So you have different measurements of species numbers at this location in each season, I guess? In this case you should better use a Poisson-regression model (since you have count data) with the categorical predictor "season" and the species number as the outcome. But do'nt you have the problem that the species abundance changes continuously with the time of year rather than changing suddenly with the season? In this case your data could show temporal autocorrelation, which has to be considered within the regression model.