Abstract
The present paper is a contribution to the ecological and biogeographical classification of the
coastal lakes from the Rio Grande do Sul State, Brazil.
The knowledge of the lake origin together with the morphological characteristics of the studies
coastal lakes provide the understanding of ecological and biogeographical relationships. The presented
morphological characteristics have been worked out from own field studies, while the discussion of the
lake origin is a result of a critical literature review.
The coastal lakes can be classified on their morphological structure, in relation to their nutrient
contents and their communities.
The three lake groups are:
1. deep lakes, until 11 m depth
2. medium-deep lakes, with a depth around 3,5 m
3. shallow lakes, maximal depth 1,5 m.
Based on this investigation a new formula for the calculation of the medium-depth is proposed,
different from these of the IBP-Programme. The relation between the maximum and the medium depth
is
z = 0,75 z(max)^0,83
and can be considered as typical for the morphological characteristics of extrem shallow lakes or lagoons.
