FACTORS INFLUENCING THE DISTRIBUTION OF NEREID POLYCHAETES - THE SULFIDE ASPECT

A study of the spatial distribution of 3 species of nereid polychaetes (Nereis virens, N. diversicolor and N. succinea) was conducted during fall 1991 in Danish estuarine waters. Results from field data (Kerteminde Fjord/Kertinge Nor and Norsminde Fjord) suggested that pore water sulfide (HS-) acts on the distribution of these species. N. virens was confined to low-sulfidic areas (< 50 muM) while N. succinea was found in high-sulfidic sediments (from 50 to 2000 muM). N. diversicolor, on the other hand, showed a broader distribution with respect to pore water sulfide. Complementary tank experiments indicated that all 3 species preferred non-sulfidic sediments in allopatry, whereas N. diversicolor was excluded from the non-sulfidic compartment of tanks in sympatry with each of the other 2 species. Mortality rates indicated that N. virens was the least sulfide-tolerant species whereas the other species showed some sort of adaptation with respect to pore water sulfide. Tank experiments and coexistence coefficients from field data indicated that interspecific competition is an important determinant of nereid distribution patterns, particularly for populations of N. diversicolor. Field data and results from laboratory tank experiments suggest that N. succinea is closely associated with mussel beds.