Marine productivity enhancement around Bouvet and the South Sandwich Islands (Southern Ocean)

Abstract

Selected physico-chemical and biological properties were compared between shelf and deep oceanic waters in the vicinity of Bouvet and the South Sandwich Islands during the austral summers of 1982-1983 and 1990-1991. On 3 of these occasions circuminsular chlorophyll a levels were 3 to 7 mg chl a m-3, an increase of 3 to 4 times over off-shore stations. At South Sandwich in 1990-1991 high phaeopigment levels indicated senescence of the phytoplankton bloom and primary production on this occasion was not markedly greater than in off-shore waters. On 2 occasions (Bouvet 1990, South Sandwich 1982 high chlorophyll concentrations were associated with a marked increase in production (up to ca 280 mg C m-' h-' in 1982-1983 and ca 1.5 mg C m-3 h- ' in 1990-1991). This combination of high chl a and production levels was associated with depletion of dissolved nutrients. Size fractionation during summer 1990-1991 indcated dominance (ca 70 % of total chl) by netphytoplankton (20 to 200 pm) at Bouvet and by nanoplankton (1 to 20 ym, 70 % of total chl) at South Sandwich. Sharp drops in temperature and salinity over the island shelves, and spatial covariance between upper mixed layer depth and chl a concentration, suggest that stabilisation by meltwater may be the main cause of phytoplankton bloom formation. The present and published data suggest a longitudinal trend of decreasing phytoplankton production from Antarctic Peninsula archipelagos to islands in the Indian Ocean sector of the Southern Ocean. This may have implications for the estimation of total carbon f l u in Antarctic waters.

Substantial open-ocean phytoplankton blooms to the north of South Georgia, South Atlantic, during summer

“…Enhanced production or accumulated biomass, due to shelf-break and island-mass effects, have previously been observed near to South Georgia and other subantarctic islands (e.g Priddle et al 1986, Perissinotto et al 1992, Whitehouse et al 1993). However, these mechanisms are unlikely to be responsible for generating the phytoplankton blooms in the present study as they occurred in the deep ocean (>3000 m), 150 km or more to the northwest of South Georgia.…”

“…Similar concentrations have also been recorded in frontal zones that receive inputs of warmer water or nutrients, or that are seeded from upstream (Lutjeharms e t al. 1985, Jacques & Panouse 1991, Perissinotto et al 1992, Bury et al 1995, Savidge e t al. 1995.…”

“…1995. However, by far the highest chlorophyll concentrations (up to 30 m g 1 r 3 ) have been measured in neritic areas, associated with a variety of islandmass effects including water column stability and nutrient enrichment derived from island runoff (Heywood & Priddle 1987, Boden 1988, Jacques 1989, Holm-Hansen & Mitchell 1991, Perissinotto et al 1992.…”

Missing link in the Southern Ocean: sampling the marine benthic fauna of remote Bouvet Island

“…Benthic marine fauna in the vicinity of the island was collected on three major expeditions: the ''Deutsche Tiefsee Expedition '' 1898'' -1899'' (e.g. Thiele 1904'' , 1925Thiele and Jaeckel 1931), the ''Discovery' ' Expeditions 1926' Expeditions -1937 (Powell 1951;Dell 1964), and the Norwegian Antarctic Expeditions 1927-1930(Bergenhayn 1937Soot-Ryen 1951), whereas in more recent times the emphasis has been on plankton research (Fevolden 1980;Perissinotto et al 1992). The 50 km 2 ice-covered, volcanically active island under Norwegian authority has mainly attracted study because of the unusual geologic and volcanic properties (Furnes and Løvlie 1978), reflecting its young geological age of just 1 Ma (Prestvik and Winsnes 1981).…”

Mesoscale surface distribution of biogeochemical characteristics in the Crozet Basin frontal zones (South Indian Ocean)

“…However, in situ studies and satellite observations indicate higher productivity and chlorophyll biomass in a variety of disparate regions. Phytoplankton blooms have been observed in the marginal ice zone (Smith & Nelson 1990, Sullivan et al 1993, around islands (Perissinotto et al 1992, Pakhomov & Froneman 1999, Blain et al 2001) and along frontal zones (Laubscher et al 1993, Bathmann et al 1997. Fronts are regions of strong horizontal temperature and/or salinity gradients that may occur in lakes, rivers and oceans (Franks 1992).…”