The health of coral reefs has been decreasing globally due to acute and diffuse anthropogenic impacts. Historically corals have persisted through periods of adverse conditions for coral growth via evolutionary selective processes, making successful sexual reproduction paramount to the future of coral reefs. Little is known about sexual reproduction of Caribbean corals at high latitude, specifically in southeast Florida on the northern most extension of the Florida reef tract. Here, a comprehensive histological analysis of gametogenesis, spawning, and size of sexual maturity is provided for Siderastrea siderea at 26°N (Broward County, Florida, USA), with accompanying analysis of fecundity variation from the upper Florida Keys (25"N) through Martin County Florida (27°N). Histological analysis of tissue samples in combination with lunar, tidal, and temperature cues suggest primary spawning occurs following the new moon of October. Massive and rapid post-spawning oocyte resorption was observed and characterized across both years indicating that spawning is generally incomplete in the study area. Histological observations suggest that size at sexual maturity in a nearshore, high sediment environment may be >20cm2 which is considerably smaller than previously reported. Fecundity decreased by 85% from 25°N to 27°N. Changes in fecundity were not attributed to significant differences in oocyte quantity between regions but to differences in oocyte volume which decreased by 65% from 25°N to 27°N. Drastic decreases in fecundity observed over a relatively small geospatial scale have important implications for regional population structure and connectivity and should prompt a further, multi-species, investigation.