118 
On 29 August 1972, a visit was made to 
Prudhoe Bay to collect samples to determine the 
abundance of microfauna (mite, Collembola, 
and enchytraeid worm). These groups consist of 
very small invertebrates which, because of their 
great abundance, collectively comprise the most 
important element of the soil fauna in many 
ecosystems. A limited sample processing capabil- 
ity prevented us from sampling all plots. We 
selected plots which appeared to span the range 
of moisture and vegetation features available at 
Prudhoe Bay. The results, shown in Table 3, are 
contrasted with results of similar sampling on 
nine study plots at Barrow. 
Prudhoe Bay plot 1, a dry Dryas integrifolia 
heath, represents a habitat not found at Barrow; 
we might expect it to have greater faunal affin- 
ities with the Dryas fell-field alpine habitat at 
Eagle Summit in central Alaska. This plot con- 
tained an exceptionally high number of prostig- 
matid mites, but low numbers (in contrast to 
Barrow) of mesostigmatic and cryptostigmatid 
mites, and low numbers of the two major super- 
families of Collembola—the Entomobryidae and 
Poduridae—and of enchytraeid worms. At Bar- 
row mites tend to increase in abundance in 
passing from wetter to drier plots, while Collem- 
bola and Enchytraeidae decline in abundance 
along such a moisture gradient. Thus, in general, 
the Prudhoe Bay plot 1 pattern was predictable 
on the basis of patterns seen at Barrow. 
Prudhoe Bay plot 6 is the wettest plot 
sampled for all three major microfaunal groups. 
It has a very low abundance of both mites and 
Collembola, which seems to reflect the ‘‘poly- 
gon basin syndrome.’’ There are other resem- 
blances: Carex aquatilis is the only vascular 
plant species; there is very little, if any, moss or 
lichen cover; the top 10 or more cm consist of 
saturated sod with very high organic matter 
accumulation. The habitat represented by plot 6 
differs from the typical Barrow polygon basins 
in its greater spatial extent and more robust but 
widely spaced shoots of Carex aquatilis. At 
Barrow the low invertebrate productivity in 
polygon basins is symptomatic of (and perhaps 
causally related to) a general reduction in the 
rate of ecosystem function relative to other 
tundra habitats. Primary productivity, microbial 
activity, and nearly all parameters that have 
been measured reach minimum values in such 
habitats. The existence of analogous, and per- 
haps homologous, habitats occupying greater 
area at Prudhoe Bay suggests that we may be 
addressing a general limiting feature of tundra 
ecosystem function. 
Prudhoe Bay plot 7, a Dryas-graminiform 
mesic mixed heath, is closer to the Barrow dry 
meadows in gross appearance and in microfaunal 
composition. Prostigmatid mites are abundant; 
entomobryid Collembola and Enchytraeidae are 
rather low in abundance. It contained a surpris- 
ing number of podurid Collembola—more than 
were found in eight of the nine Barrow plots. 
In nearly all ecosystems that have been 
studied, the cryptostigmatid mites, especially 
Table 3 
Abundance of major invertebrate groups (number m°2) at 
Barrow (seasonal mean) and Prudhoe Bay. Samples taken 29 August 1972. 
Barrow 
Group Maximum Minimum 
Acarina 
Prostigmata 42,500 4,350 
Mesostigmata 7,080 603 
Cryptostigmata 38,900 1,600 
Total Acarina 
Collembola 
Entomobryidae 172,000 22,400 
Poduridae 33,200 1,150 
Sminthuridae 2,850 0 
Total Collembola 
Enchytraeidae 95,300 11,600 
Prudhoe Bay 
Mean Plot 1 Plot 6 Plot 7 Plots 4/5 
18,000 63,200 1,090 38,700 
3,260 1,090 109 3,710 
20,000 11,900 5,790 4,040 
41,300 76,200 7,000 46,500 
83,000 11,900 2,180 31,100 
8,110 3,820 436 21,400 
1,170 3,490 0 7,750 
92,300 19,200 2,620 60,300 
46,900 15,900 30,900 20,900 32,900 
