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EU Funded projects
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SMARTPOL
Autonomous network system with specialized and integrated multi-sensor technology for dynamic monitoring of marine pollution
Ph.D.
Ph.D.
My PhD focused on habitat cascades, a unidirectional sequence of positive interactions in which one species provides habitat for another, which in turn facilitates additional species, and so on. Alongside direct interactions (e.g., species A → B and B → C), habitat cascades also generate indirect interactions (e.g., A → C).
HABITAT CASCADE SYSTEMS
Habitat cascades are a specific form of facilitation, where the primary benefit is habitat formation, modification, or amelioration. A typical example from my research involves rocky shore canopy-forming seaweeds: these algae naturally support diverse invertebrate communities by providing shelter, refuge from predation, stress buffering, and resources. When epiphytes colonise these seaweeds, they add additional structural complexity and settlement space, effectively extending the cascade. As a result, invertebrate abundance and taxonomic richness are expected to exceed the sum of what each habitat former would support independently.
My PhD tested the core hypothesis that habitat cascades are key drivers of biodiversity maintenance in marine benthic ecosystems, particularly in systems where epibiosis is widespread. I investigated their effects across multiple habitats, including rocky shores dominated by canopy-forming seaweeds, soft-bottom estuaries, and seagrass beds. The overarching aim was to develop conceptual, descriptive, and predictive ecological models applicable across habitats and biogeographical regions.
My PhD comprised 6 projects examining habitat cascades along a gradient of increasing ecological complexity, from low-diversity soft-bottom estuaries (Projects 1-2), to seagrass systems (Projects 3-4), and high-diversity rocky shores (Projects 5-6).
Approaches combined field and laboratory experiments, ecological surveys, drone-based observations, and 3D modelling. Analyses relied primarily on factorial experimental designs and permutational multivariate analysis of variance (PERMANOVA).
Descriptive surveys
to assess how habitat cascades vary across space and time, such as latitudinal and seasonal patterns
Manipulative experiments
to test causal mechanisms using multi-factorial designs such as biomass, species identity, morphology
Mechanistic experiments
to identify the processes underlying habitat cascade effects
Morphological analyses
linking habitat former structural complexity to ecological outcomes
PNZ1.jpgProject 1 — Estuarine soft-bottom systems: basic cascade structure
This project described one of the simplest habitat cascade systems observed during my PhD, in soft-bottom estuaries dominated by shell beds. I tested whether habitat cascade strength depends on the biomass of secondary habitat formers and whether ecologically and morphologically distinct species differ in their facilitative effects.
A key feature of this system is the strong morphological contrast between primary and secondary habitat formers: a bivalve and seaweeds, respectively. Seaweeds substantially increase habitat heterogeneity by adding shelter, moisture retention, and settlement surfaces absent in the bivalve matrix, thereby enhancing invertebrate diversity and abundance.
The study compared two secondary habitat formers: the sheet-forming green alga Ulva sp. and the coarsely branched red alga Gracilaria chilensis.
PNZ2.jpgProject 2 — Multi-level habitat cascades in estuaries
This project extended the previous work by testing whether longer, multi-tier habitat cascades can occur in estuarine systems. Here, both secondary and tertiary habitat formers were seaweeds differing in species identity and morphology.
I investigated a potential four-level cascade involving the bivalve Austrovenus stutchburyi, the green alga Ulva sp., and the red alga Gracilaria chilensis. Although long habitat cascades are rarely documented, this project supports the hypothesis that they may be more widespread than currently recognised.
PNZ3.jpgProject 3 — Seagrass systems and drifting algae
This project shifted to seagrass-dominated soft-bottom habitats, where primary habitat formers were seagrasses and secondary habitat formers were drifting or entangled seaweeds. Compared to estuarine shell beds, both habitat formers are photosynthetic plants with more similar functional roles, suggesting potentially weaker cascade effects.
I described a habitat cascade driven by the interaction between the seagrass Zostera muelleri and drifting algae entangled within its canopy.
PNZ4.jpgProject 4 — Anthropogenic disruption of seagrass cascades
Building on Project 3, this study examined how human-driven stressors affect habitat cascade stability. Specifically, I tested how nutrient enrichment, eutrophication, and sedimentation influence seagrass performance and, in turn, cascade strength.
Increased sedimentation reduced seagrass health and destabilised the interaction between Zostera muelleri and drifting algae, weakening the associated habitat cascade.
PNZ5.jpgProject 5 — Rocky shore canopy-forming seaweeds and epiphytes
This project examined habitat cascades in rocky shore systems dominated by brown canopy-forming seaweeds, with epiphytes acting as secondary habitat formers.
I compared multiple Cystophora species to test how variation among structurally similar primary habitat formers influences cascade strength. Unlike previous systems, both primary and secondary habitat formers are seaweeds, allowing assessment of more functionally similar facilitative interactions.
PNZ6.jpgProject 6 — Habitat cascades and secondary production
This final project extended the rocky shore study by quantifying how habitat cascades influence ecosystem functioning, specifically secondary production. Unlike previous work focused on community structure (e.g., abundance and richness), here I estimated secondary production using allometric relationships between body biomass and temperature.
I demonstrated that habitat cascades involving Cystophora spp. and their epiphytes influence not only biodiversity but also ecosystem energy flow and productivity.
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