A small-scale test of the species-energy hypothesis in a southern California estuary

Green, Lauri; Fong, Peggy

doi:10.1016/j.jembe.2014.12.012

Cited by 1 publication

(1 citation statement)

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“…This is similar to drift kelp that rafted onto seagrass beds and beaches thus enhancing nitrogen supplies (Hyndes et al ) and food availability (Spiller et al , Poore and Gallagher ) for aquatic and terrestrial communities. Further, Green and Fong () demonstrated that macroalgal mats of 0.5 and 1.5 cm supported greater densities of macrofauna than plastic macroalgal mimics, strongly suggesting that thin mats provide trophic support to benthic communities. Thus, we surmise that low to moderate subsidies of macroalgae promote estuarine ecosystem function through enhanced trophic support.…”

Section: Discussionmentioning

confidence: 99%

The good, the bad and the Ulva: the density dependent role of macroalgal subsidies in influencing diversity and trophic structure of an estuarine community

Green¹,

Fong²

2015

Oikos

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Worldwide, ecological subsidies enhance ecosystem productivity and therefore trophic support for greater biodiversity of taxa. While studies in terrestrial and aquatic ecosystems demonstrate that the magnitude of subsidies into ecosystems diff ers widely, the thresholds where subsidies may switch from exerting positive to negative eff ects are poorly understood. In estuaries, eutrophication promotes drift macroalgae that deposit on the benthos, cover intertidal fl ats for months and serve as pressed resource subsidies for benthic consumers. We hypothesized there would be a critical threshold of macroalgal biomass where ecosystem-level eff ects would turn from positive to negative. We used manipulative fi eld experiments varying macroalgal mat thickness (0.5, 1.5 and 4 cm) over eight weeks and quantifi ed eff ects on macrofauna on a lagoon mudfl at in California. We documented that plots with mat depths of 0.5 and 1.5 cm had higher diversity by supporting both surface feeding and burrowing detritivores. Non-metric multidimensional scaling showed that the benthic community diverged with mat depth over the course of the experiment. After eight weeks, surface deposit feeders were associated mainly with 0.5 cm macroalgal subsidies, whereas subsurface deposit feeding capitellids were closely linked with 4 cm mats. Depth profi les of pore water sulfi de concentration collected from 4 cm mats were 7622 Ϯ 5294 μ M, mean Ϯ SE, (mean of means across depth profi les), whereas 0.5 cm treatments resulted in sulfi de concentrations that were 0.25% of the 4 cm treatments. Th is suggests that the mechanism of negative eff ects for elevated macroalgal subsidies was development of anoxic conditions promoting sulfi de accumulation. Th us, our study was the fi rst to fi nd a critical threshold, or ecological tipping point, beyond which the eff ects of anthropogenically enhanced subsidies to estuarine mudfl at communities switched from positive to negative and to describe the mechanism by which elevated subsides altered the abiotic environment and likely reduced ecosystem functioning.

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Section: Discussionmentioning

confidence: 99%