**7. Phytoplankton communities**

278 Aquaculture

0

20

40

Nitrite (NO2-N) -

60

80

100

120

0

20

40

Nitrate (ppm NO3-N)

60

80


100

120

Days

Days

120

Days

26.5 27 27.5 28 28.5

6 6.5 7 7.5 8

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

> 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

> > 0

20

40

60

80

100

0

20

40

Phosphate (ppm PO4 -P)

60

80

3-

100

0

20

40

(ppm NH3-N)

60

Total Ammonia Nitrogen

80

100

0

20

40

Dissolved Oxygen (ppm O2)

Water temperature (° C)

60

80

100

120

7.5 7.6 7.7 7.8 7.9 8 8.1 8.2

0

20

pH

40

60

Total Alkalinity (ppm CaCO3)

80

100

Days

0 0.001 0.002 0.003 0.004 0.005 0.006

0

20

Silica (ppm SiO2)

40

60

80

100

120

0 0.1 0.2 0.3 0.4 0.5 0.6

0

20

40

60

80

100

120

Days

0

20

40

Calcium (ppm CaCO3)

60

80

100

120

Days

Days

120

Days

120

Days

juveniles in recirculating aquaculture system (Kovitvadhi et al., 2008).

0

20

40

60

80

100

120

Days

Fig. 5. Water quality during culture for 0-120 days of *Hyriopsis* (*Limnoscapha*) *myersiana*

0

20

40

60

Total Hardness (ppm CaCO3)

Free Carbondioxide (ppm CO2)

80

100

120

Days

120

Days

Phytoplankton was found in the gastrointestinal tract, which it was a source of nutrient for several species of freshwater mussel (Hudson and Isom, 1984; Gatenby et al., 1996; Gatenby et al., 1997; ÓBeirn et al., 1998; Kovitvadhi et al., 2000, 2001). This finding is consistent with gut content analyses from other bivalve species (Gale & Lowe, 1971; Huca et al., 1983; Paterson, 1986; Parker et al., 1998). From abovementioned data, it is confirmed that freshwater pearl mussels will filter phytoplankton as the main food. Therefore, culture of freshwater pearl mussels from juvenile to adult, it is necessary to have available phytoplankton species used as food for juvenile and in suitable amount throughout culturing period both in the laboratory and natural resource since freshwater mussel has to filter phytoplankton all the time. Thus, density of phytoplankton used for feeding juvenile or adult is not necessary in surplus but the food must be available throughout the culturing period which will result in increasing survival and growth.
