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Efecto de la temperatura sobre las tasas de fotosíntesis, crecimiento y calcificación del alga coralina de vida libre Lithophyllum margaritae

The Baja California peninsula represents a biogeographical boundary contributing to regional differentiation among populations of marine animals. We investigated the genetic characteristics of perennial and annual populations of the marine angiosperm, Zostera marina, along the Pacific coast of Baja California and in the Gulf of California, respectively. Populations of Z. marina from five coastal lagoons along the Pacific coast and four sites in the Gulf of California were studied using nine microsatellite loci. Analyses of variance revealed significant interregional differentiation, but no subregional differentiation. Significant spatial differentiation, assessed using theta(ST) values, was observed among all populations within the two regions. Z. marina populations along the Pacific coast are separated by more than 220 km and had the greatest theta(ST) (0.13-0.28) values, suggesting restricted gene flow. In contrast, lower but still significant genetic differentiation was observed among populations within the Gulf of California (theta(ST) = 0.04-0.18), even though populations are separated by more than 250 km. This suggests higher levels of gene flow among Gulf of California populations relative to Pacific coast populations. Direction of gene flow was predominantly southward among Pacific coast populations, whereas no dominant polarity in the Gulf of California populations was observed. The test for isolation by distance (IBD) showed a significant correlation between genetic and geographical distances in Gulf of California populations, but not in Pacific coast populations, perhaps because of shifts in currents during El Niño Southern Oscillation (ENSO) events along the Pacific coast.

The importance of submerged aquatlc macrophytes to coastal ecosystems has generated a need for knowledge of minlmum l~g h t levels that wlll support the m a~n t e n a n c e and restoration of healthy populations Our goals were (1) to evaluate the s e n s~t~v~t y to natural, non-sinusoidal fluctuatlons in irradiance I of analytical integration techniques for calculating daily carbon gain (2) to evaluate the H,,, (the daily period of I-saturated photosynthesis) model of daily production relat~ve to models based on Instantaneous photosynthesis vs Irradiance ( P v s I ) and (3) to provlde some guidance for the temporal d e n s~t y of Irradiance data r e q u~r e d for accurate estimation of dally carbon gain Monthly measures of the P v s I response of an eelgrass Zostera m a n n a L population were used to p~e d l c t rates of dally carbon galn from continuous in sjtu recordings of I Dally ~n t e g r a t e d I was not a reliable predictor of daily product~on Numencal (iterative) integration of H,,, was much more r e l~a b l e but r e q u~r e d repeated measures of I within a day as did numencal integrat~on of P vs I Analytical (non-iterative) models based only on observations of l,, (noon) could not p r e d~c t daily production accurately Analyt~cal models of P v s I and H,,, agreed with each other, however, indicating that the analyt~cal models may be useful where the daily pattern of I is sinusoidal Given the h~g h degree of temporal vanability in coastal 11ght environments continuous monltonng of hght a v a~l a b~l i t y may be required for calculation of daily production and rehable management of aquatlc macrophyte populations

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The pristine environmental conditions of offshore islands do not guarantee maximum genetic diversity. Future restoration and transplantation efforts of seagrasses must recognize cryptic species and consider the degree of both genetic and genotypic variation in candidate donor populations.

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