Figure 1
The water sampling sites in the east – sites 1, 2, 3, the middle – sites 4, 5, 6, 7 and the west subarea – 8, 9, 10 in Lake Qarun in 2012, and the main landing sites for fish catch: 1) Senoris, 2) Abu-Neema, 3) Shakshouk, 4) Abu-Soliman, 5) Abu-Shanab, 6) Kahk, 7) El-Lokanda, 8) El-Rawashdia, 9) El-Saaida, 10) Ayuob and 11) Qarun
Figure 2
Environmental parameters (mean, mean±standard error, min.-max) in Lake Qarun in 2012, the codes of 10 sampling sites were given in Fig. 1
Table 1
The trophic-level based (TLI – Trophic Level Index) assessment of Lake Qarun in 2012 compared to partly available data on SDD, TP and TN from 1995 to 20061
| Subareas | Sites2 | TLISDD | TLIChl | TLITP | TLITN | TLI | Trophic state |
|---|---|---|---|---|---|---|---|
| East | 1 | 6.03 | 5.87 | 8.17 | 8.08 | 7.04 | HYP |
| 2 | 5.61 | 6.28 | 6.93 | 7.02 | 6.46 | HYP | |
| 3 | 5.32 | 6.06 | 7.06 | 7.02 | 6.36 | HYP | |
| Middle | 4 | 5.22 | 5.95 | 6.86 | 6.49 | 6.13 | HYP |
| 5 | 5.21 | 5.81 | 6.67 | 7.05 | 6.19 | HYP | |
| 6 | 4.85 | 4.92 | 6.92 | 7.15 | 5.96 | EUT | |
| 7 | 5.72 | 5.05 | 7.71 | 7.00 | 6.37 | HYP | |
| West | 8 | 4.89 | 4.74 | 7.10 | 7.15 | 5.97 | EUT |
| 9 | 5.13 | 4.40 | 7.28 | 7.26 | 6.02 | HYP | |
| 10 | 4.91 | 4.85 | 7.02 | 7.31 | 6.02 | HYP | |
| 1995 | average for the whole lake | 5.69 | - | 6.29 | 8.05 | 6.684 | HYP |
| 1999-2000 | 5.59 | - | 6.82 | - | 6.214 | HYP | |
| 2003 | 5.68 | - | 7.71 | - | 6.704 | HYP | |
| 2006 | 5.57 | - | 8.30 | - | 6.944 | HYP | |
| 20123 | 5.23 | 5.56 | 7.25 | 7.17 | 6.30 | HYP |
1 Based on data cited in El-Shabrawy & Dumont (2009), Satar et al. (2010) and El-Shabrawy et al. (2015)
2 The codes of sites’ names are given in Fig. 1, TLI – the trophic level index based on Secchi disc depth – TLISDD, chlorophyll a concentration – TLIChl, total phosphorus concentration – TLITP, total nitrogen concentration – TLITN, HYP – hypereutrophic, EUT – eutrophic according to Parparov et al. (2010), – no data
Figure 3
The annual phytoplankton density (A) and its composition (B) in Lake Qarun in 2012, the codes of 10 sampling sites were given in Fig. 1
Figure 4
Cluster analysis based on phytoplankton taxa similarity in Lake Qarun in 2012, the codes of S1-10 sampling sites were given in Fig. 1
Figure 5
Seasonal structure of phytoplankton in Lake Qarun in 2012
Table 2
Dominant species in phytoplankton assemblages in Lake Qarun in 2012
| Species* | Sampling sites** | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | |
| Spring | ||||||||||
| Aphanocapsa elachista var. conferta West & G. S. West | + | + | + | - | + | + | - | - | - | + |
| Aulacoseira granulata (Ehr.) Sim. | - | - | - | - | - | + | + | + | + | + |
| Chroococcus dispersus (Keiss.) Lemm. | - | - | - | - | - | + | - | + | + | - |
| Coscinodiscus lacustris Grun. | + | + | + | - | + | + | + | + | + | + |
| Cosmarium nitidulum De Notaris | - | - | - | + | + | - | + | - | - | + |
| Crucigenia tetrapedia (Kirch.) Kuntze | + | - | + | + | + | - | - | + | + | - |
| Cyclotella glomerata Bach. | + | + | + | + | - | + | - | + | + | + |
| Cyclotella operculata (C. Agardh) Bréb. | - | - | - | - | - | - | + | + | + | + |
| Desmodesmus protuberans (F. E. Fritsch & M. F. Rich) E. Heg. | - | + | + | - | + | + | + | - | - | - |
| Gomphonema truncatum Ehr. | + | + | + | + | + | + | - | + | + | + |
| Lindavia kuetzingiana (Thwait.) T. Nakov et al. | + | + | + | - | + | - | + | - | - | - |
| Lindavia ocellata (Pant.) T. Nakov et al. | + | - | - | - | - | + | - | - | - | - |
| Mallomonas ploesslii Perty | - | + | - | - | - | + | - | + | - | + |
| Mallomonas sp. | + | - | + | + | + | - | - | - | - | - |
| Navicula dicephala Ehr. | - | - | - | + | + | - | + | - | - | + |
| Nitzschia acicularis (Kütz.) W. Smith | + | - | + | + | + | + | + | - | - | + |
| Ulnaria ulna (Nitzsch) P. Comp. | + | + | + | + | + | + | - | + | + | + |
| Summer | ||||||||||
| Cosmarium sp. | - | - | + | + | - | - | - | - | + | + |
| Cyclotella glomerata Bach. | - | - | - | - | - | - | - | + | + | + |
| Lindavia ocellata (Pant.) T. Nakov et al. | - | - | + | + | + | + | + | + | - | + |
| Mallomonas helvetica Pasch. | + | + | + | + | - | - | - | - | - | - |
| Mallomonas sp. | - | - | - | - | + | - | - | - | - | + |
| Nusuttodinium aeruginosum (F. Stein) Y. Tak. & T. Hor. | + | + | + | + | + | + | - | + | + | + |
| Parvodinium pusillum (Penard) S. Carty | + | + | + | + | + | - | - | - | - | + |
| Parvodinium umbonatum (Stein) S. Carty | + | + | + | + | + | + | - | + | - | + |
| Prorocentrum micans Ehr. | + | + | + | + | + | + | + | + | + | + |
| Rhabdoderma lineare Schmid. & Laut. | - | - | - | - | - | - | - | - | + | - |
| Schroederia nitzschioides (G. S. West) Korsch. | - | + | + | + | + | + | + | - | - | - |
| Ulnaria ulna (Nitzsch) P. Comp. | + | + | + | - | + | + | + | - | - | + |
| Autumn | ||||||||||
| Achnanthidium minutissimum (Kütz.) Czarn. | - | - | - | + | - | + | - | - | - | + |
| Amphora ovalis (Kützing) Kützing | - | - | - | + | - | - | - | - | - | - |
| Aphanocapsa elachista var. conferta West & G. S. West | + | + | + | - | + | - | + | + | + | - |
| Aulacoseira granulata (Ehr.) Sim. | + | - | - | + | - | - | + | - | + | + |
| Chlamydomonas globosa J. W. Snow | - | + | + | + | + | + | - | - | + | + |
| Chroococcus dispersus (Keiss.) Lemm. | + | - | - | - | - | - | + | + | - | - |
| Cosmarium nitidulum De Notaris | - | - | + | - | - | - | - | + | - | + |
| Cyclotella glomerata Bach. | - | - | + | + | - | + | - | - | - | - |
| Lindavia ocellata (Pant.) T. Nakov et al. | + | + | + | - | - | + | + | + | + | - |
| Mallomonas ploesslii Perty | - | - | - | - | + | - | + | - | - | - |
| Prorocentrum micans Ehr. | + | + | + | + | + | + | + | + | + | + |
| Prorocentrum scutellum Schröd. | - | + | + | - | + | - | + | - | - | + |
| Scenedesmus quadricauda (Turp.) Bréb. | + | - | - | - | - | - | - | + | - | - |
| Thalassiosira leptopus (Grun. ex Van Heurck) Hasle & G. Fryx. | - | - | - | - | + | - | + | + | + | - |
| Trachelomonas dubia Svir. [Swir.] | - | + | + | - | - | - | - | - | - | - |
| Ulnaria ulna (Nitzsch) P. Comp. | + | - | + | + | + | + | - | + | + | + |
| Winter | ||||||||||
| Conticribra guillardii (Has.) K. Stach.-Such. & D. M. Will. | - | - | - | + | + | + | + | + | + | + |
| Cosmarium nitidulum De Notaris | - | - | - | - | - | + | + | + | - | + |
| Cyclotella glomerata Bach. | + | + | + | + | + | - | + | - | + | + |
| Cyclotella meneghiniana Kütz. | + | + | + | + | + | + | + | + | - | + |
| Cyclotella operculata (C. Agardh) Bréb. | + | + | + | + | + | + | + | - | + | + |
| Cyclotella schroeteri Lemm. | - | - | - | + | + | + | - | - | - | + |
| Gymnodinium colymbeticum T. M. Harris | + | + | + | + | + | + | + | + | + | + |
| Lindavia ocellata (Pant.) T. Nakov et al. | - | + | + | + | + | - | + | + | - | - |
| Prorocentrum micans Ehr. | + | + | + | + | + | + | + | + | + | + |
| Prorocentrum scutellum Schröd. | + | + | + | + | + | + | + | + | - | - |
| Staurastrum paradoxum Mey. ex Ralfs | - | - | - | - | - | + | + | + | + | - |
| Ulnaria ulna (Nitzsch) P. Comp. | + | + | + | + | + | + | + | + | + | + |
* the currently accepted taxonomical names of species according to Guiry & Guiry (2016)
** the codes of 10 sampling sites were given in Fig. 1,
Figure 6
Fish and seafood catches from Lake Qarun and their composition during the period of 2003-2012 according to GAFRD (2013)
Table 3
Seasonal variation in fish and seafood catches in subareas of Lake Qarun in 2012
| Subarea | East | Middle | West | Total | |||
|---|---|---|---|---|---|---|---|
| Season | winter | summer | winter | summer | winter | summer | |
| Catch, ton | 500.0 | 699.0 | 1146.7 | 427.0 | 314.7 | 1322.6 | 4410.0 |
| Catch, % | 11.34 | 15.85 | 26.00 | 9.68 | 7.14 | 29.99 | 100.0 |
| Subarea, % | 27.19 | 35.68 | 37.13 | ||||
Figure 7
Seasonal variation of catch composition in the east, middle and west subarea of Lake Qarun during the fishing season of 2012 according to GAFRD (2013)
Figure 8
Models (optimal trend lines) of changes in phytoplankton, chlorophyll a and Secchi disk depth at the study sites (A) and the total catch with dominant fish in summer and winter (B) in three subareas of Lake Qarun
Table 4
Statistical relationships (R-Spearman correlation coefficient) between physicochemical and biological variables in Lake Qarun
| Variables | Total catch | Mugil cephalus | Tilapia zillii | Solea spp. | Engraulis encrasicolus | Others |
|---|---|---|---|---|---|---|
| Total catch | - | 0.829 | n.s. | n.s. | n.s. | n.s. |
| Mugil cephalus | 0.829 | - | n.s. | n.s. | n.s. | n.s. |
| Tilapia zillii | n.s. | n.s. | - | n.s. | n.s. | n.s. |
| Solea spp. | n.s. | n.s. | n.s. | - | n.s. | n.s. |
| Engraulis encrasicolus | n.s. | n.s. | n.s. | n.s. | - | n.s. |
| Other fish species | n.s. | n.s. | n.s. | n.s. | n.s. | - |
| Phytoplankton density | n.s. | n.s. | n.s. | -0.943 | n.s. | n.s. |
| Bacillariophyceae | n.s. | n.s. | n.s. | n.s. | n.s. | n.s. |
| Dinophyceae | n.s. | n.s. | 0.943 | -0.829 | n.s. | n.s. |
| Chlorophyll a | n.s. | n.s. | n.s. | -0.943 | n.s. | n.s. |
| Total nitrogen | n.s. | n.s. | n.s. | n.s. | n.s. | n.s. |
| Total phosphorus | n.s. | n.s. | 0.943 | n.s. | n.s. | n.s. |
| Secchi disk depth | n.s. | n.s. | n.s. | n.s. | n.s. | n.s. |
| Trophic Level Index | n.s. | n.s. | 0.943 | n.s. | n.s. | n.s. |
| Ammonium | n.s. | n.s. | 0.829 | n.s. | n.s. | n.s. |
| Nitrite | n.s. | n.s. | n.s. | -0.829 | n.s. | n.s. |
| Nitrate | n.s. | n.s. | n.s. | -0.812 | n.s. | n.s. |
| Orthophosphate | n.s. | n.s. | n.s. | n.s. | n.s. | -0.943 |
| Temperature | n.s. | n.s. | n.s. | n.s. | n.s. | n.s. |
| Salinity | n.s. | n.s. | n.s. | 0.829 | n.s. | n.s. |
| pH | n.s. | n.s. | 0.829 | n.s. | n.s. | n.s. |
| Electrical conductivity | n.s. | n.s. | n.s. | 0.829 | n.s. | n.s. |
*statistically significant correlation, p<0.05, n = 40, n.s. – not significant