2.10.1 What is aquatic plant biomass?

Aquatic plant biomass is produced in freshwater and marine environments and has some potential human uses. Most current aquatic plant biomasses include seed plants, seaweeds and micro-algae, which are mostly produced naturally as well as some with man-made culture production.

Seed plant biomasses in freshwater are a water plant (Eichihornia crassipes (Mart.) Solms) and duckweeds. E crassipes native to Brazil grows actively at 18-32 oC but shows no positive growth above 34 oC and below 0 oC. No duckweed species including about 30 species recorded has been selected as biomass utilization yet.

Within 60 species belonging 13 genera of 3 families (Hydrocharitaceae, Zosteraceae and Cymodoceaceae) as marine seed plants (sea grasses) in the world, eel grass (Zostera marina L.) and related species distributing at middle and high latitudes attract mostly for biomass uses (Hartog, 1970).

Algae include multi-cellular macro-algae (seaweeds) and unicellular micro-algae (phytoplankton). Seaweed inhabits, mostly in seawater and active biomass utilization is made with 220 species of red algae, 88 species of brown algae and 27 species of green algae in the world (Indergaard, 1982).

Micro-algae are distributed widely both in fresh — and marine waters although species are different. Current attractive species for biomass are green algae belonging Chlorella, Scenedesmus and Dunaliella and blue green alga of Spiriluna in freshwater. Selected strains are cultured artificially for biomass uses, and some freshwater strains are cultured in seawater after acclimation treatment.