Lowering pH enhances copper toxicity: A novel strategy for controlling harmful algal blooms and off-flavors
Harmful algal blooms (HABs) severely disrupt aquatic ecosystems by degrading water quality and producing unpalatable off-flavors in aquaculture products and drinking water. Copper sulfate pentahydrate (CuSO4·5 H2O) has been used as an affordable and FDA-approved algaecide to manage HABs for decades....
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| Format: | Article |
| Language: | English |
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Elsevier
2025-09-01
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| Series: | Ecotoxicology and Environmental Safety |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S0147651325008942 |
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| author | Ashley V. Hennessey Michael B. McDonald Peyton P. Johnson Matthew F. Gladfelter Kate L. Merrill Suzanne E. Tenison Sathya S. Ganegoda Tham C. Hoang H. Allen Torbert Benjamin H. Beck Alan E. Wilson |
| author_facet | Ashley V. Hennessey Michael B. McDonald Peyton P. Johnson Matthew F. Gladfelter Kate L. Merrill Suzanne E. Tenison Sathya S. Ganegoda Tham C. Hoang H. Allen Torbert Benjamin H. Beck Alan E. Wilson |
| author_sort | Ashley V. Hennessey |
| collection | DOAJ |
| description | Harmful algal blooms (HABs) severely disrupt aquatic ecosystems by degrading water quality and producing unpalatable off-flavors in aquaculture products and drinking water. Copper sulfate pentahydrate (CuSO4·5 H2O) has been used as an affordable and FDA-approved algaecide to manage HABs for decades. However, growing concerns about long-term negative environmental impacts and the diminishing efficacy of treatments over time have prompted the exploration of alternative treatment strategies. Copper toxicity is hypothesized to increase with lower pH as the cupric ion, which is most often associated with toxicity, becomes the most dominant form of copper. To rigorously evaluate this effect, ∼1600 L mesocosms were placed in a hypereutrophic pond and treated with a 20 µg/L Cu dose (0.08 mg/L CuSO4·5 H2O) or an 80 µg/L Cu dose (0.33 mg/L CuSO4·5 H2O). Half of the enclosures received a CO2 addition that dropped the pH in the enclosures from 9.15 to 7.58 prior to Cu treatment. The addition of CO2 for the 20 µg/L Cu dose resulted in 14 % greater removal of cyanobacteria in the first 24 h and a 20 % reduction of off-flavors in the first 3 d, which was significantly more effective than treatments without CO2. After one week, treatments with CuSO4·5 H2O and a CO2 addition continued to see a significant reduction in cyanobacteria (>94 %) and off-flavors (>95 %); furthermore, beneficial chlorophytes were significantly promoted (+512 %), which was not observed in treatments without CO2 or the controls. This approach mitigated cyanobacteria and off-flavors and promoted beneficial phytoplankton, all while using just 5 % of the copper dose that is typically recommended. |
| format | Article |
| id | doaj-art-2198ff6ed34f42669f294f247fbd0ac3 |
| institution | Kabale University |
| issn | 0147-6513 |
| language | English |
| publishDate | 2025-09-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Ecotoxicology and Environmental Safety |
| spelling | doaj-art-2198ff6ed34f42669f294f247fbd0ac32025-08-20T03:41:50ZengElsevierEcotoxicology and Environmental Safety0147-65132025-09-0130211854910.1016/j.ecoenv.2025.118549Lowering pH enhances copper toxicity: A novel strategy for controlling harmful algal blooms and off-flavorsAshley V. Hennessey0Michael B. McDonald1Peyton P. Johnson2Matthew F. Gladfelter3Kate L. Merrill4Suzanne E. Tenison5Sathya S. Ganegoda6Tham C. Hoang7H. Allen Torbert8Benjamin H. Beck9Alan E. Wilson10School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL, United StatesSchool of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL, United StatesSchool of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL, United StatesSchool of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL, United StatesSchool of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL, United StatesSchool of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL, United StatesSchool of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL, United StatesSchool of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL, United StatesUSDA-ARS, National Soil Dynamics Laboratory, Auburn, AL, United StatesUSDA-ARS, Aquatic Animal Health Research Unit, Auburn, AL, United StatesSchool of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL, United States; Correspondence to: Auburn University, 203 Swingle Hall, AL 36849, United States.Harmful algal blooms (HABs) severely disrupt aquatic ecosystems by degrading water quality and producing unpalatable off-flavors in aquaculture products and drinking water. Copper sulfate pentahydrate (CuSO4·5 H2O) has been used as an affordable and FDA-approved algaecide to manage HABs for decades. However, growing concerns about long-term negative environmental impacts and the diminishing efficacy of treatments over time have prompted the exploration of alternative treatment strategies. Copper toxicity is hypothesized to increase with lower pH as the cupric ion, which is most often associated with toxicity, becomes the most dominant form of copper. To rigorously evaluate this effect, ∼1600 L mesocosms were placed in a hypereutrophic pond and treated with a 20 µg/L Cu dose (0.08 mg/L CuSO4·5 H2O) or an 80 µg/L Cu dose (0.33 mg/L CuSO4·5 H2O). Half of the enclosures received a CO2 addition that dropped the pH in the enclosures from 9.15 to 7.58 prior to Cu treatment. The addition of CO2 for the 20 µg/L Cu dose resulted in 14 % greater removal of cyanobacteria in the first 24 h and a 20 % reduction of off-flavors in the first 3 d, which was significantly more effective than treatments without CO2. After one week, treatments with CuSO4·5 H2O and a CO2 addition continued to see a significant reduction in cyanobacteria (>94 %) and off-flavors (>95 %); furthermore, beneficial chlorophytes were significantly promoted (+512 %), which was not observed in treatments without CO2 or the controls. This approach mitigated cyanobacteria and off-flavors and promoted beneficial phytoplankton, all while using just 5 % of the copper dose that is typically recommended.http://www.sciencedirect.com/science/article/pii/S0147651325008942CyanobacteriaCopper sulfateSustainability2-methylisoborneolGeosminCO2 |
| spellingShingle | Ashley V. Hennessey Michael B. McDonald Peyton P. Johnson Matthew F. Gladfelter Kate L. Merrill Suzanne E. Tenison Sathya S. Ganegoda Tham C. Hoang H. Allen Torbert Benjamin H. Beck Alan E. Wilson Lowering pH enhances copper toxicity: A novel strategy for controlling harmful algal blooms and off-flavors Ecotoxicology and Environmental Safety Cyanobacteria Copper sulfate Sustainability 2-methylisoborneol Geosmin CO2 |
| title | Lowering pH enhances copper toxicity: A novel strategy for controlling harmful algal blooms and off-flavors |
| title_full | Lowering pH enhances copper toxicity: A novel strategy for controlling harmful algal blooms and off-flavors |
| title_fullStr | Lowering pH enhances copper toxicity: A novel strategy for controlling harmful algal blooms and off-flavors |
| title_full_unstemmed | Lowering pH enhances copper toxicity: A novel strategy for controlling harmful algal blooms and off-flavors |
| title_short | Lowering pH enhances copper toxicity: A novel strategy for controlling harmful algal blooms and off-flavors |
| title_sort | lowering ph enhances copper toxicity a novel strategy for controlling harmful algal blooms and off flavors |
| topic | Cyanobacteria Copper sulfate Sustainability 2-methylisoborneol Geosmin CO2 |
| url | http://www.sciencedirect.com/science/article/pii/S0147651325008942 |
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