Impacts of Human Activities on Aquatic Ecosystems Exploitation Degradation Enhancement Resource Protection
Impacts of Human Activities on Aquatic Ecosystems Urban and agricultural water supplies Waste-water discharge Eutrophication Accidental releases Exploitation Harvesting food and natural products Degradation Biomass removal Energy and mineral supplies Ocean dumping and disposal Airborne contaminants Water Regulation Pathogens and marine toxins
Impacts of Human Activities on Aquatic Ecosystems Monitoring change Reservoirs Artificial reefs Enhancement Lake fertilization Resource Protection Lake restoration Aquaculture National regulations, international agencies and global agreements
Freshwater Ecosystems Invasive Species (e.g., zebra mussel, lamprey) Pollution Habitat Modification Channelization Dams Draining wetlands Changes in terrestrial landscape
Channelization Channelization the dredging and straightening of stream channels Why? Divert water for irrigation Drain fields for agriculture Increase usable land Prevent flooding 1961 Kissimmee River, FL Present
Problems with Channelization Altered flow regimes Many species not adapted to different flows Loss of habitat Within the stream Dredging removes snags, habitat complexity Total stream area Floodplains low- and no-flow in remnant channels & encroaching exotics led to low O 2 & fish kills
Dams and stream modifications Long history of modifying rivers Egypt had irrigation ditches by 3200 B.C. and dams by 2760 B.C. Dams built per year steadily increased from around 1800 to a peak in the 1970 s.
Dams and stream modifications 75,000 dams over 2m tall, plus 2.5 million smaller dams in the U.S. alone
Effects of Dams Benefits: Water supplies Navigation Hydropower Flood Control Decreased frequency, but increased severity
Physical Effects of Dams Alterations of flow Prevents movement of sediment, nutrients downstream Slower flows upstream leads to settling of sediment reservoirs can fill by as much as 80% in 12 years More unpredictable flows downstream Disturbs normal flood-pulse in spring Interchange of nutrients between river and floodplains
Biological Effects of Dams Interrupts fish migration (e.g., salmon) Fish ladders can help Still can have 10-20% fish loss during outmigration
Biological Effects of Dams Loss of important spawning/foraging habitat in floodplain Net economic loss - river fisheries more productive than reservoir fisheries Changes in plant communities, reduced species richness below dams
Human Health Effects of Dams Aswan Dam, Egypt completed in 1970 Schistosomiasis (Bilharzia ) Parasite passes from humans to snails to humans Irrigation from lake provided more habitat for snails
Wetlands Wetlands Transitional habitats between aquatic and terrestrial environments, where water table is at or near the surface Includes marshes, swamps, bogs, estuaries, temporary ponds, etc. Estimated loss of 53% of total wetlands in U.S. 9.2 million acres lost between 1950 s-1970 s 2.6 million acres lost between 1970 2-1980 s current loss of 124,000 acres per year
Wetland Loss Wetlands provide important ecosystem services 1. Mitigate flooding 2. Retention of sediments, nutrients, pollutants Natural sewage treatment plants 3. Wildlife habitat 20% of threatened and endangered species associated with wetlands Important habitat for waterfowl
Wetlands: restoration No-net loss of wetlands rule ~1989 Developers must recreate wetlands they destroy in construction Are new wetlands really the same?
Human Impacts on Marine Systems Many threats to words oceans We will focus on: Overfishing Aquaculture Coral reefs
Oceanic Fisheries Worldwide, 25% of animal protein 70% of world s marine fisheries are overexploited or in danger of becoming overexploited
Oceanic Fisheries Number of fish caught rose steadily until 1990 s, but per capita number caught decreased Human population growing faster than increase in catch Leads to increased demand and overfishing many species commercially extinct - no longer economically profitable to harvest
Sustainable harvest Ideal strategy: harvest population to maximize growth rate determines how quickly fish can be removed, while still maintaining healthy stock too little or too much harvest, population grows slowly keep population at half carrying capacity Most fisheries harvest too much
Why overfish? Economics - Tragedy of the Commons Each group tries to maximize individual returns at expense of common resource Quota problems Often a fixed number, not percentage Harvesting constant number of decreasing population leads to severe impacts
Why overfish? Technological Improvements e.g., Bottom trawlers vs. hook and line problem of bycatch - killing non-target animals
Overfishing Example: Bluefin Tuna Large, wide ranging, fast animal Grows to 1500 lbs. Swims up to 50 mph Can migrate across oceans One of most valuable and overexploited fish Single fish sold for $172,000 in Tokyo fish market auction - sashimi Adult population declined 90% since 1975 250,000 to about 22,000
Overfishing: Bluefin Tuna
Is Aquaculture the answer? Aquaculture - breeding and raising of fish and shellfish for food Rapidly increasing industry Provides 1/4 world s marine fisheries
Aquaculture Arguments for aquaculture 1. Not depleting natural fish stocks 2. No bycatch 3. More efficient Problems 1. Still depleting natural fish populations Feeds often include fishmeal from wild populations 2-5 kg wild fish to produce 1 kg raised fish especially problematic for carnivores fish (e.g. salmon)
Aquaculture Problems (cont.) 2. Fish wastes aquatic pollution, disease spread 3. Genetic diversity raised fish escape and breed with wild fish reduces genetic diversity can cause migration problems 4. Can still be bycatch if wild fish used to stock pens/ponds Milkfish in Philippines 85% of fry collected NOT milkfish
Problems (cont.) Aquaculture 5. Habitat destruction - loss of mangroves, coastal wetlands habitats provide nursery habitat for fish/shellfish protect coast from storms help control floods trap sediments filter and clean water of excess nutrients Solutions? Reduce fishmeal in feeds, raise more herbivorous fish (e.g. Tilapia), regulations on building new facilities
Coral Reefs One of most diverse and productive ecosystems Support at least 1/3 marine fish Protect coasts from storms Uptake carbon
Threats to Coral Reefs Most threatened marine habitat Major problems include: 1. Trawling and dynamite fishing - breaks up reefs
Threats to Coral Reefs 2. Bleaching - death/loss of algae Triggered by stress elevated temperatures pollutants Frequency and severity have increased in the last decade
Threats to Coral Reefs Problems (cont.) 3. Runoff sediments, pollutants 4. Aquarium industry collect best coral, animals 5. Global warming rising sea levels - corals need shallow water rising temperatures corals exist in very narrow temperature range Solutions - creating marine reserves, control development, regulate collecting
Why should I care about coral reefs? Tourism Countries w/reefs get about 50% of their GNP from reef activities Beach protection from waves Medical uses AZT, 50% of cancer research, bone-grafting Biodiversity 1% of ocean floor houses 25% of marine species
Points to know 1) What is channelization? Why is it done and what problems can it cause? 2) What can be the problems with dams and flood control? How do they affect sediment & water flows, fish migration, and floodplains? 3) What is a wetland and how much has been lost in the U.S.? What ecosystem services do they provide? 4) Why is oceanic fishing important (2 reasons)? Name 3 reasons for overfishing. What does the bluefin tuna example tell us about the effects politics & conflict of interests on fishing policies? 5) What are the pros and cons of aquaculture? 6) Why should you care about the destruction of coral reefs?
EVALUATION FORM Instructor/Course Survey Form Faculty Course Evaluations are the primary method for evaluating teaching performance and allows students to make significant contribution to the evaluation of an instructor's performance. The Evaluation is one method of exposing good and bad qualities of courses and instructors. Please take a few minutes to fill out and submit the Evaluation. Your comments are anonymous. Course: ENVS 415 Title of the Course: Aquatic Ecology Instructor: Dr. Subodh Sharma Semester: Fourth Year First Semester
Very week Week OK Very good Excellent 1. Generally, the course was: 2. The content of the course was: 3. The teachers effort to make the course more interesting was: 4. The teacher s efficiency in teaching the material was: 5. The organizations of the course was: 6. The clearness of the teacher was: 7. The explanations of the teacher were: 8. The teacher s ability to present alternative explanations when needed was: 9. The examples and illustrations used by the teacher were: 10. The quality of the questions and problems raised by the teacher were: 11. The student s knowledge on the subject matter was:
12. The teachers enthusiasm was: 13. The answers to the students questions were: 14. The willingness to offer supplementary aid to the students, when needed, was: 15. The use of the time during the class was: 16. The interest of the teacher for the students question was: 17. The quantity of information you acknowledged during the course: 18. The relevance and the utility of the course were: 19. The evaluation techniques and grades (papers, tests, projects, field trips) were: Very low Low Medium High Very high 20. Comparing to other courses you attended, you expect that your grade is going to be: 21. Comparing to other courses you attended intellectual challenge offered by the course was:
I wish you a bright future Thank you for listening to my lectures Your Course Director