Monthly variations in density of attached algae on solid plates in two lentic and lotic localities from Basrah Province

A comparative study was performed on the Shatt Al-Arab River as a running water environment and a fishpond as a stagnant locality to investigate the distribution and abundance of attached algae. Samples were collected on monthly basis from November 2011 to October 2012. Two stations were selected in the Shatt Al-Arab River and just one in the lentic environment as it represents a thoroughly mixed water. Several ecological factors were analyzed and monthly variations were detected in all conditions, but a notable rise in water temperature and salinity was detected during the warmer period of year. Percentage composition of algae was calculated in the three investigated stations. Diatoms were dominant, followed by blue-green algae in the Shatt Al-Arab, but green algae in the pond. Three main algal taxa were encountered namely, Cyanophyceae, Chlorophyceae and Bacillariophyceae. The latter was represented by more species.


Introduction
Algae occupy an important position in the food chain as the main nutritional source for aquatic organisms (15).Algae are considered as primary producers of organic matters and oxygen, as byproduct, in aquatic habitats to stimulate their ability for photosynthesis and also their benefits for other organism.(23).However, the term benthic algae consist of species that live on the muddy bottom or nearby (31), in addition to algae growing on various submerged surfaces (13).Benthic algae are divided into muddy algae that stick or move freely on the surface of the muddy bottom (32), algae attached to submerged aquatic plants (2), algae attach themselves to submerged rocks in water and algae attached to aquatic animals i.e. epizootic algae (33).
Many environmental factors affect rate of primary production of benthic algae including light intensity, duration of light span, water temperature, salinity, Availability of nutrients, chlorophyll-a, the nature of bottom sediments, the effects of tides and the amount of organic carbon in sediments (21), (14) .
Benthic algae are used as bioindicators to evaluate the contamination of water with organic wastes (9).They are also play an important role in minimizing of environmental pollution through their bioaccumulation ability.(8) has pointed out that some have the ability to concentrate aromatic hydrocarbons and trace elements.Algae also possess an economic value by producing agar and alginates (30) and are used in various medical applications such as the production of antibiotics and as inhibitor to proliferation of microorganisms and tumors (5).Some other species are used for the production of different types of vitamins (3).
The present work is aiming to investigate some ecological factors affecting the productivity, abundance and distribution of attached algae and determining their monthly variations in densities in two, lotic and lentic, localities at Basrah Governorate.

Materials and Methods
Three stations were selected to perform the investigation.The former was at the confluence of the Shatt al-Arab River with Garmat Ali canal near Sinbad Island.(31˚38′ 30 34N,45˚00′ 47 76E) where it receiving considerable amounts of drainage water and industrial wastes released from Al-Najibiyah power plant.The second station (30˚50′ 6601N, 47˚85′ 382E) is located at heavily populated area at Al-Ashar district that receiving large quantities of domestic sewages in addition to wastes released by local boats.The third station(30˚04′ 2956N, 47˚74′ 128E),however, was stagnant locality represented by a fish pond, with an area of 6000-8000m 2 , of Basrah University fish farm (MSC) at Garmat Ali location.
Environmental factors, including water temperature, salinity and pH were measured at field using a YSI American-made Model (MPS 556).Current speed measured using Styrofoam floating object and output expressed as meters per second.Algal samples were collected depending on the method described by (11) and listed in (12).Solid plates of 30x15cm were used, fixed by wire and dropped in the water at depth range from 1-2 meters relying on the location.They placed tightly to avoid losing by irritation or effect of current speed.Three replicates of panels per month per stations were adopted and taking into consideration panels exposure during the ebb period.Panels raised monthly from the water source and algae attached on panels were removed with a brush then placed in plastic bottles of 25 cm 3 and logal solution was added for fixation and then transferred to the laboratory for further analyses.References adopted for the classification of algae are including (29), ( 26), ( 27), ( 28), ( 10) and (33).

Current speed
Figure (5) reveals the monthly changes in current speed in the three investigated locations.The highest value (1.94 m/sec.) was encountered in station1 in August compared to station2 where the highest (1.05 m/sec.)recorded in January.However, significant changes were not detected in the stagnant locality throughout the study period.

Qualitative study
The total number of algal species recorded during the study period was 86 belong to 38 genera (table 1) .This is clearly shown in figures 6, 7, 8.

Quantitative study
Figure (9) shows monthly changes in composition of algae in station1.Diatoms contribute from 125×10 3 -1000×10 3 individual/cm 2 .The lowest value encountered during August, while the highest in April.Then Green algae which ranged between 34x10 3 -858x10 3  individual/cm 2 .The minimal was recorded in August and the maximum in April.Whereas, blue-greens algae ranged between 19×10 3 -685×10 3  individual /cm 2 .The lowest value was recorded in January and the highest in April.Figure (10) reveals monthly changes in composition of algae in station2 during the investigated period.
Diatoms number ranged from 124x10 3 -1062x10 3 individual/cm 2 .The lowest encountered in August and the highest in April.Blue-green algae, however, occupied the second position and accounted for 20x10 3 -1007x10 3  individual/cm 2 .The minimal was recorded in August and the maximum in April.Whereas, Greens algae ranged between 39×10 3 -720×10 3 individual /cm 2 .The lowest value was recorded in May and the highest in April.
Figure (11) shows monthly differences in number of algae in station3 during the study period.Diatoms range from 44x10 3 to 1515x10 3 individual/cm 2 .The lowest value was encountered in January and the highest in April.Green algae, however, occupied the second position and accounted for 4x10 3 -1072x10 3  individual/cm 2 .The minimal was recorded in August and the maximum in April.Then blue-green algae which ranged between 10x10 3 -188x10 3 individual/cm 2 encountered in January and April respectively.Figure (12) shows monthly variations in total number of algae in the three selected station of the study area.The lowest values were recorded in station1 (102x10 3 individual/cm 2) and station2 (207x10 3 individual/cm 2 ).However, the lowest (83x10 3   individual/cm 2 ) was found in January in station3, whereas the highest 2543x10 3 , 2789x10 3 and 1775x10 3 were recorded in April for the three stations respectively.

Discussion
Water temperature possess great importance in aquatic life as affect the aquatic organisms directly or indirectly, and lead to impose essential impacts on properties of fresh water (16), through effecting content of dissolved oxygen and the rate of photosynthesis by the aquatic plants (22).However, salinity is considered as one of the most important ecological factors heavily fluctuates in our inland water environments (17).Therefore, it plays a substantial role in abundance and distribution of aquatic organisms (1).Results indicate that the concentration of salinity in winter was much less than those in summer.This may relate to direct correlation with temperature and increased evaporation in addition to decline in water quantities supplied by Tigris and Euphrates.Many reasons may affect current velocity namely wind movement, as is wind in addition to the variation in the temperature distribution and abruptly change at atmospheric pressure and rain showers (23).The importance of current velocity may determined as a complement to the quality of water and assist to provide a source of food and spawning locations and pathways for fish migration (24).Results were evident that there are monthly changes in current speed.
pH is vital environmental character in aquatic habitats.Values at alkaline direction are more preferred by aquatic organisms.However, all values encountered in the present work were in this level, but the relative decline in values in summer months may be attributed to decomposition of organic matters and release of carbon dioxide (22) winter more recognized with increase in pH which may be due to the role of aquatic plants and phytoplankton in imposing low rates of photosynthesis leading to shortage in CO 2 consumption.
Results showed that there are seasonal changes in algae composition, as it was noted that there are two peaks in spring and autumn.This may be attributed to the prevailing appropriate temperature and reasonable light penetration in addition to amble nutrients content.Environmental factors in particular water temperature has great impact in stimulating the bacteria to decompose organic matters thereby increasing nutrients followed by algal growth and reproduction (9); (32) and (23).

Figure ( 1 )Figure ( 2 )
Figure (1) Aerial map showing the sampling locations in the study area.

Table 1 .
Continued.Hussein, S. A.(2009).Causes of water scarcity, its high salinity, the sources of abuse of inland waters and their environmental and health consequences along with proposals to address the future.Submitted to the workshop on the impact of water scarcity in Basrah province on the natural environment and social development.Held for the period from 18-19/ November, 2009.