The primary environmental factor affecting the distribution of marine species is temperature. Water temperature influences metabolic rates, reproduction, and feeding patterns of marine organisms. Many species have specific thermal tolerances and are adapted to certain temperature ranges. Changes in ocean temperature, caused by climate change, can lead to shifts in species distributions as organisms migrate towards preferable conditions. Other factors, including salinity, nutrient availability, and light penetration, also play roles, but temperature is often the most critical determinant in marine ecosystems.