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Fragilaria synegrotesca

Lange-Bert. 1993      Category: Araphid

REPORTED AS: Fragilaria vaucheriae ((Kützing) Petersen [Podzorski 1985, p. 20, fig. 1: 13, 30: 1-3]) 

Fragilaria socia


Fragilaria tenera

LM scalebar = 10 µm = 40 pixels.


Contributor: Nick Schulte - June 2014
Length Range: 44-134 µm
Width Range: 2.6-3.9 at the central area, 2.0-3.0 at the poles µm
Striae in 10 µm: 10-18


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.

Original Description

Author: Lange-Bert. 1993
Length Range: 30-170 µm
Width Range: 2.5-4 µm
Striae in 10 µm: 11-14

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

Original Images

Original text and images reproduced with permission by Gebrüder Borntraeger Verlag.

Cite This Page:
Schulte, N. (2014). Fragilaria synegrotesca. In Diatoms of the United States. Retrieved May 21, 2018, from

Species: Fragilaria synegrotesca

Contributor: Nick Schulte

Reviewer: Eduardo A. Morales


Gaiser, E.E., Childers, D.L., Jones, R.D., Richards, J.H., Scinto, L.J., and Trexler, J.C. (2006). Periphyton responses to eutrophication in the Florida Everglades: Cross–system patterns of structural and compositional change. Limnology and Oceanography 51: 617–630.

Gaiser, E., McCormick, P., Hagerthey, S., and Gottlieb, A. (2011). Landscape patterns of periphyton in the Florida Everglades. Critical Reviews in Environmental Science and Technology 41 (S1): 92-120. doi:10.1080/10643389.2010.531192

Gottlieb, A., Richards, J., and Gaiser, E. (2005). Effects of desiccation duration on the community structure and nutrient retention of short and long-hydroperiod Everglades periphyton mats. Aquatic Botany 82 (2): 99-112. doi:10.1016/j.aquabot.2005.02.012

Lange-Bertalot, H. (1993). 85 Neue taxa und uber 100 weitere neu definierte Taxa erganzend zur Subwasserflora von Mittleuropa. Bibliotheca Diatomologica 27, 454 p. Cramer, Berlin, Stuttgart.

La Hée, J.M. and Gaiser, E.E. (2012). Benthic diatom assemblages as indicators of water quality in the Everglades and three tropical karstic wetlands. Freshwater Science 31: 205–221. 10.1899/11-022.1

Lee, S., Gaiser, E., and Trexler, J. (2013). Diatom-Based Models for Inferring Hydrology and Periphyton Abundance in a Subtropical Karstic Wetland: Implications for Ecosystem-Scale Bioassessment. Wetlands 33 (1): 157-173. doi:10.1007/s13157-012-0363-z

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Fragilaria synegrotesca CAS

North American Diatom Ecological Database (NADED)

NADED ID: 34143

Autecology Discussion

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.


Epiphytic and epilithic calcareous periphyton in the Florida Everglades.

Credit/Source: Nick Schulte

Cross section of calcareous periphyton (3.6 cm diameter core) from the Florida Everglades.

Credit/Source: 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

Credit/Source: 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)

Credit/Source: Nick Schulte