A study of hypoxia and ocean acidification related physico-chemical parameters in selected coastal waters around Mauritius

Abstract

Sea water samples were collected at five stations around Mauritius namely Flic-en-Flac, Albion, Mont Choisy, Trou-d’Eau-Douce and La Cambuse over 12 months from July 2021 to June 2022 for the analysis of dissolved oxygen (D.O), pHT and Total alkalinity (AT). Albion was the only open water system whereas the others were lagoons. Summer was from November 2021 to April 2022 while the period from July 2021 to October 2021, May 2022 and June 2022 were considered to be winter. The summer mean values of sea surface temperature (SST), D.O, pHT and AT varied from 28.2 ± 1.3°C to 29.8 ± 2.2°C, from 6.60 ± 1.15 mgL−1 to 8.11 ± 0.51 mgL−1, from 8.10 ± 0.09 to 8.20 ± 0.12 and from 2324.5 ± 110.6 μmol kg−1 to 2384.8 ± 118.6 μ mol kg−1, respectively. The winter mean values of these parameters varied from 24.7 ± 1.1°C to 26.1 ± 1.4°C, from 6.55 ± 1.21 mgL−1 to 8.26 ± 0.67 mgL−1, from 8.00 ± 0.08 to 8.13 ± 0.14 and from 2397.2 ± 84.9 μmol kg−1 to 2448.7 ± 108.5 μmol kg−1, respectively. The Two-way measures ANOVA and the post hoc analysis revealed that (1) the only two stations having a comparable mean pHT variability in the two seasons were Albion and La Cambuse, despite having opposite bearings and morphology, but their mean D.O variability was the contrary (2) the mean temporal variability in D.O and pHT at Mont Choisy were not significant due to the presence of sea grasses.