Week 6- Organism-sediment interactions and succession

Recall the early sequence of early work related to benthic organisms

1. Recognition that fauna occurred in zones/regions

2. Described/categorised fauna occurring in zones

3. Organism-sediment interactions

What organism-sediment reactions were observed at Cape Cod Bay, Massachusetts, US

• Transition in fauna from inshore sand to deeper water muds

• Silt-clay intensively reworked deposit feeders, fewer suspension feeders

• Irregular bottom topography produced by holuthurian molpadia oolitica

What is Molpadia ooltica like

• Forms cone shaped faecal mound

• Stabiliser

• Verticular upward conveyor

• Intercone depressions

How does fauna influence the sediment

Organism- sediment- fluid- chemical interactions

Influence all at same time- continuous

How does particle sorting work

Fundamentally changes sediment properties

Finer material is bought to the surface

Set up an organic gradient

What is burrow construction and ventilation

RAefers to the way animals build and manage underground shelters (burrows), focusing both on how they dig and structure the burrows and how they ensure airflow to support breathing, temperature control, and waste gas removal

What do infauna influence

Physical, chemical and biological environment all at the same time

What do physical, chemical and biological parameters influence

Infauna

Who underpinned/summarised organism-sediment reactions

John Gray and Donald Rhoads

• Both missed parts of eachothers out

What did Gray say about organism-sediment relations

Attempted to relate individuals, populations and communities to sediments

• Took view rhat selecton takes place at larval stage and is then modified by environment

What did gray mean by organism sediment couple

Selection by larvae or adults of suitable sites

and

Population modifies sediment in turn leading to temporal and spatial changes in population

= Community structure therefore can be loosely related to sediment composition but exact constitution may be radically altered by interactions between organisms and sediment

What did Rhoads say about organism sediment coupling

Influenced by in situ observations of fauna

Invented SPI

What did Gray say about ecological significance

A community must be composed of species which interact with each other and the environment and a community has, therefore, an ecological basis

Where could you find evidence to support or refute the concept of benthic succession

• Fossil records

• Historical record

• Environmental gradient

• Galway Bay and loch creran pollution studies

What was Bagges evidence from environmental gradients

Compared sequence of communities in polluted estuaries in the Skagerak Baltic region

Compared assemblages before/after onset

What are SAB curves

SAB curves typically refer to Species-Abundance-Biomass curves, used in ecology to visualize and compare the relationships between:

• Species abundance (how many individuals there are of each species),

• Species biomass (the total mass of those individuals), and

• Biodiversity structure in an ecosystem.

What are the effects of organic enrichment

Organic enrichment refers to the increase of organic matter (like decaying plant or animal material, sewage, or food waste) in an ecosystem—usually aquatic or soil environments.

• Lots of food

• Microbes go crazy

What organisms would you find in different levels of enriched soil

Less - Amphiura, sea pen, nephrops

Medium - Thyasria, Pectinaria, Labidoplax

Very - Capitella, Scolelepsis

What is the Pearson-Rosenberg model of succession

Graphical depiction of moderate succession with interactions

What is succession related to hypoxia like

organic enrichment → hypoxia → disturbance → triggers ecological succession

What is Cranfields biogenic habitat regeneration model

Focuses on understanding how benthic (seafloor) habitats, particularly those formed by living organisms like shellfish, recover after disturbances such as intensive fishing. This model was developed based on studies in Foveaux Strait, New Zealand, where overfishing had significantly degraded oyster reefs

What happened when Snelgrove and Butman critically reviewed OSI literature

OSI relationships tend to be more variable tham traditionally reporteed

Multiple variables correlate woth sediment type

What did Snelgrove and Butman conclude

Paradigms of succession are derived from limited experimentation or correlative field sampling and clearly are inadeqaute as explanations or predictive tools

Does benthic succession exist

Each represents a potential successional endpoint that can persist over time as a recognisable community type within the domain a prevailing environmental conditions