The coast of Jiangsu Province in China – where the densely-branched, oxygen-filled, free-floating filamentous green seaweed, Ulva prolifera, has always been firstly spotted before developing into large scale green tides over the past six years – is uniquely characterized by a huge intertidal radial mudflat. A scientific research team  (URL: www.mbccc.ac.cn) of Institute of Oceanology, Chinese Academy of Sciences (IOCAS) conducted field and laboratory investigations during 2009-2012 to clarify why U. prolifera starts to float and accumulate there in massive amounts.

New results from this team show that: (1) the microscopic propagules of U. prolifera have been consistently present in seawater and the sediments of this mudflat and varied with locations and seasons, and their abundance did not change much over a 3-month testing period at low temperature and in darkness; (2) over 50 000 tons of fermented chicken manure have been applied annually from March to May in coastal animal aquaculture ponds and thereafter the waste water has been discharged into the radial mudflat intensifying the existed eutrophication; (3) elevated levels of temperature, irradiance as well as nutrients in seawater greatly facilitated recovery and growth of propagules, and filaments of the branched U. prolifera were quickly filled with oxygen and floated within an hour; and (4) free-floating U. prolifera could be stranded in any floating infrastructures in coastal waters including large scale Porphyra farming rafts.

Results obtained in this investigation indicate that the bloom-forming alga U. prolifera was nurtured in early spring on this uniquely structured large intertidal mudflat of Jiangsu which has received feeding pulses of nutrients released from the coastal animal aquaculture ponds as well as from the effluents of adjacent rivers. For a truly integrated management of the coastal zone, reduction in nutrient inputs, and control of the effluents of the coastal pond systems, are needed to control eutrophication and prevent green tides in the Yellow Sea in the future.

These results were published in Marine Environmental Research on 15 Feb. 2012 and 12 Nov. 2012, respectively. Dr. Liu Feng of IOCAS was the first author who has conducted this investigation for 5 years and Professor Pang Shaojun was the corresponding author. This investigation is financially supported by Qingdao Municipal Science and Technology Commission, a project from Science and Technology Commission of Qingdao Shinan District, and a project from Qingdao National Oceanographic Center.

Please visit the following webpage links for more information:
http://dx.doi.org/10.1016/j.marenvres.2011.12.004
http://dx.doi.org/10.1016/j.marenvres.2012.10.007

Publications:
(1) Liu Feng, Pang SJ, Chopin T, Gao S, Shan T, Zhao XB, Li J (2012a) Understanding the recurrent large-scale green tide in the Yellow Sea: temporal and spatial correlations between multiple geographical, aquacultural and biological factors. Marine Environmental Research doi: 10.1016/j.marenvres.2012.10.007.
(2) Liu Feng, Pang SJ, Zhao XB, Hu CM (2012b) Quantitative, molecular and growth analyses of Ulva microscopic propagules in the coastal sediment of Jiangsu province where green tides initially occurred. Marine Environmental Research 74:56-63.

Figure 1. Ulva prolifera thalli and phylogenetic tree (Liu et al. 2012a,b)

　　Figure 2. The green algal biomass and phylogenetic tree (Liu et al. 2012a,b)