Graduate Thesis Or Dissertation
 

Zooplankton of the Galapagos Islands

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  • The marine climate of the Galapagos is spatially and seasonally heterogeneous. A taxonomically comprehensive study of Galapagos zooplankton has never been done. This study is an initial effort to establish the distribution and community structure of zooplankton in the Archipelago. I collected zooplankton samples by vertical tows over the Galapagos shelf during the islands’ cold and warm seasons. Abundance was determined and copepods and euphausiids were identified to species. Hydrographic, nutrient and chlorophyll profiles were obtained for some sites. Non-metric Multidimensional Scaling (NMS) ordinations, Multi-Response Permutation Procedures (MRPP) and Indicator Species Analyses (ISA) were used to determine trends in community composition. Two marine systems were identified: 1) a nutrient-rich upwelling system with a shallow mixed layer and a diatom dominated phytoplankton community in the west and 2) a non-upwelling system with a deeper mixed layer, lower surface nutrient concentrations and a phytoplankton community dominated by small cells in the east. During the cold season three distinct zooplankton communities were observed that divide into western, central, and southeastern regions. During the warm season, the community in the west was replaced by a mix of species from the central region and abundance decreased. The diverse zooplankton community with varying geographical and seasonal affinities reflects the advective sources of surrounding waters. In addition to diverse oceanic environments, the Galapagos also have a unique set of inland pools known as anchialine habitats. I collected zooplankton from various anchialine pools in three different islands. These pools contain species of specialized cave-dwellers including undescribed species of Ridgewayia and Pseudocyclops (calanoid copepods). I describe these species and apply morphological and molecular methods to determine phylogenetic relationships and patterns of colonization. The mitochondrial gene cytochrome c oxidase subunit I (COI) and the nuclear internal transcribed spacer 1 (ITS1) were used for phylogenetic analyses. The ITS1gene successfully reconstructed phylogenies, but the COI gene was highly conserved across these two families. This gene may not be appropriate as the current standard for “bar-coding” all marine species. These anchialine copepods are a result of several independent colonization events with phylogenetic ties to extant species in the western Pacific and Caribbean.
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