Determining Microcystis spp. in relation to their likelihood to contain microcystin

Micrographs showing morphological characteristics of Microcystis colonies (morphospecies): From Via-Ordorika et al. 2004

(A) M. aeruginosa (young colony), (B) M. ichthyoblabe

(C) M. botrys, (D) M. wesenbergii

(E) M. flos-aquae, (F) M. viridis.

Morphological characteristics of Microcystis colonies (morphospecies)

Differential phenotype characters are marked by asterisks. Diameter of cells = (min) range (max)

	M. ichthyoblabe	M. panniformis	M. flos-aquae	M. aeruginosa	M. botrys	M. viridis	M. wesenbergii
diameter of cells	2 - 3.2 (3.8) *	(2.5) 3 - 4.6 (4.8) *	(3) 3.5 – 4.8 (5.6)	(3.5) 4 – 6.5 *	4.9 - 7	(3) 4 – 7.9 *	4 – 8.5 (10) *
shape of colonies	irregular, without holes, often flattened, forming up to large, irregular compact colonies, sometimes with small clusters of cells in their mass; disintegrating in mass of solitary cells *	± flattened up to monolayers, later spherical to irregular, with ± evenly aggregated cells, sometimes with small and indistinct holes; disintegrating in small groups *	irregular spheroidal, compact, not lobate, without holes, only with places with scarce cells *	irregular in outline, lobate, older with distinct holes *	± spherical subcolonies, often joined irregularly together, not distinctly lobate, without holes	composed from typical packet-like subcolonies, irregularly agglomerated and then usually elongated *	irregular in outline, typical spheroidal, lobate, elongated and with holes; sometimes composed of spherical subcolonies *
size of colonies	microscopic up to macroscopic; in massive development macroscopic and heavy “water blooms”	microscopic up to macroscopic, forming pulverous “water blooms”	microscopic, only in strong development (rare) forming fine, pulverous “water blooms”	initial stages microscopic, later macroscopic colonies, forming often heavy “water blooms”	microscopic, only agglomerations of colonies macroscopically visible; sometimes slight water-blooms	microscopic, only agglomerations of colonies macroscopically visible; usually participating on water-blooms of other species	microscopic up to macroscopic, sometimes forming slight (rarely strong) water-blooms
cell density	densely regularly (homogeneously) and evenly agglomerated	regularly densely and evenly agglomerated, sometimes in indistinct rows *	very densely and irregularly agglomerated cells *	± densely and irregularly agglomerated cells with irregularities at the margin *	very densely gathered cells; few solitary cells liberated into the enveloping mucilage *	almost cubically to irregularly arranged cells, not very densely, rarely densely *	sparsely to densely agglomerated cells, sometimes situated near the surface of subcolonies *
mucilaginous margin	indistinct, diffuse, slightly and irregularly overlapping cells	indistinct, diffuse, not overlapping clusters of cells; in old colonies irregular outline	indistinct, diffuse, not overlapping clusters of cells	diffuse, slightly overlapping cell agglomerations (usually about 5 µm wide) *	distinct, thick, wide, in form of radial, ± semi-globose, and sometimes with tubular structures (staining!) *	± narrow, hyaline, ± copying the cell clusters, with slightly refractive margin	distinct envelopes around irregular clusters of cells with delimited, refractive, smooth margin
young stages	small, spheroidal clusters of cells, rarely spherical, often with irregular outline	small clusters of cells, flat or circular in outline, soon developing in spheroidal and ± hollow agglomerations	irregular clusters of aggregated cells	small, ±spherical or irregular clusters of cells with various density, usually with distinct mucilaginous margin	small spheroidal groups of densely gathered cells, sometimes aggregated together	small, ± cubical groups of cells, with distinct mucilaginous envelopes, sometimes gathered together	small spherical colonies with few cells, enveloped by distinct, delimited mucilaginous envelopes

How likely are these morphospecies to contain microcystins ? Data from 9 countries and 13 water bodies sampled in2001 by Via-Ordorika et al. 2004 Number of colonies tested (n) and their proportion · containing microcystins (determined by MALDI-TOF; solid shading) and · microcystin (mcy) genes (PCR; grey columns show colonies giving a PCR-product for at least one of mcyB or mcyA; open columns show those testing positive for only mcyB): (A) for each morphospecies; (B) for each water-body

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