Session 8: Anthropogenic activity and the marine benthos

What is the “Blue Acceleration"? (by Jouffray et al. (2019))

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

According to global patterns from 2008 to 2013, what percentage of national jurisdictions show increased human impact?

77%

In the study of cumulative effects, what is the mathematical formula for an additive accumulation of impacts?

$$a\&b = a + b$$

What are the mathematical representations for synergistic and antagonistic impacts?

Synergistic is expressed as a\&b > a + b

Antagonistic is expressed as a\&b < a + b

What were the percentages of additive, synergistic, and antagonistic effects found in individual laboratory studies?

Additive ($26\%$), synergistic ($36\%$), and antagonistic ($38\%$)

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? (by Paula 1995)

Incorporating historic perspectives changes the evaluation of environmental significance.

Extent of human impact in oceana

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

• Pollution

• Habitat destruction and fragmentation

• Climate change

• 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 is resource exploitation?

Exploitation of biotic and abiotic seabed resources are common,

with bottom fishing having the most extensive global footprint,

and deep-sea mining of metals from nodule grounds is as an area of increasing concern

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)

(scraping and ploughing, sediment resuspension, and physical destruction, removal, or scattering of non-target benthos)

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

To be economically viable, how many metric tonnes of nodules and sediment must a single mining unit process per day?

$5000$ metric tonnes of nodules and approximately $100,000$ metric tonnes of sediment

What is the potential tonnage of ore provided by the > 20\,million\,miles^2 of manganese nodules in the Pacific Ocean?

> 300\,billion\,tonnes

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

How many carats of diamonds are estimated to have been eroded from land and deposited into the ocean by rivers?

$$10\,billion\,carats$$

How many carats were produced by the Marine Diamond Corporation off South Africa between November $12$, $1961$ and January $5$, $1965$?

$$361,810.55\,carats$$

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

When was the voluntary moratorium on dumping radioactive waste in the North Atlantic agreed?

1983

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 are "rusticles" that form on shipwrecks, and what can they consist of?

Metal eaten away by bacteria and fungi, consisting of iron oxides and high levels of toxic metals and metalloids from ship paint

Which human activity is cited as having the most extensive global footprint on the seabed?

Bottom fishing (Trawling)

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 and sea cucumber eating organic material from sewage → entering the benthic food web

What three tracers were used to track where sewage from DWD106 settled on the seafloor?

Silver (from photographic/electronic industries), alkylbenzenes (from detergents), and spores from Clostridium perfringens (from faecal material)

What does excessive N loading cause?

e.g. Qingdao, China

• Eutrophication - Massive algae bloom

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

How does nutrient loading from agriculture disrupt the natural balance of marine systems?

It disrupts the balance between $N_2$ fixation and denitrification, leading to nitrogen accumulation and eutrophication which results in hypoxia

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 temperature can renewable power cables reach on the seafloor?

> 100^\circ C

At what depth and temperature does $CO_2$ turn into its liquid phase for sequestration?

At depths > 500\,m when temperatures are > 11^\circ C

What was the mortality rate for benthic copepods exposed to liquid $CO_2$ in Thistle et al. ($2007$) experiments?

~80%

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

What historical period and duration are used as the baseline for the Planetary Boundaries concept?

The Holocene, which is the last 11000 years

What are "Seeds" in the context of a "Good Anthropocene"?

Social, technological, economic, or social–ecological ways of thinking or doing

What is the umbrella concept of "Nature-based Solutions" intended to achieve?

To collectively use the features and complex system processes of ecosystems to achieve multiple benefits for nature, the economy, and society