Paleoenvironmental analysis using thecamoebians and foraminifera in Mexican anchialine caves: a focus on Aktun Ha (Carwash) Mexico
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Notice bibliographique
Résumé
Thecamoebians (testate amoebae) and foraminifera have never been systematically investigated in a phreatic cave system. Foraminifera (marine to brackish water protists) and thecamoebians (brackish to freshwater protists) are cosmopolitan and have been studied in virtually all environments on Earth. Although foraminifera-bearing sediment has been observed from vadose cave environments in the last 20 years, there is no mention of their ecology - or mere existence - in flooded cave passages in any micropaleontology or microbiology textbooks. Only one published manuscript briefly mentions foraminifera in preliminary test samples from phreatic caves in Bermuda. The unprecedented ability of these organisms to colonize any environment on Earth led to the hypothesis that they are also exploiting global phreatic caves. The karst landscape of the Yucatan Peninsula, Mexico, is an ideal setting for the formation of anastomosing, anchialine, phreatic cave systems. The stratified aquifer contains passages in both the superior freshwater lens (thecamoebian habitat} and marine water (foraminifera habitat) intruding below, creating an ideal location to test the hypothesis. Several important contributions have resulted from investigating surface samples and cores in this region. (1) Using thirty-three surface samples from three different cenotes, thecamoebians and foraminifera were found living in the sinkhole (cenote) environment, which are the physical entrance into the caves. An ecological boundary of -3.5 ppt was determined for thecamoebians, with Centropyxis constricta "aerophilia" determined as the most euryhaline thecamoebian taxa. (2) Foraminifera and thecamoebians have been colonizing Carwash Cave since the Sangamon Interglacial (MIS 5e), based on seventy-five surface samples collected throughout the system. The recovered taxa have responded to changes in cave environment similarly to other coastal systems, thereby indicating their potential as paleoenvironmental proxies in phreatic caves. (3) In conjunction with stable isotopes (δ<sup>13</sup>C<sub>org</sub> and δ<sup>15</sup>N<sub>org</sub>), thecamoebians and foraminifera were successful recorders of mid-late Holocene paleoenvironmental evolution in Carwash Cave. An important salinity transition in the freshwater lens (from >2 ppt to 1.5 ppt) of the aquifer at ~2760 Cal yrs BP is coincident with changes in the local Maya populations, indicating a possible environmental linkage between ancient freshwater resources and Maya cultural genesis. This thesis demonstrates unequivocally that thecamoebians and foraminifera exist in phreatic cave systems and hold wider potential as paleoenvironmental proxies in other global phreatic caves.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,035 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découle