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Flashcards in Marine Ecology Deck (43):

What affects O2 distribution in the ocean

Eutrophication and global warming


Describe the relationship between solubility of O2 and temperature

The concentration of dissolved oxygen when in equilibrium with the atmosphere decreases with increasing temperature


Where/how is O2 produced in the ocean

In sufficiently light surface waters phytoplankton photosynthesize


Where/how is CO2 produced in the ocean

Throughout the watercolumn by respiring organisms


Define thermocline

The transition layer between the warmer mixed water of the epipelagic zone and the colder deeper mesopelagic zone


Describe the vertical distribution of dissolved O2

In surface mixed layer
Equilibrate with atmosphere
Production through photosynthesis
Loss via respiration
Below thermocline
Can’t equilibrate with atmosphere
Loss via respiration
Supply via circulation


What is an oxygen minimum zone?

a zone where O2 saturation is at its lowest


What causes oxygen minimum zones

When water renewal very slow and/or
respiration very high


Define oxycline

a sharp gradient in oxygen


Describe the Oxic level

~ 250-300 mmol O2m-3 Normal aerobic respiration takes places


Describe the Hypoxic level

~ 60 mmol O2m-3 – fish, zooplankton stressed and actively select higher oxygen levels


Describe the suboxic level

5-20 mmol O2m-3. Denitrification : consumes nitrate, produces nitrogen
reduced zooplankton egg development


Describe the anoxic level

oxygen minimum zones and sediments). Sulphate reduction, production of hydrogen sulphide. Methane production from CO2


What is eutrophication and its consequences?

Run of of nitrates and phosphates leading to algal blooms which reduces the O2 concentration potentially leading to hypoxic conditions. Nutrient pollution is the single largest pollution problem affecting coastal waters of the United States (Howarth et al., 2000).


What two effects does global warming have on the oceans

Decreases solubility and increases stratification


What are the consequences of global warming on phytoplankton

Surface warming increases the density difference, or vertical“stratification” of the ocean waters, leading to
less mixing between the surface water layers,
where phytoplankton live, and the deeper water
layers, which contain the nutrients they need to


What are the 3 oceanic consequences of rising CO2 level?

acidification, warming and deoxygenation


What are the main causes of open ocean deoxygenation

a warming ocean, increased stratification and
changing circulation Keeling et al. 2010


Consequences of worsening hypoxia

Negative impacts on tourism, food security, ecosystem services and fish catch


Causes and effects of upwelling in the US

Intensified wind-driven upwelling related to atmospheric warming and its effect on the depth of waters with low oxygen and low pH, is bathing continental shelves in hypoxic, carbonate undersaturated waters along the US west coast (Freely et al. 2008)


Explain the process of OMZ expansion

Climate change causes the oceans to absorb more heat, resulting in less dissolved oxygen at the surface (decreased solubility) and increased stratification
of near-surface waters. This reduces subsurface mixing and transfer of atmospheric oxygen into the water column. . Alterations of oceanic circulation patterns can also reduce ventilation from within
the water column. Keeling et al. 2010


What are the 3 main changes OMZ expansion will have on microbial communities

Alteration of the N cycle, the emergence of sulfur (S) cycling, and the creation of new low-oxygen habitats. (Gilly et al. 2012)


Example of organisms who will be affected by OMZ expansion and why

It will lead to habitat compression for intolerant demersal, mesopelagic, and bill fishes and habitat expansion of hypoxiatolerant species such as the Humboldt squid. In general . Oxygen exerts tremendous control on marine biodiversity through effects on evolution, physiology, reproduction, behavior, and species interactions


What is the relationship between Atlantic OMZ shoaling and tropical pelagic fish

Shoaling may restrict the usable habitat of billfishes and tunas to a narrow surface layer. This habitat compression makes theses predators more vulnerable to surface fishing gear and may be associated with
a 10–50% worldwide decline of pelagic predator diversity. The expansion of the Atlantic OMZ along with overfishing may threaten the sustainability of these valuable pelagic fisheries and marine ecosystems.


What causes hypoxic coast lines?

Agricultural fertilizers leaking into the ocean where the
excess nutrients fuel plankton blooms, which
consume oxygen


What is the predicted O2 decline in the oceans

1-7% over the next century Keeling et al. 2010


Describe the hypoxic situation in Oregon

Off the coast of Oregon, oxygen content in the waters above the OMZ is declining, which may predispose the nearshore waters to hypoxia. As winds push surface water offshore, the low-oxygen, high-nutrient water wells up onto the shelf. The nutrients stimulate the growth of plankton, which use up oxygen when they die and decay. This is has been occurring annually since 2002 to varying degrees of severity (Gewin, 2010)


Consequences of ocean acidification?

It will reduce the habitat range of calcifying organisms
because the depth limit at which water becomes corrosive/under-saturated for aragonite or calcite will move upward.


What is argonite?

A naturally occurring, crystal form of calcium carbonate, CaCO3


How will increased stratification effect benthic biomes

Will reduce POC fluxes to the deep ocean which may further deprive food-poor abyssal plain or organic matter, lowering the benthic biomass.


What are the 2 main effects of stratification

Decreasing deep-water oxygen ventilation and reducing nutrient supply to surface waters from the deeper ocean, where organic matter is recycled


What are microplastics, specify types

nominally everything less than 5 mm in size
primary – produced in a micro-size range
secondary – fragments of larger plastic materials


What are macro/mesoplastics?

plastic nominally greater than 5mm


What effects does macroplastic have

Can entangle organisms wound, restrict movement, reduce ability to feed, reproduce and avoid predators. Also can be ingested which can suffocate, reduce/prevent feeding (Gregory 2009)


Which bulk plastics are buoyant?

polyethylene and polypropylene,


What happens to floating plastic in the ocean?

Floating debris tends to accumulate in the large
oceanic whirls, such as the North Pacific gyre


What is the estimation for the current amount of plastic in the ocean and who came up with it?

There are currently 5.25 trillion items of plastic
weighing more than 268,000 tonnes floating around in the oceans (PLoS One (2014)


Describe and explain the distribution of plastic waste

There is a similar distribution of floating plastic in both the northern and southern hemisphere gyres. This could be due too removal mechanisms such as plastic washing up on beaches is prevelant enough to keep the distribution equal, even though the north produces more plastic.


What is biofouling

The accumulation of biological organisms on wetted surface


How could plankton potential reduce plastic waste?

Biofouling may eventually induce the particles to sink
and end up in sediments although whether this route is an important mechanism for the removal of microplastics from surface water is still unclear
Some bacteria have genes that allow for the degredation of hydrocarbons, though it is unclear whether it is at a fast enough rate to be significant


What kind of organic pollutants adsorb to microplastics?

polychlorinated biphenyls (PCBs), organochlorines, polycyclic aromatic hydrocarbons (PAHs) and DDTs


Discuss the relationship between polyethylene and organic pollutants

The widely used polyethylene has a high propensity to pick up pollutants, which isn't necessarily a bad thing if it sunk and got stored in the sediment. However they are more likely to act as carrier and introduce the pollutants into the food web


How do microplastics effect the environment?

They concentrate low-level pollutants in water. ► These become bioavailable via ingestion to marine organisms.