Download Aquatic Biomes, Part I – Marine Biomes

Aquatic Biomes, Part I – Marine Biomes
Introduction
Extent of Marine biomes
Issues & challenges
Factors influencing distribution
Dynamics in time & space
Depth
Tour of marine biomes
& Issues (by biome)
Readings: Chapter 3 (esp. pp 50-69)
Molles & Cahill
2008
Distribution of Water in the Biosphere (“Ecosphere”)
“Water, water, everywhere, nor any drop to drink.” – Coleridge
Rime of the Ancient Mariner
Mackenzie 2003
The Hydrological Cycle
Fig. 3.2, Molles & Cahill, 2008
Importance of marine systems
Biogeochemistry – oceans have significant fluxes of several climatically
important gases (CO2, N2O, dimethyl sulfide).
CO2 storage - oceans represent a large CO2 reservoir (65 times the atmosphere)
Weather & climate – Small changes in the ocean have large impacts on global
weather and climate systems
Productivity - Roughly half of the world’s primary productivity occurs in the
oceans
Diversity - Biologically, oceans are species-rich
Food supply - Oceans are a critical food source for much of the human population
Oceans both buffer us from climate
change, and cause climate change
Oceans can take up large amounts of heat and
gases from the atmosphere (buffering us from
climate change)
Relatively small changes in ocean circulation
have large impacts on the atmosphere and the
biosphere (causing climate change)
.
Challenges to understanding marine systems
Physically, the oceans have a “long memory” (slow to respond)
Oceans are vast (70% of Earth’s surface, 11,000m deep)
Marine systems are largely “invisible” (below the surface)
– we know relatively little about this realm
Inherent variability of marine systems – oceans are very dynamic
Human impacts (direct and indirect) are altering aquatic biomes,
including oceans.
Human impacts on marine biomes
Human have many impacts on marine systems, both direct & indirect
Coastal development
Pollution
direct
Marine fisheries
Coral Reefs
Temperature
CO2 & pH
indirect
Sea level rise
Stratospheric Ozone depletion
Human impacts on marine systems
Indirect (e.g. atmospheric and climate change)
- Increasing ocean temperature, sea levels
(very slow, due to long ocean memory).
-Ozone hole events reducing marine primary productivity
- Ocean acidification due to increasing atmospheric CO2
Direct impacts (especially in coastal regions)
- Altered runoff (stream diversion, damming)
- Pollution (runoff and dumping)
- Toxic algal blooms (“red tides”)
- Altered coastal habitats (development, destruction…)
-Overfishing
Challenges to protecting oceans – marine laws are weak
The distribution of aquatic biomes (fresh and saltwater) is largely
determined by temperature, salinity, and nutrients
(affected by currents, mixing…)
Campbell & Reece 2002
Temperature and light penetration with depth further affect productivity and the
distribution of organisms
“pelagic”
“benthic” = bottom
“abyssal”
Fig. 3.6
Molles & Cahill, 2008
The open ocean – “pelagic zone” – the most extensive biome on Earth.
Molles 2008
Deep ocean currents are driven by thermohaline circulation
Thermohaline circulation
in the North Atlantic
The switching on and off of the
Atlantic thermohaline circulation
causing different modes
of planetary operation associated
with glaciation/deglaciation
Source: Locthe, 2005.
(Rahmstorf 2001)
Surface ocean currents influence species distribution and marine productivity
Surface currents are affected by wind & the Coriolis Effect
Molles 2008
Global Net Primary Production from Satellite-Driven Models
eflectance
luorescence
mission
bsorbance
Oceans: 46%, Land 54%
Field et al. 1998
Cited in Krebs
2001&(fig
ransmittance
Gamon
Qiu25.3)
1999
Ocean chlorophyll concentration and
surface temperature off the California coast
Phytoplankton blooms
(orange color on left image)
correspond to cool regions
(blue color on right image).
This is due to upwelling that
brings cold, nutrient-rich water
to the surface, boosting NPP
along the California coast.
Molles 2008
Figure 22.28
Oceans are highly structured, yet inherently dynamic
http://www.cinms.nos.noaa.gov/marineres/MRWG_SP_ED/ppframe.htm
http://www.cinms.nos.noaa.gov/marineres/MRWG_SP_ED/ppframe.htm
http://www.cinms.nos.noaa.gov/marineres/MRWG_SP_ED/ppframe.htm
http://www.cinms.nos.noaa.gov/marineres/MRWG_SP_ED/ppframe.htm
Fish populations are inherently variable,
confounding our understanding of human impacts
Botsford et al. 1997
We now know that some of this variability is tied to periodic
atmospheric and oceanic circulation patterns
Fish catches of 11 commercially important species show a strong
relationship with the Atmospheric Circulation Index (ACI, black
lines, a periodic index of atmospheric pressure and circulation
that affects energy transfer to the oceans). The fish can be grouped
in catches in phase or out of phase with the ACI.
(modified from Klyashtorin 2001)
Oceans are highly variable,
with many periodic phenomena affecting fisheries
(Pacific Sea Surface Temperature and El Nino/Southern Oscillation)
The Pacific Decadal Oscillation (PDO):
a newly discovered oscillation affecting fisheries
warm phase
cool phase
Typical wintertime Sea Surface Temperature (colors),
Sea Level Pressure (contours) and surface windstress (arrows)
anomaly patterns during warm and cool phases of PDO
http://tao.atmos.washington.edu/pdo/
North Pacific Subtropical Gyre – the largest ecosystem on the planet
Prochlorococcus, the most abundant
oxygenic phototroph in the NPSG,
was first described around 1990.
Other novel Bacteria, Archaea, and
Eukarya have not yet been isolated
(described only by nucleic acid
sequences).
NPSG
Karl (1999) Ecosytems 2:181-214.
Distribution of animal phyla among terrestrial,
freshwater and marine environments.
Note high
level of
endemism
Fig. 3.9, Molles & Cahill 2008
Temperature and light penetration with depth further affect productivity and the
distribution of organisms
“pelagic”
“benthic” = bottom
“abyssal”
Fig. 3.6
Molles & Cahill, 2008
Epipelagic zone (also, the “photic zone” – where light is sufficient to drive photosynthesis)
Molles & Cahill, 2008
An ecosystem of chemotrophic organisms at the bottom of the ocean.
Molles & Cahill 2008
Creatures of the deep!
Molles & Cahill 2008
Coastal Biomes – Kelp “forests” and coral reefs
Molles 2008
Kelp beds (cold waters)
J. Gamon
Molles 2008
Coral reefs
warm, tropical regions
Molles 2008
Coral Reefs (warm waters) - biologically diverse
Herbivory by sea urchins maintain corals (suppress algae) in many reef ecosystems
Fig. 3.17
Molles & Cahill 2008
Harmful human impacts on coral include:
•
•
•
•
•
•
Increased ocean temperature
Increasing CO2 & reduced ocean pH
Sea level changes (ENSO, sea-level rise)
Increased UV radiation levels
Siltation and pollution (runoff)
direct
Dynamiting (fishing, roadbuilding)
indirect
Anthozoan corals are mutualistic symbioses between colonial
cnidarians (class Anthozoa) and symbiotic algae (“zooxanthellae”).
This symbiosis is very
sensitive to temperature.
Kinzie & Buddemeier 1996 Global Change Biology 2:479-494
Pocillopora damicornis
Saboga Reef, Pearl Islands, Gulf of Panama
Normal pigmentation
Partial bleaching
Full bleaching
(1982-83 El Nino,
temperature 1.5oC
above normal)
Glynn PW (1996) Global Change Biology 2:495-509
To be continued …