Exploring the occurrence of and explanations for nighttime spikes in dissolved oxygen across coral reef environments

Calhoun, Sandi; Haas, Andreas F.; Takeshita, Yuichiro; Johnson, Maggie D.; Fox, Michael D.; Kelly, Emily L. A.; Mueller, Benjamin; Vermeij, Mark J. A.; Kelly, Linda Wegley; Nelson, Craig E.; Price, Nichole N.; Roach, Ty N. F.; Rohwer, Forest; Smith, Jennifer E.

doi:10.7287/peerj.preprints.2935v1

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“…In general, estimates of net ecosystem production (NEP) on the benthos can be made by measuring changes in dissolved oxygen within chambers that are placed in situ over macroalgae and invertebrate communities. In this study, we deployed collapsible benthic isolation tents (cBITs) modelled after those described by Haas et al [58] and Calhoun et al [59] that directly measured in situ benthic oxygen production and allowed us to estimate gross primary production (GPP), ecosystem respiration (Re) and net ecosystem production NEP by the benthic communities [28, 29,55]. These cBITs were the same ones used by Sullaway and Edwards [60] to measure loss of primary productivity following the…”

Section: Methodsmentioning

confidence: 99%

Marine deforestation leads to widespread loss of ecosystem function

et al. 2020

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Trophic interactions can result in changes to the abundance and distribution of habitat-forming species that dramatically reduce ecosystem functioning. In the coastal zone of the Aleutian Archipelago, overgrazing by herbivorous sea urchins that began in the 1990s resulted in widespread deforestation of the region's kelp forests, which led to lower macroalgal abundances and higher benthic irradiances. We examined how this deforestation impacted ecosystem function by comparing patterns of net ecosystem production (NEP), gross primary production (GPP), ecosystem respiration (Re), and the range between GPP and Re in remnant kelp forests, urchin barrens, and habitats that were in transition between the two habitat types at nine islands that spanned more than 1000 kilometers of the archipelago. Our results show that deforestation, on average, resulted in a 24% reduction in GPP, a 26% reduction in Re, and a 24% reduction in the range between GPP and Re. Further, the transition habitats were intermediate to the kelp forests and urchin barrens for these metrics. These opposing metabolic processes remained in balance; however, which resulted in little-to-no changes to NEP. These effects of deforestation on ecosystem productivity, however, were highly variable between years and among the study islands. In light of the worldwide declines in kelp forests observed in recent decades, our findings suggest that marine deforestation profoundly affects how coastal ecosystems function.of the region's river systems and its riparian plant communities [4,5]. Similarly, large marine algae, such as kelps, can form subtidal forests whose biogenic structures alter hydrodynamic, nutrient and light conditions, modify patterns of biodiversity, enhance primary production and carbon sequestration, and provide food and habitat for numerous other species [6][7][8][9]. Consequently, the loss of these forest-forming kelps and the benthic communities they support can have dramatic impacts to how nearshore ecosystems function, especially if they occur over large geographic areas. Indeed, kelp deforestation has occurred in numerous areas worldwide in recent decades due to a variety of forcing factors [10,11], and the subtidal rocky reefs of the Aleutian Archipelago serve as a model system to investigate the broader impacts of such deforestation. These forests have historically been dominated by dense populations of the surface canopy-forming kelp Eualaria fistulosa, several species of understory kelps such as Laminaria spp. and Agarum spp., the brown alga Desmarestia spp., and numerous species of fleshy read algae. However, the collapse of sea otter (Enhydra lutris) populations led to large increases in their primary prey, herbivorous sea urchins (Strongylocentrotus polyacanthus), which subsequently resulted in overgrazing and widespread losses of the region's kelp forests [12]. This collapse began in the late 1990s, likely in response to a dietary shift by killer whales toward sea otters, and by 2000 sea otter densities had declined throughout the ar...

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Section: Methodsmentioning

confidence: 99%

Marine deforestation leads to widespread loss of ecosystem function

et al. 2020

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“…In general, estimates of net ecosystem production ( NEP ) on the benthos can be made by measuring changes in dissolved oxygen within benthic chambers that are placed in situ over of macroalgae and invertebrate communities. In this study, we deployed collapsible benthic isolation tents (cBITs) modelled after those described by Haas et al ( 47 ) and Calhoun et al ( 48 ) that directly measured in situ benthic oxygen production and allowed us to estimate gross primary production ( GPP ), ecosystem respiration ( Re ) and net ecosystem production NEP by the benthic communities ( 27, 28, 45 ). By linking temporal changes in oxygen concentrations within the cBITs to incident irradiance conditions and organism abundances, we can relate variation in GPP , Re, and NEP to primary producer and invertebrate biomass ( 27, 49 ).…”

Section: Methodsmentioning

confidence: 99%

Marine deforestation leads to widespread loss of ecosystem function

Edwards

Konar

Kim

et al. 2019

Preprint

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Trophic interactions can result in changes to the abundance and distribution of habitat-forming species that dramatically reduce ecosystem health and functioning. Nowhere may this be as dramatic as in the coastal zone of the Aleutian Archipelago, where overgrazing by herbivorous sea urchins that began in the 1980s resulted in widespread deforestation of the region’s kelp forests. Here we show that this deforestation resulted in decreased macroalgal and invertebrate abundance and diversity, increased benthic irradiances, and reduced rates of gross primary production and respiration by the ecosystem. These opposing metabolic processes remain in balance, however, which resulted in little-to-no changes to net ecosystem production. These patterns were consistent across nine islands spanning more than 1000 kilometers of the archipelago. In light of the worldwide declines in kelp forests observed in recent decades, our findings suggest that marine deforestation profoundly affects the health of coastal ecosystems and how they function.Significance statementWidespread marine deforestation results in reduced biodiversity and primary productivity throughout more than 1000 km of the Aleutian Archipelago.

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Exploring the occurrence of and explanations for nighttime spikes in dissolved oxygen across coral reef environments

Cited by 2 publications

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Marine deforestation leads to widespread loss of ecosystem function

Marine deforestation leads to widespread loss of ecosystem function

Marine deforestation leads to widespread loss of ecosystem function

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