State of Thalassia testudinum Banks ex König meadows in the Veracruz Reef System, Veracruz, México

Abstract

The vegetative development of the seagrass Thalassia testudinum was assessed in three reefs (Hornos, isla Sacrificios, isla de Enmedio) of the Veracruz Reef System (Veracruz, México) which are located at increasing distances from the mainland coast. Leaf nutrient content of T. testudinum suggests that the availability of nitrogen and phosphorus increases from Hornos reef to isla Sacrificios and isla de Enmedio, that is, as the distance to the coast increases. The total biomass of this species tended to increase similarly as a result of the large increase of the biomass of rhizomes and roots but not of leaves. In contrast to previous knowledge of the response of seagrasses along gradients of nutrient availability, the rhizome and roots to shoot biomass ratio increased by a factor of two as nutrient availability increased. The density of T. testudinum shoots and their mass, the LAI and leaf productivity, and the average number of leaves produced by a T. testudinum shoot in 1 year were lowest in the reef closest to shore (Hornos). Our results show that the vegetative development of T. testudinum in Hornos reef is restrained when compared with that in isla Sacrificios and isla de Enmedio and suggest that the differences of vegetative development of this species in the Veracruz Reef System might be driven by factors other than nutrient availability.