在深海中，由有机物所组成的碎屑像雪花一样不断飘落，称作海洋雪。海洋雪主要由有机物碎屑所组成，起源于海洋上部透光层的有机物生产活动。

海洋雪的组成包括：已死或将死的动植物（浮游生物）、原生生物（如硅藻）、细菌、粪便颗粒、泥沙和尘土等。“雪花”（多成团或丝）是较小的颗粒被含多糖的黏性物质粘在一起形成的大的聚集体。这种多糖称作“透明胞外聚合物颗粒”（transparent exopolymer particles, TEPs），是由细菌或浮游生物产生的天然聚合物。随时间推移，这些聚集体直径可长到几厘米，需要几周时间才能飘到海底。

In the deep ocean, marine snow is a continuous shower of mostly organic detritus falling from the upper layers of the water column. It is a significant means of exporting energy from the light-rich photic zone to the aphotic zone below. The term was first coined by the explorer William Beebe as he observed it from his bathysphere. As the origin of marine snow lies in activities within the productive photic zone, the prevalence of marine snow changes with seasonal fluctuations in photosynthetic activity and ocean currents. Marine snow can be an important food source for organisms living in the aphotic zone, particularly for organisms which live very deep in the water column.