Abstract:
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.
