Evaluation of photosynthetic pathways of vegetation, and of sources of sedimentary organic matter through C in Terminos Lagoon, Campeche, México

Abstract

SUBMERGED VEGETATION WAS ISOTOPICALLY CHARACTERIZED IN ORDER TO DETERMINE THE PHOTOSYNTHETIC MECHANISM USED BY EACH SPECIES AND ITS ADAPTATION TO A TROPICAL LAGOONAL ENVIRONMENT OF VARIABLE SLAINITY. ISOTOPIC COMPOSITION FOR THALASSIA TESTUDINUM OF -11.6 TI 15.9 AND DICTYOTA SP OF -16.8 TO 18.7 WAS REGISTERED. FOR HALODULE WRIGHTII AND THE RED ALGAE TWO INTERVALS WERE REGISTERED: H. WRIGHTYY FROM 15.2 TO 17.0 TO THE NORTHEAST OF THE LAGOON AND FROM -23.6 TO 27.6 THROUGHOUT THE REST OF THE SYSTEM, AND THE RED ALGAE OF -17.2 ON THE SUBLITTORAL (BAHAMITA) AND FROM -23.3 TO 27.1 WITHIN THE LAGOON. THE REGISTRATION OF THE TWO INTERVALS OF ISOTOPICA VALUES FOR THESE LAST TWO TYPES OF VEGETATION, THE MANNER IN WHICH THESE INTERVALS ARE RELATED TO THE DISTRIBUTION OF THE VEGETATION WITHIN THE SYSTEM AND TO THE ENVIRONMENTAL CHARACTERISTICS OF EACH LOCALITY, AND THE IMPLICATIONS WITH RESPECT TO PHOTOSYNTHESIS, ARE DISCUSSED. SURFACE SEDIMENT AND DETRITUS WERE ISOTOPICALLY CHARACTERIZED IN ORDER TO IDENTIFY THE NATURAL SOURCES OF ORGANIC CARBON AND ITS DISTRIBUTION WITHIN THE LAGOON. A CLUSTER ANALYSIS WAS APPLIED TO HYDROLOGICAL, SEDIMENTARY AND ISOTOPIC DATA TO DEFINE GROUPS OF SIMILAR LOCALITIES. THE LAGOON WAS DIVIDED INTO TWO AREAS: AREA 1 TO THE NORTH AND NORTHEAST WITH AN AVERAGE δ¹³C-15.5‰ WHICH INDICATES THAT THE ORGANIC MATTER OF SEAGRASS AND ALGAE BEDS IS THE SOURCE OF ORGANIC CARBON, AND AREA 2, THE REST OF THE SYSTEM WITH AN AVERAGE δ¹³C OF -20.3‰ THAT INDICATES A PREDOMINANCE OF ORGANIC CARBON OF TERRESTRIAL ORIGIN.