Physical oceanography measured at three station in Potter cove, Western Antarctic Peninsula. This... more Physical oceanography measured at three station in Potter cove, Western Antarctic Peninsula. This data collection gives the yearly measurements from 1991 to 2012.
Abstract Light and temperature demands for photosynthesis and growth of two benthic diatoms from ... more Abstract Light and temperature demands for photosynthesis and growth of two benthic diatoms from Potter Cove, a shallow bay in King George Island, South Shetland Islands (Antarctica), were determined in laboratory cultures. The species investigated were Gyrosigma subsalinum var. antarctica and the Antarctic endemic Odontella litigiosa. The algae exhibited different light requirements for growth and photosynthesis. G. subsalinum was adapted to low light conditions, with a high light utilisation coefficient (α) and low saturating photon irradiances for photosynthesis and growth (~25 μmol m−2 s−1 and 11 μmol m−2 s−1, respectively). Photosynthesis and growth in O. litigiosa were saturated at a photon irradiance of ~100 μmol m−2 s−1. Both benthic diatoms exhibited extremely low upper survival temperature (UST, 5–7 °C) and growth only occurred over a narrow range from 0 and 7 °C. Optimal temperature for growth (0 °C) was slightly lower than optimum temperature for photosynthesis (5 °C). The results suggest that G. subsalinum is well-adapted to the low light and constant low temperature conditions present in water depths below 10 m where it occurs. In contrast, O. litigiosa requires more light and is able to tolerate the higher temperatures typical of shallow waters and tide pools. The northern distribution limit of G. subsalinum is the 4 °C summer isotherm, i.e. at the northern boundary of the Antarctic region. In contrast, O. litigiosa could potentially also occur in the sub-Antarctic region up to the 7 °C summer isotherm.
We present the final 15 issues below in thematic groups identified post-scoring, rather than rank... more We present the final 15 issues below in thematic groups identified post-scoring, rather than rank order (Fig. 1). Ecosystem impacts. Wildfire impacts on coastal and marine ecosystems. The frequency and severity of wildfires are increasing with climate change 7. Since 2017, there have been fires of unprecedented scale and duration in Australia, Brazil, Portugal, Russia and along the Pacific coast of North America. In addition to threatening human life and releasing stored carbon, wildfires release aerosols, particles and large volumes of materials containing soluble forms of nutrients including nitrogen, phosphorus and trace metals such as copper, lead and iron. Winds and rains can transport these materials over long distances to reach coastal and marine ecosystems.
FOR DOWNLOAD THE COMPLETE FILE PLEASE USE THE "OTHER VERSION".363322 values, 1037 CTD p... more FOR DOWNLOAD THE COMPLETE FILE PLEASE USE THE "OTHER VERSION".363322 values, 1037 CTD profiles (Conductivity, Temperature & Density), salinity, voltage and pressure data compiled at 123 stations, spatially distribute in entire Potter Cove. Variable available: Coordinates of stations, depth sampling [m], water temperature [°C], potential temperature [°C], salinity [psu], density [kg/m^3], conductivity [mS/cm], turbidity [NTU], voltage [V], press [dbar].The depth has been classified into three categories 0-5 m; 5-15 m and over 15 m. 5 stations were monthly sampled: E1, E2, E3 (18, 17, 6 years, respectively); Faro and Peñon de Pesca (all months except June & July for 2 and 3 years, respectively). The other 118 stations belong to summer season only covering 1 to 5 years sampling. Transects for summer 1996/1997, 2007 and 2008 have been georeferenced and newly available. Device used: CTD/Rosette (CTD-RO).
Food web structure plays an important role in determining ecosystem stability against perturbatio... more Food web structure plays an important role in determining ecosystem stability against perturbations. High-latitude marine ecosystems are being affected by environmental stressors and biological invasions. In the West Antarctic Peninsula these transformations are mainly driven by climate change, while in the sub-Antarctic region by anthropogenic activities. Understanding the differences between these areas is necessary to monitor the changes that are expected to occur in the upcoming decades. Here, we compared the structure and stability of Antarctic (Potter Cove) and sub-Antarctic (Beagle Channel) marine food webs. We compiled species trophic interactions (predator-prey) and calculated complexity, structure and stability metrics. Even if both food webs presented the same connectance, we found important differences between them. The Beagle Channel food web is more complex, but less stable and sensitive to the loss of its most connected species, while the Potter Cove food web presented lower complexity and greater stability against perturbations.
Marine phytoplankton can utilize different strategies to cope with ocean warming and freshening f... more Marine phytoplankton can utilize different strategies to cope with ocean warming and freshening from glacial melting in polar regions, which are disproportionally impacted by global warming. In the present study, we investigated the individual and combined effects of a 4 °C increase in seawater temperature (T+) and a 4 psu decrease in salinity (S-) from ambient values on biomass, nutrient use, fatty acid composition and lipid damage biochemistry of natural phytoplankton assemblages from Potter Cove (25 de Mayo/King George Island, Antarctica). Experiments were conducted by exposing the assemblages to four treatments during a 7-day incubation period using microcosm located along shore from January 23 to 31, 2016. The N:P ratio decreased in all treatments from day 4 onwards, but especially under high temperature (T+). Lipid damage was mainly detected under S0T+ and S-T+ conditions, and it decreased when the production of the antioxidant α-tocopherol increased. This antioxidant protection resulted in a build-up of phytoplankton biomass, especially at T+. Under the combined effect of both stressors (S-T+), the concentration of ω3 fatty acids increased, potentially leading to higher-quality FA composition. These results, which were related to the dominance of sub-Antarctic species in phytoplankton assemblages, contribute to the understanding of the potential consequences of ocean warming and increase seawater freshening on the trophic webs of the Southern Ocean.
Physical oceanography measured at three station in Potter cove, Western Antarctic Peninsula. This... more Physical oceanography measured at three station in Potter cove, Western Antarctic Peninsula. This data collection gives the yearly measurements from 1991 to 2012.
Abstract Light and temperature demands for photosynthesis and growth of two benthic diatoms from ... more Abstract Light and temperature demands for photosynthesis and growth of two benthic diatoms from Potter Cove, a shallow bay in King George Island, South Shetland Islands (Antarctica), were determined in laboratory cultures. The species investigated were Gyrosigma subsalinum var. antarctica and the Antarctic endemic Odontella litigiosa. The algae exhibited different light requirements for growth and photosynthesis. G. subsalinum was adapted to low light conditions, with a high light utilisation coefficient (α) and low saturating photon irradiances for photosynthesis and growth (~25 μmol m−2 s−1 and 11 μmol m−2 s−1, respectively). Photosynthesis and growth in O. litigiosa were saturated at a photon irradiance of ~100 μmol m−2 s−1. Both benthic diatoms exhibited extremely low upper survival temperature (UST, 5–7 °C) and growth only occurred over a narrow range from 0 and 7 °C. Optimal temperature for growth (0 °C) was slightly lower than optimum temperature for photosynthesis (5 °C). The results suggest that G. subsalinum is well-adapted to the low light and constant low temperature conditions present in water depths below 10 m where it occurs. In contrast, O. litigiosa requires more light and is able to tolerate the higher temperatures typical of shallow waters and tide pools. The northern distribution limit of G. subsalinum is the 4 °C summer isotherm, i.e. at the northern boundary of the Antarctic region. In contrast, O. litigiosa could potentially also occur in the sub-Antarctic region up to the 7 °C summer isotherm.
We present the final 15 issues below in thematic groups identified post-scoring, rather than rank... more We present the final 15 issues below in thematic groups identified post-scoring, rather than rank order (Fig. 1). Ecosystem impacts. Wildfire impacts on coastal and marine ecosystems. The frequency and severity of wildfires are increasing with climate change 7. Since 2017, there have been fires of unprecedented scale and duration in Australia, Brazil, Portugal, Russia and along the Pacific coast of North America. In addition to threatening human life and releasing stored carbon, wildfires release aerosols, particles and large volumes of materials containing soluble forms of nutrients including nitrogen, phosphorus and trace metals such as copper, lead and iron. Winds and rains can transport these materials over long distances to reach coastal and marine ecosystems.
FOR DOWNLOAD THE COMPLETE FILE PLEASE USE THE "OTHER VERSION".363322 values, 1037 CTD p... more FOR DOWNLOAD THE COMPLETE FILE PLEASE USE THE "OTHER VERSION".363322 values, 1037 CTD profiles (Conductivity, Temperature & Density), salinity, voltage and pressure data compiled at 123 stations, spatially distribute in entire Potter Cove. Variable available: Coordinates of stations, depth sampling [m], water temperature [°C], potential temperature [°C], salinity [psu], density [kg/m^3], conductivity [mS/cm], turbidity [NTU], voltage [V], press [dbar].The depth has been classified into three categories 0-5 m; 5-15 m and over 15 m. 5 stations were monthly sampled: E1, E2, E3 (18, 17, 6 years, respectively); Faro and Peñon de Pesca (all months except June & July for 2 and 3 years, respectively). The other 118 stations belong to summer season only covering 1 to 5 years sampling. Transects for summer 1996/1997, 2007 and 2008 have been georeferenced and newly available. Device used: CTD/Rosette (CTD-RO).
Food web structure plays an important role in determining ecosystem stability against perturbatio... more Food web structure plays an important role in determining ecosystem stability against perturbations. High-latitude marine ecosystems are being affected by environmental stressors and biological invasions. In the West Antarctic Peninsula these transformations are mainly driven by climate change, while in the sub-Antarctic region by anthropogenic activities. Understanding the differences between these areas is necessary to monitor the changes that are expected to occur in the upcoming decades. Here, we compared the structure and stability of Antarctic (Potter Cove) and sub-Antarctic (Beagle Channel) marine food webs. We compiled species trophic interactions (predator-prey) and calculated complexity, structure and stability metrics. Even if both food webs presented the same connectance, we found important differences between them. The Beagle Channel food web is more complex, but less stable and sensitive to the loss of its most connected species, while the Potter Cove food web presented lower complexity and greater stability against perturbations.
Marine phytoplankton can utilize different strategies to cope with ocean warming and freshening f... more Marine phytoplankton can utilize different strategies to cope with ocean warming and freshening from glacial melting in polar regions, which are disproportionally impacted by global warming. In the present study, we investigated the individual and combined effects of a 4 °C increase in seawater temperature (T+) and a 4 psu decrease in salinity (S-) from ambient values on biomass, nutrient use, fatty acid composition and lipid damage biochemistry of natural phytoplankton assemblages from Potter Cove (25 de Mayo/King George Island, Antarctica). Experiments were conducted by exposing the assemblages to four treatments during a 7-day incubation period using microcosm located along shore from January 23 to 31, 2016. The N:P ratio decreased in all treatments from day 4 onwards, but especially under high temperature (T+). Lipid damage was mainly detected under S0T+ and S-T+ conditions, and it decreased when the production of the antioxidant α-tocopherol increased. This antioxidant protection resulted in a build-up of phytoplankton biomass, especially at T+. Under the combined effect of both stressors (S-T+), the concentration of ω3 fatty acids increased, potentially leading to higher-quality FA composition. These results, which were related to the dominance of sub-Antarctic species in phytoplankton assemblages, contribute to the understanding of the potential consequences of ocean warming and increase seawater freshening on the trophic webs of the Southern Ocean.
Se presenta un modelo matemático del sistema fitoplancton-zooplancton para una región costera ant... more Se presenta un modelo matemático del sistema fitoplancton-zooplancton para una región costera antártica, considerando la mezcla vertical como factor forzante. Se demuestra que el sistema es estable sólo por el efecto compensatorio de la mezcla vertical que resuspende algas. El principal control físico es la mezcla vertical y el control biológico es de tipo top-down.
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