Community-Managed Coral Reef Restoration in Southern Kenya Initiates Reef Recovery Using Various Artificial Reef Designs
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Date
2023-04
Authors
Knoester, EG.
Rienstra, JJ.
Schürmann, QJF.
Wolma, AE.
Murk, AJ.
Osinga, R.
Journal Title
Journal ISSN
Volume Title
Publisher
Frontiers in Marine Science
Abstract
Monitoring of reef restoration efforts and artificial reefs (ARs) has typically been
limited to coral fragment survival, hampering evaluation of broader objectives
such as ecosystem recovery. This study aimed to determine to what extent AR
design influences the ecological recovery of restored reefs by monitoring
outplanted coral fragments, benthic cover, coral recruitment and fish and
invertebrate communities for two years. Four AR designs (16 m2
), unrestored
controls and natural reef patches as reference (n = 10) were established in
Mkwiro, Kenya. ARs consisted either of concrete disks with bottles, layered
concrete disks, metal cages or a combination thereof. A mixture of 18
branching coral species (mainly Acropora spp.) was outplanted on ARs at a
density of 7 corals m-2. After two years, 60% of all outplanted fragments had
survived, already resulting in coral cover on most ARs comparable (though
Acropora-dominated) to reference patches. Coral survival differed between
ARs, with highest survival on cages due to the absence of crown-of-thorns sea
star predation on this design. In total, 32 coral genera recruited on ARs and
recruit densities were highest on reference patches, moderate on concrete ARs
and low on cages. ARs and reference patches featured nearly twice the fish
species richness and around an order of magnitude higher fish abundance and
biomass compared to control patches. Fish abundance and biomass strongly
correlated with coral cover on ARs. AR, reference and control patches all had
distinct fish species compositions, but AR and reference patches were similar in
terms of trophic structure of their fish communities. Motile invertebrates
including gastropods, sea urchins, sea cucumbers and sea stars were present
at ARs, but generally more abundant and diverse at natural reference patches.
Taken together, all studied ecological parameters progressed towards reef
ecosystem recovery, with varying influences of AR design and material. We
recommend a combination of metal cages and layered concrete ARs to promote
high fragment survival as well as natural coral recruitment. Ultimately, a longer
period of monitoring is needed to fully determine the effectiveness reef
restoration as conservation tool to support coral reef ecosystem recovery
Description
Article
Keywords
Acropora, coral gardening, coral predation, coral recruitment, fish community, keystone invertebrates, long-term ecological monitoring, structural complexity
Citation
Knoester, E. G., Rienstra, J. J., Schürmann, Q. J. F., Wolma, A. E., Murk, A. J., & Osinga, R. (2023). Community-managed coral reef restoration in southern Kenya initiates reef recovery using various artificial reef designs. Frontiers in Marine Science, 10, 1152106.