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High abundances of mangrove pollen have been associated with transgressive cycles on tropical margins, but the detailed relations between systems tracts and the taphonomy of the pollen are unclear. We report here the occurrence and high abundance of Rhizophora pollen, in association with taraxerol, a Rhizophora-sourced biomarker, from a high-resolution Congo fan core covering the last deglaciation. An age model based on 14C dates enables the temporal changes in taraxerol content and the percentage frequencies and flux (pollen grains (pg) cm–2 (103 yr)–1) of mangrove pollen to be compared quantitatively with the lateral rate of transgression across the flooding surface (derived from glacio-hydro-isostatic model output and the bathymetry of the margin). Rhizophora pollen concentrations and taraxerol content of the sediment are very strongly positively correlated with the lateral rate of transgression and indicate, independently of any sequence stratigraphic context, that mangrove pollen spikes are associated with the transgressive systems tract rather than the highstand systems tract or maximum flooding surface. Lower-resolution longer-term records from this margin indicate an association between taraxerol concentrations and transgressive rather than regressive phases. The flux of these materials to the Congo fan is interpreted as a function of the erosion of flooded mangrove swamp on the shelf and less importantly, changing extent of mangrove habitat, during sea-level rise. Congo River palaeoflood events also result in reworking of mangrove pollen and supply to the fan, but this mechanism is subdominant. Rhizophora pollen has been underestimated in many palynological studies undertaken on cores from the African margin because of inappropriate sieve mesh size used during laboratory preparation.

Recent studies have correlated dinoflagellate resting cyst morphology to salinity and density variations in the water column, suggesting that morphology can be used for paleoceanographic reconstructions. However, the univariate statistics used by these studies are appropriate only where morphology is related to a single variable. Density is a function of salinity and temperature, so more advanced statistical methods are needed to understand which parameters affect morphology. In this study based on surface (coretop) sediments, a set of environmental variables (sea-surface salinity, temperature, nitrate, and phosphate) was simultaneously correlated to morphological variations seen in resting cysts produced by the dinoflagellate Protoceratium reticulatum (= Operculodinium centrocarpum sensu Wall and Dale). Approximately 3200 measurements were obtained from the North Atlantic Ocean and used to generate a working model based on the Akaike information criterion. Hierarchical partitioning was then applied to establish the independent and joint effects for each predictor variable. Results from these analyses showed that while salinity constitutes the dominant variable affecting process length in the cysts of P . reticulatum in the North Atlantic, it is not the sole explanatory variable and that multicollinearity exists. Temperature and nutrients also showed a significant relationship to the morphology, requiring multiple regression to construct a representative model. The applicability of the North Atlantic working model was finally evaluated by comparing the results to data from the Mediterranean, Marmara, and Black seas, and Baltic–Kattegat–Skagerrak estuarine system. This comparison showed regional differences in morphological–environmental correlation. While salinity constitutes the most important explanatory factor in both the North Atlantic and Baltic–Skagerrak system, this is not so for the Mediterranean–Black Sea region where temperature is the dominant variable. It is concluded that a predictive salinity model based on P . reticulatum cyst morphology has at best a regional application.

Specimens belonging to the mixotrophic genus Fragilidium were isolated from coastal waters of west Iberia (NE Atlantic). Based on plate morphology and large subunit ribosomal DNA (LSU rDNA) sequences two species were identified: F. subglobosum and F. cf. duplocampanaeforme. The life cycle is similar in both species. The asexual cycle is characterized by an alternation between a thecate motile stage and a reproductively active coccoid stage. The sexual cycle is characterized by heterogamous anisogamy and includes a sexual benthic hypnozygote. The first apical plate in vegetative cells does not touch the apical pore plate while in gametes it does, confirming in Fragilidium the homology of what is frequently referred to as the first pre-cingular with the first apical plate in Gonyaulacales. Both species were observed to prey on Ceratium horridum. Molecular phylogenetic analyses with strains isolated from other geographical areas and Fragilidium gene sequences available in GenBank identified three different clades: one comprising F. subglobosum from the type locality and strains from Iberian waters; a second comprising the morphological species F. cf. duplocampanaeforme from Iberia and other strains from NE Atlantic, SE Atlantic and the south Pacific; and a third with an unassigned species from the SE Atlantic.