**Row Crop Herbicide Drift Effects on Water Bodies and Aquaculture**

Peter Wesley Perschbacher1, Regina Edziyie1 and Gerald M. Ludwig2 *1University of Arkansas at Pine Bluff, Center for Aquaculture/Fisheries 2H.K.D. Stuttgart National Aquaculture Research Center United States of America* 

#### **1. Introduction**

190 Herbicides – Properties, Synthesis and Control of Weeds

Toor, A.P.; Verma, A.; Jotshi, C.K.; Bajpai, P.K. & Singh, V. (2006). Photocatalytic

Vione, D.; Minero, C.; Maurino, V.; Carlotti, M.E.; Picatonotto, T. & Pelizzetti, E. (2005).

Wei, Y.-H. & Lee, H.-C. (2002). Oxidative Stress, Mitochondrial DNA Mutation, and

Wong, C.C. & Chu, W. (2003). The Direct Photolysis and Photocatalytic Degradation of

Vol.227, No.9, (October 2002), pp. 671–682, ISSN 00379727

2004), pp. 125–133, ISSN 09263373

(June 2005), pp. 79–88, ISSN 09263373

2003), pp. 981–987, ISSN 00456535

Degradation of Direct Yellow 12 Dye Using UV/TiO2 in a Shallow Pond Slurry Reactor. *Dye and Pigments*, Vol.68, No.1, (January 2006), pp. 53–60, ISSN 01437208 Topalov, A.S.; Šojić, D.V.; Molnár-Gábor, D.A.; Abramović, B.F. & Čomor, M.J. (2004).

Photocatalytic Activity of Synthesized Nanosized TiO2 towards the Degradation of Herbicide Mecoprop. *Applied Catalysis B: Environmental*, Vol.54, No.2, (December

Degradation of Phenol and Benzoic Acid in the Presence of TiO2–based Heterogeneous Photocatalyst. *Applied Catalysis B: Environmental*, Vol.58, No.1–2,

Impairment of Antioxidant Enzymes in Aging. *Experimental Biology and Medicine*,

Alachlor at Different TiO2 and UV Sources. *Chemosphere*, Vol.50, No.8, (March

Aquatic ecosystems produce substantial amounts of aquatic products; including all new sources of seafood, from aquaculture. Level land with clay soils and the availability of water supplies makes riverine alluvial plains favorable areas for row crops and aquaculture. Aquaculture ponds are susceptible to impacts from row crop production through drift of herbicides. To assess these impacts we have conducted field research in replicated mesocosms filled with water and associated naturally-occurring communities from various pond ecosystems and subjected to expected levels of drift from all major aerially-applied herbicides currently in use. Rather than an organismal approach and LC50's, data indicates community-level approaches better approximate ecosystem impacts. Herbicide drift that affects phytoplankton adversely or in a stimulatory manner will similarly impact the ecosystem, as phytoplankton produce oxygen, take up ammonia and nitrite and provide food for zooplankton. Drift levels are below toxic levels to most other aquatic organisms, including fish (Spradley, 1991). Drift amounts reaching water bodies and ponds, including fish ponds, depend on many factors, but the cumulative range is most affected by the size of the water body. Thus, other than in direct overflight, larger catfish ponds (6-8 ha) have a drift range of 1-10% and smaller more recent designs of 4 ha, 5-20%. Even smaller ponds, used for fingerling production and baitfish production (0.8-2 ha), may receive drift amounts of up to 30% of the field rate.Herbicide drift may be expected to impact small water bodies through death or reduction in the photosynthetic rats of phytoplankton, which could reduce the supply of dissolved oxygen, inhibit removal of toxic nitrogenous wastes, and reduce production of zooplankton by reducing their food supply. These conditions could also result in death, disease, or lower growth rates of managed or cultured fishes. Triazine herbicides (atrazine and simazine), as well as amides (propanil), phenylureas (diuron), triazones, uraciles and phenolics, act through inhibition of photosystem II (PSII) of photosynthesis (Cobb, 1992). They are widely used in agriculture, since they provide a low-cost basal weed control (Jay et al., 1997). Using mesocosms and naturally-occurring plankton communities in a multi-day study provides better extrapolations to real environments than laboratory studies on a single species (Juettner et al., 1995), and possibly prevent overestimate of impacts (Macinnis-Ng and Ralph, 2002). The major drift source is aerial application, with an

Row Crop Herbicide Drift Effects on Water Bodies and Aquaculture 193

et al., 1995) and most critical to fish culture. Water temperature, dissolved oxygen and pH were measured with a multiprobe meter (OI Analytical, College Station, TX). Total ammonia nitrogen (TAN) and nitrite-nitrogen were measured by Nessler and diazotization methods (Hach Co., Loveland, CO), respectively. Unionized ammonia (UIA) levels were calculated from measured temperature, TAN and pH. Chlorophyll *a,* corrected for pheophytin *a,* and a 2-h light and dark bottle estimation of phytoplankton net primary productivity (NPP) by the oxygen method followed APHA (2005), except for use of ethanol as the solvent for chlorophyll (Nusch, 1980). Major zooplankton group concentrations were also determined in each replicate in the following manner. Three, 1-l samples were obtained with a tube sampler that encompassed the entire water column. The samples were concentrated by being strained through a 70-um Wisconsin plankton net and then preserved in 70% isopropyl alcohol. Samples were identified and quantified by using a Sedgwick-Rafter cell and a microscope (Ludwig, 1993). Statistical analysis was by SAS statistical software package. ANOVA (after pretesting for normality) and LSD were used to test for significant

Atrazine lowered NPP on d 2; and effects on ecosystems from field studies have been summarized as short-lived, with quick recovery at concentrations less than 50 ug/l (Solomon et al., 1996). Solomon et al. (1996) observed stimulation of chlorophyll *a* on d 7 post-application of 50 ug/L atrazine. This was also found by us at d 7 with propanil (Perschbacher et al. 1997, 2002). Edziyie (2004) noted drift from propanil affected fry ponds with <10 ug/l chlorophyll *a* less than culture ponds with levels of 50-85 ug/l of chlorophyll *a*, such as were present in this study. This may explain the reduced effects of atrazine, but is in need of further study. Carfentrazone drift rates resulted in significantly lower rotifer and nauplii numbers compared to control levels the day after application, but not on the second day. Reductions ranged from 5-30% of control numbers and could not be explained from chlorophyll *a* data or net primary productivity. Zooplankton from diuron and atrazine were noted greatly impacted (Table 2). Propanil at 1 and 10% drift rates did not result in significant effects, although full field rates did (Perschbacher et al., 2002). Further evaluation

These studies indicate that drift effects from 40 common aerially-applied herbicide applications on plankton and water quality were limited to atrazine, diuron and carfentrazone (Table 1). Of the 40 herbicides, diuron presents the greater risk for reduced

Small water bodies, equal to or less than 1.2 ha, in alluvial plains may be subjected to greater drift concentrations from adjacent row crops, due to reduced surface areas and volumes (Perschbacher and Ludwig 2007). These small ponds may be used for growing early and vulnerable stages of commercial aquaculture crops, and for fish consumption by farm pond owners. The three herbicides causing appreciable impacts, atrazine, propanil and diuron,

**3. Evaluation of drift levels to small alluvial plain water bodies: atrazine,** 

water quality and for a longer time period, of at least 4 weeks (Table 2).

were further tested at maximum drift rates expected of 30% of field rates.

differences (*P* < 0.05) among treatments for each day during each trial.

**2.2 Results and discussion** 

of propanil is considered in the section 3.

**propanil and diuron** 

estimated 20 X higher drift deposition compared to application by ground spray booms (Hill et al., 1994).

#### **2. Evaluation of 40 aerially-applied row crop herbicide effects on water bodies**

Recent studies at the University of Arkansas at Pine Bluff (UAPB) have assessed the effects of herbicide drift from 40 herbicides used on adjacent soybean, rice, cotton, corn and winter wheat row crops to plankton and water quality in adjacent flood plain ponds (Perschbacher et al., 1997, 2002, 2008; Perschbacher and Ludwig, 2004). Herbicide drift may be expected to impact ponds through death or a reduction in the photosynthetic rate of phytoplankton, which could reduce the supply of dissolved oxygen, inhibit removal of toxic nitrogenous wastes, and reduce production of zooplankton by reducing the food supply (Waiser and Robarts, 1997). Aerial application has drift deposition 20 times higher compared to application by ground spray booms (Hill et al., 1994).%). The mode of action of herbicides impacting phytoplankton, is reversable inhibition of photosynthesis at photosystem II (PSII) and should not be species specific (Cobb, 1992; Solomon et al., 1996). Photosystem II inhibitors are widely used in agriculture, since they provide a low-cost basal weed control (Solomon et al., 1997; Jay et al., 1997).

#### **2.1 Methods and materials**

These studies were conducted to determine if aerially-applied herbicides would cause measurable plankton and water quality changes in outdoor pool mesocosms filled with water from a fish pond. Rates used encompassed the estimated range of drift and a field rate (full) equivalent to direct application. The studies were conducted at the UAPB Aquaculture Research Station at the approximate time of the year when the respective herbicides are applied. The experimental plankton mesocosms used were above ground, circular 500-L fiberglass tanks arranged in four rows on a cement pad. When filled, water depth of tanks was 0.7 m (slightly less than the average depth of most fish ponds) and there was no mud substrate. Water surface area of each tank was 0.78 m2 and diameter was 1.0 m, similar to those used in a prior study of atrazine effects on plankton and water quality (Juettner et al., 1995). Tanks were filled immediately prior to herbicide application with water pumped from an adjacent 0.1-ha pond.

Herbicides were applied over the tank surfaces at one of three levels: field rates (equal to overspray) and high and low drift rates of 1/10 and 1/100th of this level, respectively (Perschbacher et al., 1997). A control, without herbicide addition, was the fourth treatment. Each herbicide was tested at the recommended application rate (Baldwin et al., 2000). Commercial formulations were used without addition of adjuvants or wetting agents. Approximately 30 ml of distilled water was used to dissolve the herbicide. Each treatment was replicated three times in randomly- assigned tanks. Tanks were flushed and air-dried between trials.

Each herbicide was added to the tanks at approximately 0900. A set of measurements was taken immediately prior to application and again 24, 48 and 72 hours after application. If effects were noted, sampling was continued approximately weekly until morning oxygen (DO) levels of drift treatments did not significantly different from the control (ie. recovery). Dissolved oxygen is the water quality parameter most sensitive to herbicide effects (Juettner et al., 1995) and most critical to fish culture. Water temperature, dissolved oxygen and pH were measured with a multiprobe meter (OI Analytical, College Station, TX). Total ammonia nitrogen (TAN) and nitrite-nitrogen were measured by Nessler and diazotization methods (Hach Co., Loveland, CO), respectively. Unionized ammonia (UIA) levels were calculated from measured temperature, TAN and pH. Chlorophyll *a,* corrected for pheophytin *a,* and a 2-h light and dark bottle estimation of phytoplankton net primary productivity (NPP) by the oxygen method followed APHA (2005), except for use of ethanol as the solvent for chlorophyll (Nusch, 1980). Major zooplankton group concentrations were also determined in each replicate in the following manner. Three, 1-l samples were obtained with a tube sampler that encompassed the entire water column. The samples were concentrated by being strained through a 70-um Wisconsin plankton net and then preserved in 70% isopropyl alcohol. Samples were identified and quantified by using a Sedgwick-Rafter cell and a microscope (Ludwig, 1993). Statistical analysis was by SAS statistical software package. ANOVA (after pretesting for normality) and LSD were used to test for significant differences (*P* < 0.05) among treatments for each day during each trial.

#### **2.2 Results and discussion**

192 Herbicides – Properties, Synthesis and Control of Weeds

estimated 20 X higher drift deposition compared to application by ground spray booms (Hill

Recent studies at the University of Arkansas at Pine Bluff (UAPB) have assessed the effects of herbicide drift from 40 herbicides used on adjacent soybean, rice, cotton, corn and winter wheat row crops to plankton and water quality in adjacent flood plain ponds (Perschbacher et al., 1997, 2002, 2008; Perschbacher and Ludwig, 2004). Herbicide drift may be expected to impact ponds through death or a reduction in the photosynthetic rate of phytoplankton, which could reduce the supply of dissolved oxygen, inhibit removal of toxic nitrogenous wastes, and reduce production of zooplankton by reducing the food supply (Waiser and Robarts, 1997). Aerial application has drift deposition 20 times higher compared to application by ground spray booms (Hill et al., 1994).%). The mode of action of herbicides impacting phytoplankton, is reversable inhibition of photosynthesis at photosystem II (PSII) and should not be species specific (Cobb, 1992; Solomon et al., 1996). Photosystem II inhibitors are widely used in agriculture, since they provide a low-cost basal weed control

These studies were conducted to determine if aerially-applied herbicides would cause measurable plankton and water quality changes in outdoor pool mesocosms filled with water from a fish pond. Rates used encompassed the estimated range of drift and a field rate (full) equivalent to direct application. The studies were conducted at the UAPB Aquaculture Research Station at the approximate time of the year when the respective herbicides are applied. The experimental plankton mesocosms used were above ground, circular 500-L fiberglass tanks arranged in four rows on a cement pad. When filled, water depth of tanks was 0.7 m (slightly less than the average depth of most fish ponds) and there was no mud substrate. Water surface area of each tank was 0.78 m2 and diameter was 1.0 m, similar to those used in a prior study of atrazine effects on plankton and water quality (Juettner et al., 1995). Tanks were filled immediately prior to herbicide application with water pumped

Herbicides were applied over the tank surfaces at one of three levels: field rates (equal to overspray) and high and low drift rates of 1/10 and 1/100th of this level, respectively (Perschbacher et al., 1997). A control, without herbicide addition, was the fourth treatment. Each herbicide was tested at the recommended application rate (Baldwin et al., 2000). Commercial formulations were used without addition of adjuvants or wetting agents. Approximately 30 ml of distilled water was used to dissolve the herbicide. Each treatment was replicated three times in randomly- assigned tanks. Tanks were flushed and air-dried

Each herbicide was added to the tanks at approximately 0900. A set of measurements was taken immediately prior to application and again 24, 48 and 72 hours after application. If effects were noted, sampling was continued approximately weekly until morning oxygen (DO) levels of drift treatments did not significantly different from the control (ie. recovery). Dissolved oxygen is the water quality parameter most sensitive to herbicide effects (Juettner

**2. Evaluation of 40 aerially-applied row crop herbicide effects on water** 

et al., 1994).

**bodies** 

(Solomon et al., 1997; Jay et al., 1997).

**2.1 Methods and materials** 

from an adjacent 0.1-ha pond.

between trials.

Atrazine lowered NPP on d 2; and effects on ecosystems from field studies have been summarized as short-lived, with quick recovery at concentrations less than 50 ug/l (Solomon et al., 1996). Solomon et al. (1996) observed stimulation of chlorophyll *a* on d 7 post-application of 50 ug/L atrazine. This was also found by us at d 7 with propanil (Perschbacher et al. 1997, 2002). Edziyie (2004) noted drift from propanil affected fry ponds with <10 ug/l chlorophyll *a* less than culture ponds with levels of 50-85 ug/l of chlorophyll *a*, such as were present in this study. This may explain the reduced effects of atrazine, but is in need of further study. Carfentrazone drift rates resulted in significantly lower rotifer and nauplii numbers compared to control levels the day after application, but not on the second day. Reductions ranged from 5-30% of control numbers and could not be explained from chlorophyll *a* data or net primary productivity. Zooplankton from diuron and atrazine were noted greatly impacted (Table 2). Propanil at 1 and 10% drift rates did not result in significant effects, although full field rates did (Perschbacher et al., 2002). Further evaluation of propanil is considered in the section 3.

These studies indicate that drift effects from 40 common aerially-applied herbicide applications on plankton and water quality were limited to atrazine, diuron and carfentrazone (Table 1). Of the 40 herbicides, diuron presents the greater risk for reduced water quality and for a longer time period, of at least 4 weeks (Table 2).

#### **3. Evaluation of drift levels to small alluvial plain water bodies: atrazine, propanil and diuron**

Small water bodies, equal to or less than 1.2 ha, in alluvial plains may be subjected to greater drift concentrations from adjacent row crops, due to reduced surface areas and volumes (Perschbacher and Ludwig 2007). These small ponds may be used for growing early and vulnerable stages of commercial aquaculture crops, and for fish consumption by farm pond owners. The three herbicides causing appreciable impacts, atrazine, propanil and diuron, were further tested at maximum drift rates expected of 30% of field rates.

Row Crop Herbicide Drift Effects on Water Bodies and Aquaculture 195

**Diuron 1/10**

**Atrazine 1/100**

**Atrazine 1/10**

**1/100**

1 92\* 92\* 80 102 2 93\* 81\* 100 104 7 83\* 71\* 102 111\* Recovery (days) 21 >28 0 0

1 49\* 21\* 124 105 2 37\* 25\* 82\* 79\* 7 41\* 22\* 84 82

1 97 95 110 102 2 99 96 89 93 7 83\* 58\* 96 115

1 96\* 95\* 100 100 2 98\* 91\* 100 100 7 89\* 87\* 100 100

1 194\* 122\* 94 101 2 120 80 92 85 7 243\* 356\* 133 94

1 100 50\* 100 100 2 84 12\* 80 87 7 35\* 37\* 150\* 125

1 100 100 112 93 2 120 20 141 151\* 7 100 133 25 150

1 67 78 200 150 2 126 226 128 57 7 115 96 22\* 67

1 238 163 74 76 2 66 92 104 95 7 100 100 199 300

1 100 160 173 110 2 75 150 110 113 7 64 21\* 120 94

1 NA NA 120 94 2 NA NA 73 127 7 NA NA 100 82

NPP = Net Primary Productivity; TAN = Total Ammonia Nitrogen; UIA = Unionized Ammonia Table 2. Comparison of mean low (1/100 direct application rate) and high (1/10 direct application rate) drift effects of diuron and atrazine, expressed as percentage of control levels. Means significantly different (*P <* 0.05) from control means, indicated by \*.

**Days Post-Application Diuron**

**DO** 

**NPP** 

**pH**

**TAN**

**UIA** 

**Nitrite-N** 

**Rotifers**

**Copepod nauplii**

**Copepod adults**

**Cladocerans\***

diuron trials

\*no cladocerans observed in

DO = 0900 Dissolved Oxygen; Recovery = return of morning DO to control levels;

**Chlorophyll** *a*


Table 1. Summary of mesocosm tests of drift from aerially-applied herbicides by major crop, common name, trade name, date applied, recommended active ingredient (A.I.) field rate and approximate levels of pond plankton.

**Common Name Trade Name Date Applied A.I (kg/ha) Chl. (ug/l)** 

Bentazon Basagran 8/23 0.57 200 Imazaquin Image 8/2 0.14 240 Fomesafen Flexstar 8/16 0.43 250 Aciflourfen Blazer 8/9 0.43 270 Fluzifop Fusilade 8/16 0.10 240 Clethodim Prism 7/26 0.07 300 Chlorimuron Canopy 8/9 0.004 125 Glyphosphate Roundup 8/2 0.43 500 Flumiclorac Resource 6/8 0.045 135 Sethoxydim Vantage 6/1 0.45 239 Carfentrazone\* Aim 3/2 0.03 400

Clomazone Command 5/23 0.60 280 Thiobencarb Bolero 5/29 3.40 400 Pendamethalin Prowl 6/5 1.10 250 Propanil Stam 6/12 4.50 160 Quinclorac Facet 6/20 0.60 450 Halosulfuron Permit 6/27 0.07 475 Bensulfuron methyl Londax 7/5 0.07 240 2.4-D-amine 2,4-D 7/5 1.70 45 Molinate Ordram 7/25 5.60 450 Triclopyr Grandstand 7/11 0.40 115 Fenoxyprop-ethyl Acclaim 6/15 0.13 114 Cyhalofop Clincher 7/5 0.30 65 Bispyribac-sodium Regiment 7/12 0.036 114

Diuron (burndown)\* Direx 3/5 1.40 390 Diuron (defoliant) Direx 9/23 0.165 850 Paraquat Gramaxone 4/10 0.83 160 Quizalofop Assure 6/18 0.05 300 Dimethipin Harvade 9/16 0.15 750 Tribufos Def 10/7 1.00 1075 Ethephon Finish 10/14 1.76 1000 Sodium chlorate Defol 10/21 5.30 520 Glufosinate Liberty 3/13 0.55 344 Flumioxazin Valor 4/6 0.03 334

Mesotrione Callisto 5/30 1.80 150 Metolachlor Dual 3/8 0.10 350 Atrazine\* AAtrex 5/6 0.90 30 Rimsulfuron TranXit 5/3 0.90 40 Nicosulfuron Steadfast 4/29 0.90 105

Tribenuron Harmony Extra 3/25 0.028 189

Table 1. Summary of mesocosm tests of drift from aerially-applied herbicides by major crop, common name, trade name, date applied, recommended active ingredient (A.I.) field rate

**Soybean** 

**Rice** 

**Cotton** 

**Corn** 

noted

**Winter Wheat**  Thifensulfuron +

\* significant effects

and approximate levels of pond plankton.


DO = 0900 Dissolved Oxygen; Recovery = return of morning DO to control levels; NPP = Net Primary Productivity; TAN = Total Ammonia Nitrogen; UIA = Unionized Ammonia

Table 2. Comparison of mean low (1/100 direct application rate) and high (1/10 direct application rate) drift effects of diuron and atrazine, expressed as percentage of control levels. Means significantly different (*P <* 0.05) from control means, indicated by \*.

Row Crop Herbicide Drift Effects on Water Bodies and Aquaculture 197

productivity was significantly depressed on d 1 in the propanil treatments, but increased on d 2 and 3. Morning dissolved oxygen was lower on d 1-3, but not to critical levels. Also, in the presence of propanil, pH and consequently UIA were lower from d 1-3. Atrazine reduced morning DO on d 2 and 3, but not net primary productivity. Nitrite-N, however, was significantly higher on d 1. Phytoplankton total numbers, and the cyanobacterium *Chroococcus* sp. which dominated, were reduced by propanil on d 1-3; similarly affected by atrazine on d 2 and 3. Numbers of green algae, *Scenedesmus* sp. and *Coelastrum* sp*.*, and diatoms were however stimulated by propanil and diatoms by atrazine. Zooplankton were

Due to the greater impacts of diuron (at levels equivalent to 30 ug/l), response of important environmental metrics to diuron drift are presented in Tables 3-5. No significant differences in pre-application sampling were found. Following application of diuron, net primary productivity was reduced by 97%, and recovered on d 7 (Table 1). Morning oxygen concentration also declined on day 1 by 32%, and was at stressful levels from d 2-3. Recovery was attained on d 14. Chlorophyll *a* and pheophytin *a* levels were significantly higher on d 2-14. Levels of pH were reduced by diuron addition from d 1-14. With lower pH values, unionized ammonia was significantly less from d 2-14. Plankton were also significantly impacted. Cyanobacteria, with the exception of *Chroococcus* spp.*,* were reduced from d 1 and green algae*,* especially *Scenedesmus* spp. were stimulated (Table 4, 5). The other major group of phytoplankton, pinnate diatoms, were unchanged with the exception of a decline on d 7. In terms of percentage composition of the phytoplankton community, in diuron-treated mesocosms cyanobacteria declined from 24 to 20%, while green algae

Zooplankton groups with significantly reduced mean abundances included: nauplii-616/l compared to control level of 1750/l on d 7, and cladocerans-0/l treatment level compared to 33/l on d 2. Copepod numbers however increased: from 1483/l control level to treatment level of 2133/l on d 3, and from 1150/l control level to the 2133/l treatment level on d 4. Rotifers were not impacted, in contrast to the findings of Zimba et al. (2002) who found an

Diuron is a urea herbicide, that is 4-6 times more potent in photosynthesis inhibition than simazine herbicide (Ashton and Crafts, 1981). The concentration used in this study and representing the highest drift level of diuron (Direx) was 30 ug/l. Cyanobacteria were most susceptible to diuron, found previously with diuron (Zimba et al. 2002) and propanil and atrazine (Voronova and Pushkar 1985, Leboulanger et al. 2001, Perschbacher and Ludwig 2007). An increase in chlorophyll *a* was also noted by Ricart et al. (2009) in biofilms exposed to 0.07-9.0 ug/L diuron. This was attributed to a so-called "shade-adaptation" response to reduced photosynthetic efficiency from diuron. Zimba et al. (2002) observed no decrease in phytoplankton biomass, as measured by chlorophyll *a*, during 9 weekly treatments of 10 ug/l diuron each, but found the phytoplankton composition was altered. Numbers of filamentous cyanobacteria decreased, while ultraplankton coccoid cyanobacteria, diatoms and chlorophytes increased and chlorophyll *b* indicative of chlorophytes was significantly

increased from 45 to 72%. Diatoms also declined from 26 to 8% (Table 5).

little affected by either herbicide.

increase in rotifers.

higher on one sample date.

**3.3 Discussion** 

#### **3.1 Methods and materials**

The study was conducted at the University of Arkansas at Pine Bluff (UAPB) Aquaculture Research Station The experimental mesocosms were 500-l, above ground, circular fiberglass tanks arranged in four rows on a cement pad. When filled, water depth of the tanks was 0.7 m (slightly less than the average depth of most fish ponds) and there was no soil substrate. Surface area of each tank was 0.78 m2 and diameter was 1.0 m, similar to those used by Juettner et al.(1995). Tanks were filled immediately prior to herbicide application with water pumped from an adjacent 0.1-ha Aquaculture Research Station experimental pond. Total dissolved solids were 290 mg/l, hardness 185 mg/l and alkalinity 197 mg/l as calcium carbonate.

Commercial formulations, without adjuvants or wetting agents, were applied over the tank surfaces at 30% of field rates (Baldwin et al., 2000) in four randomly selected pools each. Four additional pools received no herbicide and served as controls. The level used was equivalent to highest potential cumulative drift concentrations based on graphs in Hill et al. (1994) to water bodies of 1.2 ha surface area. The experimental dose was added to 30 ml of distilled water for more uniform application over the tank surface.

Immediately following filling, the first set of measurements were taken. The suite of measurements was subsequently taken 24, 48 and 72 h after application. If impacts were noted, sampling was continued approximately weekly until morning oxygen levels of drift treatments did not significantly differ from the control. Dissolved oxygen is the water quality parameter most sensitive to herbicide effects (Juettner et al., 1995) and most critical to aquatic life. Water temperature, dissolved oxygen, total dissolved solids (TDS), and pH were measured with a multiprobe meter (YSI, Yellow Springs, OH). Total ammonia nitrogen and nitrite-nitrogen were measured by Nessler and diazotization methods (Hach Co., Loveland, CO), respectively. Unionized ammonia levels were obtained from water temperature, TDS, TAN and pH. Chlorophyll *a,* corrected for pheophytin *a* and using ethanol as a solvent (Nusch, 1980)*,* and a 2-h light and dark bottle estimation of net phytoplankton primary productivity by the oxygen method followed Standard Methods (APHA, 2005). Concentrations of the major zooplankton groups (rotifers, copepod nauplii, adult copepods and cladocerans) were also determined in each replicate in the following manner. Six, 1-L samples were obtained with a tube sampler that encompassed the entire water column. The samples were concentrated by being strained through a 70-um Wisconsin plankton net and then preserved in 70% isopropyl alcohol. Samples were identified and quantified by using a Sedgwick-Rafter cell and a microscope. Phytoplankton were enumerated and identified to genus (Prescott, 1962) in Sedgwick-Rafter cells with Whipple grid at 150X (APHA, 2005) from 20 ml unconcentrated samples obtained with a 0.9 m polyvinyl chloride (PVC) column sampler and preserved with 1 ml of formalin. Cyanobacteria were further identified to species using Cocke (1967). A randomized block design was used. Means from each sample date were tested for significant differences (*P* < 0.05) with controls by paired, single tail Student's t-tests.

#### **3.2 Results**

Propanil levels were 58 ug/l and atrazine levels were 19.5 ug/l. Significant changes from control treatment values were found for several parameters in all three herbicide treatments (Perschbacher and Ludwig, 2007). Following application on 20 June, net primary productivity was significantly depressed on d 1 in the propanil treatments, but increased on d 2 and 3. Morning dissolved oxygen was lower on d 1-3, but not to critical levels. Also, in the presence of propanil, pH and consequently UIA were lower from d 1-3. Atrazine reduced morning DO on d 2 and 3, but not net primary productivity. Nitrite-N, however, was significantly higher on d 1. Phytoplankton total numbers, and the cyanobacterium *Chroococcus* sp. which dominated, were reduced by propanil on d 1-3; similarly affected by atrazine on d 2 and 3. Numbers of green algae, *Scenedesmus* sp. and *Coelastrum* sp*.*, and diatoms were however stimulated by propanil and diatoms by atrazine. Zooplankton were little affected by either herbicide.

Due to the greater impacts of diuron (at levels equivalent to 30 ug/l), response of important environmental metrics to diuron drift are presented in Tables 3-5. No significant differences in pre-application sampling were found. Following application of diuron, net primary productivity was reduced by 97%, and recovered on d 7 (Table 1). Morning oxygen concentration also declined on day 1 by 32%, and was at stressful levels from d 2-3. Recovery was attained on d 14. Chlorophyll *a* and pheophytin *a* levels were significantly higher on d 2-14. Levels of pH were reduced by diuron addition from d 1-14. With lower pH values, unionized ammonia was significantly less from d 2-14. Plankton were also significantly impacted. Cyanobacteria, with the exception of *Chroococcus* spp.*,* were reduced from d 1 and green algae*,* especially *Scenedesmus* spp. were stimulated (Table 4, 5). The other major group of phytoplankton, pinnate diatoms, were unchanged with the exception of a decline on d 7. In terms of percentage composition of the phytoplankton community, in diuron-treated mesocosms cyanobacteria declined from 24 to 20%, while green algae increased from 45 to 72%. Diatoms also declined from 26 to 8% (Table 5).

Zooplankton groups with significantly reduced mean abundances included: nauplii-616/l compared to control level of 1750/l on d 7, and cladocerans-0/l treatment level compared to 33/l on d 2. Copepod numbers however increased: from 1483/l control level to treatment level of 2133/l on d 3, and from 1150/l control level to the 2133/l treatment level on d 4. Rotifers were not impacted, in contrast to the findings of Zimba et al. (2002) who found an increase in rotifers.

#### **3.3 Discussion**

196 Herbicides – Properties, Synthesis and Control of Weeds

The study was conducted at the University of Arkansas at Pine Bluff (UAPB) Aquaculture Research Station The experimental mesocosms were 500-l, above ground, circular fiberglass tanks arranged in four rows on a cement pad. When filled, water depth of the tanks was 0.7 m (slightly less than the average depth of most fish ponds) and there was no soil substrate. Surface area of each tank was 0.78 m2 and diameter was 1.0 m, similar to those used by Juettner et al.(1995). Tanks were filled immediately prior to herbicide application with water pumped from an adjacent 0.1-ha Aquaculture Research Station experimental pond. Total dissolved solids were 290 mg/l, hardness 185 mg/l and alkalinity 197 mg/l as calcium

Commercial formulations, without adjuvants or wetting agents, were applied over the tank surfaces at 30% of field rates (Baldwin et al., 2000) in four randomly selected pools each. Four additional pools received no herbicide and served as controls. The level used was equivalent to highest potential cumulative drift concentrations based on graphs in Hill et al. (1994) to water bodies of 1.2 ha surface area. The experimental dose was added to 30 ml of

Immediately following filling, the first set of measurements were taken. The suite of measurements was subsequently taken 24, 48 and 72 h after application. If impacts were noted, sampling was continued approximately weekly until morning oxygen levels of drift treatments did not significantly differ from the control. Dissolved oxygen is the water quality parameter most sensitive to herbicide effects (Juettner et al., 1995) and most critical to aquatic life. Water temperature, dissolved oxygen, total dissolved solids (TDS), and pH were measured with a multiprobe meter (YSI, Yellow Springs, OH). Total ammonia nitrogen and nitrite-nitrogen were measured by Nessler and diazotization methods (Hach Co., Loveland, CO), respectively. Unionized ammonia levels were obtained from water temperature, TDS, TAN and pH. Chlorophyll *a,* corrected for pheophytin *a* and using ethanol as a solvent (Nusch, 1980)*,* and a 2-h light and dark bottle estimation of net phytoplankton primary productivity by the oxygen method followed Standard Methods (APHA, 2005). Concentrations of the major zooplankton groups (rotifers, copepod nauplii, adult copepods and cladocerans) were also determined in each replicate in the following manner. Six, 1-L samples were obtained with a tube sampler that encompassed the entire water column. The samples were concentrated by being strained through a 70-um Wisconsin plankton net and then preserved in 70% isopropyl alcohol. Samples were identified and quantified by using a Sedgwick-Rafter cell and a microscope. Phytoplankton were enumerated and identified to genus (Prescott, 1962) in Sedgwick-Rafter cells with Whipple grid at 150X (APHA, 2005) from 20 ml unconcentrated samples obtained with a 0.9 m polyvinyl chloride (PVC) column sampler and preserved with 1 ml of formalin. Cyanobacteria were further identified to species using Cocke (1967). A randomized block design was used. Means from each sample date were tested for significant differences (*P* <

Propanil levels were 58 ug/l and atrazine levels were 19.5 ug/l. Significant changes from control treatment values were found for several parameters in all three herbicide treatments (Perschbacher and Ludwig, 2007). Following application on 20 June, net primary

distilled water for more uniform application over the tank surface.

0.05) with controls by paired, single tail Student's t-tests.

**3.1 Methods and materials** 

carbonate.

**3.2 Results** 

Diuron is a urea herbicide, that is 4-6 times more potent in photosynthesis inhibition than simazine herbicide (Ashton and Crafts, 1981). The concentration used in this study and representing the highest drift level of diuron (Direx) was 30 ug/l. Cyanobacteria were most susceptible to diuron, found previously with diuron (Zimba et al. 2002) and propanil and atrazine (Voronova and Pushkar 1985, Leboulanger et al. 2001, Perschbacher and Ludwig 2007). An increase in chlorophyll *a* was also noted by Ricart et al. (2009) in biofilms exposed to 0.07-9.0 ug/L diuron. This was attributed to a so-called "shade-adaptation" response to reduced photosynthetic efficiency from diuron. Zimba et al. (2002) observed no decrease in phytoplankton biomass, as measured by chlorophyll *a*, during 9 weekly treatments of 10 ug/l diuron each, but found the phytoplankton composition was altered. Numbers of filamentous cyanobacteria decreased, while ultraplankton coccoid cyanobacteria, diatoms and chlorophytes increased and chlorophyll *b* indicative of chlorophytes was significantly higher on one sample date.

Row Crop Herbicide Drift Effects on Water Bodies and Aquaculture 199

*Scenedesmus spp.* C 30.6 19.3 10.0 0.3\*

*Ankistrodesmus spp.* C 1.4 2.3 1.5 0.5\*

*Coelastrum spp.* C 1.1 0.8 0.1\* 0.0\*

*Anabaena levanderi* C 0.3 0.3 1.3\* 12.3\*

*Anabaena circinalis* C 0.1 0.2 0.5\* 3.5\*

Pinnate diatoms C 10.7 8.8 16.5\* 1.0

Cyanobacteria C 23.1 31.8\* 55.7\* 95.6\*

Green C 51.6 47.4\* 18.8\* 2.0\*

Diatom C 22.5 20.6 25.5 20.0\*

Table 5. Mean % composition of major phytoplankton groups by natural units, with and without diuron addition, over time. Column means significantly different are \* (*P* < 0.05).

Table 4. Mean phytoplankton (103 cells/ml) in diuron (D) and control (C) treatments.

Groups Treatment Time (d)

*Oscillatoria angustissma* 

*Chroococcus dispersus* 

Column means significantly different have \* (*P* < 0.05).

0 2 7 14

D 19.0 32.7 20.9 12.7

D 2.1 2.5 1.5 2.5

D 1.2 1.1 1.1 0.3

D 0.2 0.1 0.0 0.0

D 0.1 0.1 0.0 0.1

C 7.1 11.3\* 27.3\* 27.9\*

D 3.9 5.6 18.7 0.1

C 3.3 2.7 6.7 0.2

D 8.0 1.3 3.9 4.5

D 10.4 6.8 4.7 1.8

0 2 7 14

D 24.1 12.5 14.3 20.0

D 45.4 71.8 68.1 72.0

D 25.7 15.7 17.5 7.8

Species/Genera Treatment Time (d)

Although drift levels of diuron in the present study were 3 times higher than in the Perschbacher and Ludwig (2004) study, which evaluated maximum drift effects to water bodies over 7 ha, inhibition of photosynthesis was longer lasting in the 2004 study. The dominance of cyanobacteria which formed surface scums and were thus unstable in the former study may have been responsible for the greater impacts, as found for propanil (Edziyie, 2004).

The present study found that in small eutrophic ponds, typical in agricultural environments and with relatively high chlorophyll *a* levels, short-term negative impacts would be expected on morning DO from atrazine, propanil and diuron. However, they may also benefit water quality by reducing pH, a major concern in eutrophic ponds utilized for recreational fish production and commercial fish culture (Barkoh et al., 2005; Ludwig et al., 2007) and which in turn resulted in lowered unionized ammonia levels.


DO = 0900 Dissolved Oxygen; NPP = Net Primary Productivity; UIA = Unionized Ammonia; ND = No Data

Table 3. Mean (SE) water quality differences in diuron (D) and control (C) treatments. Column means significantly different have different letters (*P* < 0.05).

Although drift levels of diuron in the present study were 3 times higher than in the Perschbacher and Ludwig (2004) study, which evaluated maximum drift effects to water bodies over 7 ha, inhibition of photosynthesis was longer lasting in the 2004 study. The dominance of cyanobacteria which formed surface scums and were thus unstable in the former study may have been responsible for the greater impacts, as found for propanil

The present study found that in small eutrophic ponds, typical in agricultural environments and with relatively high chlorophyll *a* levels, short-term negative impacts would be expected on morning DO from atrazine, propanil and diuron. However, they may also benefit water quality by reducing pH, a major concern in eutrophic ponds utilized for recreational fish production and commercial fish culture (Barkoh et al., 2005; Ludwig et al.,

0 1 2 3 7 14

DO (mg/l) C 16.13 14.83\* 11.23\* 8.63\* 6.73\* 8.73 D 16.07 11.02 3.10 2.50 4.63 7.87

D 1.47 0.05 0.07 ND 0.22 0.32

D 209.2 131.6 126.5 108.0 118.1 ND

D 45.9 47.9 38.7 33.7 21.2 ND

pH C 8.57 8.73\* 8.63\* 8.42\* 8.20\* 8.47\* D 8.60 8.60 8.07 7.73 7.75 8.17

UIA (mg/l) C 0.01 0.02 0.02\* 0.01\* 0.01\* 0.10\* D 0.02 0.02 0.01 0.00 0.00 0.00

DO = 0900 Dissolved Oxygen; NPP = Net Primary Productivity; UIA = Unionized Ammonia;

Table 3. Mean (SE) water quality differences in diuron (D) and control (C) treatments.

Column means significantly different have different letters (*P* < 0.05).

C 1.28 0.63\* 0.51\* ND 0.13 0.35

C 202.4 113.0 81.0\* 70.8\* 37.1\* ND

C 31.4\* 41.7 19.4\* 23.6 4.2\* ND

2007) and which in turn resulted in lowered unionized ammonia levels.

Parameters Treatment Time (d)

(Edziyie, 2004).

NPP (mg O2/l/h)

Chlorophyll *a* (ug/l)

Pheophytin *a* (ug/l)

ND = No Data


Table 4. Mean phytoplankton (103 cells/ml) in diuron (D) and control (C) treatments. Column means significantly different have \* (*P* < 0.05).


Table 5. Mean % composition of major phytoplankton groups by natural units, with and without diuron addition, over time. Column means significantly different are \* (*P* < 0.05).

Row Crop Herbicide Drift Effects on Water Bodies and Aquaculture 201

a longer time period (in excess of 4 wks). Atrazine effects are short-lived . Carfentrazone

Algal populations forming scums appear more susceptible to these drift levels. Propanil levels which did not result in reductions in water quality in mixed water column populations, resulted in adverse reactions equal to the direct overspray. The concentration of algae at the surface and the propensity for algae in this stage to be unstable (crash) are

Effects of propanil and atrazine drift, and perhaps of other herbicides, depend on the level of chlorophyll *a* found in the systems. The greatest impact of propanil was on water quality in ponds with chlorophyll *a* levels 50-200 ug/l and lesser impacts below 20 and above 300

Simulations in small ponds, equal to or less than 1.2 ha, used drift rates up to 30%. Although atrazine and propanil did not cause concern, diuron caused DO drops that were below 3

Beneficial effects of atrazine, propanil and diuron included reduction or elimination of cyanobacteria, and reduced pH (Ludwig et al., 2007) and thus reduced UIA. Clorophyll *a*

Students Baendo Lihono, and Malisa Hodges, and Jason Brown from USDA/ARS SNARC ably assisted the study. Dr. J. Dulka and Dupont kindly supplied the Basis Gold and component herbicides. C. Guy Jr., N. Slaton, H. Thomforde, W. Johnson, J. Ross, R Scott, and J. Welch of the Cooperative Extension Service are thanked for providing information on herbicides and herbicide samples. Virginia Perschbacher kindly assisted in manuscript preparation. Funding was from State of Arkansas, USDA/CSREES Project ARX 05013 and Grant No. 2001-52101-11300 Initiative for Future Agriculture and Food Systems and Catfish

APHA (American Public Health Association), (2005*). Standard Methods for the Examination of* 

*Water and Wastewater. 21st Edition,* American Public Health Association, ISBN

resulted in brief zooplankton reductions.

judged responsible.

**5.2 Surface scum algal populations simulations** 

**5.3 Differing chlorophyll** *a* **level simulations** 

**5.4 Small pond (1.2 ha and smaller) simulations** 

**5.5 Beneficial aspects of herbicide drift** 

**6. Acknowledgements** 

**7. References** 

levels were stimulated by propanil and atrazine.

Farmers of Arkansas Promotion Board Grant #6.

97780875530475, Washington, D.C, USA.

ug/l. Absorption by algae, and other factors, may be responsible.

mg/l for several days and recovery was not noted until 14 days.

### **4. Modifiying factors due to algal state from** *in situ* **mesocosm testing**

Aquaculture ponds often have surface floating scums predominately composed of cyanobacteria. These scum-forming algae are common in eutrophic ponds, including aquaculture ponds, especially during the growing season with warm temperatures and high nutrient loadings. Cyanobacteria in a suface scum state are unstable and prone to sudden die-offs (Boyd et al., 1975). The objective of this study was to test the effect of propanil on a pond with algal scums.

#### **4.1 Methods and materials**

The experiment was conducted at the University of Arkansas at Pine Bluff mesocosm facility. A completely randomized design was used, with three replicates for each treatment in 12 mesocosms and with water of approximately 400 ug/l chlorophyll *a* from a goldfish pond. The treatments used were: a control with no propanil, 1%, 10% and 100% of the recommended field rates (0.45 kg/ha). Variables measured included: morning dissolved oxygen, pH, nitrite-nitrogen, total ammonia nitrogen, unionized ammonia , net primary productivity, chlorophyll *a* and phytoplankton composition. Methods followed Standard Methods (APHA 2005). Samples were taken before and after treatments were added.

#### **4.2 Results and discussion**

*Microsystis* and *Anabaena* dominated the phytoplankton and formed the surface scum. Significantly lower DO and net primary productivity resulted after application in the 10% and full treatment. However, recovery was noted after 48 h. Also lower was pH following application. Tan and UIA were higher on d 2.

In the earlier trials (Perschbacher et al., 1997, 2002) without surface scum algae, propanil at 10% drift resulted only in elevated chlorophyll *a*, but no significant differences were noted in chlorophyll *a* and phytoplankton composition in the present study. Thus, the significant negative impacts found in the present study were not expressed in previous studies, and the difference is attributed to the algal state.

Effects of propanil drift depended on the level of chlorophyll *a* found in the systems, in the study by Edziyie (2005). The greatest impact was on water quality in ponds with chlorophyll *a* levels 50-200 ug/l and lesser impacts below 20 and above 300 ug/l. Phytoplankton at high levels have been proposed to modify pesticide effects by sorption to the algae (Day and Kaushik, 1987; Waiser and Robarts, 1997; Stampfli et al., 2011).
