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Navicula spp.

Classification
General Close

Pennate

(diatoms) A type of diatom that has longitudinal symmetry with valves that are linear or oval shaped. Some pennate diatoms possess a raphe, which allows them to be motile.

Pennate diatom
Description
Shape Boat-shaped
Size Length 32 - 130 μm, width 7 - 21 μm
Colour Yellow-brown
Connection None
Covering Silica Close

Frustule

In diatoms, the hard and porous silica cell wall (Horner 2002).

frustule
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Flagellum

(plural: flagella) A tail-like projection that sticks out from the cell body and enables movement.

Flagella		 None
Close

Chloroplast

An organelle in the cell that contains the cell pigments (Horner 2002). This is where photosynthesis occurs. A chloroplast is a specialized chromatophore.

Chloroplast		 Two, one on either side of central Close

Raphe

"In some pennate diatoms, one or two longitudinal slits along the [long] axis or around the valve margins" (Horner 2002). Secretion of mucilage allows a pennate diatom to attach itself to or glide on a substrate (Regents of the University of California 2006).

raphe
Behaviour
Lifestyle Close

Photosynthesis

The chemical process by which light energy, water and carbon dioxide are combined to produce oxygen and organic compounds. Photoautotrophic organisms (plants and algae) use this reaction to produce their own food.

Photosynthetic. Sexual/asexual
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Bloom

A rapid increase or accumulation of algal populations in an aquatic system. This will likely involve one or a few dominant phytoplankton species. This follows seasonal patterns (i.e., spring, summer or fall bloom) with dominant species being those that are best adapted to the environmental conditions of that time period. Discolouration of the water may be observed because of the algae's pigmentation. Blooms are often green but may be yellow-brown or red depending on the species present.

Bloom		 Does not usually form blooms
Harmful effects None known
Distribution
Habitat Close

Benthic

The ecological zone at the bottom of a body of water.

Benthic, sometimes found in Close

Plankton

Organisms that drift at the mercy of the currents.

plankton
Geographic Close

Cosmopolitan

Widely distributed; occurring in many parts in the world.

Cosmopolitan
Seasonal Present throughout the year, but more abundant in spring and fall
Growth Conditions
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Salinity

The dissolved ion content of a body of water. Can be measured in the following units: parts per thousand (PPT or ‰), practical salinity units (PSU), and absolute salinity (g/kg). PPT is measured by weight, denoting the number of parts salt per thousand total parts or a value of 10-3. PSU measures the conductivity of saltwater and compares it in a ratio to a standard KCl solution (because this is a ratio, salinity measured in this way can also be written without units). The newest unit of salinity is absolute salinity, which uses the mass fraction of salt in seawater (g salt per kg seawater) rather than its conductivity (TEOS-20 2010).

Salinity		 16 - 39
Temperature -2 - 29 °C

Classification

Empire Eukaryota
Kingdom Chromista
Subkingdom Harosa
Infrakingdom Heterokonta
Phylum Ochrophyta
Subphylum Khakista
Class Bacillariophyceae
Subclass Bacillariophycidae
Order Naviculales
Family Naviculaceae
Genus Navicula Bory de Saint-Vincent 1822

(Guiry and Guiry 2012)

Lifestyle

Photosynthetic. Reproduces sexually and asexually.

Description

Cells are boat-shaped, motile, and solitary. Cells are rectangular in Close

Girdle

In diatoms, the portion of the cell wall between the two valves of a cell; made up of intercalary bands (bands closest to the valves) and connecting bands (bands in the middle of the girdle). In dinoflagellates, the equivalent of a cingulum or transverse furrow (Horner 2002).

girdle view, and widely Close

Lanceolate

Lance-shaped. Having a wider rounded base and tapering towards the tip.

lanceolate in Close

Valve

In diatoms, the structurally distinct halves of the cell wall (Becker 1996).

valve view. Both valves have a central longitudinal raphe with a nodule (bump) in the middle. Valve surface is covered in transverse striations that are crossed by finer longitudinal striations (Hasle and Syvertsen 1997). Two chloroplasts are present, one on each side of the raphe (Cupp 1943).

Measurements

Length Close

Apical

(axis, spine) The region of the apex or point. Refers to the most anterior point or region of the cell (HPP 2003).

(apical axis): 32 - 130 μm
Width Close

Transapical axis

In diatoms, the longitudinal axis of the valve.

(transapical axis): 7 - 21 μm
Transverse Close

Striae

(referring to pores in diatoms) In diatoms, a striation or row of pores on the valve face. "In centric diatoms, striae may be radial, running from the centre of the valve to the margin ... In pennate diatoms, striae may be parallel to the median line of the valve or raphe" (Horner 2002).

striae: 5 - 16 in 10 μm
Longitudinal striae: 24 - 33 in 10 μm
(Hasle and Syvertsen 1997)

Similar species

Pleurosigma and Gyrosigma species, which are slightly Close

Sigmoid

S-shaped.

sigmoidal in valve view, whereas Navicula species are straight.

Harmful effects

None known.

Habitat

Benthic, sometimes found in plankton (Hasle and Syvertsen 1997).

Distribution

Cosmopolitan. Present throughout the year, with higher abundances in spring and fall.

Environmental Ranges

Depth range (m): 0 - 2210
Temperature range (°C): -2.045 - 29.468
Nitrate (μmol L-1): 0.053 - 33.849
Salinity: 16.391 - 38.873
Oxygen (mL L-1): 1.154 - 9.116
Phosphate (μmol L-1): 0.046 - 2.354
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Silicic acid

A general term to describe chemical compounds containing silicon, oxygen and hydrogen with a general formula of [SiOx(OH)4-2x]n. Diatoms polymerize silicic acid into biogenic silica to form their frustules (Azam and Chisholm 1976).

Silicate (μmol L-1): 0.754 - 107.078
(OBIS 2012, cited in EOL 2012)

Bloom characteristics

Does not usually form blooms.

References

Cupp, E. E. 1943. Marine Plankton Diatoms of the West Coast of North America. University of California Press. Berkeley, California. 238.

Encyclopedia of Life (EOL). 2012. Navicula. http://eol.org/pages/76973/overview. Accessed 06 Apr 2012.

Guiry, M. D. and Guiry, G. M. 2012. Navicula Bory de Saint-Vincent, 1822: 128. http://www.algaebase.org/search/genus/detail/?genus_id=43698. Accessed 06 Apr 2012.

Hasle, G. R. and Syvertsen, E. E. 1997. Marine diatoms. In: Tomas, C. R. (ed.) Identifying Marine Phytoplankton. Academic Press, Inc., San Diego. 5-385.

Ocean Biogeographic Information System (OBIS). 2012. Navicula. http://www.iobis.org/mapper/?taxon_id=475889. Accessed 06 Apr 2012.