observed in streams dosed with > 224 pg C12-AS/L between Days 256 through

270 during a period of particularly increases in mineralization AS mineralization

rapid temperature

decline (Fig 2). Nevertheless,

rates from Days 270 to 284, despite further temperature

all streams demonstrated decline.

data agrees with the results of Anderson et al. [38] and Zakova et al. [39], who independently C 12-AS degradation months.

Rates of CL2-

increased 0 to 4 times over the dosing period, despite a 14°C drop in temperature.

Interestingly,

by periphyton

This

reported that

in polluted sites generally remains the same during summer and winter

the ability of periphyton to rapidly degrade C 12-AS over seasonal ranges of

11.50

26 26 24 s 22 0, E z ;;i ;

20 16 16

g f

14 12

5

P

10

0 160 210 240 270 300 330 360

25

230

55

240

DayofYear

Figure 1. Seusonal temperature declines

is maintained

strains in periphyton degradation

observations,

that have the ability to produce

degradation

occurring

with the data presented

in periods of cold and decreasing

seasonal variations in the environment

3.3 Alkyl ethoxysulfate The mineralization

290

of CIJ-ulkyl

sulfate

in the number of bacterial

enzymes

of alkylsulfatases

responsible

oxygen) rather than temperature here, strongly temperatures

suggest

for Cl2-AS

was dependent

on water

specifically

[40].

that the rapid Cl2-AS

is the result of natural acclimation

to

mineralization

of radiolabeled

initiation of dose throughout

AES by mesocosm

the dosing period.

periphyton

the approximate

is depicted in Figure 3. Periphyton levels of mineralization

This level of mineralization

from the 774 ug AES/L from Day 236 through Day 263.

increased in a linear fashion through Day 291 to represent approximately incubation period.

260

and is not dependent on temperature.

the control and 13 ug AES/L streams maintained periphyton

alkylsulfatases,

that the production

oxygen demand and dissolved

combined

270

during the 1 Y91 mesocosm study.

during the winter months when there are decreases

[40]. Anderson et al. determined

quality factors (biological These

260 ofYear

Figure 2. Mineralization

during the 1991-96 mesocosm experiments temperature

250 Day

observed

from at the

was also observed in tests with The level of mineralization 75% mineralization

then

over a 2 day

1151 28

28

T

26

26

24 22

0 0

13CgAE.sIL ITlIlQAESlL

s 0,

20

f

18

t;i &

16 14

ig

,020 0251P

4

k

12

12

10 230

240

250

260 Day

270

Figure 3. Mineralization ethoxysulfate

280

290

300

240

250

260

ofYear

270 Day

of ClqE#-alkyl

Figure 4. Mineralization

during the 1992 mesocosm

280

290

300

310

ofYear

of C14E3-alkyl

ethoxysulfate during the 1994 mesocosm study

study. Temperatures

declined consistently

during the 1992 AES study from a high of 25°C to a low of about 13°C

by the eighth week of dosing (Fig 3).

While levels of mineralization

control and low dose streams, the dramatic

increase in the mineralization

stream after Day 263 (Fig 3) is likely due to a biological acclimation with an enhanced

ability to mineralize

AES.

remained

relatively

rate observed

temperatures

did not impact the

process or the resulting rates of AES mineralization.

water [42] and river water [37].

of AES is rapid in tests using periphyton

This study confirms

these results and demonstrates

maintains the ability to rapidly degrade AES during periods of decreasing

three surfactants with the greatest ramifications

Due to its apparent greater structural complexity,

potential

of decreasing

or increased.

correlations

[41], estuarine

that the periphyton temperatures.

Of the

tested, AES contains the largest number of different functional groups (alkyl chain, ethoxy

groups, sulfate group).

constant

in the high dose

While it is not known if constant or increasing

Previous studies have shown that the biodegradation community

in the

to AES which provide the community

would have affected the duration of the lag period, it appears that decreasing temperature acclimation

constant

to be negatively temperature.

These results

impacted

in terms

AES may represent the compound

of biodegradation

by thermodynamic

During the course of this study, biodegradation support the hypothesis

that laboratory-temperature

(or Q LO) may not represent actual processes and rates of metabolism

either remained biodegradation

in the environment.

3.4 Alkyl ethoxylate mineralization Figure 4 shows the results of the biodegradation mineralization

experiments

during the 1994 AE study.

levels ranged from 1O-l 5% at Day 245 to 1520%

within the control

streams

increased mineralization

increased

gradually

over the dosing period with the exception

at Day 286. Levels of mineralization

Control stream

at Day 300. The levels of mineralization of a spike of

remained similar between the control streams

1152

30 26 26

240

250

260

270

260

290

300

z

310

5 &

Day of Year

0

0

300

340

320

P

35

15

Day of Year

Figure 6. Mineralization

Figure 5. Periphyton heterotrophic

360

of ClqEj-alkyl

ethoxylate during the 1995-96 mesocosm study

respiration during the 1994 Cl4E3alkyl ethoxylate mesocosm study. throughout

the study.

all concentrations dosed

stream

subsequent

performed

decrease

higher than expected during

the

Day

approximately

Among the dosed streams, rates of mineralization

increased over the dosing period in

except the 36 pg AE/L dosed stream, which showed a slight decrease. similarly

to the control

in mineralization

286 sampling

in demonstrating

a substantial

rates between Days 272 and 300 (Fig 4).

levels of mineralization

those observed

streams

observed

has not yet been at the beginning

The 36 ug AE/L increase

and

While the reason for the

in the control streams and the 13 pg AE/L stream determined,

levels

of the dosing period,

of mineralization

returned

when the temperature

to

was 10°C

warmer. 3.5 Periphytic heterotrophic Periphyton

heterotrophic

respiration

respiration,

a more general measure of heterotrophic

endpoint evaluated during the 1994 AE study (Fig 5). All streams demonstrated respiration

during the dosing period.

Heterotrophic

respiration

stream, which demonstrated

at Day 300. Periphyton

increase

in periphytic

temperature acclimated

decreases

slightly increased

mesocosm

levels of respiration

respiration

periphyton.

from Days 272-300.

These levels of

decline of approximately

14’C.

in all streams but the 36 ug AE/L stream and the overall in all streams across the dosing period, the data indicate that

from 25 to 11“C do not result in lower

and Cl2E9 alkyl ethoxylates studies evaluated

in mineralization

bacterial

from all streams

compared to the control streams with the exception of the 760 ug AE/L

respiration were observed during a seasonal river water temperature Given the overall increase

an increase in the level of

generally increased in all streams from Day

245 through Day 286, followed by a slight decrease in respiration showed similar levels of respiration

activity, was an additional

Furthermore,

levels

of AE biodegradation

these results support the efficient

by naturally

degradation

of CL6E9

observed by Vashon and Schwab [42] as well as Larson and Games [3]. These

biodegradation

in estuarine water [42] and river water [3]. Importantly,

the latter study

1153 demonstrated

rapid biodegradation

not been acclimated

of AE over a range of temperatures

to the incubation temperatures

3.6 AK-y1 ethoxylate mineralization The 1995-96 AE mineralization over an 11-week throughout

period

at temperatures less than 1OT

study investigated

(Fig 6).

concentrations.

AE biodegradation

Temperatures

the end of the experiment.

AE and 0 to 13% effluent,

(3-34°C) by river water which had

[3].

were generally

Among periphyton

there was little variation

Levels of mineralization

increased

at very cold temperatures

WC

samples tested from streams containing

in the amount of AE mineralization

substantially

effect on AE mineralization

maintaining

temperatures.

study) indicating biodegradative

This data indicates that this phenomenon

acclimation

of the periphyton

data from the experiments

is not a requirement

for

conducted from 1991 through 1994, it is evident

of surfactant increases when the commuuity

previously

is not

on seasonal surfactant biodegradation

surfactant (Figs 2, 3 and 4). Bacterial acclimation

is exposed to higher concentrations

and the resulting faster rates of biodegradation

[37]. This study demonstrates

periods of declining seasonal temperatures

that acclimation to Cl2-AS,

of

have been

AES and AE during

is dynamic and results in an enhanced ability of the periphytic

communities

to mineralize these surfactants.

communities

in the environment

rates of degradation

data).

capacity during low and decreasing seasonal temperatures.

Evaluating the mineralization

documented

over the testing period (Fig 6).

These data also support previous control stream data (1994 AE

that substrate

3.7 Effect of surfactant concentration

that the mineralization

slightly at the

that additions of up to 13% effluent do not have a detectable

(D.M. Lee, unpublished

affected by low and decreasing mineralization

observations

0 ug/L

across effluent

by Day 332 and decreased

January 8 and January 30, 1996 samplings for a net increase in mineralization These results confirm previous

(9 to O’C)

from the fourth week of testing

These mesocosm

studies also suggest that bacterial

will respond to higher concentrations

of these surfactants resulting in faster

during periods of decreasing seasonal temperatures.

3.8 Summary of seasonal temperature effects on surfactant biodegradation

Taken collectively, periphyton declining

these data indicate

that has been naturally levels of biodegradation

lowered (not acclimated

observed

conservative

rates calculated

in laboratory

reality.

of nitrilotriacetate

solely on a thermodynamic

experiments

degradation Furthermore,

and in which microorganisms using non-acclimated

under in situ conditions basis.

This hypothesis

(NTA, a common laundry builder) concentrations

does not decrease

in

these data show that

in which temperature

This had been hypothesized

from experiments

and that acclimated microorganisms

would be predicted

of surfactant

to lower temperatures.

to lower temperatures)

systems may not reflect environmental that biodegradation

that the extent

acclimated

is artificially

are trapped in closed batch

by Larson [43], who cautioned microorganisms

were likely

may degrade substrates faster than was supported by an extended study

in Canadian water over a

1154

DominantAlgalTaxa

-

le+4

-I

220 230 240 250 260 270 280 290 300 >I"

220 230 240 250 260 270 260 290 300 310

Day of Year

Day of Year

Figure 7. Total algal community hiovolume (A) and percent contribution

of dominant taxa to community

biovolume (B) during the 1992 AES experiment. 4-year

period

[44].

demonstrated temperatures

periods

of constant

consumer

use and discharge,

the Canadian

study

in the levels of NTA from summer to winter months in surface waters when

dropped to 0°C [43, 441. These results. combined with the observations

that any decrease minimally

During

no increases

in biodegradation

caused by thermodynamic

offset by increases in biodegradation

ramifications

ability within the community

of this study, indicate

of decreased

temperature

are

as it changes and responds to

seasonal trends. 3.9 Algal species sensitivity Algal community

biovolume

increased approximately

IO-fold during the AES experiment

in all treatments

(Figure 7A). However, the highest exposure (774 c(g AESIL), and to a lesser and non-significant second highest exposure (25 1 ug AESIL) increased jn biovolume the study. This pattern is consistent

with other microbial periphyton endpoints

heterotrophic

adaptation to AES at high concentrations

microbial community

155 algal taxa were considered community

The exception

dominant at some point in the study. Figure 7B depicts the percentage

of the

of “dominant” taxa. The 24 dominant taxa were usually 95% or greater of was the high exposure (774 ug/L) stream which had a significantly present.

stream (see also [24]). By the conclusion

not described

were classified (Figure 8A).

This indicates the presence

A substantial

percentage

lower

of several new taxa unique to this

of the study there were no exposure-dependent

as spring seasonal dominants

or graphed any further.

seasonal preference

[24] and perhaps is related to 24 of

of the 24 dominants

Few taxa (
of

(Fig. 3). Approximately

which was comprised

the community. percentage

extent the

at a greater rate during the mid-portion

based on the periphyton

responses

noted.

literature and are

(20-40%) of taxa were found to have little

Many of these taxa would be considered

ubiquitous.

cosmopolitan

taxa

1155

100

100

ii 90 2

E 90

2 g

g

60

.;

70

$

70

z

60

z s

60

a ii z c z

40

5 t%

40

30

E

20

'E

20

i? ; P

10

Q $) n.

10

60

SummerAlgal Taxa

60

p0

0 220 230 240 260 260 270 260 290 300 310 Day

30

0 220 230 240 260 260 270 260 290 300 310

ofYear

Day

ofYear

100 fi

90

5

60

I

;

70

P =

60

FallAlgalTaxa

p0 s Ib

40

E 8 ; P

20

30

10 0 220 230 240 260 260 270 260 290 300 310

220 230 240 260 260 270 260 290 300 310 Day

Figure

8.

Day

ofYear

ofYear

Percent contribution of taxa without seasonal thermal preference

(A), summer seasonal

preference (B), fall seasonal preference (C) and winter seasonal preference (0). which are good colonizers

[29, 311.

enhanced at the highest concentration seen in Fig. 7A. pattern.

The proportional

The percentage

Fall seasonal taxa showed the inverse relationship

portion of the study.

Importantly,

for any seasonal group. more or less sensitive sensitive.

for the overall increase in community

was

biovolume

summer and winter taxa (Fig. 8B, SD) showed no exposure-response

(Fig. 8C) with the high exposure concentration

uniquely

of these taxa as part of the total community

and are responsible

to that of the taxa without seasonal preference

being reduced compared to other treatments

there is no clear dose-response

during the mid-

pattern that persists to the end of the study

This suggests that no one group, adapted to either warmer or colder temperatures than any other group.

Cold-adapted

Algal species are largely cosmopolitan

is

algal species by this analysis appear to not be and generally circumpolar

in distribution

[45]

1156

and many of the same or highly related taxa would be expected throughout

to exist in similar habitats

elsewhere

the world.

4. CONCLUSIONS In conclusion, maintained decreases

the mineralization

and often increased in temperature

species composition tested artificial therefore,

which occur seasonally.

temperature

in enclosed

changes

batch

winter seasons and in geographies these results

support

for macroflora

along with natural changes

which isolated These

in

studies which have

However, these laboratory

recruitment.

such

These conclusions

the naturally results

studies

occurring

presented

here,

AES and AE in temperate zones during the fall and

with extended periods of low mean river water temperatures. of biodegradation

Similar investigations

was at least

Furthermore,

differ from laboratory

correlated.

natural

safety of Cl2-AS,

the extrapolation

seasons and geographies.

preventing

in temperature.

fluctuations

and used testing procedures

systems,

support the environmental

are positively

periphyton

to the surfactant AES.

These conclusions

and biodegradation

acclimated

seasonal decreases

which undergo natural temperature

that temperature

community

during significant

by naturally

do not increase algal species sensitivity

are based on communities concluded

of three surfactants

and species

of temperature-related

and fauna which are more limited in their phenotypic

sensitivity

In addition,

for surfactants

species sensitivity

across

are likely needed

and genetic plasticity

than microbial

organisms.

ACKNOWLEDGMENTS The authors thank John Bowling, Burton Hamm, Daniel Davidson, Ellen LaBlanc, Rick Bausch, Ken Rupe, Dave Walker, Cheryl Tansky, Timothy Gsell and Roy Ventullo for their technical assistance. are grateful for the efforts of Rex Lowe (algal taxonomy) (biodegradation

The authors

as well as Robert Larson and Thomas

Federle

discussions).

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