Diatom to dinoflagellate shift in the summer phytoplankton community in a bay impacted by nuclear power plant thermal effluent

Abstract

Understanding how nuclear power plant thermal effluents influence the phytoplankton community may provide insights into the potential ecological consequences of global warming. In the present study, long-term trends in the phytoplankton community structure under the influence of nuclear power plant thermal effluent in the subtropical Daya Bay (DYB) in China were investigated in the summer season from 1982 to 2005. Water temperature at the outfall station was significantly higher than in the surrounding water, by as much as 5.6°C, and increased by 6.8°C during the 23 yr study period. The contribution of diatoms and dinoflagellates to the total phytoplankton showed significant correlation with temperature (R 2 > 0.65), negative for diatoms, while positive for dinoflagellates. Although dinoflagellate abundance increased over time at both the outfall and adjacent (control) stations, the increase at the outfall station was much more dramatic and accelerated over time. No clear relationship between the phytoplankton shift and stratification was evident. When water temperature reached 35°C or > 3.7°C above that at the control station, dinoflagellates, such as Ceratium furca, C. fusus, C. trichoceros, Dinophysis caudate and Protoperidinium depressum, grew to prominence, accounting for about 50% of the total phytoplankton abundance. On the contrary, the diatom contribution decreased during the study period, from 82.0% in 1982 to 53.1% in 2005. These results suggest that the rise in temperature caused by power plant thermal discharge has imposed strong influences on the phytoplankton community, favoring dinoflagellates over diatoms, with a remarkable diatom to dinoflagellate shift when temperature increases to a threshold level of 35°C or reaches a threshold differential of 3.7°C relative to the normal ambient temperature in DYB.KEY WORDS: Daya Bay · Nuclear power plant · Thermal effluent · Phytoplankton · Ecological effects Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 424: [75][76][77][78][79][80][81][82][83][84][85] 2011 perature can be indirect, via a decrease in the resupply of nutrients for phytoplankton production resulting from the intensification of water stratification (Margalef 1978, Jones & Gowen 1990. Since phytoplankton have short generation times, they can rapidly respond to temperature increases, and, because they are at the base of the aquatic food web, observations of their responses could provide useful insights into how temperature increases may induce ecosystem changes (Niemi & McDonald 2004). Phytoplankton community structure and abundance have been found to be changing as a result of global warming in many areas (Richardson & Schoeman 2004). For example, the changes in phytoplankton communities have been used as indicators of global warming in the North Sea (Edwards & Richardson 2004) and to monitor nonnative, warm-water species in the Mediterranean and the North Seas (Walther et al. 2002). Because organisms at different trophic levels m...

Phytoplankton Communities Impacted by Thermal Effluents Off Two Coastal Nuclear Power Plants in Subtropical Areas of Northern Taiwan

“…Similarly, Li et al (2011) found that the contribution of diatoms and dinoflagellates to the total phytoplankton population showed significant correlation with temperature, negative for diatoms, while positive for dinoflagellates. In the present study the species composition showed 46 -100% and 58 -71% differences between the outlet and intake of NPP I and NPP II for each season, respectively (calculated by similarity indices, data not shown).…”

“…It was reported that in the outlet area of power plants the seawater temperature increased about 8 -12°C in temperate zones (Bamber 1995) and 6 -10°C in tropical areas (Martínez-Arroyo et al 2000;Poornima et al 2006). In the subtropical Daya Bay in China, Li et al (2011) also suggested that the seawater temperature at the outfall station was significantly higher than in the surrounding water, by as much as 5.6°C, and increased by 6.8°C during the 23-year study period. Although we did not have sufficient temperature data on the NPP outlet, temperature records for NPP II outlet and intake during 2001 -2003 were available from two previous studies.…”

“…Seawater temperature (Jordan et al 1983;Li et al 2011), salinity (Heip et al 1995), and available nutrients (Hecky and Kilham 1988) are important determining factors that structure phytoplankton communities. Moreover, these factors are further affected by local oceanographic characteristics.…”

“…Most recent impact studies on phytoplankton focused mainly on the effects of elevated seawater temperature and residual chlorine on the biomass and productivity Rajadurai et al 2005;Chuang et al 2009). Li et al (2011) reported that the nuclear power plant thermal discharge in the subtropical Daya Bay in China strongly influenced the phytoplankton community. Here, a remarkable shift from diatoms to dinoflagellates was observed when the seawater temperature reached 35°C or > 3.7°C relative to the normal ambient temperature in the study area.…”

“…Through photosynthesis, phytoplankton convert inorganic compounds into organic compounds using solar energy. Phytoplankton communities are sensitive to environmental variations, and long-term or extreme changes in hydrographic conditions may affect their structure (Cottingham 1999;Li et al 2011). Seawater temperature plays a critical role in determining the development and maintenance of phytoplankton communities (Davison 1991).…”