Phytoplankton community diversity is influenced by environmental factors in the coastal East China Sea

Figures & data

Fig. 1. The phytoplankton community structure in surface seawater sampled at Huaniao Island in the coastal East China Sea in spring (17 April 2012 and 24 March–18 April 2013), summer (31 July 2012 and 18 July–8 August 2013), autumn (6 October 2012 and 23 October–12 November 2013) and winter (29 December 2012 and 1–12 January 2013) periods. ‘Others’ include Zetaproteobacteria, Euglenida, Klebsormidiophyceae, Trebouxiophyceae and Ulvophyceae (Form IAB), and Dictyochophyceae, Fragilariophyceae, Pelagophyceae, Eustigmatophyceae, Chrysophyceae and Raphidophyceae (Form ID).

Table 1. Total number of clones, library coverage, number of OTUs, clones of dominant OTUs, diversity index and classification of dominant OTUs derived from Form 1AB and Form 1D rbcL for surface seawater sampled in the coastal East China Sea in spring (17 April 2012 and 24 March–18 April 2013), summer (31 July 2012 and 18 July–8 August 2013), autumn (6 October 2012 and 23 October–12 November 2013) and winter (29 December 2012 and 1–12 January 2013) periods.

	Form 1AB rbcL				Form 1D rbcL
	Spring	Summer	Autumn	Winter	Spring	Summer	Autumn	Winter
Total Clones	154	153	157	123	174	180	167	124
Library Coverage^a	76%	80%	73%	71%	75%	77%	65%	76%
OTUs	37	30	42	36	43	42	59	30
Clones of Dominant OTU	27	67	65	20	62	43	21	64
Shannon Index	2.8	2.4	3.1	2.9	2.8	2.6	3.4	2.5
Chao1 estimator mean (95% Cl)^b	118	68	113	83	64	67	136	122
	(76, 223)	(48,126)	(70, 229)	(50, 187)	(50, 105)	(47, 126)	(87, 260)	(76, 240)
Classification of dominant OTUs	Mamiellophyceae/Bathycoccus prasinos	Mamiellophyceae /Micromonas sp. RCC299	Mamiellophyceae /Micromonas sp. RCC299	Mamiellophyceae /Micromonas sp. RCC299	Dinophyceae /Dinophysis fortii	Coscinodiscophyceae /Skeletonema costatum	Coscinodisco-phyceae /Skeletonema subsalsum	Dinophyceae /Dinophysis fortii

^a Coverage = 1 – (clones with unique amino acid sequences/total number of clones analysed) expressed as %.

^b 95% upper and lower confidence interval for Chao1.

Table 2. Closest relatives to clones amplified by Form 1AB and Form 1D rbcL for surface seawater sampled in the coastal East China Sea in spring (17 April 2012 and 24 March–18 April 2013), summer (31 July 2012 and 18 July–8 August 2013), autumn (6 October 2012 and 23 October–12 November 2013) and winter (29 December 2012 and 1–12 January 2013) periods. Relative OTUs (top three dominant OTUs) were obtained using the NCBI BLAST algorithm.

Sample	Primer pair used	Relative	NT similarity	Average proportion
Spring	AB (154 clones)	Bathycoccus prasinos (AAA87204)	98%	18%
		Methylophaga nitratireducenticrescens	99%	15%
		(AFI83368)
		Chroococcidiopsis sp. CCMP2733	97%	14%
		(AEE92832)
	D (174 clones)	Dinophysis fortii (BAD42428)	99%	36%
		Skeletonema subsalsum	99%	14%
		(ABF60378)
		Skeletonema costatum (AEN19678)	96%	14%
Summer	AB (153 clones)	Micromonas sp. RCC299	99%	44%
		(YP_002808616)
		Celeribacter baekdonensis	93%	16%
		(EKE70466)
		Tetraselmis suecica (ABA02339)	94%	14%
	D (180 clones)	Skeletonema costatum	96%	24%
		(AEN19678)
		Thalassiosira minima (ABF60355)	98%	17%
		Peridinium quinquecorne (BAE94662)	99%	15%
Autumn	AB (157 clones)	Micromonas sp. RCC299	99%	42%
		(YP_002808616)
		Candidatus Thiobios zoothamnicoli	97%	17%
		(ACC95126)
		Arthrospira platensis FACHB-439(AY147205)	93%	8%
	D (167 clones)	Skeletonema subsalsum (ABF60378)	99%	13%
		Dinophysis fortii (BAD42428)	99%	12%
		Plagioselmis sp. TUC-1	97%	11%
		(BAD42425)
Winter	AB (123 clones)	Micromonas sp. RCC299	99%	17%
		(YP_002808616)
		Candidatus Thiobios zoothamnicoli	97%	9%
		(ACC95126)
		Chroococcidiopsis sp. CCMP2733	97%	7%
		(AEE92832)
	D (124 clones)	Dinophysis fortii (BAD42428)	99%	52%
		Thalassiosira profunda (AGX25179)	98%	9%
		Plagioselmis sp. TUC-1(BAD42425)	97%	8%

Fig. 2. Phylogenetic tree obtained from a Neighbour joining analysis for the most dominant OTUs (number of clones in parentheses) discriminated by Form IAB rbcL for surface seawater sampled in the coastal East China Sea in four seasons. Sequences existing in GenBank are included with accession numbers in parentheses. The numbers at the nodes represent full heuristic bootstrap values (with 1000 replicates) greater than 50%. The scale bar represents amino acid substitutions/site.

Fig. 3. Phylogenetic tree obtained from a Neighbour joining analysis of the most dominant OTUs (number of clones in parentheses) discriminated by Form 1D rbcL for surface seawater sampled in the coastal East China Sea in four seasons. Sequences in GenBank are included with accession numbers in parentheses. The numbers around the branches represent full heuristic bootstrap values (with 1000 replicates) greater than 50%. The scale bar represents substitutions/site.

Fig. 4. The relationships between environmental factors and seawater samples collected in the coastal East China Sea in spring (samples 1–10, ▲), summer (samples 11–20, ◯), autumn (samples 21–30, □) and winter (samples 31–39, ²) analysed by Canonical Correspondence Analysis.

Fig. 5. Canonical correspondence analysis showing the relationships between environmental factors and dominant phytoplankton species including: Chroococcidiopsis sp. belonging to Cyanobacteria (●); Bathycoccus prasinos (B. prasinos), Micromonas sp. and Tetraselmis suecica (T. suecica) belonging to Chlorophyta (▼); Skeletonema costatum (S. costatum), Skeletonema subsalsum (S. subsalsum), Thalassiosira minima (T. minima), Pseudo-nitzschia multistriata (P. multistriata), Pseudo-nitzschia americana (P. americana) and Thalassiosira profunda (T. profunda) belonging to diatoms (△); Peridinium quinquecorne (P. quinquecorne) and Dinophysis fortii (D. fortii) belonging to dinoflagellates (■); Plagioselmis sp., Candidatus Thiobios zoothamnicoli (C. T. zoothamnicoli) and Methylophaga nitratireducenticrescens (M. nitratireducenticrescens) belonging to Proteobacteria (²).