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USGS2018

Sperm quality biomarkers complement reproductive and endocrine parameters in investigating environmental contaminants in common carp (Cyprinus carpio) from the Lake Mead National Recreation Area

Lake Mead National Recreational Area (LMNRA) serves as critical habitat for several federally listed species and supplies water for municipal, domestic, and agricultural use in the Southwestern U.S. Contaminant sources and concentrations vary among the sub-basins within LMNRA. To investigate whether exposure to environmental contaminants is associated with alterations in male common carp ( Cyprinus carpio ) gamete quality and endocrine- and reproductive parameters, data were collected among sub-basins over 7 years (1999–2006). Endpoints included sperm quality parameters of motility , viability, mitochondrial membrane potential, count, morphology, and DNA fragmentation; plasma components were vitellogenin (VTG), 17ß-estradiol, 11-keto-testosterone, triiodothyronine, and thyroxine. Fish condition factor, gonadosomatic index, and gonadal histology parameters were also measured. Diminished biomarker effects were noted in 2006, and sub-basin differences were indicated by the irregular occurrences of contaminants and by several associations between chemicals (e.g., polychlorinated biphenyls, hexachlorobenzene , galaxolide, and methyl triclosan) and biomarkers (e.g., plasma thyroxine, sperm motility and DNA fragmentation). By 2006, sex steroid hormone and VTG levels decreased with subsequent reduced endocrine disrupting effects. The sperm quality bioassays developed and applied with carp complemented endocrine and reproductive data, and can be adapted for use with other species.

Lake Mead National Recreation Area↗

USGS2011

Effects of herbivory and flooding on reforestation of baldcypress ( Taxodium distichum [L.]) saplings planted in Caddo Lake, Texas

The effects of herbivory and flooding were examined on survival and growth of planted baldcypress ( Taxodium distichum (L.) Rich.) saplings at three sites in Caddo Lake, TX, over a 4-yr period. There were two flood regimes (shallow periodic and deep continuous), where half of the saplings in each flood regime were protected by tree shelters to prevent herbivory. By the end of the first year, over 80% of saplings survived with half of saplings classified as healthy. By the end of the fourth year, only half of the saplings were alive and one-third were healthy. At all three sites, the combination of no protection and continuous flooding resulted in a significant number of missing saplings. Likewise, most unprotected saplings in periodic flooding were missing by the end of the study. Saplings clipped by herbivores showed about 50% chance of recovery, but many of the sprouts were of poor quality. Protected saplings in tree shelters achieved significantly greater survival and height growth.

Louisiana, Texas↗