BLUEGREEN ALGAE  The Kingdom EUBACTERIA (or PROKARYOTAE) includes the phototrophic bacteria, the blue-green members of which are called cyanobacteria. The cells of these prokaryote "algae" are quite different from those of all other algae (the eukaryotes) and resemble in many ways the cells of other bacteria. Nonetheless, most cyanobacters or blue-greens look much like other algae macroscopically, and are often the most commonly encountered algae in Hawai‘i freshwater streams. Bacteria are well known to inhabit environments characterized by extremes in temperature and salinity, and blue-greens are the dominant algal types in unusual aquatic environments (such as thermal pools, anchialine pools, and hyperhaline lagoons). Some of the filamentous (thread-like) blue-greens are capable of slow movement that is best described as "gliding."

Identification of cyanobacters requires careful examination under a microscope, usually at high power (400X or greater), because the cells are tyically quite small and macroscopic structure of bluegreens often derives from the nature of gelatinous secretions. These secretions vary from being diffluent to firm and conspicuous, and may be partly controlled by environmental conditions. A listing of bluegreen algae described or reported from non-marine, aquatic environments in Hawai‘i is given elsewhere in CPIE. Cyanosite provides an excellent web starting point for obtaining information about the cyanobacteria, with a large collection of photomicrographs of most genera. Another very useful website for understanding the taxonomy of archaea and bacteria is The Prokaryotes.

	40a	(30) & (33)	Cells arranged in rows or chains called trichomes, the trichome usually within a sheath of secreted gelatinous material (the term filament applies to the trichome and sheath together) ~ Order HORMOGONALES	[41]
	40b		Cells not tightly packed (coccoid), arranged either at random or, if in rows, then with some separation between at least small groups of cells. Also, cells typically within a gelatinous envelope ~ Order COCCOGONALES	[81]
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			Figure 1. Drawing of a trichome of Anabaena (X825) showing intercalary heterocyst and gonidium
	41a	(40)	Trichomes with heterocysts (Fig. 1; specialized cells which lack photosynthetic pigments and are typically spherical, larger, and with thicker walls than the vegetative cells)	[42]
	41b		Trichomes without heterocysts ~ Family OSCILLATORIACEAE	[53]
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	42a	(41)	Filaments branching	[43]
	42b		Filaments not branching, although several filaments may share a common outer sheath ~ Family NOSTACACEAE	[44]
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	43a	(42)	True branching, originating by division of a cell with growth in a new direction ~ Family STIGONEMATACEAE	[71]
	43b		False branching only (sheath is branched, but not the trichome) ~ Family NOSTACACEAE	[44]
			Key to Family Nostacaceae
	44a	(42) & (43)	Trichomes long-tapering, diameter decreasing from base to apex	[45]
	44b		Trichomes not long-tapering, diameter constant throughout length	[47]
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	45a	(44)	Trichomes tapering and hair-tipped	[46]
	45b		Trichomes tapering but without hair-like apices; heterocysts typically terminal at the broad end of the trichome, but some heterocysts intercalary. { Typically 2 to 6 trichomes share a common sheath for at least part of their length Dichothrix baueriana Dichothrix fusca
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	46a	(45)	Thallus solid, hard, even stony, and usually hemispherical, or colonies confluent. Filaments radiating from the center. Trichomes 4 to 7.5 microns diameter -= as Rivularia haematites (DC) C.Ag.
	46b		Thallus not hard or stone-like; filaments either isolated or radiating from a central point or growing crowded in dense tufts Calothrix braunii Calothrix fusca
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	47a	(44)	Trichomes moderately to deeply constricted at nodes (bead-like); cells appear like a row of attached spheres (see Fig. 1) or as cylinders with rounded ends	[48]
	47b		Trichomes not constricted or only slightly constricted at nodes (cells appear like attached disks or cylinders without rounded ends). Heterocysts present and mostly intercalary, but some may be terminal. Sheath present, enclosing trichomes with minimal or conspicuous false branching.	[60]
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	48a	(47)	Heterocysts always terminal (at one or both ends of a chain); a gonidium (enlarged reproductive body) may be present adjacent to heterocyst. { Cells more or less barrel-shaped. Cylindrospermum catenatum Cylindrospermum stagnale Cylindrospermum sp.
	48b		Heterocysts usually intercalary (between vegetative cells), at base of trichome in branched sheath ~ Tolypothrix
	48c		Heterocysts intercalary	[49]
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	49a	(48)	Trichomes twisting and intertwined, aggregated within a firm gelatinous mass forming a macroscopic thallus (e.g., shiney, usually dark, rounded masses to 0.5 cm) Genus: Nostoc (8+ species)
	49b		Trichomes twisting and intertwined, but if aggregated, the gelatinous mass is loose, coming apart easily Anabaena catenula Anabaena sp.
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			Key to Family Oscillatoriaceae
	53a	(41)	Trichomes spiral, without cross walls Spirulina subsalsa Oersted
	53b		Trichomes not spiral; with cross walls (multicellular)	[54]
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	54a	(53)	Filaments surrounded by a sheath and sometimes entangled to form a conspicuous mat-like structure. { End wall of apical cell not thickened	[55]
	54b		Filaments not surrounded by a sheath. { End wall of apical cell thickened if mature Genus: Oscillatoria (8+ species)
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	55a	(54)	Mat-like growth conspicuous	[56]
	55b		Filaments may be entangled, but not forming large mats Genus: Lyngbya (5+ species)
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	56a	(55)	Two or more filaments seen in a single surrounding sheath. { Apical cells tapering Genus: Schizothrix (4 species)
	56b		Only a single filament present within a surrounding sheath. { Apical cells may or may not be tapering [see Note E] Genus: Phormidium (17+ species)	[57]
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	57a	(56)	Trichomes 1-2 microns in diameter -= Phormidium tenue (Menegn.) Gom.
	57b		Trichomes exceed 3 microns in diameter	[58]
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	58a	(57)	Apex of mature trichomes capitate -= Phormidium subfuscum Kütz
	58b		Apex not capitate	[59]
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	59a	(58)	Trichomes not constricted at cross walls. Apical cell conical.Trichome 3 to 5 microns diameter -= Phormidium inundatum Kütz -= Phormidium papyraceum (C.Ag.) Gom.
	59b		Trichomes scarcely constricted at cross walls. Apical cell truncate. Trichome 4.5 to 12 micron diameter -= Phormidium retzii (C.Ag.) Gom.
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	60a	(47)	False branching conspicuous and typically occuring as paired eruptions of trichomes from the sheath. { Sheath may be thick, layered, and pigmented ~ Family SCYTONEMATACEAE Genus: Scytonema (14+ species)
	60b		False branching occasional. Heterocysts terminal and intercalary ~ Family MICROCHAETACEAE Genus: Microchaete (2 species)
			Key to Family Stigonemataceae
	71a	(43)	Thallus with a main axis composed of multiple filaments of cells (multiseriate) and branched; sheath cartilaginous. Heterocysts present. { Usually pigmented yellow to brown Stigonema mamillosum Stigonema minutum
	71b		Thallus otherwise, but filaments clearly uniseriate (single row of cells) throughout	[72]
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	72a	(71)	Beaded and branched trichomes with heterocysts apical or intercalary or both. { Forming soft-gelatinous globular structures Genus: Nostochopsis (2 species)
	72b		Plants forming firm-gelatinous spheres or irregular masses. Both freshwater streams and marine intertidal Brachytrichia cf. quoyi (C.Ag.) Bornet and Flahailt
	72c		Thallus otherwise: boring into limestone	[Note D]

Note D:

Your identification is leading to a group with no aquatic representatives reported from Hawai'i, or reported only from euhaline (marine) habitats. It is likely that a majority of the known genera of Cyanophyta are represented in the Hawaiian Islands, but have just not been recorded from here. Thus, your choices in preceeding couplets may well be correct. Efforts at the University of Hawai'i Botany Department (e.g., Sherwood, 2004) is correcting these deficiencies.

Note E:

When Dr. Francis Drouet revised the classification and taxonomy of bluegreen algae, he attempted to reduce the proliferation of species based upon characteristics that vary with environmental conditions. Many species, genera, and even families were combined into a system that uses cell morphology (and encourages culture techniques) while tending to ignore characteristics of the sheath or gelatinous matrix and other environmentally influenced growth forms (ecophenes). While simpler and closer to the species concept in application, the Drouet approach lumps together many previously described species that may represent ecotypes or ecophenes of value to the environmental scientist. The approach used here is that recommended by Humm and Wicks (1980) to combine "Drouet's carefully devised taxonony" with older names to preserve the descriptive biology these represent. Genus and/or species names in bold type follow Drouet; species names preceeded by -= may be synonyms under Drouet's system (or are in an invalid genus).