Biological Productivity and Coastal Habitats

Transcription

1 Biological Productivity and Coastal Habitats Why do we care? Fishing Water quality Wildlife

2 Ecology and Ecosystems Ecology Natural systems Include interactions between living and non-living parts Ecosystem Totality of the environment encompassing all chemical, physical, geological and biological parts Food chain Succession of organisms within an ecosystem base upon trophic dynamics Trophic dynamics Trophic refers to nutrition who is eaten by whom

3 Ecosystems Function by exchange of matter and energy Differ in size, complexity, and diversity of organisms

4 Ecosystem Energy Flow Plants take energy from the sun and put it into the system Use chlorophyll in photosynthesis to convert inorganic material into organic compounds and to store energy for growth and reproduction Plants are autotrophs Plants are primary producers Heterotrophs All other organisms Consumers - animals Decomposers bacteria and fungi Herbivores eat plants Carnivores eat animals Omnivores eat both plants and animals

5 Ecosystem Pathway Material is constantly cycled Energy comes from sun, gradually dissipates as heat and is lost

6 Trophic Dynamics Trophic refers to nutrition Trophic dynamics - study of the nutritional interconnections among organisms within an ecosystem

7 Tropic Level Position of the organism within the tropic dynamics Autotrophs first level Provide the organic matter and energy for all other levels Herbivores - second level Carnivores third and higher levels Decomposers the terminal level

8 Energy Pyramid Graphic representation of a food chain in terms of the energy contained at each trophic level The size of each successive level is controlled by the size of the level immediately below it

9 Primary Producers Phytoplankton in the ocean Require sunlight, nutrients, water and carbon dioxide for photosynthesis The limiting factors is commonly sunlight and/or nutrients Photosynthesis Sunlight + 6CO 2 +6 H 2 O? C 6 H 12 O 6 + 6O 2 C 6 H 12 O 6 is sugar Other organic compounds besides sugar, such as RMA and DNA, are also formed Rapid cell division Phytoplankton blooms rapid expansion of a phytoplankton population because light and nutrients are abundant

10 Doubling Rates Someone will start working for a penny a day, but the rate doubles every day for 30 days. Has to last 30 days. Is that a good deal for the employer or employee?

11 Consumers Animals are the consumers Animals break down the organic compounds into their inorganic components to obtain the stored energy Respiration C 6 H 12 O 6 + 6O 2? 6CO 2 +6 H 2 O + energy The recovered energy is used for movement, reproduction and growth Food consumed by most organisms is proportional to their body size Generally smaller animals eat smaller food and larger animals larger food

12 Feeding Styles Grazers consume plant material copepods, snails, sea urchins, some fish Predators hunt and kill prey sharks, some fish Scavengers consume dead organic matter crabs, lobsters, snails, some fish Filter feeders filter the water for suspended food barnacles, mussels, oysters Deposit feeders selectively or notselectively consume food that is mixed in the sediments

13 What Feeding Style are These Guys?

14 Population Size Dependent upon food supply Lag between the maximum abundance of food and the maximum population size Population goes in cycles

15 Decomposition Bacteria and fungi are the decomposers They break down organic material and release nutrients for recycling NH 3 + 2O 2? H + +NO H 2 O Ammonia and oxygen to nitrate and water Nitrate is used by plants for growth Few bacteria are capable of completely degrading organic material into its inorganic components Most operate in succession with other bacteria to decompose material in a series of stages Bacteria are food for other organisms either directly or indirectly

16 Bacteria Aerobic require free oxygen to respire and decompose dead matter Anaerobic Live in an oxygen free (anoxic) environment Obtain oxygen for respiration from other sources such as SO 4-2 (sulfate ion) and release H 2 S (hydrogen sulfide gas) as a byproduct of decay Hydrogen sulfide rotten egg smell

17 Bacteria Most are heterotrophs Two autotrophic bacteria Cyanobacteria blue-green algae Photosynthesize Chemosynthetic bacteria Use chemical energy released in the oxidation of inorganic compounds to produce food Volcanic vent communities

18 The System

19 Food Chains Transfer the energy from one tropic level to another Biomass is the quantity of living matter per volume of water With each higher trophic level, the size of the organisms generally increase, but their number and total biomass decreases Rate of growth is inversely related to position in the food chain Low on the food chain, the individuals are small but reproduce rapidly High on the food chain, individuals are large but reproduce slowly

20 Two Major Food Chains Grazing food chain Phytoplankton? zooplankton? nekton Herbivores consume autotrophs in the photic zone Detritus food chain Detritus? deposit feeder? nekton Non-living wastes form the base of the food chain Organic matter from the surface waters settles into the deep-sea food chain when it is consumed by detritus feeders

21 Energy Transfer Only about 10-20% of the energy is transferred between trophic levels This produces a rapid decline in biomass at each successive trophic level

22 Efficiency Example of 10% efficiency 100,000,000 g diatoms 10,000,000 g copepods 1,000,000 g small fish 100,000 g large fish 10,000 g human = 10 kg = 22 lb Most (80-90%) of the energy consumed by organisms is lost in movement or in growing non-nutritional structures, such as bone or shell The longer the food chain, the greater the autotrophic biomass needed to support it There must be a balance between the energy expended to obtain food and the energy obtained from the food Not all potential food sources are practical

23 Solar Radiation Only % of the solar radiation is employed for photosynthesis and its energy is stored in organic compound The amount of light decreases rapidly with depth

24 Primary Production Net primary production is the amount of carbon converted into organic material above that required for the minimal survival of the autotrophy The amount of organic material available for growth and reproduction Compensation depth depth where net primary production equals zero Not the CCD Usually located where light intensity is about 1% of the surface value and typically occurs at a depth of~110 m in clear ocean water or 15 m in estuaries

25 Primary Production Most of the light entering the ocean is converted into heat Productivity is small below 0 o C and above 40 o C, but between these productivity increases with temperature Despite decreasing solar radiation, growth and reproduction productivity tends to increase poleward because of greater availability of nutrients away from the equator

26 Nutrients Nutrients are chemicals needed for survival, growth, and reproduction Macronutrients are elements or compounds required in large quantities and include phosphorus (P), nitrogen (N), and silicon (Si) Scarcity of macronutrients usually occurs over a broad region and limits growth on a regional scale Micronutrients are indispensable elements and compounds used in very small quantities Iron, copper, manganese, boron, cobalt trace metals Because they are needed in small amounts, they rarely are scarce over a large region, but may limit growth locally

27 Nutrient Limitations Phytoplankton generally requires phosphorus, nitrogen and carbon in the ratio of 116 C: 16N : 1P Despite the enormous demand for carbon, it is so abundant as bicarbonate ion that it is never a limiting factor N and P are needed in much smaller amounts, but can be limiting factors N harder to recycle than P Decomposition releases N compounds more slowly than P N is usually the limiting factor Silicon can be a limiting factor for diatoms and silicoflagellates

28 Vertical Limitations Dead organisms sink into deep water removing them from the productive surface zone photic zone Upwelling and turbulence can return nutrients to the surface Upwelling regions are highly productive Upwelling occurs Coastal waters Along the equator between the large circulation gyres Near shore turbulence From tides, waves, and storms (waves)

29 Other Limitations Overgrazing of autotrophs can deplete the population and lead to a decrease in productivity Turbidity reduces the depth of light penetration and restricts productivity even when nutrients are abundant

30 Marine Productivity Primary production the total amount of carbon in grams converted into organic material per square meter of sea surface per year If plants abound, so will animals Factors that limit plant growth and reduce primary productivity include: Solar radiation - primary Nutrients- primary Upwelling- primary Turbulence - secondary Grazing intensity - secondary Turbidity - secondary

31 Productivity Variation Productivity varies greatly in different parts of the ocean in response to the availability of nutrients and sunlight Photic zone are the only regions capable of supporting life Deep sea vents are one exception

32 Productivity by latitude regions In tropics and subtropics Light is abundant Nutrients are limiting Strong thermocline restricts upwelling Result = low productivity most places High productivity where upwelling occurs In temperate regions Productivity is seasonal Sunlight is limited seasonally Nutrients also vary seasonally In polar regions Nutrient rich Light poor

33 Temperate Zone Limitations In the winter the water column is isothermal and mixes easily Nutrients are abundant Sunlight restricts productivity In the Spring Sunlight becomes more abundant Diatoms and phytoplankton bloom In the Summer Productivity declines as: Thermocline develops and prevents vertical mixing and resupply of nutrients Usage depletes the available nutrients Grazing by herbivores greatly reduces the population of phytoplankton In the Fall Productivity initially increases as water becomes isothermal and nutrients become abundant Sunlight becomes limiting factor

34 Global Patterns of Productivity Primary productivity varies from 25 to 1250 gm C/m 2 /yr Lowest in the open ocean Low in center like a desert High on edges Continental shelves gm C/m 2 /yr Highest in estuaries, upwelling areas High in polar regions

35 Estimating Productivity Plankton biomass is good indicator of biomass in rest of food web Annual primary production =APP APP = PPR x Area PPR Primary production rate Transfer efficiency = TE Measure of the amount of carbon that is passed between trophic levels Varies from %, generally Potential production = PP PP for each trophic level PP = APP x TE (for each step) Must use TE for each step in the food chain to the trophic level of the organism under consideration

36 Fish Production

37 Productivity Open ocean has greatest biomass productivity Rate of productivity is very low Area is very large Open ocean food chains are longer and energy transfer low, so fish populations are small Most fish production is equally divided between upwelling areas and coastal waters Annual fish production ~ 240 million tons/yr

38 Fishing Annual fish production ~ 240 million tons/yr Fishing million tons/yr million tons/yr Limit should be 110 million tons/yr

39 Productivity in Upwelling Regions Upwelling of nutrient rich water supports large populations of phytoplankton and fish Waters off Peru upwelling and support one of the world s largest fisheries During El Nino, the upwelling stops and the productivity is severely reduced Leads to mass starvation of organisms fish, birds, etc.

40 Global Primary Productivity

41 Global Zooplankton Density

42 Global Benthic Biomass Density

43 Residence Time The average time that a material remains in a system Calculations are only valid if input and output of material from system are known If the system is steady-state, input = output Residence time = material within the system input or output of system