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Bitectatodinium spongium

Zonneveld, K.A.F. and Pospelova V. (2015). A determination key for modern dinoflagellate cysts. Palynology 39 (3), 387- 407.

 
lateral view
single grain - reference collection Bremen
Sample: Arze 469 Arabian Sea
photographs: Karin Zonneveld
detail cell wall
lateral view
single grain - reference collection Bremen
Sample: Arze 469, Arabian Sea

Field characteristics

Bitectatodinium spongium (Zonneveld) Zonneveld et Jurkschat 1998

Field characteristics:
Spheroidal cysts with a wall that comprises a thin pedium and a spongy, granulo-fibrous, distally open luxuria of numerous capitate or acuminate solid spines. Archeopyle is chasmic or is formed by the loss of the precingular plates 2" and 3". There are no ornaments reflecting tabulation.

Dimensions: body diameter 62 mm, spine length on average 10.5 mm, wall thickness 3.2 mm. Range: body diameter: 48-63 μm (mean = 55.6 μm, n=22); spine length: 5-11 μm (mean = 8 μm, n= 22); thickness cell-wall: 1.5-3.5 μm (mean = 2.6 μm, n=22).
Motile affinity: unknown
Stratigraphic range: Holocene – Recent

Comparison with other species:
The most striking features of this species are its relatively large size and its spongy wall. The spongy luxuria appears densely fibrous under bright field microscopy. Part of the fibrils project from the surface of the fibrous layer and form acuminate or capitate spines which have lengths of about three times the thickness of the fibrous layer. In some specimens no capitate spines are observed. The thin pedium is only seen by lightmicroscopy in optical section. The texture of the pedium (inner layer of cyst wall) seems to be microgranular under the SEM. The cysts have a yellow appearance. The archeaopyle often consist of a single split, a precingular archeopyle is extremely seldom. The cysts are often folded making it difficult to recognise the archeopyle.

Geographic distribution

Geographic distribution based on :
Zonneveld et al., 2013. Atlas of modern dinoflagellate cyst distribution based on 2405 datapoints. Review of Palaeobotany and Palynology, v. 191, 1-197
Bitectatodinium spongium can be considered to be typical for tropical to subtropical full marine upwelling areas. It is abundant in areas with anoxic and hypoxic bottom waters.
Distribution:
B. spongium is restricted to equatorial and subtropical areas that are generally characterised by the presence of coastal upwelling. It can form up to 62.5% of the association in the eastern Pacific Ocean.

Environmental parameter range:
SST: 10.7 - 29.8°C (summer - summer). SSS: 31.9 - 38.3 (summer - winter), [P]: 0.1 - 1.1 μmol/l, [N]: 0.04 - 8.7 μmol/l, chlorophyll-a: 0.13 - 12.2 ml/l, bottom water [O2]: < 6 ml/l.
Highest abundances (>10%) are observed in regions where SST > 20°C throughout the year. Cysts are reported mainly from upwelling regions where large inter-annual variability in the trophic state of the upper waters can occur with eutrophic conditions during active upwelling, upwelling relaxation or when upwelling filaments cross the sampling site and oligotrophic conditions when upwelling is absent. The species is most abundant in areas where bottom waters are anoxic or hypoxic conditions and is absent from well-ventilated regions.

Comparison with other records:
Apart from the recordings in this Atlas B. spongium has been reported from coastal areas of Vietnam (South China Sea, Mizushima, 2007). Sediment trap studies off NW Africa and in the Indian Ocean reveal that cysts of this species are produced during times of active upwelling with upwelling cells located in the vicinity of the sampling site (Zonneveld and Brummer, 2000; Susek et al., 2005; Zonneveld et al., 2010). In the Arabian Sea the occurrence of upwelling is restricted to the south-east monsoon in June-September, off NW Africa upwelling can occur throughout the year and is not bound to a certain season.