Seabird guano enhances phytoplankton production in the Southern Ocean

In the Southern Ocean, inorganic macronutrients are very rarely depleted by phytoplankton growth. This has led to speculation on possible additional CO 2 drawdown in this region. However, the effects of climate change can only be predicted once the role of environmental and biotic factors limiting phytoplankton carbon fixation are understood. It is clear that the Southern Ocean is heterogeneous, and no single factor controls prim ary production overall. Ice cover and vertical mixing influence algal growth rates by m odulating radiance flux. Micronutrients, especially iron, may limit growth in some areas. Primary production is also suppressed by high removal rates of algal biomass. Grazing by zooplankton is the major factor determining magnitude and quality of vertical particle flux. Several of the physical controls on phytoplankton production are sensitive to climate change. Although it is impossible to make numerical predictions of future change on the basis of our present knowledge, qualitative assessments can be put forward on the basis of model predictions of climate change and known factors controlling prim ary production. Changes in water temperature and in windinduced mixing are likely to be slight and have little effect. Model predictions of changes in sea-ice cover vary widely, making prediction of biogeochemical effects impossible. Even if climatic change induces increased nutrient uptake, there are several reasons to suspect that carbon sequestration will be ineffective in comparison with continuing anthropogenic CO 2 emission.

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Impact of sea ice on the marine iron cycle and phytoplankton productivity

Biogeosciences ◽

10.5194/bg-11-4713-2014 ◽

2014 ◽

Vol 11 (17) ◽

pp. 4713-4731 ◽

Cited By ~ 42

Author(s):

S. Wang ◽

D. Bailey ◽

K. Lindsay ◽

J. K. Moore ◽

M. Holland

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Ice Cover ◽

Arctic Sea Ice ◽

The Arctic ◽

Phytoplankton Production ◽

Iron Cycle ◽

Surface Ocean ◽

Antarctic Sea Ice ◽

Iron Concentrations

Abstract. Iron is a key nutrient for phytoplankton growth in the surface ocean. At high latitudes, the iron cycle is closely related to the dynamics of sea ice. In recent decades, Arctic sea ice cover has been declining rapidly and Antarctic sea ice has exhibited large regional trends. A significant reduction of sea ice in both hemispheres is projected in future climate scenarios. In order to adequately study the effect of sea ice on the polar iron cycle, sea ice bearing iron was incorporated in the Community Earth System Model (CESM). Sea ice acts as a reservoir for iron during winter and releases the trace metal to the surface ocean in spring and summer. Simulated iron concentrations in sea ice generally agree with observations in regions where iron concentrations are relatively low. The maximum iron concentrations simulated in Arctic and Antarctic sea ice are much lower than observed, which is likely due to underestimation of iron inputs to sea ice or missing mechanisms. The largest iron source to sea ice is suspended sediments, contributing fluxes of iron of 2.2 × 108 mol Fe month−1 in the Arctic and 4.1 × 106 mol Fe month−1 in the Southern Ocean during summer. As a result of the iron flux from ice, iron concentrations increase significantly in the Arctic. Iron released from melting ice increases phytoplankton production in spring and summer and shifts phytoplankton community composition in the Southern Ocean. Results for the period of 1998 to 2007 indicate that a reduction of sea ice in the Southern Ocean will have a negative influence on phytoplankton production. Iron transport by sea ice appears to be an important process bringing iron to the central Arctic. The impact of ice to ocean iron fluxes on marine ecosystems is negligible in the current Arctic Ocean, as iron is not typically the growth-limiting nutrient. However, it may become a more important factor in the future, particularly in the central Arctic, as iron concentrations will decrease with declining sea ice cover and transport.

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Phytoplankton community structure is influenced by seabird guano enrichment in the Southern Ocean

Estuarine Coastal and Shelf Science ◽

10.1016/j.ecss.2017.04.021 ◽

2017 ◽

Vol 191 ◽

pp. 125-135 ◽

Cited By ~ 6

Author(s):

O.A. Shatova ◽

S.R. Wing ◽

L.J. Hoffmann ◽

L.C. Wing ◽

M. Gault-Ringold

Keyword(s):

Community Structure ◽

Southern Ocean ◽

Phytoplankton Community ◽

Phytoplankton Community Structure ◽

Seabird Guano

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Phytoplankton production characteristics in the Eastern Atlantic and Atlantic sector of the Southern Ocean in October–November 2004

Oceanology ◽

10.1134/s0001437008030089 ◽

2008 ◽

Vol 48 (3) ◽

pp. 364-377 ◽

Cited By ~ 2

Author(s):

A. B. Demidov ◽

V. I. Vedernikov ◽

V. I. Gagarin ◽

V. I. Burenkov

Keyword(s):

Southern Ocean ◽

Phytoplankton Production ◽

Atlantic Sector ◽

Production Characteristics

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Impacts of sea ice on the marine iron cycle and phytoplankton productivity

Biogeosciences Discussions ◽

10.5194/bgd-11-2383-2014 ◽

2014 ◽

Vol 11 (2) ◽

pp. 2383-2418 ◽

Cited By ~ 4

Author(s):

S. Wang ◽

D. Bailey ◽

K. Lindsay ◽

K. Moore ◽

M. Holland

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Arctic Sea Ice ◽

The Arctic ◽

Phytoplankton Production ◽

Iron Cycle ◽

Surface Ocean ◽

Antarctic Sea Ice ◽

Arctic Sea ◽

Iron Concentrations

Abstract. Iron is a key nutrient for phytoplankton growth in the surface ocean. At high latitudes, the iron cycle is closely related to sea ice. In recent decades, Arctic sea ice cover has been declining rapidly and Antarctic sea ice has exhibited large regional trends. A significant reduction of sea ice in both hemispheres is projected in future climate scenarios. To study impacts of sea ice on the iron cycle, iron sequestration in ice is incorporated to the Biogeochemical Elemental Cycling (BEC) model. Sea ice acts as a reservoir of iron during winter and releases iron to the surface ocean in spring and summer. Simulated iron concentrations in sea ice generally agree with observations, in regions where iron concentrations are lower. The maximum iron concentrations simulated in the Arctic sea ice and the Antarctic sea ice are 192 nM and 134 nM, respectively. These values are much lower than observed, which is likely due to missing biological processes in sea ice. The largest iron source to sea ice is suspended sediments, contributing fluxes of iron of 2.2 × 108 mol Fe month−1 to the Arctic and 4.1 × 106 mol Fe month−1 to the Southern Ocean during summer. As a result of the iron flux from ice, iron concentrations increase significantly in the Arctic. Iron released from melting ice increases phytoplankton production in spring and summer and shifts phytoplankton community composition in the Southern Ocean. Simulation results for the period of 1998 to 2007 indicate that a reduction of sea ice in the Southern Ocean will have a negative influence on phytoplankton production. Iron transport by sea ice appears to be an important process bringing iron to the central Arctic. Impacts of iron fluxes from ice to ocean on marine ecosystems are negligible in the current Arctic Ocean, as iron is not typically the growth-limiting nutrient. However, it may become a more important factor in the future, particularly in the central Arctic, as iron concentrations will decrease with declining sea ice cover and transport.

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