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CHAPTER II Asterisk * 1 symbolizes significant differences between siphoning and the FTT. Asterisk * 2 on the top of the horizontal bar symbolizes differences between ‘pre-screening’ and ‘no pre-screening’ independently from the filling technique used (therefore compare bars under the horizontal bar for both filling treatments in A and B, C and D). Error bars correspond to one standard deviation. In the two-factorial ANOVA pooled abundances of the five most abundant ciliates showed significantly lower cell concentrations after siphoning (F 1,8 = 6.685, p = 0.03) and pre-screening (F 1,8 = 16.508, p = 0.004) as compared to the FTT and no screening, respectively (Figure 3A+B, Table 3), leading in both cases to significant changes in diversity. The Margalef index ‘d’ (Table 3, Figure 3 C+D) showed no difference at the community level (data not shown) but was significantly lower for the five most abundant ciliate species when ‘no pre-screening’ took place (F 1,8 = 19.0, p = 0.002). Similar to Experiment 1, the Margalef index ‘d’ was also lower for the FTT (F 1,8 = 7.4, p = 0.026, Table 3). No significant treatment interactions were observed for either abundances or Margalef index. At the species level our results could be ascribed to the two dominant ciliates. Lohmanniella oviformis, showed a significant cell loss (17%, F 1,8 = 14.173, p = 0.006) after siphoning as well as after pre-screening (loss: 13%, F 1,8 = 7.471, p = 0.026). For Strombidium cf. tressum no significant difference between both filling treatments was found but pre-screening resulted in a significant loss of cells (up to 51% cell loss, F 1,8 = 56.3325, p = 0.00007). The interaction of both filling methods and pre-screening showed a significant negative effect (F 1,8 = 6.4228, p = 0.035) on S. cf. tressum with a stronger reduction in cell numbers when the combination of the FTT and pre-screening was used. The other three important ciliate species (Strombidium cf. epidemum, Balanion comatum and Myrionecta rubra ‘small’) were not significantly affected by any treatment. With a mean concentration of ~1.3 µg L -1 the chlorophyll a content was approximately 10-fold higher in Experiment 2 compared to Experiment 1. However, the differences between the treatments were not as clear as in Experiment 1. Dinoflagellates The four most abundant dinoflagellate categories were considered for analyses: Athecate dinoflagellates ‘intermediate’ (25-40 µm length), Gyrodinium sp. ‘intermediate’ (30-50 µm length), Protoperidinium bipes and Torodinium sp.. These four species contributed 82% to the dinoflagellate community. As in Experiment 1, no differences in abundance were found when the four dinoflagellate groups pooled were 50
CHAPTER II compared to the control (Table 2). For the pooled group an ANOVA proved insignificant (Figure 3E+F, Table 3) for the treatments as well as their interaction. At species level the athecate dinoflagellates ‘intermediate’ revealed significantly lower cell numbers in the siphoned treatment (F 1,8 = 8.2718, p = 0.02, Table 3) as compared to the FTT. No impact of the pre-screening process or the combination of treatment and prescreening on the other dinoflagellates could be found. As in Experiment 1, no differences were found for the Margalef index ‘d’ calculated for the whole community (data not shown) or when considering only the five most abundant groups (Table 3, Figure 3 G+H). Comparison of Treatments Siphoned Screening Screening x Treatment Mean values - Loss in comparison to FTT p Mean values - Loss in comparison to No Screening p - p Ciliates Lohmanniella oviformis a 16.9% 0.006 12.6% 0.026 n.s. Strombidium cf. tressum a 11.6% n.s. 50.7% 0.00007 0.035 a Strombidium cf. epidemum a 3.1% n.s. 9.7% n.s. n.s. Balanion comatum a 10.3% n.s. 2.8% n.s. n.s. Myrionecta rubra 'small' a 9.2% n.s. -11.8% n.s. n.s. Sum 5 most abundant ciliates 11.4% 0.032 17.4% 0.0036 n.s. Dinoflagellates Athecate dinoflagellates 'intermediate' a 17.6% 0.021 -2.7% n.s. n.s. Gyrodinium sp. 'intermediate' a 14.6% n.s. 19.7% n.s. n.s. Protoperidinium bipes a -17.9% n.s. -17.9% n.s. n.s. Torodinium sp. a -15.2% n.s. 2.8% n.s. n.s. Sum 4 most abundant dinoflagellates 11.0% n.s. 0.0% n.s. n.s. Chlorophyll a 7.2% 0.0025 b 2.6% n.s. 0.027 b Margalef diversity (d) Sum 5 most abundant ciliates -1.4% 0.026 -2.3% 0.002 n.s. Sum 4 most abundant dinoflagellates -1.5% n.s. 0.002% n.s. n.s. Table 3: Percentage of loss in abundance of the most abundant ciliate and dinoflagellate species, chlorophyll a contents and Margalef index ‘d’ due to siphoning in comparison to the FTT and prescreening in comparison to no pre-screening and effects of the combination between pre-screening and treatment during Experiment 2 (1. April 2008). P-values derived from ANOVA comparing all treatments (n = 6). n.s. = not significant (p > 0.05). a significantly lower abundance in the FTT with pre-screening treatments. b significantly higher content in the FTT with pre-screening treatments. 51
Page 1 and 2:
The role of heterotrophic dinoflage
Page 3:
“What we know is a drop, what we
Page 7 and 8: INTRODUCTION INTRODUCTION Understan
Page 9 and 10: INTRODUCTION flagellates) and metaz
Page 11 and 12: INTRODUCTION The remaining species
Page 13 and 14: INTRODUCTION Figure 4: Diplopsalis
Page 15 and 16: INTRODUCTION compared to dinoflagel
Page 17: INTRODUCTION “seawater dilution t
Page 20 and 21: RESEARCH AIMS Apart from the pure g
Page 22 and 23: OUTLINE OF THE THESIS the two diffe
Page 25 and 26: CHAPTER I CHAPTER I Dinoflagellates
Page 27 and 28: CHAPTER I Dinoflagellates and cilia
Page 29 and 30: CHAPTER I INTRODUCTION Marine resea
Page 31 and 32: CHAPTER I counted out at 200-fold m
Page 33 and 34: CHAPTER I Dinoflagellates closely f
Page 35 and 36: CHAPTER I Figure 3: Biomass [µgC L
Page 37 and 38: CHAPTER I prevents confusion with o
Page 39 and 40: CHAPTER I Figure 6: Comparison of c
Page 41: CHAPTER I should therefore occur on
Page 44 and 45: CHAPTER II 38
Page 46 and 47: CHAPTER II ABSTRACT Grazing experim
Page 48 and 49: CHAPTER II application, the alterna
Page 50 and 51: CHAPTER II Experiment 2 Experiment
Page 52 and 53: CHAPTER II Ciliates The three most
Page 54 and 55: CHAPTER II Experiment 2 Microzoopla
Page 58 and 59: CHAPTER II DISCUSSION Transfer tech
Page 60 and 61: CHAPTER II bottles when siphoning w
Page 62 and 63: CHAPTER II ACKNOWLEDGEMENTS This st
Page 64 and 65: CHAPTER III 58
Page 66 and 67: CHAPTER III ABSTRACT Mesocosm exper
Page 68 and 69: CHAPTER III the prey (Cowles et al.
Page 70 and 71: CHAPTER III The mesocosms were stir
Page 72 and 73: CHAPTER III Net growth of plankton
Page 74 and 75: CHAPTER III prior to the experiment
Page 76 and 77: CHAPTER III incubation bottles with
Page 78 and 79: CHAPTER III Data analysis To monito
Page 80 and 81: CHAPTER III General development of
Page 82 and 83: CHAPTER III Ciliate community After
Page 84 and 85: CHAPTER III Other microzooplankton
Page 86 and 87: CHAPTER III Microzooplankton Experi
Page 88 and 89: CHAPTER III Figure 6: (6a) General
Page 90 and 91: CHAPTER III Table 3: Temora longico
Page 92 and 93: CHAPTER III Table 4: Temora longico
Page 94 and 95: CHAPTER III The comparison of mesoc
Page 96 and 97: CHAPTER III Flagellates contributed
Page 98 and 99: CHAPTER III The effort to capture,
Page 100 and 101: CHAPTER III in words and deeds. Man
Page 102 and 103: CHAPTER III Table 2 Microzooplankto
Page 104 and 105: CHAPTER III Table 3b Temora longico
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CHAPTER III Table 4b Temora longico
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CHAPTER IV 102
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CHAPTER IV ABSTRACT The intra-speci
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CHAPTER IV Hansen, 1997). In turn,
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CHAPTER IV out in F/2 medium over 7
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CHAPTER IV the same patterns in G.
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CHAPTER IV Figure 1: General develo
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CHAPTER IV Favella ehrenbergii (Fig
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CHAPTER IV (24, 48, 72 hours of inc
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CHAPTER IV Growth response of G. do
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CHAPTER IV due to pre-conditioning
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CHAPTER IV This was also confirmed
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DISCUSSION described by competition
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DISCUSSION to know who they are. Th
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DISCUSSION Microzooplankton grazers
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DISCUSSION Figure 1: A rather simpl
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DISCUSSION 1986, Tillmann, 2004) co
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DISCUSSION To my knowledge similar
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DISCUSSION transported around the w
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SUMMARY by its larger competitor. T
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REFERENCES Buskey, E.J. & Stoecker,
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REFERENCES Gentsch, E., Kreibich, T
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REFERENCES Jeong, H.J., Yoo, Y.D.,
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REFERENCES Montagnes, D.J.S., 2003.
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REFERENCES Rose, J.M. & Caron, D.A.
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REFERENCES Teixeira, I.G. & Figueir
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