Metabarcoding Reveals Temporal Patterns of Community Composition and Realized Thermal Niches of Thalassiosira Spp. (Bacillariophyceae) from the Narragansett Bay Long-Term Plankton Time Series.

Tatiana A Rynearson,Sarah A Flickinger,Diana N Fontaine

doi:10.3390/biology9010019

Tatiana A Rynearson, Sarah A Flickinger + Show 1 more

Open Access

https://doi.org/10.3390/biology9010019

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Journal: Biology	Publication Date: Jan 16, 2020
Citations: 23	License type: CC BY 4.0

Affiliation: University of Rhode Island

Abstract

Diatoms generate nearly half of marine primary production and are comprised of a diverse array of species that are often morphologically cryptic or difficult to identify using light microscopy. Here, species composition and realized thermal niches of species in the diatom genus Thalassiosira were examined at the site of the Narragansett Bay (NBay) Long-Term Plankton Time Series using a combination of light microscopy (LM), high-throughput sequencing (HTS) of the 18S rDNA V4 region and historical records. Thalassiosira species were identified over 6 years using a combination of LM and DNA sequences. Sixteen Thalassiosira taxa were identified using HTS: nine were newly identified in NBay. Several newly identified species have small cell diameters and are difficult to identify using LM. However, they appeared frequently and thus may play a significant ecological role in NBay, particularly since their realized niches suggest they are eurythermal and able to tolerate the >25 °C temperature range of NBay. Four distinct species assemblages that grouped by season were best explained by surface water temperature. When compared to historical records, we found that the cold-water species Thalassiosira nordenskioeldii has decreased in persistence over time, suggesting that increasing surface water temperature has influenced the ecology of phytoplankton in NBay.

Highlights

The combined activities of individual diatom species generate 40%–45% of oceanic primary production and influence the global cycling of silica and carbon [1,2,3]
Based on light microscopy (LM) records in the long-term dataset, Thalassiosira species were present in 85% of the weekly surface water samples collected between December 2008 and December 2014 (Figure 1)
Using a combination of LM and metabarcoding approaches to analyze 6 years of data from the NBPTS, we found that Thalassiosira species diversity in Narragansett Bay (NBay) is greater than previously recognized

Summary

Introduction

The combined activities of individual diatom species generate 40%–45% of oceanic primary production and influence the global cycling of silica and carbon [1,2,3]. One of the challenges in accurately identifying the activities of individual species and their subsequent ecological and biogeochemical impacts is that many species are morphologically similar, or even identical, at the level of light microscopy [7,8]. Identical or "cryptic" species have been identified in the ecologically important diatom genus Thalassiosira [9,10]. Thalassiosira is one of the most abundant and diverse diatom genera [11] and includes species that are ecologically important components of phytoplankton communities in estuarine, coastal, and open ocean regions [12,13,14,15,16,17]. The identification of Thalassiosira species is known to be difficult, especially using light microscopy (LM) due to subtle differences in frustule morphology [18] and some Thalassiosira species are unidentifiable with LM methods [19]

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