OCEAN: Chapter 13 - Biological Productivity

Microscopic (small) algae

*Diatoms, important producers in the epipelagic open ocean, are members of the Division chrysophyta* *Diatoms are important marine autotrophs that have silica incorporated into their cell walls* *Many of the organisms responsible for toxic red tides and paralytic shellfish poisoning belong to the Division pyrrophyta* *Karenia is responsible for paralytic shellfish poisoning in humans*

Productivity levels

*Freshwater swamp, marsh, algae beds, and coral reefs (comparable to a tropical rainforest) has the highest average net primary productivity.* *Most productive to least: temperature waters, polar waters, tropical waters* Coastal and upwelling areas are productive (Eutrophic), and *open ocean lacks productivity (Oligotrophic)*.

Energy flow

*In an ecosystem, it is unidirectional* *Through a biotic community, it's noncyclic and unidirectional* *1. Producers: organisms within an ecosystem that nourish themselves through either photosynthesis or chemosynthesis* 2. *Consumers/heterotrophic: eat other organisms; Bacteriovores, carnivores, herbivores, and omnivores* 3. *Decomposers: organisms within an ecosystem that break down dead and decaying remains and waste products of organisms for their own energy requirements.* 4. *Autotrophic: algae, plants, archaea, and photosynthetic bacteria*

Nutrient flow

*In an ecosystem, it's cyclical* *Through a biotic community, it's cyclic and multidirectional*

Productivity in temperate oceans

*In middle latitude (temperate) oceans, primary productivity is limited by both available sunlight (fall) and nutrient supply (spring)* *In temperate oceans of the northern hemisphere during the winter months, nutrient concentrations are high, solar input is low, and water temperatures decrease* *In temperate oceans of the northern hemisphere during the summer months, nutrient concentrations are low, solar input is high, and dissolved oxygen decreases* - Winter low (lots of nutrients, little sunlight due to low angle of incidence, deep mixing) - Spring high (spring bloom, more light, less mixing) - Summer low (lots of sunlight, little nutrients due to stratification) - Fall high (fall bloom, more mixing + nutrients)

Primary productivity

*Rate at which energy is stored by organisms through the formation of organic matter* *There is a net gain in organic carbon by organisms* *Measurement: Satellites that measure color.* Factors affecting it: 1. Nutrients 2. Solar radiation 3. COs (rare) 4. Temperature (controlling cellular growth)

Marine fisheries

*The mass of a population of fish present at a given time is called its standing stock* Commercial fishing; Most from continental shelves; Over 20% from areas of upwelling that make up 0.1% of ocean surface area.

Overfishing

*The maximum sustainable yield (MSY) is best defined as largest catch that can be taken without overfishing* *Catches above the maximum sustainable yield result in overfishing* *The term bycatch or incidental catch refers to non-target species that are caught along with commercial species* ---------------------------- The recent abundance of the Maine Lobster in the North Atlantic Ocean is due to the overfishing of cod; The Canadian government declared Cods fishing completely off-limits to fishing in 2003. The overfishing of sharks caused the closure of North Carolina's century-old bay scallop fishery in 2004. Dolphins often wind up as bycatch because fishers commonly used them to locate tuna. Modification of purse seine nets have reduced dolphin mortality as baycatch. The collapse of Atlantic cod stocks resulted in fishers seeking the deep-water Greenland Halibut, which is now in danger of becoming overfished throughout the Atlantic. Orange roughy was originally called the slimehead and is now on the Seafood Watch List of fish to avoid purchasing. Chilean seabags was originally called the toothfish and is now on the Seafood Watch List of fish to avoid purchasing. If you are concerned about purchasing fish from health thriving fisheries, which of the following should you avoid: - bluefin - tuna: canned - tilapia (asia farmed) - cod: atlantic (Canada and United States) - crab: king (imported) - mahi mahi (imported longline) - orange roughy - alaska wild salmon (mercury)

Macroscopic (large) algae

*The most abundant marine macroscopic algae are members of the Division rhodophyta* *Red algae is the most abundant and widespread* *Brown algae is responsible for the name of the Sargasso Sea* *Dead Man's Fingers is green algae*

Photosynthetic marine organisms

1. Anthophyta = *seed-bearing plants (Ulva)* 2. Macroscopic (large) algae = seaweeds 3. Microscopic (small) algae = *phytoplankton (needs sodium)* 4. Photosynthetic bacteria = cyanobacteria and photoheterotrophs

Feeding strategies

1. Suspension/filter feeding: Take in seawater and filter out usable organic matter. - *Barnacles, Baleen whales, sharks, and clams are an example of a heterotroph that feeds by filter* 2. Deposit feeding: Take in detritus and sediment and extract usable organic matter. - Arenicola and Orchestoidea, is an example of a heterotroph that feeds by deposit. 3. Carnivorous feeding: Organisms capture and eat other animals *Individual members of a feeding population in a food chain are generally larger in size and less numerous than their prey*

Productivity in tropical oceans

Availability of sunlight and low rate of primary productivity. *In low latitude (tropical) oceans, primary productivity is limited by nutrient supply only* *Although primary productivity in tropical areas is generally low, equatorial downwelling zones have unusually high primary productivity rates.*

Ocean Eutrophication and Dead Zones

Dead zones: hypoxic (oxygen-poor) water; mouths of major rivers and spring runoffs. *Overproduction of organic matter resulting in anoxic conditions is attributed to Eutrophication* *The number of dead zones has doubled (more than 500)*

Nutrients

Factors affecting primary productivity; *Nitrogen and phosphorus limit photosynthesis in marine environments.* *When nutrients are not limiting productivity, the ratio of carbon to nitrogen to phosphorus in the tissues of algae is in the proportion of 106:16:01* *The concentration of iron nutrients limits productivity in the waters near Antarctica and the Galapagos Islands*

Solar radiation

Factors affecting primary productivity; *The process by which energy is derived from solar radiation that is used by certain organisms to form organic matter is called photosynthesis* *When compared to coastal regions, solar energy extends deep into the water column and concentrations of nutrients are lower in the open ocean.* *When compared to the open ocean, solar energy extends less into the water column and concentrations of nutrients are greater in coastal regions.* *In the clearest ocean water, solar energy may be detected to depths of one kilometer* *The depth at which the cellular respiration rate equals the photosynthetic rate is referred to as the compensation depth for photosynthesis.*

Light transmission

In the ocean, it is limited by 1. Sun's angle of incidence 2. Turbidity from runoff 3. Organisms in suspension Blue wavelengths penetrate deepest, and longer wavelengths (red, orange) absorbed first. *Cosmic rays are high energy charged particles, originating in outer space* *Sensors in the human eye are most efficient at detecting visible light* *X-rays is used to create images of the internal composition of something because it is able to pass through many materials opaque to light*

Productivity in polar oceans

Nutrient-rich all year (upwelling) of North Atlantic Deep Water. Productivity is only high in the summer when light is abundant. *Limited by available sunlight only.* Phytoplankton (diatoms) bloom Zooplankton (mainly small crustaceans) productivity follows; ex. *Blue whales time their migration through middle latitude and polar oceans to coincide with maximum zooplankton productivity; feeds closest to the primary producing population*