Pleurosigma pacificum is a species of planktonic diatom discovered in the tropical Western Pacific Ocean.

[2] In particular, naviculoid diatoms of the genus Pleurosigma usually have a sigmoid valve or raphe, in the shape of a sigmoid function or the letter S.[3] The species P. pacificum is characterized by lanceolate valves, around 45.0–51.1 μm long and 13.0–15.6 μm wide, that taper gradually towards subacute ends.

[1] Pleurosigma pacificum is a planktonic unicellular alga known only from its type location, in the Pacific Ocean.

Its DNA was sequenced and, through phylogenetic analyses based on two genes, SSU rDNA and rbcL, its taxonomic position within the genus Pleurosigma was confirmed.

The species was described by researchers Fei-Chao Du, Yu-Hang Li and Kui-Dong Xu of the Chinese Academy of Sciences.