Carbonate system variation evidences the effect of seasonality in carbon uptake in a tropical seagrass meadow of South Caribbean

doi:10.21203/rs.3.rs-4707952/v1

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Carbonate system variation evidences the effect of seasonality in carbon uptake in a tropical seagrass meadow of South Caribbean

https://doi.org/10.21203/rs.3.rs-4707952/v1

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We explore the variation of the carbonate system in the water column over a seagrass meadow under ecological restoration and its correlation with Net Primary Production (NPP), Net Calcification (NC) and Eutrophication, in a small coralline island within the Seaflower International Biosphere Reserve, Colombian Caribbean. We assessed one point within seagrass and another devoid of seagrass, during dry and rainy seasons. Dry season was characterized by higher levels of pH_T (total scale), descending levels of Dissolved Inorganic Carbon (C_T) along the day, and net fluxes of carbon towards the ocean. Rainy season presented lower pH_T values and carbonate variables not correlated with hour in the meadow, while the area presented fluxes of CO2 towards the atmosphere. NPP in the rainy season decreased by 39% in the point without seagrass and by 95% in the seagrass respect to dry season. NC in the meadow registered values 3.2x higher in dry season than in rainy season. These phenomena evidenced a shift in NPP from seagrass to water column, a strong remineralization process, and loss of sheltering function for calcifying organisms localized in the meadow during rainy season. These findings coincide with previous evaluations in the island, which have shown lower rates of seagrass growth and organic carbon accumulation in sediment during rainy season. Possible explanations include carbon import from adjacent ecosystems and influence of cultural eutrophication. Our results suggest the importance of runoff and eutrophication control to protect carbon sequestration ability and improve the outcome of ecological restoration processes in tropical seagrasses.

Carbon sequestration

blue carbon

calcification

eutrophication

Thalassia testudinum

Caribbean Sea

The dissolution of CO₂ in oceanic water releases hydronium (H⁺) ions, which leads to a decrease in pH and shifting of chemical equilibrium in carbonate system, including CaCO₃ minerals such as calcite and aragonite. This set of phenomena are denominated as ocean acidification (Zeebe & Wolf-Gradow, 2001) and are enhanced by the massive influx of anthropogenic CO₂ into the ocean. Ocean acidification is predicted to impact directly all levels of the food chain and ecological processes in the ocean, with special emphasis in the photic and productive zone of the ocean, where most of the biological processes take place (Hofmann & Schellnhuber, 2009). Studies have reported mostly negative effects on key ecological processes such as the biologic pump (Basu & Mackey, 2018; De La Rocha & Passow, 2007), the availability of calcareous sediments on beaches (Simeone et al., 2018), the predator-prey interactions (Seroy & Grünbaum, 2018), or the physiological responses to pollution (Cao et al., 2018; De Marchi et al., 2019).

In coastal zones, fluxes of inorganic carbon trend to be highly variable over very short spatial and temporal scales (Sutton et al., 2016) and pH variations can reach the range of 0.3–0.5 units throughout the year (Duarte et al., 2013; Hendriks et al., 2015), which exceeds by several orders of magnitude the anthropogenic signal of acidification in the open ocean (Bates et al., 2014). Therefore, assess the potential of coastal ecosystems as modulators of ocean acidification and carbon sinks is a very active area of research. Both functions have been extensively characterized for seagrass meadows (Hendriks et al., 2014), macroalgae "forests” (Becherucci et al., 2021), mangrove forests (Sippo et al., 2016), and coral reefs (Anthony et al., 2013), but the natural variability of these systems makes it considerably difficult to extrapolate parameters between different locations (Van Dam et al., 2021). Changes in the pH of coastal zones respond to many forcing factors not necessarily related to ocean acidification, such as the flow of nutrients, environmental and land use transformations in continental basins, and changes in the structure and metabolism of the coastal ecosystems (Carstensen & Duarte, 2019; Duarte et al., 2013). Among the biological variables, the ability of photosynthesis to act as a pH buffer has been demonstrated: in eutrophic waters a high correlation between pH and chlorophyll-a has been found, but in very oligotrophic waters this capacity can be transferred to seabed photosynthesizers.

Seagrass meadows are considered strategic in climate change mitigation due to their high capacity for carbon capture and sequestration (Herr & Landis, 2014b; McLeod et al., 2011). For those ecosystems, although a higher concentration of CO₂ could increase the photosynthetic efficiency of the seagrass, the disappearing of calcifying communities (e.g., epiphytic crusted algae, mollusks, or echinoderms) could lead to a loss of structural complexity with a potential negative impact over the ability of seagrass meadow to provide ecosystem services (Zunino et al., 2019). The consensus on the effectiveness of seagrass meadows as carbon sinks relies in one of these assumptions: 1. inorganic carbon stored in them has an allochthonous origin (Saderne et al., 2019), or 2. calcification is widely surpassed by primary net production (Mazarrasa et al., 2015). However, the fluxes from the carbonate system to the sediment carbon pool are far from being simple. The biogeochemical cycles and other processes occurring in the meadow affect biomass growth and nutrient fluxes in complex ways. Precipitation of one unit of CaCO₃ results in the release of an additional 0.6 units of CO₂ into the atmosphere due the loss of alkalinity resulting from the carbonate precipitation, and the re-adjustment of carbonate equilibrium that releases additional H⁺ from bicarbonate (Ware et al., 1992), partially offsetting the carbon capture and pH control provided by net primary productivity. Although global balances on seagrasses trend to favor the preponderance of net primary production over calcification (Saderne et al., 2019), regional variations still need to be quantified. In meadows with high grades of recirculation calcification could take mainly autochthonous material as substratum. Under this scenario, calcification – in conjunction with other phenomena such as seafloor erosion, anaerobic decomposition, or eutrophication – could nullify or even reverse the effect of biological CO₂ fixation, turning a seagrass meadow into a net source of CO₂ into the atmosphere (Van Dam et al., 2021), and this effect could be accentuated in tropical and subtropical latitudes due to the elevation of the aragonite saturation index as effect of higher temperature and salinity (Mazarrasa et al., 2019). Simultaneously, adjacent ecosystems – such as coral reefs – can exert a protective effect on the seagrass that increases the efficiency of carbon sequestration in meadows (Guerra-Vargas et al., 2020), but those ecosystems will face their own complex scenarios driven by climate change (Zunino et al., 2019). Therefore, the response to environmental changes of each seagrass meadow is likely to be highly variable and dependent on local and regional conditions. It is necessary to deepen research efforts aimed at understanding and modelling the physical and biogeochemical cycles that regulate carbon transfer in seagrass meadows, especially those selected as models for ecological restoration, blue carbon initiatives, protection of coastal communities, or any other program implied in the framework of Nature Based Solutions (e.g. do Amaral Camara Lima et al., 2023; Jacob et al., 2023; Rifai et al., 2023).

In this work we evaluated the effect of the carbonate system in adjacent water masses on organic carbon accumulation in seagrass beds, addressing the following research question: How does the carbonate system vary at different timescales in water bodies associated with seagrasses, ecosystems recognized for their high accumulation of OC? As a working hypothesis, we proposed that seagrass would exert a buffering effect on the carbonate system, demonstrable trough higher levels of pH and/or Total Alkalinity, lower levels of Dissolved Inorganic Carbon and a quantifiable difference in the fluxes of carbon between ocean and atmosphere in the meadow area.

a. Area of Study

San Andrés is a coralline oceanic island located in the Caribbean Sea between 12°35'41"N – 12°28'49"N and 81°41'14"W – 81°44'08"W, with an approximate area of 27 km² and a population of approximately 55,000 (DANE, 2019; IGAC, 1986). It has a tropical monsoon climate and a precipitation regime typically monomodal, with an average annual of 1884 mm, characterized by a well-marked dry season in January – April and a scattered rainy season which peaks in October – December, when 80% of the mean annual rainfall occurs. The island is part of the Seaflower Biosphere Reserve, and it is characterized by a) the predominance of oceanic conditions, and b) the limited supply of drinking water, including the absence of permanent freshwater streams, although runoff can occur in the rainy season and/or by influence of human activity (Gavio et al., 2010). The island has about 400 hectares of seagrass, mainly distributed within the reef lagoon basin at north-east of the island. Thalassia testudinum is the dominant specie up to 4 m depth, while Syringodium filiforme is widespread at depths between 7–10 m. The island's meadows usually have an important algae component dominated by the genera Halimeda, Penicillus, Caulerpa and Avrainvillea. At least 22 species of fish, 20 species of mollusks, 16 species of sponges and 13 species of crustaceans have been found in the meadows (Diaz et al., 2003).

b. Carbonate system sampling

Three sampling campaigns were performed in San Andrés Island during two contrasting periods: mostly dry season (June 2022) and peak of rainy season (November 2019 and September 2022). In each one, two locations were sampled: a point within a seagrass meadow in process of ecological restoration, and a point without seagrass. Both points were in the East coast of the island, inside the coral lagoon and adjacent to a dense mangrove forest (Fig. 1). For each location three daily samples (morning, noon, and afternoon) were taken during 3–5 days per campaign using a 5-l Niskin bottle operated by divers, the closest possible to seagrass canopy when the sample was taken in meadow. Sea Surface Temperature (SST) and Sea Surface Salinity (SSS) were taken in situ with SCHOTT Conductivity meter - Handylab LF 12 multiprobe. 250 ml were collected in borosilicate glasses to determine Total Alkalinity (A_T) and Dissolved Inorganic Carbon (C_T) (Bernal et al., 2021a; Bernal et al., 2021b). Once per day, 500 ml samples were collected to determine dissolved inorganic nutrients: Nitrate + Nitrite, Ammonium, Reactive Phosphorus measured as Orthophosphates (Strickland & Parsons, 1972), and Silicates (UNESCO, 1983).

c. Carbonate System Calculation

CO2Sys v2.1 in Excel (Pierrot et al., 2006) was used to find the variables of carbonate system derived from C_T and A_T (pCO₂, pH_T). Constants K₁ and K₂ of Mehrbach et al. (1973) adjusted by Dickson & Millero (1987), K HSO₄⁻ by Dickson (1990), Boron concentration by Uppström (1974), and pH_T scale (Zeebe & Wolf-Gradow, 2001) were selected. CO₂ fluxes (F_CO2) were calculated with the simplified Eq. (1), as reported in Wanninkhof (2014):

$$\:{F}_{{CO}_{2}}=7.7\times\:{10}^{-4}\bullet\:\left({U}^{2}\right)\bullet\:\varDelta\:p{CO}_{2}$$

(1)

Where F is given in mol/m²∙y; ΔpCO₂ = pCO_2(water) - pCO_2(atm) expressed in µatm; and U is the wind speed at 10 m above the surface in m/s. Wind speed was obtained from monthly averages of Gustavo Rojas Pinilla Airport station (Code: 1701501) reported by IDEAM (2023), and atmospheric CO₂ concentration was obtained from monthly global values estimated by Global Monitoring Laboratory (NOAA, 2023).

Figure 1 Location of the seagrass meadow point, and bare sand point sampled within San Andrés Island.

d. Residue Analysis: ΔC_T and ΔA_T Method

Linear correlations A_T vs. SSS and C_T vs. SSS were performed to reduce the variability associated with conservative phenomena in which salinity can be used as a proxy. Residuals of A_T (ResA_T) and C_T (ResC_T) were obtained. Spearman's rho coefficients for A_T, C_T, ResA_T, and ResC_T vs. Hour, and linear regressions were obtained for each pair. A standard unit of 1m² of meadow at a depth of 2 m was taken to transform the change in concentrations of the different chemical species into flows per unit area. Therefore, the contribution of each process can be determined using the following system of linear equations (2).

$\:\:\:\:\:\varDelta\:{C}_{T}\:+\:{F}_{{CO}_{2}}\:=\:-\:x\:-\:y$ $\:\:\:\varDelta\:{A}_{T}\:=\:Kx\:-\:2y$

Where Δ represents the daily change of C_T and A_T (10-hour period), x is the Net Primary Productivity (NPP), and y is the Net Calcification (NC). Values for Δ C_T and ΔAT were obtained from linear regressions and daily values of F_CO2 were the mean values of the timespan. By convention, the positive sign of F_CO2 went towards the atmosphere. K coefficients were estimated fromMiddelburg et al. (2020) considering the source of N in NPP was proportional to ratios of NH₄⁺ and NO₃⁻ concentrations. When NH₄⁺ or NO₃⁻ were under limit of quantification, the other ion was considered the only source of N.

e. Statistical analysis

Shapiro-Wilk and Levene tests were used to evaluate the normality of data and homogeneity of variances, respectively. ANOVA tests were performed for A_T, C_T, pCO₂, pH_T, ResA_T, and ResC_T to evaluate significant differences between seagrass and point without seagrass within the same campaign, and between different campaigns within the same point. In cases where more than two groups were analyzed, paired Wilcoxon test was used to assess differences between pars. R² coefficients and Spearman coefficients were obtained to evaluate the significance of correlations.

C_T and pCO₂ in the seagrass were lower in the dry season of June 2022 than in the rainy season of November 2019 (ANOVA: p = 0.026; Mann-Whitney: p = 0.062). pH_T in the seagrass was lower in the rainy season of November 2019 than in June 2022 (ANOVA: p < 0.001; Mann-Whitney: p = 0.001), while pH_T in the point without seagrass behaved similarly, but showed less marked differences (ANOVA: p = 0.056). A_T was higher in June 2022 than in September 2022 in the seagrass (ANOVA: p = 0.034; Mann-Whitney: p = 0.029) and the point without seagrass (ANOVA: p < 0.001) and was higher in the seagrass during September 2022 in relation with point without seagrass (ANOVA: p = 0.002). Direction of CO₂ fluxes went towards the sea in both sample points during dry season of June 2022. During the rainy season an opposite condition was found, with fluxes behaving near neutrality in September 2022 and pointing towards the atmosphere in November 2019. (ANOVA in seagrass: p < 0.001; ANOVA in point without seagrass: p = 0.082). The main variables of the carbonate systems are shown in Fig. 2.

C_T, pH_T and pCO₂ were highly correlated with sampling Hour for June 2022 both in seagrass and no seagrass points (Spearman coefficient: C_T: -0.809, pH_T: 0.809 and pCO₂: -0.809 for Seagrass; C_T: -0.738, pH_T: 0.857 and pCO₂: -0.899 for No Seagrass; p < 0.02 in all cases). pH_T and pCO₂ showed significative correlation with Hour in September 2022 at point without seagrass point (Spearman coefficient: 0.869 and − 0.899 respectively; p < 0.05 in all cases). No one of the campaigns at rainy season showed correspondence between Hour and variables of carbonate system in the seagrass. C_T in September 2022 showed relative high correlation at point without seagrass, but less marked than in June (Spearman: -0.753, p = 0.08). ResC_T were highly correlated with Hour in June 2022 (Spearman coefficient: Seagrass: -0.809; No seagrass: -0.738; p < 0.05 in both cases) and for September 2022 in the point without seagrass (Spearman coefficient: -0.754; p = 0.08) (Fig. 3).

During rainy season all values of ammonium were under the limit of quantification during June 2022. Reactive phosphorus only showed values above the limit of quantification during November 2019. Nitrites and Nitrates were under limit of quantification in the point without seagrass in June 2022. The seagrass point in June 2022 was the only point where values of both reduced and oxidized nitrogen were registered. Variability of silicates was higher during the rainy season, with peaks near twice the mean values (Fig. 4).

The results suggest that NPP was higher around June and decreased as the rainy season advanced. This behavior was repeated in both the 2019 and 2022 campaigns. The seagrass showed a very low (or even negative) NPP in both rainy seasons of 2019 and 2022, being the values at point without seagrass more like the ones in dry season. NC rates were low at all stations except for seagrass during June 2022. NC rates in seagrass trend to be around one order of magnitude lower than NPP values (Fig. 5).

The net carbon transport between the meadow, the sand banks, and other ecosystems could not be considered in this research but has been extensively explored in literature. Akhand et al. (2021) found that mangroves can act as a net exporter of A_T, C_T, and dissolved organic carbon (DOC) to adjacent ecosystems when they share a continuous space with seagrasses and coral reefs. In this scenario, seagrass meadows behaved as a net source of carbon in the form of C_T, dissolved OC and particulate OC, and the remineralization of allochthonous organic matter (OM) was an important source of C_T, especially when freshwater runoff is available. Other studies have reported that seagrass meadows are particularly efficient at capturing exogenous organic matter which can enhance remineralization processes in both the canopy and the sediment (Bouillon et al., 2004, 2007; Chen et al., 2017). Those studies were carried out on continental coasts or big islands, where the amount of freshwater from inland is considerable, while San Andrés Island is a small insular system without permanent freshwater currents, so these conclusions cannot be directly extrapolated into this research. However, our results suggest a strong process of remineralization of OM in the meadow during rainfall maximum, which was not present in the dry season. Monitoring carried out in the mangrove area of Hooker Bay, less than 1 km from this study, have found historical salinity averages lower than the mean oceanic values with sporadic extremes in the range of estuarine waters, accompanied with the highest average total OC averages on the island (Ibarra et al., 2023), and low levels of water quality for a multivariate indicator composed by fecal coliforms, total suspended solids, BDO, ammonium, nitrate, and phosphorus (Abdul azis et al., 2018) during the rainy season. In contrast, Gavio et al. (2010) found nitrogen and phosphorus concentrations to be lower during this season, which was attributed to a greater dilution by runoff from land, the uptake of nutrients by other primary producers, and a shorter water residence time within the reef lagoon. Under these circumstances, accumulation of remineralizable carbon from mangroves in seagrass meadow is feasible. A scenario with a higher concentration of organic carbon (OC) coupled with a Gross Primary Productivity (GPP) partially limited by nutrients available for the seagrass bed would be consistent with a diminishing NPP in the meadow. A plausible mechanism for this flux between ecosystems is the carbon transport through Suspended Solids, which have been reported to reach concentrations up to 10x during the rainy season in relation with the dry season (Bernal Glen, 2024).

Photosynthesizing organisms can take up nitrogen in different oxidation states, while decomposition releases ammonium compounds Middelburg et al. (2020). Although this consideration introduces uncertainties in our calculations for the fraction of ΔA_T corresponding to NPP, our results suggest that the contribution of Net Calcification (NC) on the carbonate system variation is low, considerably less than NPP contribution. Van Dam et al. (2021) have demonstrated that magnitude of calcification may mask or exceed photosynthetic carbon capture when calcification takes autochthonous material as substrate. We did not find this behavior during the study, although meadows at San Andrés Island have abundant epiphytic photosynthetic calcifiers, such as Hydrolithon farinosum and Pneophyllum fragile (Albis-Salas & Gavio, 2015). NC and NPP influence each other: the seagrass canopies provide structural complexity and shelter for a wide variety of calcifying organisms that modify the flows of matter and energy within the meadow (Heck et al., 2008). Estimated NC was higher in the seagrass than in the point devoid of seagrass during June 2022. This scenario is compatible with a higher presence of calcifiers in the seagrass meadow when compared to adjacent sand banks. The pH_T values in the samples did not show significant differences between those points, but there are other mechanisms, different from direct influence on pH in the water column, capable of enhance the presence of calcifiers in the seagrass. Hurd (2015) explored the conditions provided by submerged canopies (both macroalgae and seagrass) and found the following protective elements against ocean acidification: 1. The own metabolism of seagrass or macroalgae could exert a modulation of ions such as OH⁻, NH₄⁺, NO₃⁻, Ca²⁺ or molecules such as NH₃; 2. A boundary layer of variable thickness could be formed within and over the canopy can sustain a microcosm with chemical properties and concentration gradients different from the surrounding water. 3. Higher pH fluctuations between day and night could lead to metabolic adaptations of living organisms. Further studies need to be carried to know the extent and diversity of calcifiers in San Andrés Island meadows and the role of the seagrass on its shelter.

Values of 1.47 ± 0.80% for OC have been found in seagrass meadow sediments in San Andrés Island, and isotopic analysis of δ^13C estimated that up to 47% of the OC deposited in the sediment originated in blooms of the macroalgae Halimeda tuna, with the remaining percentage being divided equally between the seagrass and the seston (Serrano et al., 2021). This supports the hypothesis that allochthonous carbon fluxes have significant effect over the carbon cycles in the meadow, although the contribution of mangrove forests was not evaluated. Halimeda sp. species are also calcifying algae, and high NPP have been reported for those species when grow in the coral reefs of the island (Serrano et al., 2021). Therefore, they could have a significant influence on the organic and inorganic carbon cycles in the Caribbean shallow waters, which is yet to be determined. The content of aboveground biomass and belowground biomass in this meadow was considerably lower than those reported for mature meadows in the island. Values reported for this meadow were 0.59 MgC/Ha aboveground and 0.52 MgC/Ha belowground (Bernal Glen, 2024). In contrast,Guerra-Vargas et al. (2020) have found average contents of up to 1.0 MgC/Ha aboveground and up to 5.3 MgC/Ha belowground. They also found that total seagrass biomass and Thalassia testudinum biomass, both aboveground and belowground, were consistently higher during the dry season. Those findings support our hypothesis that uptake of C_T could be impaired during rainy season, which reflects on the growth rate of seagrass, the ability of the meadow for the accumulation of OC, and the higher remineralization rates at the peak of the rainy season.Vega Rojas (2020) found that Thalassia testudinum meadows growing in estuarine conditions (high turbidity in water and high OM concentration in the substrate) had lower rhizoidal biomass than their counterparts growing in "insular" conditions (high transparency, calcareous sediments), and leaf growth of the “insular” meadows was also higher during the dry season, although both data should be used with caution due to the differences between both locations.

Cultural eutrophication could also have an impact on the observed behavior.Jaax et al. (2024) estimated that a mean of 1,000 kg/day of nitrogen are injected into the sea and other 750 kg/day into the soil of San Andrés Island (with potential affectations over groundwater) only due to sewage discharge. Our own results did not detect high concentration of nutrients in most of the samples, so it is very probable that a rapid uptake by photosynthetic organisms is occurring, as was reported by Gavio et al. (2010). Increment in nutrient loads in coastal shallow waters can result in a shift in the ecosystem state towards the dominance of phytoplankton and macroalgae biomass in detriment of seagrasses(McGlathery et al., 2007) that could be irreversible beyond certain limit (Scheffer et al., 2001). The effects of eutrophication on OC storage in seagrasses have different manifestations. For example,Luo et al. (2024) reported that nitrogen loads are capable of impair the formation of refractory organic compounds in seagrass, andGillis et al. (2019) have found that effluent from shrimp farms can reduce root growth and fine roots biomass in other blue carbon ecosystems such as mangroves, where fine roots have higher carbon contents and are generally associated with higher amounts of accumulated sedimentary OM (Huxham et al., 2010). As a result, carbon fluxes could be reconducted from the seagrass meadow to more labile, remineralizable organic compounds characteristic of phytoplankton and fleshly algae (Basu & Mackey, 2018; Krause-Jensen et al., 2021). Both alternatives are compatible with a diminishing C_T uptake and OC sequestration during the rainy season. Loss of calcification capacity in the meadow during the rainy season (compared with dry season) could be an early sign of loss of capacity to provide ecosystem services – shelter for calcifying organisms, in this case – in presence of eutrophication and low pH, as described by Zunino et al. (2019). Implicitly, we could hypothesize that control of eutrophication and improvement of sewage systems in San Andrés and other Caribbean islands could exert a protective effect over the seagrass and mitigate the loss of OC during the rainy season. This consideration should be afforded in blue carbon and ecological restoration programs.

Further studies are required to clarify whether other factors are contributing to this drop in NPP rates and OC accumulation during rainy season. Although we estimated the bulk inorganic fluxes, the relative contribution of gross primary production, respiration, calcification and carbonate dissolution still need to be evaluated for each one of the components of the meadow ecosystem: seagrass, phytoplankton and macroalgae. It is expected that differential response to climate variability, seasonality and nutrient fluxes can be found in each of these components. Additionally, fluxes between adjacent ecosystems – such as the mangrove forests and the coral reefs – still need to be quantified to assess the entire panorama of carbon exchange in the seagrass meadows of San Andrés Island.

Carbon uptake by seagrass meadow and water column has a strong seasonal component characterized by low NPP and high remineralization rates during the peak of rainy season, which impacts the ability of the meadow for OC sequestering. Evidence suggests that these high remineralization rates are influenced by organic and inorganic carbon fluxes between seagrass meadow and adjacent ecosystems, and cultural eutrophication. Cultural eutrophication potentially has a negative impact over the ability on the growth and OC sequestration in the meadow, which makes necessary to include this factor in the assessment of blue carbon potential of the area.

Competing interests

This research was carried out under the project "Seagrass Restoration as Mitigation of Ocean Acidification in the Caribbean Region – Blue Carbon Restoration", financed by The Ocean Foundation, 1320 19th St, NW, Suite 500, Washington, DC 20036. (202) 887-8996.

Acknowledgements

This research was carried out under the project "Seagrass Restoration as Mitigation of Ocean Acidification in the Caribbean Region – Blue Carbon Restoration", developed by Universidad Nacional de Colombia, and financed by The Ocean Foundation. Hermes code 46559. Technical support was provided by Instituto de Investigaciones Marinas y Costeras “José Benito Vives de Andréis” – INVEMAR..

Authors contribution

Daniel Bernal-Glen and José Mancera-Pineda conceived the research question and working hypothesis; José Mancera-Pineda and César Bernal designed the methodology and lead the fieldwork. César Bernal performed the laboratory analysis of the samples; Daniel Bernal-Glen performed the data revision and statistical analysis. All authors contributed critically to the writing of the document and gave their final approval for publication.

Data availability

Once the article be accepted, data and calculation memories will be available at the Figshare Digital Repository: https://doi.org/10.6084/m9.figshare.26064457

During review process, data will be accessible through the following private link: https://figshare.com/s/eadd94f40a4e75a9fd7f

Date of submission

This document will be submitted on July 8^th, 2024.

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Carbonate system variation evidences the effect of seasonality in carbon uptake in a tropical seagrass meadow of South Caribbean

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