July, 1999 
SCAMIT Newsletter 
Vol. 18, No.3 
order of magnitude more slowly in high- 
density treatments. The authors suggest that 
physical or chemical interference is the 
probable cause of the observed differences. 
Resource limitation may also be involved. 
Although particle availability was unaffected, 
the nutrient content of the particles with regard 
to carbon and nitrogen was not evaluated in the 
study. Though causation remains unresolved, 
the results clearly indicate that extrapolations 
of laboratory rate information to field 
bioturbation estimates must take population 
density into account. 
A number of years ago, while preparing a 
proposal to the State of Florida for monitoring 
of coral reef areas, Jerry Bernard asked me to 
provide an iron-clad rationale for use of limited 
funds to monitor the marine environment. 
Much to my surprise and chagrin I could not do 
so, at least to my own satisfaction. The 
question has been rephrased by Karr & Chu 
(1997) to evade the monetary issue and only 
address information need. They argue that 
biological monitoring, with results expressed in 
some easily interpretable index value, is an 
essential underpinning of informed decision 
making. To evaluate the impact and 
advisability of human activities, we need to 
monitor how man’s activity affects our natural 
surroundings. They insist that monitoring 
efforts “should stay focused on human impact”. 
I disagree. I think there is also a real need for 
continued appraisal of natural variability, for 
which continued monitoring of un-impacted 
areas is also required. Either way both the 
“pure” ecological research questions and the 
“applied” risk monitoring efforts are mutually 
informative. The authors’ commentary on why 
we need monitoring provides good and 
thought-provoking reading. 
If we monitor, how much definition in the 
taxonomy is enough? This perennial question 
has been answered differently by different 
authors. Several analyses had suggested that 
identification to family level is sufficient, and 
that additional work to take collected 
specimens to species level is largely wasted. 
This is based on power analyses which show 
that conclusions drawn from samples identified 
to species do not differ significantly from those 
based on samples identified to family. Myers 
(1997) approached the question from a 
different angle in an examination of biological 
diversity at different scales. He found that 
family level diversity showed no predictable 
relationship to species diversity in several 
tropical lagoons. He concluded “at least as far 
as concerns amphipods, there appears to be no 
simple way of assessing biodiversity without 
actually counting species.” And the debate 
continues... 
The isopod species Eurydice truncata is 
reported from a number of areas, including 
California. Macquart-Moulin (1998) provides 
some autecological data on the species from 
the eastern Atlantic. He found the species to 
migrate between the bottom and the surface 
during the night, apparently feeding on living 
neuston, particularly ‘passive’ neuston that 
doesn’t fight back. In this category are things 
like animals caught in the surface meniscus, 
fish eggs and other reproductive propagules. 
Gut fullness declined from inshore to offshore, 
so the individuals at the deep edge of the 
population may be at risk of starvation. 
Recent reviews of the subject have concluded 
that although scavenging is widespread in the 
marine environment, there is no evidence that 
obligate scavengers exist. Kaiser & Moore 
(1999) revisit this question and conclude the 
opposite. They single out the case of a small 
lysianassoid amphipod Orchomene nanus , 
which evidence suggests is a specialized and 
obligate scavenger on crustacean carrion. 
Others have previously described a guild of 
marine large food-fall scavengers, but these are 
not confirmed as being restricted to 
scavenging. It may not matter much what the 
ultimate outcome is, a scavenger is just a 
predator who has the habit of letting his prey 
die before eating it. 
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