Format: ORAL

Sergio Armando Fuentes Agueda 1, Margarita Elizabeth Gallegos Martnez 1, Jos Alfredo Arvalo Ramrez 2, Jordan Kyril Golubov Figueroa 2 y Mara del Carmen Mandujano Snchez 3.

1 Universidad Autónoma Metropolitana-Iztapalapa, México City, México 2 Universidad Autónoma Metropolitana-Xochimilco, México City, México 3 Instituto de Ecología, UNAM, México City, México

Seagrasses are angiosperms that live mostly in the ocean. Also, they have ecological and economic importance, like having a highly primary production (500 4000g carbon m-2 year-1) and giving nourishment to fish and other important invertebrates. One of the strategies for evaluating the health of seagrasses is the evaluation of their photosynthetic efficiency. The objective of the study was to obtain theFv/Fmof Thalassia testudinum and to analyze the abiotic factors associated with photosynthetic efficiency in seagrasses. In 7 areas of The Gulf of Mxico and Yucatn, environmental parameters (temperature pH, depth, dissolved oxygen, salinity, nutrients in the water column, interstitial water nutrients, type of sediment, and organic carbon) were registered at each site. Plants of T. testudinum were collected in 7 areas along the coasts of The Gulf of Mxico and Yucatn during the years 2016 and 2019. They were in dark conditions for less than 24 hours, and with a Pulse-amplitude modulated (PAM) chlorophyll fluorometer, it was possible to register theFv/Fmof the youngest leaves. A PCA analysis was used to establish relations with the photosynthetic efficiency of T. testudinum.T. testudinum hasan average of 0.72 Fv/Fm ratio. Also, there were significant differences in the areas; Area 5 (San Felipe, Yucatán) presented the lowest Fv/Fm ratio (0.61). The most important factors in the PCA were, the Fv/Fm ratio of T. testudinum, depth, silicates, and dissolved inorganic nitrogen (DIN). Higher values of photosynthetic efficiency are related to a high amount of nutrients and low depths; areas that are low in these parameters will have low photosynthetic efficiency and be vulnerable to seagrasses meadows.