Transylv. Rev. Syst. Ecol. Res. 8, (2009), "The Wetlands Diversity" 1 NAJAS SPP. GROWTH IN RELATION TO ENVIRONMENTAL FACTORS IN WADI ALLAQI (NASSER LAKE, EGYPT) Hoda YACOUB * * Egyptian Environmental Affairs, Nature Conservation Department, Wadi Allaqi Biosphere Reserve, Environmental Regional Building, Sadaat Road, Aswan, Egypt, [email protected] KEYWORDS: Egypt, Lake Nasser, Wadi Allaqi, Najas spp., human impacts, canonical correspondence analysis (CCA), fodder resources. ABSTRACT The study aims to evaluate the pattern of Najas spp. (aquatic plant) distribution along the shores of Allaqi, Lake Nasser, to identify the effect of physico-chemical variables on the growth and on the expansion of the plants. Najas spp. is vital for nomadic groups (Bedouins) living in the area, they harvest the plant out of lake to utilize it as fodder resource for their sheep and goats. Drought conditions that extended more than ten years increase the demands for the plants, in order to compensate the reduction of available grazing areas and the lack of grazing terrestrial plants. It was noticed that Najas growth declined in many areas in Allaqi due to anthropogenic and natural factors. Najas was exposed to negative conditions caused by human activities, including shores agriculture and fishing. The dense flocks of large migratory birds and the expansion of aquatic plants (other species of macrophytes and epiphytes) are additional factors that threat in many ways the Najas spp. presence. Environmental patterns were assessed over 17 abiotic parameters related to water (depth, temperature, pH, TDS, conductivity, dissolved oxygen, light transparency, phosphate, nitrate, nitrite, ammonium, sulphate) and hydrosoil (phosphate, nitrate, nitrite, ammonium, organic matter). Three field samplings were performed (May, July and September 2008) in the period when Najas (mainly Najas horrida which is dominant) starts and completes its life cycle; this period also represents the maximum human impact (harvesting time of Najas by Bedouins and the period of shores cultivation) covering a wide range of natural and anthropogenic conditions variations. The temporal and spatial variation of Najas spp. growth was obvious in Allaqi due to conditions related to: 1) variation in water and hydrosoil qualities caused mainly by human impacts, 2) variation in the nature and physical features of the shores, 3) mechanical damage from migratory birds and 4) competition of epiphytes and other macrophytes species for light, nutrients oxygen and space. CCA statistical technique was extremely useful in understanding the response of different Najas species growing in Allaqi (Najas horrida, Najas marina subsp. armata and Najas minor) to various conditions. It indicated that depth, TDS, water ammonium and hydrosoil phosphate are the key factors that control Najas growth in Allaqi, and this agreed with field observation, where Najas thrived and dominated in shallow sheltered areas with low nutrient contents. Remarkable reduction in Najas growth was recorded at cultivated shores, due to fertilizers reaching the water, and causing high ammonium contents. Myriophyllum spicatum known to be a sever competitor, able to grow in wide range of environmental conditions, and our study showed that Myriophyllum was more adapted to unfavourable conditions than Najas, suggesting the invasive ability of this species in the future. 2 H. Yacoub – Najas spp. growth in relation to environmental factors in Wadi Allaqi (1 ~ 40) RÉSUMÉ: Le développement des espèces de Najas en relation avec les facteurs environnementaux dans le Wadi Allaqi (Lac Nasser, Egypte). L’étude vise l’évaluation des modèles de distribution de Najas spp. (plante aquatique) le long des rives d’Allaqi, Lac Nasser ainsi que l’identification des effets des paramètres physiques et chimiques sur la croissance et l’expansion de la plante. Najas spp. est une plante vitale pour les populations nomades (Bédouins) de la région, qui ramassent la plante du lac et l’utilisent en tant que fourrage pour leurs moutons et chèvres. Les conditions de sécheresse qui se sont maintenues sur plus de dix ans ont augmenté la demande pour cette plante appelée à compenser la réduction des pâturages disponibles et le manque des plantes terrestres disponibles. Nous avons remarqué le fait que la croissance de Najas a reculé dans plusieurs régions d’Allaqi à cause des facteurs naturels et anthropogéniques. Najas a été exposée à des conditions négatives à cause des activités humaines tel que la pèche et l’agriculture littorale. Les colonies de grands oiseaux migrateurs et l’expansion des plantes aquatiques (autres espèces de macrophytes et d’épiphytes) sont d’autres facteurs qui menacent de plusieurs façons la présence de Najas spp. Les modèles environnementaux ont été évalués sur la base de 17 paramètres abiotiques liés à l’eau (profondeur, température, pH, TDS, conductivité, oxygène dissout, transparence, phosphate, nitrate, nitrite, ammoniac, sulfate) et aux hydrosols (phosphate, nitrate, nitrite, ammoniac, matière organique). Trois campagnes de prélèvement ont été entreprises (mai, juillet et septembre 2008) pendant la période dans laquelle Najas (principalement Najas horrida, qui est dominante) commence et finit son cycle de vie, période également concernée par le maximum de l’impacte anthropique (la période de cueillette de Najas par les Bédouins et la période de culture des berges) couvrant une large palette de variations des conditions naturelles et non naturelles. La variation temporelle et spatiale de l’expansion de Najas spp. a été si visible à Allaqi à cause des conditions liées à: 1) des variations dans la qualité de l’eau et des hydrosols dues principalement à l’impacte anthropique; 2) des variations des caractéristiques naturelles et physiques des berges; 3) l’altération mécanique due aux oiseaux migratoires et 4) la compétition des espèces épiphytes et d’autres espèces macrophytes pour la lumière, les nutriments, l’oxygène et l’espace. La techniques statistique CAA a été particulièrement utile dans la compréhension des réponses des différentes espèces de Najas qui poussent à Allaqi (Najas horrida, Najas marina subsp. armata et Najas minor) à des différentes conditions. Cette analyse a indiqué le fait la profondeur, TDS, l’ammoniac de l’eau et le phosphate des hydrosols sont les facteurs clef qui contrôlent la croissance de Najas à Allaqi, fait confirmé par les observations du terrain indiquant le fait que Najas s’est bien développé et a dominé les régions abritées et peu profondes avec un faible contenu de nutriments. La réduction la plus importante des effectifs de Najas a été enregistrée pour les berges cultivées à cause des engrais mobilisés dans l’eau qui ont augmenté les concentrations d’ammoniac. Myriophyllum spicatum, connu en tant que compétiteur féroce, capable de pousser dans une large gamme de conditions, a été démontré par notre étude en tant que mieux adapté que Najas aux facteurs adverses, suggérant que cette espèce pourrait devenir invasive par la suite. REZUMAT: Dezvoltarea subspeciilor de Najas în relaţie cu factori de mediu în Wadi Allaqi (Lacul Nasser, Egipt). Studiul urmăreşte evaluarea modelelor de distribuţie ale Najas spp., (plantă acvatică) în zona litorală Allaqi a Lacului Nasser, precum şi identificarea efectelor diferiţilor factori fizico-chimici asupra dezvoltării şi expansiunii acestei plante. Najas spp. este vitală pentru grupurile nomade din regiune (beduini), care o recoltează şi o folosesc pentru furajarea oilor şi caprelor. Seceta care a durat peste zece ani în zonă a făcut ca presiunea asupra acestei plante să Transylv. Rev. Syst. Ecol. Res. 8, (2009), "The Wetlands Diversity" 3 crească pentru a compensa reducerea zonelor de păşunat disponibile şi lipsa plantelor terestre. S-a remarcat faptul că Najas nu a mai crescut în mai multe sectoare din Allaqi, datorită unor factori naturali şi antropogeni. Najas a fost expusă la condiţii de mediu negative datorită unor activităţi umane, precum pescuitul şi agricultura, practicate pe lângă maluri. Coloniile de păsări migratoare mari şi invazia plantelor acvatice (alte specii de macrofite şi epifite) sunt alţi factori care ameninţă în diferite feluri prezenţa Najas spp. Modelele ecologice au fost evaluate pe baza a 17 parametri abiotici ai apei (adâncime, temperatură, pH, TDS, conductivitate, oxigen dizolvat, transparenţă, fosfat, nitrat, nitrit, amoniac, sulfat) şi hidrosolurilor (fosfat, nitriat, nitrit, materie organică). Au fost efectuate trei campanii de teren (mai, iulie şi septembrie 2008) în perioada de început şi de final a ciclului de viaţă la Najas (în special la Najas horrida, specie dominantă), perioadă vizată şi de un maxim al activităţii antropice (perioada de recoltare a plantelor de Najas de către beduini şi de cultivare a malurilor), acoperind o paletă largă de variaţii ale condiţiilor naturale şi nu numai. Variaţia temporală şi spaţială a expansiunii Najas spp. a fost vizibilă la Allaqi din cauza condiţiilor de mediu legate de: 1) variaţii ale calităţii apei şi hidrosolurilor datorate în principal activităţilor antropice; 2) variaţii ale caracteristicilor naturale şi fizice ale malurilor; 3) deteriorarea mecanică datorată păsărilor migratoare şi 4) competiţia cu speciile epifite şi alte specii macrofite pentru lumină, nutrienţi, oxigen şi spaţiu. Tehnica statistică CAA a fost deosebit de utilă în înţelegerea răspunsurilor diferitelor specii de Najas prezente la Allaqi (Najas horrida, Najas marina subsp. armata şi Najas minor) la diferite condiţii de