Izmit Bay, located in the Marmara Sea, is a highly important region in terms of aquatic ecosystems, marine transportation, shipping and industrial sector. Due to the residential areas and the industrial activities around the bay, this region is affected by both domestic and industrial wastes. In this study, the environmental relationships between the macro algae species Ulva rigida C. Ag., Enteromorpha sp., Gracilaria sp., Porphyra sp., Gelidium sp. and Ceramium sp. in the littoral zone of Izmit Bay and the heavy metals in the sea water (Al, Fe, Cd, Zn, As, Cr, Mn) were evaluated using the Canonical Correspondence Analysis (CCA). The same method was also used to evaluate the environmental relationships between these macro algae species and the sea water parameters, such as; NH4-N (mg/L), NO3-N (mg/L), NO3- (mg/L), PO4-P (mg/L), PO4-3 (mg/L), suspended solids (mg/L), Temperature (C-0), Conductivity (mu S/cm), Ph and Dissolved oxygen mg l(-1)). According to the Canonical Correspondence Analysis (CCA) results, the marine algae species and the heavy metals show that the correlation between the variables on the axis 1 was significant (p = 0.01). Enteromorpha sp., Gelidium sp., and Gracilaria sp. The distributions were positively correlated, especially with the heavy metals such as; As, Mn and Zn, whereas, the situation for Ulva rigida C. Ag. and Ceramium sp. was the opposite. On the other hand, Enteromorpha sp. and Gelidium sp., both showed positive correlations with the values of PO4-P and PO4-3, where Ulva rigida C. Ag. and Ceramium sp. showed a negative correlation with these parameters.