A species of marine arthropod lives in seawater that contains calcium in a concentration of 32 mmol/kg water. Thirteen of the animals are collected and the calcium concentrations in their coelomic fluid are found to be: 28, 27, 29, 29, 30, 30, 31, 30, 33, 27, 30, 32, and 31 mmol/kg. Construct an appropriate hypothesis test to conclude whether members of this species maintain a coelomic calcium concentration different from their environment. State your assumptions, rationale behind the statistic and critical values of the statistic for a significance level of = 0.01.