Positive responses of a seagrass ecosystem to experimental nutrient enrichment

Brendan P. Kelaher, James Van Den Broek, Paul H. York, Melanie J. Bishop, David J. Booth

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Nutrient enrichment of coastal waters is widely recognized as a major driver of seagrass decline. Under conditions where seagrasses are nutrient-limited, however, moderately elevated nutrient loads can enhance seagrass biomass and increase above- and below-ground consumers that support higher order predators. To improve understanding of bottom-up processes in seagrass ecosystems, we conducted a manipulative field experiment to simultaneously evaluate the responses of primary producers (seagrass and epiphytes) and the epiphyte- and the sedimentbased components of seagrass food webs to moderate and high levels of waterborne nutrients. Fifteen 7 m 2 sites in Zostera muelleri meadows were assigned randomly to control, moderate or high nutrient treatments and were enriched with 0, 1800 g and 3600 g respectively of slow-release fertilizer in above-ground dispensers. The experiment ran for 9 mo (August 2006 to April 2007) and the fertilizer was replaced every 2 mo to ensure continuous enrichment. The biomass of primary producers (seagrasses Z. muelleri, Halophila ovalis and associated epiphytes) and the abundance of predators in the epiphyte- and the sediment-based components of the food web were greater in nutrient-enriched treatments than in controls. Epiphyte grazers, deposit feeders/detritivores, suspension feeders and benthic grazers did not respond significantly to the nutrient enrichment. In general, responses to nutrient enrichment were similar for medium and high nutrient treatments except that the biomass and surface area of seagrass was greater in high enrichment sites. These results demonstrate that Z. muelleri-dominated seagrass meadows in oligotrophic systems may be resilient to greater nutrient loads. Effective conservation strategies for Z. muelleri meadows should continue to consider interactions among nutrient enrichment and other key anthropogenic stressors, particularly non-nutrient pollutants in runoff and sewage discharge.

LanguageEnglish
Pages15-25
Number of pages11
JournalMarine Ecology Progress Series
Volume487
DOIs
Publication statusPublished - 30 Jul 2013

Fingerprint

nutrient enrichment
seagrass
ecosystems
nutrient
ecosystem
nutrients
meadows
epiphyte
epiphytes
pollution load
food webs
biomass
predators
meadow
Halophila
food web
dispensers
Zostera
slow-release fertilizers
detritivores

Cite this

Kelaher, Brendan P. ; Van Den Broek, James ; York, Paul H. ; Bishop, Melanie J. ; Booth, David J. / Positive responses of a seagrass ecosystem to experimental nutrient enrichment. In: Marine Ecology Progress Series. 2013 ; Vol. 487. pp. 15-25.
@article{1f09d93830a34a8f96e3a3b53b8fbbfc,
title = "Positive responses of a seagrass ecosystem to experimental nutrient enrichment",
abstract = "Nutrient enrichment of coastal waters is widely recognized as a major driver of seagrass decline. Under conditions where seagrasses are nutrient-limited, however, moderately elevated nutrient loads can enhance seagrass biomass and increase above- and below-ground consumers that support higher order predators. To improve understanding of bottom-up processes in seagrass ecosystems, we conducted a manipulative field experiment to simultaneously evaluate the responses of primary producers (seagrass and epiphytes) and the epiphyte- and the sedimentbased components of seagrass food webs to moderate and high levels of waterborne nutrients. Fifteen 7 m 2 sites in Zostera muelleri meadows were assigned randomly to control, moderate or high nutrient treatments and were enriched with 0, 1800 g and 3600 g respectively of slow-release fertilizer in above-ground dispensers. The experiment ran for 9 mo (August 2006 to April 2007) and the fertilizer was replaced every 2 mo to ensure continuous enrichment. The biomass of primary producers (seagrasses Z. muelleri, Halophila ovalis and associated epiphytes) and the abundance of predators in the epiphyte- and the sediment-based components of the food web were greater in nutrient-enriched treatments than in controls. Epiphyte grazers, deposit feeders/detritivores, suspension feeders and benthic grazers did not respond significantly to the nutrient enrichment. In general, responses to nutrient enrichment were similar for medium and high nutrient treatments except that the biomass and surface area of seagrass was greater in high enrichment sites. These results demonstrate that Z. muelleri-dominated seagrass meadows in oligotrophic systems may be resilient to greater nutrient loads. Effective conservation strategies for Z. muelleri meadows should continue to consider interactions among nutrient enrichment and other key anthropogenic stressors, particularly non-nutrient pollutants in runoff and sewage discharge.",
author = "Kelaher, {Brendan P.} and {Van Den Broek}, James and York, {Paul H.} and Bishop, {Melanie J.} and Booth, {David J.}",
year = "2013",
month = "7",
day = "30",
doi = "10.3354/meps10364",
language = "English",
volume = "487",
pages = "15--25",
journal = "Marine Ecology Progress Series",
issn = "0171-8630",
publisher = "Inter-Research",

}

Positive responses of a seagrass ecosystem to experimental nutrient enrichment. / Kelaher, Brendan P.; Van Den Broek, James; York, Paul H.; Bishop, Melanie J.; Booth, David J.

In: Marine Ecology Progress Series, Vol. 487, 30.07.2013, p. 15-25.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Positive responses of a seagrass ecosystem to experimental nutrient enrichment

AU - Kelaher, Brendan P.

AU - Van Den Broek, James

AU - York, Paul H.

AU - Bishop, Melanie J.

AU - Booth, David J.

PY - 2013/7/30

Y1 - 2013/7/30

N2 - Nutrient enrichment of coastal waters is widely recognized as a major driver of seagrass decline. Under conditions where seagrasses are nutrient-limited, however, moderately elevated nutrient loads can enhance seagrass biomass and increase above- and below-ground consumers that support higher order predators. To improve understanding of bottom-up processes in seagrass ecosystems, we conducted a manipulative field experiment to simultaneously evaluate the responses of primary producers (seagrass and epiphytes) and the epiphyte- and the sedimentbased components of seagrass food webs to moderate and high levels of waterborne nutrients. Fifteen 7 m 2 sites in Zostera muelleri meadows were assigned randomly to control, moderate or high nutrient treatments and were enriched with 0, 1800 g and 3600 g respectively of slow-release fertilizer in above-ground dispensers. The experiment ran for 9 mo (August 2006 to April 2007) and the fertilizer was replaced every 2 mo to ensure continuous enrichment. The biomass of primary producers (seagrasses Z. muelleri, Halophila ovalis and associated epiphytes) and the abundance of predators in the epiphyte- and the sediment-based components of the food web were greater in nutrient-enriched treatments than in controls. Epiphyte grazers, deposit feeders/detritivores, suspension feeders and benthic grazers did not respond significantly to the nutrient enrichment. In general, responses to nutrient enrichment were similar for medium and high nutrient treatments except that the biomass and surface area of seagrass was greater in high enrichment sites. These results demonstrate that Z. muelleri-dominated seagrass meadows in oligotrophic systems may be resilient to greater nutrient loads. Effective conservation strategies for Z. muelleri meadows should continue to consider interactions among nutrient enrichment and other key anthropogenic stressors, particularly non-nutrient pollutants in runoff and sewage discharge.

AB - Nutrient enrichment of coastal waters is widely recognized as a major driver of seagrass decline. Under conditions where seagrasses are nutrient-limited, however, moderately elevated nutrient loads can enhance seagrass biomass and increase above- and below-ground consumers that support higher order predators. To improve understanding of bottom-up processes in seagrass ecosystems, we conducted a manipulative field experiment to simultaneously evaluate the responses of primary producers (seagrass and epiphytes) and the epiphyte- and the sedimentbased components of seagrass food webs to moderate and high levels of waterborne nutrients. Fifteen 7 m 2 sites in Zostera muelleri meadows were assigned randomly to control, moderate or high nutrient treatments and were enriched with 0, 1800 g and 3600 g respectively of slow-release fertilizer in above-ground dispensers. The experiment ran for 9 mo (August 2006 to April 2007) and the fertilizer was replaced every 2 mo to ensure continuous enrichment. The biomass of primary producers (seagrasses Z. muelleri, Halophila ovalis and associated epiphytes) and the abundance of predators in the epiphyte- and the sediment-based components of the food web were greater in nutrient-enriched treatments than in controls. Epiphyte grazers, deposit feeders/detritivores, suspension feeders and benthic grazers did not respond significantly to the nutrient enrichment. In general, responses to nutrient enrichment were similar for medium and high nutrient treatments except that the biomass and surface area of seagrass was greater in high enrichment sites. These results demonstrate that Z. muelleri-dominated seagrass meadows in oligotrophic systems may be resilient to greater nutrient loads. Effective conservation strategies for Z. muelleri meadows should continue to consider interactions among nutrient enrichment and other key anthropogenic stressors, particularly non-nutrient pollutants in runoff and sewage discharge.

UR - http://www.scopus.com/inward/record.url?scp=84881075395&partnerID=8YFLogxK

U2 - 10.3354/meps10364

DO - 10.3354/meps10364

M3 - Article

VL - 487

SP - 15

EP - 25

JO - Marine Ecology Progress Series

T2 - Marine Ecology Progress Series

JF - Marine Ecology Progress Series

SN - 0171-8630

ER -