| Autor: |
Xu Y; Key Laboratory of Environment Change and Resources Use in Beibu Gulf, Ministry of Education, Guangxi Teachers Education University, Nanning, Guangxi, China.; School of Geographical and Oceanographic Sciences, Nanjing University, Nanjing, Jiangsu, China.; Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, United States of America., Richlen ML; Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, United States of America., Liefer JD; Department of Geography and Environment, Mount Allison University, Sackville, New Brunswick, Canada., Robertson A; Department of Marine Sciences, University of South Alabama and Dauphin Island Sea Lab, Dauphin Island, Alabama, United States of America., Kulis D; Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, United States of America., Smith TB; Center for Marine and Environmental Studies, University of the Virgin Islands, St. Thomas, US Virgin Islands, United States of America., Parsons ML; Coastal Watershed Institute, Florida Gulf Coast University, Fort Myers, Florida, United States of America., Anderson DM; Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, United States of America. |
| Abstrakt: |
Benthic dinoflagellates in the genus Gambierdiscus produce the ciguatoxin precursors responsible for the occurrence of ciguatera toxicity. The prevalence of ciguatera toxins in fish has been linked to the presence and distribution of toxin-producing species in coral reef ecosystems, which is largely determined by the presence of suitable benthic habitat and environmental conditions favorable for growth. Here using single factor experiments, we examined the effects of salinity, irradiance, and temperature on growth of 17 strains of Gambierdiscus representing eight species/phylotypes (G. belizeanus, G. caribaeus, G. carolinianus, G. carpenteri, G. pacificus, G. silvae, Gambierdiscus sp. type 4-5), most of which were established from either Marakei Island, Republic of Kiribati, or St. Thomas, United States Virgin Island (USVI). Comparable to prior studies, growth rates fell within the range of 0-0.48 divisions day(-1). In the salinity and temperature studies, Gambierdiscus responded in a near Gaussian, non-linear manner typical for such studies, with optimal and suboptimal growth occurring in the range of salinities of 25 and 45 and 21.0 and 32.5°C. In the irradiance experiment, no mortality was observed; however, growth rates at 55 μmol photons · m(-2) · s(-1) were lower than those at 110-400 μmol photons · m(-2) · s(-1). At the extremes of the environmental conditions tested, growth rates were highly variable, evidenced by large coefficients of variability. However, significant differences in intraspecific growth rates were typically found only at optimal or near-optimal growth conditions. Polynomial regression analyses showed that maximum growth occurred at salinity and temperature levels of 30.1-38.5 and 23.8-29.2°C, respectively. Gambierdiscus growth patterns varied among species, and within individual species: G. belizeanus, G. caribaeus, G. carpenteri, and G. pacificus generally exhibited a wider range of tolerance to environmental conditions, which may explain their broad geographic distribution. In contrast, G. silvae and Gambierdiscus sp. types 4-5 all displayed a comparatively narrow range of tolerance to temperature, salinity, and irradiance. |
