An investigation into the possible light-shielding role of gas vacuoles in a planktonic blue-green alga |
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Authors: | Harvey Shear AE Walsby |
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Institution: | Department of Marine Biology , University College of North Wales, Marine Science Laboratories , Menai Bridge, LL59 5EH, Gwynedd, Wales |
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Abstract: | When the gas vacuoles of Anabaena flos-aquae Bréb. ex Born. et Flah. are collapsed, the optical properties of the alga change. While this may suggest a light-shielding role, photosynthetic measurements indicate that intact gas vacuoles reduce the light falling on the thylakoids by only 4%, or less. Intact gas vacuoles offer no protection against the lethal effects of ultraviolet light. When the alga is grown at high light intensity the gas vacuoles are fewer in number but are oriented peripherally in the cells. However, this does not markedly affect their light shielding efficiency. Spectrophotometric measurements carried out by others indicate a light shielding role by gas vacuoles in a non-planktonic blue-green alga, Nostoc muscorum Kütz., but do not give a quantitative estimate of this effect. In Anabaena no definite evidence of light-shielding is obtained by such a method. All of the experiments described were conducted with dilute algal suspensions to investigate shielding effects in individual cells. Possible self-shading effects in dense suspensions and surface water blooms require further investigation. |
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Keywords: | bacterial growth Cryptomonas tetrapyrenoidosa Cryptophyta extracellular polysaccharide microbial degradation |
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