This calculation shows that burning grams of methane [takes in/gives off] energy.

Formula for heat change:   q = mcδtwhere 
q = the heat addedm = massc = specific heatδt=  (tf - to in absolute temperature) 
note: in this case subtracting the final and initial temperature in kelvin or celsius will not make a difference)
we add everything into the formula:   δt  = t(final) - t(original)
δt  = 36.65 - 24.85δt  = 11.8° cso the change in temperature is 11.8 degrees 

q = 41.11x  4.319 x 11.8 
q= 2095.13 heat of combustion of methane.
it shows that burning 41.11g of methane gives of 2095.13 joules of energy

Tolerance to high levels of salinity

The mass has escaped into a gas which you can not see so the law stays true.