23 research outputs found
Coral spawning in the Gulf of Oman and relationship to latitudinal variation in spawning season in the northwest Indian Ocean
Despite a wealth of information on sexual reproduction in scleractinian corals, there are regional gaps in reproductive records. In the Gulf of the Oman in the Arabian Sea, reproductive timing was assessed in four common species of broadcast spawning corals using field surveys of gamete maturity and aquarium observations of spawning activity. The appearance of mature gametes within the same month for Acropora downingi, A. hemprichii, Cyphastrea microphthalma and Platygyra daedalea (≥ 75% of colonies, n = 848) indicated a synchronous and multi-specific spawning season. Based on gamete disappearance and direct observations, spawning predominantly occurred during April in 2013 (75- 100% of colonies) and May in 2014 (77-94% of colonies). The difference in spawning months between survey years was most likely explained by sea temperature and the timing of lunar cycles during late-stage gametogenesis. These reproductive records are consistent with a latitudinal gradient in peak broadcast spawning activity at reefs in the northwestern Indian Ocean which occurs early in the year at low latitudes (January to March) and progressively later in the year at mid (March to May) and high (June to September) latitudes
Environmental characteristics of the United Arab Emirates waters along the Arabian Gulf : Hydrographical survey and nutrient salts
225-232<span style="font-size:14.0pt;line-height:
115%;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" color:black;mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:="" hi"="" lang="EN-IN">Surface and bottom seawater samples were collected monthly from October 1993
to September 1994 at twenty-four stations. The levels of different parameters
were in the range of : temperature (16.90-34.60°C), salinity (35.2-44.0×10-3
),transparency (0.5- 13.0 m), pH (7.91-8.60), dissolved oxygen
(3.63-9.02 mg/l), biological oxygen demand (0.05-6.11mg/l), ammonia (ND-
15.32μg-at N/l), nitrite (ND-5.18μg-at N/l), nitrate (0.07-14.32μg-at N/l),
phosphate (0.01- 10.2 μg-at P/l), and silicate (0.4-26.5μg-at Si/l). The
patterns of distribution indicated insignificant differences between surface
and bottom layers due to the shallowness of the area, turbulence of the water
column, and effects of sewage wastewaters. Water temperatures exhibited their
lowest average value in the winter season and the highest in the summer season.
The lowest averages of salinity, transparency, pH, and dissolved oxygen
were measured in the summer season. Whereas, the highest averages for these
parameters were observed in the winter season. Except for nitrate and
phosphate, insignificant differences between average values of other nutrient
salts in the summer and winter seasons were observed. Nitrate and phosphate
showed lower average values in the summer season compared to the winter season
due to the increase in the rate of uptake by phytoplankton which was more abundant
in the summer season. Horizontal patterns of distributions for hydrographic
parameters revealed only an increase for transparency and a decrease for
biological oxygen demand in a seaward direction. Except for Sharjah creek, no
distinct horizontal patterns of distributions for nutrient salts were observed.
At Sharjah, most of the nutrient salts decreased in a seaward direction due to
the presence of effective sewage pollution sources inside the creek. The atomic
ratio of the elements N: P: Si were similar in Abu-Dhabi, Umm al-Quwain, and
Ras al-Khaimah areas, but with lower values in Sharjah. It is concluded that
the discharge of sewage and industrial wastes has affected the quality of seawater inside some semi-enclosed areas,
especially Sharjah creek, as indicated by the increase in the levels of
biological oxygen demand and the
elevation in the concentrations of the nutrient salts.</span
بعض الخصائص الهيدروكيميائية لمياه دولة الإِمارات العربية المتحدة المطلة على الخليج العربي وخليج عمان
Surface and bottom water samples were collected from the United Arab Emirates waters along the Arabian Gulf and the Gulf of Oman during the period from October 1993 to September 1995. Samples were analyzed for temperature (21.1-33.5oC), salinity (35.86-43.20%), pH (7.94-8.40), transparency (4.5-17.5 m), dissolved oxygen (3.94-8.72 mg/1), ammonia (ND-22.7 ug-at N/l), nitrite (ND-2.16 (ug-at N/l), nitrate (ND-18.12 ug-at N/l), phosphate (0.01-4.22 ug-at P/l), and silicate (0.62-15.38 ug-at Si/1). The levels and distributions of the hydrochemical parameters in the investigated area showed that the Arabian Gulf seawater exhibited higher salinity (1.07 times), and ammonia (1.60 times) compared to the Gulf of Oman waters. Meantime, the Gulf of Oman waters were more transparent (1.30 times), and more oxygenated (1.07 times) . Moreover, seawater at the Gulf of Oman showed a tendency to concentrate nitrite (1.25 times), nitrate (1.72 times), phosphate (1.40 times), and silicate (1.06 times) which reveal relatively oligotrophic conditions in the Arabian Gulf waters.
The Calculated atomic ratios of the elements P:N:Si in seawater of the Arabian Gulf and the Gulf of Oman were, particularly in the Gulf of Oman water, different from Redifield ratio and indicated that inorganic phosphorus was the limiting factor.تمت دراسة التغيرات الفصلية والمكانية لبعض الصفات الهيدروكيميائية مثل دوجة الحرارة - الملوحة - النفاذية - الأس الهيدروجيني - الأكسجين المذاب - الأملاح المغذية ( الأمونيا - النيتريت - النيترات - الفوسفات - السيليكات ) في مياه دولة الإِمارات العربية المتحدة المطلة على الخليج العربي وخليج عمان خلال الفترة من أكتوبر1993 وحتى سبتمبر1995 .
أوضحت الدراسة وجود تغيرات فصلية ومكانية واضحة في معظم الصفات الهيدروكيميائية وخصوصاً درجات الحرارة - الملوحة وبعض الأملاح المغذية .
أوضحت الدراسة أيضاً ارتفاع درجات الملوحة وارتفاع تركيز الأمونيا في مياه الخليج العربي عنها في مياه خليج عمان وبالعكس تميزت مياه خليج عمان بزيادة تركيز الأكسجين المذاب ومعظم الأملاح المغذية مثل النيتريت - النيترات - الفوسفات "السيليكات مما يدل على زيادة إِنتاجية مياه الدولة المطلة على خليج عمان .
أوضحت الدراسة أيضاً أن نسب النيتروجين والفسفور والسيلكون في مياه الدولة بوجه عام اختلفت خصوصاً في منطقة خليج عمان عن النسب العادية ، وقد دلت هذه النسب على أن الفسفور هو الامل المحدد في المنطقة