Spatial and temporal distribution of freshwater sponges in Connecticut lakes based upon analysis of siliceous spicules in dated sediment cores

A survey of 28 Connecticut water bodies for spicular remainsoffreshwater sponges preserved in lacustrine sediments revealed14species representing 10 genera. Sediments were examined atfivelevels (ca 1991, ca 1970, ca 1934, ca 1890, ca 1875)todocument changes in species composition, distribution, andabundance. Five species were recorded statewide in all fivegeologic regions: Spongilla lacustris, Heteromeyeniatubisperma, Anheteromeyenia ryderi, Eunapius fragilis, andEphydatia muelleri. Spongilla lacustris was the mostcommonand widely distributed species. Factors that may havecontributedto the observed distribution of the spongillids in Connecticutareregional differences in lake water chemistries, individualspeciestolerances, and differences in extent of dispersal of variousspecies. Most of the more abundant species are widelydistributedwith respect to water quality parameters. Anheteromeyeniaargyrosperma, Duosclera mackayi and Trochospongillapennsylvanica appear to be restricted to waters exhibitingthelower ranges for conductivity, alkalinity and calcium content.Ingeneral, a greater number of spicules was found in bottomsedimentsof the surveyed lakes as compared with the surface sediments.Oftenthis was correlated with increased sediment accumulation ratesinmore recent periods. When this fact is taken into account, itappears that populations of a number of sponge species haveremained relatively constant in many of the lakes over thepastcentury. However, in some lakes exhibiting lower or onlyslightlyhigher sediment accumulation rates at the surface, fewerspiculeswere also found in more recent sediments, suggesting an actualdecline in sponge population sizes. Changes in abundance overthelast 100 years may be related to changes in land use practicesinsurrounding watersheds and the associated changes in waterchemistries.