Diel Aquatic CO2 System Dynamics of a Bermudian Mangrove Environment

Abstract

Mangrove ecosystems play an important, but understudied, role in the cycling of carbon in tropical and subtropical coastal ocean environments. In the present study, we examined the diel dynamics of seawater carbon dioxide (CO 2 ) and dissolved oxygen (DO) for a mangrove-dominated marine ecosystem (Mangrove Bay) and an adjacent intracoastal waterway (Ferry Reach) on the island of Bermuda. Spatial and temporal trends in seawater carbonate chemistry and associated variables were assessed from direct measurements of dissolved inorganic carbon, total alkalinity, dissolved oxygen (DO), temperature, and salinity. Diel pCO 2 variability was interpolated across hourly wind speed measurements to determine variability in daily CO 2 fluxes for the month of October 2007 in Bermuda. From these observations, we estimated rates of net sea to air CO 2 exchange for these two coastal ecosystems at 59.8 ± 17.3 in Mangrove Bay and 5.5 ± 1.3 mmol m -2 d -1 in Ferry Reach. These results highlight the potential for large differences in carbonate system functioning and sea-air CO 2 flux in adjacent coastal environments. In addition, observation of large diel variability in CO 2 system parameters (e.g., mean pCO 2 : 390-2,841 latm; mean pH T : 8.05-7.34) underscores the need for careful consideration of diel cycles in longterm sampling regimes and flux estimates.

Community composition in mangrove ponds with pulsed hypoxic and acidified conditions

“…A similar occurrence was noted in Mangrove Bay, Bermuda, where Zablocki et al. () observed a diel range in pH of 0.71 units in a mangrove pond.…”

“…Our results suggest that diel cycling in DO and pH in mangrove ponds is a general phenomenon as we observed it in both mainland Panama sites and offshore islands in Belize. A similar occurrence was noted in Mangrove Bay, Bermuda, where Zablocki et al (2011) observed a diel range in pH of 0.71 units in a mangrove pond. We expected that physical characteristics of ponds would affect the magnitude of the diel cycle.…”

Effects of pCO2 on the interaction between an excavating sponge, Cliona varians, and a hermatypic coral, Porites furcata

“…CO 2 -enriched seawater from mangrove habitats is then tidally exported to adjacent environments before being mixed and diluted. Zablocki et al (2011) found that the maximum diel range of pCO 2 in mangrove habitats of Bermuda was from 268 to 4,823 μatm, far beyond the range experienced in a controlled experiment designed to manipulate pCO 2 at certain target levels. The pCO 2 values at Isla Pastores ranged from 213 to 430 μatm; however, measurements were taken weekly during the mid-morning hours, and therefore, a full diel range is not represented by these data.…”

“…The P. furcata fragments used in this experiment were collected from a reef tract on Isla Pastores that, like most reefs inside the archipelago of Bocas del Toro, Panama, lies directly adjacent to a large mangrove habitat (<10 m distance). Mangrove habitats typically experience large diel variations in pCO 2 and temperature due to the shallow waters and high level of organic matter decomposition within the sediments (Borges 2003;Zablocki et al 2011). CO 2 -enriched seawater from mangrove habitats is then tidally exported to adjacent environments before being mixed and diluted.…”

Groundwater‐derived dissolved inorganic and organic carbon exports from a mangrove tidal creek: The missing mangrove carbon sink?

“…Groundwater-derived carbon export-Previous studies have documented an inverse relationship between tidal height and DIC Kristensen et al 2008b;Zablocki et al 2011) and DOC (Lara and Dittmar 1999;Dittmar and Lara 2001) concentrations in mangrove creeks. It has been hypothesized that this tidal variation is driven by the input of groundwater enriched in DIC and DOC during the ebb tide (Dittmar and Lara 2001; Bouillon et al 2007b), with connectivity between groundwater and surface water enhanced in mangroves because of the mosaic of macrofauna burrows and organic-rich sediment layers (Ridd 1996;Mazda and Ikeda 2006).…”