Data from: Invertebrate holobionts contribute to methane release from coastal ecosystems

In this study, we incubated 103 animals specimens equivalent to 19 macrofaunal species to quantify holobiont-associated methane (CH₄) fluxes and metabolic processes [oxygen (O₂) - respiration and ammonium (NH₄⁺) - excretion rates]. The specific goals were to quantify holobionts CH₄ production/uptake and to establish correlations between CH₄ fluxes and environmental factors (e.g., salinity).

Invertebrates were collected in 4 coastal systems and incubated in 22 mL glass microcosms filled with 0.22 µm twice-filtered in situ water. Individual and Mass-standardized CH₄ Production Rates (IPR and MPR, respectively), O₂ Respiration Rates (IRR and MRR) and  NH₄⁺ Excretion Rates (IER and MER) were measured in 103 animals’ incubations.

1. IRR were calculated from linear regression analysis of the solute (O₂) versus time equation: 

       \(IRR=(Reg.Slope × V)/N\)

       where IRR (µmol O₂ ind.⁻¹ day⁻¹) is the respiration of the chemical species O₂; Reg.Slope is the slope of the regression (µmol O₂ L⁻¹ day⁻¹); V (L) is the water volume in the glass microcosm; N is the number of incubated animals per microcosm.

2. IER and IPR were calculated from the difference in concentrations (NH₄⁺ and CH₄) in the water using the equation:

        \(IER and IPR =((C_f-C_i )×V)/(N×t)\)

        where IER and IPR (µmol ind.⁻¹ day⁻¹ and nmol ind.⁻¹ day⁻¹) are the excretion or production of the chemical species (NH₄⁺ or CH₄); C_f and C_i (µmol or nmol L⁻¹) are the final and initial concentrations of the chemical species; V (L) is the water volume in the glass microcosm; N is the number of incubated animals per microcosm; and t (days) is the incubation time. Positive values represent productions while negative values represent uptake.

Same equations were used to calculated mass-standardized rates, but instead of N the total animal biomass (g_dw) was used. Animals’ biomass was determined as dry weight (DW) or as dry weight shell free (DWSF) for bivalves, after the desiccation at 70°C until constant mass. Water temperature and salinity were measured in situ with a multiple probe (556 MPS, YSI).  Rates are reported as average ± standard error.