Phaeocystis globosa (Prymnesiophyceae) colonies: hollow structures built with small amounts of polysaccharides

Rijssel, Marion van; Hamm, Christian; Gieskes, W.W.C.

doi:10.1017/s0967026297001108

Cited by 28 publications

(38 citation statements)

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“…from Tasman Bay, New Zealand, show that the matrix has a multilayered gelatinous structure, with an average thickness of 5 lm (Chang 1984). Van Rijssel et al (1997) calculated a thickness of 7 lm based on carbohydrate measurements and the assumption of a mucous layer with a fixed thickness for various colony sizes, whereas a thickness of 10 lm was determined based on confocal laser scanning imagery. As colonial cells of Phaeocystis have similar (Baumann et al 1994), or even higher growth rates compared to single cells, the allocation of the material needed to build the colonial matrix obviously does not hamper cell metabolism.…”

Section: Mucopolysaccharidesmentioning

confidence: 99%

The carbohydrates of Phaeocystis and their degradation in the microbial food web

2007

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The ubiquity and high productivity associated with blooms of colonial Phaeocystis makes it an important contributor to the global carbon cycle. During blooms organic matter that is rich in carbohydrates is produced. We distinguish five different pools of carbohydrates produced by Phaeocystis. Like all plants and algal cells, both solitary and colonial cells produce (1) structural carbohydrates, (hetero) polysaccharides that are mainly part of the cell wall, (2) mono-and oligosaccharides, which are present as intermediates in the synthesis and catabolism of cell components, and (3) intracellular storage glucan. Colonial cells of Phaeocystis excrete (4) mucopolysaccharides, heteropolysaccharides that are the main constituent of the mucous colony matrix and (5) dissolved organic matter (DOM) rich in carbohydrates, which is mainly excreted by colonial cells. In this review the characteristics of these pools are discussed and quantitative data are summarized. During the exponential growth phase, the ratio of carbohydrate-carbon (C) to particulate organic carbon (POC) is approximately 0.1. When nutrients are limited, Phaeocystis blooms reach a stationary growth phase, during which excess energy is stored as carbohydrates. This so-called overflow metabolism increases the ratio of carbohydrate-C to POC to 0.4-0.6 during the stationary phase, leading to an increase in the C/N and C/P ratios of Phaeocystis organic matter. Overflow metabolism can be channeled towards both glucan and mucopolysaccharides. Summarizing the available data reveals that during the stationary phase of a bloom glucan contributes 0-51% to POC, whereas mucopolysaccharides contribute 5-60%. At the end of a bloom, lysis of Phaeocystis cells and deterioration of colonies leads to a massive release of DOM rich in glucan and mucopolysaccharides. Laboratory studies have revealed that this organic matter is potentially readily degradable by heterotrophic bacteria. However, observations in the field of accumulation of DOM and foam indicate that microbial degradation is hampered. The high C/N and C/P ratios of Phaeocystis organic matter may lead to nutrient limitation of microbial degradation, thereby prolonging degradation times. Over time polysaccharides tend to self-assemble into hydrogels. This may have a profound effect on carbon cycling, since hydrogels provide a vehicle to move DOM up the size spectrum to sizes subject to sedimentation. In

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Section: Mucopolysaccharidesmentioning

confidence: 99%

The carbohydrates of Phaeocystis and their degradation in the microbial food web

2007

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“…Pectin degradation, for example, requires the action of different enzymes, each releasing fragments of different composition. The pectin chains contain so-called ''hairy regions,'' with varying monosaccharide ratios resulting from unevenly distributed neutral sugar side chains (van Rijssel 1992). In spite of the gradual decrease in the rate of degradation of the Phaeocystis (NS) mucopolysaccharides (Fig.…”

Section: Effects Of Mucopolysaccharide Composition On Its Degradationmentioning

confidence: 99%

Microbial breakdown of Phaeocystis mucopolysaccharides

Janse

Rijssel

Ottema

et al. 1999

Limnology & Oceanography

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Mucus from the microalga Phaeocystis was partially purified and used as the C source in various stable enrichment cultures wherein the mucus carbohydrates were degraded under oxic as well as anoxic conditions. The breakdown of mucopolysaccharides (initially at a rate of 50% in 11 d at 12ЊC) markedly slowed after about 15 d, leaving a fraction nondegraded. The carbohydrate composition of the residual fraction did not change during breakdown. It was shown that the incomplete degradation of mucopolysaccharides was not due to inherent resistance to breakdown in parts of the mucus carbohydrates but to the release of inhibitors produced during breakdown. The (potentially high) overall degradability of mucopolysaccharides has important consequences for the fate of C fixed by Phaeocystis. The balance between recycling of Phaeocystis biomass in surface waters and its accumulation, sedimentation, and burial in the sediment will greatly depend on factors such as nutrient availability, presence of inhibiting agents, and composition of the microbial community, rather than on structural impediments inhibiting mucopolysaccharide degradation.

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“…In a P. globosa colony, individual cells are distributed within a mucous envelope while the colony interior remains fluid-filled [4]. Hence, the density of a colony is determined by the combined density of colonial cells, mucous envelope and interior fluid.…”

Section: Effects Of Colony Structures and Growth Phases On Buoyancymentioning

confidence: 99%

“…Peperzak et al estimated the density of colonial cells to be 1090 kg m -3 under nutrient replete condition [21], which is denser than the seawater in our experiments (~1009.7 kg m -3 ). The mucous envelope is believed to be made of primarily carbohydrates, but its composition remains largely unknown [4]; hence, estimating its density is difficult. Nonetheless, colonial mucous with no or few cells is commonly found in sediment traps [42].…”

Section: Effects Of Colony Structures and Growth Phases On Buoyancymentioning

confidence: 99%

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Buoyancy Regulation in Phaeocystis globosa Scherffel Colonies

Wang¹

2010

TOMBJ

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Buoyancy of Phaeocystis globosa Scherffel (Prymnesiophyceae) colonies was investigated by measuring the vertical distribution of colonies in quiescent water where convection had been removed. Over 60% of the colonies exhibited negative buoyancy regardless of light condition or growth phase. Positively and neutrally buoyant colonies lost their buoyancy in the dark, but regained buoyancy upon return to the light. Colonies with closer cell packing; i.e., more cells per unit colonial surface area, had greater capability to remain buoyant. Our results suggest that colony buoyancy was not uniform within a P. globosa population, and that biological regulation of colony buoyancy required light energy.

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Phaeocystis globosa (Prymnesiophyceae) colonies: hollow structures built with small amounts of polysaccharides

Cited by 28 publications

References 0 publications

The carbohydrates of Phaeocystis and their degradation in the microbial food web

The carbohydrates of Phaeocystis and their degradation in the microbial food web

Microbial breakdown of Phaeocystis mucopolysaccharides

Buoyancy Regulation in Phaeocystis globosa Scherffel Colonies

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