Today: Productivity in the marine world Food webs and trophic levels Chemotrophic communities Dinner Time! Yum Yum Oceans are brimming with life Not a lot of diversity But a great abundance of organisms And very efficient producers (protista or plankton) Sat. image of chlorophyll Production = synthesis of organic molecules from inorganic compounds (autotrophs) 1
Primary Producers = base of food web Primary Producers synthesize organic molecules from inorganic nutrients (phytoplankton) Feed other organisms (zooplankton) Most are photosynthetic - previous map of chlorophyll = map primary production How do they produce Photosynthesis Sunlight + 6CO 2 + 6H 2 O => chlorophyll => glucose (C 6 H 12 O 6 ) + 6O 2 Glucose is used by both autotrophs and heterotrophs to Grow the organism Energy in Respiration Respiration How organisms get energy from glucose (C 6 H 12 O 6 ) + 6O 2 => 6CO 2 + 6H 2 O + Energy (H) 2
Biomass & Productivity Biomass = mass of organic matter (grams) Gross Primary Production: This is the total biomass synthesized by photosynthesis & chemosynthesis Net Primary Production: Gross P.P. - biomass consumed by respiration Net P.P. is the biomass available for consumption Productivity in oceans Chlorophyll content = productivity of photosynthetic organisms (mostly phytoplankton) Note: not the same everywhere High on some parts of coasts Higher at high latitudes What causes variations in productivity? Average annual chlorophyll 3
Requirements for productivity: Sunlight: Most primary producers are photosynthetic Live in photic zone Nutrients: Nitrogen & Phosphorous must be available N (as nitrate or NO 3 ) Used in making proteins = building blocks of life P as phosphate (PO 4 ) Required for DNA Use to make cell walls Required in Respiration Stable water column No vertical mixing when nutrients are present Average Global Primary Production Where is productivity (chlorophyll) highest? Coastal areas, high latitudes and equatorial Pacific 4
Production in Coastal Areas Estuaries have high nutrient levels due to (1) river input and (2) recycling of nutrients due to flow of fresh and salt water. Ekman flow results in coastal upwelling that brings nutrients to surface Equatorial Pacific Pacific Surface water diverges at equator, bringing nutrients to surface Notice areas of convergence (gyres) have low productivity 5
Productivity vs. Latitude: High Latitude Short summer But, long summer days Big Bloom - Why so big? Nutrients brought to surface during winter overturn Stable upper water column during summer Melting sea ice No vertical mixing Perfect for phytoplankton bloom! Mid-latitudes: Nutrients brought to surface during winter overturn Spring bloom - solar radiation increases Grazing lowers productivity in late spring Second bloom Separate species of phytoplankton Lower nutrient level due to previous bloom, so this one is not so productive. 6
Tropics: Small summer bloom Why is productivity so low in the tropics? Nutrients are limited! No vertical mixing during change of seasons Thus, nutrients are not cycled to photic zone. Combining Solar radiation and nutrient availability (mid-latitude): Nutrients are high in winter b/c of vertical mixing, and low in summer due to consumption by producers Notice biomass lags behind nutrients - b/c of required solar radiation animation 7
Compare productivity in the oceans Upwelling zones (high latitude and coastal): Greatest Primary Productivity Lowest total Primary Productivity - short season Concentrated in space and time (upwelling & Coastal) Good eatin Yum Yum Open oceans: Lowest Primary Productivity Greatest total Primary Productivity - vast size Diffuse or low concentration - not good eatin Compare marine productivity to terrestrial productivity Upwelling zones and Estuaries approach productivity of the most productive cultivated Land! Their productivity is similar to rain forests! Estuaries and upwelling zones are DENSE with life! 8
Nutrients and Dead Zones or Harmful Algal Blooms (HAB) Over abundance of Nutrients (P & N) causes HAB Lots of P and N cause phytoplankton to Bloom in excess They die & sink, consumed by bacteria Bacteria consume ALL O 2 during respiration, creating anaerobic conditions at depth (hypoxia) This lack of O 2 Kills aerobic organisms E.g. Neuse, Tar, Roanoke, Chowan Rivers: 1999 Hurricane Floyd Nasty little algae on East Coast Pfiesteria piscicida - dinoflagellate Recently discovered at NC- State after HAB caused massive fish kills in Neuse, River, Pamlico Sound, Chesapeake Bay. Can cause serious illness in Humans if breathed. Toxic Zoospore causes lesions on fish, consume the oozing goo. Kills fish Amoeboid Stage Gorges on dead fish Cist stage - dormant Flagellate stage - eat algae saves chloroplast from algae and uses them for a few weeks swims to find a new fish host. 9
HAB / Dead Zones (continued) Fertilizers (N & P) from mid-continent flow down the river and out into Gulf of Mexico (see the sediment plume) During summer, the Dead Zone (hypoxia region) increases Annual Dead zone! This also occurs at the deltas of many rivers world wide. Mississippi river system drains mid-continent and carries tons of fertilizer to the gulf coast. Causing an annual HAB and dead zone Since 1993, the average extent of mid-summer bottom-water hypoxia in the northern Gulf of Mexico has been approximately 16,000 square kilometers Approximately twice the average size measured between 1985 and 1992. The hypoxic zone attained a maximum measured extent in 2002, when it was about 22,000 square kilometers larger than the size of the state of Massachusetts. HAB in Gulf 10
Pisco Chile:Algal Bloom and Fish Kill, 2004 Industrial fishing Fish meal (1 ton per 5 tons of anchovy) Shellfish farming Effluent from the fish meal factories serves as nutrients for algae. April 2-4, 2004 anchovy landings were ~10-11 ktons per day (or ~8 ktons of effluent per day) Sediment plumes Effluent caused major phytoplankton bloom and fish kill along the coast. Authorities closed the port for 22 days costing local industry ~27.5 million Pisco Marine food webs begin here: This is basically a map of phytoplankton Phytoplankton Photosynthetic - convert inorganic molecules to organic molecules base of the marine food web (supply nutrients to all other ogranisms!) 11
First link in all marine chains: Zooplankton Zooplankton are herbivore plankton Most numerous and massive population of herbivores on Earth Zooplankton are the primary consumers Convert all plant life to animal tissue Feed all Carnivores (directly or indirectly) Zooplankton 12
Food Web Example: Herring Web = complex interconnected chains Webs = pathways of nutrients & energy Notice: Organisms feed at various levels Organisms occupy various levels during life cycle Disruption of one level, effects all other levels because it disrupts the transfer of nutrients to higher tropic levels! Trophic Pyramids Input nutrients & solar E at base (phytoplankton) Nutrients out at each level Bacteria cycle nutrients back to base! Trophic levels: numbers & mass decrease, size of organism increases Energy transfer between trophic levles: 10% (90% loss to metabolism, life, decay) To produce 10 kg of salmon requires 100 kg fish to feed salmon, 1000 kg zooplankton to feed the fish, 10000 kg phytoplankton to feed the zooplankton 13
Re-visit Antarctic food web Humans hunted baleen whales to near extinction. This disrupted Energy transfer to killer whales What was the result? Over harvesting of lower levels! lots of mass required to replace the energy transfer lost by declining whale numbers Disrupted food web & nutrient cycling? Chemosynthetic communities: Depart from norm (above) At the base of this chain are the chemosynthetic bacteria Use Sulfur-compounds (or methane) to make organic molecules from CO 2 and O 2 Live in water & in crust! (extremophiles) 14
Extremophiles: organisms living in extreme conditions Some bacteria live at >500ºC In hydrothermal vents, hotsprings, in the crust near eruptions Some bacteria live at <12ºC Cold water, Ice, sediment Life under Europa s Ice sheets? In 2005 an entirely new ecological community was discovered beneath the Larsen Ice Shelf off the coast of Antarctica. Mats of chemosynthetic algae feeding on cold seeps supported communities of filter feeders that fed on algae. Higher trophic levels in vent communities Some organisms (shrimp) feed directly on bacteria Others on bacteria bi-products (symbiosis) Tube worms have bacteria in their gut So do clams and mussels 15
Then some open ocean predators feed on these or others - linking food webs Higher trophic levels 16