Case study AssignmentCourse: Marine Extreme System

Presented By Islam Md Jakiul

Ploughing the deep sea floorObjectives

To focus on bottom trawling effects on deep ocean floor

Results Bottom trawling have direct impact on fish

populations and benthic communities Also modify the physical properties of seafloor

sediments, water-sediment chemical exchanges and sediment fluxes

Reworking of the deep sea floor by trawling gradually modifies the shape, morphology of the deep sea floor become smoother over time

Following modernization of fishing techniques, bottom trawl net become an important driver of deep seascape evolution

Researcher anticipate that the morphology of the upper continental slope in many parts of the world’s oceans could be altered by intensive bottom trawlinghttp://www.newindianexpress.com/

Ploughing the deep sea floorIn the upper portion of continental slope the morphological complexity, as well as

benthic habitat heterogeneity, has been drastically reduced, potentially affecting species diversity by regulating levels of competition, predation and physiological stress

Huge volume of sediment that can be remobilized downslope by trawling activitiesBottom trawling has been compared to forest clear-cuttingThe frequent repeated trawling (ploughing) over the same ground, involving

displacement of sediments owing to mechanical redistribution

Underwater trawled continental-slope equivalent of a gullied hill slope on land, part of which has been transformed into crop fields that are ploughed regularly, thus replacing the natural contour-normal drainage pattern by levelled areas with a smaller-scale contour-parallel alignment of troughs and crests

Although farmers usually plough their land a few times per year, at sea trawling can occur on a nearly daily basis

Conclusion and criticism

Ploughing the deep sea floorRelated Article

Palanques, A., Puig, P., Guillén, J., Demestre, M., & Martín, J. (2014). Effects of bottom trawling on the Ebro continental shelf sedimentary system (NW Mediterranean). Continental Shelf Research, 72, 83-98.

ResultsTrawling affects the morphology of the seabed

Trawling produces an upward increase of the silt and the organic carbon content in the sediment column

Trawling generates significant turbidity peaks mainly during working days.

Resuspension by trawling more than doubles the suspended sediment load of the Bottom nepheloid layer.

Silt content and median grain size of the surface sediment samples from

he trawled and untrawled area

Objectives To study the physical changes induced by trawling, analyzing seafloor

morphology, sediment characteristics and turbidity in trawled and un-trawled zones

Ploughing the deep sea floorRelated Article

Trawling affects the distribution of silt content as well as organic carbon content.

Vertical distribution of the average silt content and median grain size from trawled and untrawled area

Vertical distribution of the average organic carbon content from trawled and untrawled area

Trawling is altering the modern sediment dynamics inducing the export of additional sedimentary supplies off-shelf.All these effects induced by trawling have occurred during the last few decades, changing natural conditions in the fishing

ground.

Tighten regulations on deep-sea mining

Objectives

This article discussed on necessity of tight regulations for deep sea mining to protect deep sea vents and theirs peculiar biodiversity

Key messages and results

Deep sea vents are underwater hot springs in volcanically active areas of the Pacific Ocean floor.

These hydrothermal vent support bacteria that use chemicals erupted from vent fluids to generate cellular energy.

At deep sea barren area, this bacteria feed so many luxurious and beautiful invertebrates

Additionally this deep sea vents are rich of minerals e.g. Zn, Cu, Ag and Au

With the ever increasing demand to fulfill life style and advancement of sea mining technologies, deep sea mining likely to be inevitable.

To avoid/minimize the mining effects scientists need to promote conservation at every levels- from government to mining companies

Tighten regulations on deep-sea mining Continuing research since last three decades researchers continue to find new vent

sites in remote locations and new species, adaptations, behaviors and microhabitats, even in well-known settings

There is much more to learn about hydrothermal vents, still now no strategies to assess the cumulative impacts of mining and researchers still don’t know the best way to mitigate mining activities

Government agencies and International Seabed Authorities(ISA) should function properly for deep sea mining

It’s a urgent need to establish conservation guidelines in functioning governance and regulatory frameworks

Sea-floor hot springs remain pristine should kept touched by mining. But for unavoidable reasons its scientific value must be weighed against other values, including economic ones

Human may choose to threaten these unique habitats for development and to feed unlimited lifestyles that depend on relentless demand for minerals and other resources.

Conclusion and criticism

Tighten regulations on deep-sea miningRelated Article

Lodge, M., Johnson, D., Le Gurun, G., Wengler, M., Weaver, P., & Gunn, V. (2014). Seabed mining: International Seabed Authority environmental management plan for the Clarion–Clipperton Zone. A partnership approach.Marine Policy, 49, 66-72.

Context The main deep-sea mineral resources are: Polymetallic nodules, Manganese

crusts, Polymetallic sulphide deposits Distinct ecosystems are or can be associated with these minerals and will be

affected in different ways by different types of mining. Dredging for nodules is likely to damage large areas of the seabed and

disperse large clouds of sediment. Polymetallic sulphide mining may destroy active and inactive hydrothermal

vents (black smokers) and their associated communities and disperse toxic materials.

The extraction of cobalt rich crusts may destroy the benthic seamount communities and dependent fauna.

Objectives To understand the hydrothermal vents, its biodiversity, and consequence of

deep sea mining on it.

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Tighten regulations on deep-sea mining

Deep-sea mining may result in the destruction of seabed communities at or near the mining site, offsite impacts due to the dispersion of toxic and particulate material in ocean currents and from sea surface discharges, and due to accidents involving mining gear and support vessels.

Potential negative impacts of deep-sea mining include Loss of habitat Degradation of habitat quality Decreased seafloor and/or water column primary production Modification of trophic interactions Decreased diversity Local, regional, or global extinction of endemic or rare taxa

Deep-sea mining activities should not commence before measures are in place to protect deep-sea ecosystems from adverse impacts

Until a strict governance mechanism is set up and adhered to that allows for all countries to benefit at an equal footing from deep seabed resources in areas beyond national jurisdiction is set up and adhered to, there are also potential socio-economic consequences

Conclusion and criticism

Deep carbon export from a Southern Ocean iron-fertilized diatom bloom

Objectives This article discussed on rules of iron into the oceans in the face of

climate change.

Context

Ocean Iron fertilization is the deliberate introduction of Fe to the ocean surface to fuel a phytoplankton bloom.

This is envisioned to increase biological production, which benefit the oceanic food chain and hopes that of increasing CO2 abstraction from the air.

Fe is consider as a trace element required for photosynthesis in all plants. It’s greatly insoluble in marine water and is frequently the limiting nutrient for phytoplankton progression.

Huge algal blooms can be formed by providing Fe to iron scarce ocean waters.

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Results Fe fertilization as a means to sequester CO2 from atmosphere to deep ocean, and to upturn oceanic

biological production which is probable in decline for climate change Fertilization may occur when weather brings wind blown dust from a long distances above the

ocean, or Fe rich mineral deposits are carried into ocean by glaciers, rivers and icebergs. Fertilization of the deep-sea by addition of Fe rich compounds has prompted diatom dominated

blooms escorted by considerable CO2 drawdown into the ocean surface. Growth of numerous diatom species displayed 97% Chl increase, and dropping was initiated by

massive death and swift sinking which was compensated by others species. 50% of the bloom biomass sank far beneath a depth of thousand meter and that a considerable

portion is likely to have gotten the ocean floor. Thus, Fe-fertilized diatom blooms may act as carbon sequester for timescales of spans in oceanic bottom water and in the sediments for longer .

Sinking of accumulated cells and chains in the decease phase of diatom blooms similarly occurs in the open Southern Ocean, both in natural and artificially manured blooms

Findings recommended that Fe insufficiency is not only merely impacting ocean ecosystems, it also offer a key tools to mitigate climate change as well.

If phytoplankton convert all the NO3- and PO4 in existence of Fe in the shallow mixed depth through the

whole “Antarctic Circumpolar Current” into organic carbon, the resulting CO2 scarcity could be recompensed by uptake from the atmosphere

Conclusion and comments

Ocean Iron FertilizationRelated Article

Buesseler, K. O., Andrews, J. E., Pike, S. M., & Charette, M. A. (2004). The effects of iron fertilization on carbon sequestration in the Southern Ocean. Science, 304(5669), 414-417.

Context The Southern Ocean plays a key role in the climate system, and is known as

the marine body utmost sensitive to climate change Phytoplankton bloom observed induced by naturally iron fertilization. With a

view to overcome some of the limitations of associated with temporary experiments.

The availability of iron limits have great impact on primary productivity and on the associated uptake of carbon over huge areas of the deep-sea.

Thus Fe plays an vital role in the earth carbon cycle, and alterations in its supply to the ocean surface have a significant impact on atmospheric carbon dioxide concentrations over glacial and interglacial cycles

Objectives To investigate o the effect of natural iron fertilization on carbon

sequestration in the Southern Ocean “Iron fertilization of its surface waters during

glacial times by enhanced

dust deposition is a scenario (known as

the ‘iron hypothesis’) proposed to explain lower atmospheric CO2 during colder

climates”(Martin, 1990).

Iron hypothesis

Results

This result sheds new light on the effect of long-term fertilization by iron and macronutrients on carbon sequestration, suggesting that changes in iron supply from below as invoked in some palaeoclimatic and future climate change scenarios may have a more significant effect on atmospheric carbon dioxide concentrations than previously thought.

Conclusion and comments

A large phytoplankton bloom was found over the study area in the Southern Ocean, was consistent by Fe and major nutrients supply to water surface from Fe-rich deep water beneath.

Addition of iron results ten times higher carbon export at the investigation areas.

Carbon can be exported up to 1000 meters, POC content also increase as a result of iron fertilization.

The higher carbon sequestration efficacy of the natural bloom in contrast to mesoscale iron adding experimentations arises from differences in the sequestration efficiency ratio.

Carbon export at A3 and C11.Profiles of 234Th activity at A3 (red lines) and C11 (blue lines).