Trophic Models of Seagrass Ecosystems in Maqueda Channel, Caramoan Peninsula, Philippines

Abstract

Steady-state trophic models were constructed using the Ecopath with Ecosim software to examine the general status, development trends, and functional integrity of three extensive seagrass meadows located in Maqueda Channel of Caramoan Peninsula, Southern Luzon Island, Philippines. The results show that the ecosystems are composed of 23-24 functional groups with effective trophic levels extending from 1.00 to 3.76. Mixed trophic impacts show that decrease in the biomass of grazers Tripneustes gratilla (collector urchin) had a positive impact on the biomass of seagrasses. On the other hand, a positive effect on the benthic groups is expected with an assumed decrease in the biomass of detritus and phytoplankton. Analysis of the flow network of organic matter and trophic efficiencies showed that flows were generally low for higher TLs but high for lower TLs (i.e., from TL 1 to IV. The ecosystems were found to be in mature and stable state based on the system statistics.

Food-Web Dynamics in Three Seagrass Systems in Caramoan Peninsula, Philippines

“…Thus, supply exceeds demand, that is, the excess seagrass production simply goes to detritus. These findings are congruent with the observations of Mengistou [41] and Clores and Cuesta [8], who documented that herbivore grazers leave significant excess during the consumption of their prey. Furthermore, this finding implies that the production of seagrass is high, but a large amount of this production becomes part of unconsumed detritus.…”

“…The results of MTI analysis were consistent with the observations of Clores and Cuesta [8], showing that phytoplankton and detritus have a positive impact on most other groups. Phytoplankton significantly positively impact zooplankton illustrating that the greatest impact was observed on direct predators.…”

“…It similarly affirms the observation that the ratio between total primary production and total system respiration suggests that all the seagrass systems are still immature. Clores and Cuesta [8] made the same conclusion about the other seagrass meadows in Caramoan Peninsula.…”

“…Caramoan Peninsula is one of the Philippines' under-researched areas. The pristine seagrass ecosystems in this part of the country are ideal sites for trophic analysis by characterizing the ecosystem components and links, especially between the primary producers and the consumers in seagrass systems [8].…”

“…This study builds on Lindeman's tropho-dynamics concept [8] by examining how energy flows from the seagrasses to their consumers. "Trophodynamics, by regulating the cycling of mass, energy, and nutrients, determines how marine ecosystems function and respond to both internal and external pressures, as food web pathways adapt to facilitate ecosystem resilience and persistence" [9].…”