Marine Ecology Flashcards
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
flourish.
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.
