High Marsh Foraminiferal Assemblages' Response to Intra-Decadal and Multi-Decadal Precipitation Variability, Between 1934 and 2010 (Minho, NW Portugal)
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Journal of Sea Research 93 (2014) 118–132 Contents lists available at ScienceDirect Journal of Sea Research journal homepage: www.elsevier.com/locate/seares High marsh foraminiferal assemblages' response to intra-decadal and multi-decadal precipitation variability, between 1934 and 2010 (Minho, NW Portugal) Francisco Fatela a,b,⁎, João Moreno a,b, Eduardo Leorri a,c, Reide Corbett c a Universidade de Lisboa, Centro de Geologia_CeGUL, Campo Grande, 1749-016 Lisboa, Portugal b Universidade de Lisboa, Faculdade de Ciências, Departamento de Geologia, Campo Grande, 1749-016 Lisboa, Portugal c East Carolina University, Department of Geological Sciences, Greenville, NC 27858-4353, USA article info abstract Article history: Foraminiferal assemblages of Caminha tidal marshes have been studied since 2002 revealing a peculiar domi- Received 22 March 2013 nance of brackish species, such as Haplophragmoides manilaensis, Haplophragmoides wilberti, Haplophragmoides Received in revised form 3 July 2013 sp., Pseudothurammina limnetis and Trochamminita salsa/irregularis in the high marshes of the Minho and the Accepted 31 July 2013 Coura lower estuaries. The assemblage composition reflects low salinity conditions, despite the short distance Available online 14 August 2013 to the estuarine mouth (~4 km). However, in May 2010, the presence of salt marsh species Trochammina inflata and Jadammina macrescens became very significant, likely a result of 5 consecutive dry years and a corresponding Keywords: Modern foraminifera salinity rise in sediment pore water. Correspondence analysis (CA) groups the surface samples according to their High-marsh marsh zone, showing a positive correlation with the submersion time of each sampling point. The brackish and Multi-decadal precipitation normal salinity foraminiferal species appear separated in the CA. This observation was applied to the top SW Europe 10 cm of a high marsh sediment core that corresponds to the period of instrumental record of precipitation and river flow in the Minho region. We found that river flow strongly correlates with precipitation in the Lima and Minho basins. The longer precipitation record was, therefore, used to interpret the foraminiferal assem- blages' variability. Three main phases were distinguished along ca. 80 years of precipitation data: 1) nega- tive anomalies from 1934 to 1957; 2) positive anomalies from 1958 to 1983; and 3) negative anomalies from 1984 to 2010. This last dryer period exhibits the precipitation maximum and the greatest amplitude of rainfall values. High marsh foraminifera reveals a fast response to these short-term shifts; low salinity species relative abundance increases when precipitation increases over several decades, as well as in the same decade, in the years of heavy rainfall of dryer periods. High marsh foraminifera records the increase of freshwater flooding and seepage by 1) decreasing abundance and 2) increasing the dominance of low salinity species. On the other hand, low precipitation over ca. 5 years increases the assemblage productivity and the relative abundance of normal salinity species. The positive correlation found between winter precipitation and the NAO winter index indicates that the Minho region is a part of the North Atlantic climate dynamics and demonstrates that the foraminiferal record from Caminha high marsh may be applied in high-resolution studies of SW Europe climate evolution. © 2013 Elsevier B.V. All rights reserved. 1. Introduction The study of benthic foraminiferal assemblages from tidal-marsh ecosystems undertaken in the last several decades clearly highlights their value as environmental proxies (e.g. Gehrels et al., 2001; Hayward et al., 1999; Martin, 2000; Martin et al., 2002; Murray, 1991, ⁎ Corresponding author at: Universidade de Lisboa, Faculdade de Ciências, Centro de 2006; Phleger and Bradshaw, 1966; Phleger and Walton, 1950; Pujos, Geologia, Ed. C6, Campo Grande, 1749-016 Lisboa, Portugal. Tel.: +351 21 750 03 58; 1971, 1976; Scott et al., 2001; Sen Gupta, 2002). The development of fax: +351 21 750 00 64. E-mail addresses: [email protected] (F. Fatela), [email protected] (J. Moreno), marsh foraminiferal studies has provided insights into palaeoecological [email protected] (E. Leorri), [email protected] (R. Corbett). information, mainly concerned with climate dynamics, sea-level rise, 1385-1101/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.seares.2013.07.021 F. Fatela et al. / Journal of Sea Research 93 (2014) 118–132 119 and the evolution of coastal zones under natural or anthropogenic influ- interpretations (e.g. Callard et al., 2011; Fatela et al., 2009; Leorri and ence (e.g. Alve, 1995; Armynot du Châtelet et al., 2004; Callard et al., Cearreta, 2009; Leorri et al., 2008, 2010a, 2011). 2011; Cearreta et al., 2008; Fatela et al., 2007; Gehrels, 1994, 2000; The distribution of foraminiferal assemblages across a tidal marsh Hippensteel et al., 2002; Horton and Edwards, 2006; Horton et al., is linked to the tidal flooding (a direct constraint of ecological factors 1999; Kemp et al., 2011; Leorri et al., 2010a, 2011; Moreno et al., such as salinity and desiccation) that, in turn, correlates well with 2005; Scott and Medioli, 1980). This micropalaeontological information, elevation. Foraminiferal assemblages gradually reduce the number when sufficiently preserved in the sedimentary record, tied to high pre- of species from tidal flat (submersion time N50%) to high marsh cision instrumental data and analyzed with robust statistical analy- (submersion time b6%) where Trochammina inflata (Montagu, 1808) sis, can provide reliable palaeoenvironmental reconstructions (e.g. and Jadammina macrescens (Brady, 1870) are usually dominant Callard et al., 2011; Cearreta et al., 2002b, 2007, 2008; Diz et al., (e.g. Phleger and Bradshaw, 1966; Scott and Medioli, 1980; Sen Gupta, 2002; Gehrels, 1994; Gehrels et al., 2001; Hippensteel et al., 2002; 2002) in the lower reaches of the estuaries (i.e. greater marine Horton and Edwards, 2000, 2006; Kemp et al., 2009; Leorri et al., influence). This is not the case in the Minho and the Coura estuaries 2010b, 2011; Martin, 2000; Williams, 1994). Climate, geological where high tide covers the marsh with brackish water. The high structures and lithology, and geomorphological conditions of the marsh foraminiferal assemblages are dominated by Haplophragmoides drainage basin and the hydrodynamics of an estuary control the ma- manilaensis (Andersen, 1953), Haplophragmoides sp., Trochamminita rine influence in its lower reaches, imposing a geochemical signature salsa (Cushman and Bronnimann, 1948), Trochamminita irregularis in estuarine waters as well as in the marsh sediments and interstitial (Cushman and Bronnimann, 1948), and Pseudothurammina limnetis waters. The composition and distribution of foraminiferal assem- (Scott and Medioli, 1980)(seeFatela et al., 2007, 2009; Moreno et al., blages reflect these abiotic characteristics of a tidal marsh ecosystem, 2005, 2006). We believe that high marsh represents an extreme as well as their evolution controlled by regional and global changes environment where foraminiferal species, though euryhaline and eury- and responding to anthropogenic impacts of the estuary over time thermic, are at the limit of their environmental tolerance. Consequently, (e.g. Alve, 1995; Armynot du Châtelet et al., 2004; Cearreta et al., a global and regional overview of these proxies must be supported by 2000, 2002a,b; De Rijk, 1995; De Rijk and Troelstra, 1997; Diz et al., regional or local studies. 2002; Fatela et al., 2007, 2009; Hayward et al., 1999; Kemp et al., 2011; Moreno et al., 2005, 2006, 2007). The contribution of tidal- 2. Regional setting marsh foraminiferal assemblages to palaeoenvironmental studies has been recognized worldwide (e.g. Callard et al., 2011; Fatela et al., The Minho River originates at Serra da Meira, in the province of Lugo 2009; Hayward et al., 1999; Horton and Murray, 2007; Kemp et al., (Spain). 2011; Murray, 1971; Phleger and Walton, 1950), but when analyzed After approximately 300 km, the Minho River flows into the NE in detail, regional differences must be accounted for to achieve accurate Atlantic, in the northwest coast of the Iberian Peninsula. It defines the Fig. 1. A — Location of study area in Portugal. B — Minho estuary and Coura tributary. Darker gray area represents the Caminha tidal marsh. 120 F. Fatela et al. / Journal of Sea Research 93 (2014) 118–132 210 -1 137 -1 Pb Excess (Bq kg ) Cs (Bq kg ) The Minho River discharges to the sea through a barred estuary – 0 trending NNE SSW. It presents a semi-diurnal high meso-tidal regime with an astronomical tidal range of 2 m, during neap waters, and almost 1 4 m in spring tides. The high-water astronomic tidal levels are often ac- 2 centuated by storm surges (Taborda and Dias, 1991). The dynamic tide is felt up to 40 km upstream, due to the large tidal range and the 3 smoothness and low gradient of the Minho's outlet (Alves, 1996). The 4 upstream limit of marine water influence has been reported between 9kmand35km,(Bettencourt et al., 2003; Fatela et al., 2009). The 5 lower estuary section just extends a few kilometers from the 6 mouth and essentially behaves as “partially mixed” (Brown et al., 1991). This section is very shallow as a result of widespread siltation 7 and, therefore, a significant part of the bottom emerges during low Deph (cm) 8 water spring tide. A large tidal flat and tidal marsh surface of around 6km2 have developed in the