Herbivory in multi-species, tropical seagrass beds

Abstract

Very little is known about the characteristics of herbivory and selection by various grazers in tropical, multi-species seagrass beds. We used an in situ shoot tethering method to quantify grazing on 3 dominant seagrass species (Thalassia hemprichii, Cymodocea rotundata, and C. serrulata) that co-inhabit extensive seagrass beds surrounding Dongsha Island in the South China Sea. We measured the amount of seagrass grazing as well as leaf production in different habitats and seasons. The dominant seagrass grazers in Dongsha Island were parrotfish, followed by meso-invertebrates, suggesting that herbivory by small invertebrates may also be critical in tropical seagrass ecosystems. Our results revealed significant spatial and seasonal differences in leaf biomass losses. The level of grazing was 3.6× higher in the subtidal than in the intertidal zones, and 2.6 × higher in the warm than in the cool season. Leaf biomass losses were positively associated with parrotfish density, water depth, leaf production, and starch content. However, the nitrogen and total sugar contents did not affect the preferences of the grazers. The 2 Cymodocea species were preferred by most grazers. Collectively, all grazers typically removed <10% of the leaf production in Dongsha Island, which indicates that most seagrass biomass was not directly used by herbivores and flows into detrital pathways.

Long Distance Dispersal Potential of Two Seagrasses Thalassia hemprichii and Halophila ovalis

“…They are highly mobile and are presumably good vectors between habitats on different islands. Most fishes around seagrass beds, on the other hand, are small, benthic fishes [ 32 ].…”

Paleophysiology: From Fossils to the Future

“…In attached seaweeds, rapid nutrient uptake and transport is indicated by a highly branched morphology and, in species with large blades, a complex 3D surface [80,81]. Mapping of these potential proxies for performance on algal phylogenies can indicate how performance has evolved over time and the extent to which performance is related to CO 2 levels and to escalating herbivory in the sea [82][83][84].…”

Spatial and Temporal Patterns in Macroherbivore Grazing in a Multi-Species Tropical Seagrass Meadow of the Great Barrier Reef

“…In temperate and subtropical meadows, herbivorous fish can consume all of the daily seagrass productivity, and in peak grazing events, they can consume over 10 times the daily productivity [8][9][10]. In tropical seagrass meadows, estimates of macroherbivore seagrass consumption range from as little as 3-26% of daily seagrass productivity [11][12][13][14], up to 10 times daily productivity at times [15], with grazing dominated by herbivorous fish [11,12]. Urchin herbivory can be high in temperate environments, where urchins can consume over 80% of aboveground seagrass biomass [16,17].…”