Dynamics in carbohydrate composition of Phaeocystis pouchetii colonies during spring blooms in mesocosms

• Published in: Journal of sea research Vol. 55; no. 3; pp. 169 - 181
• Main Authors: Alderkamp, Anne-Carlijn, Nejstgaard, Jens C., Verity, Peter G., Zirbel, Marnie J., Sazhin, Andrey F., van Rijssel, Marion
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-04-2006
• Subjects: Algae; Diel; Glucan; Laminarin; Marine; Mucus; Phaeocystis; Phaeocystis pouchetii; Polysaccharides; ANE, Norway, Hordaland, Bergen; Glucan; Laminarin; Polysaccharides; Mucus; Diel; Algae
• ISSN: 1385-1101; 1873-1414
• DOI: 10.1016/j.seares.2005.10.005

The colony-forming microalgae
Phaeocystis produces two major pools of carbohydrates: mucopolysaccharides in the colony matrix and intracellular storage glucan. Both have different functions and separate degradation pathways in the ecosystem, so a partial precipitation method was developed to distinguish the dynamics of the two pools. Changes in concentration in response to variation in nutrients and irradiance were followed during a spring bloom of
Phaeocystis pouchetii colonies in mesocosms near Bergen, Norway. Upon nutrient limitation, the carbohydrate to carbon ratio of the colonies increased from 15% during the growth phase, to more than 50% during the decline phase. During the growth phase of the bloom, the carbohydrate concentration and composition were influenced by irradiance: glucan concentrations showed strong diel dynamics and increased with higher light levels, whereas mucopolysaccharide concentrations were unaffected. During the exponential growth phase, glucan contributed 6–11% to
P. pouchetii carbon, depending on the time of the day. During the decline of the bloom, the glucan contribution increased up to 60%. We provide further evidence for the concept that the
Phaeocystis colony matrix is built with a relatively small but constant amount of carbohydrates, compared to the large quantities of glucan produced during
Phaeocystis spring blooms. Since a major part of
Phaeocystis primary production is recycled in the water column by bacteria, this vast glucan injection is a potential determinant of the magnitude and composition of the microbial community following a bloom.