Ecological Characterization of the Benthic Community of Lake Pontchartrain, Louisiana

摘要

We have examined and documented several changes in the benthic community structure of Lake Pontchartrain. The change from dominance by large Rangia cuneata to dominance by very small hydrobiid gastropods, for instance, has occurred since the last large-scale study was done 25 years ago. We have also discussed changes in benthic community function in Lake Pontchartrain. We have characterized the lake as a functioning as a one-resource system, with the filter-feeding zooplankton, the deposit-feeding benthos, and suspension-feeding benthos all feeding together at the sediment-water interface. This loss of distinction between feeding types reflects the loss of specialized species and the dominance of the generalist or the broad-niched species. This trend appears to be a response to lower levels of primary production. Several factors appear to be involved in the long-term changes we have documented. Increasing levels of pollution in the lake and the increasing destabilization of the sediments by dredging apparently have acted together to reduce primary production and to diminish the number of species and abundance of the zooplankton and the benthos. Changes in dominance in the nekton appear to be related to the same causes. The only species remaining in the lake in abundance are those known to be tolerant to pollution stress, to the degree that some are considered pollution indicator species.