Bryophyte and pteridophyte spores and other palynomorphs in quaternary marine sediments from Campos Basin , southeastern Brazil : Core BU-91-GL-051

This paper presents morphological descriptions and ecological data of cryptogam spores and other non-pollen palynomorphs from Quaternary sediments of Campos Basin, Rio de Janeiro, SE Brazil. The ages were derived from biostratigraphy of planktonic foraminifers and two radiocarbon dates, and suggest that sediment deposition started in the last 140,000 years BP. Thirty different types of palynomorphs were identified, described, and photographed: two bryophyte spores (sensu lato); 21 pteridophyte spores; four freshwater microalgae; onePseudoschizaea; and two microfungi. Some of the identified spores (Sphagnum, Blechnum, Cyatheaceae, Dennstaedtiaceae, Lycopodiella, Microgramma, Polypodium, Acrostichum, Pityrogramma, and Lygodium) are related to the modern flora found on the northern coast of Rio de Janeiro State, at the Restinga of Jurubatiba, from vegetation types such as shrub swamp/ coastal swamp formation, seasonally flooded forest, Clusia and Ericaceae woods, and disturbed vegetation. The freshwater microalgae and the microfungi are also presently recorded from the coastal lagoons of this region. The high spore concentration in slope sediments reflects the intense terrigenous influx, caused by a relative low sealevel during glacial stages. Palynological analysis suggests the presence of taxa from flooded forests and humid areas in the coastal plain during glacial and interglacial stages of the Late Pleistocene.


Introduction
As pollen and spore morphotypes are very similar to those produced by modern living plants, allowing precise taxonomic identifications at family and genera levels, and as they can indicate ecological processes that took place over timescales on the order of millennia, they are widely used in paleoenvironmental reconstructions on both local and regional geographical scales, together with other types of palynomorphs (Salgado-Labouriau 1994).
The deposition of spores and pollen grains in quaternary marine sediments of Campos Basin is mainly a function of riverine transport, which is strongly influenced by changes in the relative sea level during glacial-interglacial cycles during Pleistocene (Behling et al. 2002).These authors reported high percentage values of spores from tree ferns (e.g.Cyathea and Dicksonia), probably transported by the Paraíba do Sul river.
The evolution of the southeastern Brazilian coast was strongly affected by relative sea level changes that took place during Late Pleistocene, as the coastal plain was formed during two different stages of high sea level: in the previous interglacial (approximately 123,000 years BP) and most recently (7000-5100 years BP) in the current interglacial (Martin et al. 1996).In the last glacial maximum (LGM), approximately 20,000 -18,000 years BP, the relative sea level was 120 meters below the modern level (Viana et al. 1998) and rose rapidly until 7000-5000 years BP (Viana & Faugères 1998).During low sea level stages, the rivers cut through the continental shelf and may have reached the upper continental slope, where paleochannels may be found today.The organic matter originated on the continent was probably transported through these channels and deposited straight onto the continental slope (Viana et al. 1998).Vicalvi (1997) built a biochronostratigraphic framework for Campos Basin on the basis of planktonic foraminifers, following Ericsson & Wöllin (1968).As the BU-91-GL-05 core belongs to this framework, its chronology mainly derives from its biostratigraphy, which allows dating of sediment layers older than radiocarbon's oldest limit.
Two main groups of vascular plants compose the pteridophytes (ferns, horsetails, club mosses, and others): lycophytes and monilophytes (Juddet al. 2002).Smith et al. (2006) proposed a division of monilophytes into four classes: Psilotopsida, Equisetopsida, Marattiopsida,and Polypodiopsida.The largest concentration of pteridophyte species is found in the Mata Atlântica biome (834 species), followed by the Amazon region (428 species) and the Cerrado (245 species), with the highest species diversity found in the southeast and south Brazilian regions (Prado & Sylvestre 2010).
This study presents morphological descriptions of bryophyte (sensu lato) and pteridophyte spores, freshwater algae, and microfungi found in Quaternary sediments from Campos Basin, which is located to the northeast off the Rio de Janeiro coast.Throughout the analyzed core (Fig. 1) the relationship between the identified spores (fossil) and the modern flora of pteridophytes found in the vegetation formations on the continent is clear (Freitas 2005;Freitas et al. 2013).Therefore, these results along with the pollen data constitute an inventory of the Quaternary flora of SE Brazil, and may be a useful tool for other paleoclimate and paleoenvironmental reconstructions conducted in the SE region of Brazil.

Hydrodynamics and depositional aspects of palynomorphs
Hydrodynamical and meteorological aspects (Tyson 1995) control pollen and spore dispersal.Allochthonous palynomorphs are transported to the water after being released from the originating plant.At this dispersal stage, palynomorphs can spread out over large areas, and may be found very far from the source.The general rule of thumb is that the further the distance from the source plant, fewer palynomorphs are to be found in the sediments, and the opposite is also true, as most of the pollen and spores produced fall close to the plant that produced them.The floating time of palynomorphs on water mainly depends on the specific gravity of each palynomorph, palynomorph shape, and protoplasm decay rates.As palynomorph size is similar to that of silt and clay particles, when river transported, palynomorphs can overcome the barrier of waves and be deposited near the edge of the continental shelf and slope (Tyson 1995).On the continental slope thick layers of sediment can be carried to abyssal depths, mainly by turbidity currents through sub- marine canions.The deposition patterns of palynomorphs in marine sediments are mainly a function of drainage basin characteristics, such as basin dimensons, and river discharge, among others (Mudie 1982), and as you go further offshore, the abundance of palynomorphs markedly decreases.In large river systems, such as the Amazon, Mississippi, Nile, and Orinoco rivers, the transport is much more efficient, and sediments and palynomorphs accumulate further from shore and faster than in other regions.Gregory & Hart (1992) promote the use of the pollen grain/spore ratio to infer relative sea level, because at low sea level, there is an increase of spore abundance, whereas pollen grains accumulate increasingly during conditions of high sea levels.

Study area
Campos Basin is located on the southeastern coast of Brazil, 21°-23°S, between Vitória High and Cabo Frio High (Fig. 1).The coastal plain of northern Rio de Janeiro is wide (21°30'-22°15'S), and because it includes the Paraiba do Sul River estuary, it is affected by both the river and the sea (Radambrasil 1983).As the Paraiba do Sul River is 1145 km long, and its drainage basin is 55,400 km 2 (Molisani et al. 1999), including the mountain ridges of Serra do Mar and Serra da Mantiqueira (Behling et al. 2002), it constitutes a major terrigenous input of sediments (including continental palynomorphs) to the continental slope.
Climate is warm (23°C) and humid, with wet summers and dry winters.The mean annual precipitation varies between 650 and 1000 mm, and the dry season lasts 3-4 months (Nimer 1979).
The modern vegetation of the region is a mosaic of rain forest (Floresta Ombrófila Densa), seasonally dry forest (Floresta Estacional Semidecidual), coastal woodland and mangroves (pioneer formations), and cultivated areas (Radambrasil 1983).Phytosociological studies conducted in the region (Assumpção & Nascimento 2000;Silva & Nascimento 2001;Moreno et al. 2003;Pimentel et al. 2007) identified deciduous forests on top of Tertiary coastal plateaus, and a xerophytic type of vegetation (restinga) near the shore.The restinga vegetation is strongly influenced by the sea, and presents several grades of physiognomy (i.e., from herbaceous to shrubby woodlands).Along the entire coast, mangroves are also easily found (IBGE 1992) (Fig. 1).In addition, the Jurubatiba Coastal Woodlands National Park, a very important conservation area located in this region, harbors many restinga ecosystems (Costa & Dias 2001;Pereira et al. 2004;Montezuma & Araujo 2007).
The marine currents carry sediments, including organic matter and palynomorphs, over the continental shelf (where submarine canyons are abundant) from the continent to the continental slope.Estimated sedimentation rates are higher for the Pleistocene (40-140cm/1000 years) than during the Holocene (12.7cm/1000 years) (Vicalvi 1997).The amount of airborne palynomorphs deposited in these marine sediments is supposedly negligible because the prevailing wind direction is from the sea to the land (Nimer 1979), although dry winds occasionally blow from the west and northwest (Ybert 1980).
Forty-three samples (10-20g of sediment each) were used for palynological analysis.The chemical attack avoided organic matter oxidation and followed Tyson (1995) andMendonça Filho et al. (2002), using hydrochloric and fluoric acids to dissolve carbonates and silicates, and heavy liquid separation with zinc chloride (D=2.0) to concentrate the organic residue.The palynological slides are stored at the Laboratório de Paleoecologia Vegetal, in the Departamento de Geologia e Paleontologia of Museu Nacional, Universidade Federal do Rio de Janeiro.For each sample, were counted between 200-300 palynomorphs, with the exception of just a few samples where concentration was to low (0.3 m, 1.3 m, 64.62 m, 70.45 m, 86.17 m, 99.75 m e 128.5 m), which coincided with sand layers in the core (Freitas 2005).

Final remarks
The taxonomy data and morphological descriptions allowed the identification of 30 different palynomorphs, including bryophyte (sensu lato) and pterydophyte spores, freshwater microalgi, and fungal spores.The ecological informations provided by these palynomorphs help to reveal paleoenvironmental conditions, from the coastal plains, coastal tablelands, and hills near Campos Basin.The spores from plants could be associated to the vegetation types found today in the continent, such as ombrophilous (Atlantic Rainforest), semi-deciduous forest, herbaceous and forest-swampy coastal vegetation.The freshwater microalgi and the microfungi confirm the influence of periodic and permanent flooded environments, swamp forests and aquatic environments.The plant spores found in these sediments from the continental slope suggest the high input of terrigenous during the last glacial stadial, coincident with the low sea level during the Late Pleistocene (Last Glacial Maximum).
Comments: resambles Danaea spp.Ecological Data: recorded as herbaceous living within

Table 2 .
(Pereira et al. 2007)001)nt spores registered in this work and the present-day taxa occurrence in plant communities at "Jurubatiba Coastal Woodlands National Park" (Rio de Janeiro State).References:Santos & Sylvestre (2001)andSantos et al. (2004).Zona da Mata (Coastal Atlantic Forest) in Pernambuco State(Pereira et al. 2007).Occurrence: at Atlantic Rain Forest of southern Espírito Santo State (Aquije & Santos 2007) and at the Ecological Reserve of Gurjaú, Cabo de Santo Agostinho County (Pernambuco State, NE Brazil), where it is considered to be a rare species (D. bipinnata) with a new record in Pernambuco State.Asplenium, Blechnum, Microgramma, Polypodium and Vittaria) (Schmitt & Windisch 2005).Occurrence: recorded in the hills with Atlantic Rain Forest of southern Espírito Santo State and SE Brazil (Aquije & Santos 2007).