Overview

The study focuses on the placement of artificial tidal pools along the Lauwersmeerdijk in the Dutch Wadden Sea to enhance biodiversity and improve coastal ecosystems. It investigates how eco-engineering can transform hardened coastal infrastructure into more ecologically valuable habitats.

Background

Modern coastal defence structures — such as dikes, seawalls, and breakwaters — often replace natural habitats like salt marshes, tidal flats, and estuaries.

  • This process, known as shoreline hardening, leads to a loss of habitat diversity and a decline in marine biodiversity.
  • With sea level rise and climate change, there is an increasing need for artificial coastal protection, which could further intensify these problems.

Artificial tidal pools are introduced as a solution. These structures retain water during low tide, mimicking natural rock pools that provide shelter, moisture, and cooler conditions for marine organisms, thus supporting a diverse array of species.

The Lauwersmeerdijk Project

  • Location: Vierhuizergat, between Lauwersoog and Westpolder, Dutch Wadden Sea.
  • Timeline: Pools installed in November 2021.
  • Scale:
    • 26 tidal pools installed along 4.5 km of dike.
    • Divided into six clusters containing different pool designs.
  • Materials: Built using sustainable concrete and natural recycled materials like shell fragments.

Three Different Designs

The project tested three pool types with different depths and surface textures (see visual on page 3 of the document):

  1. Armor Blocks (AB):
    • Shallow pools
    • Complex ridge structure for microhabitats
  2. Tidal Pools (TP):
    • Deep pools with a smoother surface
    • Horizontal ridges on the exterior
  3. Reefpools (RP):
    • Deep rectangular pools
    • Rough, natural texture incorporating shell fragments

Study Objectives

The researchers aimed to determine:

  1. Whether the artificial tidal pools would attract different and more diverse communities compared to the existing dike rocks.
  2. Whether the different designs would foster unique habitats and species.

Key Findings (2022–2024)

  1. Increase in Biodiversity
  • After three years, the tidal pools supported 50% higher biodiversity compared to the regular rock base of the dike

  • Communities included common species like barnacles, mussels, oysters, and green algae, but also rare and unique species:
    • Sea anemones
    • Hydroids
    • Red algae
    • Colonial diatoms
  1. Diverse Ecological Functions
  • The pools fostered a greater variety of ecosystems, increasing both:
    • Alpha diversity (local diversity within each pool)
    • Beta diversity (variation between clusters)
  • Different designs supported different communities:
    • RP pools: Promoted blue mussels
    • TP pools: Encouraged bladderwrack and oysters
    • AB pools: Supported hydroids and algae
  1. Strengthening the Food Web
  • By adding canopy-forming algae and reef-building species like mussels and oysters, the pools created 3D habitat structures that support other organisms.
  • Increased growth of algae and diatoms provides food for grazers, strengthening the local food chain.

Conclusions

The research demonstrates that artificial tidal pools are a powerful eco-engineering tool to:

  • Significantly increase marine biodiversity along hardened coastlines.
  • Enhance habitat quality by introducing natural features like water retention and structural complexity.
  • Support climate-resilient and nature-inclusive coastal defences.

The study recommends installing clusters of mixed pool designs to create a mosaic of habitats, ensuring a wide variety of niches for different species

Implications

This project shows how coastal engineering can go beyond flood protection to actively restore ecological functions:

  • Healthier intertidal ecosystems
  • Improved resilience of coastal food webs
  • Potential for replication along other dikes and seawalls worldwide