Distribution of green algae micro-propagules and their function in the formation of the green tides in the coast of Qinhuangdao,the Bohai Sea, China

Since 2015, a novel green tide has been recurring in the coastal areas of Qinhuangdao at the western coast of the Bohai Sea in China, threatening the environment and ecosystem of the Beidaihe seaside holiday resort along the coast. Micro-propagules of the green algae including gametes, spores, micro-germlings and micro-vegetative fragments play an important role in the formation of green tides. They serve as a "seed source" of green macroalgae, and their distributions could reflect and influence the "algae source" of green tides. In this study,monthly surveys in the inshore and offshore areas of the Qinhuangdao coast were conducted from April to September 2016 and in January 2017 to investigate the tempo-spatial distribution patterns and the biomass variations of the green algae micro-propagules. The obtained results show that micro-propagules were mainly distributed in the inshore areas with a significantly decreasing abundance towards offshore areas. Their biomass was highest in July and August, and lowest in winter. The areas that were affected by the green tides showed a remarkably higher abundance of micro-propagules compared to other areas. These micro-propagules could serve as the "seed" source of green tides. Their distribution patterns indicate that the green tide in the coastal areas of Qinhuangdao originated locally.

Examination of Silicate Limitation of Primary Production in Jiaozhou Bay,North ChinaⅢ.Judgment Method,Rules and Uniqueness of Nutrient Limitation Among N,P,and Si

Analysis and comparison of Jiaozhou Bay data collected from May 1991 to February 1994(12 seasonal investigations) provided by the Ecological Station of Jiaozhou Bay revealed the characteristic spatiotemporal variation of the ambient concentration Si:DIN and Si:16P ratios and the seasonal variation of Jiaozhou Bay Si:DIN and Si:16P ratios showing that the Si:DIN ratios were < 1 throughout the year in Jiaozhou Bay; and that the Si:16P ratios were < 1 throughout Jiaozhou Bay in spring, autumn and winter. The results proved that silicate limited phytoplankton growth in spring, autumn and winter in Jiaozhou Bay. Analysis of the Si:DIN and Si:P ratios showed that the nutrient Si has been limiting the growth of phytoplankton throughout the year in some Jiaozhou Bay waters; and that the silicate deficiency changed the phytoplankton assemblage structure. Analysis of discontinuous 1962 to 1998 nutrient data showed that there was no N or P limitation of phytoplankton growth in that period. The authors consider that the annual cyclic change of silicate limits phytoplankton growth in spring, autumn and winter every year in Jiaozhou Bay; and that in many Jiaozhou Bay waters where the phytoplankton as the predominant species need a great amount of silicate, analysis of the nutrients N or P limitation of phytoplankton growth relying only on the N and P nutrients and DIN:P ratio could yield inaccurate conclusions. The results obtained by applying the rules of absolute and relative limitation fully support this view. The authors consider that the main function of nutrient silicon is to regulate and control the mechanism of the phytoplankton growth process in the ecological system in estuaries, bays and the sea. The authors consider that according to the evolution theory of Darwin, continuous environmental pressure gradually changes the phytoplankton assemblage’s structure and the physiology of diatoms. Diatoms requiring a great deal of silicon either constantly decrease or reduce their requirement for silicon. This will cause a series of huge changes in the ecosystem so that the whole ecosystem requires continuous renewal, change and balancing. Human beings have to reduce marine pollution and enhance the capacity of continental sources to transport silicon to sustain the continuity and stability in the marine ecosystem.

Effect of temperature,salinity and irradiance on growth and photosynthesis of Ulva prolifera

Intensive Pyropia aquaculture in the coast of southwestern Yellow Sea and its subsequent waste, including disposed Ulva prolifera, was speculated to be one of the major sources for the large-scale green tide proceeding in the Yellow Sea since 2007. It was, however, unclear how the detached U. prolifera responded and resumed growing after they detached from its original habitat. In this study, we investigated the growth and photosynthetic response of the detached U. prolifera to various temperature, salinity and irradiance in the laboratory. The photosynthetic rate of the detached U. prolifera was significantly higher at moderate temperature levels（14–27℃）and high salinity（26–32）, with optimum at 23℃ and 32. Both low（14℃） and highest temperature（40℃）, as well as low salinity（8） had adverse effects on the photosynthesis. Compared with the other Ulva species, U. prolifera showed higher saturated irradiance and no significant photoinhibition at high irradiance, indicating the great tolerance of U. prolifera to the high irradiance. The dense branch and complex structure of floating mats could help protect the thalli and reduce photoinhibition in field. Furthermore, temperature exerted a stronger influence on the growth rate of the detached U. prolifera compared to salinity. Overall, the high growth rate of this detached U. prolifera（10.6%–16.7% d^–1） at a wide range of temperature（5–32℃） and salinity（14–32） implied its blooming tendency with fluctuated salinity and temperature during floating. The environmental parameters in the southwestern Yellow Sea at the beginning of green tide were coincident with the optimal conditions for the detached U. prolifera.

Changes of nutrient concentrations and N:P:Si ratios and their possible impacts on the Huanghai Sea ecosystem

To investigate the impacts of nutrient concentrations and N：P：Si ratios on the ecosystem of the Huanghai Sea （Yellow Sea）, the current status and long-term variation of nutrients concentrations and ratios as well as phytoplankton community structure in the Huanghai Sea were collected and analyzed. The results reveal great annual and seasonal fluctuations in the nutrient concentrations and N：P：Si ratios during 1998-2008 with no clear pattern observed in the whole region. Yet on a seasonal scale of spring and in the coastal regions such as the Jiaozhou Bay and Sanggou Bay, the increase of DIN concentration and N：P ratio as well as the decrease of phosphate and sili- cate concentrations and Si：N ratios were relatively significant. Many pelagic ecosystem changes have occurred concurrent with these changes of the nutrient regime, such as the recent increase of primary production, changes of phytoplankton chlorophyll a biomass and abundance, an increase of eutrophication, and occurrence of HABs. In addition, new trends in the variation of nutrients seem to be developing in some particular transect such as 36N, which suggests that long-term and systematic ecosystem monitoring in the Huanghai Sea is necessary.

Heterocapsa bohaiensis sp.nov.(Peridiniales:Dinophyceae):a novel marine dinoflagellate from the Liaodong Bay of Bohai Sea,China

A small armed dinoflagellate bloomed in the aquaculture ponds off the coast of Liaodong Bay, Bohai Sea of China, resulting in heavy mortalities of the cultured prawns （Penaeusjaponicus） and larvae of Chinese mitten handed crabs （Eriocheir sinensis）. The bloom-forming species was successfully isolated, and cellular morphology of the specimen was consequently investigated through light, fluorescent and electron microscopy. The small （（14.4±1.6） μm in length） ellipsoid cells show typical Heterocapsa thecal plate arrangement （Po, cp, 5′, 3a, 7″, 6c, 5s, 5′″, 2″″）. The episome is evidently bigger than the hyposome. One to three spherical pyrenoids are located above or beside the large elongated nucleus. The body scale is characterized by a triangle basal plate with one central upright and nine peripheral spines. Above all, Heterocapsa bohaiensis could be distinguished from other Heterocapsa species by the combination of the cell size, morphology, cellular structure and body scale. Sequence analyses of both ITS and LSU regions reveal the significant genetic divergence between H. bohaiensis and other established species in this genus, further supporting novelty of this species. Noticeably, different sample treatment methods resulted in morphological variation of the apical pore complex （APC） of H. bohaiensis, which needs to be taken into account in future study.

An approach to the age of Huanghe River in shelf regions of Yellow Sea and Bohai Sea

There are two different opinions on the formation history of Huanghe (Yellow) River. One postulates that Huanghe River might have come into existence before Tertiary. The other supposes that it joined up into a long river only in the last stage of Late Pleistocene. The appearance of Huanghe River is believed to have close relation to the uplifting of Tibetan Plateau. It is not likely that it could have come into being before its high elevation riverhead was formed. Today Huanghe River occurred probably during the recession of the sea in glacial periods. In the last glacial age, the climate was very harsh in the area north of the modern estuary of Changjiang (Yangtse) River; some areas were permafrost and the others barren deserts. At that time, eolation was the major exogenic force on exposed shelf. Beginning from 12 Ka BP, the global climate warmed up, resulting in gradual disappearance of continental mountain glaciers retreated, and sea level rose. Consequently, Huanghe River was replenished with water to become modern river system. With continued rising of sea level, Huanghe River delta moved continuously eastward.

Artificial seed germination and seedling production of Zostera marina L.by salinity manipulation

Vast declines in Zostera marina seagrass beds demand effective methods of rehabilitation. In this study, we developed a practical method by reducing salinity to induce seed germination followed with recovering salinity to facilitate seedling production of Z. marina. The results showed that Z. marina seeds collected from natural seawater（salinity 30） were induced to germinate at reduced salinities. Percent germination（GR） was higher and mean-time-to-germinate（MTG） was shorter at lower salinities. The highest GR and shortest MTG occurred at salinity 0（deionized freshwater）. After germination in freshwater, seeds could develop into seedlings at salinities5–30 and continue the growth. Viability or development of germinated seeds was not significantly different during the 40 d of post-germination incubation at salinities 5–15 after 1–20 d of germination in freshwater. However,during the process of translating germinated seeds from salinity 0 and 5 to salinity 30, reducing the gradients of post-germination acclimation facilitated more seeds forming seedlings in less time. On average, after 60 d of static incubation, including 20 d in freshwater for germination followed with immediate shift to salinity 5 and increasing to salinity 30 at increment of 5 every two days until cultivation at constant salinity 30, 33% of Z. marina seeds produced healthy seedlings. The results indicate that the salinity-manipulation based method of artificial germination and seedling production is practical and effective in supporting rehabilitation of Z. marina bed.

Seasonal variability of the zooplankton community in the southwest of the Huanghai Sea (Yellow Sea) Cold Water Mass

Samples were collected with a plankton net in the four seasonal cruises during 2006-2007 to study the seasonal variability of the zooplankton community in the southwest part of Huanghai Sea Cold Water Mass （HSCWM, Yellow Sea Cold Water Mass）. The spatial and temporal variations of zooplankton species composition, biomass, abundance and biodiversity were examined. A total of 122 zooplankton species and 30 pelagic larvae were identified in the four cruises. Calanus sinicus and Aidanosagitta crassa were the most dominant species, and Themisto gaudichaudi and Euphau- sia pacifica were widely distributed in the HSCWM area. The spatial patterns of non-gelatinous zooplankton （removing the high water content groups） were similar to those of the total zooplank- ton biomass in autumn, but different significantly in the other three seasons. The seasonal means of zooplankton biomass in spring and summer were much higher than that in autumn and win- ter. The total zooplankton abundance averaged 283.5 ind./m3 in spring （highest）, 192.5 ind./m3 in summer, 165.5 ind./m3 in autumn and 65.9 ind./m3 in winter （lowest）, and the non-gelatinous groups contributed the most total abundance. Correlation analysis suggests that the non-gelatinous zooplankton biomass and abundance had a significant positive correlation in the whole year, but the relationship was insignificant between the total zooplankton biomass and abundance in spring and summer. The diversity index HI of zooplankton community averaged 1.88 in this study, which was somewhat higher than historical results. Relatively low diversity in summer was related to the high dominance of Calanus sinicus, probably due to the strongest effect of the HSCWM in this season.

Source of propagules of the fouling green macroalgae in the Subei Shoal,China

Since 2007,large-scale green tides dominated by Ulva prolifera consecutively bloomed in the Yellow Sea and caused great economic losses.The fouling U.prolifera on the Pyropia yezoensis aquaculture rafts in the Subei Shoal was regarded as the major source of the floating biomass.However,it was still unclear about the seed source of fouling green macroalgae attached on the rafts.In this study,the field surveys and the indoor experiments were conducted to reveal the source of propagules of the fouling green macroalgae on the rafts and to study the anti-fouling material for P.yezoensis aquaculture rafts which could possibly be a feasible strategy to control the green tides in the Yellow Sea.The results showed that（1） micro-propagules of several green macroalgal species,including U.prolifera,U.linza,U.compressa,U.flexuosa,and Blidingia sp.coexisted in the waters and sediments in the Subei Shoal and their proportion remarkably changed over time;（2） the bamboo poles with peeling treatment could significantly reduce the amount of U.prolifera micro-propagules attached.This study confirmed that the micro-propagules distributed in the Subei Shoal area were the precursors of the green tides,and provided a feasible method to control the Yellow Sea large-scale green tides at the beginning.

Phytoplankton pigment pattern in the subsurface chlorophyll maximum in the South Java coastal upwelling system, Indonesia

Upwelling occurs on the coast of Java between June and October, forced by local alongshore winds associated with the southeasterly monsoon. This causes variations in phytoplankton community composition in the upwelling zone compared with the surrounding offshore area. Based on pigments analysis with subsequent calculations of group contributions to total chlorophyll a(Chl a) using CHEMTAX, we studied the distribution and composition of phytoplankton assemblages in the subsurface chlorophyll maximum along the south coast of Java and the influence of upwelling. Nineteen phytoplankton pigments were identified using high-performance liquid chromatography, and CHEMTAX analysis associated these to ten major phytoplankton groups. The phytoplankton community in the coastal area influenced by upwelling was characterized by high Chl a and fucoxanthin concentrations, indicating the dominance of diatoms. In contrast, in the offshore area, the Chl a and fucoxanthin concentrations declined to very low levels and the community was dominated by haptophytes represented by 19′-Hexanoyloxyfucoxanthin. Accordingly, microphytoplankton was found to be the major size class in the coastal area influenced by upwelling, while nanophytoplankton was most abundant in the offshore area. Low concentrations of other accessory pigments indicated less contribution from dinoflagellates,prasinophytes, chlorophytes and cryptophytes. Photo-pigment indices revealed that photosynthetic carotenoids(PSCs) were the largest component of the pigment pool, exceeding the proportion of Chl a, with the average PSCTP up to 0.62. These distribution trends can mainly be explained by phytoplankton adaption strategies to upwelling and subsurface conditions by changing species composition and adjusting the pigment pool.