BIO 366 1st Edition Lecture 7Chapter 2424.8- Rives Flow into the Sea, Forming EstuariesEstuary- place where freshwater join saltwater; semi-enclosed parts of coastal ocean where seawater is diluted and partially mixed with freshwater coming from land; salinity dictates distribution of lifeTwo problems organisms inhabiting estuary have:1. Maintaining their position2. Adjusting to changing salinity24.9- Oceans Exhibit Zonation and StratificationPelagic- whole body of water; pelagic and benthic are two main divisions of the seasNeritic- one province of pelagic; water that overlies the continental shelfOceanic- second province of pelagicEpipelagic Zone or Photic Zone- vertical layer of pelagic from surface to 200m; sharp gradients in illumination, temperature, and salinityMesopelagic Zone- vertical layer of pelagic from 200-1000m; little light penetrates and the temperature gradient is more even and gradualBathypelagic Zone- below the mesopelagic; darknessAbyssopelagic Zone- (Greek meaning “no bottom”); 4000m to sea floorHadalpelagic Zone- deepest zone with areas found in deep-sea trenches and canyonsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.24.10- Pelagic Communities Vary among the Vertical ZonesPelagic ecosystems- lack the supporting structures and framework provided by large, dominant plant life so the sea looks monotonous; bacteria and protists responsible for the largest part of energy flow Dominant autotrophs-phytoplankton; absorb nutrients from water; smaller the organism the greater is the surface-to-volume ratioAutotrophs- restricted to upper surface waters due to light penetrationMajor herbivores- tiny zooplanktonDinoflagellates- a large diverse group with two whiplike flagella; responsible for “red tides” and are in warm watersNanoplankton- make up the largest biomass in temperate and tropical waters; most abundant are the cyanobacteria (tiny)Coccolithophores- most important member of the haptophytes; major source of primary production in the oceans and have an armored appearance due to calcium carbonate plateletsMicrobial loop- feeding loop; bacteria take up dissolved organic matter produced by plankton and nanoplankton; adds several trophic levels to the plankton food chainNekton- feeds on zooplankton; passes energy along higher trophic levels; range in size from small fish to large predatory sharks and whales, seals, and marine birds24.11- Benthos Is a World of Its OwnBenthic- floor of the sea; dark and no photosynthesis takes place; bottom community is heterotrophic; organisms for food chain are bacteria of the sedimentsBenthos- plants and animals that live in the benthicVents- high-temperature, deep-sea hydrothermal, along volcanic ridges in ocean floorPrimary producers of the vents- chemosynthetic bacteria that oxidize reduced sulfur compoundsPrimary consumers of the vents- giant clams, mussels, polychaete worms24.12- Coral Reefs Are Complex Ecosystems Built by Colonies of Coral AnimalsCoral reefs- complex ecosystems; begin with complexity of corals themselvesThree basic types of coral reefs1. Fringing reefs grow seaward from rocky shores of islands and continents2. Barrier reefs parallel shorelines of continents and islands3. Atolls formed when volcanic mountain subsides beneath surface; rings of coral reefs and islands surrounding a lagoon24.13- Productivity of the Oceans Is Governed by Light and NutrientsPrimary productivity- limited to regions where the availability of light and nutrients can support photosynthesisThermocline- limits movement of nutrients from deeper to surface waters where light is adequate to support photosynthesisProductivity controlled by two processes:1. Seasonal breakdown of thermocline and subsequent turnover2. Upwelling of deeper nutrient-rich waters to the surfaceEutrophication- nutrient enrichment; zone of anoxic water in Gulf of Mexico is caused bythisDead Zone- threatens valuable commercial and recreational Gulf fisheries in Gulf of Mexico and is found worldwide; key to minimizing the Gulf dead zone is to address it atthe source; restoration of wetlands and riparian ecosystems can help to capture nutrients and reduce