Macrocystis pyrifera is a major habitat forming kelp in coastal ecosystems of temperate regions o... more Macrocystis pyrifera is a major habitat forming kelp in coastal ecosystems of temperate regions of the northern and southern hemispheres. We investigated the seasonal occurrence of adult sporophytes, morphological characteristics, and reproductive phenology at two sites within a wave‐protected harbour and two wave‐exposed sites in southern New Zealand every 3–4 months between 2012 and 2013. Seasonality in reproduction was assessed via the number of sporophylls, the occurrence of sori on sporophylls, and non‐sporophyllous laminae (fertile pneumatocyst‐bearing blades and fertile apical scimitars), meiospore release, and germination. We found that M. pyrifera was present and reproductive year‐round in three of the four sites, and patterns were similar for the wave‐exposure conditions. Sori were found on pneumatocyst‐bearing blades and apical scimitars in addition to the sporophylls, and viable meiospores were released from all three types of laminae. Morphological variations between sites with different wave exposure indicate that sporophytes from wave‐protected sites have bigger blades and holdfasts and are longer than those from wave‐exposed sites. We discuss the implications of these biological variables for the ecology of M. pyrifera inhabiting different wave exposure environments in southern New Zealand.
Macrocystis pyrifera is a major habitat forming kelp in coastal ecosystems of temperate regions o... more Macrocystis pyrifera is a major habitat forming kelp in coastal ecosystems of temperate regions of the northern and southern hemispheres. We investigated the seasonal occurrence of adult sporophytes, morphological characteristics, and reproductive phenology at two sites within a wave‐protected harbour and two wave‐exposed sites in southern New Zealand every 3–4 months between 2012 and 2013. Seasonality in reproduction was assessed via the number of sporophylls, the occurrence of sori on sporophylls, and non‐sporophyllous laminae (fertile pneumatocyst‐bearing blades and fertile apical scimitars), meiospore release, and germination. We found that M. pyrifera was present and reproductive year‐round in three of the four sites, and patterns were similar for the wave‐exposure conditions. Sori were found on pneumatocyst‐bearing blades and apical scimitars in addition to the sporophylls, and viable meiospores were released from all three types of laminae. Morphological variations between sites with different wave exposure indicate that sporophytes from wave‐protected sites have bigger blades and holdfasts and are longer than those from wave‐exposed sites. We discuss the implications of these biological variables for the ecology of M. pyrifera inhabiting different wave exposure environments in southern New Zealand.
The responses of macroalgae to ocean acidification could be altered by availability of macronutri... more The responses of macroalgae to ocean acidification could be altered by availability of macronutrients, such as ammonium (NH4+). This study determined how the opportunistic macroalga, Ulva australis responded to simultaneous changes in decreasing pH and NH4+ enrichment. This was investigated in a week-long growth experiment across a range of predicted future pHs with ambient and enriched NH4+ treatments followed by measurements of relative growth rates (RGR), NH4+ uptake rates and pools, total chlorophyll, and tissue carbon and nitrogen content. Rapid light curves (RLCs) were used to measure the maximum relative electron transport rate (rETRmax) and maximum quantum yield of photosystem II (PSII) photochemistry (Fv/Fm). Photosynthetic capacity was derived from the RLCs and included the efficiency of light harvesting (α), slope of photoinhibition (β), and the light saturation point (Ek). The results showed that NH4+ enrichment did not modify the effects of pH on RGRs, NH4+ uptake rates...
Finfish aquaculture is an activity that has experienced an explosive global development, but pres... more Finfish aquaculture is an activity that has experienced an explosive global development, but presents several environmental risks, such as high nitrogen outputs with potential eutrophication consequences. Therefore, the integration of seaweed aquaculture with the aim of decreasing nitrogen emissions associated with intensive salmon farming has been proposed as a bioremediation solution. Ecophysiological knowledge about seaweeds cultured close to farming cages is, however, still rudimentary. We experimentally studied the growth and physiological responses of Macrocystis pyrifera (Linnaeus) C. Agardh in a suspended culture system near a commercial salmon farm at three culture depths in order to understand its productivity performance. The results showed maximum growth responses at intermediate depths (3 m) as opposed to near the surface (1 m) or at a deeper culture level (6 m). At 6 m depth, light limitations were detected, whereas the sporophytes growing at 1 m depth responded to hig...
AbstractAnthropogenic atmospheric emissions of CO2 are responsible for simultaneous ocean warming... more AbstractAnthropogenic atmospheric emissions of CO2 are responsible for simultaneous ocean warming (OW) and ocean acidification (OA). These global events can have important impacts on marine fleshy macroalgae and coastal ecosystems. To understand the effects of OW and OA on the early life history stages of native (Macrocystis pyrifera) and invasive (Undaria pinnatifida) macroalgae, a multi-factorial experiment was performed to determine the independent and interactive effects of the drivers and the corresponding species-specific responses. Meiospores of M. pyrifera and U. pinnatifida were separately exposed to a 4 × 2 factorial design of seawater pH (pHT 7.20, extreme OA predicted for 2300; pHT 7.65, OA predicted for 2100; pHT 8.03, ambient pH; and pHT 8.40, pre-industrial pH) and temperature (12 °C, seasonal average temperature; and 16 °C, OW predicted for 2100). Over 15 days, different physiological parameters (i.e. meiospore germination, germling growth rate, gametophyte development and sex ratio) were measured. Reduced seawater pH and elevated temperature had independent and significant effects on developmental processes (germling growth rate, and male and female gametophyte sizes were independently greater under OA and OW conditions), but the interaction of the abiotic factors had no effect on any stage of meiospore development of either species. Despite some small differences between species (e.g. sex ratio), results of this experiment suggest that microscopic stages of the native M. pyrifera and the invasive U. pinnatifida will respond similarly to OA and OW.
Abstract: Copper in low natural concentrations is essential for cell metabolism but in excess it ... more Abstract: Copper in low natural concentrations is essential for cell metabolism but in excess it becomes extremely toxic to aquatic life, including to the early life stages of marine macroalgae. This work determined the effects of copper exposure on meiospore development of two kelp species, the native Macrocystis pyrifera and invasive Undaria pinnatifida. After settlement, meiospores were exposed to nominal copper concentrations of control (no added copper), 100, 200, 300 and 400 μg L−1 Cu for 9 days. Inductively coupled plasma mass spectrometry of total dissolved copper (CuT) concentrations in the blanks showed that nominal copper concentrations were reduced to 54, 91, 131 and 171 μg L−1 CuT, respectively, indicating that > 50% of the dissolved copper was adsorbed onto the culture vessel walls. In the media with meiospores, the dissolved copper concentrations decreased to 39, 86, 97 and 148 μg L−1 CuT in M. pyrifera and to 39, 65, 97 and 146 μg L−1 CuT in U. pinnatifida, indicating that 6–15% of the dissolved copper was adsorbed by the cells. For both species, meiospores germinated in all copper treatments, with germination decreasing with increasing copper concentration. However, gametophyte growth and sexual differentiation were arrested under all copper treatments. The effective copper concentration causing 50% of arrested germination (Cu-EC50) was 157 and 231 μg L−1 CuT for M. pyrifera and U. pinnatifida, respectively. The higher Cu-EC50 for U. pinnatifida suggests ecological success for the invasive species in copper-polluted environments; however, the subsequent inhibition of gametogenesis under all copper treatments indicated no difference in copper tolerance between both kelp early life stages. We compare our results with the literature available on the effects of copper on the development of early life stages of brown seaweed (Laminariales and Fucales) and discuss the importance of reporting actual experimental dissolved copper concentrations and the necessity of standardizing the response variables measured in macroalgal copper ecotoxicology.
Different lamina of Macrocystis pyrifera sporophytes (i.e., sporophylls, pneumatocyst-bearing bla... more Different lamina of Macrocystis pyrifera sporophytes (i.e., sporophylls, pneumatocyst-bearing blades, and apical scimitars) in a wave-sheltered site were found to be fertile. We quantified their sorus surface area, reproductive output (number of spores released) and the viability of released spores (germination rate). Sorus area was greatest on the sporophylls, with sporangia developing on >57% of the total area and smallest on the pneumatocyst-bearing blades with 21% of the total area bearing sporangia. The apical scimitar released the greatest number of meiospores (cells · mL(-1) · cm(-2) ) and the sporophylls the least. Meiospores produced from all types of fertile laminae were equally viable. This reproductive plasticity may enhance reproductive output, and contribute to short and long-distance spore dispersal and the cryptic gametophyte propagule bank for the next generation of sporophytes.
Ocean warming (OW), ocean acidification (OA) and their interaction with local drivers, e.g., copp... more Ocean warming (OW), ocean acidification (OA) and their interaction with local drivers, e.g., copper pollution, may negatively affect macroalgae and their microscopic life stages. We evaluated meiospore development of the kelps Macrocystis pyrifera and Undaria pinnatifida exposed to a factorial combination of current and 2100-predicted temperature (12 and 16 °C, respectively), pH (8.16 and 7.65, respectively), and two copper levels (no-added-copper and species-specific germination Cu-EC). Meiospore germination for both species declined by 5-18% under OA and ambient temperature/OA conditions, irrespective of copper exposure. Germling growth rate declined by >40%·day, and gametophyte development was inhibited under Cu-EC exposure, compared to the no-added-copper treatment, irrespective of pH and temperature. Following the removal of copper and 9-day recovery under respective pH and temperature treatments, germling growth rates increased by 8-18%·day. The exception was U. pinnatifida...
Anthropogenic atmospheric emissions of CO2 are responsible for simultaneous ocean warming (OW) an... more Anthropogenic atmospheric emissions of CO2 are responsible for simultaneous ocean warming (OW) and ocean acidification (OA). These global events can have important impacts on marine fleshy macroalgae and coastal ecosystems. To understand the effects of OW and OA on the early life history stages of native (Macrocystis pyrifera) and invasive (Undaria pinnatifida) macroalgae, a multi-factorial experiment was performed to determine the independent and interactive effects of the drivers and the corresponding species-specific responses. Meiospores of M. pyrifera and U. pinnatifida were separately exposed to a 4 × 2 factorial design of seawater pH (pHT 7.20, extreme OA predicted for 2300; pHT 7.65, OA predicted for 2100; pHT 8.03, ambient pH; and pHT 8.40, pre-industrial pH) and temperature (12 °C, seasonal average temperature; and 16 °C, OW predicted for 2100). Over 15 days, different physiological parameters (i.e. meiospore germination, germling growth rate, gametophyte development and sex ratio) were measured. Reduced seawater pH and elevated temperature had independent and significant effects on developmental processes (germling growth rate, and male and female gametophyte sizes were independently greater under OA and OW conditions), but the interaction of the abiotic factors had no effect on any stage of meiospore development of either species. Despite some small differences between species (e.g. sex ratio), results of this experiment suggest that microscopic stages of the native M. pyrifera and the invasive U. pinnatifida will respond similarly to OA and OW.
Ocean acidification (OA), the ongoing decline in seawater pH, is redicted to have wide-ranging ef... more Ocean acidification (OA), the ongoing decline in seawater pH, is redicted to have wide-ranging effects on marine organisms and ecosystems. For seaweeds, the pHat the thallus surface, within the diffusion boundary layer (DBL), is one of the factors controlling their response to OA. Surface pH is controlled by both the pH of the bulk seawater and by the seaweeds’ metabolism: photosynthesis and respiration increase and decrease pH within the DBL (pHDBL), respectively. However, other metabolic processes, especially the uptake of inorganic nitrogen (Ni; NO3− and NH4+) may also affect the pHDBL. Using Macrocystis pyrifera, we hypothesized that (1) NO3− uptake will increase the pHDBL, whereas NH4+ uptake will decrease it, (2) if NO3− is cotransported with H+, increases in pHDBL would be greater under an OA treatment (pH=7.65) than under an ambient treatment (pH=8.00), and (3) decreases in pHDBL will be smaller at pH 7.65 than at pH 8.00, as higher external [H+] might affect the strength of the diffusion gradient. Overall, Ni source did not affect the pHDBL. However, increases in pHDBL were greater at pH 7.65 than at pH 8.00. CO2 uptake was higher at pH 7.65 than at pH 8.00, whereas HCO3− uptake was unaffected by pH. Photosynthesis and respiration control pHDBL rather than Ni uptake. We suggest that under future OA, Macrocystis pyrifera will metabolically modify its surface microenvironment such that the physiological processes of photosynthesis and Ni uptake will not be affected by a reduced pH.
The production of accurate and reliable data on copper ecotoxicology of marine algae depends on t... more The production of accurate and reliable data on copper ecotoxicology of marine algae depends on the use of trace metal clean techniques during experimentation. We reviewed the methodologies used in the literature on copper ecotoxicology of marine macro- and microalgae, specifically the use of trace metal clean procedures such as the labware used (glassware vs plasticware), methods of cleaning the labware (acid soaking and ultrapure water rinsing), stock solution preparation (copper source and acidification), and measurement and reporting of dissolved copper concentrations. In terms of taxonomic classification, the most studied algal groups were the Phyla Ochrophyta, Bacillariophyta, Rhodophyta and Chlorophyta. In terms of methodology, ~50% of the articles did not specify the labware, ~25% used glassware and ~25% plasticware; ~30% of the studies specified cleaning protocols for labware to remove trace metal impurities; the copper form used to prepare the stock solutions was specified in ~80% of studies but acidification to stabilize the dissolved copper was performed in only ~20%; and the dissolved copper concentration was measured in only ~40% of studies. We discuss the importance of following trace metal clean techniques for the comparison and interpretation of data obtained on copper ecotoxicology in algae.
Copper in low natural concentrations is essential for cell metabolism but in excess it becomes ex... more Copper in low natural concentrations is essential for cell metabolism but in excess it becomes extremely toxic to aquatic life, including to the early life stages of marine macroalgae. This work determined the effects of copper exposure on meiospore development of two kelp species, the native Macrocystis pyrifera and invasive Undaria pinnatifida. After settlement, meiospores were exposed to nominal copper concentrations of control (no added copper), 100, 200, 300 and 400 μg L−1 Cu for 9 days. Inductively coupled plasma mass spectrometry of total dissolved copper (CuT) concentrations in the blanks showed that nominal copper concentrations were reduced to 54, 91, 131 and 171 μg L−1 CuT, respectively, indicating that > 50% of the dissolved copper was adsorbed onto the culture vessel walls. In the media with meiospores, the dissolved copper concentrations decreased to 39, 86, 97 and 148 μg L−1 CuT in M. pyrifera and to 39, 65, 97 and 146 μg L−1 CuT in U. pinnatifida, indicating that 6–15% of the dissolved copper was adsorbed by the cells. For both species, meiospores germinated in all copper treatments, with germination decreasing with increasing copper concentration. However, gametophyte growth and sexual differentiation were arrested under all copper treatments. The effective copper concentration causing 50% of arrested germination (Cu-EC50) was 157 and 231 μg L−1 CuT for M. pyrifera and U. pinnatifida, respectively. The higher Cu-EC50 for U. pinnatifida suggests ecological success for the invasive species in copper-polluted environments; however, the subsequent inhibition of gametogenesis under all copper treatments indicated no difference in copper tolerance between both kelp early life stages. We compare our results with the literature available on the effects of copper on the development of early life stages of brown seaweed (Laminariales and Fucales) and discuss the importance of reporting actual experimental dissolved copper concentrations and the necessity of standardizing the response variables measured in macroalgal copper ecotoxicology.
Macrocystis pyrifera is a major habitat forming kelp in coastal ecosystems of temperate regions o... more Macrocystis pyrifera is a major habitat forming kelp in coastal ecosystems of temperate regions of the northern and southern hemispheres. We investigated the seasonal occurrence of adult sporophytes, morphological characteristics, and reproductive phenology at two sites within a wave‐protected harbour and two wave‐exposed sites in southern New Zealand every 3–4 months between 2012 and 2013. Seasonality in reproduction was assessed via the number of sporophylls, the occurrence of sori on sporophylls, and non‐sporophyllous laminae (fertile pneumatocyst‐bearing blades and fertile apical scimitars), meiospore release, and germination. We found that M. pyrifera was present and reproductive year‐round in three of the four sites, and patterns were similar for the wave‐exposure conditions. Sori were found on pneumatocyst‐bearing blades and apical scimitars in addition to the sporophylls, and viable meiospores were released from all three types of laminae. Morphological variations between sites with different wave exposure indicate that sporophytes from wave‐protected sites have bigger blades and holdfasts and are longer than those from wave‐exposed sites. We discuss the implications of these biological variables for the ecology of M. pyrifera inhabiting different wave exposure environments in southern New Zealand.
Macrocystis pyrifera is a major habitat forming kelp in coastal ecosystems of temperate regions o... more Macrocystis pyrifera is a major habitat forming kelp in coastal ecosystems of temperate regions of the northern and southern hemispheres. We investigated the seasonal occurrence of adult sporophytes, morphological characteristics, and reproductive phenology at two sites within a wave‐protected harbour and two wave‐exposed sites in southern New Zealand every 3–4 months between 2012 and 2013. Seasonality in reproduction was assessed via the number of sporophylls, the occurrence of sori on sporophylls, and non‐sporophyllous laminae (fertile pneumatocyst‐bearing blades and fertile apical scimitars), meiospore release, and germination. We found that M. pyrifera was present and reproductive year‐round in three of the four sites, and patterns were similar for the wave‐exposure conditions. Sori were found on pneumatocyst‐bearing blades and apical scimitars in addition to the sporophylls, and viable meiospores were released from all three types of laminae. Morphological variations between sites with different wave exposure indicate that sporophytes from wave‐protected sites have bigger blades and holdfasts and are longer than those from wave‐exposed sites. We discuss the implications of these biological variables for the ecology of M. pyrifera inhabiting different wave exposure environments in southern New Zealand.
The responses of macroalgae to ocean acidification could be altered by availability of macronutri... more The responses of macroalgae to ocean acidification could be altered by availability of macronutrients, such as ammonium (NH4+). This study determined how the opportunistic macroalga, Ulva australis responded to simultaneous changes in decreasing pH and NH4+ enrichment. This was investigated in a week-long growth experiment across a range of predicted future pHs with ambient and enriched NH4+ treatments followed by measurements of relative growth rates (RGR), NH4+ uptake rates and pools, total chlorophyll, and tissue carbon and nitrogen content. Rapid light curves (RLCs) were used to measure the maximum relative electron transport rate (rETRmax) and maximum quantum yield of photosystem II (PSII) photochemistry (Fv/Fm). Photosynthetic capacity was derived from the RLCs and included the efficiency of light harvesting (α), slope of photoinhibition (β), and the light saturation point (Ek). The results showed that NH4+ enrichment did not modify the effects of pH on RGRs, NH4+ uptake rates...
Finfish aquaculture is an activity that has experienced an explosive global development, but pres... more Finfish aquaculture is an activity that has experienced an explosive global development, but presents several environmental risks, such as high nitrogen outputs with potential eutrophication consequences. Therefore, the integration of seaweed aquaculture with the aim of decreasing nitrogen emissions associated with intensive salmon farming has been proposed as a bioremediation solution. Ecophysiological knowledge about seaweeds cultured close to farming cages is, however, still rudimentary. We experimentally studied the growth and physiological responses of Macrocystis pyrifera (Linnaeus) C. Agardh in a suspended culture system near a commercial salmon farm at three culture depths in order to understand its productivity performance. The results showed maximum growth responses at intermediate depths (3 m) as opposed to near the surface (1 m) or at a deeper culture level (6 m). At 6 m depth, light limitations were detected, whereas the sporophytes growing at 1 m depth responded to hig...
AbstractAnthropogenic atmospheric emissions of CO2 are responsible for simultaneous ocean warming... more AbstractAnthropogenic atmospheric emissions of CO2 are responsible for simultaneous ocean warming (OW) and ocean acidification (OA). These global events can have important impacts on marine fleshy macroalgae and coastal ecosystems. To understand the effects of OW and OA on the early life history stages of native (Macrocystis pyrifera) and invasive (Undaria pinnatifida) macroalgae, a multi-factorial experiment was performed to determine the independent and interactive effects of the drivers and the corresponding species-specific responses. Meiospores of M. pyrifera and U. pinnatifida were separately exposed to a 4 × 2 factorial design of seawater pH (pHT 7.20, extreme OA predicted for 2300; pHT 7.65, OA predicted for 2100; pHT 8.03, ambient pH; and pHT 8.40, pre-industrial pH) and temperature (12 °C, seasonal average temperature; and 16 °C, OW predicted for 2100). Over 15 days, different physiological parameters (i.e. meiospore germination, germling growth rate, gametophyte development and sex ratio) were measured. Reduced seawater pH and elevated temperature had independent and significant effects on developmental processes (germling growth rate, and male and female gametophyte sizes were independently greater under OA and OW conditions), but the interaction of the abiotic factors had no effect on any stage of meiospore development of either species. Despite some small differences between species (e.g. sex ratio), results of this experiment suggest that microscopic stages of the native M. pyrifera and the invasive U. pinnatifida will respond similarly to OA and OW.
Abstract: Copper in low natural concentrations is essential for cell metabolism but in excess it ... more Abstract: Copper in low natural concentrations is essential for cell metabolism but in excess it becomes extremely toxic to aquatic life, including to the early life stages of marine macroalgae. This work determined the effects of copper exposure on meiospore development of two kelp species, the native Macrocystis pyrifera and invasive Undaria pinnatifida. After settlement, meiospores were exposed to nominal copper concentrations of control (no added copper), 100, 200, 300 and 400 μg L−1 Cu for 9 days. Inductively coupled plasma mass spectrometry of total dissolved copper (CuT) concentrations in the blanks showed that nominal copper concentrations were reduced to 54, 91, 131 and 171 μg L−1 CuT, respectively, indicating that > 50% of the dissolved copper was adsorbed onto the culture vessel walls. In the media with meiospores, the dissolved copper concentrations decreased to 39, 86, 97 and 148 μg L−1 CuT in M. pyrifera and to 39, 65, 97 and 146 μg L−1 CuT in U. pinnatifida, indicating that 6–15% of the dissolved copper was adsorbed by the cells. For both species, meiospores germinated in all copper treatments, with germination decreasing with increasing copper concentration. However, gametophyte growth and sexual differentiation were arrested under all copper treatments. The effective copper concentration causing 50% of arrested germination (Cu-EC50) was 157 and 231 μg L−1 CuT for M. pyrifera and U. pinnatifida, respectively. The higher Cu-EC50 for U. pinnatifida suggests ecological success for the invasive species in copper-polluted environments; however, the subsequent inhibition of gametogenesis under all copper treatments indicated no difference in copper tolerance between both kelp early life stages. We compare our results with the literature available on the effects of copper on the development of early life stages of brown seaweed (Laminariales and Fucales) and discuss the importance of reporting actual experimental dissolved copper concentrations and the necessity of standardizing the response variables measured in macroalgal copper ecotoxicology.
Different lamina of Macrocystis pyrifera sporophytes (i.e., sporophylls, pneumatocyst-bearing bla... more Different lamina of Macrocystis pyrifera sporophytes (i.e., sporophylls, pneumatocyst-bearing blades, and apical scimitars) in a wave-sheltered site were found to be fertile. We quantified their sorus surface area, reproductive output (number of spores released) and the viability of released spores (germination rate). Sorus area was greatest on the sporophylls, with sporangia developing on >57% of the total area and smallest on the pneumatocyst-bearing blades with 21% of the total area bearing sporangia. The apical scimitar released the greatest number of meiospores (cells · mL(-1) · cm(-2) ) and the sporophylls the least. Meiospores produced from all types of fertile laminae were equally viable. This reproductive plasticity may enhance reproductive output, and contribute to short and long-distance spore dispersal and the cryptic gametophyte propagule bank for the next generation of sporophytes.
Ocean warming (OW), ocean acidification (OA) and their interaction with local drivers, e.g., copp... more Ocean warming (OW), ocean acidification (OA) and their interaction with local drivers, e.g., copper pollution, may negatively affect macroalgae and their microscopic life stages. We evaluated meiospore development of the kelps Macrocystis pyrifera and Undaria pinnatifida exposed to a factorial combination of current and 2100-predicted temperature (12 and 16 °C, respectively), pH (8.16 and 7.65, respectively), and two copper levels (no-added-copper and species-specific germination Cu-EC). Meiospore germination for both species declined by 5-18% under OA and ambient temperature/OA conditions, irrespective of copper exposure. Germling growth rate declined by >40%·day, and gametophyte development was inhibited under Cu-EC exposure, compared to the no-added-copper treatment, irrespective of pH and temperature. Following the removal of copper and 9-day recovery under respective pH and temperature treatments, germling growth rates increased by 8-18%·day. The exception was U. pinnatifida...
Anthropogenic atmospheric emissions of CO2 are responsible for simultaneous ocean warming (OW) an... more Anthropogenic atmospheric emissions of CO2 are responsible for simultaneous ocean warming (OW) and ocean acidification (OA). These global events can have important impacts on marine fleshy macroalgae and coastal ecosystems. To understand the effects of OW and OA on the early life history stages of native (Macrocystis pyrifera) and invasive (Undaria pinnatifida) macroalgae, a multi-factorial experiment was performed to determine the independent and interactive effects of the drivers and the corresponding species-specific responses. Meiospores of M. pyrifera and U. pinnatifida were separately exposed to a 4 × 2 factorial design of seawater pH (pHT 7.20, extreme OA predicted for 2300; pHT 7.65, OA predicted for 2100; pHT 8.03, ambient pH; and pHT 8.40, pre-industrial pH) and temperature (12 °C, seasonal average temperature; and 16 °C, OW predicted for 2100). Over 15 days, different physiological parameters (i.e. meiospore germination, germling growth rate, gametophyte development and sex ratio) were measured. Reduced seawater pH and elevated temperature had independent and significant effects on developmental processes (germling growth rate, and male and female gametophyte sizes were independently greater under OA and OW conditions), but the interaction of the abiotic factors had no effect on any stage of meiospore development of either species. Despite some small differences between species (e.g. sex ratio), results of this experiment suggest that microscopic stages of the native M. pyrifera and the invasive U. pinnatifida will respond similarly to OA and OW.
Ocean acidification (OA), the ongoing decline in seawater pH, is redicted to have wide-ranging ef... more Ocean acidification (OA), the ongoing decline in seawater pH, is redicted to have wide-ranging effects on marine organisms and ecosystems. For seaweeds, the pHat the thallus surface, within the diffusion boundary layer (DBL), is one of the factors controlling their response to OA. Surface pH is controlled by both the pH of the bulk seawater and by the seaweeds’ metabolism: photosynthesis and respiration increase and decrease pH within the DBL (pHDBL), respectively. However, other metabolic processes, especially the uptake of inorganic nitrogen (Ni; NO3− and NH4+) may also affect the pHDBL. Using Macrocystis pyrifera, we hypothesized that (1) NO3− uptake will increase the pHDBL, whereas NH4+ uptake will decrease it, (2) if NO3− is cotransported with H+, increases in pHDBL would be greater under an OA treatment (pH=7.65) than under an ambient treatment (pH=8.00), and (3) decreases in pHDBL will be smaller at pH 7.65 than at pH 8.00, as higher external [H+] might affect the strength of the diffusion gradient. Overall, Ni source did not affect the pHDBL. However, increases in pHDBL were greater at pH 7.65 than at pH 8.00. CO2 uptake was higher at pH 7.65 than at pH 8.00, whereas HCO3− uptake was unaffected by pH. Photosynthesis and respiration control pHDBL rather than Ni uptake. We suggest that under future OA, Macrocystis pyrifera will metabolically modify its surface microenvironment such that the physiological processes of photosynthesis and Ni uptake will not be affected by a reduced pH.
The production of accurate and reliable data on copper ecotoxicology of marine algae depends on t... more The production of accurate and reliable data on copper ecotoxicology of marine algae depends on the use of trace metal clean techniques during experimentation. We reviewed the methodologies used in the literature on copper ecotoxicology of marine macro- and microalgae, specifically the use of trace metal clean procedures such as the labware used (glassware vs plasticware), methods of cleaning the labware (acid soaking and ultrapure water rinsing), stock solution preparation (copper source and acidification), and measurement and reporting of dissolved copper concentrations. In terms of taxonomic classification, the most studied algal groups were the Phyla Ochrophyta, Bacillariophyta, Rhodophyta and Chlorophyta. In terms of methodology, ~50% of the articles did not specify the labware, ~25% used glassware and ~25% plasticware; ~30% of the studies specified cleaning protocols for labware to remove trace metal impurities; the copper form used to prepare the stock solutions was specified in ~80% of studies but acidification to stabilize the dissolved copper was performed in only ~20%; and the dissolved copper concentration was measured in only ~40% of studies. We discuss the importance of following trace metal clean techniques for the comparison and interpretation of data obtained on copper ecotoxicology in algae.
Copper in low natural concentrations is essential for cell metabolism but in excess it becomes ex... more Copper in low natural concentrations is essential for cell metabolism but in excess it becomes extremely toxic to aquatic life, including to the early life stages of marine macroalgae. This work determined the effects of copper exposure on meiospore development of two kelp species, the native Macrocystis pyrifera and invasive Undaria pinnatifida. After settlement, meiospores were exposed to nominal copper concentrations of control (no added copper), 100, 200, 300 and 400 μg L−1 Cu for 9 days. Inductively coupled plasma mass spectrometry of total dissolved copper (CuT) concentrations in the blanks showed that nominal copper concentrations were reduced to 54, 91, 131 and 171 μg L−1 CuT, respectively, indicating that > 50% of the dissolved copper was adsorbed onto the culture vessel walls. In the media with meiospores, the dissolved copper concentrations decreased to 39, 86, 97 and 148 μg L−1 CuT in M. pyrifera and to 39, 65, 97 and 146 μg L−1 CuT in U. pinnatifida, indicating that 6–15% of the dissolved copper was adsorbed by the cells. For both species, meiospores germinated in all copper treatments, with germination decreasing with increasing copper concentration. However, gametophyte growth and sexual differentiation were arrested under all copper treatments. The effective copper concentration causing 50% of arrested germination (Cu-EC50) was 157 and 231 μg L−1 CuT for M. pyrifera and U. pinnatifida, respectively. The higher Cu-EC50 for U. pinnatifida suggests ecological success for the invasive species in copper-polluted environments; however, the subsequent inhibition of gametogenesis under all copper treatments indicated no difference in copper tolerance between both kelp early life stages. We compare our results with the literature available on the effects of copper on the development of early life stages of brown seaweed (Laminariales and Fucales) and discuss the importance of reporting actual experimental dissolved copper concentrations and the necessity of standardizing the response variables measured in macroalgal copper ecotoxicology.
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Papers by Pablo Leal
the pHDBL, whereas NH4+ uptake will decrease it, (2) if NO3− is cotransported with H+, increases in pHDBL would be greater under an OA treatment (pH=7.65) than under an ambient treatment (pH=8.00), and (3) decreases in pHDBL will be smaller at pH 7.65 than at pH 8.00, as higher external [H+] might affect the strength of the diffusion gradient. Overall, Ni source did not affect the pHDBL. However, increases in pHDBL were greater at pH 7.65 than at pH 8.00. CO2 uptake was higher at pH 7.65 than at pH 8.00, whereas HCO3−
uptake was unaffected by pH. Photosynthesis and respiration control pHDBL rather than Ni uptake. We suggest that under future OA, Macrocystis pyrifera will metabolically modify its surface microenvironment such that the physiological processes of photosynthesis and Ni uptake will not be affected by a reduced pH.
the pHDBL, whereas NH4+ uptake will decrease it, (2) if NO3− is cotransported with H+, increases in pHDBL would be greater under an OA treatment (pH=7.65) than under an ambient treatment (pH=8.00), and (3) decreases in pHDBL will be smaller at pH 7.65 than at pH 8.00, as higher external [H+] might affect the strength of the diffusion gradient. Overall, Ni source did not affect the pHDBL. However, increases in pHDBL were greater at pH 7.65 than at pH 8.00. CO2 uptake was higher at pH 7.65 than at pH 8.00, whereas HCO3−
uptake was unaffected by pH. Photosynthesis and respiration control pHDBL rather than Ni uptake. We suggest that under future OA, Macrocystis pyrifera will metabolically modify its surface microenvironment such that the physiological processes of photosynthesis and Ni uptake will not be affected by a reduced pH.