Capstone Title

Non-Framework Coral Communities in the Gulf of California, Mexico

Defense Date

5-2007

Document Type

Capstone

Degree Name

M.S. Marine Environmental Sciences

First Advisor

Bernhard Riegl

Second Advisor

Samuel Purkis

Abstract

The goal of this present study was to describe environmental parameters along the Gulf of California(23°N to 29°N), and understand and analyze how they determine the presence and structure of coral communities. Here, high latitude non-framework coral communities thrive in limiting environmental factors. Three sites were used to illustrate changes in temperature, nutrients, and coral species diversity along an increasing latitude gradient. Bahia de Los Angelesto the north maintains monotypic colonies of Porites sp. in a cooler, eutrophic environment, while species diversity and temperature increased to the south in mesotrophic and oligotrophic conditions. The majority of zooxanthellate species present in the Gulf of California have Indo-Pacific origin, with the possibility of Porites sverdrupi being generated by allopatric speciation. Regional oceanographic conditions in theGulf of California determine community structure, more than biological factors. Coral communities are sporadically affected by hurricanes with an average frequency of 0.62 hurricane/yr, within a radius of 100 km. Sea-surface temperatures records for the period of 136 years from the HADISST1 data set were correlated to warm related bleaching events in the Gulf in 1982-83 and 1997-98, and to cold related bleaching in 1989. The coral communities of theGulf of California suffered moderate bleaching and mortalities in 1997-1998 (ENSO), even when this event is considered one of the strongest events in the century. Hurricanes and ENSO events appear to be attenuated in an increasing latitude gradient in the Gulf. Overall, the analysis indicates that the structure of coral communities in theGulf of California are dominated more by regional oceanography, than perhaps large-scale oceanographic/atmospheric events.

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