dorsal/arxiv
View SchemaBenthic inputs as predictors of seagrass (Posidonia oceanica) fish farm-induced decline
| Authors | Elena Diaz-Almela, Nuria Marba, Elvira Alvarez, Rocio Santiago, Marianne Holmer, Antoni Grau, Roberto Danovaro, Marina Argyrou, Ioannis Karakasis, Carlos Manuel Duarte |
|---|---|
| Categories | |
| ArXiv ID | q-bio/0611006 |
| URL | https://arxiv.org/abs/q-bio/0611006 |
Abstract
Fish farms represent a growing source of disturbance to shallow benthic ecosystems like seagrass meadows. Despite some existing insights on the mechanisms underlying decline, efficient tools to quantitatively predict the response of benthic communities to fish farm effluents have not yet been developed. We explored relationships of fish farm organic and nutrient input rates to the sediments with population dynamics of the key seagrass species (Posidonia oceanica) in deep meadows growing around four Mediterranean Sea bream and Sea bass fish farms. We performed 2 annual shoot censuses on permanent plots at increasing distance from cages. Before each census we measured sedimentation rates adjacent to the plots using benthic sediment traps. High shoot mortality rates were recorded near the cages, up to 20 times greater than at control sites. Recruitment rates remained similar to undisturbed meadows and could not compensate mortality, leading to rapid seagrass decline within the first 100 meters from cages. Seagrass mortality increased with total (R2= 0.47, p< 0.0002), organic matter (R2= 0.36, p= 0.001), nitrogen (R2= 0.34, p= 0.002) and phosphorus (R2= 0.58, p< 3 x 10-5) sedimentation rates. P. oceanica decline accelerated above a phosphorus loading threshold of 50 mg m-2 day-1. Benthic sedimentation rates seem a powerful predictor of seagrass mortality from fish farming, integrating local hydrodynamics, waste effluents variability and several environmental mechanisms, fuelled by organic inputs and leading to seagrass loss. Coupling direct measurements of benthic sedimentation rates with dynamics of key species is proposed as an efficient way to predict and minimize fish farm impacts to benthic communities.
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"abstract": "Fish farms represent a growing source of disturbance to shallow benthic\necosystems like seagrass meadows. Despite some existing insights on the\nmechanisms underlying decline, efficient tools to quantitatively predict the\nresponse of benthic communities to fish farm effluents have not yet been\ndeveloped. We explored relationships of fish farm organic and nutrient input\nrates to the sediments with population dynamics of the key seagrass species\n(Posidonia oceanica) in deep meadows growing around four Mediterranean Sea\nbream and Sea bass fish farms. We performed 2 annual shoot censuses on\npermanent plots at increasing distance from cages. Before each census we\nmeasured sedimentation rates adjacent to the plots using benthic sediment\ntraps. High shoot mortality rates were recorded near the cages, up to 20 times\ngreater than at control sites. Recruitment rates remained similar to\nundisturbed meadows and could not compensate mortality, leading to rapid\nseagrass decline within the first 100 meters from cages. Seagrass mortality\nincreased with total (R2= 0.47, p\u003c 0.0002), organic matter (R2= 0.36, p=\n0.001), nitrogen (R2= 0.34, p= 0.002) and phosphorus (R2= 0.58, p\u003c 3 x 10-5)\nsedimentation rates. P. oceanica decline accelerated above a phosphorus loading\nthreshold of 50 mg m-2 day-1. Benthic sedimentation rates seem a powerful\npredictor of seagrass mortality from fish farming, integrating local\nhydrodynamics, waste effluents variability and several environmental\nmechanisms, fuelled by organic inputs and leading to seagrass loss. Coupling\ndirect measurements of benthic sedimentation rates with dynamics of key species\nis proposed as an efficient way to predict and minimize fish farm impacts to\nbenthic communities.",
"arxiv_id": "q-bio/0611006",
"authors": [
"Elena Diaz-Almela",
"Nuria Marba",
"Elvira Alvarez",
"Rocio Santiago",
"Marianne Holmer",
"Antoni Grau",
"Roberto Danovaro",
"Marina Argyrou",
"Ioannis Karakasis",
"Carlos Manuel Duarte"
],
"categories": [
"q-bio.QM",
"q-bio.PE"
],
"title": "Benthic inputs as predictors of seagrass (Posidonia oceanica) fish farm-induced decline",
"url": "https://arxiv.org/abs/q-bio/0611006"
},
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