Solving the coastal eutrophication problem by large scale seaweed cultivation

Eutrophication is becoming a serious problem in coastal waters in many parts of the world. It induces the phytoplankton blooms including 'Red Tides', followed by heavy economic losses to extensive aquaculture area. Some cultivated seaweeds have very high productivity and could absorb large quantities of N, P, CO2, produce large amount of O-2 and have excellent effect on decreasing eutrophication. The author believes that seaweed cultivation in large scale should be a good solution to the eutrophication problem in coastal waters. To put this idea into practice, four conditions should be fulfilled: (a) Large-scale cultivation could be conducted within the region experiencing eutrophication. (b) Fundamental scientific and technological problems for cultivation should have been solved. (c) Cultivation should not impose any harmful ecological effects. (d) Cultivation must be economically feasible and profitable. In northern China, large-scale cultivation of Laminaria japonica Aresch. has been encouraged for years to balance the negative effects from scallop cultivation. Preliminary research in recent years has shown that Gracilaria lemaneiformis (Bory) Daws. and Porphyra haitanensis Chang et Zheng are the two best candidates for this purpose along the Chinese southeast to southern coast from Fujian to Guangdong, Guangxi and Hong Kong. Gracilaria tenuistipitata var. liui Chang et Xia is promising for use in pond culture condition with shrimps and fish.

Tank cultivation of the red alga Palmaria palmata: Effects of intermittent light on growth rate, yield and growth kinetics

Tank cultivation of marine macroalgae involves air-agitation of the algal biomass and intermittent light conditions, i.e. periodic, short light exposure of the thalli in the range of 10 s at the water surface followed by plunging to low light or darkness at the tank bottom and recirculation back to the surface in the range of 1-2 min. Open questions relate to effects of surface irradiance on growth rate and yield in such tumble cultures and the possibility of chronic photoinhibition in full sunlight. A specially constructed shallow-depth tank combined with a dark tank allowed fast circulation times of approximately 5 s, at a density of 4.2 kg fresh weight (FW) m(-2) s(-1). Growth rate and yield of the red alga Palmaria palmata increased over a wide range of irradiances, with no signs of chronic photoinhibition, up to a growth-saturating irradiance of approximately 1600 mumol m(-2) s(-1) in yellowish light supplied by a sodium high pressure lamp at 16 h light per day. Maximum growth rate ranged at 12% FW d(-1), and maximum yield at 609 g FW m(-2) d(-1). This shows that high growth rates of individual thalli may be reached in a dense tumble culture, if high surface irradiances and short circulation times are supplied. Another aspect of intermittent light relates to possible changes of basic growth kinetics, as compared to continuous light. For this purpose on-line measurements of growth rate were performed with a daily light reduction by 50% in light-dark cycles of 1, 2 or 3 min duration during the daily light period. Growth rates at 10degreesC and 50 mumol photon m(-2) s- 1 dropped in all three intermittent light regimes during both the main light and dark periods and reached with all three periodicities approximately 50% of the control, with no apparent changes in basic growth kinetics, as compared to continuous light.

Comparison of photobioreactors for cultivation of Undaria pinnatifida gametophytes

Undaria pinnatifida gametophytes were grown in 2.5 l bubble column and airlift reactor at 25 degreesC and light intensity of 40 mumol m(-2) s(-1) for 6 days. With aeration at 1 l min(-1), the airlift reactor yielded higher growth rate (0.12 mg DW ml(-1) d(-1)) than a bubble column (0.08 mg DW ml(-1) d(-1)). The advantages were related to the more homogeneous fluid dynamic characteristics of the airlift reactor.

Translocation of assimilates in Undaria and its cultivation in China

Undaria cultivation on a commercial scale began in China only in the last decade. Today, Undaria pinnatifida is the main species under cultivation concentrated in two provinces, Liaoning and Shandong. The annual production in the early nineties was 8000-13 000 tons dry weight, which is two or three times the pre-1980 figures. The raft cultivation method maintaining the alga at the desired depths generally ensures the light saturated rate of photosynthesis on clear days, and enhances production. Under the cultivated condition, the calculated annual primary productivity of this alga is 160 g C m(-2) y(-1). Translocation of C-14-labelled photoassimilates in rapidly growing sporophyte of Undaria pinnatifida was studied in the open sea. Samples from different parts of the blade with counterparts exposed to tracer ((NaHCO3)-C-14) showed that the translocation that occurred mainly from the tip of the blade to the growing region had obvious source-sink relationship. It took 20 minutes to translocate the labelled photoassimilates from the epidermis, via cortex, to the medulla of the midrib, where rates of translocation averaging 42-48 cm h(-1) were observed in the open sea. Production experiments of tip-cutting of the blades showed an increased production of 9%.

Integrated cultivation of the red alga Kappaphycus alvarezii and the pearl oyster Pinctada martensi

The effect of simultaneously cultivating the pearl oyster Pinctada martensi and the red alga Kappaphycus alvarezii on growth rates of both species was investigated in laboratory and field studies conducted from December 1993 to June 1995. The two study sites were in subtidal areas 100 km apart off the east coast of Hainan Island, China. Pearl oysters were cultivated in the center of an algal farm and red alga was cultivated in the center of the pearl oyster farm. These field experiments showed higher growth rates of both P. martensi and K. alvarezii in a co-culture system than in a monospecies culture system. Laboratory studies showed that the algae removed nitrogenous wastes released by pearl oysters. Algae treated with pearl oyster wastes grew much faster than those without oyster wastes. Algae treated with the seawater to which NH4Cl, NaNO3 and NaNO2 were added grew at the same rate as those treated with natural seawater containing oyster nitrogenous wastes, suggesting that enhanced growth of algae in the co-culture system was largely due to nitrogenous metabolites of the pearl oysters. In the co-culture, growth of pearl oysters was positively influenced by the presence of rapidly growing algae but when seawater temperature decreased below 20 degrees C, the algae grew slowly and there was no measurable benefit of mixed culture to either algae or pearl oyster.

Cultivation of the brown alga Hizikia fusiformis (Harvey) Okamura: stress resistance of artificially raised young seedlings revealed by chlorophyll fluorescence measurement

Commercial farming of the intertidal brown alga Hizikia fusiformis (Harvey) Okamura in China and South Korea in the sea depends on three sources of seedlings: holdfast-derived regenerated seedlings, young plants from wild population and zygote-derived seedlings. Like many successfully farmed seaweed species, the sustainable development of Hizikia farming will rely on a stable supply of artificial seedlings via sexual reproduction under controlled conditions. However, the high rate of detachment of seedlings after transfer to open sea is one of the main obstacles, and has limited large-scale application of zygote-derived seedlings. To seek the optimal condition for growing seedlings on substratum in land-based tanks for avoidance of detachment in this investigation, young seedlings were grown in both outdoor tanks exposed directly to sunlight and in indoor raceway tanks in reduced, filtered sunlight. Results showed that young seedlings, immediately after fertilization, could withstand a daily fluctuation of direct solar irradiance up to a level of 1800 mu mol photons m(-1)s(-1), and maintained a faster growth rate than seedlings grown in indoor tanks. Detailed experiments by use of chlorophyll fluorescence measurements further demonstrated that the overnight (12 h) recovery of optimal fluorescence quantum yield (F-v/F-m) of seedlings after 1 h treatment at 40 degrees C was 98%, and the 48 h recovery of F-v/F-m of seedlings after 1 h exposure to 1800 mu mol m(-2)s(-1) was 92%. Forty-one-day-old seedlings showed no significant decrease of optimal fluorescence quantum yield at salinity ranging from 30 to 5 ppt for a treatment up to 17 h. Six-hour desiccation treatment did not have any influence on the optimal fluorescence quantum yield. Exposure to 18 mmol L-1 sodium hypochlorite for 10 min did not damage the PSII efficiency, and thus could be used to remove epiphytic algae. The strong tolerance of young seedlings to high temperature, high irradiance, low salinity and desiccation found in this investigation supports the view that mass production of Hizikia seedlings should be performed in ambient light and temperature instead of in shaded greenhouse tanks.

Characterization of the life history of Bangia fuscopurpurea (Bangiaceae, Rhodophyta) in connection with its cultivation in China

Bangia fuscopurpurea (Rhodophyta) was cultivated in Putian (Fujian province, China). The characteristics of the life history concerned with cultivation were investigated and the cultivation procedure was presented. The gametophytic phase (thallus) and the sporophytic phase (conchocelis) occurred alternately in the life history of B. fuscopurpurea. Young thalli produced archeospores, and the number depended on the environmental factors. Temperature affected the number of archeospore release and percent of germination, and photo flux density (PFD) mainly affected the time of spore release and germination. Thalli matured from December to February and developed into the conchocelis phase through sexual reproduction. The conchocelis grown in shells had three developmental stages: vegetative conchocelis, conchosporangiall formation and conchospore formation. Pit-connections were present in the first 2 stages but absent after conchospore formation. Vegetative conchocelis and conchosporangial. branches can transform into each other. However, conchospores only developed into the gametophytic phase. Cultivation of B. fuscopurpurea was based on characterization of the life history, consisting of 3 steps: zygotospores collection, indoor cultivation of conchocelis and outdoor cultivation of thalli. Young thalli that developed from conchospores produced numerous archeospores before December. Over 90% of the crop was from the development of archeospores. The results indicated that conchosporelings were a good source of archeospores, and the development of the large quantity of archeospores acted as a more prevailing means to increase the population size. (C) 2008 Elsevier B.V. All rights reserved.

Early development of Costaria costata (C. Agardh) Saunders and cultivation trials

Costaria costata (C. Agardh) Saunders is one of common kelps distributed in many coastal areas worldwide; however, in China, no reports have been made on cultivation of the genus. To investigate potential cultivation of the species in the northern part of China, trials on isolation and preservation of the gametophytes were conducted using C. costata from Korea; growth and development of the gametophytes were observed. We showed that at 10 +/- 1A degrees C, 60 mu mol m(-2)s(-1) and 12:12 h (L:D), freshly released zoospores settled down within 1 hour, and then developed into the primary cell during the following 2 days. After a vegetative growth phase lasting 6-8 days, female gametophytes became 3-4 times larger in diameter than that of the primary cell, but still remained at a unicellular stage, while male gametophytes divided into 4-10 cells with only a slight change in size. Fertilization occurred within 10 days after the zoospores were released from the sporangia, and the apical and basal tissues of the juvenile sporophyte divided and differentiated into the blade and stipe. Temperature and irradiance influenced gametophytic vegetative growth and developmental patterns. Generally, low irradiance (15 mu mol m(-2)s(-1) and 30 mu mol m(-2)s(-1)) was unfavorable to the induction of fertility, but it enhanced female gametophyte division. The optimal conditions for vegetative growth were 15A degrees C and 30 mu mol m(-2)s(-1). After transplantation of the juvenile seedlings and after eight months cultivation, the harvested mature blade reached 194 cm in length and 32.7 cm in width. Our study proves that it is feasible to implement propagation and large scale cultivation of C. costata in northern China.

Rapid optimization of process conditions for cultivation of transgenic Laminaria japonica gametophyte cells in a stirred-tank bioreactor

Batch cultivation for transgenic kelp gametophyte cells was investigated in an online controlled 5 L stirred-tank photo-bioreactor to rapidly optimize the process conditions by monitoring the rate of increase of pH. The transgenic kelp gametophytes with heterologous gene encoding hepatitis B surface antigen (HBsAg) could rapidly grow in the bioreactor. Optimal temperature and agitation rate for bioreactor cultivation of gametophytes were 15 degrees C and 200 rpm. Optimal incident light intensities depended on the initial cell densities. (c) 2006 Elsevier B.V. All fights reserved.

Cultivation of the brown alga Hizikia fusiformis (Harvey) Okamura: controlled fertilization and early development of seedlings in raceway tanks in ambient light and temperature

Commercial cultivation of the dioecious brown macroalga Hizikia fusiformis (Harvey) Okamura in East Asia depends on the supply of young seedlings from regenerated holdfasts or from wild population. Recent development of synchronized release of male and female gametes in tumble culture provides a possibility of mass production of young seedlings via sexual reproduction. In this paper, we demonstrate that controlled fertilization can be efficiently realized in ambient light and temperature in a specially designed raceway tank in which the sperm-containing water has been recirculated. The effective fertilization time of eggs by sperm was found to be within six hours. Fast growth and development of the young seedlings relied on the presence of water currents. Velocity tests demonstrated that young seedlings of 2-3 mm in length could withstand a water current of 190 cm s(-1) stop without detachment. Culture experiments at 24 h postfertilization showed that elongation of both the seedlings and their rhizoids were not hampered by high irradiance up to 600 mu mol photons m(-2) stop s(-1) stop. However, growth was slightly retarded if cultured at a temperature of 16 degrees C compared to other culture temperatures of 22, 25 and 29 degrees C. No seedling detachment was observed after transfer of the young seedlings to raft cultivation in the sea after one and 1.5 months post-fertilization, indicating the feasibility of obtaining large quantity of seedlings in such a system.

Tank cultivation of the red alga Palmaria palmata: Year-round induction of tetrasporangia, tetraspore release in darkness and mass cultivation of vegetative thalli

Field-collected tetrasporophytes of Palmaria palmata were tumbled in 300-L outdoor tanks from January to August at ambient daylength or in a constant short-day (SD) regime (8 h light per day), both at 10 or 15 degrees C. Tetrasporangia were massively induced after 2.5 months under SD conditions at 10 degrees C and completely lacking at 15 degrees C, both under SD or ambient daylength conditions, with a few tetrasporangia present at 10 degrees C and ambient daylength. Elongation rates of tagged tetrasporophytic thalli peaked from March to April in all four conditions, when the biomass densities in the outdoor tanks were close to 2.5 kg fresh weight m(-2). Under all four conditions, juvenile proliferations started to appear in June from the margins of the old fronds, and attained approximately 1 cm in length by the end of July. Approximately 80% of the tetraspores were released during the first three dark phases in a light/dark regime, and the remaining 20% during the light phases. A minimum of 10 min darkness was observed to trigger spore release. White light inhibited tetraspore release, while a similar number of spores were released in continuous red light or in the light/dark regime, although with no significant differences of spore release during subjective days and nights. Sporelings were successfully derived from the released tetraspores for mass propagation of the male gametophyte in 2000-L outdoor tanks in a greenhouse. Mass production of male gametophytic sporelings of P. palmata was completed two times by SD induction of tetrasporangia at 10 degrees C, release of spores in darkness and culturing the sporelings until they were ready to be propagated vegetatively in greenhouse tanks. One experiment lasted from January to October 2001, with spore release in June, and the second from September to April 2003, with spore release in January. These results may support the development of sustainable, year-round Palmaria farming. (c) 2005 Elsevier B.V. All rights reserved.

Growth of Gracilaria lemaneiformis under different cultivation conditions and its effects on nutrient removal in Chinese coastal waters

Gracilaria lemaneiformis (Bory) Daws has been extensively cultivated as a source of commercial agar and the ecomaterials in Shenao Bay, Guangdong Province, Jiaozhou Bay, Shandong Province and other waters in China. This paper examines the in situ suspended farming of G. lemaneiformis using raft cultivation under different conditions and its effects on nutrient removal in the laboratory. The results showed that cultivated Gracilaria grew well in both Shenao Bay and Jiaozhou Bay. The biomass of Gracilaria increased from 50 to 775 g m(-1) (fresh weight) during 28 days, with special growth rate (SPG) 13.9% d(-1) under horizontal cultivation in Jiaozhou Bay. Light, temperature, nutrient supply, as well as cultivation treatments such as initial density, and depth of suspension seaweed were important to the growth of Gracilaria. The highest biomass production was observed in the horizontal culture condition (0.0 m) and 0.5-1.5 m deep layer in Jiaozhou Bay. However, the highest growth rate in Shenao Bay appeared under the lowest initial stocking density treatment. In the laboratory, the aquarium experiments (fish and seaweed culture systems) demonstrated that Gracilaria was able to remove inorganic nutrients effectively. The concentration of NH4+-N decreased by 85.53% and 69.45%, and the concentration of PO4-P decreased 65.97% and 26.74% in aquaria with Gracilaria after 23 days and 40 days, respectively. The results indicate that Gracilaria has the potential to remove excess nutrient from coastal areas, and the large-scale cultivation of G. lemaneiformis could be effective to control eutrophication in Chinese coastal waters. (c) 2005 Elsevier B.V. All rights reserved.

Optimization of conditions for cell cultivation of Porphyra haitanensis conchocelis in a bubble-column bioreactor

Process conditions for cell cultures derived from conchocelis of female red macroalga Porphyra haitanensis were optimized in an illuminated 0.3-l bubble-column photobioreactor, using CO2 in air as the sole carbon source during a 20-day cultivation period. It reached the highest growth rate when the initial cell density was 700 mg l(-1)(dry weight), the optional aeration rate was 1.2 v/v/min, inorganic nitrate concentration was 15 mM and inorganic phosphate concentration was 0.6 mM. This is the first reported bioreactor cultivation study of cell cultures derived from conchocelis of Porphyra haitanensis.

Optimal light regime for the cultivation of transgenic Laminaria japonica gametophytes in a bubble-column bioreactor

Fluctuating light intensity had a more significant impact on growth of gametophytes of transgenic Laminaria japonica in a 2500 ml bubble-column bioreactor than constant light intensity. A fluctuating light intensity between 10 and 110 mu E m(-2) s(-1), with a photoperiod of 14 h:10 h light:dark, was the best regime for growth giving 1430 mg biomass l(-1).