Keywords: Chlorine; Arabian Gulf; acute toxicity; chronic toxicity; risk assessment; species sensitivity distribution;
Guidelines established by the Qatari Ministry of Environment (MoE) (one of the Arabian Gulf states) for TRO and CBPs in cooling discharge waters specify that the maximum concentration of free TRO is 0.05 mg/L at the discharge point [51]. However, greater than 0.05 mg/L is permitted if a site-specific dispersion model is developed to demonstrate that the chlorine concentration does not exceed 0.01 mg/L at the edge of the mixing zone. This value is in line with the USEPA TRO guideline for marine species [1].
For sea urchins the eggs were collected and counted under the microscope and a suspension of 2000 eggs per ml was made. 1 ml of the egg suspension was transferred to 3 ml well plates. This was followed by an addition of sperm suspension. Simultaneously the toxicant was added to the well plates to check the impact of the toxicant on fertilization. Four replicates per treatment were used. After 8 h incubation at 23 °C in an isothermal chamber, contents in the wells were preserved using formalin for later observations under an inverted microscope. Successful fertilization in sea urchin is indicated by the formation of a fertilization membrane around the egg. The recorded endpoint for pearl oyster was the percentage of normal D-larvae in samples of a minimum of 100 individuals per well. A larva was considered developing normally when the shell was D-shaped (straight hinge) and the mantle did not protrude out of the shell. Fertilization success and normal larvae development in the control, for both species, were always more than 70%.
Taxon |
Species |
Life stage |
Endpoint |
Acceptability criteria |
References |
Phytoplankton |
Synechococus Sp. |
n.a |
Growth inhibition |
Control growth: X 16 per 3 days |
ASTM E1218-04 (2012) |
Chaetoceros Sp. |
n.a |
Growth inhibition |
Control growth: X 16 per 3 days |
OECD Guideline 201(2011) |
|
Crustaceans |
Euterpina acutifrons |
Nauplii Copepodite |
Mortality Mortality |
Mortality in controls < 10% Mortality in controls < 10% |
Rosea A, et al., (2006) |
Microstella Sp. |
Copepodite |
Mortality |
Mortality in controls < 10% |
|
|
Bivalves |
Pinctada radiata |
Embryo |
Embryo development |
Normal larvae in controls > 75% |
ASTM E 724-89, (1989) |
Echinoderm |
Echinometra mathaei |
Embryo |
Fertilization |
Successful fertilization |
EPA, 2009 |
> 75% in controls |
|
|
|||
Fish |
Aphanius dispar |
Embryo |
Hatchability |
Hatchability in controls > 80% |
OECD 235 (2015) |
Juvenile |
Mortality |
Mortality in controls < 10% |
OECD 215, 2013 |
||
Adult |
Mortality |
Mortality in controls < 10% |
OECD 203, 1992 |
In the acute toxicity test, 72-h-EC50 (effective concentration in 50% of the test organisms over 72 h) for microalgae, 48-h-LC50 for copepod, pearl oyster and sea urchins and 96-h-LC50 (lethal concentration in 50% of the test organisms over 96 h) for fish larvae and adults and 10-d- LC50 for fish embryos were used as main endpoints. In the chronic toxicity test, 21-d-EC10 (effective concentration in 10% of the test organisms over 21 days) for copepod and 120-d-EC10 (effective concentration in 10% of the test organisms over 120 days) for oysters and 28-d-EC10 for fish.
Species |
Wet weight |
Stage |
Time |
Chlorine Exposure |
|
(g) |
|
|
concentration (mg/L) |
Synechococcus sp. |
n.a |
n.a |
72h |
0.000, 0.030, 0.060, 0.125, 0.250 |
Chaetoceros sp. |
n.a |
n.a |
72h |
0.000, 0.030, 0.060, 0.125, 0.250 |
Euterpina acutifrons |
|
Nauplii/copepodite |
48h |
0.000, 0.030, 0.060, 0.125, 0.250 |
Nauplii/copepodite |
n.a |
|
|
|
Microstella sp. |
|
larvae |
48h |
0.000, 0.030, 0.060, 0.125, 0.250 |
copepodite |
n.a |
|
|
|
Pinctada radiata Embryo |
|
4hpf |
48h |
0.000, 0.030, 0.060, 0.125, 0.250 |
|
n.a |
|
|
|
Echinometra mathaei |
|
4hpf |
48h |
0.000, 0.030, 0.060, 0.125, 0.250 |
Embryo |
n.a |
|
|
|
|
|
|
|
|
Aphanius dispar Embryo |
n.a |
8hpf |
10d |
0.00, 0.125, 0.25, 0.50, 1.00, 2.000 |
Juvenile |
0.3 ±0.2 |
1-3m |
96h |
0.00, 0.125, 0.25, 0.50, 1.00, 2.000 |
Adult |
1.3 ± 0.1 |
6-8m |
96h |
0.00, 0.25, 0.50, 1.25, 2.5, 5.000 |
*m: month.
*n.a: not applicable
Species |
Wet weight |
Stage |
Time |
Chlorine Exposure |
Copoped |
n.a |
Nauplii |
21d |
|
0.000, 0.025, 0.100 |
||||
Pinctada radiata Adult |
|
|
120d |
0.000, 0.025, 0.100 |
3.64 ±0.3 |
3-5y |
|||
Aphanius dispar Juvenile |
|
|
28d |
0.000, 0.025, 0.100 |
0.3 ±0.2 |
1-3m |
Species |
Exposure |
Dosing |
R2 |
P |
EC50/LC50 |
Synechococcus Sp. Chaetoceros Sp. |
72h |
Semi-static Semi-static |
0.999 |
<0.01 |
0.101(0.101-0.101) |
Euterpina acutifrons
•Copepodite Microstella Sp. Pinctada radiata Echinometra mathaei |
48h |
Semi-static Semi-static Semi-static Semi-static Semi-static |
0.996 |
<0.01 |
0.217(0.195-0.239) |
Aphanius dispar
•Juvenile •Adult |
10 d |
Semi-static Semi-static Semi-static |
0.997 |
<0.02 |
0.454(0.421-0.489) |
Aphanius dispar
•Juvenile |
10d |
Flow-thro Flow-thro |
0.991 |
<0.01 |
0.074(0.061-0.086) |
Species |
Endpoint |
R2 |
P |
LOEC/LC10 |
Euterpina acutifrons |
21d |
0.845 |
<0.01 |
0.02(0.0-0.050) |
Pinctada radiata |
longevity (120d) |
0.791 |
<0.02 |
0.01(0.0-0.069) |
Aphanius dispar |
longevity (28d) |
0.999 |
<0.01 |
0.02 (0.01-0.03) |
Rank |
Saltwater Species |
EC50/LC50 |
Time |
References |
4 |
Leiostomus xanthurus |
0.09 |
96h flow-thro |
Bellanca, M. A., Bailey, D. S. (1977) |
3 |
Oncorhynchus mykiss |
0.14 |
96h static |
Basch, R.E. et al. (1971) |
3 |
Pimephales promelas |
4.8-8 |
96h static |
Curtis, M.W. (1981) |
3 |
Morone saxatilis |
0.04 |
96h flow-thro |
Middaugh, D.P., et.al. (1977) |
3 |
Pandalus goniurus |
0.063-0119 |
96h |
Thatcher, T.O. (1978b) |
3 |
Crangon sp. |
0.118-0.151 |
96h |
Thatcher, T.O. (1978b) |
3 |
Anonyx sp. |
0.118-0.173 |
96h |
Thatcher, T.O. (1978c) |
4 |
Neomysis sp. |
0.15-0.175 |
96h |
Thatcher, T.O. (1978b) |
3 |
Pontogeneia sp. |
0.583-0.864 |
96h |
Thatcher, T.O. (1978b) |
3 |
Shore crab |
1.24 — 1.53 |
96h |
Thatcher, T.O. (1978b) |
2 |
Dunaliella tertiolecta |
0.11 |
24h |
Gentile J.H. et al. (1976) |
2 |
Thalassiosira rotula |
0.20 |
24h |
Gentile J.H. et al. (1976) |
2 |
Thalassiosira guilardii |
0.075 |
24h |
Gentile J.H. et al. (1976) |
Cumulative Probability |
Native GMAVs Log (mg/L) |
Non-native GMAVs Log (mg/L) |
All Taxa |
0.1 |
-1.137 |
-1.397 |
-1.397 |
0.2 |
-1.119 |
-1.041 |
-1.119 |
0.3 |
-0.996 |
-1.041 |
-1.041 |
0.4 |
-0.959 |
-0.957 |
-0.996 |
0.5 |
-0.928 |
-0.869 |
-0.959 |
0.6 |
-0.664 |
-0.854 |
-0.869 |
0.7 |
-0.129 |
-0.836 |
-0.836 |
0.8 |
0.0017 |
-0.472 |
-0.472 |
0.9 |
0.0073 |
0.142 |
0.142 |
Furthermore, [37] reported a 96-hour LC50 value of 0.06 mg/L to rainbow trout (Salma gaidneri), which contrasts with LC50 values of 0.15 mg/L for trout (Salvalinus fontinalis) and 0.032 mg/L for salmon (Oncorhynchus kisutch), reported by [61]. The effects of chlorine to 11 phytoplanktonic algae species were tested by [33] and report the chlorine concentrations causing 50% growth reduction in a series of 24 h static tests; the LC50values ranged from 75 to 330 μg/l. The acute toxicity of chlorine in fish has been the most studied, with the most referenced including (61] [37] [65]. The lowest 96h LC50 value was determined by [61] for juvenile Oncorhynchus kisutch (Coho salmon, LC50= 0.032 mg/L) and juvenile Oncorhynchus gorbuscha (pink salmon, LC50 = 0.023–0.052 mg/L). Exposing fish to chlorine adversely impacts the structure of the gill with an increase in mucus production around the gill and destruction of the respiratory wall epithelium [11] [19] [65]. Exposure to sub-lethal levels of chlorine to bluegill and rainbow trout caused histological damage to the gills ultimately resulting in death by asphyxia [11].
The results of [59] demonstrated the effect of exposure methods i.e. flow through versus static systems. The LC50 for the crustacean, Ceriodaphnia dubia in a 24 hour flow through test at 25°C was equal or greater than 0.005 mg/L. The LC50 determined under static conditions was 0.048 mg/L which is in the range of the values reported in 17 at the same temperature. Essentially a 10-fold increase in LC50 was observed, driven mostly by the difference in exposure condition. However, semistatic exposure was the method of choice in this study as this is more representative of how industries operating within the Arabian Gulf administer chlorine to counter act the biofouling in the cooling pipes.
Studies have reported that early developmental stages of fish and invertebrates were more sensitive to toxicants than the adults [38] [40] [54] [42]. The variability in sensitivity may be due to several factors; surface area/volume ratio (particularly with juvenile fish); greater uptake of toxicant from environment; under developed homeostatic mechanism to deal with toxicants; immature immune system and under developed organs (liver and kidney) which has an important role in detoxification and elimination of toxicants. For fish, it has been reported in this study and in others [62], that the juveniles are more sensitive than embryos. The difference in the effect of chlorine between embryos, juveniles and adults reported in this study could be attributed to the chorion, the membrane surrounding the egg. As previously demonstrated the chorion is believed to provide a barrier against substances in early stages of embryo development because of the water hardening of the chorion, allowing the egg to become mechanically more resistant and possibly restricting the entrance of waterborne substances into the perivitelline fluid.
Temperature affects the physiology of organisms and there is a point when the temperature is too low or too high that death may occur. Organisms have a range of temperature that they can tolerate without any adverse effects. When the temperature changes in the environment, all the cold-blooded organisms would adjust their body temperatures to be equal to the external temperature. The rate of heat exchange in these organisms is very rapid and as such their metabolic rate will increase. 23 showed that metabolic rates increase with an increase in temperature for tallest fish. The relationship between metabolic rate and temperature is often expressed as Q10, which measures the rate of increase for every 10ºC rise in temperature. For coldblooded animals, the Q10 ranges from a factor of 2 to [23]. Since temperature alone can be lethal, when an organism is exposed to a chemical at an elevated temperature, a synergistic effect could occur and enhanced toxicity may be observed.
However, there was a common observation among species that between 23-27°C there was a noticeable relative increase in toxicity. This temperature is more than the average measured (22°C ± 0.2) in the Arabian Gulf. At high temperatures such as 27°C the metabolic rate of the species would be expected to increase, which could have enhanced the toxicity as found in this study showing a synergistic effect of both chlorine and temperature. Furthermore, at higher temperatures (higher than 32°C) increased evaporation of available chlorine in the waters might have reduced exposure in the animals. At low temperatures, 16°C, the metabolic rate of the animal decreases to a lower level which would lower the negative impact of chlorine.
In general, the sensitivities of the native species tested in this study were similar to those reported in previous studies of nonnative species. It is in range with previous studies which reported that toxicity value for planktonic crustacean Ceriodaphnia dubia was 0. 056 mg/L [59] for 10d lifecycle test. [9] reported that 21-d no observed effect concentration (NOEC) for the survival of Pimephales promelas was 0.026 mg/L. The 28-d-EC10 for growth of fish Aphanius dispar in this study was 0.026 mg/L, and previous studies reported that 28 days NOEC for survival of Menidia peninsulae and Oryzias javanicusb were 0.04 and 0.078 mg/L, respectively [34].
Based on the comparison in this study, the SSD curves [Figure. 4], indicated that the native Arabian Gulf organisms with acute exposures to chlorine were as sensitive as the non-native species that have been used in deriving WQC elsewhere. The HC5s were 0.054, 0.039, and 0.045 mg/L, respectively. Previous study found that natural history, habitat type and geographical distribution of the species used to construct the SSD did not have a significant influence on the assessment of hazard, and this was in accordance with this study [39] [31).
For the present study, the species sensitivity distribution (SSD) based on both native and non-native species was generated. The question was brought up [26] [67] about the feasibility of using toxicity data of species from one geographical region to assess the ecological risk posed to species in a different region. Moreover, differences in the sensitivity of cold-water, temperate, and tropical fish species have been reported [6] [25] [67]. Since there has been limited information on the toxicity of chlorine to native and non-native species, comparison could only be conducted on the SSDs constructed from acute toxicity data of native and non-native [5] [43] [64].
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