Metacommunity ecology explicitly incorporates processes at multiple spatial scales to explain the assembly and dynamics of a community. In a metacommunity, local communities interact with one another through the dispersal of individuals across a region. As such, metacommunities are molded by two sets of processes: local and regional. Local factors are those that directly impact a single local community, such as environmental conditions, competition, and predation. On the other hand, regional factors affect communities across a landscape and include mechanisms such as, immigration and emigration. The potential interactions between local and regional factors make metacommunity dynamics a unique body of theory when compared to classic community theory. However, while the direct influence of dispersal on metacommunity dynamics continues to be a well-researched topic, how dispersal interacts with local factors to shape metacommunity dynamics is a more open topic. In particular, one continuing gap in my knowledge is how dispersal interacts with biotic effect how it may affect metacommunities. One type of local biotic process that can directly affect communities is a strong interactive species, i.e., a species that affects community structure and diversity, and to the best of my knowledge, the interaction between dispersal and strongly interactive species has not been directly addressed experimentally. In the following study, I investigated the interaction of dispersal and a strong interactive species on metacommunity diversity and assembly. I chose Daphnia magna as my strong interacting species due to its biological and physical traits. Dispersal is known to create predictable patterns of diversity as it increases in a metacommunity. We made logical predictions based off of my knowledge of these patterns, and my inclinations regarding how dispersal would interact with a strong interacting species. The following predictions were made in relation to the control: 1) Alpha diversity would be the highest during low dispersal as new species would be introduced and maintained above the extinction threshold. I also predicted beta diversity would decrease with increased dispersal due to the homogenization of communities. 2) In the presence of D. magna, beta diversity would only increase during low dispersal due to possible rescue effects. 3) Temporal variability would decrease for the low dispersal treatment and increase for the high dispersal treatment in the absence of D. magna. 4) Temporal variability would overall increase across all treatments in the presence of D. magna. To carry out the study, I assembled outdoor mesocosms using a 2x3x3x4 factorial design (Daphnia Treatment: no addition of D. magna, addition of D. magna; Dispersal Treatment: no dispersal, low dispersal, high dispersal; three buckets were equivalent to one metacommunity; 4 replicates). There was a significant interaction between D. magna and dispersal. Over time, beta diversity decreased as communities became homogenized; however, the no dispersal treatment homogenized at a slower rate compared to the other treatments. In addition, D. magna appeared to create local selection for certain taxa resulting in the increase of Bosmina and Simocephalus while other taxa decreased, for example Streblocerus. This trend was likely due to the feeding and grazing habits of D. magna which is known to outcompete other large zooplankton for larger phytoplankton taxa. Lastly, D. magna directly influenced temporal variability of metacommunities in the experiment. In particular, the low dispersal treatment increased in temporal variability in the presence of D. magna. Again, this result could likely be attributed to D. magna effects selecting for certain taxa, or by the re-introduction of new or dying species with each dispersal through rescue effects. Overall, the results in my study supported majority of my predictions. It is clear that D. magna had an effect on communities as taxa abundances increased and beta diversity in the no dispersal treatment did not decrease as quickly. This result suggests that the introduction of D. magna as an invasive to non-local waters could pose a threat to local community dynamics. It is important to understand how a strong interactive species can affect communities across a landscape as they can greatly alter diversity and composition. Future studies should focus on expanding the dispersal gradient and incorporating a local strong interactive species and non-local strong interactive species to understand how they may change community dynamics. / Master of Science

No description available.

Lie, An Ying Alice. / Thesis submitted in: November 2008. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 115-134). / Abstracts in English and Chinese. / Chapter Chapter 1. --- Introduction --- p.1 / Chapter 1.1. --- Microzooplankton --- p.1 / Chapter 1.1.2. --- Microzooplankton grazing --- p.1 / Chapter 1.2. --- Dilution method --- p.4 / Chapter 1.2.1. --- Basic principles --- p.4 / Chapter 1.2.2 --- Variation and extensive uses of the dilution method --- p.7 / Chapter 1.2.3. --- Criticism of the dilution method --- p.9 / Chapter 1.2.4. --- Results of the dilution experiments and their implications --- p.11 / Chapter 1.3. --- The roles of microzooplankton --- p.16 / Chapter 1.4. --- Phytoplankton --- p.18 / Chapter 1.4.1. --- Size classification --- p.18 / Chapter 1.4.2. --- Chemotaxonomic marker pigments --- p.19 / Chapter 1.4.3. --- Nutrients and phytoplankton dynamics --- p.19 / Chapter 1.5. --- Hypothesis --- p.26 / Chapter 1.6. --- Objectives --- p.26 / Chapter 1.7 --- Research outline --- p.27 / Chapter 1.7.1. --- Microzooplankton grazing rates and phytoplankton growth rates --- p.27 / Chapter 1.7.2. --- Phytoplankton group selection --- p.27 / Chapter 1.7.3. --- Phytoplankton size selection --- p.27 / Chapter 1.8. --- Study sites --- p.27 / Chapter 1.81. --- Tolo Harbour --- p.28 / Chapter 1.8.2. --- Mirs Bay --- p.28 / Chapter 1.8.3. --- Biological and physio-chemical parameters --- p.30 / Chapter Chapter 2. --- Materials and methods --- p.33 / Chapter 2.1. --- Study site and sampling --- p.33 / Chapter 2.2. --- Dilution experiments --- p.33 / Chapter 2.2.1. --- Preliminary dilution experiments and enrichment tests --- p.35 / Chapter 2.2.2. --- HPLC --- p.37 / Chapter 2.2.3. --- Pigment data analysis --- p.41 / Chapter 2.2.4. --- Phytoplankton and microzooplankton community analysis --- p.42 / Chapter Chapter 3. --- Results --- p.43 / Chapter 3.1. --- Field parameters --- p.43 / Chapter 3.1.1. --- Physiochemical parameters --- p.43 / Chapter 3.1.2. --- Chlorophyll a --- p.46 / Chapter 3.2. --- Initial conditions --- p.49 / Chapter 3.2.1. --- Phytoplankton pigment and size fraction composition --- p.49 / Chapter 3.2.2. --- Microscopy cell counts --- p.56 / Chapter 3.3. --- Dilution experiments results --- p.64 / Chapter 3.3.1. --- Linear regression analysis results --- p.64 / Chapter 3.3.2. --- Estimated pigment specific phytoplankton growth rates and microzooplankton grazing rates --- p.66 / Chapter 3.3.3. --- Ratio of microzooplankton grazing to the phytoplankton growth rate in ambient nutrient --- p.70 / Chapter 3.4. --- Correlation analyses --- p.78 / Chapter 3.4.1. --- Physiochemical parameters --- p.78 / Chapter 3.4.2. --- Initial pigment concentration --- p.81 / Chapter 3.4.3. --- Initial densities --- p.81 / Chapter 3.4.4. --- Phytoplankton growth rates and microzooplankton grazing rates --- p.82 / Chapter 3.5. --- Percentage and composition shifts --- p.83 / Chapter 3.5.1. --- Percentage change --- p.83 / Chapter 3.5.2. --- Size fraction --- p.83 / Chapter 3.5.3. --- Pigment markers --- p.83 / Chapter Chapter 4. --- Discussions --- p.103 / Chapter 4.1. --- Hypothesis --- p.103 / Chapter 4.2. --- Phytoplankton growth rates and microzooplankton grazing rates --- p.104 / Chapter 4.3. --- Dilution experiment --- p.105 / Chapter 4.3.1. --- Nutrient enrichment --- p.105 / Chapter 4.3.2. --- Shift of pigment compositions --- p.106 / Chapter 4.3.3. --- Experiment limitations --- p.107 / Chapter 4.4. --- Microzooplankton feeding preference --- p.108 / Chapter 4.4.1. --- Phytoplankton size --- p.108 / Chapter 4.4.2. --- Phytoplankton group --- p.109 / Chapter 4.5. --- Food web dynamics --- p.110 / Chapter 4.5.1. --- The role of microzooplankton --- p.110 / Chapter 4.5.1.1. --- Nutrient recycling --- p.110 / Chapter 4.5.1.2. --- Energy transfer --- p.111 / Chapter 4.5.1.3. --- Phytoplankton control --- p.111 / Chapter 4.5.2. --- The role of mesozooplankton --- p.111 / Chapter Chapter 5. --- Conclusions --- p.113 / References --- p.115 / Appendices --- p.135

Methylmercury (MeHg) bioaccumulation in freshwater aquatic systems is impacted by anthropogenic stressors, including climate change and excess nutrients. The goal of this study was to determine how warmer water temperatures and excess nutrients would impact zooplankton communities and phytoplankton concentrations, and in turn increase or decrease MeHg concentrations in freshwater zooplankton. I used a 2x2 factorial design to determine if the interaction of temperature and nutrients would impact plankton metrics and zooplankton MeHg concentrations. Mesocosms were filled with Hg-contaminated water and plankton from Cottage Grove Reservoir, Oregon, a waterbody that has experienced decades of elevated MeHg concentrations and corresponding fish consumption advisories due to run-off from Black Butte Mine tailings, located within the watershed. Treatment combinations of warmer temperature (increased by 0.5°C) and nutrient addition (a single pulse of excess nitrogen and phosphorous), control, and a combination of temperature and nutrients were applied to mesocosms. While plankton did respond to treatments, zooplankton biomass and phytoplankton concentrations did not have significant relationships to MeHg concentrations. However, a significant interactive effect of nutrients and temperature was present: nutrients appeared to buffer against increased MeHg concentrations when temperature was elevated. The mechanisms for this interaction appear to be related to a shift to larger body size and an increase in abundance of Daphnia over copepods. Findings suggest that community composition and species-specific differences in both zooplankton and phytoplankton could play a role in MeHg transfer to higher trophic levels.

The hydrodynamic disturbances generated by two types of free-swimming, marine zooplankton were quantified experimentally in the laboratory with a novel, infrared Particle Image Velocimetry (PIV) system. The study consisted of three main parts: (1) the flow fields of free-swimming and tethered Euchaeta antarctica were compared to determine the effects of tethering, (2) three species of copepods (Euchaeta rimana, Euchaeta elongata, and Euchaeta antarctica) that live in seawater in a range of temperatures (23 ºC - 0 ºC) and a corresponding range of fluid viscosity (0.97 - 1.88 mm2 s-1) were analyzed experimentally and with a computational fluid dynamics model (FLUENT) to assess the effect of size and fluid viscosity on the flow fields, (3) the flow fields were collected for individuals of two species of euphausiids (Euphausia pacifica and Euphausia superba) to compare the effect of size and Reynolds number on propulsion and the spatial extent of the flow disturbance. In addition to the measured flow fields around solitary krill, flow fields were collected around small, coordinated groups of E. superba to examine group sensory cues through hydrodynamics. In the first part of this investigation, it was determined that tethering zooplankton during data collection resulted in flow fields with increased asymmetry and larger spatial extent due to the unbalanced force applied to the fluid by the tether. In response to these findings, only flow fields collected for free-swimming organisms were used in the subsequent studies. In the second part of the study, the increase in viscosity between subtropical and temperate fluid environments in conjunction with increased size and species-specific swimming speeds resulted in similar Reynolds numbers among E. elongata and E. rimana (in both cruising and escaping modes). During cruising (Re ~10), the spatial extent of the copepod hydrodynamic disturbances and propulsion costs were similar between species. In the case of fluid distrubances of escape (Re ~ 100), the spatial extent and energetic cost were larger for the larger species ( E. elongata). In the third part of the study, the hydrodynamic disturbance produced by E. superba (larger krill species) was found to be longer in horizontal spatial extent and at scales more appropriate for communication within schools than the hydrodynamic disturbance produced by E. pacifica. However, the sensory cue in coordinated groups of krill was complicated by the interaction of multiple flow disturbance fields, which suggests that hydrodynamic cues between krill in groups are restricted to small distances. The energetic cost of propulsion was ten times greater for the larger species of krill, and energetic expenditure did not appear to decrease for krill swimming in coordinated groups.

During the Norwegian North Polar Expedition of 1893-96, the historie voyage of the Fram ( Sars, G.O. 1900), the first zooplankton collections were taken from the Arctic Basin. In 1931 the Nautilus made collections north of Spitzbergen, being the first submarine to attempt polar research (Farran, 1936). [...]

Alterations in the summer zooplankton community that have appeared since Johnson's (1972) study of a Michigan City (site M) transect in southeastern Lake Michigan were investigated. Vertical tows were made at 5, 10, 15, and 18 meters from June through August in 1987 and 1988 in order obtain data that could be compared with that of Johnson (1972).Subsamples analyzed were proportionately larger than those of Johnson (1972), in order to obtain a detailed profile of the species and numbers in the community, and to identify large, predatory zooplankton species that are believed to have been severely impacted by the explosive growth of the alewife population during the 1960's.The most common crustacean species collected were: Diacyclops thomasi, Leptodiaptomus minutus, Leptodiaptomus ashlandi, calanoid and cyclopoid nauplii and copepodids, Daphnia retrocurva, and Bosmina longirostris. The most common rotifer species collected were Keratella c. cochlearis, Keratella crassa, Kellicottia longispina, Conochilus sp., and Polyarthra sp.. Higher numbers of Epischura lacustris adults and copepodids, Leptodora kindti, Mesocyclops edax, Daphnia galeata mendotae, and the rotifers Asplanchna priodonta, Conochilus sp., Keratella crassa, and Ploesoma truncatum were recorded as compared to Johnson's 1972 data. The summer zooplankton community of this transect appears to have been represented in the summers of 1987 and 1988 by a greater number of large crustacean zooplankton species, as opposed to a 1970 community dominated by small microfiltrators and D. thomasi. / Department of Biology

Thesis (Ph. D.)--Oregon State University, 2006. / Includes bibliographical references. Also issued online.

Thesis (M. Sc.), Memorial University of Newfoundland, 1998. / Bibliography: leaves 138-163.

Thesis (M.Sc. (Ichthyology & Fisheries Science)) - Rhodes University, 2009.