Transcript

Effect of temperature, salinity and irradiance on growth andphotosynthesis of Ulva proliferaXIAO Jie1, ZHANG Xiaohong1, 2, GAO Chunlei1*, JIANG Meijie1, LI Ruixiang1, WANG Zongling1, LI Yan1,FAN Shiliang1, ZHANG Xuelei1

1 Key Laboratory of Science and Engineering for Marine Ecology and Environment, The First Institute ofOceanography, State Oceanic Administration, Qingdao 266061, China

2 Qingdao Environmental Monitoring Station, Qingdao 266071, China

Received 31 August 2015; accepted 24 December 2015

©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2016

Abstract

Intensive Pyropia aquaculture in the coast of southwestern Yellow Sea and its subsequent waste, includingdisposed Ulva prolifera, was speculated to be one of the major sources for the large-scale green tide proceeding inthe Yellow Sea since 2007. It was, however, unclear how the detached U. prolifera responded and resumedgrowing after they detached from its original habitat. In this study, we investigated the growth and photosyntheticresponse of the detached U. prolifera to various temperature, salinity and irradiance in the laboratory. Thephotosynthetic rate of the detached U. prolifera was significantly higher at moderate temperature levels (14–27°C)and high salinity (26–32), with optimum at 23°C and 32. Both low (<14°C) and highest temperature (40°C), as wellas low salinity (8) had adverse effects on the photosynthesis. Compared with the other Ulva species, U. proliferashowed higher saturated irradiance and no significant photoinhibition at high irradiance, indicating the greattolerance of U. prolifera to the high irradiance. The dense branch and complex structure of floating mats couldhelp protect the thalli and reduce photoinhibition in field. Furthermore, temperature exerted a stronger influenceon the growth rate of the detached U. prolifera compared to salinity. Overall, the high growth rate of this detachedU. prolifera (10.6%–16.7% d–1) at a wide range of temperature (5–32°C) and salinity (14–32) implied its bloomingtendency with fluctuated salinity and temperature during floating. The environmental parameters in thesouthwestern Yellow Sea at the beginning of green tide were coincident with the optimal conditions for thedetached U. prolifera.

Key words: Ulva prolifera, green tide, photosynthesis, growth rate, temperature, salinity

Citation: Xiao Jie, Zhang Xiaohong, Gao Chunlei, Jiang Meijie, Li Ruixiang, Wang Zongling, Li Yan, Fan Shiliang, Zhang Xuelei. 2016. Effectof temperature, salinity and irradiance on growth and photosynthesis of Ulva prolifera. Acta Oceanologica Sinica, 35(10): 114–121, doi:10.1007/s13131-016-0891-0

1  IntroductionThe world’s largest green tides have been proceeding in the

Yellow Sea, China in recent years (Liu et al., 2010a, 2013a, c; Ye etal., 2011). The causative species was confirmed to be Ulva prolif-era, a cosmopolitan fouling green macroalga distributed alongthe coasts of China and many other countries around the world(Hayden and Waaland, 2002; Hayden et al., 2003; Leliaert et al.,2009). Field surveys and satellite image analyses indicated thatmacroalgae floating mats were consistently formed in the coastalwater of southwestern Yellow Sea where intensive Pyropia(formerly known as Porphyra, Sutherland et al., 2011) aquacul-ture is conducted (Hu et al., 2010; Liu et al., 2010a; Keesing et al.,2011). Large amounts of macroalgal wastes disposed by farmersduring Pyropia harvest season, consisting of U. prolifera, wereconsidered to be one of the major sources for floating U. prolif-era mats (Liu et al., 2010a, 2013a; Keesing et al., 2011).

The floating U. prolifera, forming green tides in the YellowSea of China, exhibited unique features both in morphology and

reproduction compared to the strains in Japan and those previ-ously described in China (Ding and Luan, 2009; Hiraoka et al.,2011). Extremely filamentous, diversified reproduction of thepelagic U. prolifera and high nutrient absorption activity wasconsidered as physiological adaptation to the floating environ-ment, which attributed to the huge biomass accumulation dur-ing floating (Lin et al., 2008; Gao et al., 2010; Wang et al., 2012). Itwas, however, still unclear how the disposed macroalgae be-came afloat, physiologically adapted to the fluctuated environ-ment, and formed the initial large-scale floating mats. The de-tached U. prolifera could undergo various environmental stressesduring the sessile stage on the muddy flats, such as nutrient lim-itation, extreme low and high temperature and salinity (osmoticstress), high irradiance exposure, etc. Therefore, it is the key pro-cess linking detached and floating macroalgae and critical for un-derstanding the green tide formation at early stage that how thedetached algae perform under those stressful environmentalconditions and then resume growth and proliferation.

Acta Oceanol. Sin., 2016, Vol. 35, No. 10, P. 114–121

DOI: 10.1007/s13131-016-0891-0

http://www.hyxb.org.cn

E-mail: [email protected]

  

Foundation item: The Special Funds for Basic Ocean Science Research of FIO under contract Nos 2012T08, 2014G33 and 2008T30; theNational Natural Science Foundation of China—Shandong Joint Funded Project “Marine Ecology and Environmental Sciences” undercontract No. U1406403; the National Natural Science Foundation of China under contract Nos 41206162 and 41206161; the National BasicResearch Program (973 Program) of China under contract No. 2010CB428703.*Corresponding author, E-mail: [email protected]

Thus in this study, we examined the growth and photosyn-thetic responses of detached U. prolfiera to various temperature,salinity and irradiance levels in laboratory, and furthermore toassess its capability of acclimating to the floating environmentand its contributions to the formation of floating mats. Althoughnumbers of research had studied the growth and photosynthesisof Ulva spp. (Taylor et al., 2001; Wang et al., 2007; Fu et al., 2008;Hiraoka and Oka, 2008; Li et al., 2009; Choi et al., 2010; Kim et al.,2011; Gao et al., 2012; Luo et al., 2012), the results varied signific-antly among research. We compared our data with the previousresearch, especially the growth rate of Ulva spp. (including U.prolifera at various stages), in order to explain how and why thedata varied and try to get a consistent answer for the future re-search.

2  Materials and methods

2.1  Sample collection and laboratory acclimationIn May of 2009, macroalgae were collected from the Pyropia

aquaculture rafts in the coastal water (seawater surface temper-ature 16.2°C, salinity 31) of Rudong, southern Jiangsu province.The samples were transferred to the laboratory in a cooler, andU. prolifera was sorted out based on the morphology (Ding andLuan, 2009) and further identified with a molecular assay (Xiao etal., 2013). The algal thalli were then cleaned and temporarilymaintained in the laboratory (salinity 32, temperature 15°C, and100 μmol photons m–2 s–1 with 12L:12D photoperiod).

2.2  Growth experimentTo test the effects of temperature and salinity on the growth of

detached U. prolifera, ten temperature levels (5, 8, 11, 14, 17, 20,23, 26, 29, 32°C) were fully crossed with four salinity levels (14, 20,26, 32), which resulted in 40 treatments. The fresh algal thalliwere cleaned and dried gently using the paper towel before theywere weighted on a balance. For each treatment, approximately(0.50±0.01) g (wet weight) freshly collected algal thalli wereweighted and incubated in 500 mL PES (Provasoli’s enriched sea-water medium, Bold and Wynne, 1978) enriched natural seawa-ter with addition of GeO2 (final concentration of 0.50 mg/L) to in-hibit the diatom growing. Each treatment was tested in triplicate.The natural seawater (salinity 32) was collected from Shazikou ofQingdao, filtered and autoclaved before using. Culture mediumwith salinity lower than 32 was obtained by adding distilled wa-ter to the sterilized natural seawater until the desired salinity. Themedium was refreshed every 3 d and gently stirred 3–5 timesevery day to ensure well-mixed nutrients. Light intensity was setat 90–100 μmol photos m–2 s–1 with 12L:12D cycle, and the beak-ers in each incubator were rotated frequently to ensure the simil-ar light attenuations.

During the 15-day culture period, the algae were harvestedevery three days and weighted after they were tap dried with pa-per towel. The specific growth rate (SGR) was calculated basedon the equation (Brinkhuis, 1985): SGR (% d– 1) = [ln(Wt/W0)]/t×100%, where W0 and Wt were initial and final wetweight of cultured algae, t was the culture period in days.

2.3  Photosynthesis experimentApproximately 5 g of freshly collected U. prolifera thalli was

cultured in 250 mL PES enriched natural seawater at salinity 32.Total of nine temperature gradients (1, 5, 11, 14, 20, 23, 27, 32 and40°C) were set to evaluate the effects of temperatures on the pho-tosynthesis of the detached U. prolifera. Another group of U. pro-lifera thalli were cultured at 20°C, but at different salinity levels(8, 14, 20, 26 and 32) in order to test the photosynthetic response

of U. prolifera to the salinity variations. Culture medium with sa-linity lower than 32 was obtained as described in previous sec-tion. All the treatments were maintained in the incubators with90–100 μmol photons m–2 s–1 irradiance at 12L:12D photoperiod.The algae were acclimated to the desired experimental condi-tions for 3 days before their photosynthetic performance wasevaluated.

The photosynthesis of the acclimated U. prolifera algae wastested by the technique of O2 evolution, in which the photosyn-thesis and respiration rates were determined by the O2 concen-tration changes in light and dark chambers. Initial and final O2

concentrations were measured by an Oxygraph respirometer(Hansatech Instruments Ltd., UK). Specifically, the treated algalthalli was cut into segments, and acclimated in dark under eachtreatment condition for 1 h. Then algal samples (approximately100 mg, wet weight) were put in a closed respiration chambercontaining 2 mL distilled seawater. Temperature of the chamberwas controlled at the pre-acclimated levels by the circulated wa-ter bath. Similarly, the water inside the chamber was at the cul-turing salinity for each treatment and mixed using a magneticstirring bar during the experiments.

For the salinity experiment, the photosynthesis-irradiance(P/I) curve was constructed using the net photosynthetic rates(Pn) at irradiance levels of 0, 20, 60, 100, 300, 600, 900, 1 200 and1 450 μmol photons m–2 s–1, respectively. While the irradiancelevels were 0, 20, 40, 60, 80, 100, 150, 200, 300, 400, 500, 600, 1 220and 1 450 μmol photons m–2 s–1 in the temperature experiment.The photosynthetic performance was evaluated in triplicate bysubsampling of each treatment.

The oxygen consumption rate in dark was used as the respira-tion rate (Rd), and the net photosynthetic rate at each irradiancelevel was calculated as the difference in oxygen concentration inthe chamber at the beginning and end of incubation. The P/Icurve was determined by a nonlinear regression based on themodel described by Baly (1935): Pn = (α I Pnmax)/(α I + Pnmax)–Rd,wherein Pn is the net photosynthetic rate (μmol O2 g–1 h–1), α isthe slope of P/I curve when I ≤ 200 μmol photons m–2 s–1, Pnmax

is the maximum net photosynthetic rate (μmol O2 g–1 h–1), and Rd

is the respiration rate in dark. Other parameters were calculatedaccording to Binzer and Middelboe (2005): compensation irradi-ance Ic = Rd/α; gross photosynthetic rate Pg = Pn + Rd; light satura-tion Isat = Pgmax/α, where Pgmax is the maximum gross photosyn-thetic rate; the light-use efficiency at high irradiance LUE (μmolO2 g–1 h–1/μmol photons m–2 s–1) = Pgmax/Imax, wherein Imax is themaximum irradiance used in the experiment.

2.4  Statistic analysisTwo-way analysis of variance (ANOVA) was performed using

the Origin software package (OriginLab Co., USA) to test the sig-nificant effects of salinity and temperature on growth of the de-tached U. prolifera thalli. The photosynthetic data was tested fornormality and homogeneity of variance using a hyperbolic non-linear regression model, and then the photosynthetic paramet-ers were calculated as above after the testing. Figures were drawnby Origin.

3  Results

3.1  Growth of detached U. prolifera under various temperatureand salinity treatmentsThe U. prolifera thalli from the Pyropia rafts maintained a

high growth rate of 10.6%–16.7% d–1 at all temperature-salinitycombinations. The algal thalli could still grow with SGR of 10%d–1 at the lowest temperature of 5°C, and reached the highest SGR

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(16.7% d–1) at 20°C, salinity 32 (Fig. 1). Statistical analysis indic-ated that growth rate of the detached U. prolifera thalli was signi-ficantly affected by both salinity and temperature, and further-more by the interaction between these two factors (Table 1).However, temperature exerted a stronger influence on the SGR asindicated in Fig. 1. The values of SGR were generally highest at20°C, and decreased towards both lower and higher temperat-ures. SGR increased by about 4% d–1 from 5°C to 20°C at salinity26. In comparison, the variation of SGR at different salinity levelswas relatively small at the testing range of 14–32. It was highest athigh salinities (20–32).

3.2  Effect of temperature on photosynthesis of U. proliferaThe photosynthesis-irradiance (P/I) responses of U. prolifera

followed the hyperbolic curves with a fast increasing of net pho-tosynthetic rate (Pn) at low irradiance level until Pn was saturatedirradiance (Fig. 2). As indicated in Fig. 2, the temperature signi-ficantly impacted the P/I responses of U. prolifera. The photosyn-thesis, in terms of Pnmax, dramatically increased when temperat-ure >14°C, reached maximum of 475.24 μmol O2 g–1 h–1 at 23°C,and then decreased at the highest temperature (40°C, Fig. 2b).Consequently, the light utilization efficiency (LUE) fluctuatedsimilarly as Pnmax, which was significantly higher when temperat-ure was between 14°C and 32°C while much lower at low (<14°C)and highest temperatures (40°C). The LUE values at temperat-ures 14–32°C were about one magnitude higher than those at lowtemperatures, indicating a high photosynthetic activity and lightutilization for the detached U. prolifera at this range (14–32°C).

The other parameters (α, Ic, Isat and Rd) fluctuated with tem-peratures and showed different patterns (Table 2). Ic and Isat weregenerally increasing with temperature, while the photosyntheticefficiency at low irradiance (α) peaked at 20–23°C. Similar to α,the values of Rd were high at 20–27°C. It was worth noting that anabnormally high value of Rd observed when the algae weretreated at the highest temperature (40°C). Given the slight drop ofPnmax and LUE at this temperature (Fig. 2), the highest values forthe dark respiration rate at 40°C indicated that U. prolifera was ata critical condition at such a high temperature.

3.3  Effect of salinity and irradiance on the photosynthesis of U.proliferaIn the salinity experiment, Pnmax increased significantly with

salinity (Fig. 3a) and the highest Pnmax (387.8 μmol O2 g–1 h–1) wasobserved at salinity 32. As a result, the light utilization efficiency(LUE) increased dramatically with salinity (Fig. 3b). The highest

 

Fig. 1.  Contour plot of averaged SGR (% d–1) of U. prolif-era over the 15-day culture period as a function of temper-ature and salinity.

Table 1.  Two-way ANOVA tests on the SGRs of U. prolifera amongdifferent temperature and salinity treatments (SS means sum ofsquare)

Parameter SS df F P

Temperature 176.9 9 39.2 <0.01

Salinity 23.7 3 15.8 <0.01

Interaction 40.2 27 3.0 <0.01

 

Fig. 2.  Regressions of photosynthetic rate vs. irradiance (P/I curves) for U. prolifera at various temperature levels (a) and changes ofmaximum photosynthetic rate (Pnmax) and light utilization efficiency (LUE) of the detached U. prolifera with temperatures (b). Errorbars=SD.

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LUE at 32 was approximately one magnitude higher than that atsalinity 8 and around 3 times of that at 14, indicating a significantincreasing of light utilization when the U. prolifera was in highsalinity seawater. In contrast, the two related parameters (Rd andIc) exhibited a different pattern from that of LUE and Pnmax,which was lowest at salinity 20 and increased at both low andhigh salinity (Table 3).

Unlike the P/I curves in the temperature experiment, thecurves at different salinities were prone to be more linear (Figs 2and 3). The treatment of salinity 32 and temperature 20°C wastested in both experiments, while the resulting parameters estim-ated (Figs 2 and 3, Tables 2 and 3) were quite different. Values ofPnmax and LUE at the treatment combination of 20°C and salinity32 were apparently higher in salinity experiment (600 μmol O2 g–1

h–1 and 0.43) than those from temperature experiment (442 μmolO2 g–1 h–1 and 0.35, respectively).

Additionally, the saturation irradiance (Isat) of the tested U.prolifera varied from 127–809 μmol photons m–2 s–1 for the ninetemperature treatments to 29–671 μmol photons m–2 s–1 for thefive salinity treatments. Except for the lowest salinity (8), the val-

ues of Isat for the other groups were all larger than 100 μmolphotons m–2 s–1. No evident photosynthetic inhibition was ob-served for the tested U. prolifera even at such high irradiance asover 1 000 μmol photons m–2 s–1 (Figs 2 and 3). Except for a fewP/I curves at extremely low salinity and temperature (e.g., 1°C inFig. 2a and salinity 8 in Fig. 3a), the photosynthetic rates did notdecrease significantly after the irradiance reached saturation(Isat), but increased slightly.

4  DiscussionIn this study, we examined the photosynthetic responses of

detached U. prolifera to short-term temperature, salinity and ir-radiance fluctuations in order to understand the underlyingphysiological mechanism that detached U. prolifera adjusted oracclimated to these environmental changes. We found that U.prolifera could tolerate a wide range of temperature and salinity,and maintained growing with the rate of 10.6%–16.7% d–1 at thetested temperature and salinity ranges. Compared to the relat-ively smaller variation from salinity, the growth rate of detachedU. prolifera was more influenced by the temperature with highestSGR at 20°C. The photosynthesis of these detached U. prolifera,on the other hand, was quite sensitive to the environmentalchanges, and both extreme low or high temperatures and low sa-linity had adverse effects on the photosynthesis. The photosyn-thesis was significantly higher at moderate temperature levels(14–27°C) and high salinity (26–32), with optimum at 23°C and32. No obvious photoinhibition was observed in the test.

As described above, slightly different shapes of P/I curveswere observed in the temperature and salinity experiments. P/I

Table 2.  The photosynthetic parameters of U. prolifera at various temperatures and salinity 32

Photosyntheticparameter

Temperature/°C

1 5 11 14 20 23 27 32 40

α 0.22 0.44 1.04 1.08 1.43 1.43 1.12 0.62 0.56

Ic 12.87 26.90 22.63 33.28 41.00 38.82 53.13 68.14 115.28

Isat 126.67 282.69 165.46 345.48 349.78 372.18 465.20 808.93 682.78

Rd 2.89 11.83 23.43 35.90 58.66 55.35 59.32 41.99 65.04

Note: α represents photosynthetic efficiency at low light (μmol O2 g–1 h–1/μmol photons m–2 s–1), Ic compensation irradiance(μmol photons m–2 s–1), Isat saturated irradiance (μmol photons m–2 s–1), and Rd dark respiration (μmol O2 g–1 h–1).

 

Fig. 3.  Regressions of net photosynthesis rate vs. irradiance (P/I curves) for U. prolifera after 3-day acclimation to 5 salinity levelsand at temperature 20°C (a). Changes of maximum net photosynthetic rate (Pnmax) and light utilization efficiency (LUE) of detachedU. prolifera with different salinity levels (b). Error bars=SD.

Table 3.  The photosynthetic parameters of U. prolifera at differentsalinities and temperature 20°C

Photosyntheticparameter

Salinity

8 14 20 26 32

α 2.29 1.11 0.64 1.20 0.92

Ic 12.58 21.85 7.06 12.28 16.59

Isat 28.54 215.91 622.37 337.35 671.22

Rd 28.78 24.18 4.53 14.76 15.23

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curves at various salinity were prone to be more linear (Fig. 3).Additionally, compared with the other research showing evidentphotoinhibition after Isat (Arnold and Murray, 1980; Binzer andMiddelboe, 2005; Kim et al., 2011), the photosynthesis in mosttreatments of this study did not decrease significantly, but slightlyincreased after Isat (Figs 2 and 3). Unfortunately, the photosyn-thesis of U. prolifera at irradiance higher than 1 450 μmolphotons m–2 s–1 was not tested due to the maximum irradiancelimit of respirometer used in this study. Therefore, it was not de-termined whether the detached U. prolifera had no photoinhibi-tion or was photo inhibited at an extremely high irradiance. Nev-ertheless, the Isat of U. prolifera in this study was higher than theother macroalgae species, indicating great tolerance of this spe-cies to high irradiance. Previously, Arnold and Murray (1980) re-ported various photosynthetic responses (including saturationand compensate irradiance, maximal photosynthesis and pho-toinhibition at high irradiance, etc.) of the benthic green algaefrom different locations (littoral and sublittoral) and with differ-ent morphologies. The intertidal, thin sheet-like and tubular sea-

weeds showed higher productivity while great photoinhibition atfull sunlight (Arnold and Murray, 1980). At the same time, the al-gae with thick, optically dense thallus, such as Codium fragile,had lower productivity but less photoinhibition (Arnold andMurray, 1980). More recently, Binzer and Middelboe (2005) re-ported more linear photosynthesis and irradiance relations forthe samples from single- or multi-species communities com-pared to those from a single-species thallus. It was found thatcompared to the individual thallus, the structure of a wholeaquatic plant (positioning of the thalli) could help the distribu-tion of irradiance, and hence greatly increase the photosyntheticproduction and the irradiance level of photosaturation (Binzerand Middelboe, 2005). The U. prolifera alga used in this studywas highly filamentous (Leliaert et al., 2009; Liu et al., 2010c;Hiraoka et al., 2011). The floating small thallus segments in thetests probably partially covered by each other, hence changed thelight availability and lowered the photosynthetic inhibition athigh irradiance. With stirring, the thalli could be rotated to ex-pose to light, and therefore showed slight increase in photosyn-

Table 4.  Comparisons of maximum daily growth rates (SGRmax) among Ulva spp. from literatures

Taxa1), 2) SGRmax/% d–1 Salinity3) Temperature/°CLaboratory (L) or

on-site (O)Reference

E. compressa 8 15 10 L Taylor et al. (2001)

U. compressa 9 N.D. 15 L Wang et al. (2010)

U. curvata 13 27 20 L Taylor et al. (2001)

U. expansa 7.5 35 N.D. L Fong et al. (1996)

E. intestinalis 4.5 15 N.D. L Fong et al. (1996)

U. lactuca 21–28 N.D. 15–20 O Nielsen and Sand-Jensen (1990)

U. lactuca 16 N.D. N.D. L Ale et al. (2011)

U. linza 6.7 32 20 L Kim et al. (2011)

E. linza 12 27 15 L Taylor et al. (2001)

U. linza 12 N.D. 15 L Luo et al. (2012)

E. linza 4 33 20 L Gao et al. (2012)

U. linza 9.6 27–31 >15 O Wang et al. (2015)

U. pertusa 3.2 20 N.D. L Choi et al. (2010)

U. pertusa 12 30 20 L Liu and Dong (2001)

U. pseudocurvata 25 N.D. 10 L Lüning et al. (2008)

U. rigida 13 23 15 L Taylor et al. (2001)

Enteromorpha 14–26 N.D. 15–20 O Nielsen and Sand-Jensen (1990)

Ulva 25 N.D. 15 O de Paula Silva et al. (2008)

E. prolifera 7.3 20–28 18–25 L Wu et al. (2000)

E. prolifera 3.7 24 25 L Wang et al. (2007)

E. prolifera 3 33‰ 20 L Gao et al. (2012)

E. prolifera (F) 10 N.D. 25 L Fu et al. (2008)

U. prolifera (F) 1.5 25–29 23 L Xin et al. (2009)

U. prolifera (F) 8 30 20 L Li et al. (2009)

U. prolifera (F) 10 30 20 O Wu et al. (2010)

U. prolifera (F) 20 30‰ 16 L Luo and Liu (2011)

U. prolifera (F) 17 30 15 L Luo et al. (2012)

U. prolifera (G) 37 N.D. 20 L Hiraoka and Oka (2008)

U. prolifera (G) 36 N.D. 20 L Liu et al. (2010c)

U. prolifera (G) 27 N.D. 15 L Liu et al. (2010b)

U. prolifera (A) 38 26 20 L Zhang et al. (2012)

U. prolifera (A) 23 N.D. N.D. O Zhang et al. (2013)

U. prolifera (A) 26 27–31 >15 O Wang et al. (2015)

U. prolifera (A) 16 20–32 20 L this study

Note: 1) Enteromorpha was synonymized with Ulva in Tan et al. (1999) and Hayden et al. (2003); 2) Letters in parentheses indicatetypes of the Ulva (Enteromorpha) prolifera samples: F is floating, G germling, and A attached. 3) Unless otherwise specified, the unit ofsalinity is psu. N.D. means not determined.

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thesis at high irradiance. In field, the numerous tubular branch-ing of U. prolifera often forms dense algal mat, especially duringfloating. This floating algal mat with complex structure could par-tially protect the algae at lower part, and maintain high pro-ductivity and growth rate during floating even with high sunlightin the southwestern Yellow Sea. Furthermore, a higher geneticdiversity was observed for the attached U. prolifera populationcompared to the floating one (Zhang et al., 2011; Zhao et al.,2011; Liu et al., 2012) indicating multiple genotypes of U. prolif-era existing on the Pyropia rafts. Our laboratory tests also indic-ated distinct photosynthetic activities of different tissue parts ofthe algae (thalli, root, germlings, etc.). Here in our study, al-though a single species (U. prolifera) was used for both salinityand temperature experiments, the thalli samples tested mightenclosed different genotypes or different tissues parts. A single-species community consisted of multiple genotypes or tissuetypes might be used for this salinity experiment. Thus a highersaturation irradiance and photosynthetic rate would be expectedfor the salinity experiment due to more efficient distribution andphotosynthetic use of light (Binzer and Middelboe, 2005). It wasconfirmed by the observation in our study that Isat and Pnmax atsalinity 32 and 20°C were higher in the salinity experiment thanthose in temperature experiment (Figs 2 and 3, Tables 2 and 3).

The maximum photosynthetic rate of the detached U. prolif-era in this study was relatively higher compared to the other Ulvaspecies and U. prolifera at other stages. A number of researchesinvestigated the photosynthesis of floating ulvoid algae at differ-ent stages in the Yellow Sea, and found variable photosyntheticperformances (Lin et al., 2009, 2011; Kim et al., 2011). By usingthe averaged Chl a content for U. prolifera (about 0.20–0.68 mgChl a g–1; Lin et al., 2011), the photosynthetic rate (Pnmax, 300–600μmol O2 h–1 g–1) of the detached U. prolifera under optimum con-dition from this study was higher than that of floating Ulva① atearly stage (72–245 μmol O2 g–1 h–1) and at late stage (29–100μmol O2 g–1 h–1) in the eastern coast of Yellow Sea (Kim et al.,2011). We also tested the photosynthesis of the floating U. prolif-era collected from the coast of Shandong Province, and con-firmed the higher photosynthetic performance of the detached U.prolifera relative to those floating ones (Gao et al., unpublisheddata)②. Compared to the floating algae which had limit potentialfor growth and reproduction (Lin et al., 2011; Kim et al., 2011),the high photosynthesis of the detached U. prolifera indicated itshigh growth rate and proliferation once they were at optimumconditions, which was confirmed by our growth experiments.

The change of growth rate with temperature and salinity wasrelatively small, but significant. We summarized the maximumgrowth rates (SGRmax) of Ulva spp. from the literatures in Table 4,including U. prolifera at different stages (germling, floating andattached③). Considering the different species, culturing methodsand physio-chemical conditions at every test, it is not surprisingthat SGRs were quite variable (1.5%–38% d–1) even for the singlespecies (e.g., U. prolifera and U. linza). However, the SGRs of U.prolifera from most research (67%) were higher than 10% d–1, inwhich, the values for “germling” and “attached” were evidentlyhigher than the floating ones and the other Ulva species (Table

4). The high SGR of U. prolifera indicated the great ecological ad-vance for this species under the favored environmental condi-tions. High nutrient absorption and assimilation was consideredto contribute greatly to the rapid growth rate and consequentecological success of this species over the other co-occurring ul-void species, especially in the eutrophic waters (Luo et al., 2012;Wang et al., 2012). The U. prolifera strain bloomed in the YellowSea was found to be extremely filamentous (Liu et al., 2010c;Hiraoka et al., 2011), and such an increased surface/volume ratiocould assist the nutrient absorption and light utilization, and fur-ther enhance the photosynthesis and rapid growing (Arnold andMurray, 1980; O’Brien and Wheeler, 1987; Nielsen and Sand-Jensen, 1990). The field growth rate of U. prolifera was estimatedto be 23%–26% d–1 based on the on-site and mesocosm tests un-der local natural environments (surface seawater temperature>15°C, salinity 27–31; Zhang et al., 2013; Wang et al., 2015). Basedon the numerical modeling, such high growth rates were wellenough supporting the rapid floating biomass proliferation at theinitial stage of the green tide in the Yellow Sea (Wang et al., 2015).Besides, the high growth rates in field indicated the optimal localenvironmental conditions favoring blooming of U. prolifera asdiscussed in the following.

Local environmental conditions in the southwestern YellowSea during April–May favored the blooming of the detached U.prolifera, especially the salinity, irradiance and sea surface tem-perature (Table 5). Daily irradiance varied from 0–1 800 μmolphotons m–2 s–1 which did not show any evidence limiting theproductivity of U. prolifera. As shown in Figs 1 and 3, no evidentdecline of SGR and photosynthesis at highest salinity indicatedthat the salinity range tested in this study probably did not coverthe optimal level at which maximum SGR and photosynthetic re-sponse could reach. It needs further investigation whether thedetached U. prolifera could tolerate the higher salinity and per-form a normal or even better biomass accumulation and photo-synthesis. However, the salinity range in this study (8–32)covered the real salinity variation in the coastal water of SubeiShoal, where the U. prolifera bloom initiated (Table 5, Huo et al.,2013; Shi et al., 2015; Wang et al., 2015). Salinity varied little andhad less effect on the growth of the detached U. prolifera asshown above (Fig. 1). The sea surface temperature, on the otherhand, increased rapidly from 9.9°C to 20.3°C (Wang et al., 2015),

Table 5.  Physico-chemical parameters during April to May inand around the Subei Shoal, southwestern Yellow Sea of China

Environmental parameters Range (Mean)

Salinity1) 27–32 (30)

Surface temperature1)/°C 9.9–20.3 (15.3)

Nitrate2)/μmol·L–1 0.2–28.2 (7.8)

Ammnonia2)/μmol·L–1 0.1–4.5 (1.9)

Phosphate2)/μmol·L–1 ≤0.6 (0.2)N:P ratio2) 5.1–230.2 (69.1)

Irradiance3)/μmol photons m–2 s–1 0–1 800

Note: 1) Wang et al. (2015); 2) Shi et al. (2015); 3) the irradiancewas measured on sea surface during April 3–17, 2009 (Gao et al.,unpublished)②.

  

① Although the algae in this study (Kim et al., 2011) was named as U. linza, the type specimen was same as green tide-forming U.prolifera in the Yellow Sea based on morphology and molecular data (Kang et al., 2014). So the growth rate data from Kim et al. (2011)was cited.② Gao Chunlei, Fan Shiliang, Xiao Jie. Photosynthesis of Ulva prolifera in field.③ The words “attached” in Table 4 and “detached” in the text have the similar meaning, referring to the U. prolifera materialsseparated from its original substrata.

  XIAO Jie et al. Acta Oceanol. Sin., 2016, Vol. 35, No. 10, P. 114–121 119

and could be one of the important triggers for U. prolifera bloom-ing. Fan et al. (2015) observed that the macroalgal assemblage onthe Pyropia rafts was sensitive to the seawater temperature andU. prolifera biomass was prone to rising with temperature. Ourmultiple field surveys also implied a consistent sea surface tem-perature (≥15°C) when the floating U. prolifera started to prolif-erate rapidly and the large-scale floating mats were firstly spot-ted in the Yellow Sea (Fan et al., 2015; Wang et al., 2015).

AcknowledgementsThe authors thank Song Wei and Xu Jintao, Wang Xiaona for

their assistance with sample collection.

ReferencesAle M T, Mikkelsen J D, Meyer A S. 2011. Differential growth re-

sponse of Ulva lactuca to ammonium and nitrate assimilation. JAppl Phycol, 23(3): 345–351

Arnold K E, Murray S N. 1980. Relationships between irradiance andphotosynthesis for marine benthic green algae (Chlorophyta) ofdiffering morphologies. J Exp Mar Bio Ecol, 43(2): 183–192

Baly E C C. 1935. The kinetics of photosynthesis. Proc Roy Soc B BiolSci, 117(804): 218–239

Binzer T, Middelboe A L. 2005. From thallus to communities: scale ef-fects and photosynthetic performance in macroalgae com-munities. Mar Ecol Prog Ser, 287: 65–75

Bold H C, Wynne M J. 1978. Introduction to the Algae: Structure andReproduction. New Jersey: Prentice Hall limited Company,77–130

Brinkhuis B H. 1985. Growth patterns and rates. In: Littler M M, Lit-tler D S, eds. Handbook of Phycological Methods, EcologicalField Methods: Macroalgae. Cambridge: Cambridge UniversityPress, 461–477

Choi T S, Kang E J, Kim J H, et al. 2010. Effect of salinity on growthand nutrient uptake of Ulva pertusa (Chlorophyta) from an eel-grass bed. Algae, 25(1): 17–26

de Paula Silva P H, McBride S, de Nys R, et al. 2008. Integrating fila-mentous ‘green tide’ algae into tropical pond-based aquacul-ture. Aquaculture, 284(1–4): 74–80

Ding Lanping, Luan Rixiao. 2009. The taxonomy, habit, and distribu-tion of a green alga Enteromorpha prolifera (Ulvales, Chloro-phyta). Oceanol Limnol Sin (in Chinese), 40(1): 68–71

Fan Shiliang, Fu Mingzhu, Wang Zongling, et al. 2015. Temporal vari-ation of green macroalgal assemblage on Porphyra aquacul-ture rafts in the Subei Shoal, China. Estuar Coast Shelf Sci, 163:23–28

Fong P, Boyer K E, Desmond J S, et al. 1996. Salinity stress, nitrogencompetition, and facilitation: what controls seasonal succes-sion of two opportunistic green macroalgae?. J Exp Mar BioEcol, 206(1–2): 203–221

Fu Gang, Yao Jianting, Liu Fuli, et al. 2008. Effect of temperature andirradiance on the growth and reproduction of Enteromorphaprolifera J. Ag. (Chlorophycophyta, Chlorophyceae). Chin JOceanol Limnol, 26(4): 357–362

Gao Shan, Chen Xiaoyuan, Yi Qianqian, et al. 2010. A strategy for theproliferation of Ulva prolifera, main causative species of greentides, with formation of sporangia by fragmentation. PLoS One,5(1): e8571

Gao Bingbing, Zheng Chunfang, Xu Juntian, et al. 2012. Physiologicalresponses of Enteromorpha linza and Enteromorpha proliferato seawater salinity stress. Chin J Appl Ecol (in Chinese), 23(7):1913–1920

Hayden H S, Blomster J, Maggs C A, et al. 2003. Linnaeus was right allalong: Ulva and Enteromorpha are not distinct genera. Eur JPhycol, 38(3): 277–294

Hayden H S, Waaland J R. 2002. Phylogenetic systematics of the Ul-vaceae (Ulvales, Ulvophyceae) using chloroplast and nuclearDNA sequences. J Phycol, 38(6): 1200–1212

Hiraoka M, Oka N. 2008. Tank cultivation of Ulva prolifera in deepseawater using a new “germling cluster” method. J Appl Phycol,

20(1): 97–102Hiraoka M, Ichihara K, Zhu Wenrong, et al. 2011. Culture and hybrid-

ization experiments on an Ulva clade including the Qingdaostrain blooming in the Yellow Sea. PLoS One, 6(5): e19371

Hu Chuanmin, Li Daqiu, Chen Changsheng, et al. 2010. On the recur-rent Ulva prolifera blooms in the Yellow Sea and East ChinaSea. J Geophys Res, 115(C5): C05017

Huo Yuanzi, Zhang Jianheng, Chen Liping, et al. 2013. Green algaeblooms caused by Ulva prolifera in the southern Yellow Sea:identification of the original bloom location and evaluation ofbiological processes occurring during the early northwardfloating period. Limnol Oceanogr, 58(6): 2206–2218

Kang E J, Kim J H, Kim K, et al. 2014. Re-evaluation of green tide-forming species in the Yellow Sea. Algae, 29(4): 267–277

Keesing J K, Liu Dongyan, Fearns P, et al. 2011. Inter-and intra-annu-al patterns of Ulva prolifera green tides in the Yellow Sea dur-ing 2007–2009, their origin and relationship to the expansion ofcoastal seaweed aquaculture in China. Mar Pollut Bull, 62(6):1169–1182

Kim J H, Kang E J, Park M G, et al. 2011. Effects of temperature and ir-radiance on photosynthesis and growth of a green-tide-form-ing species (Ulva linza) in the Yellow Sea. J Appl Phycol, 23(3):421–432

Leliaert F, Zhang Xiaowen, Ye Naihao, et al. 2009. Identity of theQingdao algal bloom. Phycol Res, 57(2): 147–151

Li Ruixiang, Wu Xiaowen, Wei Qinsheng, et al. 2009. Growth of En-teromorpha prolifera under different uutrient conditions. AdvMarine Sci (in Chinese), 27(2): 211–216

Lin Apeng, Shen Songdong, Wang Jianwei, et al. 2008. Reproductiondiversity of Enteromorpha prolifera. J Integr Plant Biol, 50(5):622–629

Lin Apeng, Shen Songdong, Wang Guangce, et al. 2011. Comparisonof chlorophyll and photosynthesis parameters of floating andattached Ulva prolifera. J Integr Plant Biol, 53(1): 25–34

Lin Apeng, Wang Chao, Qiao Hongjin, et al. 2009. Study on the pho-tosynthetic performances of Enteromorpha prolifera collectedfrom the surface and bottom of the sea of Qingdao sea area.Chin Sci Bull, 54(3): 399–404

Liu Jingwen, Dong Shuanglin. 2001. Nutrient metabolism and themajor nutrient uptake kinetics of seaweeds. Plant Physiol Com-mun (in Chinese), 37(4): 325–330

Liu Dongyan, Keesing J K, Dong Zhijun, et al. 2010a. Recurrence ofthe world’s largest green-tide in 2009 in Yellow Sea, China: Por-phyra yezoensis aquaculture rafts confirmed as nursery formacroalgal blooms. Mar Pollut Bull, 60(9): 1423–1432

Liu Dongyan, Keesing J K, He Peimin, et al. 2013a. The world’s largestmacroalgal bloom in the Yellow Sea, China: formation and im-plications. Estuar Coast Shelf Sci, 129: 2–10

Liu Feng, Pang Shaojun, Chopin T, et al. 2010b. The dominant Ulvastrain of the 2008 green algal bloom in the Yellow Sea was notdetected in the coastal waters of Qingdao in the followingwinter. J Appl Phycol, 22(5): 531–540

Liu Feng, Pang Shaojun, Chopin T, et al. 2013b. Understanding therecurrent large-scale green tide in the Yellow Sea: temporal andspatial correlations between multiple geographical, aquacul-tural and biological factors. Mar Environ Res, 83: 38–47

Liu Feng, Pang Shaojun, Xu Na, et al. 2010c. Ulva diversity in the Yel-low Sea during the large-scale green algal blooms in 2008–2009.Phycol Res, 58(4): 270–279

Liu Feng, Pang Shaojun, Zhao Xiaobo, et al. 2012. Quantitative, mo-lecular and growth analyses of Ulva microscopic propagules inthe coastal sediment of Jiangsu province where green tides ini-tially occurred. Mar Environ Res, 74: 56–63

Lüning K, Kadel P, Pang Shaojun. 2008. Control of reproductionrhythmicity by environmental and endogenous signals in Ulvapseudocurvata (Chlorophyta). J Phycol, 44(4): 866–873

Luo Minbo, Liu Feng. 2011. Salinity-induced oxidative stress and reg-ulation of antioxidant defense system in the marine macroalgaUlva prolifera. J Exp Mar Bio Ecol, 409(1–2): 223–228

Luo Minbo, Liu Feng, Xu Zhaoli. 2012. Growth and nutrient uptakecapacity of two co-occurring species, Ulva prolifera and Ulva

120 XIAO Jie et al. Acta Oceanol. Sin., 2016, Vol. 35, No. 10, P. 114–121  

linza. Aquat Bot, 100: 18–24Nielsen S L, Sand-Jensen K. 1990. Allometric settling of maximal pho-

tosynthetic growth rate to surface/volume ratio. Limnol Ocean-ogr, 35(1): 177–180

O’Brien M C, Wheeler P A. 1987. Short term uptake of nutrients byEnteromorpha prolifera (Chlorophyceae). J Phycol, 23(4):547–556

Shi Xiaoyong, Qi Mingyan, Tang Hongjie, et al. 2015. Spatial and tem-poral nutrient variations in the Yellow Sea and their effects onUlva prolifera blooms. Estuar Coast Shelf Sci, 163: 36–43

Sutherland J E, Lindstrom S C, Nelson W A, et al. 2011. A new look atan ancient order: generic revision of the Bangiales (Rhodo-phyta). J Phycol, 47(5): 1131–1151

Tan I H, Blomster J, Hansen G, et al. 1999. Molecular phylogeneticevidence for a reversible morphogenetic switch controlling thegross morphology of two common genera of green seaweeds,Ulva and Enteromorpha. Mol Biol Evol, 16(8): 1011–1018

Taylor R, Fletcher R L, Raven J A. 2001. Preliminary studies on thegrowth of selected ‘Green tide’ algae in laboratory culture: ef-fects of irradiance, temperature, salinity and nutrients ongrowth rate. Bot Mar, 44: 327–336

Wang Yangyang, Huo Yuanzi, Cao Jiachun, et al. 2010. Influence oflow temperature and low light intensity on growth of Ulva com-pressa. Journal of Fishery Sciences of China (in Chinese), 17(3):593–599

Wang Ying, Wang You, Zhu Lin, et al. 2012. Comparative studies onthe ecophysiological differences of two green tide macroalgaeunder controlled laboratory conditions. PLoS One, 7(8): e38245

Wang Zongling, Xiao Jie, Fan Shiliang, et al. 2015. Who made theworld’s largest green tide in China?—an integrated study on theinitiation and early development of the green tide in YellowSea. Limnol Oceanogr, 60(4): 1105–1117

Wu Hongxi, Xu Aiguang, Wu Meining. 2000. Preliminary study on ex-perimental ecology of Enteromorpha prolifera (Miill.). J Zheji-

ang Ocean Univer (Nat Sci) (in Chinese), 19(3): 230–234Wang Jianwei, Yan Binlun, Lin Apeng, et al. 2007. Ecological factor re-

search on the growth and induction of spores release in Entero-morpha prolifera (Chlorophyta). Marine Science Bulletin (inChinese), 26(2): 60–65

Wu Xiaowen, Li Ruixiang, Xu Zongjun, et al. 2010. Mesocosm experi-ments of nutrient effects on Enteromorpha prolifera growth.Adv Mar Sci, (in Chinese), 28(4): 538–544

Xiao Jie, Li Yan, Song Wei, et al. 2013. Discrimination of the commonmacroalgae (Ulva and Blidingia) in coastal waters of YellowSea, northern China, based on restriction fragment-lengthpolymorphism (RFLP) analysis. Harmful Algae, 27: 130–137

Xin Dinghao, Ren Song, He Peimin, et al. 2009. Preliminary study onexperimental ecology of Enteromorpha in Yellow Sea. Mar En-viron Sci (in Chinese), 28(2): 190–192

Ye Naihao, Zhang Xiaowen, Mao Yuze, et al. 2011. ‘Green tides’ areoverwhelming the coastline of our blue planet: taking theworld’s largest example. Ecol Res, 26(3): 477–485

Zhang Jianheng, Huo Yuanzi, Yu Kefeng, et al. 2013. Growth charac-teristics and reproductive capability of green tide algae in Rud-ong coast, China. J Appl Phycol, 25(3): 795–803

Zhang Xiaohong, Wang Zongling, Li Ruixiang, et al. 2012. Microscop-ic observation on population growth and reproduction of En-tromorphra prolifera under different temperature and salinity.Adv Mar Sci (in Chinese), 30(2): 276–283

Zhang Xiaowen, Xu Dong, Mao Yuze, et al. 2011. Settlement of veget-ative fragments of Ulva prolifera confirmed as an importantseed source for succession of a large-scale green tide bloom.Limnol Oceanogr, 56(1): 233–242

Zhao Jin, Jiang Peng, Liu Zhengyi, et al. 2011. Genetic variation ofUlva (Enteromorpha) prolifera (Ulvales, Chlorophyta)–thecausative species of the green tides in the Yellow Sea, China. JAppl Phycol, 23(2): 227–233

  XIAO Jie et al. Acta Oceanol. Sin., 2016, Vol. 35, No. 10, P. 114–121 121


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