exceed 50 μM south of ∼62°S.
(^) Several subantarctic mesoscale iron-enrichment experiments (SoFEX and
LOHAFEX) have been carried out late in summer, an appropriate season if iron were
to be used to enhance deep-sea carbon sequestration. Both failed to generate
significant blooms of large diatoms. The SoFEX “north” addition (Coale et al. 2004)
in the eastern Pacific subantarctic (∼54°S, with ∼3 μM Si(OH) 4 ) did stimulate
increase of flagellated phytoplankton and some Pseudonitzschia (small diatoms),
while LOHAFEX (Smetacek 2009) weakly enhanced stocks of flagellated
phytoplankton, but also of grazing pteropods and copepods, particularly the regionally
endemic Clausocalanus laticeps. Predatory amphipods also strongly increased,
presumably eating the grazers.
(^) At least one abundant, circumglobal, subantarctic copepod, Neocalanus tonsus, has
a lipid-loading and diapause scheme resembling that of the subarctic Pacific
dominants. Like its subarctic congeners, it matures, mates, and females initiate
spawning at the resting depth. However, unlike the Pacific species, females retain
feeding mouthparts and ascend to the surface to continue spawning while feeding
(Ohman et al. 1989). Calanus simillimus shares dominance among larger copepods in
the subantarctic, its distribution extending across the PF into northern antarctic
waters. It apparently is distantly related to other Calanus species (Hill et al. 2001), but
it retains their life-history pattern of deep winter diapause, the females feeding to
produce eggs. It runs through several generational cycles in the productive season
(Ward et al. 1996). A suite of small copepods, Limacina, salps, and euphausiids are
also present. Clupeids or other small, schooling fish are apparently few, apart from
coastal regions off South America. Vertically migrating midwater fish and
ommastrephid squid are, however, important and support stocks of island-breeding fur
seals, sea lions, elephant seals, and endemic seabirds, e.g. wandering albatross
(Diomedia exulans), several species of giant petrels (Macronectes), and of small
petrels (Procellaria). Endemic epibenthic fish are (or were – they have been
overfished) abundant on shelves and over seamounts, including sundry notothenids
tolerant of extreme cold and occurring also farther south. Commercially important
species have been Patagonian toothfish (Dissostichus eleginoides), orange roughy
(Hoplostethus atlanticus), hoki (Macruronus novaezelandiae), and a southern hake
(Merluccius australis).
The Arctic Ocean
(^) The Arctic Ocean is the smallest and most land-locked of the named oceans. Pacific
Ocean water flows in through the Bering Strait and contributes about 24% of the
seawater exchange in the Arctic Ocean. Atlantic water flows in through the Fram
Strait and Barents Sea and comprises the remaining 76% of exchange. There is a