Biological activity of a red-tide alga--A. tamarense under co-cultured condition with bacteria.

The relationship between Alexandrium tamarense (Lebour) Balech, one of red-tide alga, and two strains of marine bacteria, Bacillius megaterium (S7) and B. halmapulus (S10) isolated from Xiamen Western Sea, was investigated by evaluating the growth state of A. tamarense and the variation of beta-glucosidase activity in co-culture system. The results showed the growth and multiplication of the alga were related with the concentration, genus speciality of the bacteria, and growth stage of the alga itself. The growth of A. tamarense was obviously inhibited by S7 and S10 at high concentration. Either inhibition or promotion contributed much more clearly in earlier than in later stage of the growth of the alga. Furthermore, there was a roughly similar variation trend of the activity of extra-cellular enzyme, beta-glucosidase, in the water of the separately co-cultured bacteria S7 and S10 with the alga. The beta-glucosidase activity (beta-GlcA) rapidly increased during the later algal growth accompanying the increase of the lysis of the alga cells. The obvious inhibition of A. tamarense by marine bacteria at high concentration and evident increase of beta-GlcA in co-colture system would help us in better understanding the relationship between red-tide alga and bacteria, and also enlightenedus the possible use of bacteria in the bio-control of red-tide.

[Phytoplankton pigment patterns and community structure in the Yangtze Estuary and its adjacent areas].

Three cruises were carried out in the Yangtze Estuary and its adjacent areas in May, November, June during 2009-2010. The spatial variations of phytoplankton community structure were investigated based on RP-HPLC analysis of pigments and CHEMTAX processing of the pigment data. 21 kinds of pigments were detected, among which chlorophyll a, peridinin, fucoxanthin, 19'-butanoyloxyfucoxanthin, 19'-hexanoyloxyfucoxanthin, chlorophyll b, diadinoxanthin, alloxanthin and zeaxanthin were the major pigments in the Yangtze Estuary and its adjacent areas. Chlorophyll a was the most abundant in all pigments, followed by fuxoxanthin. Other pigments generally contributed a minor proportion to the total pigments. High concentrations of fucoxanthin and peridinin were observed in May 2009 and June 2010, indicating blooms of diatoms and dinoflagellates. The results showed that the composition and distribution of phytoplankton pigments were influenced by environmental factors. The phytoplankton community, as determined by biomarker pigment concentration using HPLC and CHEMTAX, was composed mainly of diatoms, dinoflagellates, cryptophytes, chlorophytes, cyanobacteria, prymnesiophytes, chrysophytes and prasinophytes. The dominant algal groups were diatoms, dinoflagellates and chlorophytes in May 2009. The phytoplankton community was characterized by high contribution of diatoms in November 2009. Diatoms, dinoflagellates and cryptophytes accounted for 62.5% of chlorophyll a in June 2010, and the relative abundance of cyanobacteria was higher in this cruise. The spatial variations of phytoplankton community structure featured distinct regionality. Diatoms, chlorophytes and cryptophytes were the main groups in the inshore waters, and the abundances of prymnesiophytes, chrysophytes and cyanobacteria were increasing from inshore to the open sea.

[Removal of Heterosigma akashiwo by modified wheat straw].

The modified wheat straw (MWS) was prepared and used to investigate the removal and the mechanism of Heterosigma akashiwo. The results showed that under the same loading of 0.10 g/L, the algal removal efficiency could reach 80% by MWS in 120 minutes, while 10% by the unmodified wheat straw. To investigate the mechanism, we measured the optical density of the supernatant at 260 nm. The result showed that the nucleotides were released, which meant disruption of the cytoplasmic membrane. More than 15% of the nucleotides were released from the cytoplasm under the effect of 0.15 g/L of MWS, indicating the irreversible damage on the cellular membrane, which resulted in the disintegration of the harmful algal cells. It is suggested that the low concentration of MWS might adsorb onto the algal cell surface and bind to the cytoplasmic membrane, which resulted in the flocculation. While the high concentration might cause the penetration into the cellular membrane, which resulted in the leakage of cytoplasm material and hence the death of cell.

[Effects of different phosphorus substrates on the growth and phosphatase activity of Skeletonema costatum and Prorocentrum donghaiense].

The effects NaH2PO4, adenosine disodium triphosphate (ATP), glucose 6-phosphate (G-6-P) and sodium beta-glycerophosphate (G-P) on the growth and phosphatase activity of Skeletonema costatum and Prorocentrum donghaiense were studied. The results showed that both species could utilize both dissolved inorganic phosphate (DIP) and dissolved organic phosphorus (DOP), and DOP had more effects on the growth of two species than DIP. For S. costatum, after 8 days, the cell abundances of the four treatments (NaH2PO4, ATP, G-6-P and G-P) were 48 x 10(4), 73 x 10(4), 63 x 10(4) and 54 x 10(4) cells/mL, respectively; For P. donghaiense, after 10 days, the cell abundances of the four treatments were 8.7 x 10(4), 15.5 x 10(4), 12.4 x 10(4) and 9.5 x 10(4) cells/mL, respectively. On the first 3-4 days, the phosphatase activity of all treatments of the two species showed a decreasing trend, but different changes were observed for the different phosphorus substrate treatments in latter days. For the NaH2PO4 treatment, both the AP and AcP activity of two species increased from the fifth day onwards. For S. costatum, the AP activity of the ATP and G-6-P treatment groups showed no obvious changes and AcP activity had a slight increase from the fifth day to the eighth day, while the activity of G-P treatment had highest phosphatase activity which increased from the fifth day on. At the end of the experiment, the AP activity of the three DOP treatment groups (ATP, G-6-P and G-P) was 0.004 x 10(-5), 0.014 x 10(-5) and 0.029 x 10(-5) U/cell, respectively, and the AcP activity was 0.006 x 10(-5), 0.011 x 10(-5) and 0.018 x 10(-5) U/cell, respectively. For P. donghaiense, both the AP and AcP activity of the three DOP treatments had similar trends, i.e., ATP < G-6-P < G-P. Under the same nutrient conditions, S. costatum had a much higher phosphatase activity and could absorb P from the environment much faster than P. donghaiense.

[Comparative research on the effects of different nutrient concentrations on the photopigment content and photosynthesis of two bloom-forming species isolated from the Changjiang River estuary].

The contents of cellular chlorophyll a (Chl-a), chlorophyll c (Chl-c), total coloured carotenoids (TCC) and the photosynthesis of Skeletonema costatum and Prorocentrum donghaiense under different nutrient conditions were studied. The results showed that both species in the low nutrient concentration conditions had lower cellular Chl-a, Chl-c and TCC content than those in the high nutrient concentration conditions. When the initial N/P ratio was 16/1 while the concentrations were different, the two species had different photosynthetic rate responses. For S. costatum, the photosynthetic rate normalized by cell in the low nutrient concentration group (64 micromol/L N and 4 micromol/L P) was significantly lower than that in the high concentration group (256 micromol/L N and 16 micromol/L P) from the fifth day, and at the end of the experiment (on the seventh day), the photosynthetic rate was 0.031 x 10(-4) micromol x (cell x h)(-1) and 0.13 x 10(-4) micromol x (cell x h)(-1) respectively, while the photosynthetic rate normalized by Chl-a was 12.92 micromol x (microg x h)(-1) and 13.03 micromol x (microg x h)(-1) for the two groups respectively, and there was no significant difference between them; however, for P. donghaiense, the photosynthetic rates normalized by both cell and Chl-a in the low concentration conditions (64 micromol/L N and 4 micromol/L P) were significantly higher than those in the high concentration conditions (256 micromol/L N and 16 micromol/L P). For the two species, when P was sufficient, the low N concentration group (64 micromol/L N and 36 micromol/L P) and when N was sufficient, the low P concentration group (883 micromol/L N and 4 micromol/L P) had higher photosynthetic rates normalized by both cell and Chl-a than the high N concentration group (256 micromol/L N and 36 micromol/L P) and the high P concentration group (883 micromol/L N and 16 micromol/L P) respectively. There was a significant positive relationship between the photosynthetic rate and the intracellular P for both species, and P. donghaiense had higher cellular photopigment contents and photosynthetic rates than S. costatum under the same nutrient conditions. It could be inferred from their photosynthetic characteristics that P. donghaiense would survive better in low nutrient conditions compared with S. costatum.

[Inhibitory effect of Gracilaria lemaneformis (Bory) Weber Bosse on the co-cultured Scrippsiella trochoidea (Stein) Loeblich III under controlled laboratory conditions].

The inhibitory effects of Grcilaria lemaneiformis on the co-cultured Scrippsiella trochoidea were determined under controlled laboratory conditions, and the possible mechanism was studied. Results showed that: (1) in the separating S. trochoiea-G. lemaneormis co-culture system when the initial cell density of C. lemaneaonis was set at 0.5 g x L(-1), the growth of S. trochoidea was obviously inhibited and its maximum cell density and exponential phase were decreased compared with the control; however, the inhibitory effect was not as strong as that in the direct cell-cell contact co-culture. Result showed that allelopathy basing on the direct cell contact was the most possible reason leading to the observed result; (2) when the initial cell density of G. lemaneiformis was set at 0.2 g'L-' in the direct cell-cell contact co-culture, the intracellular nitrate concentration of S. trochoidea in monoculture system was 1.5 times of that in co-culture. It seemed that G. lemaneiformis could competitively absorb the environmental nitrate and ultimately led to the decrease of the stock of intracellular nitrate of S. trochoidea.

[Application of principal component analysis (PCA) for the estimation of source of heavy metal contamination in marine sediments].

Concentrations of heavy metals and organic matter in the bottom sediments of Jiaozhou Bay were determined and the average enrichment factors (AEFs) were used simultaneously to evaluate the extent of metal enrichment-contamination. Results show that heavy metal contamination in this bay could be divided into three groups: negligible to low contamination (AEFs < 2), which is the case of Zn (AEF = 1.11), Pb (AEF = 1.15), Cr (AEF = 1.52), Mn (AEF = 0.80) and Fe (AEF = 0.45); moderate contamination (AEFs = 2 - 3), which is the case of Cu (AEF = 2.79) and Cd (AEF = 2.52); certain to severe contamination (AEFs > 3), As (AEF = 3.03) and Hg (AEF = 8.08) being included in this group. Principal component analysis (PCA) was applied to estimate the sources of heavy metal contamination. Results that the first three components accounted for 52.61%, 17.37% and 15.60% of the total variance respectively exhibited that industrial wastewater, degradation of organic matter and erosion of rocks were the main sources of heavy metal contamination. The Q-analysis of PCA indicated that 14 stations could be divided into five groups. This result not only reflected the pollution characteristic of surface sediments, but also provided fundamental evidences for the putative analysis that industrial discharge is the main source of heavy metal contamination in Jiaozhou Bay.

[Extinguishment of harmful algae by organo-clay modified by alkyl glucoside quaternary ammonium compound].

Systematic study of the sorption behavior of alkyl glucoside quaternary ammonium compound (AGQAC) on kaolin and bentonite showed that the isotherms of its sorption can be described very well by the Langmuir isotherm. The rate of alkyl glucoside quaternary ammonium compound sorption on kaolin and bentonite was very fast, it could reach equilibration in one or two minutes, and its saturate sorption amount was much enough to be used to modify clays. Then the influence of alkyl glucoside quaternary ammonium compound on the growth of Prorocentrum donghaiense, Amphidinium carterae, Scrippsiella trochoidea were studied, it was found that when its concentration was below 0.4 mg/L, 0.5 mg/L, 0.8 mg/L it just restrained the growth of the algae, but when the concentration was above 0.6 mg/L, 0.75 mg/L, 1.2 mg/L it could cumber the algae's growth and even made them die after three days. When it was used combined with clays the concentration below 5 mg/L could enhance the algal removal efficiency of 50 mg/L clay from about 20% to above 90%, so it could decrease the concentration of crude clays in removing algal blooms. Meanwhile, the kinetics of red tide organism coagulation with clay was studied, the effects of different kinds and concentrations of clays, the second component added in clays were examined. Results showed that adding the second component in clay was the most efficient method to improve the algal removal efficiency.

[Effects of Ulva pertusa and Gracilaria lemaneiformis on growth of Heterosigma akashiwo (Raphidophyceae) in co-culture].

We studied the effects of fresh tissue and culture medium filtrate of two species of macroalgae, Ulva pertusa (Chlorophyta) and Gracilaria lemaneiformis (Rhodophyta) on growth of Heterosigma akashiwo (Raphidophyceae) in co-culture. Both U. pertusa and G. lemaneiformis, and especially their fresh tissues, significantly impede the growth of H. akashiwo. Carbonate limitations and the presence of environment bacteria are not necessary for the negative effects of macroalgal on H. akashiwo. The simultaneous nutrient assays show that nitrate and phosphate are almost exhausted in the G. lemaneiformis co-culture system, but remain at acceptable levels in the U. pertusa system, when all cells of H. akashiwo are completely dead. When f/2 medium is supplied daily to G. lemaneiformis culture, the growth of H. akashiwo is greatly inhibited but not completely terminated. Furthermore, different amounts of fresh seaweed tissue, and culture medium filtrate prepared from different macroalgal concentrations are analyzed to determine their effects on the growth of H. akashiwo. The results show a positive correlation between the initial macroalgal concentration and the negative effects they exert on the co-cultured microalgae. Results suggest that the allelopathic effects of U. pertusa may be essential for negative effects on H. akashiwo; however, the combined roles of allelopathy and nutrient competition may be responsible for the negative effect of G. lemaneiformis the release of allelochemicals by U. pertusa.

[Effects of macroalgae on growth of 2 species of bloom microalgae and interactions between these microalgae in laboratory culture].

We studied the effects of fresh tissue and culture medium filtrate of Ulva pertusa (Chlorophyta) and Gracilaria lemaneiformis (Rhodophyta) on growth of 2 causative bloom species: Prorocentrum donghaiense and Alexandum tamarense, in laboratory conditions. Both U. pertusa and G. lemaneiformis, especially their fresh tissues, significantly interfered with the growth of the co-cultured microalgae. P. donghaiense could be completely killed in the bialgal culture, but growth of A. tamarense in it was little affected. Simultaneous assay on the effects of culture medium filtrates showed that the culture filtrate of A. tamarense had algicidal effect on P. donghaiense, while that of P. donghaiense had little effect on growth of A. tamarense. We simulated the interactions between P. donghaiense and A. tamarense in the bialgal culture by using a mathematical model. Results show that the effect of P. donghaiense inhibited by A. tamarense is about 17 times larger than the inhibitory effect of P. donghaiense exerted on A. tamarense. The joint effects of multialgal cultures on microalga were analyzed. Results present that the multialgal cultures of either U. pertusa or G. lemaneiformis on P. donghaiense are synergism, and the joint effect of U. pertusa and P. donghaiense on A. tamarense is additional. However, it was difficult to determine the joint effects of G. lemaneiformis and P. donghaiense on A. tamarense. Results suggest that allelopathy is the most likely reason responsible for the results obtained in this paper.

[Mechanisms of removing red tide organisms by organo-clays].

We tested the influence of the preparation conditions of the quaternary ammonium compounds (QACs) modified clays on their capacities to remove red tide organisms, then discussed the mechanisms of the organo-clays removing red tide organisms. Hexadecyltrimethylammonium (HDTMA) improved the capacity of clays to flocculate red tide algae, and the HDTMA in metastable state enhanced the toxicity of the clay complexes to algae. The capacities of the organo-clays correlated with the toxicity and the adsorbed amount of the QACs used in clays modification, but as the incubation time was prolonged the stability of the organo-clays was improved and the algal removal efficiencies of the clay complexes decreased. When the adsorbed HDTMA was arranged in different clays in which the spatial resistance was different, there was more HDTMA in metastable state in the three-layer montmorillonite. Because of the homo-ion effect the bivalent or trivalent metal ions induced more HDTMA in metastable state and the corresponding organo-clays had high capacities to remove red tide organisms. When the reaction temperature was 60 degrees C the adsorbed HDTMA was easily arranged on cation exchange sites, if the temperature rose or fell the metastable HDTMA would increase so that the capacity of the clays was improved.

[Matrix-bound phosphine (PH3) distribution characteristics in the sediments of Jiaozhou Bay, China].

The distribution of matrix-bound phosphine in sediments was investigated in some selective sea areas of Jiaozhou Bay on Sep.6, 2003. Results show that the peak concentration of phosphine reachs to 143.75 ng/kg (dry weight). Moreover, an obvious regularity of distribution is observed that phosphine concentration in coastal sediments is higher than that in offshore's, and concentration within the Bay is higher than that of outside Bay. Results also reveal that phosphine concentration in such seriously polluted areas as culture farm and estuary is significantly higher than that in other investigated places. On the other hand, the relationship between phosphine and its sedimentary environment suggest that the phosphine concentration and distribution are mainly affected by the organic phosphorous, the redox potential and the sediment composition.

[Removal efficiency of red tide organisms by modified clay and its impacts on cultured organisms].

Removal efficiencies of Prorocentrum donghaiense (Prorocentrum dentatum) by Hexadecyltrimethylammonium (HDTMA) bromide and organo-clay modified by HDTMA were identified. Moreover the toxicity of the unbound HDTMA and HDTMA plus clay to aquacultural organisms, Penaeus japonicus, was also tested. The results suggested that (1) The unbound HDTMA had an excellent ability to remove the red tide organisms. However, its strong toxicity to Penaeus japonicus would restrict its practical use in red tide control. (2) The toxicity of HDTMA could be remarkably decreased by addition of clay and the organo-clay complex had a good ability to removal red tide organisms. At the same time the availability of organo-clay to remove the red tide of P. donghaiense and Heterosigma akashiwo in the lab-imitated cultures were studied. The results indicated that the organo-clay complex could remove 100% P. donghaiense at the dosage of 0.03 g/L and effectively control H. akashiwo at 0.09 g/L while the survival rate of Penaeus japonicus larvae, which were cultured in the red tide seawater, is kept 100%. According to the results in laboratory, the mesocosm tests (CEPEX) in East China Sea were conducted in April and May of 2003. The removal efficiencies of original clay, organic clay and inorganic clay were compared during the CEPEX tests. The results revealed that both inorganic clay and organic clay could remove red tide organisms more effectively than the original clay.