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

• Published in: Journal of Sea Research
• Main Authors: Alderkamp, AC, Nejstgaard, JC, Verity, PG, Zirbel, MJ, Sazhin, AF, van Rijssel, M, Sazhin, V.N
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2006
• Subjects: algae; polysaccharides; mucus; glucan; laminarin; diel; BELGIAN COASTAL WATERS; NORTH-SEA; FOOD-WEB; PRYMNESIOPHYCEAE COLONIES; POLYSACCHARIDE HYDROLYSIS; BIOCHEMICAL-COMPOSITION; SOUTHERN-OCEAN; VERTICAL FLUX; TROPHIC FATE; PHYTOPLANKTON; Bergen; Norway; Southern Ocean
• Online Access: https://hdl.handle.net/11370/c1714a57-1231-4693-be29-de53c8b6cf6b; https://research.rug.nl/en/publications/c1714a57-1231-4693-be29-de53c8b6cf6b; https://doi.org/10.1016/j.seares.2005.10.005

The colony-forming microalgae Phaeocystis produces two major pools of carbohydrates: in 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 Phacocystis 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. (c) 2005 Elsevier B.V. All rights reserved.