School of Engineering and Science - Jacobs University

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CHAPTER III Microzooplankton Experiment 1 - (MMC 30.33 µg L -1 ) Experiment 2 - (MMC 74.47 µg L -1 ) Phytoplankton F c p I c p E* F c p I c p E* Chaetoceros spp. 1.99E-08 * 0.30 * 0.30 1.70E-08 **** 0.16 **** 0.24 Rhizosolenia spp. 9.11E-09 ** 0.33 ** -0.08 1.02E-08 **** 0.41 **** -0.01 Thalassiosira spp. 1.85E-08 ** 0.73 ** 0.26 8.46E-09 **** 0.35 **** -0.11 Flagellates 6.35E-09 ** 0.10 ** -0.26 1.13E-08 * 0.11 * 0.04 other Diatoms -3.46E-09 * -0.02 * -1.00 5.49E-09 ** 0.03 ** -0.31 TOTAL PHYTOPLANKTON 1.40E-08 * 1.57 * 8.85E-09 *** 1.00 *** RELATED TO TOTAL MICROZOOPLANKTON CARBON F 0.425 I 47.65 F 0.659 I 74.58 Experiment 3 - (MMC 93.82 µg L -1 ) Experiment 4 - (MMC 33.12 µg L -1 ) Phytoplankton F c p I c p E* F c p I c p E* Chaetoceros spp. 5.53E-09 * 0.08 * 0.13 2.12E-08 **** 0.17 **** 0.13 Rhizosolenia spp. 4.48E-09 **** 0.16 **** 0.03 1.49E-08 **** 0.39 **** -0.04 Thalassiosira spp. 1.59E-09 * 0.08 * -0.46 2.09E-08 **** 0.49 **** 0.13 Flagellates 5.68E-09 *** 0.09 *** 0.14 2.92E-09 0.06 -0.70 other Diatoms 3.98E-09 * 0.01 * -0.03 2.14E-08 **** 0.02 **** 0.14 TOTAL PHYTOPLANKTON 5.77E-09 **** 0.62 **** 1.19E-08 *** 0.97 *** RELATED TO TOTAL MICROZOOPLANKTON CARBON F 0.542 I 58.02 F 0.394 I 32.13 Table 2: Microzooplankton carbon specific filtration rates F c [L µgC predator -1 d -1 ] and carbon specific ingestion rates I c [µgC prey µgC predator -1 d -1 ], total filtration rates F [L d -1 ], total ingestion rates I [µgC prey L -1 d -1 ] and electivity E* [-] for different phytoplankton groups. Positive selection marked with gray background. MMC = mean microzooplankton carbon biomass. P-values are the same as for the grazing rates of microzooplankton. * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001. At the phytoplankton peak (Experiment 2) total grazer biomass (74 µgC L -1 ) was more than twice as high as during the pre-bloom experiment and shares of dinoflagellate and ciliate biomass were almost equal. Ciliates displayed the highest growth rates of 0.37 d -1 in this phase. The community showed an I c of 1.00 µgC prey µgC predator -1 d -1 at a total filtration rate F of 0.66 L d -1 (Table 2) and a total grazing rate g of 0.66 d -1 (Table 1). As µ 0 (0.77 d -1 ) was higher than g 93% of P i and 90% of P p (Table 1) were grazed. Food selectivity reflected the high grazer diversity and was spread over all categories of phytoplankton resulting in a total daily ingestion of 74.58 µgC L -1 d -1 (Table 2). On group level microzooplankton selected flagellates and Thalassiosira spp. (Table 2). The early post bloom phase (Experiment 3) was characterized by the highest grazer biomass of all experiments (94 µgC L -1 ) and ciliates clearly dominated the community (69%). Microzooplankton grazed 72% of P i and 87% of P p at a rate of 0.54 d -1 (g) and filtered 0.54 L d -1 (F) (Table 1+2). Phytoplankton displayed a higher instantaneous growth rate µ 0 (0.65 d -1 ) than in the fertilized incubation bottles (k = 0.39 d -1 ). I c (0.62 80
CHAPTER III µgC prey µgC predator -1 d -1 ) was the lowest detected in our experiments leading to a total daily ingestion I of 58.02 µgC L -1 d -1 (Table 2). Microzooplankton selected for flagellates (except flagellates 5 µm), Rhizosolenia spp. and Chaetoceros spp. (Table 2). In the late post-bloom phase (Experiment 4), grazer biomass (33 µgC L -1 ) was as low as before the bloom and again saturated feeding was detected in 5 phytoplankton species (Appendix Table 1). Beside the now dominating dinoflagellates, rotifers became as important as ciliates. The community grazed 48% of P i and 80% of P p at a rate of 0.39 d -1 (g) and filtered 0.39 L d -1 (F) (Table 1+2). I c (0.97 µgC prey µgC predator -1 d -1 ) increased to a value similar to Experiment 2 resulting in a total daily ingestion I of 32.13 µgC L -1 d -1 . Again instantaneous growth µ 0 (0.52 d -1 ) of the phytoplankton exceeded the growth in fertilized bottles (0.41 d -1 ) (Table 1). Selectivity was similar to Experiment 1 whereas also the category ‘other diatoms’ was selected. Microzooplankton predator-prey relationships A direct coupling between ciliate and flagellate biomass was observed. This resulted in a strong suppression of flagellate biomass from 26 to 10 µgC coincident with the ciliate peak (Figure 6a). This was most pronounced for thecate and athecate dinoflagellates < 15 µm which disappeared totally during the Strombidium capitatum bloom (Figure 6b). Simultaneously with the disappearance of both dinoflagellate groups S. capitatum started to form cysts and its population collapsed totally within one week. With the break-down of strombidiid and strobilid biomass at the end of March a relaxation from grazing pressure enabled the flagellates to regenerate again. The majority of dinoflagellate species we found in the mesocosms are reported to prefer diatom prey. As diatoms did hardly change in composition, dinoflagellate succession in the mesocosms was not as pronounced as for the ciliates. While two groups disappeared during the first half of our experiment due to predation by ciliates as described above, the remaining dinoflagellate community composition remained relatively constant until the end of the experiment. We also found a strong predator-prey relationship between a thecate amoeba and Chaetoceros spp.. The apparently parasitic amoeba was found to be attached only to cells of this genus. The abundance of the amoeba followed the development of Chaetoceros spp. and showed a similar decline towards the end of the experiment. 81
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The role of heterotrophic dinoflage
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“What we know is a drop, what we
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INTRODUCTION INTRODUCTION Understan
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INTRODUCTION flagellates) and metaz
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INTRODUCTION The remaining species
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INTRODUCTION Figure 4: Diplopsalis
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INTRODUCTION compared to dinoflagel
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INTRODUCTION “seawater dilution t
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RESEARCH AIMS Apart from the pure g
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OUTLINE OF THE THESIS the two diffe
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CHAPTER I CHAPTER I Dinoflagellates
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CHAPTER I Dinoflagellates and cilia
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CHAPTER I INTRODUCTION Marine resea
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CHAPTER I counted out at 200-fold m
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CHAPTER I Dinoflagellates closely f
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Page 46 and 47: CHAPTER II ABSTRACT Grazing experim
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Page 50 and 51: CHAPTER II Experiment 2 Experiment
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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 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
Page 106 and 107: CHAPTER III Table 4b Temora longico
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Page 110 and 111: CHAPTER IV ABSTRACT The intra-speci
Page 112 and 113: CHAPTER IV Hansen, 1997). In turn,
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Page 116 and 117: CHAPTER IV the same patterns in G.
Page 118 and 119: CHAPTER IV Figure 1: General develo
Page 120 and 121: CHAPTER IV Favella ehrenbergii (Fig
Page 122 and 123: CHAPTER IV (24, 48, 72 hours of inc
Page 124 and 125: CHAPTER IV Growth response of G. do
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Page 128 and 129: CHAPTER IV This was also confirmed
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Page 132 and 133: DISCUSSION described by competition
Page 134 and 135: 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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