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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 …