Turbidity and kelp holdfast amphipoda. I. Wales and S. W. England

Abstract

Analyses are given of a collection of over 65,000 amphipods derived from kelp holdfasts surveyed around Wales and S.W. England. Faunal affinity is predominantly biased latitudinally, warmwater elements being confined to the extreme southwest. Total amphipod density is related to holdfast weight. There are no significant differences in amphipod density with differences in wave exposure or turbidity. Standardized density is, however, higher in west coast than in east coast holdfasts. Diversity is lower in turbid waters due to the increased dominance of a few species. The distribution, population structure, and fecundity of the previously implicated turbidity-susceptible species, Lembos websteri Bate and Corophium bonnellii Milne Edwards are examined in the light of new ethological information. Supporting and conflicting data are examined and mechanisms are suggested to show how suspended inorganic particles could be directly detrimental to both species. In addition, indirect effects involving climatic fluctuation and competitive interactions, particularly with C. sextonae Crawford emend. Hurley and Jassa falcata (Montagu) cannot be excluded.