Tolerance of the Baltic amphipod Monoporeia affinis to hypoxia, anoxia andhydrogen sulfide

Tolerance of different levels of hypoxia and hydrogen sulfide was tested fo r the amphipod Monoporeia affinis. M. affinis was exposed to 6.7 kPa and <0 .2 kPa oxygen tension and 25 mu M and 50 mu M sulfide. The tolerance of M. affinis to moderate hypoxia (6.7 kPa oxygen) was relatively good as only 3. 3 +/- 1.7% of the animals were dead after 120h of exposure. Tn severe hypox ia (<0.2 kPa oxygen) the LT50 Value was 91 +/- 25.7h which is higher than p reviously found for M. affinis. Survival of M. affinis significantly decrea sed when sulfide was added. An LT50 of 14.2 +/- 1.3h for 25 mu M sulfide ex posure with 1.1 kPa oxygen did not change (LT50=13.5 +/- 2.0h) significantl y when no oxygen was available. Consequently, IM. affinis can be classified as a species that is not tolerant of sulfide, and being one of the primary food sources for fish and invertebrates in the northern Baltic Sea its low tolerance gives further evidence on the detrimental effects of severe oxyg en deficiency and hydrogen sulfide.