• Category
  • Length Range
    43.5-133.9 µm
  • Width Range
    2.6-3.9 at the central area, 2.0-3.0 at the poles µm
  • Striae in 10 µm
  • Reported As
    Fragilaria vaucheriae ((Kützing) Petersen [Podzorski 1985, p. 20, fig. 1: 13, 30: 1-3])



Valves are linear and lanceolate with capitate to subcapitate apices. The central area has a slightly expanded margin on one side and is faintly hyaline. The hyaline central area is generally unilateral but may be symmetric or indistinguishable. In specimens with a unilateral central area, the striae are reduced in length on the opposite margin. Such striae range in density from 10 – 18 in 10 µm. In most specimens, striae on the remainder of the valve are finely punctate and parallel. Striae may be uniformly distributed along the valve, erratic, or denser near the poles. Costae are generally thicker than the striae. Fine, circular areolae are only resolvable under SEM. The axial area is very narrow to absent. Valves may be slightly heteropolar at the apices, which range in breadth from 2 – 3 µm. Each pole has a rimoportula, distinguishable under LM. Under SEM, the apical pore field is evident on the mantle and is of the ocellulimbus type. Mantle height ranges from 1.7 – 3.2 µm.


Fragilaria synegrotesca is well documented in shallow water, karstic, oligotrophic wetlands of the Florida Everglades and Caribbean. It is abundant in benthic and epiphytic calcareous periphyton communities and is typical of low phosphorus (P), long hydroperiod, and slightly high conductivity. In the freshwater interior of the Everglades the optimum total periphyton biovolume for F. synegrotesca presence is 900 mL/m with a tolerance from 0 (in benthic, flocculent detritus) – 2900 mL/m (Lee et al. 2013). In the Everglades, F. synegrotesca comprises 11.2 – 18% of diatom abundance in periphyton and is among the five most common diatom species encountered in transects across the Water Conservation Areas, Shark River Slough, and Taylor Slough (Gaiser et al. 2006, La Hée and Gaiser 2012, Lee et al. 2013), with a maximum abundance of 72.54% (Lee et al. 2013) and presence in 149 of 197 samples (Gaiser et al. 2006). In Caribbean wetlands, the relative abundances of F. synegrotesca in periphyton are 14% (New River Lagoon in Orange Walk, Belize), 6% (Sian Ka’an Biosphere Reserve in Quintana Roo, Mexico), and 6.6% (Black River Morass, St. Elizabeth, Jamaica).

In P-limited Caribbean wetlands, F. synegrotesca total phosphorus (TP) optimum is 266 µg P/g with a tolerance range of 145 – 488 µg P/g (La Hée and Gaiser 2012). In the Everglades, F. synegrotesca TP optima have been recorded as 270 ± 202 µg P/g (Gaiser et al. 2006) and 168 µg P/g with a tolerance range of 80 – 355 (La Hée and Gaiser 2012).

Fragilaria synegrotesca is characteristic of and abundant in periphyton communities of freshwater marshes with little drying, with a hydroperiod optimum of 258 ± 48 days inundated (Lee et al. 2013). Drying and subsequent rewetting of the periphyton mat decreases F. synegrotesca relative abundances from up to 18 ±11% to 6 ± 5% (Gottlieb et al. 2005), making this species a potentially “reliable indicator of the absence of periodic drying” in hydrologically controlled habitats like the Everglades (Gaiser et al. 2011).

Fragilaria synegrotesca is characteristic of low nutrient and low conductivity freshwater periphyton, but it has also been found in the oligohaline region of the Everglades. It has a salinity optimum and tolerance of 5 ±7.3 ppt – slightly higher than other freshwater Everglades taxa such as Encyonema evergladianum, Mastogloia calcarea and Brachysira neoexilis (Wachnicka 2010).

There are confirmed distribution records (by Gaiser and colleagues) of F. synegrotesca in freshwater and oligohaline regions of the Everglades and in three regions in the northern Caribbean Basin: the New River Lagoon in Orange Walk, Belize; the Sian Ka’an Biosphere Reserve in Quintana Roo, Mexico; and the Broad River in the Black River Morass, St. Elizabeth, Jamaica.

Epi Periphyton
Credit: Nick Schulte
Epiphytic and epilithic calcareous periphyton in the Florida Everglades.
Xs Periphyton
Credit: Nick Schulte
Cross section of calcareous periphyton (3.6 cm diameter core) from the Florida Everglades.
F Synegrotesca Live
Credit: Nick Schulte
Girdle view of solitary (degraded cell) F. synegrotesca from epiphytic periphyton in a pond in Everglades National Park (25.394516, -80.583271). Scale bar = 10 µm
Ns  Mmd 9 2014  F Synegrotesca Live  Gv 1
Credit: Nick Schulte
Girdle view showing plate-like chloroplasts and oil droplets of solitary F. synegrotesca from benthic oligohaline periphyton in Everglades National Park (25.244478, -80.803351)

Original Description

Fragilaria synegrotesca Lange-Bertalot nov. spec. (Fig. 12:1-11; Fig. 13:1-6)

Synonym: Fragilaria vaucheriae (Kützing) Petersen sensu Pozorski 1985, p. 20, fig. 1: 13 und 30 1-3

Valvae lineares ad valde anguste lineari-lanceolatae, plerumque de medio usque ad fines paulatim attenatae apicibus capitellato-rotundatis, 30 - 170 µm longae, 2.5 - 4 µm latae. Area axialis angustissima, area centralis unilateraliter amplificata. Striae transapicales tenuissime punctatae apparentes, 11 - 14/10 µm quaeque una unam opposite neque alternantes. Rimoportulae non singulae sed binae pro valve. Valvocopula et copulae apertae unilateraliter. Spinae marginales absunt, ocellullimbus depressus in polos adest.

Holotypus: Praep. Am-N 66 in Coll. Lange-Bertalot, Botan. Institut Univerität Frankfurt a.M. Fundort des Holotypus: Florida/USA, Everglades, zwischen Paurotis und Nine Mile pond, leg. Ute Runrich. 3. 10. 1991

  • Author
    Lange-Bert. 1993
  • Length Range
    30-170 µm
  • Width
    2.5-4 µm
  • Striae in 10µm

Original Images

Fragilaria syngrotesca orig illus 2
Fragilaria synegrotesca orig illus 4
F Synegrotesca Orig Des Abridged
Original text and images reproduced with permission by Gebrüder Borntraeger Verlag.

Citations & Links


  • Index Nominum Algarum
  • CAS
  • North American Diatom Ecological Database
    NADED ID: 34143

Cite This Page

Schulte, N. (2014). Fragilaria synegrotesca. In Diatoms of North America. Retrieved July 21, 2018, from https://diatoms.org/species/fragilaria_synegrotesca


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Fragilaria synegrotesca from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.