BACTERIOPLANKTON: DISTRIBUTION AND ECOLOGY

Role of bacteria in the carbon cycle

Recall

How to determine numbers of cells and biomass

• Direct count• Culture• Fluorescence microscopy• ATP• Identify environmental microbes by PCR, RFLP,

and sequencing

SEM micrograph of bacterioplankton Fluorescence micrograph of bacterioplankton

ASSUMPTIONS

• Growth of bacteria substrate-limited• Thus, bacterioplankton most common in

layers where primary production highest (epilimnion)

• Low biomass in metalimnion• A second maximum in the hypolimnion• Numbers lowest in winter

Thus, bacterioplankton should vary according to season and depth

Co-occurrence of phytoplankton and bacterioplankton

Numbers and relative occurrence of bacterioplankton in a Michigan Lake from October to July

Numbers and production rates of bacterioplankton through the seasons

Lake Hancza, the deepest lake in Poland

Gotkowska-Płachta A. , Niewolak S. , Korzeniewska E. 2003. VERTICAL DISTRIBUTION AND SEASONAL CHANGES IN THE NUMBER OF BACTERIOPLANKTON IN THE WATER OF LAKE HAŃCZA, PARTICULARLY IN THE PERIOD OF RESERVOIR SUMMER STRATIFICATION. EJPAU 6(2), #10.

Figure 2. Vertical changes of temperature, oxygen saturation and number of planktonic bacteria (thousands of cells/ 1 cm3 of water) in the water of Lake Hańcza (at station 1) during summer stratification of the lake in 1997 and 1998. A temperature, B oxygen, C planktonic bacteria

Gotkowska-Płachta A. , Niewolak S. , Korzeniewska E. 2003. VERTICAL DISTRIBUTION AND SEASONAL CHANGES IN THE NUMBER OF BACTERIOPLANKTON IN THE WATER OF LAKE HAŃCZA, PARTICULARLY IN THE PERIOD OF RESERVOIR SUMMER STRATIFICATION. EJPAU 6(2), #10.

Figure 3. Vertical changes of temperature, oxygen saturation and number of planktonic bacteria (thousands of cells/ 1 cm3 of water) in the water of Lake Hańcza (at station 1) during summer stratification of the lake in the years 1999 and 2000. A temperature, B oxygen, C planktonic bacteria

Also controlled by

• Temperature (as you have seen, usually highest in warm months)

• pH (grow best in circumneutral pH)• Often restricted by nutrient availability,

especially phosphate

Model of seasonal control of bacterioplankton

DOC: Amino Acids and Carbohydrates

• Concentrations low• Assimilated faster in aerobic water than in

anaerobic water• Assimilation faster in warmer water than in

cooler water• Humic acids degrade very slowly and may be

linked to other organics

Uptake of DOC

• As cells die, 5-35% released as DOC• Extracellular release of DOC by primary

producers a major source• Most DOC released by primary producers in

the euphotic zone• Bacterial assimilation peaks after peak release

of DOC by phytoplankton

Distribution of carbon fractions versus rates of uptake

The microbial loop

Idealized daily fluctuations of various parameters that impact bacterial uptake

Organic content of suspended particulate matter (POC) through the seasons

Phytoplankton production relative to rates of sedimentation of POC

Rates of turnover by large and small bacterioplankton

Bacteria in Rivers and Lakes, a Study

De Araujo, M.F.F. and M.J.L. Godinho. 2008. Seasonal and spatial distribution of Bacterioplankton in a fluvial-lagunar system of a tropical region: density, biomass, cellular volume and morphologic variation. Brazilian Archives of Biology and Technology. 51(1): doi: 10.1590/S1516-89132008000100024

Summary for bacterioplankton. See Table 17-16 (p. 523)

RIVERS RESERVOIRS LAKES

Bacterioplankton abundance

High to very high Moderate to high Low

Bacterioplankton production

Low but increasing with stream order

Low to moderate Low

Bacterioplankton respiration

High Moderate Low

Bacterioplankton Mortality

High Moderate High