THE RESPONSE OF TIGRIOPUS-CALIFORNICUS TO CHLOROPHYTIC MACROALGAE, INCLUDING CLADOPHORA-TRICHOTOMA KUTZING

The harpacticoid copepod Tigriopus californicus is not observed to mai ntain populations in supralittoral pools containing the alga Cladophor a trichotoma. Laboratory microcosms and field treatments in Barkley So und, British Columbia, Canada were inoculated with T. californicus and monitored seasonally (winter, spring, summer). After 5 days, C. trich otoma microcosms held fewer survivors (18.6 +/- 7.3%) compared to trea tments without vegetation (95.6 +/- 0.1%) or those containing the alga Enteromorpha compressa (93.8 +/- 5.4%), mean +/- SE. Though more diff icult to determine in situ, results from inoculated field sites were s imilar. Copepodite and adult T. californicus were the most adversely a ffected, while the survival of nauplii was generally maintained over 5 -day intervals of observation. Other invertebrates, including littorin es, barnacles and mussels were more abundant in C. trichotoma pools at lower tidal elevations. Although several factors (exposure, nutrient supply, predation) are likely to contribute to the observed 'exclusion ' of T. californicus from pools containing C. trichotoma, the present results additionally suggest the deleterious influence of an unidentif ied chemical exudate from C. trichotoma. The particular susceptibility of mature T. californicus to this exudate precludes the establishment of viable copepod populations in these pools. (C) 1997 Academic Press Limited.