Predictions of Ecological Effects of Artificial Upwelling in Semi-Enclosed Bay and Enclosed Lake

An apparatus, which mixes waters in upper and lower layers in density stratification and discharges the mixture at the middle depth, has made a remarkable success in enhancing water quality for ecosystems in a small semi-enclosed bay and an enclose lake in Japan. In this study, we conducted numerical simulations by using a three-dimensional tidal current model and an ecosystem model to predict the effects of the apparatus in two different waters: a larger semi-enclosed bay and an enclosed lake. Isahaya Bay in Ariake Sea was chosen as the former case to see how effectively the apparatus can reduce oxygen-deficient water, and Feng-Shan dam-lake located in South Taiwan represents the latter case, where we are interested in the effect of the apparatus on reduction of Microcystis aeruginosa, which is harmful blue-green alga and causes environmental problems in the neighbouring area. As a result, it is suggested that the apparatus averages temperature of water vertically in its vicinity and this increases phytoplankton in the lower layers resulting in reducing oxygen-deficient water in Isahaya Bay. However, it is not very effective in reducing the blue-green alga in the Taiwanese lake because the temperature in the lower layer is still preferable for the alga even after the mixing.

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Three-Dimensional Ultrastructure of Agmenellum Quadruplicatum

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100054200 ◽

1982 ◽

Vol 40 ◽

pp. 318-319

Author(s):

S. A. Nierzwicki ◽

D. L. Balkwil ◽

S. E. Stevens

Keyword(s):

Green Alga ◽

Three Dimensional ◽

Cyanobacterial Cell ◽

Blue Green Alga ◽

Unicellular Cyanobacterium ◽

Cell Structures ◽

Agmenellum Quadruplicatum ◽

Fine Structures ◽

First Time

Agmenellum quadruplicatum is a unicellular cyanobacterium (blue-green alga) measuring ≃2.5 x 5.0 μm. The basic ultrastructural features of this organism have been characterized previously, but there have been no reports fully describing the three-dimensional organization of these features within the cell. Yet, such information would be valuable in regard to understanding the mechanism by which cell structures in cyanobacteria function. The purpose of this study, then, was to reconstruct for the first time the three-dimensional arrangement of fine structures in a cyanobacterial cell.

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Effect of Iron Limitation on the Ultrastructure of Agmenellum Quadruplicatum

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100098551 ◽

1981 ◽

Vol 39 ◽

pp. 410-411

Author(s):

L. P. Hardie ◽

D. L. Balkwill ◽

S. E. Stevens

Keyword(s):

Growth Medium ◽

Green Alga ◽

Natural Habitat ◽

Iron Limitation ◽

Natural Environments ◽

Blue Green Alga ◽

Marine Cyanobacterium ◽

Natural Systems ◽

Thin Sectioning ◽

Agmenellum Quadruplicatum

Agmenellum quadruplicatum is a unicellular, non-nitrogen-fixing, marine cyanobacterium (blue-green alga). The ultrastructure of this organism, when grown in the laboratory with all necessary nutrients, has been characterized thoroughly. In contrast, little is known of its ultrastructure in the specific nutrient-limiting conditions typical of its natural habitat. Iron is one of the nutrients likely to limit this organism in such natural environments. It is also of great importance metabolically, being required for both photosynthesis and assimilation of nitrate. The purpose of this study was to assess the effects (if any) of iron limitation on the ultrastructure of A. quadruplicatum. It was part of a broader endeavor to elucidate the ultrastructure of cyanobacteria in natural systemsActively growing cells were placed in a growth medium containing 1% of its usual iron. The cultures were then sampled periodically for 10 days and prepared for thin sectioning TEM to assess the effects of iron limitation.

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