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CHAPTER II Ciliates The three most abundant ciliate groups were: Myrionecta rubra ‘intermediate’ (35-50 µm length), Scuticociliates and Myrionecta rubra ‘small’ (15-25 µm length). These three groups accounted for 84% of the total abundance of the FTT treatment and 77% of the siphoned treatment (mean values). They therefore dominated the ciliate community. We found a significant ciliate cell loss of 41% due to siphoning (t = 3.162, df = 4, p = 0.034, two-sided t-test) (Figure 2A, Table 1) for pooled values of the three most abundant groups leading to significant changes in diversity. The Margalef index ‘d’ (Figure 2B, Table 1) for the three most abundant ciliate groups was significantly lower for the FTT (t = -2.569, df = 4, p = 0.031, single-sided t-test) compared to siphoning. No difference in the Margalef index was observed between both treatments for the whole ciliate community (data not shown). Figure 2: Experiment 1. (A) Mean abundance and (B) Margalef diversity ‘d’ of the most abundant ciliate and dinoflagellate species. Both treatments were done using a 200 µm pre-screened natural seawater sample. Significant difference marked with asterisk. Error bars correspond to one standard deviation. At species/group level the loss of cells was most pronounced in the category M. rubra ‘intermediate’. This size class of M. rubra accounted for 54% of total ciliate cells (FTT) and displayed a significant loss of 56% in cell numbers in the siphoned treatments (t = 3.483, df = 4, p = 0.025, two-sided t-test). The category M. rubra ‘small’ showed a similar pattern to M. rubra ‘intermediate’ with a 34% lower mean cell number when siphoned, however this effect was not statistically significant given the large count uncertainties. For the category “Scuticociliates” no significant difference between both treatments could be detected. 46
CHAPTER II Although chlorophyll a concentrations during our experiment were relatively low (< 0.2 µg/L), we detected significant differences between both methods, with lower chlorophyll a contents in the siphoned treatments (t = 5.366, df = 4, p = 0.006, twosided t-test) (Table 1), possibly linked to the loss of M. rubra cells. Dinoflagellates Four groups, accounting for 85% of the total dinoflagellate abundance in both treatments, were used for statistical analysis: Thecate dinoflagellates ‘small’ (20-25 µm length), Scrippsiella sp., Gyrodinium sp. ‘intermediate’ (30-50 µm length) and Torodinium sp. (Table 1). In contrast to observations for the most abundant ciliate categories, we found no differences between the two treatments for the four most abundant dinoflagellate groups pooled together or at species level (Figure 2A, Table 1). Margalef indices ‘d’ calculated for the four most abundant and all dinoflagellate categories also revealed no differences in abundance for both treatments (Figure 2B, Table 1). Comparison of Treatments Siphoned - 200 µm screening Mean values - Abundance in comparison to FTT Loss in comparison to FTT p Ciliates Myrionecta rubra 'intermediate' a 44.0% 56.0% 0.025 Scuticociliates a 102.6% -2.6% n.s. Myrionecta rubra 'small' a 65.6% 34.4% n.s. Sum 3 most abundant ciliates 59.0% 41.0% 0.034 Dinoflagellates Thecate dinoflagellates 'small' a 96.9% 3.1% n.s. Scrippsiella sp. a 77.9% 22.1% n.s. Gyrodinium sp. 'intermediate' a 103.4% -3.4% n.s. Torodinium sp. a 126.9% -26.9% n.s. Sum 4 most abundant dinoflagellates 94.8% 5.2% n.s. Chlorophyll a 75.3% 24.7% 0.006 Margalef diversity (d) Sum 3 most abundant ciliates 108.6% -8.6% 0.031* Sum 4 most abundant dinoflagellates 100.5% -0.5% n.s. Table 1: Percentage of loss based on abundances of the most common ciliate and dinoflagellate groups, chlorophyll a contents and Margalef index ‘d’ during siphoning compared to the FTT for Experiment 1 (4. July 2007). P-values derived from double-sided t-tests (n = 3). n.s. = not significant (p > 0.05). * P- value derived from single-sided t-test. 47
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 54 and 55: CHAPTER II Experiment 2 Microzoopla
Page 56 and 57: CHAPTER II Asterisk * 1 symbolizes
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
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CHAPTER III Table 2 Microzooplankto
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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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