Optimizing the use of quicklime (CaO) for sea urchin management — A lab and field study

Mass blooms of sea urchins sometimes cause kelp forest collapses that can last for decades. Quicklime has historically been used to reverse those conditions, but the efficacy of liming has varied along latitudinal and temperature gradients for reasons that are not fully understood. To evaluate the feasibility and ecological impacts of liming in a high latitude area in Northern Norway (70°N), we conducted a field pilot study in 2008–2011, a follow-up lab study in 2017, and a further field study in 2018–2019, with the latter evaluating and implementing the previous results in a site high in refuges. It was found that liming can reduce sea urchin densities sufficiently for macroalgal revegetation to occur, and that the mobile fauna species richness and abundance increased in the re-vegetated in comparison to the barren control fields. Also, the remaining sea urchins in the treated fields increased their roe content to commercial levels after 2 years. The lab experiments in 2017 indicated that the liming method is season/temperature-independent, as mortality remained at the same level irrespective of whether treatment started in the spring, when the sea temperatures were 2 °C, or in autumn when the temperatures were closer to 10 °C. The most important factor in treatment efficacy in the lab was particle size. With similar doses, the particles in the smallest size range (0–0.5 mm) caused 100% mortality, while the 0.5–2 mm and 2–4 mm fractions caused only 13% and 2% mortality respectively. In 2018–2019 we tested the fine CaO fraction (0.1–0.6 mm) and the medium fraction (0.5–2 mm) in a field experiment in areas characterized by high levels of refuges. Within 11 days, the sea urchin densities in the three fields treated with the fine lime were reduced to levels that theoretically should allow revegetation, but only in one of those fields was that potential partly realized after 1 year. The lack of effect in the two other fields was probably due to urchins protected by the substrate during treatment reappearing in sufficient numbers to prevent macroalgal regrowth, demonstrating that CaO treatment can be less effective on substrates where part of the sea urchin population hides among stones. Of the three variables held up as potential explanations for the different effects of CaO treatment in previous studies, we conclude based on our experiments that the presence of refuges and particle size were probably more important than temperature. Further improvements for larger scale treatments are discussed.publishedVersio

Lime-cement stabilisation of Trondheim clays and its impact on carbon dioxide emissions

publishedVersio

Determining the risk of calcium oxide (CaO) particle exposure to marine organisms

Calcium oxide (CaO) is being considered as a possible treatment for both the control of echinoderm populations and the treatment against sea lice infestation in Norwegian salmon farms. CaO particles produce an exothermal reaction when in contact with water, which can cause epidermal burns and lesions to certain target organisms leading to death. The aim of the present study was to determine the effects of fine (<0.8 mm) and coarse (<2.5 mm) CaO particles to a range of marine species from different taxonomic groups: two echinoderms (Asterias ruben and Strongylocentrotus droebachiensis); two crustaceans (Carcinus maenas and Tisbe battagliai); two molluscs (Mytilus edulis and Hinia reticulata); a polychaete (Nereis pelagica); a fish (Cyclopterus sp.); and seaweed germlings (Fucus vesiculosus). Overall, the fine CaO particles were more toxic to the selected marine species than the coarse particles. Coarse CaO particle effects were only observed in four of the nine species tested (A. rubens, S. droebachiensis, N. pelagica, T. battagliai) with similar LC50 values between 207 and 268 g/m2. For the fine CaO particles, the lowest LC50 was for the epibenthic copepod (T. battagliai) at 3.14 g/m2, followed by the sea urchin (20.1 g/m2), starfish (22.2 g/m2), ragworm (29.6 g/m2), and netted dog whelk (41.9 g/m2). Lump sucker fish exhibited significant mortalities only at the highest fine CaO concentration tested (320 g/m2) and recorded an LC50 of 226 g/m2. The toxicity data were used to generate species sensitivity distributions (SSDs) for both fine and coarse CaO particles. The hazard concentrations for 5% of the species (HC5) calculated from the SSDs, based on NOEC values, for the coarse and fine particles were 35.5 and 1.5 g/m2 respectively. Using a recommended assessment factor of 5, the Predicted No Effect Concentration (PNEC) was calculated as 7.1 and 0.3 g/m2 for coarse and fine CaO particles respectively.publishedVersio

Transformation Kinetics of Burnt Lime in Freshwater and Sea Water

Calcium oxide (CaO), also known as burnt lime, is being considered as a possible treatment to reduce the negative impact of sea urchins on tare forests in northern coastal waters and blue-green algal blooms in the surrounding of fish-farms. In this respect, the reaction kinetics of burnt lime in contact with sea water has been elucidated and compared to its behaviour in fresh water. In the first minutes of contact between burnt lime and water, it “slaked” as CaO reacted with water to yield calcium hydroxide (Ca(OH)2). Subsequently, calcium hydroxide reacted with magnesium, sulphate and carbonate from the sea water to yield magnesium hydroxide (Mg(OH)2), calcium sulphate dihydrate (gypsum, CaSO4·2H2O) and calcium carbonate (CaCO3), respectively. In a closed system of 1% CaO in natural sea water (where the supply of sulphate, magnesium and carbonate is limited), more than 90% reacted within the first 5 h. It is foreseen that in an open system, like a marine fjord, it will react even faster. The pH 8 of sea water close to the CaO particle surface will immediately increase to a theoretical value of about 12.5 but will, in an open system with large excess of sea water, rapidly fall back to pH 10.5 being equilibrium pH of magnesium hydroxide. This is further reduced to <9 due to the common ion effect of dissolved magnesium in sea water and then be diluted to the sea water background pH, about 8. Field test dosing CaO particles to sea water showed that the pH of water between the particles stayed around 8.publishedVersio

Determining the risk of calcium oxide (CaO) particle exposure to marine organisms

Calcium oxide (CaO) is being considered as a possible treatment for both the control of echinoderm populations and the treatment against sea lice infestation in Norwegian salmon farms. CaO particles produce an exothermal reaction when in contact with water, which can cause epidermal burns and lesions to certain target organisms leading to death. The aim of the present study was to determine the effects of fine (<0.8 mm) and coarse (<2.5 mm) CaO particles to a range of marine species from different taxonomic groups: two echinoderms (Asterias ruben and Strongylocentrotus droebachiensis); two crustaceans (Carcinus maenas and Tisbe battagliai); two molluscs (Mytilus edulis and Hinia reticulata); a polychaete (Nereis pelagica); a fish (Cyclopterus sp.); and seaweed germlings (Fucus vesiculosus). Overall, the fine CaO particles were more toxic to the selected marine species than the coarse particles. Coarse CaO particle effects were only observed in four of the nine species tested (A. rubens, S. droebachiensis, N. pelagica, T. battagliai) with similar LC50 values between 207 and 268 g/m2. For the fine CaO particles, the lowest LC50 was for the epibenthic copepod (T. battagliai) at 3.14 g/m2, followed by the sea urchin (20.1 g/m2), starfish (22.2 g/m2), ragworm (29.6 g/m2), and netted dog whelk (41.9 g/m2). Lump sucker fish exhibited significant mortalities only at the highest fine CaO concentration tested (320 g/m2) and recorded an LC50 of 226 g/m2. The toxicity data were used to generate species sensitivity distributions (SSDs) for both fine and coarse CaO particles. The hazard concentrations for 5% of the species (HC5) calculated from the SSDs, based on NOEC values, for the coarse and fine particles were 35.5 and 1.5 g/m2 respectively. Using a recommended assessment factor of 5, the Predicted No Effect Concentration (PNEC) was calculated as 7.1 and 0.3 g/m2 for coarse and fine CaO particles respectively

Transformation Kinetics of Burnt Lime in Freshwater and Sea Water

Calcium oxide (CaO), also known as burnt lime, is being considered as a possible treatment to reduce the negative impact of sea urchins on tare forests in northern coastal waters and blue-green algal blooms in the surrounding of fish-farms. In this respect, the reaction kinetics of burnt lime in contact with sea water has been elucidated and compared to its behaviour in fresh water. In the first minutes of contact between burnt lime and water, it “slaked” as CaO reacted with water to yield calcium hydroxide (Ca(OH)2). Subsequently, calcium hydroxide reacted with magnesium, sulphate and carbonate from the sea water to yield magnesium hydroxide (Mg(OH)2), calcium sulphate dihydrate (gypsum, CaSO4·2H2O) and calcium carbonate (CaCO3), respectively. In a closed system of 1% CaO in natural sea water (where the supply of sulphate, magnesium and carbonate is limited), more than 90% reacted within the first 5 h. It is foreseen that in an open system, like a marine fjord, it will react even faster. The pH 8 of sea water close to the CaO particle surface will immediately increase to a theoretical value of about 12.5 but will, in an open system with large excess of sea water, rapidly fall back to pH 10.5 being equilibrium pH of magnesium hydroxide. This is further reduced to <9 due to the common ion effect of dissolved magnesium in sea water and then be diluted to the sea water background pH, about 8. Field test dosing CaO particles to sea water showed that the pH of water between the particles stayed around 8

Transformation Kinetics of Burnt Lime in Freshwater and Sea Water

Calcium oxide (CaO), also known as burnt lime, is being considered as a possible treatment to reduce the negative impact of sea urchins on tare forests in northern coastal waters and blue-green algal blooms in the surrounding of fish-farms. In this respect, the reaction kinetics of burnt lime in contact with sea water has been elucidated and compared to its behaviour in fresh water. In the first minutes of contact between burnt lime and water, it “slaked” as CaO reacted with water to yield calcium hydroxide (Ca(OH)2). Subsequently, calcium hydroxide reacted with magnesium, sulphate and carbonate from the sea water to yield magnesium hydroxide (Mg(OH)2), calcium sulphate dihydrate (gypsum, CaSO4·2H2O) and calcium carbonate (CaCO3), respectively. In a closed system of 1% CaO in natural sea water (where the supply of sulphate, magnesium and carbonate is limited), more than 90% reacted within the first 5 h. It is foreseen that in an open system, like a marine fjord, it will react even faster. The pH 8 of sea water close to the CaO particle surface will immediately increase to a theoretical value of about 12.5 but will, in an open system with large excess of sea water, rapidly fall back to pH 10.5 being equilibrium pH of magnesium hydroxide. This is further reduced to <9 due to the common ion effect of dissolved magnesium in sea water and then be diluted to the sea water background pH, about 8. Field test dosing CaO particles to sea water showed that the pH of water between the particles stayed around 8

Transformation Kinetics of Burnt Lime in Freshwater and Sea Water

Calcium oxide (CaO), also known as burnt lime, is being considered as a possible treatment to reduce the negative impact of sea urchins on tare forests in northern coastal waters and blue-green algal blooms in the surrounding of fish-farms. In this respect, the reaction kinetics of burnt lime in contact with sea water has been elucidated and compared to its behaviour in fresh water. In the first minutes of contact between burnt lime and water, it “slaked” as CaO reacted with water to yield calcium hydroxide (Ca(OH)2). Subsequently, calcium hydroxide reacted with magnesium, sulphate and carbonate from the sea water to yield magnesium hydroxide (Mg(OH)2), calcium sulphate dihydrate (gypsum, CaSO4·2H2O) and calcium carbonate (CaCO3), respectively. In a closed system of 1% CaO in natural sea water (where the supply of sulphate, magnesium and carbonate is limited), more than 90% reacted within the first 5 h. It is foreseen that in an open system, like a marine fjord, it will react even faster. The pH 8 of sea water close to the CaO particle surface will immediately increase to a theoretical value of about 12.5 but will, in an open system with large excess of sea water, rapidly fall back to pH 10.5 being equilibrium pH of magnesium hydroxide. This is further reduced to <9 due to the common ion effect of dissolved magnesium in sea water and then be diluted to the sea water background pH, about 8. Field test dosing CaO particles to sea water showed that the pH of water between the particles stayed around 8

Optimizing the use of quicklime (CaO) for sea urchin management — A lab and field study

Mass blooms of sea urchins sometimes cause kelp forest collapses that can last for decades. Quicklime has historically been used to reverse those conditions, but the efficacy of liming has varied along latitudinal and temperature gradients for reasons that are not fully understood. To evaluate the feasibility and ecological impacts of liming in a high latitude area in Northern Norway (70°N), we conducted a field pilot study in 2008–2011, a follow-up lab study in 2017, and a further field study in 2018–2019, with the latter evaluating and implementing the previous results in a site high in refuges. It was found that liming can reduce sea urchin densities sufficiently for macroalgal revegetation to occur, and that the mobile fauna species richness and abundance increased in the re-vegetated in comparison to the barren control fields. Also, the remaining sea urchins in the treated fields increased their roe content to commercial levels after 2 years

Optimizing the use of quicklime (CaO) for sea urchin management — A lab and field study

Mass blooms of sea urchins sometimes cause kelp forest collapses that can last for decades. Quicklime has historically been used to reverse those conditions, but the efficacy of liming has varied along latitudinal and temperature gradients for reasons that are not fully understood. To evaluate the feasibility and ecological impacts of liming in a high latitude area in Northern Norway (70°N), we conducted a field pilot study in 2008–2011, a follow-up lab study in 2017, and a further field study in 2018–2019, with the latter evaluating and implementing the previous results in a site high in refuges. It was found that liming can reduce sea urchin densities sufficiently for macroalgal revegetation to occur, and that the mobile fauna species richness and abundance increased in the re-vegetated in comparison to the barren control fields. Also, the remaining sea urchins in the treated fields increased their roe content to commercial levels after 2 years. The lab experiments in 2017 indicated that the liming method is season/temperature-independent, as mortality remained at the same level irrespective of whether treatment started in the spring, when the sea temperatures were 2 °C, or in autumn when the temperatures were closer to 10 °C. The most important factor in treatment efficacy in the lab was particle size. With similar doses, the particles in the smallest size range (0–0.5 mm) caused 100% mortality, while the 0.5–2 mm and 2–4 mm fractions caused only 13% and 2% mortality respectively. In 2018–2019 we tested the fine CaO fraction (0.1–0.6 mm) and the medium fraction (0.5–2 mm) in a field experiment in areas characterized by high levels of refuges. Within 11 days, the sea urchin densities in the three fields treated with the fine lime were reduced to levels that theoretically should allow revegetation, but only in one of those fields was that potential partly realized after 1 year. The lack of effect in the two other fields was probably due to urchins protected by the substrate during treatment reappearing in sufficient numbers to prevent macroalgal regrowth, demonstrating that CaO treatment can be less effective on substrates where part of the sea urchin population hides among stones. Of the three variables held up as potential explanations for the different effects of CaO treatment in previous studies, we conclude based on our experiments that the presence of refuges and particle size were probably more important than temperature. Further improvements for larger scale treatments are discussed