Challenges to Marine
Richard Norris; SIO-UCSD
Major challenges to Marine
Direct human impacts (immediate effects)
• Reduce biodiveristy & resilience
• Both top-down and bottom-up impacts
• Reduce mobility in face of climate change
Human environments
• species poor
• short food-chains
• disturbed
• have imported energy and
Major challenges to Marine
Indirect human impacts (long-range
impacts) due to Global change
• Acidification
• Stratification
• Altered PPT patterns
• Storm and sea-level impacts on coasts
Keeping Perspective
Consider the nature of impacts that
would exist under a business-as-usual
Partial solutions may be preferable to no solution
…But there are worries that partial solutions will sap
political will to act
Three types of Geo-engineering
Albedo enhancement
Reflectors, Cloud production and Ground-based albedo
Land-based Carbon Sequestration
CO2 into oil wells, saline aquifers, Enhanced
Ocean-based Carbon Sequestration
Ocean dumping of CO2, Biochar, Nutrient fertilization,
Enhanced weathering
Can also think about just
two categories
Methods that change the chemistry of
• These typically address the acidification issue
as well as climate change
Those that do not….
• Usually only deal with temperature
Albedo-enhancing Geoengineering Consequences
Common themes—no reduction of:
• CO2 absorption in ocean
• environmental loading of other waste
products of fossil fuel burning—NOx, SOx,
trace metals (many of them heavy metals)
NOx already a problem in coastal water ways
• Carbon-particulates (ash)
Reflectors in space
Changes albedo at the top of the atmosphere
• Because these are in space, the main impacts on
ecosystems come from potential changes in weather
systems, ppt, land-sea contrasts, and continued
• Diminished UV may also affect composition of surface
ocean phytoplankton
Reflectors in space
Impacts from changes in weather
• Severity related to shifting ‘natural’ processes into new frequency,
geographic position, or stable states.
• Mucking around with the PDO, NAO and other multi-decadal
• e.g. Mantua et al. 1997, Bull Am, Met. Soc
• Of course, all these happen anyway with global change.
Cloud Seeding with Salt Spray
Increasing cloudiness:
• Changes community structure toward low-light intensity communities
with potential impacts on export production;
Clouds may affect air-sea temperature contrast
• Storm intensity & evaporation weakened (Mahmud 2009 Singapore J
Trop. Geography)
• Implications for nutrient exchange between thermocline and surface.
• Create a permanent, local el-Niño?
Shepard et al. 2009
after Latham et al, 2008
Some other impacts of
cloud ‘whitening’
Water removal could affect:
• Larval abundance and viability (like desalination plants)
Permanent installations
• Act as giant open-ocean habitats (Fish Aggregation Devices) for
highly-migratory fishes and marine mammals
SO2 addition to atmosphere
Acid rain
Sure, but the ocean is big and relatively well mixed
More of a problem for poorly buffered terrestrial systems
BUT, deposition on snow or ice could create a runoff acid pulse
to coastal waters—problematic for Arctic, Antarctic…
SO2 addition to atmosphere
Ozone destruction
• increases UV influence in surface ocean
• but ocean absorbs UV efficiently
• Experiments show some diatoms (Pseudonitzschia) do well in high UV waters (Mengelt &
Prezelin (2005) Mar-Ecol. Prog Series)
• UV also reduced overall phytoplankton
production (Llabres & Agusti 2010 Aquatic Microb. Bio;
Finkel et al. 2010; J. Plank. Res)
• Could be a problem for seabirds, seal colonies (walrus, fir
seals, elephant seals…)
These seem unlikely to have a major impact
on marine communities
• Unless they alter weather
• Water runoff
• Sediment and nutrient transport by wind, streams or
dissolved ground water flows.
Ocean-based C-Sequestration
Major impacts from land-based enhanced weathering:
• Could change the flows of dissolved compounds (like
bicarbonate ion) and cations into ocean water.
• Waste streams are likely to be concentrated
• Have many of the same impacts as saline outfall from desalination
• Could offset ocean acidification
• But this depends upon where outfall is delivered
• Local alkalinity spikes might contribute to ‘whitings’
Trace metals are the problem
• Peridotite is not a completely benign substance
• due to imbalances in Mg/Ca ratios
• High concentrations of Ni, Co, Cr; low Mo
• A “serpentine barrens” of the sea?
US Forest Service
Enhanced Weathering
Dumping effluent from enhanced weathering like
other waste streams
• Tend to produce reduced biodiversity & short food
Ocean-based Carbon
Consumption of other bio-limiting nutrients
• Causes Fe-fertilization to ‘rob’ downstream
communities of nutrients
Shortening food chains
• Changes in marine community structure depending
upon type of phytoplankton production
• increased primary production would likely shorten
food chains and reduce biodiversity.
Nutrient Fertilization
O2 consumption
• Impacts of doubling c-flux to the sea floor on
benthic communities
• Ocean O2 (Keeling et al. 2010, Ann Rev Mar. Sci; Shaffer et al. 2009
Nature Geosci)
• Models already predict up to ~60% volume of ocean
affected by ocean hypoxia in coming millennia
• A return to the Cretaceous?
Ocean-based Carbon
Biochar storage in the ocean
• Potential habitat for wood-loving taxa;
• if stored as wood or biomass has short lifecycle owing to ship
worms (>> Century)
Geo-engineering-final thoughts
• CO2 removal either by political will or technology
deals with most problems
• CO2 dumping in ocean could be problematic if
not neutralized by carbonate or buried.
• From a biodiversity perspective, solutions that
leave acidification in place are the most
dangerous (e.g. albedo enhancement)
• But, in short-term, direct human impacts are the
major threat

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