Streams and Rivers in South America(with emphasis on algae)

Morgan L. Vis

Neotropical Ecology Seminar

French Guiana

Questions to consider What type of algae usually grow in large rivers like

the Amazon? What are macroalgae? What are the morphological types of macroalgae? Is the diversity of macroalgae in the eastern Atlantic

Rainforest greater or less than in other areas? Why? What is known about the seasonality of macroalgae?

Classification of Streams & Rivers Based on orders 2- 1st order streams meet

to form a 2nd order stream.

2- 2nd order streams meet to form a 3rd order etc.

When a 1st meets a 2nd it stays a 2nd.

Amazon River (largest in terms of drainage area)

The Amazon – a large flood plain river

Animals of the Large Rivers Fish (~2000 species)

Mostly small Feed on zooplankton A few large types used

as food source Piranhas

Invertebrates

Animals of the Large Rivers Alligators Caiman Birds Dolphins/Manatees Otters Turtles Capybara

Large Rivers and Algae Turbid Deep Lack of substrate Phytoplankton

Stream Macroalgae

Usually attached to the bottom and have a discretethallus that can be seen with the naked eye.

Functional Groupings Algae that bend

in the direction of the flow to reduce drag

Algae that avoid flow by living within the boundary layer

Gelatinous Filament

Batrachospermum

Tuft

Audouinella

Free Filament

Cladophora

Mat

Phormidium

Tissue Like

Lemanea

Gelatinous Colony

Nostoc

Crust

Heribauldiella

Rio Preto Large river

system Southeastern

Brazil Flows

through temperate forests and tropic regions

Distribution of stream macroalgae in the eastern Atlantic Rainforest of Sao Paulo State, southeastern Brazil

52 streams sampled 42 macroalgal taxa collected Most abundant

Audouinella pygmaea Compsopogon coeruleus Microcoleus subtorulosus

No correlations for overall macroalgae

Audouinella occurred in higher conductance & current velocity with lower pH

Distribution of stream macroalgae in the eastern Atlantic Rainforest of Sao Paulo State, southeastern Brazil

Lower diversity than found in other studies

Patchy distribution Intermediate disturbance

hypothesis – this region has high disturbance

High precipitation good for terrestrial plant diversity but could be lowering macroalgal diversity.

Seasonality of macroalgae in 3 tropical drainage basins

3 separate but close drainage basins

Monthly sampling for 1 year

Algae & phys/chem measured

Purpose: compare dynamics of macroalgal communities and evaluate most influential variables acting on seasonality

Seasonality of macroalgae in 3 tropical drainage basins - Results

Several factors influence community dynamics Percent cover – oxygen, cross-sectional area, pH, current

velocity, conductance, turbidity & precipitation Richness – oxygen, temperature, turbidity, pH and current

velocity Overall – precipitation & turbidity

Seasonal patterns the same in 3 drainage basins with high percent cover & richness in dry season (June-November?)

Seasonality of macroalgae in 3 tropical drainage basins

Chantransia high Sept-Feb & April –Sept Correlated to current velocity &

conductance Stigeoclonium

Abundant April - Sept Various correlations in different spots

Batrachospermum Low cover Dec-May Various correlation

Phormidium High Dec-April Neg corr oxygen & current velocity

Microhabitat and plant structure of Batrachospermum populations in four stream

7 Batrachospermum populations 4 B. delicatulum 1 B. macrosporum 2 Chantransia

Quadrats sampled during Aug-Sept Purpose – examine microhabitat,

plant structure and the influence of physical variables

Microhabitat and plant structure of Batrachospermum populations in four stream

Microhabitat and plant structure of Batrachospermum populations in four stream

B. delicatulum - 1, 4, 5, 6 B. macrosporum – 2 Much higher

male/female ratio in 2 Different reproductive

strategies

Questions revisited What type of algae usually grow in large rivers like the Amazon?

Phytoplankton – those that can float in the water What are macroalgae?

Algae that are visible with the naked eye What are the morphological types of macroalgae?

Gelatinous filament, free filament, tuft, mat, tissue-like, gelatinous colony, crust

Is the diversity of macroalgae in the eastern Atlantic Rainforest greater or less than in other areas? Why? Less – possibly due to high disturbance

What is known about the seasonality of macroalgae? Most influenced by precip & turbidity; greatest in dry

season

Bibliography http://eebweb.arizona.edu/fish/calhamaz.html#anchor5050752 http://www.netshaman.com/brazil/index.html Giller, P.S. & Malmqvist, B. 1998. The Biology of Streams and Rivers.

Oxford Press. Branco, C.C.Z. & Necchi Jr., O. 1996. Distribution of stream

macroalgae in the eastern Atlantic Rainforest of Sao Paulo State, southeastern Brazil. Hydrobiologia 333: 139-150.

Branco, L.H.Z. & Necchi Jr., O. 1997. Seasonality of macroalgae in three tropical drainage basins in Sao Paulo State, southeastern Brazil. Archiv fur Hydrobiologia 141: 75-91.

Necchi Jr., O. 1997. Microhabitat and plant structure of Batrachospermum (Batrachospermales, Rhodophyta) populations in four streams of Sao Paulo State, southeastern Brazil. Phycological Research 45: 39-45.