Biota of Tropical Aquatic Environments

1. Biota of Tropical Aquatic Environments An Overview

2. Taxonomic Classification • Prokaryotes - Bacteria - Archaea • Eukaryotes - Protista - Fungi - Plantae - Animalia

3. Functional Classification Energy Source • Phototrophs • Chemotrophs Carbon Source • Autotrophs • Heterotrophs

4. Top Carnivores 1st Carnivores Herbivores Producers Decomposers Ecological Classification

5. 9,500 cal 10,000 cal 500 cal 150 cal Producer Efficiency • Gross 1o Production (GPP) • GPP/Solar flux • 0.5 – 4.0 % efficiency. • Net 1o Production (NPP) • GPP - Respiration • NPP/GPP • 30 - 80 % efficiency.

6. Consumer Efficiency 50 cal Heat 10 cal Growth/ Reproduction 100 cal 40 cal Waste 100 cal Not Eaten 200 cal

7. Nekton Benthic invertebrates Zooplankton Phytoplankton Classification According to Life Form

8. Plankton • Small organisms suspended in the water column, with no or limited powers of locomotion. Plankton ranges in size from < 2 µm (picoplankton), 2-20 µm (ultra or nanoplankton), to >20 µm (microplankton). • Phytoplankton refers to small plant plankton. • Zooplankton refers to small animal plankton.

9. Periphyton • Community of algae growing attached to substrates (rock, plant, animal, sand). • The entire community of microscopic organisms (bacteria, algae, protozoa, small metazoa) is referred to as biofilm (‘aufwuchs’)

10. Benthic Invertebrates • Non-planktonic animals associated with substrate at the sediment-water. • Epibenthos live and move about on the lake bottom. • Infauna are organisms that burrow beneath the mud surface.

11. Nekton • Actively swimming organisms

12. Neuston (‘Pleuston’) • Organisms (plant or animal) resting or swimming on the surface.

13. Osborne 2000

14. Prokaryotes • Archaebacteria (archaea) • Eubacteria (bacteria) • Density • 1,000,000,000 / g sediment (less in water) • Diversity: ca. 5,000 species known (millions may exist) • Surface area : volume ratio high

16. Numbers, biomass and productivity of bacterio- plankton generally increase with increasing trophic state and temperature. Tropical aquatic systems • High bacterial density (+ 109/L vs. + 108/L in temperate systems) • High bacterial activity • Rapid decomposition and re-use of inorganic compounds (4-9 x faster than in the temperate zone)

17. Bacteria • Autotrophs (examples) * Purple sulfur bacteria (anaerobic:CO2 + H2S  CH2O + S) * Green sulfur bacteria (anaerobic: ditto but different light wavelength) * Cyanobacteria (‘blue-green algae’) • Heterotrophs. Decomposition of particulate and dissolved organic matter. Rates of decomposition determined by chemical composition of organic matter, pH, temperature, availability of electron acceptors. • Parasitic. Significant role in the spread of water-borne diseases (cholera, dysentery, salmonella, etc.)

18. Cyanobacteria Bloom Anabaena Microcystis

19. Bacteria • Autotrophs * Purple sulfur bacteria (anaerobic:CO2 + H2S  CH2O + S) * Green sulfur bacteria (anaerobic: ditto but different light wavelength) * Cyanobacteria (‘blue-green algae’) • Heterotrophs. Decomposition of particulate and dissolved organic matter. Rates of decomposition determined by chemical composition of organic matter, pH, temperature, availability of electron acceptors. • Parasitic. Significant role in the spread of water-borne diseases (cholera, dysentery, salmonella, etc.)

20. Surface Area to Volume Ratios r = 1 µm Surface area (s) = 4(pi)r2 s = 12.6 µm2 = 3.0 V = 4.2 µm3 Volume (V) = 4/3(pi)r3 r = 20µm s = 5028 µm2 = 0.15 V = 33520 µm3

21. Turnover Rate Surface Area Volume high high Nutrient Release (per unit body weight) low low small large Body Size Rotifers and protozoans are often “co-blooming” with cyanobacteria in tropical waters Protozoa (1-2 days) Rotifera (3-5 days) Cladocera (7-14 days) Copepoda (3-5 weeks)

22. For a given nutrient status, primary production in the (sub)tropics is higher because • Efficient nutrient cycling • High density/activity of bacterial decomposers • Importance of smaller organisms • Greater stability in solar radiation • Higher temperatures • Lowland tropics

23. Temperate lakes Tropical lakes Fish A B B A Phyto- plankton Phyto- plankton Bacteria Bacteria B A Crustaceans Rotifers and Protozoans Source: Nilssen 1984

24. Importance of grazing high low Body size of grazer small large Systems dominated by bacteria  abundant small grazers Systems dominated by algae (not blue-greens)  abundance of larger grazers algae bacteria

25. Energy Protozoa (Ciliates, Flagellates) Algae Zooplankton Fish Particulate organic matter Nutrients Soluble organic matter ‘Microbial loop’ Role of Heterotrophic Bacteria in Food Webs Bacterial Decomposition

26. Ciliates, Flagellates (Protozoa) Algae Macrozooplankton Fish DOM, POM Bacteria Protozoa may also consume cyanobacteria Cyano bacteria Consequences: (1) Toxins become concentrated in aquatic invertebrates and passed up the food chain (2) Added steps in food chain decrease food transfer efficiency to higher trophic levels (3) Exceptions to this decrease food transfer efficiency occur when cyanobacteria are directly consumed by higher trophic levels such as some cichlids, birds, humans (largely restricted to tropics).

27. Vibrio cholerae Bacteria • Autotrophs * Purple sulfur bacteria (anaerobic:CO2 + H2S  CH2O + S) * Green sulfur bacteria (anaerobic: ditto but different light wavelength) * Cyanobacteria (‘blue-green algae’) • Heterotrophs. Decomposition of particulate and dissolved organic matter. Rates of decomposition determined by chemical composition of organic matter, pH, temperature, availability of electron acceptors. • Heterotroph Parasitic. Significant role in the spread of water-borne diseases (cholera, dysentery, salmonella, etc.)

28. Tropics and the Transmission ofInfectious Diseases • Cultural factors • Lower standards of hygiene and health care • Lower standard of living (e.g., refrigeration, water supply & wastewater treatment) • Higher incidence of nutritional deficiencies (lower resistance) • Active control of vectors in non-tropical regions (spraying, draining of wetlands, etc.) • Ecological factors • High temperatures, high humidity: Disease vectors (e.g., mosquitos, flies) are more abundant (particularly during the wet season) • Increased exposure to contaminated water and soil (particularly during the wet season) • Vectors survive year round Source: Sattenspiel 2000

29. Bacterial Waterborne Diseases • Clinical Features • Acute dehydrating diarrhea (cholera), prolonged febrile illness with abdominal symptoms and malaise (typhoid fever), acute bloody diarrhea (dysentery), etc. • Common agents • Vibrio cholerae, Campylobacter spp., Salmonella typhi, Shigella spp., and the diarrheogenic Escherichia coli. • Incidence • Each year, an estimated 3 million deaths (mostly among children) result from diarrhea. Waterborne bacterial infections may account for as many as half of these deaths. [More information: Centers for Disease Control, World Health Organization]

30. Bacterial Waterborne Diseases • Sequelae • Many deaths among infants and young children are due to dehydration, malnutrition, or other complications. • Transmission • Contaminated surface water and poorly-functioning water distribution systems contribute to transmission of waterborne bacterial diseases. Chlorination, safe water handling, and water treatment can reduce the risks of transmission. • Trends • Improvements in water and sanitation infrastructure have barely kept pace with population increases and migrations in the developing world. [More information: Centers for Disease Control, World Health Organization]

31. Source: WHO

33. Cases of cholera reported to WHO by continent and by year, 1989-2009 Source: WHO 2010