contained less than 0.1 mg per ml (Fig.13.7a). While the positive relationship
between biomass and predicted metabolism persisted among the communities
with less than 1 mg per ml, there were also communities with very similar total
biomass but different predicted metabolism (Fig.13.7b). That two communities
with equal total biomass have very different levels of metabolism must result
from differences in the size distributions between those communities. Higher
metabolism for a given biomass results if a community contains mostly small
individuals in contrast to communities that contain mostly large individuals.
Across all of the communities, total biomass and predicted metabolism
explained very similar amounts of variation in observed metabolism (measured
by respirometry) (Figs.13.7c & 13.e). They both explained about 45% of the
variation in observed metabolism and were both significant at p¼0.01.
Analyzing on the communities with less than 1 mg per ml revealed different
results. Here, total community biomass had very little explanatory powerTable 13.5Summary of analysis two of the community consequences of body size
on total community biomass. The response variable is total community density.
M¼body mass, S¼species richness, E¼environmental warming treatment,
Ew¼warmed.ANOVA tableDf Sum sq Mean sq F value Pr(>F)
M 1 11.0975 11.097 421.3570 <2.2e16***
S 1 0.0022 0.0022 0.0843 0.773437
E 1 0.2561 0.2561 9.7256 0.003829**
M:S 1 0.1847 0.1847 7.0116 0.012466*
M:E 1 0.1634 0.1634 6.2034 0.018131*
S:E 1 0.0432 0.0432 1.6387 0.209700
M:S:E 1 0.2138 0.2138 8.1185 0.007601**
Residuals 32 0.8428 0.0263
Coefficients
Estimate Std. error t value Pr(>|t|)
(Intercept) 0.53928 1.76310 0.306 0.761685
M 0.91835 0.2545 3.608 0.001039**
S 0.13457 0.24425 0.551 0.585502
Ew 10.74478 2.88291 3.727 0.000749***
M:S 0.02363 0.03724 0.635 0.530111
M:Ew 1.44316 0.39465 3.657 0.000909***
S:Ew 1.03664 0.35082 2.955 0.005827**
M:S:Ew 0.14428 0.05064 2.849 0.007601**258 O.L. PETCHEYET AL.