Changes in sediment texture may inhibit the recovery of Hexagenia spp. in Saginaw Bay, Lake Huron

Session: Imperiled Species in the Great Lakes Basin: Identifying Threats and Restoring Populations (1)

Heather Siersma, Wayne State University, [email protected]
Donna Kashian, Wayne State University, [email protected]

Abstract

Multiple anthropogenic disturbances to the Laurentian Great Lakes have detrimentally affected benthic habitats and biota, including Saginaw Bay Hexagenia, extirpated c1960. Remediation efforts have not facilitated bay Hexagenia recovery as of 2012. Bay sediment texture map comparisons (1970s v 2012) suggest suitable Hexagenia habitat has decreased, potentially limiting species recovery. Therefore, we investigated the effects of natural bay and reference site sediments plus sediments constructed to texturally match them on Hexagenia growth, survival, and adult emergence.  Hexagenia nymphs were reared in five 60d bioassays (5 replicates/treatment): bioassay 1 comprised eight sediment treatments constructed of 28%-98% sand in 10% increments; bioassays 2-5 each comprised seven treatments of reference site, bay, and constructed sediments plus several manipulations to make each texturally mimic the others. Chi-square testing revealed significant (p<0.05) differences in: survival across a %sand gradient; both survival and adult emergence from sediments constructed to have bay v reference site texture; and survival and emergence between bay sediments and those constructed to only texturally match bay sediments. No growth differences were found, but data analysis is incomplete.  These results suggest that current Saginaw Bay sediment texture can support Hexagenia development and natural conditions combined with texture may be limiting bay Hexagenia recovery.