Oxygenation of a karst subterranean estuary during a tropical cyclone: mechanisms and implications for the carbon cycle

Abstract

Seasonal precipitation affects carbon turnover and methane accumulation in karst subterranean estuaries, the region of coastal carbonate aquifers where hydrologic and biogeochemical processes regulate material exchange between the land and ocean. However, the impact that tropical cyclones exert on subsurface carbon cycling within karst landscapes is poorly understood. Here, we present 5-month-long hydrologic and chemical records from 1 and 2 km inland from the coastline within the Ox Bel Ha Cave System in the northeastern Yucatan Peninsula. The record encompasses wet and dry seasons and includes the impact of rainfall during the development of Tropical Storm Hanna in October 2014. Methane accumulated in highest concentrations at the inland site, especially during the wet season preceding the storm. Intense rainfall led to episodic increases in water level and salinity shifts at both sites, indicating a spatially widespread hydrologic response. The most profound storm effect was a $ 0.8 mg L À1 pulse of dissolved oxygen that declined to zero within 2 weeks and corresponded with a reduction of methane. A positive shift in methane's stable carbon isotope content from À62.6‰ AE 0.6‰ before the storm to À44.0‰ AE 2.4‰ after the storm indicates microbial methane oxidation was a mechanism for the loss of groundwater methane. Post-storm methane concentrations did not recover to pre-storm levels during the observation period, suggesting tropical cyclones have long-lasting (months) effects on the carbon cycle. Compared to seasonal effects, mixing and oxygen inputs during storm-induced hydrologic forcing have an outsized biogeochemical influence within stratified coastal aquifers.

Response and resilience of karst subterranean estuary communities to precipitation impacts

“…This study provides insights into the effects of meteorological events on groundwater temperature within a KSE, with changes in groundwater temperature of half the magnitude than the interannual variation. Previous reports of changes in groundwater due to meteorological events have been related to tropical cyclones (Brankovits et al, 2022 ; Collins et al, 2015 ; Coutino et al, 2017 ; Kovacs et al, 2017 ). Evidence from the GAMM + precipitation shows that the groundwater is not only affected by extreme meteorological events.…”

“…Direct mortality (i.e., changes directly affecting fauna) could be a consequence of the drastic osmotic shock and temperature change brought in by the event (the day before when it was not possible to dive due to meteorological conditions). Available information of the variability of the environmental parameters is limited to temperature and water level, and information about the changes due to disturbances by severe weather is scarce (Brankovits et al, 2022 ; Collins et al, 2015 ; Coutino et al, 2017 ; Kovacs et al, 2017 ; Mejía‐Ortíz et al, 2020 ). Currently, no studies have been performed on the physiological tolerances of stygobiont species, or relatives at family level, present in Cozumel Island (Ballou et al, 2022 ).…”

“…Anthropogenic influences, such as groundwater pollution, water overexploitation, habitat destruction (i.e., quarrying of limestone), and alteration of adjacent ecosystems are of concern, and may lead to irreversible ecosystem change (Doehring & Butler, 1974 ; Iliffe, 2002 ; Mammola, Cardoso, et al, 2019 ). Meteorological events also appear to have an impact in the KSEs, with evidence of changes in temperature (Coutino et al, 2017 ; Kovacs et al, 2017 ), salinity (Coutino et al, 2017 ), water level (Collins et al, 2015 ; Kovacs et al, 2017 ), and oxygen (Brankovits et al, 2022 ) after tropical cyclones.…”

Diversity and bioprospection of Gram-positive bacteria derived from a Mayan sinkhole

“…This study focused on the bioprospection of cultivable Gram-positive bacteria isolated from sediment samples of the cenote Pol-Ac. In contrast to other coastal cenotes, Pol-Ac lacks a freshwater layer on its surface due to a surface salinity of 20.9 psu and a halocline at a shallow depth of only 0.4 m. For instance, the coastal cenotes Tábano [54] and Na'ach Wennen Ha [55], both within 1 km of the Caribbean Sea, have surface salinities of 2 psu and 0.5 psu, and much deeper haloclines at 11 m and 5 m, respectively. With an average water temperature of 26.4°C, Pol-Ac follows the trend of other coastal cenotes like Tabano and Odyssey [54] during this time of the year [5,56].…”

Diversity and Bioprospection of Gram-positive Bacteria Derived from a Mayan Sinkhole

“…This study focused on the bioprospection of cultivable Gram-positive bacteria isolated from sediment samples of the cenote Pol-Ac. In contrast to other coastal cenotes, Pol-Ac lacks a freshwater layer on its surface due to a surface salinity of 20.9 psu and a halocline at a shallow depth of only 0.4 m. For instance, the coastal cenotes Tábano [ 54 ] and Na’ach Wennen Ha [ 55 ], both within 1 km of the Caribbean Sea, have surface salinities of 2 psu and 0.5 psu, and much deeper haloclines at 11 m and 5 m, respectively. With an average water temperature of 26.4 °C, Pol-Ac follows the trend of other coastal cenotes like Tabano and Odyssey [ 54 ] during this time of the year [ 5 , 56 ].…”