Dr. Schiel et al., THE STRUCTURE OF SUBTIDAL ALGAL AND INVERTEBRATE ASSEMBLAGES AT THE CHATHAM ISLANDS, NEW-ZEALAND, Marine Biology, 123(2), 1995, pp. 355-367
We examined the distribution and abundance of organisms on subtidal ro
cky reefs at nine sites around the Chatham Islands, a remote group 780
km east of southern New Zealand. We sampled five depth strata ranging
from 1 to > 16m to identify spatial patterns in the abundance of alga
e and invertebrates and to assess their variation within and among sit
es. This information is used to discuss hypotheses concerning communit
y structure at this remote locality. Several patterns were apparent. T
he immediate subtidal was occupied by the southern bull kelp Durvillae
a spp. A suite of 11 fucalean species were dominant to a depth of 10 m
with an average abundance of 28 m(-2), while one species, Carpophyllu
m flexuosum, occurred mostly in deeper water. Only two laminarian spec
ies of algae were present at the islands. The indigenous Lessonia thol
iformis was abundant at 2.5 to 15 m and was not found in deeper water,
while the giant kelp Macrocystis pyrifera was abundant at two sites i
n 12 to 18 m. The commercially valuable abalone Haliotis iris was extr
emely abundant in shallow water, with an overall mean of 6 m(-2) at 5
m. The sea urchin Evechinus chloroticus was common, but reached high d
ensities only in small (< 25 m(2)) patches. The characteristic urchin-
dominated zones reported in kelp beds world-wide were not seen. There
was considerable site-to-site variation in the occurrence and abundanc
e of individual species. Some differences between sites were associate
d with shelter from swell (e.g. M. pyrifera was found only in sheltere
d sites) and physical habitat (e.g. juvenile H. iris were found only b
eneath boulders inshore), but much of the variation could not be expla
ined by physical or depth-related factors alone. We hypothesize that t
he differences in these kelp bed assemblages compared to mainland New
Zealand are partially due to the high degree of endemism at the Chatha
m Islands. Local variation cannot be explained by herbivory, and is mo
st likely the result of the various life-history characteristics of th
e major habitat-forming species, the large brown algae.