Tropical Seagrass Identification (Seagrass-Watch)

Cymodocea rotundata (CR)

• Flat, strap-like leaves 2-4mm wide
• Rounded, smooth leaf tip
• Smooth rhizome
• Scars from well developed leaf sheaths form a continuous ring around the stem
• Found on shallow reef flats

Cymodocea serrulata (CS)

• Linear strap-like leaves, 5-9mm wide
• Serrated leaf tip
• Leaf sheath is broadly triangular with a narrow base
• Leaf scars do not form a continuous ring around the stem
• Found on shallow subtidal reef flats and sand banks

Enhalus acoroides (EA)

• Very long ribbon-like leaves 30-150 cm long
• Leaves with inrolled leaf margins
• Thick rhizome with long black bristles and cord-like roots
• Found on shallow/intertidal sand/mud banks (often adjacent to mangrove forests)

Halodule pinifolia (HP)

• Fine, delicate leaves up to 20cm long
• 1 central vein
• Black central vein splits into two at the rounded leaf tip
• Usually pale rhizome, with clean black leaf scars
• Found on intertidal sand banks

Halodule uninervis (HU)

• Usually larger than Halodule pinifolia
• Trident leaf tip
• 1 central longitudinal vein
• Rhizome usually pale ivory, with clean black leaf scars
• Dugong preferred food
• Found on shallow/intertidal sand or mud banks

Halophila capricorni (HC)

• Small oval leaves that are hairy on one side
• Central vein on leaf with 9-14 cross veins
• Usually found deeper than 10m in coral environments proximal to coral reefs
• Only found in subtidal Australian waters (>10m) proximal to coral reefs 

Halophila decipiens (HD)

• Small oval leaf blade 1-2.5cm long
• 6-8 cross veins
• Leaf hairs on both sides
• Leaves usually longer than wider
• Found at subtidal depths (>10m)

Halophila ovalis (HO)

• Oval shaped leaves in pairs
• 8 or more cross veins
• No hairs on leaf surface
• Preferred dugong food
• Common early colonising species
• Found from intertidal to subtidal depths

Halophila minor (HM)

• Less than 8 pairs of cross veins
• Small oval leaves occurring in pairs
• Wedge-shaped leaf sheath
• Found on shallow/intertidal sand flats

Halophila spinulosa (HS)

• Fern like
• Leaves arranged in opposite pairs
• Erect shoot up to 15cm long
• Found at subtidal depths (>10m)

Halophila tricostata (HT)

• Erect shoots 8-18cm long
• Leaves with 3 veins
• 2-3 leaves at each node
• Leaves “whorl” around stem
• Found at subtidal depths (>10m)
• Endemic to Queensland, Australia 

Syringodium isoetifolium (SI)

• Cylindrical in cross section (spaghetti like)
• Leaf tip tapers to a point
• Leaves 7-30cm long
• Found on shallow subtidal reef flats and sand banks

Thalassia hemprichii (TH)

• Short black bars of tannin cells in leaf blade 
• Thick rhizome with scars between shoots
• Hooked/curved shaped leaves
• Leaves 10-40cm long
• Common on shallow reef flats

Thalassodendron ciliatum (TC)

• Cluster of ribbon-like curved leaves at the end of an erect stem
• Round, serrated leaf tip
• Tough, woody rhizomes with scars from successive shoots
• Very coiled, branched roots
• Typically found in rocky areas with strong reef crests

Zostera capricorni (ZC)

• Long strap-shaped leaves