The Doha index edged down 0.7 percent because of Islamic lender Masraf Al Rayan, which dropped 2.7 percent as its shares no longer carried the 2014 dividend of 1.75 riyals.
Petrochemicals-to-metals conglomerate Industries Qatar, which went ex-dividend a day earlier, was down a further 1.3 percent.
Oil prices, which directly affect the prices of petrochemicals, tumbled 5 percent, their largest drop in a month, late on Monday as speculation of a nuclear deal that could lift sanctions on Iran and boost its oil exports brought worries about high supply back to the market.
However, Abu Dhabi's market edged up 0.4 percent on the back of First Gulf Bank, which jumped 2.0 percent. The lender will pay a dividend of 1.00 dirham per share on Thursday.
But oil and gas firm Dana Gas, whose profit is sensitive to energy prices, dropped 2.2 percent.
Dubai's index edged down 0.3 percent as most stocks declined on very low trading volumes. Builder Arabtec, which has not yet commented on media reports saying its $40 billion Egyptian project has stalled again, fell 1.0 percent.
Oman's market was flat and Kuwait inched up 0.1 percent, but Kuwait Food Co (Americana) dropped 3.4 percent after posting a 28 percent decrease in fourth-quarter net profit on Monday and proposing a flat annual dividend.