Foraminiferal biotopes and their distribution control in Ria de Aveiro (Portugal): a multiproxy approach

Abstract

Ria de Aveiro, which is located in the centre of Portugal (40° 38' N, 8° 45' W), is a well-mixed and complex coastal lagoon that is separated from the sea by a sandy barrier and connects with the Atlantic through an artificial inlet. Tidal currents are the main factor controlling the lagoon's hydrodynamics and, to a great extent, the sedimentary dynamic. The inner lagoonal zones receive input from several rivers and experience the pressure caused by the accumulation of organic matter and pollutants (namely, trace metals) from diverse anthropic activities. This paper is the first piece of work aiming to recognize, characterize and explain the main benthic foraminiferal biotopes in Ria de Aveiro. To provide a broad overview of this kind of setting, our results are compared to those of previous published studies conducted in similar transitional environments. The research is based on an investigation of 225 sites spread throughout this ecosystem. Utilizing a statistical approach, this study analyses the details of dead benthic foraminiferal assemblages composed of 260 taxa, the texture and composition (mineralogical and geochemical) of the sediment and physicochemical data. On the basis of the results of R-mode and Q-mode cluster analyses, several different biotopes can be defined as marsh biotope/near-marsh biotope; marginal urban/marginal urban mixing biotope; inner-outer lagoon biotope or enclosed lagoon; outer lagoon biotope, mixed sub-biotope; and outer lagoon, marine sub-biotope. These biotopes are related to foraminifera assemblages and substrate type and are influenced by local currents, water depth, chemical and physicochemical conditions, river or oceanic proximity, and anthropogenic impact, as evidenced by the mapping of the six factor loadings of the principal component analysis conducted herein. Based on a similar methodology of analysis as that applied in previous studies in the Lagoon of Venice, comparable biotypes were identified in Lagoon of Aveiro.

Biocenoses of Benthic Foraminifera of the Aveiro Continental Shelf (Portugal): Influence of the Upwelling Events and Other Shelf Processes

“…In this zone, the presence of a significant number of euryhaline and eurythermic agglutinated species, also can be found alive in Aveiro Lagoon (Martins et al, 2014(Martins et al, b, 2016, such as C. jeffreysii, Lepidodeuterammina eddystonensis, L. ochracea, Remaneica plicata and Remaneicella gonzalezi is in agreement with the possible occurrence of salinity and temperature deviances related to the lagoon outflow. The living foraminiferal assemblage found in this sector seems to include mainly opportunistic species, such as some Bolivinids and C. jeffreysii that should tolerate environmental disturbance but are benefited by the supply of organic matter from the Aveiro Lagoon.…”

“…Therefore, it should be deduced that the biocenoses composition of foraminifera found between 20-80 m were relatively well established and included species common in other regions of the Portuguese Continental Shelf (Mendes et al, 2004;Guerreiro et al, 2009;Martins et al, 2012Martins et al, , 2014.…”

Taxonomy, ecology and biogeographical trends of dominant benthic foraminifera species from an Atlantic-Mediterranean estuary (the Guadiana, southeast Portugal)

“…Mendes et al (2004) previously described B. ordinaria as an important component of the shelf deep-water assemblage, relating it to low hydrodynamic levels, low-oxygen fine-grained sediments and to coldwater incursion derived from upwelling events. This species was also found in significant numbers in benthic foraminiferal assemblages from areas of greater marine influence offshore from the Ria de Aveiro, associated with fine-grained sediments enriched in TOC (Martins et al, 2014). Redois (1997a,1997b), in a survey regarding foraminiferal distribution on the continental shelf in North Senegal, related the presence of Bolivina spp.…”

Living benthic Foraminifera from the Saquarema lagoonal system (Rio de Janeiro, southeastern Brazil)

“…In Rio de Janeiro state, it was the dominant species in Guanabara Bay and Itaipu Lagoon. This species was also found in in Italy, such as the Laguna di Orbetello (Tuscany), Lago di Varano (Apulia) and Stagno di Santa Gilla (Sardinia), all in the most confined areas (Frontalini et al 2009(Frontalini et al , 2010(Frontalini et al , 2014). …”

“…Sediment characteristics are one of the principal determinants of their distribution; benthic Foraminifera live more abundantly in silty and clayey sediments. However, Foraminifera are also can be influenced by sediment pollution (Bhalla & Nigam 1986;Alve & Olsgard 1999;Frontalini & Coccioni 2008;Martins et al 2013Martins et al , 2014Martins et al , 2015a. The aim of this study is to characterize the living benthic foraminiferal assemblages on surface sediments from the SLS in order to serve as a background to future ecological and paleoecological studies, as well as contribute to research on the biodiversity and distribution of Foraminifera throughout Brazilian coastal lagoons.…”