Session 8: Anthropogenic activity and the marine benthos

What is the “Blue Acceleration"?

Rapidly expanding human demand for ocean space and resources

(Global trends of human activities in ocean rapidly accelerating →moving to offshore/deeper env. too)

Why does sediments of the ocean matter?

Define Anthropogenic activity

An unprecedented expansion of human activity in the ocean has caused the connections between ocean health and people to become increasingly complex, diverse and dynamic

Climate trajectory and resiliance?

Changes in shrimp fisheries

Small nets → Big trawl nets

Small → Bigger boats

=> result in system collapse of shrimps due to overfishing

How historical activities not fit to current baseline?

If the current baseline is used, which incorporates historic activities, effects of the proposed project not likely be significant

[historical baseline shifted]

Changing perspectives in fisheries: What is Shifting baseline syndrome?

Incorporating historic perspectives changes the evaluation of environmental significance.

Extent of human impact

Changes at this scale will have dramatic consequences for ecosystem properties and functioning

• Pollution

• Habitat destruction and fragmentation

• Climate chnage

• Unsustainable resource use

• Species invasion

What is a stressor?

• "any physical, chemical or biological factor that requires a compensation response by affected organisms

• thus placing constraints on the productivity and development of ecosystems".

What does Trawling cause?

• Benthic environment destroyed and reduced

• Destroy habitat → local coextinction (e.g. Solenosmilia variabilis [stony coral] + oligotrophy fish that relies on it)

What does Mineral extraction cause?

• Billion tonnes of manganese nodules searched and extracted

• Removing nodules affects community structure

→ sediment washed, leaving nodules only to collect

What does Diamond mining cause?

• Off the coasts of South Africa and Namibia (Marine Diamond Corporation initiated by Sammy Collins)

Sediment fraction shifted → leaving coarser unmined sediment behind

What does Carbon sequestration cause?

Injecting liquid/solid CO2 into deep sea

→ Co2 cause high mortality of abundant sediment-dwelling metazoans e.g. 80% copepods + nematodes

What does Radioactive waste disposal cause?

Radioactive waste at sites in NE Atlantic

→ as Radionuclides e.g. Americium-241, taken up by benthic species like Hermione (polychaete) and Cirolana (isopod) at varying rates

→ Chernobyl fallout found bioturbated into Norwegian Sea sediments

→ Traces of radioactive material from vertical profiles through the water column in the NE atlantic found at >1000m depths

What do shipwrecks cause?

3700 ships lost in sea → 12.8 million tonnes of metals and others (10% hits abyss)

=> Toxic substances and fuels dumped into deep sea

=> Oil washed up to shore and over the ocean - kill birds and organisms

What is Sewage sludge?

Sewage sludge is composed of:

• silica (which flocculates)

• reactive organic materials

• organic nitrogen

• persistent organic pollutants (POPs) like PCBs

• heavy metals

• Inorganic solutes

• bacteria and human pathogens

What does dumping at sea cause?

E.g. Deepwater Municipal Dump Site 106 (DWD106) off New York (1986-1992):

• sewage particles settled over a massive footprint on the continental rise

• urchins eating organic material from sewage → entering the benthic food web

What does excessive N loading cause?

e.g. Qingdao, China

• Eutrophication - Massive algae bloom

• need to manually remove the algae (2-3 feet deep)

What is Hypoxia/Anoxia?

Cause coastal dead zones globally

Dissolved o2 reduce:

Mature communties (normoxia)→ mass mortality (hypoxia) → leaving laminted, lifeless sediments (anoxia)

How persistent are organic poullutants?

Pass down in the food chain (e.g. PCB conc.)

What does offshore infrastructure cause?

Change deposit → suspension feeding system

(Change is normal but it should not be happening here)

What do cables and pipelines cause?

Cables full of plastic, oils, and chemicals to allow conduction

→ pollutants

What are underwater sounds

Ship make underwater sounds (broadband noise)

2 types

• Continuous broadband noise (135 – 140 dB re 1 μPa)

• Impulsive broadband noise (150 dB re 1 μPa )

What do underwater sound cause?

Overlapping of noise (ships and wind mills) affects:

• marine mammals + fish communications

• sediment-dwelling invertebrates bioturbation and bioirrigation

What does Warming cause?

Cause cascading effects to productivity, distribution, phenology, interactions, ecosystem structure etc.

Examples:

What does UV radiation cause?

Direct DNA damage (dimerization, strand breaks)

Oxidative damage (Reactive Oxygen Species like H2O2), lipid peroxidation, and photoinhibition.

What does Littering cause?

Accumulating rapidly; degradation takes decades to centuries

e.g., plastic bags take 1-20 years, plastic bottles 450 years, fishing line 600 years

What does Pharmaceuticals cause?

Ingested by macrofauna → excreted and release from sediments

Why does the level of pressure not necessarily reflect exposure?

Microplastic burden depends on species traits and feeding
ecology within biogeographical provinces (deposit v.s. suspension)

How does a single human activity generate multiple impacts?

How do multiple human activities contribute to A SINGLE STRESSOR?

Cumulative effects of multiple stressors - how they interact?

Stressors = context- dependent

Interact in 3 main ways:

• Additive ( a&b = a+b)

• Synergistic (a&b > a + b)

• Antagonistic (a&b < a+b)

How multiple human activities generate multiple stressors?

Effects take time to be expressed