Publication Date

2017-12-06

Availability

Open access

Embargo Period

2017-12-06

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Biology (Arts and Sciences)

Date of Defense

2017-11-07

First Committee Member

Kathleen Sullivan Sealey

Second Committee Member

J. Albert C. Uy

Third Committee Member

David Die

Fourth Committee Member

Carla Hurt

Abstract

The Caribbean is generally an oligotrophic sea; however, in the southern portion between Venezuela and Colombia, a yearly, moderate, coastal upwelling fuels a very productive marine ecosystem, the Southern Caribbean Upwelling System. Extensive submerged aquatic vegetation (SAV) ecosystems are found in the Colombian side of the system, by La Guajira peninsula. SAV ecosystems constitute key habitat for multiple marine fauna species, specially at juvenile/larval stages. La Guajira’s SAV unique, upwelled ecosystems are hypothesized as important foraging and developmental habitat for the endangered, migratory sea turtle Chelonia mydas. The complex habitat-shifting behavior and very long-lasting juvenile stage traits of the species limit its populations’ growth. This lengthy juvenile stage its spent primarily at the Developmental Habitat (DH). The identification of quality DHs for the species, and the acknowledgement of their relative contribution to the overall dynamics of the C. mydas populations, is important for its ecology and conservation. This work aimed to quality the extent and diversity of SAV communities, known food items of the species, in the upwelled coastal waters of La Guajira, Colombia, a likely DH for the species. Also, this work looked at the quality of this DH from external indicators of the individuals aggregating in these waters, including distributional and body condition indicators. Additionally, this work aimed to estimate the connectivity patterns of this DH to nesting populations of the species in the Atlantic basin. Extensive and highly diverse SAV ecosystems dominated by macroalgae taxa were found in the studied area. Preferred food items by the species, were macroalgae species such as the red Gracilaria sp. Red algae were very common taxa in the area, even driving differences in species richness among sites. The study area was occupied by an aggregation of mostly immature turtles ranging from 16.2 cm to 87 cm in carapace straight length. The body condition of immature sea turtles in La Guajira was good and slightly better than other populations in the Caribbean. Thus, it is proposed that la Guajira is a quality habitat for C. mydas in the Atlantic. Finally, the genetic diversity of the turtle aggregation was high and slightly more so than other foraging or developmental areas in the Atlantic. This could be due to the origin populations of immature turtles from from three distinct demographically-connected groups of the species. Observed contributions may be explained by the opposite-direction, rapid currents that reach the study area. However, regional differences within the area existed that cannot be explained only by the influence of currents. A model system, the Central Caribbean was proposed to explore the role of habitat quality in explaining patterns of demographic connectivity of the Atlantic C. mydas within regions, using a migratory network theoretical framework.

Keywords

La Guajira; southern caribbean upwelling system; developmental habitat; submerged aquatic vegetation; green sea turtle

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