Meadow maintenance, growth and productivity of a mixed Philippine seagrass bed

Abstract

Leaf product~on, shoot demography and rhlzome growth and branchlng were quantified for the common seagrass specles In a muted seagrass bed on the Bollnao leef flat (Luzon The Ph~llpplnes) to assess the contribution of these s p e c ~e s to canopy maintenance meadow biornass and productlvlty We tested the hypothesis that seagrass growth rates correlated negatively with shoot size and a g e when compared across specles, and found that shoot recruitment leaf turnover and honzontal rhizome elongation and branchlng rates were lower for s p e c ~e s wlth older and larger shoots ~Vedian shoot ages for the short-llved species were generally less than a year, those for the longer-llved Enhalus acoroides ( L f ) Royle and Thalassla hempnchii (Ehrenb ) Aschers were sllghtly more than 1 5 yr The oldest E acoroldes had almost reached 10 yr Generally, shoot mortality and ~e c r u l t m e n t balanced each other falrly well The rhizomes of longer-lived E acoroldes and T hempnchli elongated at rates of 5 and 21 cm yr-l, respectively, and those of the short-llved Synngodi~lm isoetifobum (Aschers ) Dandy and Halophila ovalls (R Br ) Hook f at rates of 135 and 141 cm yr-' Vertical shoot elongat~on ranged from 2 to 13 cm shoot ' yr ' and was not correlated wlth size or a g e The meadow had a total bion~ass of 624 g dry wt (DW) m-' (roots excluded), to whlch the larger and longer-llved specles 7 hempnchil and E acoro~des contnbuted substantially (52 and 37%, respectively) Leaf product~on dominated total annual ploductlvity, constituting 91 % of 2143 g DW m ' yr ' (roots excluded) thls productlvlty was malnly due to T hempnchli (74 %), and not to the oldest and slowest-growing E acoroides ( 1 0 % ) KEY WORDS Troplcal seagrasses Shoot life spans Recruitment and mortal~ty P ~o n e e r vs cllmax specles Allon~etry 'E-mail address. ]ev