5. THE RESPONSE OF FRESHWATER MICRO-ALGAE TO INORGANIC SALTS
5.3 RESULTS
5.3.3 Species sensitivity distributions
91
Na2SO4, while P. subcapitata and C. sorokiniana showed the lowest NOEC to NaCl. These NOEC results were in agreement with the EC50 results shown on Figure 5.1, where Na2SO4
had the lowest EC50 to P. subcapitata and the other three species showed slightly higher EC50 values that were not too different from each other. Similarly for NaCl (Figure 5.1) the EC50 values to P. subcapitata and C. sorokiniana are low and close to each other, while the other two species showed slightly higher EC50 values which also seemed closer to each other.
92
Table 5.3 A summary of single species toxicity data of NaCl to freshwater micro-algae and macro-invertebrates obtained from the ECOTOX and UCEWQ databases as well as this study, and used to generate a species distribution (SSD) curve.
Species Scientific Name
Geometric
mean (g/L) Taxonomic group
Exposure durations (hours)
Number of data points
Pseudokirchneriella subcapitata 0.5 Algae 96 2
Chlorella protothecoides 1.7 Algae 96 3
Chlorella sorokiniana 0.2 Algae 96 2
Chlorella vulgaris 1.3 Algae 96 3
Lithobates sylvaticus 3.7 Macro-invertebrate 96 2
Ceriodaphnia dubia 1.8 Macro-invertebrate 24-96 8
Daphnia ambigua 2.0 Macro-invertebrate 48 1
Daphnia magna 3.3 Macro-invertebrate 24-96 16
Gammarus
pseudolimnaeus 7.7 Macro-invertebrate 96 1
Hyalella azteca 5.0 Macro-invertebrate 96 1
Lirceus fontinalis 3.0 Macro-invertebrate 96 1
Pseudo sidaramosa 1.4 Macro-invertebrate 48 20
Streptocephalus rubricaudatus 3.1 Macro-invertebrate 24 1
Baetis tricaudatus 6.1 Macro-invertebrate 24-48 7
Acroneuria abnormis 10.0 Macro-invertebrate 96 1
Agnetina capitata 10.0 Macro-invertebrate 96 1
Callibaeti sfluctuans 5.0 Macro-invertebrate 96 1
Chaoborus americanus 5.0 Macro-invertebrate 96 1
Pycnopsyche guttifer 3.5 Macro-invertebrate 96 1
Pycnopsyche lepida 3.5 Macro-invertebrate 96 1
Tipula abdominalis 10.0 Macro-invertebrate 96 1
Elliptio complanata 2.4 Macro-invertebrate 24-48 2
Lampsili fasciola 2.3 Macro-invertebrate 24-96 3
Lampsilis siliquoidea 1.1 Macro-invertebrate 24-96 3
Villosa constricta 2.7 Macro-invertebrate 24-48 2
Villos adelumbis 4.0 Macro-invertebrate 24-48 3
Physagyrina 2.5 Macro-invertebrate 96 1
Physella integra 5.0 Macro-invertebrate 96 1
Tubifex tubifex 1.0 Macro-invertebrate 24-96 3
Caenorhabditis elegans 21.3 Macro-invertebrate 24-48 9
Tricorythu stinctus 1.7 Macro-invertebrate 96 1
Euthraulus elegans 7.6 Macro-invertebrate 96 1
Afronurus peringueyi 6.7 Macro-invertebrate 96 1
Caridina nilotica 5.9 Macro-invertebrate 48-96 5
Daphnia pulex 2.8 Macro-invertebrate 24-48 18
Burnupia stenochorias 3.9 Macro-invertebrate 96 1
Flatworm sp. 5.6 Macro-invertebrate 96 1
Plea pullula 7.6 Macro-invertebrate 96 1
Coenagrionidea sp. 22.5 Macro-invertebrate 96 3
Oligoneuridae lawrencei 4.8 Macro-invertebrate 96 1
Leptocerid sp. 6.2 Macro-invertebrate 96 2
Athericidae sp. 18.6 Macro-invertebrate 96 1
Caenidae sp. 3.6 Macro-invertebrate 96 1
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Table 5.4 A summary of single species toxicity data of Na2SO4 on freshwater micro-algae and macro-invertebrates obtained from the ECOTOX and UCEWQ databases as well as this study, and used to generate a species distribution (SSD) curve.
Species Scientific Name
Geometric
mean (g/L) Taxonomic group
Exposure duration (hours)
No. of data points Pseudokirchneriella
subcapitata 0.7 Algae 72-96 6
Chlorella
protothecoides 1.4 Algae 96 5
Chlorella sorokiniana 2.3 Algae 96 2
Chlorella vulgaris 2.2 Algae 96 3
Ceriodaphnia dubia 2.5 macro-invertebrate 48-72 63
Daphnia magna 1.6 macro-invertebrate 24-48 16
Hyalella azteca 2.0 macro-invertebrate 96 48
Chironomus tentans 14.1 macro-invertebrate 48 1
Tricorythus sp. 0.7 macro-invertebrate 96 1
Lampsilissi liquoidea 2.8 macro-invertebrate 48-96 10
Sphaerium simile 2.4 macro-invertebrate 96 7
Tricorythus tinctus 2.8 macro-invertebrate 96 1
Adenophlebia
auriculata 7.2 macro-invertebrate 96 7
Afroptilumsud
africanum 3.4 macro-invertebrate 96 4
Tricorythus discolor 2.7 macro-invertebrate 96 3
Euthraulus elegans 10.2 macro-invertebrate 96 1
Caridina nilotica 5.0 macro-invertebrate 48-96 6
Daphnia pulex 2.0 macro-invertebrate 48 8
Burnupia stenochorias 5.3 macro-invertebrate 96 1
Baetis harrisoni 2.9 macro-invertebrate 96 1
Afronurus barnardi 6.0 macro-invertebrate 96 1
Flatworm sp. 6.5 macro-invertebrate 96 2
Cloeon virgiliae 4.2 macro-invertebrate 96 3
Plea pullula 11.6 macro-invertebrate 96 2
Coenagrionidae sp. 27.0 macro-invertebrate 96 3
Oligoneuridae
lawrencei 0.3 macro-invertebrate 96 2
Leptocerid sp. 8.8 macro-invertebrate 96 3
Belostomatidae sp. 6.9 macro-invertebrate 96 1
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Figure 5.4 The species sensitivity distribution (SSD) curve of micro-algae and macro- invertebrates based on the geometric means of EC50 values of 24-96 hour toxicity test data for NaCl obtained from the ECOTOX and UCEWQ databases, and this study.
Chlorella vulgaris Daphnia magna
Pseudosida ramosa Tricorythus tinctus
Chlorella protothecoides
Ceriodaphnia dubia Daphnia ambigua
Lampsilis fasciola Elliptio complanata
Physa gyrina Villosa constricta
Daphnia pulex Lirceus fontinalis
Streptocephalus rubricaudatus
Pycnopsyche lepida Pycnopsyche guttifer
Caenidae sp.
Lithobates sylvaticus Burnupia stenochorias Villosa delumbis
Oligoneuridae lawrencei Physella integra Hyalella azteca Chaoborus americanus
Callibaetis fluctuans Flatworm sp.
Caridina nilotica Baetis tricaudatus Leptocerid sp.
Afronurus peringueyi Euthraulus elegans Plea pullula
Gammarus pseudolimnaeus
Tipula abdominalis Agnetina capitata
Acroneuria abnormis Athericidae sp.
Caenorhabditis elegans
Chlorella sorokiniana
Pseudokirchneriella subcapitata
Tubifex tubifex Lampsilis siliquoidea
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0.10 1.00 10.00 100.00
Proportion of species affected
NaCl Median effect concentration (g/L)
Central Tendency
95% Prediction Interval
95
The higher number of toxicity data points for the NaCl than Na2SO4 on the ECOTOX re- iterates that there has generally been more work done on the effects of NaCl on organisms than Na2SO4 (Soucek 2007). Ceriodaphnia dubia had the highest number of data points (63), followed by Hyalella azteca (48), and then Daphnia magna (16). Pseudokidokirchneriella subcapitata and Chlorella protothecoides appeared to be more tolerant to Na2SO4 than two of the macro-invertebrates (Tricorythus sp. and Oligoneuridae lawrencei) (Figure 5.5).
Figure 5.5 The species sensitivity distribution (SSD) curve of micro-algae and macro- invertebrates based on 24-96 hour toxicity test data for Na2SO4 obtained from the ECOTOX and UCEWQ databases, and this study.
Daphnia magna Daphnia pulex Hyalella azteca
Chlorella vulgaris Chlorella sorokiniana
Sphaerium simile Ceriodaphnia dubia
Tricorythus discolor Tricorythus tinctus Lampsilis siliquoidea
Baetis harrisoni Afroptilum sudafricanum
Cloeon virgiliae Caridina nilotica
Burnupia stenochorias Afronurus barnardi
Flatworm sp.
Belostomatidae sp.
Adenophlebia auriculata
Leptocerid sp.
Euthraulus elegans Plea pullula
Chironomus tentans Coenagrionidae sp.
Oligoneuridae lawrencei
Tricorythus sp.
Pseudokirchneriella subcapitata
Chlorella protothecoides
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0.10 1.00 10.00 100.00
Proportion of species affected
Na2SO4 Median effect concentration (g/L)
Central Tendency 95% Prediction Interval
96
The two locally isolated algal species, C. sorokiniana and C. vulgaris, appeared to be slightly more tolerant to Na2SO4 than the other two algal species, even more tolerant than five of the macro-invertebrates (Tricorythus sp., Oligoneuridae lawrencei, Daphnia magna, Hyalella Azteca and Daphnia pulex) (Figure 5.5).