species diversity gradient problem

[Peter Schuchert]

dear collegues
could anyone give me some hints on publications
with studies comparable to my case decribed below?

I have identified all marine hydroids down to 2400 m depth from
a collection made in a defined region. I would now like to
know how species diversity decreases with depth.

However, there are two ways of analysing this, and I don't know
which one is more appropriate.

First, I can define equal depth intervals of 100 m and then
count the species present in the individual intervals. But this will
lead to unequal sample sizes (unequal search effort).

The other solution is to define depth intervals which have
the same number of samples taken. This will lead to rather unequal
intervals.

I assume, that species diversity is both dependent on
search effort and area (= depth interval).

Both approaches give a decreasing species number with depth,
but the first method gives a much more dramatic result.

Any idea?
cheers,
Peter

Dr. Peter Schuchert
Museum of Natural History
Dept. of Invertebrates
1, route de Malagnou
CH-1208 Geneva
Switzerland

fax 0041 22 418 63 01
http://www.ville-ge.ch/musinfo/mhng/index.htm