scholarly journals Phytoplankton blooms on the western shelf of Tasmania: evidence of a highly productive ecosystem

Ocean Science ◽  
2015 ◽  
Vol 11 (1) ◽  
pp. 1-11 ◽  
Author(s):  
J. Kämpf
Keyword(s):  
Satellite Data ◽  
Coastal Upwelling ◽  
Phytoplankton Bloom ◽  
Hot Spot ◽  
Marine Ecosystem ◽  
Austral Summer ◽  
Phytoplankton Blooms ◽  
Study Region ◽  
Upwelling System ◽  
Fluorescence Line

Abstract. Satellite-derived chlorophyll a data using the standard NASA-OC3 (ocean colour) algorithm are strongly biased by coloured dissolved organic matter and suspended sediment of river discharges, which is a particular problem for the western Tasmanian shelf. This work reconstructs phytoplankton blooms in the study region using a quadratic regression between OC3 data and chlorophyll fluorescence based on the fluorescence line height (FLH) data. This regression is derived from satellite data of the nearby Bonney upwelling region, which is devoid of river influences. To this end, analyses of 10 years of MODIS-aqua satellite data reveal the existence of a highly productive ecosystem on the western Tasmanian shelf. The region normally experiences two phytoplankton blooms per annum. The first bloom occurs during late austral summer months as a consequence of upwelling-favourable coastal winds. Hence, the western Tasmanian shelf forms a previously unknown upwelling centre of the regional upwelling system, known as Great South Australian Coastal Upwelling System. The second phytoplankton bloom is a classical spring bloom also developing in the adjacent Tasman Sea. The author postulates that this region forms another important biological hot spot for the regional marine ecosystem.

scholarly journals Phytoplankton blooms on the western shelf of Tasmania: evidence of a highly productive ecosystem

2014 ◽  
Vol 11 (5) ◽  
pp. 2173-2204 ◽  
Author(s):  
J. Kämpf
Keyword(s):  
Coastal Upwelling ◽  
Austral Summer ◽  
Nutrient Supply ◽  
Phytoplankton Blooms ◽  
The West ◽  
River Plumes ◽  
Study Region ◽  
Fur Seals ◽  
Color Data ◽  
Event Based

Abstract. Analyses of >10 years of satellite-derived ocean-color data reveal the existence of a highly productive ecosystem on the west Tasmanian shelf. A closer event-based analysis indicates that the nutrient supply for this system has two different dynamical origins: (a) wind-driven coastal upwelling and (b) river plumes. During austral summer months, the west Tasmanian shelf forms a previously unknown upwelling center of the "Great South Australian Coastal Upwelling System", presumably injecting nutrient-rich water into western Bass Strait. Surprisingly, river discharges render the study region productive during other seasons of the year, except when nutrient-poor water of the South Australian Current reaches the region. Overall, the west Tasmanian shelf is more phytoplankton-productive than the long-known coastal upwelling along the Bonney Coast. The existence of phytoplankton blooms during the off-upwelling-season may explain the wintertime spawing aggregations of the blue grenadier (Macruronus novaezelandiae) and the associated regionally high abundance of Australian fur seals (Arctocephalus pusillus doriferus).

scholarly journals Hydrological differentiation and spatial distribution of high altitude wetlands in a semi-arid Andean region derived from satellite data

2011 ◽  
Vol 8 (1) ◽  
pp. 1287-1327 ◽  
Author(s):  
M. Otto ◽  
D. Scherer ◽  
J. Richters
Keyword(s):  
High Altitude ◽  
Satellite Data ◽  
Regional Scale ◽  
Austral Summer ◽  
Monthly Precipitation ◽  
Austral Winter ◽  
Andean Region ◽  
Study Region ◽  
The Andes ◽  
Semi Arid

Abstract. High Altitude Wetlands of the Andes (HAWA) are unique types of wetlands within the semi-arid high Andean region. Knowledge about HAWA has been derived mainly from studies at single sites within different parts of the Andes at only small time scales. On the one hand HAWA depend on water provided by glacier streams, snow melt or precipitation. On the other hand, they are suspected to influence hydrology through water retention and vegetation growth altering stream flow velocity. We derived HAWA land cover from satellite data at regional scale and analysed changes in connection with precipitation over the last decade. Perennial and temporal HAWA subtypes can be distinguished by seasonal changes of photosynthetically active vegetation (PAV) indicating the perennial or temporal availability of water during the year. HAWA have been delineated within a region of 11 000 km2 situated in the Northwest of Lake Titicaca. The multi temporal classification method used Normalized Differenced Vegetation Index (NDVI) and Normalized Differenced Infrared Index (NDII) data derived from two Landsat ETM+ scenes at the end of austral winter (September 2000) and at the end of austral summer (May 2001). The mapping result indicates an unexpected high abundance of HAWA covering about 800 km2 of the study region (6%). Annual HAWA mapping was computed using NDVI 16-day composites of Moderate Resolution Imaging Spectroradiometer (MODIS). Analyses on the reletation between HAWA and precipitation was based on monthly precipitation data of the Tropical Rain Measurement Mission (TRMM 3B43) and MODIS Eight Day Maximum Snow Extent data (MOD10A2) from 2000 to 2010. We found HAWA subtype specific dependencies to precipitation conditions. Strong relation exists between perennial HAWA and snow fall (r2: 0.82) in dry austral winter months (June to August) and between temporal HAWA and precipitation (r2: 0.75) during austral summer (March to May). Annual spatial patterns of perennial HAWA indicated spatial alteration of water supply for PAV up to several hundred metres at a single HAWA site.

scholarly journals Hydrological differentiation and spatial distribution of high altitude wetlands in a semi-arid Andean region derived from satellite data

2011 ◽  
Vol 15 (5) ◽  
pp. 1713-1727 ◽  
Author(s):  
M. Otto ◽  
D. Scherer ◽  
J. Richters
Keyword(s):  
High Altitude ◽  
Satellite Data ◽  
Austral Summer ◽  
Snow Melt ◽  
Austral Winter ◽  
Andean Region ◽  
Unique Type ◽  
Study Region ◽  
The Andes ◽  
Semi Arid

Abstract. High Altitude Wetlands of the Andes (HAWA) belong to a unique type of wetland within the semi-arid high Andean region. Knowledge about HAWA has been derived mainly from studies at single sites within different parts of the Andes at only small time scales. On the one hand, HAWA depend on water provided by glacier streams, snow melt or precipitation. On the other hand, they are suspected to influence hydrology through water retention and vegetation growth altering stream flow velocity. We derived HAWA land cover from satellite data at regional scale and analysed changes in connection with precipitation over the last decade. Perennial and temporal HAWA subtypes can be distinguished by seasonal changes of photosynthetically active vegetation (PAV) indicating the perennial or temporal availability of water during the year. HAWA have been delineated within a region of 12 800 km2 situated in the Northwest of Lake Titicaca. The multi-temporal classification method used Normalized Differenced Vegetation Index (NDVI) and Normalized Differenced Infrared Index (NDII) data derived from two Landsat ETM+ scenes at the end of austral winter (September 2000) and at the end of austral summer (May 2001). The mapping result indicates an unexpected high abundance of HAWA covering about 800 km2 of the study region (6 %). Annual HAWA mapping was computed using NDVI 16-day composites of Moderate Resolution Imaging Spectroradiometer (MODIS). Analyses on the relation between HAWA and precipitation was based on monthly precipitation data of the Tropical Rain Measurement Mission (TRMM 3B43) and MODIS Eight Day Maximum Snow Extent data (MOD10A2) from 2000 to 2010. We found HAWA subtype specific dependencies on precipitation conditions. A strong relation exists between perennial HAWA and snow fall (r2: 0.82) in dry austral winter months (June to August) and between temporal HAWA and precipitation (r2: 0.75) during austral summer (March to May). Annual changes in spatial extend of perennial HAWA indicate alterations in annual water supply generated from snow melt.

scholarly journals The relation of wind-driven coastal and offshore upwelling in the Benguela Upwelling System

2021 ◽  
Author(s):  
Mohammad Hadi Bordbar ◽  
Volker Mohrholz ◽  
Martin Schmidt
Keyword(s):  
Chlorophyll A ◽  
Wind Stress ◽  
Coastal Upwelling ◽  
Marine Ecosystem ◽  
Surface Wind ◽  
Phase Relationship ◽  
Wind Stress Curl ◽  
Upwelling System ◽  
Benguela Upwelling ◽  
Ekman Theory

AbstractSpatial and temporal variations of nutrient-rich upwelled water across the major eastern boundary upwelling systems are primarily controlled by the surface wind with different, and sometimes contrasting, impacts on coastal upwelling systems driven by alongshore wind and offshore upwelling systems driven by the local wind-stress-curl. Here, concurrently measured wind-fields, satellite-derived Chlorophyll-a concentration along with a state-of-the-art ocean model simulation spanning 2008-2018 are used to investigate the connection between coastal and offshore physical drivers of the Benguela Upwelling System (BUS). Our results indicate that the spatial structure of long-term mean upwelling derived from Ekman theory and the numerical model are fairly consistent across the entire BUS and closely followed by the Chlorophyll-a pattern. The variability of the upwelling from the Ekman theory is proportionally diminished with offshore distance, whereas different and sometimes opposite structures are revealed in the model-derived upwelling. Our result suggests the presence of sub-mesoscale activity (i.e., filaments and eddies) across the entire BUS with a large modulating effect on the wind-stress-curl-driven upwelling off Lüderitz and Walvis Bay. In Kunene and Cape Frio upwelling cells, located in the northern sector of the BUS, the coastal upwelling and open-ocean upwelling frequently alternate each other, whereas they are modulated by the annual cycle and mostly in phase off Walvis Bay. Such a phase relationship appears to be strongly seasonally dependent off Lüderitz and across the southern BUS. Thus, our findings suggest this relationship is far more complex than currently thought and seems to be sensitive to climate changes with short- and far-reaching consequences for this vulnerable marine ecosystem.

scholarly journals Phenology and Environmental Control of Phytoplankton Blooms in the Kong Håkon VII Hav in the Southern Ocean

2021 ◽  
Vol 8 ◽  
Author(s):  
Hanna M. Kauko ◽  
Tore Hattermann ◽  
Thomas Ryan-Keogh ◽  
Asmita Singh ◽  
Laura de Steur ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Environmental Changes ◽  
Environmental Control ◽  
Phytoplankton Bloom ◽  
Mixed Layer Depth ◽  
Marine Ecosystem ◽  
Light Availability ◽  
Phytoplankton Blooms ◽  
Atlantic Sector

Knowing the magnitude and timing of pelagic primary production is important for ecosystem and carbon sequestration studies, in addition to providing basic understanding of phytoplankton functioning. In this study we use data from an ecosystem cruise to Kong Håkon VII Hav, in the Atlantic sector of the Southern Ocean, in March 2019 and more than two decades of satellite-derived ocean color to study phytoplankton bloom phenology. During the cruise we observed phytoplankton blooms in different bloom phases. By correlating bloom phenology indices (i.e., bloom initiation and end) based on satellite remote sensing to the timing of changes in environmental conditions (i.e., sea ice, light, and mixed layer depth) we studied the environmental factors that seemingly drive phytoplankton blooms in the area. Our results show that blooms mainly take place in January and February, consistent with previous studies that include the area. Sea ice retreat controls the bloom initiation in particular along the coast and the western part of the study area, whereas bloom end is not primarily connected to sea ice advance. Light availability in general is not appearing to control the bloom termination, neither is nutrient availability based on the autumn cruise where we observed non-depleted macronutrient reservoirs in the surface. Instead, we surmise that zooplankton grazing plays a potentially large role to end the bloom, and thus controls its duration. The spatial correlation of the highest bloom magnitude with marked topographic features indicate that the interaction of ocean currents with sea floor topography enhances primary productivity in this area, probably by natural fertilization. Based on the bloom timing and magnitude patterns, we identified five different bloom regimes in the area. A more detailed understanding of the region will help to highlight areas with the highest relevance for the carbon cycle, the marine ecosystem and spatial management. With this gained understanding of bloom phenology, it will also be possible to study potential shifts in bloom timing and associated trophic mismatch caused by environmental changes.

scholarly journals Movements and behaviour of blue whales satellite tagged in an Australian upwelling system

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Luciana M. Mӧller ◽  
Catherine R. M. Attard ◽  
Kerstin Bilgmann ◽  
Virginia Andrews-Goff ◽  
Ian Jonsen ◽  
...  
Keyword(s):  
Coastal Upwelling ◽  
Human Impacts ◽  
Austral Summer ◽  
Temporal Scale ◽  
Sea Surface ◽  
Height Anomaly ◽  
Environmental Drivers ◽  
Upwelling System ◽  
Spatio Temporal ◽  
Blue Whales

AbstractKnowledge about the movement ecology of endangered species is needed to identify biologically important areas and the spatio-temporal scale of potential human impacts on species. Blue whales (Balaenoptera musculus) are endangered due to twentieth century whaling and currently threatened by human activities. In Australia, they feed in the Great Southern Australian Coastal Upwelling System (GSACUS) during the austral summer. We investigate their movements, occupancy, behaviour, and environmental drivers to inform conservation management. Thirteen whales were satellite tagged, biopsy sampled and photo-identified in 2015. All were genetically confirmed to be of the pygmy subspecies (B. m. brevicauda). In the GSACUS, whales spent most of their time over the continental shelf and likely foraging in association with several seascape variables (sea surface temperature variability, depth, wind speed, sea surface height anomaly, and chlorophyll a). When whales left the region, they migrated west and then north along the Australian coast until they reached West Timor and Indonesia, where their movements indicated breeding or foraging behaviour. These results highlight the importance of the GSACUS as a foraging ground for pygmy blue whales inhabiting the eastern Indian Ocean and indicate the whales’ migratory route to proposed breeding grounds off Indonesia. Information about the spatio-temporal scale of potential human impacts can now be used to protect this little-known subspecies of blue whale.

scholarly journals Monthly measured primary and new productivities in the Ulleung Basin as a biological "hot spot" in the East/Japan Sea

2013 ◽  
Vol 10 (2) ◽  
pp. 2127-2158 ◽  
Author(s):  
J. H. Kwak ◽  
S. H. Lee ◽  
H. J. Park ◽  
E. J. Choy ◽  
H. D. Jeong ◽  
...  
Keyword(s):  
Primary Production ◽  
Nitrogen Source ◽  
Coastal Upwelling ◽  
Hot Spot ◽  
Marine Ecosystem ◽  
Japan Sea ◽  
Temporal Variations ◽  
Ulleung Basin ◽  
Deep Basin ◽  
Annual Primary Production

Abstract. The Ulleung Basin (UB), located in the southwestern part of the East/Japan Sea (EJS), is considered having an unusually high productivity for a~deep basin. Recently changes have been reported in physical, chemical, and in biological properties. Here we measured the primary and new productivities in the UB using a 13C-15N dual isotope tracer technique. Measurements took place every month for the first time throughout a year for a~better estimate of the annual primary production in the EJS. Temporal variations of temperature, salinity and density (σt) in the study area were highly seasonal as expected for an ocean in the temperate zone. Nutrient distributions reflected these seasonal fluctuations in the vertical structure of the water column. Diatoms were in general the most dominant phytoplankton ranging from 15.5 to 82.2% with an average of 42.0% (S.D. = ± 9.9%). Based on those average daily productivities from our monthly measurements, the annual primary, new, and regenerated production in the UB were 273.0 g C m−2 yr−1, 62.6 g N m−2 yr−1, and 48.7 g N m−2 yr−1, respectively. Our estimated high f-ratio (0.59) in the UB, indicated that the predominant nitrogen source for primary production was nitrate. This is comparable with the nitrogen source in a productive coastal-upwelling region. New carbon production by phytoplankton is estimated as 212.8 g C m−2 yr−1 (S.D. = ± 9.7 g C m−2 yr−1) which indicates that a large portion (78%) of total annual primary production might potentially be exported from the diatom-dominated euphotic zone to a deeper zone in the UB. Further intense integrated field observations will be necessary to improve our understanding of the current marine ecosystem in the UB as an important biological production area in the EJS.

scholarly journals Monthly measured primary and new productivities in the Ulleung Basin as a biological "hot spot" in the East/Japan Sea

2013 ◽  
Vol 10 (7) ◽  
pp. 4405-4417 ◽  
Author(s):  
J. H. Kwak ◽  
S. H. Lee ◽  
H. J. Park ◽  
E. J. Choy ◽  
H. D. Jeong ◽  
...  
Keyword(s):  
Primary Production ◽  
Nitrogen Source ◽  
Coastal Upwelling ◽  
Hot Spot ◽  
Marine Ecosystem ◽  
Japan Sea ◽  
Temporal Variations ◽  
Ulleung Basin ◽  
Deep Basin ◽  
Annual Primary Production

Abstract. The Ulleung Basin (UB), located in the southwestern part of the East/Japan Sea (EJS), is considered having an unusually high productivity for a deep basin. Recently changes have been reported in physical, chemical, and biological properties. Here we measured the primary and new productivities in the UB using a 13C-15N dual isotope tracer technique. Measurements took place every month for the first time throughout a year for a better estimate of the annual primary production in the EJS. Temporal variations of temperature, salinity, and density (σt) in the study area were highly seasonal as expected for an ocean in the temperate zone. Nutrient distributions reflected these seasonal fluctuations in the vertical structure of the water column. Diatoms were in general the most dominant phytoplankton ranging from 15.5 to 82.2% with an average of 42.0% (S.D. = ±9.9%). Based on those average daily productivities from our monthly measurements, the annual primary, new, and regenerated production in the UB were 273.0 g C m−2 yr−1, 62.6 g N m−2 yr−1, and 48.7 g N m−2 yr−1, respectively. Our estimated high f ratio (0.59) in the UB, indicated that the predominant nitrogen source for primary production was nitrate. This is comparable with the nitrogen source in a productive coastal-upwelling region. New carbon production by phytoplankton is estimated as 145.6 g C m−2 yr−1 (S.D. = ±40.8 g C m−2 yr−1) which indicates that a large portion (53.9%) of the total annual primary production might potentially be exported from the diatom-dominated euphotic zone to a deeper zone in the UB. Further intense integrated field observations will be necessary to improve our understanding of the current marine ecosystem in the UB as an important biological production area in the EJS.

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