History of the introduction of a species resembling the benthic foraminifera Nonionella stella in the Oslofjord (Norway): morphological, molecular and paleo-ecological evidences

Noémie Deldicq

doi:10.3391/ai.2019.14.2.03

Abstract

Specimens resembling the benthic foraminifera Nonionella stella (Cushman and Moyer, 1930), a morphospecies originally described from the San Pedro Basin, California, USA, were observed for the first time in the Oslofjord (Norway) in 2012. This study investigates the Oslofjord Nonionella population in order to confirm its nonindigenous species (NIS) status and assess its introduction time. Morphological characterisation based on SEM imaging complemented by molecular identification using small subunit (SSU) rDNA sequencing and assessment of the recent past record (sediment core), were performed on material collected in the Oslofjord in 2016. Examination of the dead fauna showed that specimens resembling N. stella only appeared recently in the Oslofjord, confirming the NIS status of this population. Moreover, DNA results indicate that the Oslofjord specimens differ genetically from N. stella sampled in the Santa Barbara Basin (California USA). Hence, we propose to use the name Nonionella sp. T1 for the specimens sampled in the Oslofjord for the time being. In the southern part of the Skagerrak, specimens morphologically similar to Nonionella sp. T1 were reported as NIS in the Gullmar fjord (Sweden) in 2011 and in the Skagerrak in 2015. Molecular data indicate that the two populations from Gullmar- and Oslofjords are identical, based on their SSU rDNA sequences. In addition, analyses of foraminiferal dead assemblages suggest that the population from the Gullmar fjord settled prior to the Oslofjord population, i.e. ~ 1985 and about 2010, respectively. This implies that Nonionella sp. T1 may have been transported from Sweden to Norway by northward coastal currents.

Highlights

Introduction of non-indigenous species (NIS) is one of the major threats to biodiversity and ecosystem functioning in coastal waters (Butchart et al 2010; Pyšek and Richardson 2010)
The Oslofjord sediment samples were collected on the 22nd of August 2016 at station Cj3-2016 located in a semi-enclosed basin of the Vestfjord (59°50.683′N; 10°30.603′E, 58 m water depth, Figure 1) using the R/V Trygve Braarud (University of Oslo, Norway)
Of the 85 imaged and dried specimens of Nonionella sp. from the Oslo- and the Gullmar fjords (Supplementary material Figures S1, S2, S3, S4), 32 were successfully sequenced for partial small subunit (SSU) rDNA analysis and a total of 73 sequences were obtained either by direct sequencing or after cloning (Table 1, Figures S2, S3). These sequences were aligned with other nonionid sequences retrieved from GenBank for a comparative analysis (Table 2)

Summary

Introduction

Introduction of non-indigenous species (NIS) is one of the major threats to biodiversity and ecosystem functioning in coastal waters (Butchart et al 2010; Pyšek and Richardson 2010). In 2001, maritime shipping carried 90% of the world’s 5.1 billion tons of international trade (KitePowell 2008) and every day, more than 10,000 species are likely to be transported around the world in the ballast tanks of cargo ships (Carlton 1987; Carlton and Geller 1993) Most of those potential invaders do not survive due to unsuitable environmental conditions (Bax et al 2003). There is a lack of knowledge on smaller body-sized taxa, especially on meiofauna-sized organisms (Occhipinti-Ambrogi et al 2010), which include foraminifera These were found alive in ballast water (Galil and Hülsmann 1997). The benthic foraminifera Trochammina hadai Uchio, 1962 was introduced in the San Francisco Bay in 1983 by ballast water and today, the species accounts for more than 50% of the foraminiferal assemblage in the bay while it contributed only 1.5% when it first appeared (McGann et al 2000, 2012)

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