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Diel Vertical Migration of Peridiniopsis Niei, Liu Et Al., a New Species of Dinoflagellates in an Eutrophic Bay of Three-Gorge R

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Diel Vertical Migration of Peridiniopsis Niei, Liu Et Al., a New Species of Dinoflagellates in an Eutrophic Bay of Three-Gorge R View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Institute of Hydrobiology, Chinese Academy Of Sciences Aquat Ecol (2010) 44:387–395 DOI 10.1007/s10452-009-9298-8 Diel vertical migration of Peridiniopsis niei, Liu et al., a new species of dinoflagellates in an eutrophic bay of Three-Gorge Reservoir, China Yaoyang Xu • Qinghua Cai • Lan Wang • Linghui Kong • Daofeng Li Received: 9 January 2009 / Accepted: 9 November 2009 / Published online: 27 November 2009 Ó Springer Science+Business Media B.V. 2009 Abstract In spring, a typical dinoflagellate (Peridini- Introduction opsis niei Liu et al.) constitutes most of the phytoplankton biomass in most of eutrophic bay of Three-Gorge Dinoflagellates are a diverse group of unicellular or Reservoir (TGR, China). There are few field observa- colonial eukaryotic microorganisms, which are char- tions on vertical migration of the members of the genus acterized by regulated motility combined with an Peridiniopsis. We studied diel vertical migration of the ability to photosynthesize (Clegg et al. 2007). As an new species (Peridiniopsis niei) at sampling stations A important functional component of the phytoplankton and B in an eutrophic bay (Xiangxi Bay) of TGR during community, most of the dinoflagellates are capable of both day and night in March 2007. The present study using their weak swimming abilities to perform diel suggests that vertical migration by Peridiniopsis niei is vertical migration (DVM), which is a widespread similar in nature to the migration patterns observed for phenomenon in both marine and freshwater habitats, other dinoflagellates. Solar irradiance incident was an and it has been the focus of most migration studies important factor regulating the ascent and descent of (Salonen and Rosenberg 2000; Beckmann and Hense Peridiniopsis niei. The vertical descent of Peridiniop- 2004; Townsend et al. 2005; Doblin et al. 2006; sis niei during nighttime was restricted when the Yamamoto and Nakahara 2006). In general, DVM thermocline (Temperature gradient [1°Cm-1) was behavior is known to facilitate the cells acquiring present in the station B. both high light and high nutrient levels, by maintain- ing near surface distributions by day and near Keywords Diel vertical migration Á pycnocline and nutricline depths by night (Ralston Dinoflagellate Á Thermocline Á Incident solar et al. 2007; Ross and Sharples 2008). Advantages of radiation Á Nutrient Á Stratification DVM behavior can be used to explain the dominance of dinoflagellates in marine and freshwater ecosystem (Salonen and Rosenberg 2000; Clegg et al. 2004; Y. Xu Á Q. Cai (&) Á L. Wang Á L. Kong Á D. Li Townsend et al. 2005; Doblin et al. 2006). Most of State Key Laboratory of Freshwater Ecology and dinoflagellates with high light and high nutrient Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, 430072 Wuhan, affinities frequently become the principal contributor People’s Republic of China to harmful algal blooms and red tides (Erga et al. e-mail: [email protected] 2003; Bearon et al. 2006). Knowledge of DVM is of fundamental importance in explaining dinoflagellates Y. Xu Á L. Wang Á L. Kong Graduate University of Chinese Academy of Sciences, bloom in marine and freshwater habitats and under- 100049 Beijing, People’s Republic of China standing the ecology of dinoflagellates. 123 388 Aquat Ecol (2010) 44:387–395 In general, variations in DVM behavior of dino- of TGR was still a fully mixed system, and most of the flagellates have been attributed to a large number of TGR bays may be characterized by well developed driving factors such as light (Kessler et al. 1992; Clegg stratification (Zheng et al. 2006). Surprisingly, phyto- et al. 2003b), temperature stratification(Clegg et al. plankton spring blooms often occurred in most reser- 2003a), chemical gradients (Lee et al. 1999; Clegg voir-bays, but there have been no algal blooms reported et al. 2004; Doblin et al. 2006) and salinity (Erga et al. until now in the main TGR after the reservoir became 2003; Clegg et al. 2007). The relative importance and operational (Cai and Hu 2006). As a new species of interplay of the various factors that can potentially freshwater dinoflagellates from China, Peridiniopsis affect DVM behavior of dinoflagellates show much niei Liu et al. is often found to bloom during spring in variation, because aquatic ecosystems, such as ocean, large numbers and color the water brown in the estuaries, bays, lake and reservoirs are very diverse. reservoir-bays of the Three-Gorges Reservoir (TGR), For example, Erga et al. (2003) concluded that strong China (Cai and Hu 2006; Liu et al. 2008). Theoreti- haloclines in fjords and coastal waters can prevent cally, the typical dinoflagellate Peridiniopsis niei with phytoplankton flagellates (Tetraselmis sp.) in the the characteristic of vegetative free-swimming cells, surface layer from reaching the nutrient-rich deeper should exhibit active vertical movements in water layer during the night and therefore play an important column, but there is no evidence for DVM behavior of regulating role in the bloom dynamics of phytoplank- this species from field observation until now. Interspecies ton. In freshwater ecosystems, temperature is the main differences among dinoflagellates can lead to very governing factor with respect to the density of fresh- different vertical migration strategies and different cell water, and thermocline is the main contributor to the distributions in the water column (Ralston et al. 2007). stratification of these waters. Behavioral response of Field monitoring is thus necessary to understand DVM dinoflagellates to temperature gradient has been dem- behavior of Peridiniopsis niei. onstrated for many phytoplankton flagellates both in Xiangxi Bay can be considered as representative situ and/or in experimental columns (Clegg et al. of most eutrophic bays of the TGR (Cai and Hu 2003a, 2007). The occurrence of dinoflagellates during 2006). Monthly monitoring over 2 years revealed temperature stratification is considered to be a result of mean concentrations of total nitrogen and total their ability to conduct DVM down below the thermo- phosphorus in Xiangxi Bay of 1.29 mg N L-1 and cline to satisfy their nutrient demand, but some studies 0.153 mg P L-1, respectively (Cao et al. 2006). (e g., Doblin et al. 2006) also found that cells of Dinoflagellate bloom frequently occurred during flagellates in nutrient-replete columns showed no warming spring in Xiangxi Bay. The important vertical migration, but they were more dispersed in questions are does Peridiniopsis niei perform DVM the upper layer during the dark compared to the light in the nutrient-rich waters of the bays and does it period. However, the knowledge about these aspects penetrate the thermocline in the dark? In order to gain remains unknown in most of freshwaters in subtropical a preliminary understanding of the ecology of the and tropical regions, especially from China. Obvi- organism, we carried out two field observations on ously, field observation on DVM phenomenon in those vertical distributions of the dominant dinoflagellates waters is not only of local interest, but relevant for the (Peridiniopsis niei) and their controlling factors understanding of DVM behavior of dinoflagellates. during spring of the year 2007 in Xiangxi Bay. The Three-Gorges Reservoir (TGR) located in the main purpose of paper is to firstly present the results mainstream of the Yangtze River (China), is one of of field observations on diel vertical migration of the the largest man-made lakes in the world, with capacity new species (Peridiniopsis niei) and discuss whether of 3.93 9 1010 m3, water level of 175 m, surface area this dinoflagellate perform vertical migrations to the of 1,080 km2 and watershed area of over 1.00 9 deep nutrient reservoir during the dark periods. 106 km2 (Wang et al. 1997; Huang et al. 2006). The reservoir includes forty large reservoir-bays (watershed area of each bay [100 km2), and the surface area of Materials and methods these bays accounts for one-third of the total surface area of the TGR (Cai and Hu 2006; Huang et al. 2006). The field observations were carried out at two sampling Based on the estimated residence time, the mainstream stations (A and B) of Xiangxi Bay (Fig. 1). The water 123 Aquat Ecol (2010) 44:387–395 389 samples for phytoplankton were collected at 2 h The established single-sample index of dispersion intervals during daytime and at 4 h intervals at (Morisita’s index, MI) was chosen to determine disper- nighttime using a 5 L Van Dorn sampler. The samples sion patterns for dinoflagellate population in water from the station A with ca. 8.5 m depth, at 2 m column, as it is independent of both the sample mean intervals in water column, and that from the station B and the total number of organisms found in the sample with ca. 21 m depth at 2 m intervals in upper water (Thackeray et al. 2006). The index was calculated as: layers (0–6 m) and 5 m intervals in deeper water layers X X X X (10–20 m) were taken. The water samples were 2 MI¼n X2 À X X À X preserved in situ with standard Lugol’s solution in i i i i 1.5 L clean plastic bottles. Those samples were where X is the number of individuals in a given concentrated to 30 mL of quantitative subsamples i sampling unit (i), and n is the number of sampling units. using sedimentation method (Zhang and Huang 1991; An index value\1 indicates a uniform distribution, a Huang et al. 1999). The phytoplankton cells were value [1 indicates an aggregated distribution, and a counted in a Fuchs-Rosenthal counting chamber under value = 1 indicates a random distribution (Thackeray an Olympus microscope at 4009 magnification.
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