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Spiniferites ramosus var. ramosus

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

 
dorsal view
single grain - reference collection Bremen
sample: GeoB xxxxx
eastern equatorial Atlantic,off NW Africa
photgraphs: Karin Zonneveld
 

Field characteristics

Spiniferites ramosus var. ramosus (Ehrenberg 1838) Mantell 1854

Field characteristics:
Proximochorate ovoidal to spherical cysts with smooth outer wall. Tabulation is expressed by low sutural septa,. Processes are hollow and exclusively gonal, distally furcate with bifurcate tips.

Dimensions: Cyst body: 17 to 43 (width) x 30 to 46 (length) µm; length of processes: 1.2 to 12 µm (after Lewis et al., 1999).
Motile affinity: Probably a cyst of Gonyaulax spp. (Lewis et al., 1999).
Stratigraphic range: Cretaceous to Recent.

Comparison with other species:
This species differs from all other Spiniferites by its relatively long processes compared to its cyst body (length at least 2/3 th....but this is an arbitrary decision as it is not included into the species description). It may appear like a N. labyrinthus without the distal connection of its processes. Sometimes one or very few processes can be distally connected by ribbon-like trabeculae. In culture specimens with low process lengths are known.

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
Spiniferites ramosus is a cosmopolitan species with a sub-polar to equatorial distribution. Although it can reach high relative abundances in high productivity areas such as upwelling regions and areas influenced by river discharge, it is not restricted to these regions and occurs in the oligotrophic parts of the open oceans as well.
Distribution:
Spiniferites ramosus is observed from sub-polar to equatorial regions with the polar fronts forming roughly the margins of its distribution in both hemispheres. Highest abundances (up to 96%) occur near the coast in the Gulf of Alaska (northeastern Pacific), the Yellow Sea and Sea of Japan (northwestern Pacific), the Tasman Sea (southwestern Pacific) the equatorial eastern Indian Ocean, the Arabian Sea and the upwelling regions off NW and SW Africa. Although it is observed in river plume areas, it is not more abundant in these regions.

Environmental parameter range:
SST: 0 - 29.8°C (winter - spring) except for two North Atlantic/Arctic sites off Greenland where SST drop to -2.0°C. SSS: 17.5 - 39.4 (summer - autumn), P]: 0.06 - 1.73 μmol/l, [N]: 0.04 - 24.0 μmol/l, chlorophyll-a: 0.06 - 20.9 ml/l, bottom water [O2]: between 0.01 - 8.0 ml/l.
Spiniferites ramosus is observed in regions where the upper water salinity conditions can be reduced permanently or seasonally by river discharge or melting of snow/ice. Although Spiniferites ramosus can be observed in oligotrophic regions, highest abundances occur where the environment is seasonally mesotrophic to eutrophic such as in upwelling areas.

Comparison with other records:
Apart from the records in the dataset of this Atlas, Spiniferites ramosus has been observed in surface sediments of coastal sites of the Persian Gulf, off western India (Arabian Sea), the upwelling area off Peru (eastern Pacific) and the coastal area off Svalbard (Bradford, 1975; Godhe et al., 2000; Biebow et al., 1993; Grøsfjeld et al., 2009).
Seasonal distribution and sediment trap studies in general, report only very few cysts of Spiniferites ramosus hampering the determination of a seasonal production pattern (e.g. Pospelova et al., 2010). In the Arabian Sea cysts with cell content were registered during active upwelling whereas empty cysts are were recorded throughout the year (Zonneveld and Brummer, 2000). Although no clear seasonal production pattern has been observed in the upwelling area off Portugal, low numbers of cysts were documented in the sediments during upwelling initiation and termination phases (Ribeiro; Amorim, 2008). In the North Atlantic, low numbers of Spiniferites ramosus cysts are observed exclusively in trap samples from the North Atlantic Current region (Dale and Dale, 1992)
In Arctic sediments the relative abundance of this species is negatively correlated to the seasonal ice cover duration (Radi and de Vernal, 2008). It has, with one exception, not been observed in areas where ice cover lasts > 8 months a year (de Vernal et al., 1998).