Cold marine indicators of the late Quaternary: the new dinoflagellate cyst genus Islandinium and related morphotypes

Abstract

Head, M. J., Harland, R. and Matthiessen, J. 2001. Cold marine indicators of the late Quaternary: the new dinoflagellate cyst genus Islandinium and related morphotypes.ABSTRACT: Round, brown, spiny dinoflagellate cysts characterise many modern high-latitude assemblages. Abundance is often highest where summer sea-surface temperatures seldom exceed 7°C and where winter sea-surface temperatures are around 0°C, making this morphological group important for reconstructing cold intervals within marine Quaternary sequences. Our analysis of modern sediments from the Beaufort Sea of Arctic Canada, the Kara and Laptev seas of Arctic Russia, and across the Arctic Ocean, allows us to recognise the new cyst genus Islandinium along with the extant species Islandinium minutum (Harland and Reid in Harland et al., 1980) new combination (basionym: Multispinula? minuta), Islandinium? cezare (de Vernal et al., 1989 ex de Vernal in Rochon et al., 1999 new status and combination (basionym: Multispinula? minuta var. cezare) sensu lato, and Echinidinium karaense new species. Of these, the generotype Islandinium minutum is a well-known but morphologically problematic species. We have re-examined the type material from the Beaufort Sea and studied specimens from across the Arctic, and our observations clarify ambiguities in the original description of this species. The archeopyle of Islandinium minutum results from the loss of three apical plates, an unusual style among peridiniphycidean dinoflagellates. The asymmetrical location of these plates around the apex is distinctive, and probably contributed to earlier misunderstandings of the archeopyle. Previous attributions to Multispinula? and Algidasphaeridium? are unsustainable. Maps showing the distribution of Islandinium minutum are given for the Northern Hemisphere and show this species to be polar to north-temperate, whereas Islandinium? cezare s.l. and Echinidinium karaense appear to be more restricted to polar environments.

Regional seesaw between the North Atlantic and Nordic Seas during the last glacial abrupt climate events

“…S2 for further details on the methodology; Rochon et al, 1999;Head et al, 2001;Telford and Birks, 2005Telford, 2006;de Vernal, 2007, 2011a, b;Birks et al, 2010;Radi et al, 2013;de Vernal et al, 2013a, b;Trachsel and Telford, 2016). As dinoflagellates are mostly restricted to the uppermost 50 m water depth (Sarjeant, 1974), they are assumed to directly reflect sea-surface conditions (see Sect.…”

Spatial distribution of benthic foraminiferal stable isotopes and dinocyst assemblages in surface sediments of the Trondheimsfjord, central Norway

“…An average amount of 300 cysts per slide was counted using a Zeiss axio scope light microscope at 40× magnification. The identification of the cysts is based on the nomenclature of Rochon et al (1999) and Head et al (2001). Operculodinium centrocarpum s.l.…”

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“…Furthermore, heterotrophic dinoflagellate cysts dominate the assemblages in polar areas where sea ice occurs up to 12 months per year (e.g., Rochon et al, 1999). The sea ice-associated species Islandinium minutum, known to be very abundant or dominant in the Arctic Ocean and subarctic regions with pronounced sea ice cover (Head et al, 2001;Hamel et al, 2002), appeared to increase at ~1 Ma at both Sites U1343 and U1344 (Fig. F9).…”

“…is one of the most ubiquitous taxa among protoperidinials, and its distribution in modern sediments is closely related to primary productivity in temperate regions and also to polar and subpolar regions of the North Atlantic and Arctic oceans with seasonal sea ice coverage (Rochon et al, 1999). Islandinium minutum is one of the principal, if not the dominant, component of assemblages in the modern Arctic Ocean (Rochon et al, 1999;Head et al, 2001). The overall abundance of dinocysts and particularly the above-mentioned species suggests high productivity and upwelling during prominent interglacials.…”