T6 AM Environmental Hypoxia
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in 324-326
(CHE-1117-837976) Hypoxia limits estuarine fish reproduction.
Cheek, A1, Landry, C2, Steele, S2, Sutton, A2, 1 Univ Texas Health Science Center at Houston, School of Public Health, Houston, TX, USA2 Southeastern Louisiana University, Hammond, LA, USA
ABSTRACT- Resident salt marsh fishes tolerate periodic hypoxia, but its effects on reproduction are poorly understood. Our hypothesis is that dissolved oxygen (DO) stress limits reproduction. Our aim was to identify reproductive indicators that consistently respond to hypoxia. We measured two morphological and two biochemical indicators in Gulf killifish (Fundulus grandis): gonadosomatic index (GSI), condition factor (K = 100,000*length/weight3), sex steroid hormone levels, and vitellogenin (VTG) levels. In the laboratory, wild-caught killifish were exposed to normoxia (
7.3 mg/L DO) or chronic hypoxia (1.8 mg/L DO) for one month. Hypoxia suppressed all reproductive parameters in males and all except VTG in females. In the field, F. grandis were collected from normoxic and cyclically hypoxic marsh creeks in Terrebonne Bay, LA; Pensacola Bay, FL; and Weeks Bay, AL in April, July, and November 2002-2004. Indicators varied in temporal sensitivity as demonstrated by the response patterns observed in marshes with different durations of diel DO minima ≤ 2 mg/L. Medium-term (5 weeks) diel hypoxia in a Weeks Bay marsh creek suppressed male and female GSI and steroid hormones, but condition factor and vitellogenin (VTG) were unchanged. Long-term (> 3 mos) diel hypoxia in a Pensacola Bay marsh creek did not alter male or female GSI or steroid hormones, but did reduce condition factor and VTG. Duration of diel hypoxia was unknown for Terrebonne Bay, but was probably between 5 to 12 weeks, based on the pattern of indicator responses. Like Weeks Bay, male GSI and steroid hormones were significantly reduced at the hypoxic Terrebonne Bay site, but condition factor was not. No female indicators were reduced. These morphometric and endocrine indicators respond to DO stress on different time scales, so are potentially useful as retrospective indicators of stress duration and as early warning indicators of reproductive failure.
Key words: hypoxia, reproduction, Fundulus grandis, hormones