Aquatic Ecology

Factors Affecting Aquatic Ecosystems Light decreases with depth. - Only 1% of light below 200 m - No light below 1000 m Turbidity (cloudiness) affects light. Temperature decreases with depth due to decreasing energy input from sun.li

Euphotic Zone Continental shelf High tide Low tide Sun Depth in meters Coastal Zone Open Sea Sea level Photosynthesis 50 Euphotic Zone Estuarine Zone 100 Continental shelf 200 500 Bathyal Zone Twilight 1,000 1,500 2,000 Water temperature drops rapidly between the euphotic zone and the abyssal zone in an area called the thermocline . Abyssal Zone 3,000 Darkness 4,000 5,000 10,000 5 10 15 20 25 30 Water temperature (°C)

Discuss with your table partner: Study the pattern of oxygen with depth. The red line represents approximately the start of the aphotic (no light) zone. What process accounts for the depletion of oxygen at this depth? Why is the level of oxygen higher closer to the surface (besides diffusion of O2 into the H2O)? Decomposition of organic matter (most of which comes from above) by aerobic organisms depletes the oxygen. Enough light for photosynthesis which adds oxygen.

Discuss with your table partner: Temperature and pressure also affect the levels of dissolved oxygen and other gases. How does temperature affect the amount of dissolved gas? How does pressure affect the amount of dissolved gas? (Consider what happens when you release the pressure on a sealed bottle of soda.) Temperature varies inversely with maximum DO. Pressure varies directly with maximum DO. More dissolved gas at higher pressure.

Factors Affecting Aquatic Ecosystems Nutrient availability most limiting macronutrients are phosphorus (P) & Limiting micronutrients include iron (Fe); essential for growth of phytoplankton. A failed experiment to increase the carbon stored in the ocean by seeding it with iron to stimulate phytoplankton growth did not work because it also caused a bloom of toxic diatoms. http://permaculturenews.org/2012/11/07/ocean-fertilization-promotes-toxic-algae-in-haida-gwaii/

Discuss with your table partner: Study the pattern of nitrate levels with depth. What accounts for the increase in nitrates, which corresponds approximately with the lower levels of oxygen? Decomposition of materials (much of which falls from above) provide available nitrates. Why are lower levels of nitrates not available closer to the surface? Greater rate of uptake of nitrates and other nutrients. Phytoplankton use up much of the nitrates.

Discuss with your table partner: Note that in most locations, the surface has low levels of nitrates. Relate the areas of higher nitrates off the west coast of South America to our weather unit. How do areas of high nitrates along coast of South America relate to weather unit? Location of upwelling that bring nutrient-rich water from deeper ocean .

Life zones of the Ocean Vertical Zones: Euphotic Zone: 0 - 200 m Greatest amount of light. (Eu = good, photo = light) Bathyl Zone: 200 - 4500 m Abyssal Zone: 4500 - 11,000 “marine snow” – dead organisms from above (Abyss= the deep) Hadal Zone: > 6000m

Benthic Zone = Region along bottom of sea Benthos = bottom dwelling sea creature. Pelagic Zone = open sea Region that is not near the shore or close to the bottom.

Marine (salt water) Ecosystems NATURAL CAPITAL Marine (salt water) Ecosystems Marine Ecosystems Ecological Services Economic Services Climate moderation Food CO2 absorption Animal and pet feed Nutrient cycling Pharmaceuticals Waste treatment Harbors and transportation routes Reduced storm impact (mangroves, barrier islands, coastal wetlands) Coastal habitats for humans Recreation Habitats and nursery areas Employment Oil and natural gas Genetic resources and biodiversity Minerals Scientific information Building materials

Estuaries & Coastal Wetlands Estuary: where seawater mixes with freshwater from land, generally at the mouth of a river Coastal wetland: areas of coastal land covered all or part of the year with salt water Brackish= mix of salt water and fresh Importance nutrient rich and high primary productivity nurseries for fish & other aquatic animals waterfowl & shorebird breeding areas filter water pollutants

Estuaries & Coastal Wetlands Human Impacts world has lost over half of its estuaries & coastal wetlands percentage lost in the U.S. even higher. Most lost to coastal development causes of degradation: urban runoff, sewage treatment plant effluent, sediment & chemical runoff from agricultural lands

Barrier Islands Barrier Islands: long, thin, low offshore islands of sand that run parallel to the shore. They do not remain stationary over time. Importance protect mainland from offshore storms shelter inland bays, estuaries, & wetlands

Barrier Islands Human Impacts Development on barrier islands destroys dunes & dune vegetation causes beach erosion (through trying to keep islands in place) destroys or disturbs wildlife habitat (e.g., some endangered birds nest on barrier islands) Protecting barrier islands jetties & seawalls beach replenishment replanting dune vegetation, controlling development Ocean City, MD

Coral Reefs reefs formed by mutualism between polyps & algae reefs built as colonies of polyps secrete limestone; hard deposits remain when the polyps die reefs located in coastal zones of tropical oceans

Coral Reefs Importance high biodiversity: “tropical rain forests of the ocean” protect coastlines from storms & high waves nurseries for many fish species disappearing Human Impacts sediment runoff & effluent increased UV radiation (ozone depletion) fishing with cyanide & dynamite Vulnerability slow growing easily disturbed thrive only in clear water

Mangrove Swamps Salt-tolerant trees & shrubs Warm tropical coastal areas Too silty for coral reefs Protect coastlines from erosion, especially during typhoons & floods Trap nutrient-rich sediments Provide habitat for fish, birds, invertebrates, and plants

Freshwater Ecosystems Lakes Littoral zone: shallow area near the shore, to the depth at which rooted plants stop growing. Limnetic zone: open, sunlit, surface layer away from the shore. Depth is the limit of light penetration. Profundal zone: deep, open water where there is no light penetration. Benthic zone: the bottom of a lake; inhabited by insect larvae, decomposers, & clams.

Sunlight Painted turtle Blue-winged teal Green frog Muskrat Pond snail Littoral zone Plankton Limnetic zone Diving beetle Profundal zone Northern pike Benthic zone Yellow perch Bloodworms

NATURAL CAPITAL Freshwater Systems Ecological Services Economic Services Climate moderation Food Nutrient cycling Drinking water Waste treatment Irrigation water Flood control Hydroelectricity Groundwater recharge Habitats for many species Transportation corridors Genetic resources and biodiversity Recreation Scientific information Employment

Discuss with your table partner: Describe the normal pattern of temperature (and density) with depth in a lake in the summer. How does this pattern result in stratification (layers)? Upper layer is warmer. Since this warmer layer is less dense it remains on the top. epilimnion: warm, upper layer epi= above thermocline: zone where temperature changes rapidly hypolimnion: colder, denser lower layer hypo= below

Discuss with your table partner: In temperate locations, there is often a turnover over water in the Spring and Fall, which can help redistribute nutrients and oxygen. Explain why these overturns occur. spring & fall (temperate zone lakes) When the surface water cools in the Fall it becomes more dense and sinks. In the Spring, as ice melts it becomes more dense and sinks.

Video: Overturn in Temperate Lakes http://www.youtube.com/watch?v=X26ocQkhNH4

Atmosphere vs. Bodies of Water In the atmosphere, there is more heating at the bottom. (Not much blocking of light by the atmosphere). - This heating at the bottom creates convection currents such as the Hadley Cells. In bodies of water, most of the heating is at the surface since light can not penetrate very far into the more dense water. - This often leads to thermal stratification.

Wetlands Wetland functions Human impacts: Lands covered with wildlife habitat, especially for waterfowl & amphibians filter sediments & pollutants from runoff , “nature’s kidneys” flood attenuation Human impacts: some states have lost over 90% of their wetlands by filling or draining.