MALFORMATIONS IN EMBRYOS OF THE DEPOSIT-FEEDING AMPHIPOD MONOPOREIA-AFFINIS IN THE BALTIC SEA

The embryonic development of the deposit-feeding Baltic amphipod Monop oreia affinis (Lindstrom) was studied from fertilization to hatching. Severe types of aberrant embryonic development are described and the n ormal variation of the aberrations is estimated. Between 2 and 6% malf ormed, 0 and 5% undifferentiated and 0 and 6% dead eggs and embryos we re observed at different sites in the coastal area of the northern Bal tic proper and the Bothnian Sea without local contaminant discharges. The embryonic development of M. affinis was described to facilitate th e use of the embryo Variables in field studies of sediment toxicity. T he merits of the different embryo variables as biomarkers in effect mo nitoring were evaluated. Gravid females were sampled in the receiving waters of 2 different types of pulp mills and an aluminum smeltery. Fe cundity (eggs per female) and frequency of malformed, enlarged, undiff erentiated and dead embryos per female were determined. Frequency of m alformed embryos was higher at industrially affected stations as compa red to reference areas (p < 0.0001, p < 0.0001. and p = 0.003 respecti vely). The highest frequencies (15.3%) were recorded close to the alum inum smeltery. In reference areas the frequency varied between 1.5 and 4.9. The number of enlarged embryos with oedema was higher near the p ulp mills (p = 0.03, p > 0.0001), particularly the pulp mill with a bl eaching stage, where 25 to 40% embryos per female were affected. Backg round frequencies of enlarged embryos (0.7 to 3.5%) were observed outs ide the aluminum smeltery. Undifferentiated eggs and dead eggs did not correlate to the exposure situation, suggesting these variables are o f limited value in effect monitoring of xenobiotics. The frequency of malformed embryos was increased also when fecundity, reproduction succ ess and developmental stage of embryos were unaffected. Thus, the vari able is suggested to be particularly toxicant-sensitive and by analysi ng the number of malformed embryos of M. affinis an early warning of a ffected populations could be provided.