Marine Zoology & Ecosystems: Hard Sediment

Environmental factors

Substrate type

Sediment transport

Productivity regime

Hydrodynamics

Depth

Disturbance

Substrate characteristics

Rock type, texture, complexity, stability & orientation

determine what organisms can attach/live there

Affect habitat suitability for marine organisms

Hydrodynamic forces & light

Wave exposure, currents, tidal regimes & light availability

Influences species zonation & nutrient flow

Abiotic factors:

Temp & salinity fluctuations

Affect species distribution & physiological tolerance in marine habitats

Biotic factors:

Competition & predation

Anthropogenic Impacts

Over harvesting, pollution/eutrophication

Alter community structure & biodiversity in marine ecosystems

Submarine canyons:

Investigate Northwest Atlantic vulnerable marine ecosystems (VME)

To understand eco-hydrodynamic & sediment drivers of macrofaunal diversity

Sediment regime

dynamics: turbidity currents & tidal flushing

turbidity- nepheloid layer

accumulation of organic matter in deposition zone within canyons

community composition

246 taxa, 15 phyla

bimodal density distribution in canyons vs slopes

biomass decreases with depth in canyons, increases with depth on slopes

overall deep-sea pattern: abundance decreases with depth

Hydrodynamics:

studies movement of water through waves, currents, tides, internal waves & turbulence

Hydrodynamics: hard sediment

water movement- dominant environmental driver

influences nutrient delivery, O2 availability, larval supply & settlement, sediment transport, species distribution (zonation)

Zonation

patterns of species distribution across depth or hydrodynamic gradients

species distribution

How traits affect ecology: surface texture

rough, complex surfaces trap larvae & biofilms

How traits affect ecology: chemistry

reactive minerals attract or deter settlers

How traits affect ecology: stability

affects succession- unstable/eroding surfaces favour opportunists

How traits affect ecology: Orientation

orientation changes desiccation & flow exposure

Predicting ecological outcomes: Early colonisers: Natural rock

Bacterial biofilm → microalgae (diatoms) → sessile inverts

Predicting ecological outcomes: Early colonisers: biogenic

Bacterial biofilm & crustose coralline algae/encrusting sponges

larvae of corals, oysters, calcifiers

Predicting ecological outcomes: Early colonisers: artificial

bacterial biofilm → opportunistic fast colonisers

Predicting ecological outcomes: long-term community: Natural rock

Macroalgae (kelp), grazing inverts (limpets), dense mussel beds

Predicting ecological outcomes: long-term community: biogenic

complex 3D reef with epibionts, cryptic species, borers (spongers), symbionts

Predicting ecological outcomes: long-term community: artificial

lower evenness & structural complexity unless intentionally textured

dominated by non-calcifying fouling species

Predicting ecological outcomes: feedback process: natural rock

Rugosity/crevices retain moisture & reduce morality for later settlers

Canopy macroalgae alter light & flow- creating understorey microhabitats

Predicting ecological outcomes: feedback process: biogenic

Calcification builds structure → promotes more settlement

simultaneously bioerosion & dissolution reduce structure (-ve feedback)

Predicting ecological outcomes: feedback process: artificial

chemistry can alter biofilm

absence of natural microcrevices limits niche diversity

Natural rock

promotes slow, stable succession

granite/basalt

Biogenic

enables chemically mediated, fast colonisation but fragile

coral skeletons

Artificial

simplify communities unless modified

concrete

Foundation species

organisms that create, define & maintain habitat through physical structure

Kelp forest: structural trait

holdfast: tall, flexible fronds, dense canopy

Kelp forest: abiotic effect

reduces light & flow

Kelp forest: Biotic outcome

creates shaded refuged for invers/fish; suppresses understorey algae

Coral reef: Structural trait

rigid CaCo3 skeleton

Coral reef: Abiotic effect

alters hydrodynamics: buffers wave energy

Coral reef: biotic outcome

3D complexity supports fish/inverts; high biodiversity

Mussel bed: Structural trait

Dense, byssally bound shell matrix

Mussel bed: abiotic effect

traps sediment, retains moisture

Mussel bed: biotic outcome

provides habitat for infauna; reduces desiccation; increases small-scale diversity

Sponge garden: structural trait

vertical, porous bodies

Sponge garden: abiotic effect

filter water, modifies nutrients

Sponge garden: biotic outcome

increases microbial productivity; creates substrate for epibionts

Layers of life: Surface dwellers role

Primary production (algae)

Suspension feeding/space competition (barnacles)

Layers of life: Interstitial species role

Detritovores

Transferring energy as prey for larger predation

Layers of life: infauna role

Bioturbation

Nutrient remineralisation

Layers of life: borers

Bioerosion

Carbonate cycling

Creating microhabitats

Contributing to structural weakening

How does vertical habitat partitioning increase biodiversity in hard substrates:

Different layers support distinct species

Each layer offer unique microhabitats & resources

Functional roles vary by layer

Reduces competition by spatial separation

Enhances overall ecosystem complexity & resilience

Kelp canopy->function->service:

primary function → carbon storage & habitat

Coral reef->function->service:

3D habitat & carbonate accretion → shoreline protection

Mussel bed->function->service:

Filtration → water clarity & nutrient cycling

sponge garden->function->service:

nutrient cycling → water quality & microbial food web

artificial->function->service:

refuge → biodiversity enhancement

What happens when foundation species lost/replaced

removal shifts structure-function networks → loss of microhabitat complexity & ecosystem services

Can ecosystem functions recover without original structure:

partial recovery possible via opportunists

lacks 3D habitat or long term stability

Study→ removing dead coral= 5x great coral densities after marine heatwave

How can humans intervene to enhance resilience/restoration

active restoration: coral gardening

eco-engineering: biodegradable reef blocks to mimic natural heterogeneity

assisted adaptation: selecting heat tolerant coral

management leverage: marine protected areas