Flujo de partículas en un ambiente costero Antártico de aguas someras: un estudio con trampas de sedimento

Sediment trap arrays were deployed at Potter Cove, King George Island, Antarctica, between December 1991 and August 1992 and in the summer seasons of 1993-1994, and 1995. The sampling sites reached 30 m depth, and traps were placed during the different seasons at various distances from the sea bottom (0.1 to 25 m), some being buried in the sediments. Daily sedimentation rates of total particulate matter (TPM) and chlorophyll-a were estimated. Water column temperature and salinity as well as pigment and TPM concentration were also measured and related to traps´ results. Water column data evidenced processes in relation with phytoplankton dynamics, stormy events and particles containing fresh water runoff. Similar trends were observed in the traps located at 25 m, 1 m and sometimes even in those located to around 0.1 m from sea bottom, although traps buried in the sediments mainly reflected resuspension events. Chlorophyll a fluxes were higher in the bottom traps, but the sedimented organic fraction of the TPM (particulate organic matter, POM) was higher in the traps located remotely from the bottom, being significantly lower in the buried traps (i.e. POM represented 50% of TPM at 1 m and 9% POM in the buried trap on November 23 in 1993, although a great variability among sampling dates was also observed). The significance of these dynamics for the food availability for the macrozoobenthic organisms present in the area is discussed.Entre diciembre de 1991 y agosto de 1992 y durante las campañas de verano de 1993-1994 y 1995 se estudió la tasa de sedimentación de partículas en Caleta Potter, Isla King George - 25 de Mayo, Antártida, mediante el empleo de trampas de sedimento. La profundidad en los sitios de muestreo fue de 30 m. Las trampas fueron colocadas a distintas distancias del fondo (0,1 a 25 m), habiéndose enterrado algunas en los sedimentos. Se estimaron las tasas diarias de sedimentación para el total de material particulado y los pigmentos. Se midieron además la temperatura y la salinidad, así como la concentración de material particulado total y pigmentos en la columna de agua. Estos parámetros fueron relacionados con aquellos de las trampas de sedimento. Los resultados de la columna de agua reflejaron procesos relacionados con la dinámica del fitoplancton, eventos de tormentas y aportes terrígenos de agua dulce. Esto fue válido para las trampas colocadas a 25 m, 1 m y en ocasiones aún para aquellas colocadas a 0,1 m, si bien los datos obtenidos de las trampas enterradas en el sedimento se relacionan con episodios de resuspensión. Los flujos de clorofila a fueron mayores en las trampas más cercanas al fondo, pero la fracción orgánica del material particulado sedimentada fue significativamente menor en las trampas enterradas. Por ejemplo, el porcentaje de materia orgánica en las trampas del 23 de noviembre de 1993 fue de 50% a 1 m y del 9% en la trampa enterrada en los sedimentos, si bien pudo observarse una gran variabilidad entre fechas de muestreo. Se discute la importancia de esta dinámica para la nutrición de los organismos del macrozoobentos presentes en el área

Variability and change in the west Antarctic Peninsula marine system: Research priorities and opportunities

The west Antarctic Peninsula (WAP) region has undergone significant changes in temperature and seasonal ice dynamics since the mid-twentieth century, with strong impacts on the regional ecosystem, ocean chemistry and hydrographic properties. Changes to these long-term trends of warming and sea ice decline have been observed in the 21st century, but their consequences for ocean physics, chemistry and the ecology of the high-productivity shelf ecosystem are yet to be fully established. The WAP shelf is important for regional krill stocks and higher trophic levels, whilst the degree of variability and change in the physical environment and documented biological and biogeochemical responses make this a model system for how climate and sea ice changes might restructure high-latitude ecosystems. Although this region is arguably the best-measured and best-understood shelf region around Antarctica, significant gaps remain in spatial and temporal data capable of resolving the atmosphere-ice-ocean-ecosystem feedbacks that control the dynamics and evolution of this complex polar system. Here we summarise the current state of knowledge regarding the key mechanisms and interactions regulating the physical, biogeochemical and biological processes at work, the ways in which the shelf environment is changing, and the ecosystem response to the changes underway. We outline the overarching cross-disciplinary priorities for future research, as well as the most important discipline-specific objectives. Underpinning these priorities and objectives is the need to better define the causes, magnitude and timescales of variability and change at all levels of the system. A combination of traditional and innovative approaches will be critical to addressing these priorities and developing a co-ordinated observing system for the WAP shelf, which is required to detect and elucidate change into the future

Distribución de nutrientes inorgánicos y clorofila-a a través de los frentes de la Plataforma Continental Patagónica Argentina durante verano y otoño

Oceanographic data collected during 2001-2003 on the Patagonian Continental Shelf of Argentina were analyzed in order to study the main chemical features of this large shelf. The variation of inorganic nutrients and chlorophyll-a during summer and fall in an area within 40 to 60 km from the coast are presented. Nitrate is the limiting nutrient in the region and is negatively correlated to chlorophyll-a. All variables show localized variations in summer, which can be related to tidal fronts through the comparison of our data with the critical Simpson parameter of stability (50 J m-3). In fall, nutrient concentrations on the continental shelf were more uniform and generally higher than in summer due to the disruption of these fronts.Datos oceanógraficos recolectados durante 2001-2003 en la Plataforma Continental Patagónica Argentina fueron analizados para estudiar las principales características químicas en esta gran plataforma. Se presenta la variación de los nutrientes inorgánicos y de la clorofila-a a una distancia de 40 a 60 km de la costa. El nitrato es el nutriente limitante en la región y está negativamente correlacionado con la clorofila-a. Todas las variables presentan variaciones localizadas en verano, las cuales pueden ser relacionadas con los frentes de marea a través de la comparación de nuestros datos con el parámetro crítico de estabilidad de Simpson (50 J m-3). En otoño, la concentración de nutrientes en la plataforma continental fue más uniforme y generalmente mayor que en verano debido a la disrupción de dichos frentes.Facultad de Ciencias Naturales y Muse

Influence of microbial community composition and metabolism on air.sea ΔpCO 2 variation off the western Antarctic Peninsula

We studied CO 2 and O 2 dynamics in the western Antarctic Peninsula (WAP) waters in relation to (1) phytoplankton biomass, (2) microbial community primary production and respiration, and (3), for the first time, phytoplankton composition, during summer and fall in 3 consecutive years (2002, 2003 and 2004). The areal average of ΔpCO 2 (the difference between surface seawater and atmospheric partial pressure of CO 2) for the 3 yr was significantly negative (.20.04 ± 44.3 μatm, p < 0.01) during the summer to fall period in the region, possibly indicating a CO 2 sink. In the southern WAP (i.e. south of Anvers Island), ΔpCO 2 was significantly negative (.43.60 ± 39.06 μatm) during fall. In the northern WAP (north of Anvers Island), ΔpCO 2 values showed a more complex distribution during summer and fall (.4.96 ± 37.6 and 21.71 ± 22.39 μatm, respectively). Chlorophyll a (chl a) concentration averaged 1.03 ± 0.25 μg l.1 and was higher in the south of the peninsula. Phytoplankton composition influenced chl a concentration with higher and lower values for diatom-and phytoflagellate-dominated communities, respectively. A significant negative correlation existed between chl a and ΔpCO 2. From incubation experiments performed in the northern WAP, respiration was low (averaging 5.1 mmol O 2 m.3 d.1), and the net community production (NCP) correlated negatively with ΔpCO 2 and positively with %O 2 saturation. However, despite the high NCP values measured, ΔpCO 2 was significantly positive in the northern WAP during the summer to fall period. Strong mixing and lower chl a concentration may explain this result. In contrast, ΔpCO 2 was significantly negative in the southern WAP, possibly because of high surface water chl a concentration.Facultad de Ciencias Naturales y Muse

Correction to: Detection of the phycotoxin pectenotoxin-2 in waters around King George Island, Antarctica

A correction to this paper has been published: https://doi.org/10.1007/s00300-021-02834-3</jats:p

Anatomy of a glacial meltwater discharge event in an Antarctic Cove

Glacial meltwater discharge from Antarctica is a key influence on the marine environment, impacting ocean circulation, sea level and productivity of the pelagic and benthic ecosystems. The responses elicited depend strongly on the characteristics of the meltwater releases, including timing, spatial structure and geochemical composition. Here we use isotopic tracers to reveal the time-varying pattern of meltwater during a discharge event from the Fourcade Glacier into Potter Cove, northern Antarctic Peninsula. The discharge is strongly dependent on local air temperature, and accumulates into an extremely thin, buoyant layer at the surface. This layer showed evidence of elevated turbidity, and responded rapidly to changes in atmospherically driven circulation to generate a strongly pulsed outflow from the cove to the broader ocean. These characteristics contrast with those further south along the Peninsula, where strong glacial frontal ablation is driven oceanographically by intrusions of warm deep waters from offshore. The Fourcade Glacier switched very recently to being land-terminating; if retreat rates elsewhere along the Peninsula remain high and glacier termini progress strongly landward, the structure and impact of the freshwater discharges are likely to increasingly resemble the patterns elucidated here

Response of a natural Antarctic phytoplankton assemblage to changes in temperature and salinity

The climate around the Western Antarctic Peninsula (WAP) is rapidly changing and dramatically affecting marine coastal waters. Increases in air and seawater temperatures, not matter how small, can alter coastal biological communities due to both temperature increases as well as salinity reduction from glacier melting. The aim of this study was to evaluate the individual and combined effects of elevated sea surface temperature (+4 °C) and decreased salinity (−4) on growth and assemblage composition of natural summer phytoplankton from Potter Cove (King George Island, South Shetlands, northern WAP), using an outdoor microcosm experiment. Pigment composition was analyzed by high performance liquid chromatography (HPLC/Chemtax) and species composition by light and electron microscopy. Increases in phytoplankton biomass during the first 3 days at elevated-temperatures coincided with an increase in the abundance and the specific growth rate of small centric diatoms (Chaetoceros socialis and Shionodiscus gaarderae, mostly observed in temperate waters) and unidentified small phytoflagellates &lt;5 μm. In contrast, pennate diatoms significantly decreased. At the end of the experiment on day 7, under nitrate and phosphate limitation, chlorophytes abundances increased under low salinity whereas prasinophytes decreased in all treatments. This study suggests that climate change could notably affect Antarctic phytoplankton composition by favouring temperate-water species previously undetected in Antarctic waters, such us S. gaarderae. Moreover, the observed changes in phytoplankton structure, associated with an increase of nano- over micro-size taxa, could have important implications for future Antarctic food webs

Distribución de nutrientes inorgánicos y clorofila-a a través de los frentes de la Plataforma Continental Patagónica Argentina durante verano y otoño

Oceanographic data collected during 2001-2003 on the Patagonian Continental Shelf of Argentina were analyzed in order to study the main chemical features of this large shelf. The variation of inorganic nutrients and chlorophyll-a during summer and fall in an area within 40 to 60 km from the coast are presented. Nitrate is the limiting nutrient in the region and is negatively correlated to chlorophyll-a. All variables show localized variations in summer, which can be related to tidal fronts through the comparison of our data with the critical Simpson parameter of stability (50 J m-3). In fall, nutrient concentrations on the continental shelf were more uniform and generally higher than in summer due to the disruption of these fronts.Datos oceanógraficos recolectados durante 2001-2003 en la Plataforma Continental Patagónica Argentina fueron analizados para estudiar las principales características químicas en esta gran plataforma. Se presenta la variación de los nutrientes inorgánicos y de la clorofila-a a una distancia de 40 a 60 km de la costa. El nitrato es el nutriente limitante en la región y está negativamente correlacionado con la clorofila-a. Todas las variables presentan variaciones localizadas en verano, las cuales pueden ser relacionadas con los frentes de marea a través de la comparación de nuestros datos con el parámetro crítico de estabilidad de Simpson (50 J m-3). En otoño, la concentración de nutrientes en la plataforma continental fue más uniforme y generalmente mayor que en verano debido a la disrupción de dichos frentes.Facultad de Ciencias Naturales y Muse

Role of plankton communities in sea-air variations in pCO2 in the SW Atlantic Ocean

The influence of the plankton community structure on carbon dynamics was studied in the surface waters of the Argentinean continental shelf (SW Atlantic Ocean) in summer and fall 2002, 2003 and 2004, The horizontal changes in plankton community respiration (R), net community production (NCP) and gross primary production (GPP) were (1) compared with the difference in the partial pressure of CO2 (pCO2) between the sea surface and the atmosphere (ΔpCO2), (2) compared with oxygen saturation and (3) related to the microscopic phytoplankton assemblages, This area, which has recently been shown to be a CO2 sink, had an average surface oxygen saturation of 108.1%, indicating that net photosynthesis could have played a dominant role in the CO2 dynamics. At most stations, the production:respiration (GPP:R) ratio was greater than 1, indicating that planktonic communities were autotrophic; the average GPP:R ratio for the whole study was 2.99, Phytoplankton biomass (chlorophyll a) and NCP showed an inverse relationship with ΔpCO2 and a direct relationship with %O 2 saturation when phytoplankton assemblages were dominated by diatoms (30% of the stations), This was not the case when small (≤5 μm) flagellates were the most abundant organisms, Although NCP was mostly positive for both groups of stations (i.e. diatom-dominated or small flagellate- dominated), other physical and biological processes are thought to modify the CO2 dynamics when small flagellates are the prevailing phytoplankton group.Facultad de Ciencias Naturales y Muse

Inter-decadal variability of phytoplankton biomass along the coastal West Antarctic Peninsula

The West Antarctic Peninsula (WAP) is a climatically sensitive region where periods of strong warming have caused significant changes in the marine ecosystem and food-web processes. Tight coupling between phytoplankton and higher trophic levels implies that the coastal WAP is a bottom-up controlled system, where changes in phytoplankton dynamics may largely impact other food-web components. Here, we analysed the inter-decadal time series of year-round chlorophyll-a (Chl) collected from three stations along the coastal WAP: Carlini Station at Potter Cove (PC) on King George Island, Palmer Station on Anvers Island and Rothera Station on Adelaide Island. There were trends towards increased phytoplankton biomass at Carlini Station (PC) and Palmer Station, while phytoplankton biomass declined significantly at Rothera Station over the studied period. The impacts of two relevant climate modes to the WAP, the El Niño-Southern Oscillation and the Southern Annular Mode, on winter and spring phytoplankton biomass appear to be different among the three sampling stations, suggesting an important role of local-scale forcing than large-scale forcing on phytoplankton dynamics at each station. The inter-annual variability of seasonal bloom progression derived from considering all three stations together captured ecologically meaningful, seasonally co-occurring bloom patterns which were primarily constrained by water-column stability strength. Our findings highlight a coupled link between phytoplankton and physical and climate dynamics along the coastal WAP, which may improve our understanding of overall WAP food-web responses to climate change and variability