246
Andrew CLARKE
Fig. 8.4. Relationship between species diversity of deep-sea prosobranch gastropods and latitude for the North Atlantic and the Norwegian
Sea. Diversity is expressed as the expected number of species E (Sn), with n = 50 individuals (Hurlbert, 1971). Diversity in this group is
negatively correlated with latitude, and the relationship is statistically significant (P < 0.001). Redrawn from Stuart and Rex (1994).
The best known groups are the amphipod and isopod
crustaceans, and echinoderms. These groups have a
high degree of endemism at the species level, but
very low endemism at the genus and family level
(Guryanova, 1970). The diversity is lowest in the
central Arctic basin (Clough et al., 1997), and the
strongest faunal affinities are with the Norwegian
Basin, suggesting continuing invasion from the North
Atlantic.
Fedyakov and Naumov (1989) listed 183 species of
bivalve molluscs, of which 44 species were found in
the Norwegian Basin and 35 species in the central
Arctic Basin. Deep sea bivalves appear to be generally
distributed in all the deep-sea basins, and characteristic
species of the central Arctic Basin are Ledella tamara,
Nucula zophos and Tindaria derjugini. Echinoderms
are typically important members of abyssal faunas,
and key Arctic species are the widespread echinoid
Pourtalesia jeffreysi and the ophiuroid Ophiopyren
striatum (Anisimova, 1989).
Quantitative data on biomass and diversity have been
provided for Arctic deep-sea macrofauna by Kr¨ oncke
(1994, 1998). Samples were collected by a box-core
technique along transects across the Amundsen and
Makarov Basins. Box-core samples are excellent for
quantitative data on species abundance, but the small
areas sampled mean that many large, infrequent taxa
are missed. Thus the species list provided by Kr¨ oncke
(1998) contains many polychaetes and small crustaceans (cumaceans, tanaiids, isopods and amphipods)
but only a single echinoderm (Ophiura robusta).
Biomass values were very low in the deep basins
(0.025 to 3.445 g fresh mass per square metre), but
somewhat higher at the shallower stations. Species
richness was also very low in the deep basins (1 to 11
species in a sample of 0.02 m
2 ) and non-overlapping
k-dominance plots showed clearly that faunal diversity
was lowest in the deepest basins. Comparison was made
difficult, however, by the very low absolute number of
species from the deeper stations.
Are Arctic deep-sea faunas impoverished?
It has long been established for many groups of
terrestrial plants and animals that there is a marked
cline in richness at several taxonomic levels (species,
genera, families) from the tropics to the poles. Following the seminal work of Thorson (1957), it has
also long been assumed that a similar latitudinal cline
in taxonomic diversity exists in the sea. Although the
data are very convincing for some well-studied groups
(notably gastropod and bivalve molluscs), it is not yet
certain that this will prove to be a general feature of
Andrew CLARKE
Fig. 8.4. Relationship between species diversity of deep-sea prosobranch gastropods and latitude for the North Atlantic and the Norwegian
Sea. Diversity is expressed as the expected number of species E (Sn), with n = 50 individuals (Hurlbert, 1971). Diversity in this group is
negatively correlated with latitude, and the relationship is statistically significant (P < 0.001). Redrawn from Stuart and Rex (1994).
The best known groups are the amphipod and isopod
crustaceans, and echinoderms. These groups have a
high degree of endemism at the species level, but
very low endemism at the genus and family level
(Guryanova, 1970). The diversity is lowest in the
central Arctic basin (Clough et al., 1997), and the
strongest faunal affinities are with the Norwegian
Basin, suggesting continuing invasion from the North
Atlantic.
Fedyakov and Naumov (1989) listed 183 species of
bivalve molluscs, of which 44 species were found in
the Norwegian Basin and 35 species in the central
Arctic Basin. Deep sea bivalves appear to be generally
distributed in all the deep-sea basins, and characteristic
species of the central Arctic Basin are Ledella tamara,
Nucula zophos and Tindaria derjugini. Echinoderms
are typically important members of abyssal faunas,
and key Arctic species are the widespread echinoid
Pourtalesia jeffreysi and the ophiuroid Ophiopyren
striatum (Anisimova, 1989).
Quantitative data on biomass and diversity have been
provided for Arctic deep-sea macrofauna by Kr¨ oncke
(1994, 1998). Samples were collected by a box-core
technique along transects across the Amundsen and
Makarov Basins. Box-core samples are excellent for
quantitative data on species abundance, but the small
areas sampled mean that many large, infrequent taxa
are missed. Thus the species list provided by Kr¨ oncke
(1998) contains many polychaetes and small crustaceans (cumaceans, tanaiids, isopods and amphipods)
but only a single echinoderm (Ophiura robusta).
Biomass values were very low in the deep basins
(0.025 to 3.445 g fresh mass per square metre), but
somewhat higher at the shallower stations. Species
richness was also very low in the deep basins (1 to 11
species in a sample of 0.02 m
2 ) and non-overlapping
k-dominance plots showed clearly that faunal diversity
was lowest in the deepest basins. Comparison was made
difficult, however, by the very low absolute number of
species from the deeper stations.
Are Arctic deep-sea faunas impoverished?
It has long been established for many groups of
terrestrial plants and animals that there is a marked
cline in richness at several taxonomic levels (species,
genera, families) from the tropics to the poles. Following the seminal work of Thorson (1957), it has
also long been assumed that a similar latitudinal cline
in taxonomic diversity exists in the sea. Although the
data are very convincing for some well-studied groups
(notably gastropod and bivalve molluscs), it is not yet
certain that this will prove to be a general feature of