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Spatial structure and temporal dynamics of an intertidal population of the marine ecosystem engineering worm Lanice conchilega (Pallas, 1766)

(2017)
Author
Promoter
(UGent) , Jean-Marc Guarini, (UGent) , Tjeerd Bourma, (UGent) and Marijn Rabaut
Organization
Abstract
*Lanice conchilega* is an ecosystem engineering polychaete worm. It forms tube aggregations in temperate coastal zones, being particularly abundant in Europe. Tube aggregations engineer sandy-muddy marine sediments by posing as physical barriers which modulate water flow on the sediment surface, increasing local sedimentation and creating distinct micro-habitats within tube arrays for other organisms. Although previous research has greatly contributed to our understanding of how this organism engineers marine sediments, processes pertaining to formation and decay of its aggregations remained unclear. The main objective of this thesis was to elucidate these processes, in particular, to determine the role of population dynamics on engineering effects and the formation and decay of intertidal *L. conchilega* aggregations. Experiments were executed exploring the relationships between population dynamics, sedimentation, and mortality (chapter 2). Findings revealed that dense aggregations induce locally higher sedimentation and more stable sediments in comparison to bare surfaces. Abrupt sedimentation triggered tube-accretion and may form a positive feedback wherein growing tubes cause further sedimentation, hence contributing to aggregation maintenance. However, abrupt sedimentation of 5-12cm in height may hinder maintenance by increasing population mortality through smothering, which diminishes tube density and undermines further flow modulation. We also assessed temporal patterns in population structure, and investigated how these relate to ecosystem engineering by *L. conchilega* on marine sediments through monthly in-situ monitoring of intertidal aggregations (chapter 3). This revealed that seasonal population dynamics and demographic composition influence the temporal evolution of *L. conchilega* engineering effects, intensifying in periods of high density (i.e. recruitment), and decaying during periods of harsh conditions (i.e. winter). We also assessed the temporal evolution, persistence, and longevity of small-scale distribution patterns for intertidal *L. conchilega* aggregations (chapter 4). It was found that the formation of small-scale spatial patterns was associated to the aforementioned recruitment periods, prompting the formulation of a hypothetical conceptual model for aggregation formation and decay. We postulate that yearly recruitment in spring and autumn result in population replenishment and the formation of early small-scale spatial patterns. The latter are likely modified by continuing settlement and post-settlement survival giving rise to different small-scale distribution patterns, while aggregation decay was shown to occur apart from recruitment and likely due to population mortality. Lastly, we explored an alternative conceptual model for spatial-pattern formation in L. conchilega aggregations by performing a modelling exercise assessing the role of food availability and assimilation on population dynamics (chapter 5). Findings from the exercise suggest that food availability and assimilation are likely to only marginally influence population density dynamics, which seems to be determined largely by the recruitment intensity. This thesis has lead us to conclude that spatial-pattern formation in *L. conchilega* aggregations is likely delineated by conditions during settlement and factors influencing post-settlement survival. Since hydrodynamic conditions often influence settlement and recruitment, we suggest that future research focus on the effects of hydrodynamic stress in *L. conchilega* larval settlement and survival at very small spatial scales.
Keywords
ecosystem engineering, Lanice conchilega, polychaete aggregations, autogenic engineering, spatial pattern formation, population dynamics

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Citation

Please use this url to cite or link to this publication:

Chicago
Mamede da Silva Alves, Renata. 2017. “Spatial Structure and Temporal Dynamics of an Intertidal Population of the Marine Ecosystem Engineering Worm Lanice Conchilega (Pallas, 1766)”. Ghent, Belgium: Ghent University. Faculty of Sciences.
APA
Mamede da Silva Alves, R. (2017). Spatial structure and temporal dynamics of an intertidal population of the marine ecosystem engineering worm Lanice conchilega (Pallas, 1766). Ghent University. Faculty of Sciences, Ghent, Belgium.
Vancouver
1.
Mamede da Silva Alves R. Spatial structure and temporal dynamics of an intertidal population of the marine ecosystem engineering worm Lanice conchilega (Pallas, 1766). [Ghent, Belgium]: Ghent University. Faculty of Sciences; 2017.
MLA
Mamede da Silva Alves, Renata. “Spatial Structure and Temporal Dynamics of an Intertidal Population of the Marine Ecosystem Engineering Worm Lanice Conchilega (Pallas, 1766).” 2017 : n. pag. Print.
@phdthesis{8544280,
  abstract     = {*Lanice conchilega* is an ecosystem engineering polychaete worm. It forms tube aggregations in temperate coastal zones, being particularly abundant in Europe. Tube aggregations engineer sandy-muddy marine sediments by posing as physical barriers which modulate water flow on the sediment surface, increasing local sedimentation and creating distinct micro-habitats within tube arrays for other organisms. Although previous research has greatly contributed to our understanding of how this organism engineers marine sediments, processes pertaining to formation and decay of its aggregations remained unclear. The main objective of this thesis was to elucidate these processes, in particular, to determine the role of population dynamics on engineering effects and the formation and decay of intertidal *L. conchilega* aggregations. Experiments were executed exploring the relationships between population dynamics, sedimentation, and mortality (chapter 2). Findings revealed that dense aggregations induce locally higher sedimentation and more stable sediments in comparison to bare surfaces. Abrupt sedimentation triggered tube-accretion and may form a positive feedback wherein growing tubes cause further sedimentation, hence contributing to aggregation maintenance. However, abrupt sedimentation of 5-12cm in height may hinder maintenance by increasing population mortality through smothering, which diminishes tube density and undermines further flow modulation. We also assessed temporal patterns in population structure, and investigated how these relate to ecosystem engineering by *L. conchilega* on marine sediments through monthly in-situ monitoring of intertidal aggregations (chapter 3). This revealed that seasonal population dynamics and demographic composition influence the temporal evolution of *L. conchilega* engineering effects, intensifying in periods of high density (i.e. recruitment), and decaying during periods of harsh conditions (i.e. winter). We also assessed the temporal evolution, persistence, and longevity of small-scale distribution patterns for intertidal *L. conchilega* aggregations (chapter 4). It was found that the formation of small-scale spatial patterns was associated to the aforementioned recruitment periods, prompting the formulation of a hypothetical conceptual model for aggregation formation and decay. We postulate that yearly recruitment in spring and autumn result in population replenishment and the formation of early small-scale spatial patterns. The latter are likely modified by continuing settlement and post-settlement survival giving rise to different small-scale distribution patterns, while aggregation decay was shown to occur apart from recruitment and likely due to population mortality. Lastly, we explored an alternative conceptual model for spatial-pattern formation in L. conchilega aggregations by performing a modelling exercise assessing the role of food availability and assimilation on population dynamics (chapter 5). Findings from the exercise suggest that food availability and assimilation are likely to only marginally influence population density dynamics, which seems to be determined largely by the recruitment intensity. This thesis has lead us to conclude that spatial-pattern formation in *L. conchilega* aggregations is likely delineated by conditions during settlement and factors influencing post-settlement survival. Since hydrodynamic conditions often influence settlement and recruitment, we suggest that future research focus on the effects of hydrodynamic stress in *L. conchilega* larval settlement and survival at very small spatial scales.},
  author       = {Mamede da Silva Alves, Renata},
  isbn         = {9789082561111},
  keyword      = {ecosystem engineering,Lanice conchilega,polychaete aggregations,autogenic engineering,spatial pattern formation,population dynamics},
  language     = {eng},
  pages        = {XXII, 238},
  publisher    = {Ghent University. Faculty of Sciences},
  school       = {Ghent University},
  title        = {Spatial structure and temporal dynamics of an intertidal population of the marine ecosystem engineering worm Lanice conchilega (Pallas, 1766)},
  year         = {2017},
}