Assessing Herbivorous Impacts of Apohale sp. on the Ulva prolifera Green Tide in China

An epiphytic gammarid species, Apohyale sp., was abundant in the floating Ulva prolifera (U. prolifera), which forms large-scale green tides in the Yellow Sea (YSGT). Field observation and laboratory experiments were subsequently conducted to study the species identity, abundance, and grazing effects on the floating algal biomass. The abundance of Apohyale sp. showed great spatial variation and varied from 0.03 to 1.47 inds g−1 in the YSGT. In average, each gram of Apohyale sp. body mass can consume 0.43 and 0.60 g algal mass of U. prolifera per day, and the grazing rates varied among the algae cultured with different nutritional seawaters. It was estimated that grazing of Apohale sp. could efficiently reduce ~0.4 and 16.6% of the algal growth rates in Rudong and Qingdao, respectively. The U. prolifera fragments resulting from gnawing of Apohyale sp. had a higher growth rate and similar photosynthetic activities compared to the floating algae, indicating probably positive feedback on the floating algal biomass. This research corroborated the significant impact of Apohyale sp. on the floating algal mass of YSGT through the top-down control. However, further research is needed to understand the population dynamics of these primary predators and hence their correlation with the expansion or decline of YSGT, especially under the complex food webs in the southern Yellow Sea.

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Ulva prolifera green-tide outbreaks and their environmental impact in the Yellow Sea, China

National Science Review ◽

10.1093/nsr/nwz026 ◽

2019 ◽

Vol 6 (4) ◽

pp. 825-838 ◽

Cited By ~ 26

Author(s):

Yongyu Zhang ◽

Peimin He ◽

Hongmei Li ◽

Gang Li ◽

Jihua Liu ◽

...

Keyword(s):

Yellow Sea ◽

Red Tide ◽

Abiotic Factors ◽

Management Strategies ◽

Ulva Prolifera ◽

The Yellow Sea ◽

Green Tide ◽

Biological Interactions ◽

Green Tides ◽

Carbon Cycles

Abstract The Ulva prolifera green tides in the Yellow Sea, China, which have been occurring since 2007, are a serious environmental problem attracting worldwide attention. Despite extensive research, the outbreak mechanisms have not been fully understood. Comprehensive analysis of anthropogenic and natural biotic and abiotic factors reveals that human activities, regional physicochemical conditions and algal physiological characteristics as well as ocean warming and biological interactions (with microorganism or other macroalgae) are closely related to the occurrence of green tides. Dynamics of these factors and their interactions could explain why green tides suddenly occurred in 2007 and decreased abruptly in 2017. Moreover, the consequence of green tides is serious. The decay of macroalgal biomass could result in hypoxia and acidification, possibly induce red tide and even have a long-lasting impact on coastal carbon cycles and the ecosystem. Accordingly, corresponding countermeasures have been proposed in our study for future reference in ecosystem management strategies and sustainable development policy.

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Monitoring the Dissipation of the Floating Green Macroalgae Blooms in the Yellow Sea (2007–2020) on the Basis of Satellite Remote Sensing

Remote Sensing ◽

10.3390/rs13193811 ◽

2021 ◽

Vol 13 (19) ◽

pp. 3811

Author(s):

Deyu An ◽

Dingfeng Yu ◽

Xiangyang Zheng ◽

Yan Zhou ◽

Ling Meng ◽

...

Keyword(s):

Remote Sensing ◽

Yellow Sea ◽

Large Scale ◽

Marine Ecology ◽

The Yellow Sea ◽

Green Tide ◽

Southern Yellow Sea ◽

Simple Method ◽

Green Macroalgae ◽

The Southern Yellow Sea

Large scale green macroalgae blooms (MABs) caused by Ulva prolifera have occurred regularly in the Yellow Sea since 2007. In the MAB dissipation phase, the landing or sinking and decomposition of U. prolifera would alter the physical-chemical environment of seawater and cause ecological, environmental, and economic problems. To understand MAB dissipation features, we used multiple sensors to analyze the spatiotemporal variation of the MAB dissipation phase in the southern Yellow Sea. The results show the variation in the daily dissipation rate (DR) was inconsistent from year to year. Based on the DR variation, a simple method of estimating MAB dissipation days was proposed for the first time. Verification results of the method, from 2018 to 2020, showed the estimated dissipation days were relatively consistent with the results obtained by remote sensing imagery. From 2007 to 2020, the order in which macroalgae landed in the coastal cities of Shandong Peninsula can be roughly divided into two types. In one type, the macroalgae landed first in Rizhao, followed by Qingdao, Rushan, and Haiyang. In the other type, they landed in the reverse order. The MABs annual distribution density showed significant differences in the southern Yellow Sea. These results provided a basis for evaluating the MABs’ impact on marine ecology and formulating the green-tide prevention and control strategies.

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Temporal succession of community structure and biphase ratio in a natural population of Ulva spp. (Chlorophyta) attached to Pyropia rafts in the Yellow Sea, China

Botanica Marina ◽

10.1515/bot-2018-0115 ◽

2019 ◽

Vol 62 (6) ◽

pp. 549-561

Author(s):

Yu Du ◽

Yuan Ao ◽

Yuan He ◽

Yi Yin ◽

Yafeng Ma ◽

...

Keyword(s):

Yellow Sea ◽

Internal Transcribed Spacer ◽

Algal Blooms ◽

Null Model ◽

Ulva Prolifera ◽

The Yellow Sea ◽

Green Tide ◽

Continuous Change ◽

Green Tides ◽

Temporal Succession

Abstract Green tide algal blooms occur worldwide, especially in China’s Yellow Sea, and have caused serious damage to local ecological environments and economies. As a dominant agent of green tides, the green macroalga Ulva has caused widespread concern. In this study, phylogenetic clades were constructed among related Ulva species isolated from Pyropia rafts at six sites over 1.5 years based on internal transcribed spacer (ITS) and tufA sequences. In addition, traditional observation ploidy methods and flow cytometry methods were used to analyse continuous change in the biphase and sex ratios of Ulva species and to assess the changes in phase advantages over time. The results showed that the perennial Ulva populations on rafts mainly consisted of Ulva flexuosa and Ulva prolifera, and the biphasic dominance of the attached Ulva populations changed with the seasons: sporophytes were predominant mainly in winter and spring, and gametophytes were predominant mainly in summer and autumn. At the same time, there were some differences in gametophyte and sporophyte frequencies (mainly sporophyte biased) compared to the null model prediction of a √2:1 ratio, while the sex ratio of male and female gametophytes remained 1:1 throughout the year. Our results indicate the presence of both phases of bloom-forming species of Ulva in green tides year round, and that multiple generations coexist and grow continuously.

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Interactions between selected microalgae and microscopic propagules of Ulva prolifera

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315417001345 ◽

2017 ◽

Vol 98 (7) ◽

pp. 1571-1580 ◽

Cited By ~ 5

Author(s):

Qing Liu ◽

Tian Yan ◽

Rencheng Yu ◽

Qingchun Zhang ◽

Mingjiang Zhou

Keyword(s):

Yellow Sea ◽

Large Scale ◽

Critical Role ◽

Ulva Prolifera ◽

Alexandrium Tamarense ◽

The Yellow Sea ◽

Negative Effects ◽

Green Tides ◽

Complex Interactions ◽

Potential Interactions

Large-scale green tides of Ulva prolifera occur repeatedly in the Yellow Sea, and the microscopic propagules of U. prolifera play a critical role during the development of green tides. Ulva prolifera propagules and microalgae are both present in seawater and share similar niches, but their potential interactions are poorly understood. Nine species of microalgae were selected to study their interactions with the propagules of U. prolifera (gametes) in laboratory. The results showed that settlement of gametes could be inhibited by some microalgae, such as Alexandrium tamarense, Prorocentrum lima and Karenia mikimotoi, at the cell density of blooming (102–103 cells ml–1). Inversely, the germlings germinated from U. prolifera gametes had negative effects on the microalgae, the inhibition rate ranged from 28 to 66%. Our results demonstrated the complex interactions between microalgae and propagules of green algae, which may influence the formation of green tides and their ecological consequences in the Yellow Sea.

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Inter- and intra-annual patterns of Ulva prolifera green tides in the Yellow Sea during 2007–2009, their origin and relationship to the expansion of coastal seaweed aquaculture in China

Marine Pollution Bulletin ◽

10.1016/j.marpolbul.2011.03.040 ◽

2011 ◽

Vol 62 (6) ◽

pp. 1169-1182 ◽

Cited By ~ 153

Author(s):

John K. Keesing ◽

Dongyan Liu ◽

Peter Fearns ◽

Rodrigo Garcia

Keyword(s):

Yellow Sea ◽

Ulva Prolifera ◽

The Yellow Sea ◽

Green Tides ◽

Seaweed Aquaculture ◽

Annual Patterns

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Tempo-spatial distribution and species diversity of green algae micro-propagules in the Yellow Sea during the large-scale green tide development

Harmful Algae ◽

10.1016/j.hal.2014.05.013 ◽

2014 ◽

Vol 39 ◽

pp. 40-47 ◽

Cited By ~ 26

Author(s):

Yan Li ◽

Wei Song ◽

Jie Xiao ◽

Zongling Wang ◽

Mingzhu Fu ◽

...

Keyword(s):

Spatial Distribution ◽

Species Diversity ◽

Green Algae ◽

Yellow Sea ◽

Large Scale ◽

The Yellow Sea ◽

Green Tide

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Spatiotemporal Patterns and Morphological Characteristics of Ulva prolifera Distribution in the Yellow Sea, China in 2016–2018

Remote Sensing ◽

10.3390/rs11040445 ◽

2019 ◽

Vol 11 (4) ◽

pp. 445 ◽

Cited By ~ 10

Author(s):

Yingzhi Cao ◽

Yichen Wu ◽

Zhixiang Fang ◽

Xiaojian Cui ◽

Jianfeng Liang ◽

...

Keyword(s):

Yellow Sea ◽

Vegetation Index ◽

Morphological Changes ◽

Surface Wind ◽

Morphological Characteristics ◽

Ulva Prolifera ◽

Spatiotemporal Patterns ◽

The Yellow Sea ◽

Green Tide ◽

Sea Surface Wind

The world’s largest macroalgal blooms, Ulva prolifera, have appeared in the Yellow Sea every summer on different scales since 2007, causing great harm to the regional marine economy. In this study, the Normalized Difference of Vegetation Index (NDVI) index was used to extract the green tide of Ulva prolifera from MODIS images in the Yellow Sea in 2016–2018, to investigate its spatiotemporal patterns and to calculate its occurrence probability. Using the standard deviational ellipse (SDE), the morphological characteristics of the green tide, including directionality and regularity, were analyzed. The results showed that the largest distribution and coverage areas occurred in 2016, with 57,384 km2 and 2906 km2, respectively and that the total affected region during three years was 163,162 km2. The green tide drifted northward and died out near Qingdao, Shandong Province, which was found to be a high-risk region. The coast of Jiangsu Province was believed to be the source of Ulva prolifera, but it was probably not the only one. The regularity of the boundary shape of the distribution showed a change that was opposite to the variation of scale. Several sharp increases were found in the parameters of the SDE in all three years. In conclusion, the overall situation of Ulva prolifera was still severe in recent years, and the sea area near Qingdao became the worst hit area of the green tide event. It was also shown that the sea surface wind played an important part in its migration and morphological changes.

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