Pavia, H.; Carr, H.; Åberg, P. (1999). Habitat and feeding preferences of crustacean mesoherbivores inhabiting the brown seaweed Ascophyllum nodosum (L.) Le Jol. and its epiphytic macroalgae. Journal of Experimental Marine Biology and Ecology. 236(1): 15-32.
Habitat and feeding preferences of crustacean mesoherbivores inhabiting the brown seaweed Ascophyllum nodosum (L.) Le Jol. and its epiphytic macroalgae
Journal of Experimental Marine Biology and Ecology
236(1): 15-32
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NeMys doc_id: 10063
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Habitat and feeding preferences of crustacean mesoherbivores inhabiting the brown alga
Ascophyllum nodosum (L.) Le Jol. and its macroepiphytes were examined on the Swedish west
coast. After an initial survey of the epifauna, three species of mesoherbivores, the isopods Idotea
granulosa Rahtke and Jaera albifrons Leach, and the amphipod Gammarus locusta (L.), were
selected for further studies. The role of macroepiphytes in the distribution, abundance and
recolonization rates of the mesoherbivores were investigated in observational and manipulative
field experiments. The results from these experiments were compared with results from multiplechoice
feeding experiments in order to see if the distribution pattern of the mesoherbivores was
related to, or independent of, feeding preferences. The epifauna was dominated in numbers by
gammarid amphipods, but the most abundant crustacean species in terms of biomass was the
isopod I . granulosa. The field experiments showed that macroepiphytes had large effects on the
distribution and abundance of the amphipod G .locusta, with 5–8 times higher mean densities on
A . nodosum plants with macroepiphytes. The effect of macroepiphytes on the abundance of I .
granulosa varied strongly among sites, and for the smaller isopod J .albifrons no effects could be
observed. The manipulative field experiments showed that complete recolonization by the
mesoherbivores on defaunated A .nodosum plants was rapid, occurring on a time-scale of hours or
days. Natural densities on plants with and without macroepiphytes were already found after the
first 24 h for G .locusta, implying that the distribution pattern was the result of habitat selection by
the amphipod, rather than differential predation. Feeding preferences differed among, as well as
within, mesoherbivore species. Large individuals of G . locusta clearly preferred to feed on
macroepiphytes, while large individuals of I . granulosa mostly grazed on meristematic apices of
A .nodosum. Small individuals of both species grazed on both A .nodosum and its macroepiphytes,
with a preference for the epiphytes. For J . albifrons no significant feeding preferences could be
detected. The general conclusion of this study was that macroepiphytes are important as habitat
and food for some of the crustacean mesoherbivores inhabiting A . nodosum, but that large
variations in mesoherbivore–epiphyte interactions occur among and within species. Furthermore,
the results supported the conception that many crustacean mesoherbivores display large mobility.
