Environmental conditions of two Red Sea coastal lagoons in Jeddah : 2-Nutrients

Abstract EN

Arbaeen and Reayat-Alshabab are two silled-fjord like lagoons (in Jeddah), each is occupied by two main water layers, one (of thickness 2 m) lies above the sills, it is a Red Seu water superfic ially mixes wiih non-saline water discharged from Jeddah sewage treatment plants.

The other is, in beneath, dammed behind the sills and is euxinic, dense and hypersaline water.

Now, study of the nutrients PO.j _ 5i04 , Nfl4, NO} and N01 in these water layers reveal their enrichments with P04, SiO.j, and NH4• with a noticeable decrease and increase in conccnrmrion with depth in rhc upper and lower layers, respectively .

Also, it reveals that salinity is negatively and positively correlated with the enriched nutrients in the upper and lower layers.

respectively.

refleeting their different sources, Nitrate and NO} are depleted in the upper layer and practically undetectable in the euxinic lower layer.

Their depletion and at the same time domiuancy of the reduced NH4 in the upper layer refers to occurrence of denitrification at rate exceeding rha: of nitrific ation.

Annually.

the lagoons are contributing - 32, 5 and 108 tons of P, Si and N, respectively to the Red Sea