Turning riprap into reefs: Integrating oyster shells into shoreline armouring

Thea E. Bradford; Chi C. Lo; Juan Carlos Astudillo; Rainbow W.S. Leung; Charlene Lai; Jay J. Minuti; Carmen K.M. Wong; Stephen J. Hawkins; Rebecca L. Morris; Kenneth Mei Yee  Leung

doi:10.1016/j.marpolbul.2025.117933

Turning riprap into reefs: Integrating oyster shells into shoreline armouring

Thea E. Bradford (Co-first Author), Chi C. Lo (Co-first Author), Juan Carlos Astudillo^*, Rainbow W.S. Leung, Charlene Lai, Jay J. Minuti, Carmen K.M. Wong, Stephen J. Hawkins, Rebecca L. Morris, Kenneth Mei Yee Leung^*

^*Corresponding author for this work

Research output: Journal Publications and Reviews › RGC 21 - Publication in refereed journal › peer-review

2 Citations (Scopus)

Abstract

Boulder seawalls constructed with granite riprap for shoreline armouring lack habitat complexity, leading to lower marine biodiversity than natural rocky shores. Baskets of live oysters and cured oyster shells, and strings of cured shells laid on concrete blocks were installed on ripraps in Hong Kong, China with an aim to enhance biodiversity and ecosystem functioning towards that of a natural rocky shore. Inhabiting taxa were monitored for at least 18 months and biofiltration capacity of the emerging community was determined ex-situ. Despite high mortality of the live oysters, the baskets and shell reefs developed consistently greater biodiversity than control riprap, culminating in a mean 3.8 (±0.28, 95 % C.I.) times higher across sites. The baskets and shell reefs harboured suspension feeders, herbivores and carnivores generally absent from control riprap, demonstrating the potential for enhancing ecosystem functioning. Overall, baskets and shell reefs increased biodiversity through increased microhabitat availability for epibiota on ripraps. © 2025 Published by Elsevier Ltd.

Original language	English
Article number	117933
Journal	Marine Pollution Bulletin
Volume	216
Online published	13 Apr 2025
DOIs	https://doi.org/10.1016/j.marpolbul.2025.117933
Publication status	Published - Jul 2025

Funding

The authors thank the Development Bureau and the Civil Engineering and Development Department (CEDD) of the Hong Kong SAR Government for their ongoing support and expertise in these projects. The oyster basket experiment was supported by CEDD (project number PW 2/2017) while the oyster shell reef experiment was supported by the Development Bureau (project number PLB(Q)24/2019). The study was partially supported by the State Key Laboratory of Marine Pollution (SKLMP) at City University of Hong Kong which is supported by the provision of regular research funding from the Innovation and Technology Commission (ITC) of the Hong Kong SAR Government (project number PJ9448002). However, any opinions, findings, conclusions, or recommendations expressed in this publication do not reflect the views of the Hong Kong SAR Government.

Research Keywords

Living shorelines
Eco-engineering
Artificial seawalls
Land reclamation
Greening of grey infrastructure
Coastal blue/green infrastructure

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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title = "Turning riprap into reefs: Integrating oyster shells into shoreline armouring",

abstract = "Boulder seawalls constructed with granite riprap for shoreline armouring lack habitat complexity, leading to lower marine biodiversity than natural rocky shores. Baskets of live oysters and cured oyster shells, and strings of cured shells laid on concrete blocks were installed on ripraps in Hong Kong, China with an aim to enhance biodiversity and ecosystem functioning towards that of a natural rocky shore. Inhabiting taxa were monitored for at least 18 months and biofiltration capacity of the emerging community was determined ex-situ. Despite high mortality of the live oysters, the baskets and shell reefs developed consistently greater biodiversity than control riprap, culminating in a mean 3.8 (±0.28, 95 % C.I.) times higher across sites. The baskets and shell reefs harboured suspension feeders, herbivores and carnivores generally absent from control riprap, demonstrating the potential for enhancing ecosystem functioning. Overall, baskets and shell reefs increased biodiversity through increased microhabitat availability for epibiota on ripraps. {\textcopyright} 2025 Published by Elsevier Ltd.",

keywords = "Living shorelines, Eco-engineering, Artificial seawalls, Land reclamation, Greening of grey infrastructure, Coastal blue/green infrastructure",

author = "Bradford, {Thea E.} and Lo, {Chi C.} and Astudillo, {Juan Carlos} and Leung, {Rainbow W.S.} and Charlene Lai and Minuti, {Jay J.} and Wong, {Carmen K.M.} and Hawkins, {Stephen J.} and Morris, {Rebecca L.} and Leung, {Kenneth Mei Yee}",

year = "2025",

month = jul,

doi = "10.1016/j.marpolbul.2025.117933",

language = "English",

volume = "216",

journal = "Marine Pollution Bulletin",

issn = "0025-326X",

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TY - JOUR

T1 - Turning riprap into reefs

T2 - Integrating oyster shells into shoreline armouring

AU - Bradford, Thea E.

AU - Lo, Chi C.

AU - Astudillo, Juan Carlos

AU - Leung, Rainbow W.S.

AU - Lai, Charlene

AU - Minuti, Jay J.

AU - Wong, Carmen K.M.

AU - Hawkins, Stephen J.

AU - Morris, Rebecca L.

AU - Leung, Kenneth Mei Yee

PY - 2025/7

Y1 - 2025/7

N2 - Boulder seawalls constructed with granite riprap for shoreline armouring lack habitat complexity, leading to lower marine biodiversity than natural rocky shores. Baskets of live oysters and cured oyster shells, and strings of cured shells laid on concrete blocks were installed on ripraps in Hong Kong, China with an aim to enhance biodiversity and ecosystem functioning towards that of a natural rocky shore. Inhabiting taxa were monitored for at least 18 months and biofiltration capacity of the emerging community was determined ex-situ. Despite high mortality of the live oysters, the baskets and shell reefs developed consistently greater biodiversity than control riprap, culminating in a mean 3.8 (±0.28, 95 % C.I.) times higher across sites. The baskets and shell reefs harboured suspension feeders, herbivores and carnivores generally absent from control riprap, demonstrating the potential for enhancing ecosystem functioning. Overall, baskets and shell reefs increased biodiversity through increased microhabitat availability for epibiota on ripraps. © 2025 Published by Elsevier Ltd.

AB - Boulder seawalls constructed with granite riprap for shoreline armouring lack habitat complexity, leading to lower marine biodiversity than natural rocky shores. Baskets of live oysters and cured oyster shells, and strings of cured shells laid on concrete blocks were installed on ripraps in Hong Kong, China with an aim to enhance biodiversity and ecosystem functioning towards that of a natural rocky shore. Inhabiting taxa were monitored for at least 18 months and biofiltration capacity of the emerging community was determined ex-situ. Despite high mortality of the live oysters, the baskets and shell reefs developed consistently greater biodiversity than control riprap, culminating in a mean 3.8 (±0.28, 95 % C.I.) times higher across sites. The baskets and shell reefs harboured suspension feeders, herbivores and carnivores generally absent from control riprap, demonstrating the potential for enhancing ecosystem functioning. Overall, baskets and shell reefs increased biodiversity through increased microhabitat availability for epibiota on ripraps. © 2025 Published by Elsevier Ltd.

KW - Living shorelines

KW - Eco-engineering

KW - Artificial seawalls

KW - Land reclamation

KW - Greening of grey infrastructure

KW - Coastal blue/green infrastructure

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DO - 10.1016/j.marpolbul.2025.117933

M3 - RGC 21 - Publication in refereed journal

SN - 0025-326X

VL - 216

JO - Marine Pollution Bulletin

JF - Marine Pollution Bulletin

M1 - 117933

ER -

Turning riprap into reefs: Integrating oyster shells into shoreline armouring

Abstract

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