Highly Productive Tropical Seagrass Beds Support Diverse Consumers and a Large Organic Carbon Pool in the Sediments

Abstract

Tropical seagrass beds are productive coastal ecosystems that are important blue carbon sinks and crucial habitats and feeding grounds for consumers at high trophic levels. To understand how energy sustains the ecosystem from seagrass production, we constructed an Ecopath trophic model to reveal the possible pathways of energy flow in the tropical seagrass beds around Dongsha Island, South China Sea. The model indicates that Dongsha seagrass beds were developing but well-structured ecosystems. The productive seagrasses were rarely directly consumed by herbivores and, ultimately, flowed into detrital pools. Detritus was the main food source used to support diverse consumers in the food web. Nevertheless, the low cycling rate (2.74%) suggests that most detritus was not reused or exported and was stored as a large organic carbon pool in the sediments. The detritus-feeding invertebrates are keystone groups in the Dongsha seagrass beds, as they recycle energy from detritus and transfer to top predators such as sharks. The predation of top predators affected the biomasses of other compartments, leading to strong top-down control via a trophic cascade effect.

Improving stable isotope assessments of inter‐ and intra‐species variation in coral reef fish trophic strategies

“…Algal and detrital resources are readily replenished on coral reefs but vary in their accessibility (Bonaldo & Bellwood, 2011 ; Brandl et al, 2015 ), but in the Dongsha lagoon, the range of resources available to herbivores is exceptionally diverse due to extensive seagrass beds and associated seagrass‐derived detritus. Furthermore, deeper water during flood tides provides more space for herbivores to forage, potentially expanding available resources (Lee et al, 2014 ; Lee, 2021 ). Wide ranges in aquatic plant matter isotope values are also not uncommon, driven by both differential forms of photosynthesis ( δ 13 C) and sulfate assimilation ( δ 34 S; Peterson et al, 1986 ; Peterson & Fry, 1987 ).…”

A Systematic Review and Global Trends on Blue Carbon and Sustainable Development: A Bibliometric Study from 2012 to 2023

“…Topic II: Blue carbon ecosystem assessment and sustainable management Seagrasses (dead seagrass, seagrass beds, seagrass meadows), mangroves, coral reefs, kelps, saltmarshes, macroalgae (or seaweeds), benthic microalgae, etc., constitute the blue carbon ecosystem, whose comprehensive benefit is also determined by the size, quality, and extent of the ecosystem [69,71,76,104,110,124,135,136,161,164,165,168,[170][171][172][173][174][175][176][177][178][179][180][181][182][183][184]. Due to the structural complexity of coastal vegetation ecosystems (root systems, dense vegetation, and leafy canopy in seagrass systems), salt marshes, mangroves, and seagrass beds are capable of efficiently capturing sediment and associated organic carbon from both riverine and oceanic sources [164].…”

Dynamics of O2 and pCO2 in a Southeast Asia seagrass meadow: Metabolic rates and carbon sink capacity

“…Despite the small area of Dongsha Island, massive seagrass meadows extend from the intertidal to the subtidal zones with a total coverage area of 11.85 km 2 around the entire island (Huang et al, 2015). A total of seven seagrass species from six genera and two families have been identified at Dongsha Island, including Thalassia hemprichii, Halophila ovalis, Cymodocea rotundata, C. serrulata, Halodule uninervis, Syringodium isoetifolium, and Thalassodentron ciliatum (Lin et al, 2005), and the coverage of seagrass meadows was generally >75% around the island (Lee et al, 2021). Among them, the most abundant species around Dongsha Island are T. hemprichii, H. uninervis, C. rotundata, and C. serrulata (Huang et al, 2015), and which are also popular species in Indo-Pacific (Short et al, 2007).…”