Temporal controls on silicic acid utilisation along the West Antarctic Peninsula

The impact of climatic change along the Antarctica Peninsula has been widely debated in light of atmospheric/oceanic warming and increases in glacial melt over the past half century. Particular concern exists over the impact of these changes on marine ecosystems, not only on primary producers but also on higher trophic levels. Here we present a record detailing the historical controls on the biogeochemical cycling of silicic acid [Si(OH)4] on the west Antarctica Peninsula margin, a region in which the modern phytoplankton environment is constrained by seasonal sea-ice. We demonstrate that Si(OH)4 cycling through the Holocene alternates between being primarily regulated by sea-ice or glacial discharge from the surrounding grounded ice-sheet. With further climate-driven change and melting forecast for the 21st Century, our findings document the potential for biogeochemical cycling and multi-trophic interactions along the peninsula to be increasingly regulated by glacial discharge, altering food-web interactions

Physical control of spring summer phytoplankton dynamics in the North Water, April July 1998

International audienceA 4-month multidisciplinary expedition, beginning at the end of winter to track the spring phytoplankton bloom to its termination in summer, was conducted from April to July 1998. The aim of the expedition was to investigate possible mechanisms responsible for the high biological productivity of the North Water, the most productive and largest polynya in the Northern Hemisphere. The aims of the present study were to investigate: (1) the effects of the physical forces, driving the formation of the polynya, on the dynamics of the phytoplankton stock in the polynya over the spring-summer period; and (2) the factors that limit the maximum biomass of phytoplankton. Contrasting physical characteristics, including ice concentration, surface mixed-layer depth (MLD), salinity and temperature in the surface mixed layer (SML), were observed between the east and west sides of the polynya. The Greenland (eastern) side of the polynya was characterized by a shallow SML, warm temperature, and high salinity relative to the Ellesmere Island, Canada (western) side. Chlorophyll a (Chl)>1 mg m -3 was observed in late April on the eastern side, and in late May on the western side. The peak phytoplankton bloom occurred in the southeastern part of the polynya, with average Chl of 15 mg m -3 (240-300 mg m -2) in the euphotic zone during the end of May and beginning of June. The increased phytoplankton biomass was associated with higher salinity and warmer temperature on the eastern side of the polynya. Low temperature in April and May decoupled the increase of Chl biomass from the shallowed SML, as predicted by Sverdrup's model. As Chl in the euphotic zone increased to 5 mg m -3, the proportion of light absorption by phytoplankton could not increase further with Chl biomass, which might have limited the increase of primary production in the water column. Although the initial nutrient inventories largely determined the maximum biomass of phytoplankton, self-shading occurred in the build-up phytoplankton biomass to ∼5 mg m -3, which retarded the timing of the peak bloom. Both sensible heat due to deep warm water entrainment into the SML and the biological heating effect via phytoplankton light absorption appear to contribute to the pattern of phytoplankton distribution in the North Water

Phytoplankton biomass, production and potential export in the North Water

International audienceThe seasonal patterns of phytoplankton biomass and production were determined in the North Water, located between Greenland and Ellesmere Island (Canadian Arctic), in August 1997, April-July 1998, and August-September 1999. The patterns differed among the four defined regions of this large polynya, i.e. North (>77.5°N), East (>75°W), West (-3). The large-sized (>5 μm) fraction dominated the biomass and production during the bloom. During July, August, and September, biomass and production decreased over the whole region, with the highest biomass, dominated by large cells, occurring in the North. The annual particulate and dissolved phytoplankton production were the highest ever reported for the high Arctic, reaching maximum values of 254 and 123 g C m -2 yr -1, respectively, in the East. Rates in the North and West were considerably lower than in the East (ca. two- and three-fold, respectively). The f-ratios (i.e. ratio of new to total production), derived from the size structure of phytoplankton, were high north of 76°N (0.4-0.7). Regionally, this indicated a high potential export of particulate organic carbon ( EPOC) from the phytoplankton community to other trophic compartments and/or downwards in the East (155 g C m -2 yr -1), with lower values in the North and West (i.e. 77 and 42 g C m -2 yr -1, respectively). The seasonal and spatial patterns of EPOC were consistent with independent estimates of potential carbon export. Phytoplankton biomass and production were generally dominated by the large size fraction, whereas EPOC seemed to be dominated by the large size fraction early in the season and by the small size fraction (<5 μm) from June until the end of the growing season

Estimating the biodiversity of Planning Domain 5 (Marion and Prince Edward Islands – Del Cano – Crozet) for ecoregionalisation

The CCAMLR MPA Workshop on Marine Protected Areas, held in Brest (France) in August 2011, recommended that the Scientific Committee considers supporting three technical workshops including one specific to Planning Domain 5. Planning Domain 5 includes Marion and Prince Edward Islands, the Del Cano Rise and the Crozet Archipelago in the north. It also includes the Ob and Lena seamounts. The workshop focusing on Planning Domain 5 was held in St Pierre, La Réunion, France from 15th May to 18th May, 2012 at the headquarters of TAAF (French Southern and Antarctic Territories). It followed a meeting on the northern part of Planning Domain 5, which was held in South Africa in 2008, organized and funded by WWF South Africa and known as Del Cano 1. The intention of the CCAMLR workshop was to study the ecological values and the use of the marine environment and to identify possible threats that might occur in this area. It extended the Del Cano 1 study spatially and also ecologically to include the benthic and pelagic realms. Identification of objectives for Conservation Planning and future research were discussed in relation to national and international projects. Depending on the availability of data, the approach was based on mapping species distributions (either observed data or predictions for species or community presence/abundance based on environmental factors). Various national and international datasets were used including data from CCAMLR. However, South African and French data relevant to the Planning Domain 5 and surrounding domains were a major focus in the workshop because these CCAMLR member nations are the major scientific actors in this region. Species distributions were visualized by the mean of a Geographic Information System. Available Norwegian data from the Bouvetøya region were also discussed, but this region is less studied compared to the Planning Domain 5. The workshop provided benthic and pelagic abiotic classifications of the Planning Domain using geographic and oceanographic features. Distributions of plankton, mesopelagic fish and top predators were consistent with the abiotic regionalization showing latitudinal patterns of communities for the pelagic species. The importance of frontal zones such as the Antarctic Polar Front and especially the Subantarctic Front were highlighted. North of the CCAMLR area, the Agulhas Return Current has a strong influence on this region. The latitudinal zonation of bioregions according to frontal zones may be influenced by climate change. This will have consequences for marine bird and mammal populations as it will change the habitat of their main pelagic prey species (e.g. euphausiids, squids, mesopelagic fish, etc.). The working group concluded that ecoregionalisation has to be conducted at the scale of plateaus which includes Prince Edward Islands, Del Cano Rise and Crozet Islands i.e. a more detailed level than what has been done to date. High productive pelagic areas must be considered in relation to the bathymetry, iron enrichment, fronts and island mass effects, which contrast with high nutrient low chlorophyll areas farther south. Ichtyofauna and benthos were described as being characteristic of the subantarctic zone with some species being endemic. However, cryptic benthic species have not yet been studied. The French and South African islands support substantial colonies of seabirds and seals, which for several species have global importance. For example, the Crozet and Prince Edward Islands together host the entire population of Crozet shag, about 70% of the world population of wandering albatross, 54% of king penguin, 33% of Indian yellow-nosed albatross, 33% of subantarctic fur seal, 27% of sooty albatross and 21% of the world’s southern rockhopper penguin. The high productivity in the vicinity of the islands, together with the large aggregations of seabirds and seals found at the islands, attract various other animals, e.g. several cetaceans, to their vicinity. The populations of several seabirds that breed at the islands have decreased. There is accumulating evidence that decreases of albatrosses and petrels have been substantially influenced by by-catch mortality in fisheries, whereas decreases in some penguins are probably attributable to decreased availability of prey that may have been caused by environmental change. Although the islands themselves enjoy a protected status and fishing is at present excluded within 12 nautical miles of the islands, providing some protection to inshore-foraging species, many of the seabirds and seals range well beyond the immediate precincts of the islands. Some circumnavigate Antarctica and others move to the north well beyond the CCAMLR convention area. Hence, many seabirds and seals are affected by human activities, and almost certainly environmental change, in other CCAMLR domains as well as in regions of the high seas that are administered by other Regional Fisheries Management Organisations. In particular the CCAMLR Planning domains that neighbour Domain 5 are of importance, as is the southern region of the Indian Ocean Tuna Commission (IOTC, FAO Area 51). Human activities in these other areas adversely influence the conservation status of animals from Planning Domain 5, as is the case with by-catch mortality, it will be necessary for CCAMLR to work in close association with other Regional Fisheries Management Organisations (e.g. IOTC), treaties (e.g. Agreement on the Conservation of Albatrosses and Petrels, ACAP) and conservation organisations (e.g. BirdLife International) to achieve a favourable conservation status for species that are at present Threatened or Near Threatened. The problem is sometimes compounded by albatrosses and petrels segregating their at-sea distributions by sex or age or both, so that components of populations may suffer particularly high mortality leading, e.g., to sex imbalances or inadequate recruitment into breeding populations. Preliminary models suggest that both topographical (e.g. plateau and rises) and oceanographic (e.g. locations of fronts) features play important roles in defining good foraging grounds for some wide-ranging predators. Whereas topographical features are permanent, the locations of oceanographic features may be changing, thereby presenting a greater challenge for spatial conservation planning. For some albatrosses (notably Thalassarche spp.) and penguins (notably Eudyptes spp.) there is accumulating evidence that populations and species may segregate their feeding grounds, which also will need to be accounted for in any form of spatial conservation planning. The Working group noted set of preliminary strategic points essential to Systematic Conservation Planning, which include accounting for ecological relationships with surrounding areas (Bouvet to the West, Kerguelen to the East and East Antarctica to the South). The working group concluded that subtropical areas north of the Planning Domain 5 should be included in the planning, because of the spatial range covered by top predators, and also because the limit of the CCAMLR area cuts across the EEZs of both the Prince Edward and the Crozet Islands, as well as the Del Cano Rise. Strategic points include: First of all, biodiversity features needed to be mapped. The workshop concentrated on this objective most of the time. Second, biodiversity targets need to be determined. France will see how to adapt the ones that were used by Lombard et al. (2007) for the EEZ of the Prince Edward Islands, to the Crozet Islands. For the high seas, the working group recommended that the definition of targets should be discussed by EMM and the MPA circumpolar workshop. Third, the Working Group started to evaluate pressures and areas of research that need to be defined (spawning and nursery areas, bycatch, interactions with killer whales, etc.). The involvement of stakeholders was discussed, including fishing industries, NGOs, other relevant treaties and CCAMLR members for the high sea areas. This general theme has to be more specifically discussed during the circumpolar workshop and at the SC. The workshop also considered MPAs existing under national jurisdiction in the Planning Domain, procedures to extend them, and the need for strengthened cooperation between CCAMLR and other relevant legal instruments, organizations and initiatives. To achieve these goals, research and monitoring were discussed under three headings: (1) census of biodiversity, (2) ecoregionalisation classification and (3) monitoring. Such research would make up for a current lack of data, e.g. with regard to the benthos (deep and shallow), the mesopelagic zone and plankton. With regard to monitoring ecological processes, especially at the northern limits of the CCAMLR area, CCAMLR may wish to broaden the lists of species and environmental parameters that are monitored, to consider parameters of species that may best reflect change associated with global warming and, if necessary, develop protocols for any new parameters to be monitored. This would naturally include the use of the Continuous Plankton Recorder and tracking for birds, seals and mammals

Estimating the biodiversity of Planning Domain 5 (Marion and Prince Edward Islands – Del Cano – Crozet) for ecoregionalisation

The CCAMLR MPA Workshop on Marine Protected Areas, held in Brest (France) in August 2011, recommended that the Scientific Committee considers supporting three technical workshops including one specific to Planning Domain 5. Planning Domain 5 includes Marion and Prince Edward Islands, the Del Cano Rise and the Crozet Archipelago in the north. It also includes the Ob and Lena seamounts. The workshop focusing on Planning Domain 5 was held in St Pierre, La Réunion, France from 15th May to 18th May, 2012 at the headquarters of TAAF (French Southern and Antarctic Territories). It followed a meeting on the northern part of Planning Domain 5, which was held in South Africa in 2008, organized and funded by WWF South Africa and known as Del Cano 1. The intention of the CCAMLR workshop was to study the ecological values and the use of the marine environment and to identify possible threats that might occur in this area. It extended the Del Cano 1 study spatially and also ecologically to include the benthic and pelagic realms. Identification of objectives for Conservation Planning and future research were discussed in relation to national and international projects. Depending on the availability of data, the approach was based on mapping species distributions (either observed data or predictions for species or community presence/abundance based on environmental factors). Various national and international datasets were used including data from CCAMLR. However, South African and French data relevant to the Planning Domain 5 and surrounding domains were a major focus in the workshop because these CCAMLR member nations are the major scientific actors in this region. Species distributions were visualized by the mean of a Geographic Information System. Available Norwegian data from the Bouvetøya region were also discussed, but this region is less studied compared to the Planning Domain 5. The workshop provided benthic and pelagic abiotic classifications of the Planning Domain using geographic and oceanographic features. Distributions of plankton, mesopelagic fish and top predators were consistent with the abiotic regionalization showing latitudinal patterns of communities for the pelagic species. The importance of frontal zones such as the Antarctic Polar Front and especially the Subantarctic Front were highlighted. North of the CCAMLR area, the Agulhas Return Current has a strong influence on this region. The latitudinal zonation of bioregions according to frontal zones may be influenced by climate change. This will have consequences for marine bird and mammal populations as it will change the habitat of their main pelagic prey species (e.g. euphausiids, squids, mesopelagic fish, etc.). The working group concluded that ecoregionalisation has to be conducted at the scale of plateaus which includes Prince Edward Islands, Del Cano Rise and Crozet Islands i.e. a more detailed level than what has been done to date. High productive pelagic areas must be considered in relation to the bathymetry, iron enrichment, fronts and island mass effects, which contrast with high nutrient low chlorophyll areas farther south. Ichtyofauna and benthos were described as being characteristic of the subantarctic zone with some species being endemic. However, cryptic benthic species have not yet been studied. The French and South African islands support substantial colonies of seabirds and seals, which for several species have global importance. For example, the Crozet and Prince Edward Islands together host the entire population of Crozet shag, about 70% of the world population of wandering albatross, 54% of king penguin, 33% of Indian yellow-nosed albatross, 33% of subantarctic fur seal, 27% of sooty albatross and 21% of the world’s southern rockhopper penguin. The high productivity in the vicinity of the islands, together with the large aggregations of seabirds and seals found at the islands, attract various other animals, e.g. several cetaceans, to their vicinity. The populations of several seabirds that breed at the islands have decreased. There is accumulating evidence that decreases of albatrosses and petrels have been substantially influenced by by-catch mortality in fisheries, whereas decreases in some penguins are probably attributable to decreased availability of prey that may have been caused by environmental change. Although the islands themselves enjoy a protected status and fishing is at present excluded within 12 nautical miles of the islands, providing some protection to inshore-foraging species, many of the seabirds and seals range well beyond the immediate precincts of the islands. Some circumnavigate Antarctica and others move to the north well beyond the CCAMLR convention area. Hence, many seabirds and seals are affected by human activities, and almost certainly environmental change, in other CCAMLR domains as well as in regions of the high seas that are administered by other Regional Fisheries Management Organisations. In particular the CCAMLR Planning domains that neighbour Domain 5 are of importance, as is the southern region of the Indian Ocean Tuna Commission (IOTC, FAO Area 51). Human activities in these other areas adversely influence the conservation status of animals from Planning Domain 5, as is the case with by-catch mortality, it will be necessary for CCAMLR to work in close association with other Regional Fisheries Management Organisations (e.g. IOTC), treaties (e.g. Agreement on the Conservation of Albatrosses and Petrels, ACAP) and conservation organisations (e.g. BirdLife International) to achieve a favourable conservation status for species that are at present Threatened or Near Threatened. The problem is sometimes compounded by albatrosses and petrels segregating their at-sea distributions by sex or age or both, so that components of populations may suffer particularly high mortality leading, e.g., to sex imbalances or inadequate recruitment into breeding populations. Preliminary models suggest that both topographical (e.g. plateau and rises) and oceanographic (e.g. locations of fronts) features play important roles in defining good foraging grounds for some wide-ranging predators. Whereas topographical features are permanent, the locations of oceanographic features may be changing, thereby presenting a greater challenge for spatial conservation planning. For some albatrosses (notably Thalassarche spp.) and penguins (notably Eudyptes spp.) there is accumulating evidence that populations and species may segregate their feeding grounds, which also will need to be accounted for in any form of spatial conservation planning. The Working group noted set of preliminary strategic points essential to Systematic Conservation Planning, which include accounting for ecological relationships with surrounding areas (Bouvet to the West, Kerguelen to the East and East Antarctica to the South). The working group concluded that subtropical areas north of the Planning Domain 5 should be included in the planning, because of the spatial range covered by top predators, and also because the limit of the CCAMLR area cuts across the EEZs of both the Prince Edward and the Crozet Islands, as well as the Del Cano Rise. Strategic points include: First of all, biodiversity features needed to be mapped. The workshop concentrated on this objective most of the time. Second, biodiversity targets need to be determined. France will see how to adapt the ones that were used by Lombard et al. (2007) for the EEZ of the Prince Edward Islands, to the Crozet Islands. For the high seas, the working group recommended that the definition of targets should be discussed by EMM and the MPA circumpolar workshop. Third, the Working Group started to evaluate pressures and areas of research that need to be defined (spawning and nursery areas, bycatch, interactions with killer whales, etc.). The involvement of stakeholders was discussed, including fishing industries, NGOs, other relevant treaties and CCAMLR members for the high sea areas. This general theme has to be more specifically discussed during the circumpolar workshop and at the SC. The workshop also considered MPAs existing under national jurisdiction in the Planning Domain, procedures to extend them, and the need for strengthened cooperation between CCAMLR and other relevant legal instruments, organizations and initiatives. To achieve these goals, research and monitoring were discussed under three headings: (1) census of biodiversity, (2) ecoregionalisation classification and (3) monitoring. Such research would make up for a current lack of data, e.g. with regard to the benthos (deep and shallow), the mesopelagic zone and plankton. With regard to monitoring ecological processes, especially at the northern limits of the CCAMLR area, CCAMLR may wish to broaden the lists of species and environmental parameters that are monitored, to consider parameters of species that may best reflect change associated with global warming and, if necessary, develop protocols for any new parameters to be monitored. This would naturally include the use of the Continuous Plankton Recorder and tracking for birds, seals and mammals