I'm trying to find out if there is a significant correlation between salinity and no. of Bivalves found on a shore. I did a Spearman Rank and this was my result:

"There was a statistically significant correlation between Salinity and the number of Bivalvia individuals (Spearman Rank Correlation Coefficient, rs = 0.63, n = 40, P < 0.05)."

But then I did quadratic regression and it's saying it's not significant, with a P value of 0.267 !!

How can this be when my rs value is pretty close to +1?

Am I using the wrong tests?? If so, what do I use??

Many thanks