Ecological Principles and the Chesapeake Bay

1. Ecological Principles and the Chesapeake Bay

2. Objectives • Be familiar with the following ecological principles: • Organisms adapt to their habitat • Pyramid of numbers, biomass, energy • Nutrient cycles • Ecosystem Balance • Ecosystem Stability • Ecosystem Succession

3. Organisms adapt to their habitat • Salinity • Temperature • Light • Oxygen

4. Salinity • Salinity is a measure of how much salt is in the water • measured as parts per thousand • Bay has a salt concentration of 0ppt to 32ppt • influenced by rain tides and coriolas forces

5. Temperature • Seasonal fluctuations • Temperatures range from 32oC to ~85oC

6. Light • Light fluctuates daily, is weather dependant, and is seasonally dependant • Erosion also reduces light penetration

7. Oxygen • Required for most non-plant species • Regions of the Bay have fluctuating O2 levels • Summer is usually the most stressful time • Affected by nutrient runoff

8. Pyramid of numbers, biomass, energy • Reflects a decrease in organisms with each increasing level of the food chain

9. Nutrient cycles • CARBON CYCLE • Carbon is the basic element on which all life relies. Our planet is Carbon dependant. • Usable carbon is present in the environment as CO2. • Carbon dioxide is found in the atmosphere and dissolved in water. • Carbon is transferred up the food chain and returned as waste products

10. Nutrient cycles • NITROGEN CYCLE • Nitrogen is an element used in DNA and other biological elements and is a prevalent gas in our Earth’s atmosphere. Atmospheric nitrogen is not usable by most organisms. • In marine systems, nitrogen is a limitingfactor.

11. Nutrient cycles • Phosphorous cycle • Phosphorous is a molecule that is extremely reactive and used by living organisms to make cell membranes • Phosphate is added to fertilizer and cleaning reagents • Phosphate is a limiting factor in freshwater systems

12. Ecosystem Balance • Organisms influence nutrient cycles • Humans disrupt the carbon cycle through habitat destruction and pollution, primarily combustion byproducts. • We disrupt nitrogen and phosphate balance through over fertilization of fields or poor agricultural practices. Erosion. Household wastes.

13. Ecosystem Balance • Ecosystem have environmental checks and balances that usually allow for the resumption of natural cycles following a brief disruption • Growth factors: cause a flourish of life. Results in an increase in carrying capacity. • Reduction factors: result in the death of organism. Results in a reduction in carrying capacity.

14. Environmental Resistance • Collectively, growth and reduction factors constitute environmental resistance. • Environmental resistance can be further grouped into: • Density independent factors : limit growth of organisms irrespective of number. • Density dependent factors: limit increase or decrease of organisms depending on the density (#/area) of the organism

15. Density Independent Factors • Storms: Hurricanes such as Agnes • River flooding following localized thunder storms • Unseasonable temperature fluctuations • Drought • Pollution: spills or runoff

16. Density Dependent Factors • Competition: interaction of organisms for resources such as food and habitat. • Limiting factors: nutrients, hard substrate • Predation: predators tend to eat the prey organism encountered most often • Toadfish eats fish, crabs, and/or oysters • Parasitism: increased organism numbers makes transmission easier • Menhaden and parasitic Isopods • Disease: spreads more readily in densely populated groups • Fish and fungal infections

17. Ecosystem Stability • The stability of an ecosystem is linked to the species diversity within that ecosystem, i.e. the number of different species in the system.

18. Ecosystem Succession • Succession is a slow ecosystem force which is most easily recognized after a destructive force has devastated an environment. • Primary succession: Establishment of life in a virgin environment e.g. volcanic island or following a glacial retreat. • Slow process because of soil formation and species introduction • Secondary succession: re-establishment of life following a disruptive force. • Quicker process because ingredients for life are in place and previous species are nearby and ready to re-invade.