LISBON, Feb 22 (Reuters) - Portugal's oil and gas company, Galp Energia, on Monday posted a 98% plunge in adjusted fourth-quarter net profit on a steep slump in refining margins and a drop in output due to the impact of the coronavirus pandemic.

Galp suspended production at its largest unit in Sines and its smallest, Matosinhos, in April. It restarted production at both locations in June, but stopped it at Matosinhos in early October to not resume it again.

The company said production in the fourth quarter fell to 122,800 barrels of oil equivalent per day (boepd) on a working interest basis, from 136,900 boepd a year earlier.

The firm's refining margin fell to $1.6 per barrel in the fourth quarter from $3.3 in the same period last year.

Galp's adjusted net profit fell to 3 million euros ($3.64 million) from 157 million a year earlier, according to its statement.

Earnings before interest, taxes, depreciation and amortisation (EBITDA) fell 37% to 410 million euros.

Net profit and EBITDA has been adjusted to reflect changes in the company's stocks of crude. ($1 = 0.8251 euros) (Reporting by Sergio Goncalves Editing by Nathan Allen)