Bottom-up and top-down forces in a tropical intertidal ecosystem: The interplay between seagrasses, bivalves and birds

Jimmy de Fouw

Bottom-up and top-down forces in a tropical intertidal ecosystem: The interplay between seagrasses, bivalves and birds

Jimmy de Fouw

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Zeegrassen zijn zogenaamde ‘biobouwers’ en zijn de basis voor veel kustecosystemen. Het Waddengebied Banc d’Arguin is zo’n kustgebied. Het zeegras Zostera noltii hier barst van het leven waar o.a. de kanoet (Calidris canutus canutus) van leeft.
Zeegrassen hebben een belangrijke sturende rol als fundering van onderuit het ecosysteem (bottom-up). Ze creëren geschikte leefomstandigheden voor zichzelf én voor veel andere soorten. Zeegrasvelden die cruciaal zijn voor de biodiversiteit en kustbescherming worden echter op een onverwachte manier bedreigd door klimaatverandering. Door droogte en hittegolven stopt zeegras met het leveren van zuurstof aan schelpdieren (Loripes lucinalis) die samenleven met sulfide-etende bacteriën. Hierdoor sterven de schelpdieren en hun bacteriën, waarna ophopend sulfide in de zeebodem het zeegras vergiftigt.
Kanoeten beschikken over een uniek zintuig in het puntje van hun snavel waarmee ze efficiënt prooien kunnen detecteren zonder direct contact. Men zou verwachten dat kanoeten in staat zouden moeten zijn om Loripes weg te eten. Maar wat blijkt in hoge zeegras dichtheden verbergt zeegras indirect zijn detoxificerende schelp. In combinatie met de toxiciteit van de schelpen voorkomt dit een sterke doorwerking op het systeem van bovenaf (top-down).
Een computer model liet zien dat de stabiliseerde werking van het mutualisme weldegelijk kon worden verstoord door kanoeten. Het model liet zien dat in afstervend zeegras kanoeten mogelijk in staat waren om het afsterf proces te versnellen. Door hier de resterende Loripes weg te eten nam het giftige sulfide toe. Daarom kunnen we concluderen dat het top-down effect van kanoeten waarschijnlijk een cumulatief effect is wat het afsterven van het zeegras doet versnellen.

Originele taal-2	English
Kwalificatie	Doctor of Philosophy
Toekennende instantie	Rijksuniversiteit Groningen
Begeleider(s)/adviseur	Piersma, Theunis, Supervisor Olff, Han, Supervisor van Gils, J.A., Co-supervisor, Externe Persoon van der Heide, T., Co-supervisor, Externe Persoon
Datum van toekenning	29-apr.-2016
Plaats van publicatie	[Groningen]
Uitgever	Rijksuniversiteit Groningen
Gedrukte ISBN's	978-90-367-8769-7
Elektronische ISBN's	978-90-367-8768-0
Status	Published - 2016

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Title and contens Final publisher's version, 263 KB
Chapter 1 Final publisher's version, 4,51 MB
Chapter 2 Final publisher's version, 2,01 MB
Chapter 3 Final publisher's version, 5,87 MB
Chapter 4 Final publisher's version, 2,41 MB
Chapter 5 Final publisher's version, 1,16 MB
Chapter 6 Final publisher's version, 1,89 MB
Box 6.1 Final publisher's version, 1,18 MB
Chapter 7 Final publisher's version, 969 KB
Chapter 8 Final publisher's version, 4,76 MB
References Final publisher's version, 1,33 MB
Summary Final publisher's version, 1,06 MB
Acknowledgements Final publisher's version, 1,33 MB
Author affiliations and addresses Final publisher's version, 1,06 MB
List of PublicationsFinal publisher's version, 237 KB
Complete thesisFinal publisher's version, 36,5 MB
PropositionsFinal publisher's version, 32,5 KB

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@phdthesis{788ff8cd4cde457fa6b955850f1e4c44,

title = "Bottom-up and top-down forces in a tropical intertidal ecosystem: The interplay between seagrasses, bivalves and birds",

abstract = "Seagrasses are called 'ecosystem engineers' and are essential for many coastal ecosystems. The intertidal area Banc d'Arguin is such coastal area. The seagrass Zostera noltii here bursting with life, where the red knot (Calidris canutus canutus) lives and feeds from the benthic life.Seagrasses have an important bottom-up role as the foundation of the ecosystem. They create suitable living conditions for themselves and for many other species. Although seagrasses are crucial for biodiversity and coastal protection they are threatened by climate change in an unexpected way. Due to drought and heat waves seagrass suffers from desiccation stress and this alters the delivery of oxygen to their bivalve mutualistic partner (Loripes lucinalis) and their sulphide-oxidizing, gill-inhabiting bacteria ({\textquoteleft}endosymbionts{\textquoteright}). The breakdown of the mutualsim increases sulfide toxicity and speeds up the die-off of seagrasses.Red knots have a unique remote sense in the tip of their bill which allows them to detect buried prey efficiently without direct contact. One would expect that knots would be able to deplete Loripes and break the mutualistic partnership. But in high seagrass densities the seagrass conceals their detoxifying shell. In combination with the toxicity of the shells this prevents a strong top-down impact on the system.However, a computer model showed that the stabilized effect of the mutualism could be disturbed by knots. The model showed that in degrading seagrass knots may have been able to speed up the gradually degrading process. Here they may be able to eat the remaining Loripes which increases the toxic sulfide. Therefore, we can conclude that the top-down effect of knots is probably a cumulative effect that accelerates the disappearance of the seagrass in our study system.",

author = "{de Fouw}, Jimmy",

year = "2016",

language = "English",

isbn = "978-90-367-8769-7",

publisher = "Rijksuniversiteit Groningen",

school = "University of Groningen",

}

TY - BOOK

T1 - Bottom-up and top-down forces in a tropical intertidal ecosystem

T2 - The interplay between seagrasses, bivalves and birds

AU - de Fouw, Jimmy

PY - 2016

Y1 - 2016

N2 - Seagrasses are called 'ecosystem engineers' and are essential for many coastal ecosystems. The intertidal area Banc d'Arguin is such coastal area. The seagrass Zostera noltii here bursting with life, where the red knot (Calidris canutus canutus) lives and feeds from the benthic life.Seagrasses have an important bottom-up role as the foundation of the ecosystem. They create suitable living conditions for themselves and for many other species. Although seagrasses are crucial for biodiversity and coastal protection they are threatened by climate change in an unexpected way. Due to drought and heat waves seagrass suffers from desiccation stress and this alters the delivery of oxygen to their bivalve mutualistic partner (Loripes lucinalis) and their sulphide-oxidizing, gill-inhabiting bacteria (‘endosymbionts’). The breakdown of the mutualsim increases sulfide toxicity and speeds up the die-off of seagrasses.Red knots have a unique remote sense in the tip of their bill which allows them to detect buried prey efficiently without direct contact. One would expect that knots would be able to deplete Loripes and break the mutualistic partnership. But in high seagrass densities the seagrass conceals their detoxifying shell. In combination with the toxicity of the shells this prevents a strong top-down impact on the system.However, a computer model showed that the stabilized effect of the mutualism could be disturbed by knots. The model showed that in degrading seagrass knots may have been able to speed up the gradually degrading process. Here they may be able to eat the remaining Loripes which increases the toxic sulfide. Therefore, we can conclude that the top-down effect of knots is probably a cumulative effect that accelerates the disappearance of the seagrass in our study system.

AB - Seagrasses are called 'ecosystem engineers' and are essential for many coastal ecosystems. The intertidal area Banc d'Arguin is such coastal area. The seagrass Zostera noltii here bursting with life, where the red knot (Calidris canutus canutus) lives and feeds from the benthic life.Seagrasses have an important bottom-up role as the foundation of the ecosystem. They create suitable living conditions for themselves and for many other species. Although seagrasses are crucial for biodiversity and coastal protection they are threatened by climate change in an unexpected way. Due to drought and heat waves seagrass suffers from desiccation stress and this alters the delivery of oxygen to their bivalve mutualistic partner (Loripes lucinalis) and their sulphide-oxidizing, gill-inhabiting bacteria (‘endosymbionts’). The breakdown of the mutualsim increases sulfide toxicity and speeds up the die-off of seagrasses.Red knots have a unique remote sense in the tip of their bill which allows them to detect buried prey efficiently without direct contact. One would expect that knots would be able to deplete Loripes and break the mutualistic partnership. But in high seagrass densities the seagrass conceals their detoxifying shell. In combination with the toxicity of the shells this prevents a strong top-down impact on the system.However, a computer model showed that the stabilized effect of the mutualism could be disturbed by knots. The model showed that in degrading seagrass knots may have been able to speed up the gradually degrading process. Here they may be able to eat the remaining Loripes which increases the toxic sulfide. Therefore, we can conclude that the top-down effect of knots is probably a cumulative effect that accelerates the disappearance of the seagrass in our study system.

M3 - Thesis fully internal (DIV)

SN - 978-90-367-8769-7

PB - Rijksuniversiteit Groningen

CY - [Groningen]

ER -

Bottom-up and top-down forces in a tropical intertidal ecosystem: The interplay between seagrasses, bivalves and birds

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