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Basic Research Journal of Soil and Environmental Science ISSN 2345-4090 Vol. 2(4) pp. 51-56 December 2013 Available online http//www.basicresearchjournals.org Copyright ©2012 Basic Research Journal Full Length Research Paper Interactions between phytoplankton, zooplankton and fish in the Massa estuary *1Badsi Hind, 2Oulad Ali Hassan, 3Loudiki Mohammed, 4Aamiri Ahmed 1 Laboratory of Oceanography and Limnology, Department of Biology, Faculty of Sciences, Ibn Zohr University, Agadir, Morocco. 2 Laboratory of Oceanography and Limnology, Department of Biology, Faculty of Sciences, Ibn Zohr University, Agadir, Morocco. 3 Laboratory of Biology and Biotechnology of Microorganisms, Department of Biology, Faculty of Sciences, Semlalia Cadi Ayyad University, Marrakech, Morocco. 4 Laboratory of Oceanography and Limnology, Department of Biology, Faculty of Sciences, Ibn Zohr University, Agadir, Morocco. *Corresponding author email: [email protected] Accepted 18 December 2013 The interactions between phytoplankton and zooplankton was studied from march 2009 to April 2011 at seven stations. In spite of large weekly variations in the abundance and community structure, phytoplankton and zooplankton usually showed an obvious inverse relationship during different periods. However, the density of phytoplankton seems to be due to the existence of unfavorable phytoplankton species to be grazed by zooplankton. The grazing appeared to be affected by the environmental conditions, like salinity, a temperature, also the species composition of both phytoplankton and zooplankton communities. The preliminary study of stomcal contents of Chelon labrosus and Mugil cephalus fish species showed that their food spectra clearly dominated by algae. Keyword: Massa estuary, phytoplankton, zooplankton, fish, stomacal contents. INTRODUCTION The simultaneous study of the phytoplankton and zooplankton communities is crucial for understanding the functioning of the ecosystem. It is well known that the density, species composition and size distribution of phytoplankton are controlled not only by nutrient conditions, but also by the zooplankton (Sarnelle, 1993; Kivi et al., 1993). The impact of physicochemical parameters and phytozooplankton interactions have been several studies limnology, for against the role of fish on the structure and dynamics of ecosystems has been less studied (Persson et al., 1988). Fish predation to impact on zooplankton on phytoplankton and other biotic component (Lazzaro and LacroixG, 1995). This study is a contribution to the understanding of the structure of the food web of the estuary of Massa and we present here the results of studies of the interactions between phytoplankton community and the population of zooplankton on the one hand and the relationship between the two phyto- zooplankton communities with predation by fish inhabit the Massa estuary . MATERIAL AND METHODS The sampling stations were chosen to allow us to meet Badsi et al. 52 Figure 1. The Study area and positions of sampling stations the objective of our study and taking into account a number of factors including the representativeness of the estuary for many spatially identify the importance of stations and accessibility, seven stations, are selected (figure 1). Phytoplankton and zooplankton were collected with a bottle “Wildco” kind to collect a volume of water to any depth desired. For phytoplankton study, 6 liters of water were collected at each station, preserved in 4% neutralized formaldehyde. The supernatant water was then decanted and the concentrated were examined for species identification and counting. For zooplankton 6 liters of water were collected at each stations and preserved in 5%formol and then examined and counted. Principal component analysis was employed to detect the correlations between the different groups of both phytoplankton and zooplankton. We chose two types of fish Chelon labrosus and Mugil cephalus wich have a wide geographical distribution and grouping both tropical, subtropical and temperate regions. Several studies have been devoted (Ameur, 1994; El Housni, 1988; Ould, 1892). RESULT AND DISCUSSION Interaction between Phytopalnkton and Zooplankton before the floods The comparative evolution of phytoplankton and zooplankton populations has allowed us to observe a lack of proportionality in particular before the opening of the sand dune. This could be related to poor quality algae and the effect of predation by fish and plankton larvae Chaoborus. Frequent blooms of Microcystis aeruginosa are hardly grazed by species zooplankton. The high abundance of phytoplankton at the closed and shallow estuary Massa suggests that primary producers in this phase are not controlled by grazing due to the presence of unpalatable species and low nutritional value, the small zooplankton as it is the group of Rotifers herbivors, scavengers that dominate the estuary and the absence of large of Cladocera especially downstream. The analysis of large phytoplankton and zooplankton groups (figure 2) showed associations between Rotifers (Brachionus plicatilis , Brachionus urceolaris and 53. Basic Res. J. Soil Environ. Sci. Figure 2. Principal Component Analysis of the phytoplankton and zooplankton groups before the floods. Hexarthra fennica) Harpacticoid (Epactophanes richardi, Moraria sp) and Cyanophyceae (Microcystis aeruginosa, Anabaena sp) The associations we observed are similar to those observed in several studies that have shown a positive correlation between Rotifers and proliferations of Cyanobacteria in systems having a tendency to eutrophication (Bonecker et al., 2001; Leonard and Paerl, 2005). The association between potentially toxic Cyanobacteria (Microcystis aeruginosa, Gloeocapsa turgida and Anabaena sp) and some species of zooplankton (Rotifers: the genus Brachionus) in Massa estuary is consistent with several studies showing that some zooplankton species can coexist in the presence of toxins produced by cyanobacteria. Indeed, (Ferrao-Filho et al., 2009a) have shown that Cyanobacterial toxins may be responsable for the predominance of more resistant species such as Copepods and Rotifers, Similarly, data analysis based on major taxonomic groups at Massa shown that Cladocerans (Chydorus sphearicus, Ceriodaphnia reticulata and Ceriodaphnia quardangula) and Calanoides (Diaptomus sp) are negatively correlated with the Cyanophyceae (Microcystis aeruginosa, Gloecapsa turgida). This is due to the inefficiency of these large grazers to consume filamentous Cyanobacteria. The downstream stations (Ameur, 1994; Bonecker et al., 2001; El Housni, 1988) where eutrophication is accentuated because of the low water renewal are associated with groups of phytoplankton (diatoms and Cyanophyceae) and zooplankton (Rotifers). At the upstream sector (Gliwicz, 1994; Haddad, 1996; Heinbokel et al., 1988), where eutrophication is less acute is with more transparent waters are associated with diatoms and Chlorophyceae for phytoplankton, the Rotifers, Cladocerans and Cyclopoid for zooplankton (Figure 2). Interaction between Phytopalnkton and Zooplankton after the floods After the opening of the estuary (Figure 3), the first factorial explains 88.60% of variance, with 73.68% for the first axis. It is observed that Dictyophyceae (Dictyocha fibula) and Dinophyceae (Prorocentrum micans, Alexandrium minutum) are positively correlated to Calanoides (and "other organizations" zooplankton, Chlorophyceae (Merismopedia, Scenedesmus falcatus) and Euglenophycées (Euglena texta) are positively correlated with Cladocerans (Ceriodaphnia reticulata, Bosmia longirostris) and Cyclopoid and oppose Cyanophyceae (Scenedesmus). Zygophyceae that are related to rotifers (Polyarthra vulgaris). Cyclopoid and Cladocera and have a very strong correlation between them and have a positive relationship with Euglenophycées and diatoms (Cyclotella ocellata, Navicula cryptocyphala...). These groups show a negative association with marine Calanoides (Centropages typicus Paracalanus parvus) (Figure 3). On the Axis 2 (14.92%) was observed that diatoms Badsi et al. 54 Figure 3. Principal Component Analysis on the phytoplankton and zooplankton groups after the floods. (Cyclotella ocellata, Navicula cryptocephala) are associated with Calanoides (Diaptomus sp) and oppose Cladocerans (Ceriodaphnia reticulata, Bosmina longirostris), the cyclopoid (Tropocyclops prasinus, Acanthocyclps robustus) and Rotifers (Brachiouns plicatilis, Polyarthra vulgaris). Latter group shows a positive correlation with Zygophyceae and Cyanophyceae. We found a correlation between the densities of phytoplankton and Zooplankton. This may be due to two main factors: nutrient regeneration by Zooplankton, which leads to an increase in Phytoplankton abundance, and the effect of predation on fish inhabit the Massa estuary on Zooplankton community that fosters the development phytoplankton. The pressure of zooplankton grazing on phytoplankton is less pronounced especially at the downstream sector as it is populated by small species (Rotifers) and less than Copepods. Downstream, in addition to Rotifers, Copepods we have engaged a grazing Cladocera more on phytoplankton species. This observation explain the significant correlation between groups of dominant Zooplankton (Rotifers, Copepods and Cladocerans) and most groups of Phytoplankton (Diatoms, Cyanophyceae, Chlorophyceae and Euglenophyceae at the Massa estuary. Befor the floods, predation intra- Zooplankton in the Massa estuary has a role in the structuring Zooplankton communities through association predator - prey. In our study, Asplanchna priodonta is mainly associated with rotifers of the genus Brachionus, which are potential prey for this species. Indeed, the sharp decline of Brachionus plicatilis for development Asplanchna priodonta in summer 2009 including at stations 4 and 5 confirms that Brachionus is diet favorable Asplanchna priodonta. After the flood, we did not observe an effect of grazing on phytoplankton. Indeed, the dinoflagellate Prorocentrum micans is impreferable Zooplankton species and this species could have a harmful effect on Calanoides grazers who peuplement estuary downstream. It is therefore concluded that the Dinoflagellates seem to be not preferable by different zooplankton during the present study, a case which is in agreement with (Ismael and Abdel-Aziz, 2003) who reported that the dinoflagellates Prorocentrum micans, P. minimum and P. triestinum are unsuitable food for microand meso-zooplankton. (Heinbokel et al., 1988) noted that rotifers often constituting the dominant grazer on the dinoflagellates. Befor the floods both Rotifers Brachionus plicatilis and Brachionus urceolaris feed Cyclotella ocellata and Navicula cryptocephala, and we have seen the development of two species of Rotifers, which coincides with the decline of two Phytoplankton species, such as in March 2009, we noted a peak due to intense development, Cyclotella ocellata and Navicula cryptocephala , which is accompanied by low densities of both Rotifers Brachionus plicatilis and Brachionus urceolaris. A reverse relationship was observed between 55. Basic Res. J. Soil Environ. Sci. Polyarthra vulgaris and two Cyclops Tropocyclops parasinus and Acanthocyclops robustus and saw the development of Polyarthra vulgaris in July and August 2009 and is accompanied by low densities or even the disappearance of the two Cyclops Tropocyclops parasinus and Acanthocyclops robustus and aims to it. This allows us to conclude that the two Cyclops show selectivity for food of Polyarthra vulgaris. Our findings therefore bring a similar result compared to the literature (Gliwicz, 1994). For phytoplankton population, both Cyclops show a selectivity of the diatom Cyclotella ocellata. In fact, usually the peak densities of the two Cyclops in April and October 2009 caused significant decrease in the abundance of Cyclotella ocellata this allows us to suggest the use of this diatom small by Cyclops. The abundance of large grazers (Calanoides and large Cladocera) is generally observed during the absence or in the reduction of Cyanobacteria which is in agreement with the observation of (Lampert, 1987). Interaction between fish and plankton Fish-phytoplankton: 101 stomcal contents was examined, the results show that the stomach contents of both species are similar. They show the dominance of phytoplankton. The analysis of the diet of both species shows that in terms of biomass the phytoplankton population is better represented in the digestive tract of fish. Differs result from what has been found by Haddad (1996). Indeed, the presence of phytoplankton in the contents of digestive tracts indicates that these fish could contribute to improving the water quality in the Massa estuary by reducing algal biomass. *Mugil cephalus: phytoplankton fraction consists of diatoms (Bacillariophyceae (95%), Cyanophyceae (3%) and Euglenophyceae (2%). *Chelon labrosus: phytoplankton fraction includes pinnate and centric diatoms (94%), Cyanophyceae (4%) and Euglenophyceae (2%). Fish Fish –zooplankton *Mugil cephalus: animal fraction is represented by 43% attributed to Copepods, Cladocerans 29% and 19% of Rotifers. *Chelon labrosus: stomach contents is presented by 41% copepods, 27% of 18% of cladocerans and rotifers 14% ostracods. This is especially eggs of Brachionus and individuals who dominate. The low percentage densities of zooplankton in the stomach contents of two species in relation to phytoplankton biomass relative contribution and energy intake of zooplankton could be relatively higher than that of phytoplankton. The results obtained in this study revealed the adaptation of the two species to trophic environmental conditions CONCLUSION The interaction between phytoplankton and zooplankton is regulated by environmental factors, the composition and abundance of the two communities. The Zooplankton is committed by either selective or non- selective mechanisms, but sometimes a species of Zooplankton can toggle between the two mechanisms depending on the composition of Phytoplankton available. The interaction between Phytoplankton and Zooplankton in the estuary Massa is regulated by environmental factors, grazing by Zooplankton and the composition and abundance of both phyto- zooplankton communities. Indeed, zooplankton grazing is committed by either selective or non- selective mechanisms, based on the composition of phytoplankton available. The study of diet showed a diet mainly Zoophytoplanctonophage for both species with different food preferences. A broad food spectrum reflecting the adaptation of these species to trophic environmental conditions. The high Phytoplankton fraction constituting the gut contents of fish fauna studied is strongly reduced Phytoplankton biomass. REFERENCE Ameur B (1994). Aspects biologiques et dynamiques de la population de Mugil cephalus (Poissons, Mugillidés) de la lagune de Moulay Bousselham (Maroc). Doctorat de 3ème cycle, Univ. Mohammed V, Fac. Sci. Rabat, 93 p. Bonecker CC, Lansac-Tôha FA, Velho LFM, Rossa DC (2001). The temporal distribution patterns of copepods in Corumbá. Reservoir, State of Goiás, Brazil. Hydrobiologia,453/454: 375-384 El Housni A (1988). Les poissons de la réserve naturelle de Massa (Agadir). 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