First record of Ebria tripartita (Schumann) Lemmermann, 1899 from south of the Caspian Sea

 [Report and Opinion]

First record of Ebria tripartita (Schumann) Lemmermann, 1899 from south of the Caspian Sea

F. Jafari¹*, Z. Ramezanpour², M. Sattari¹

1. Dept. of Fisheries, Faculty of Natural Resources, University of Guilan, Sowmeh Sara, Iran.

2. Dept. of Ecology, International Sturgeon Research Institute, Rasht, Iran.

* Corresponding author’s E-mail: Jafari_fateme63@yahoo.com

ABSTRACT

Ebria tripartita (Schumann) Lemmermann, 1899, a non-photosynthetic flagellate was identified from the southern coast of the Caspian Sea in December 2012. Water temperature at the sampling time was 10 ºC.  The abundance of total phytoplankton cells was 3 × 10⁶ Cells.l^-1, while E. tripartita with 2 × 10 ³ Cells. l^-1 included 0.75% of phytoplankton community. Water quality parameters were recorded when species was observed. The average concentration of nitrate, phosphate and silicate were 0.7, 0.1 and 1.8 mg.l^-1 respectively.

INTRODUCTION

Ebria tripartita (Schumann) Lemmermann, 1899 presents in coastal planktonic communities overall the world (Horner, 2002; Ikavalko, 1998; Throndsen, 1997; Throndsen et al., 2003; Tong et al., 1998; Vors, 1992) but it is usually seen at low  cell concentration. It  belongs to Ebriid family locating  in Rhizaria groups of Eukaryotes (Chantangsi  et al., 2010). The ebridian flagellates are a small group of marine microplankton with a long fossil record. The first fossils recognized to this group are Cretaceous in age and the biodiversity maximum for ebridian genera was recorded in the Miocene (Loeblich et al., 1968; Tappan, 1980).  The fossils of this species are applied as important proxies for determining geological ages of marine sediments (Onodera et al., in press). Although there are reports of other species of this family, E. tripartita and Hermesium adriaticum Zacharias, 1906 especially have been recognized (Hargraves, 2002). Desired temperature is expressed different in available papers, since it has been reported in some papers in cold seasons and others in warm seasons of year (Rhodes & Gibson, 1981; Bizsel & Cirik, 2002; Suikkanen et al., 2007). It is paleontogically expressed that E. tripartita lived in warm water at the Quaternary (Locker, 1995).  It locates  in heterotrophic group and on the top of the microbial food web (Uitto et al., 1997; Rychert, 2013). Ebriids have two slightly subapically unequal flagella and nucleus with condensed chromosomes during interphase. They do not have external cell wall but internal silica skeleton is composed of branching or fenestrated rods (Hargraves, 2002; Patterson, 1999). Ebria cells are phagotrophic and range  from 25 to 40 µm in length. Reproduction is unknown. The name of taxon comes from the Latin word ebrius, which means “drunken” and refers to their distinctive swimming mode. Ebriids are ecologically interest because they are herbivorous grazers (Uitto et al., 1997, Chitchai et al., 2010) that occasionally reach high cell concentration (Hargraves & Miller, 1974).  E. tripartita feeds on phytoplankton, especially on diatoms and also on dinoflagellates (Jin et al., 2011, Hargraves, 2002; Taylor, 1990). The details of the feeding process are still unknown and the involvement of pseudopodia has not been definitively recognized (Hargraves, 2002; Taylor, 1990). However, the capacity to produce pseudopodia has been indicated in the literature (Patterson, 1999). In addition, a species that has the ability to swallow up diatom cells needs an ingestion mechanism and specialized cell structures. Although a distinct mouth would be one option, there is no structural data that support this theory. Hence, the hypothesis of pseudopodia in feeding is much more likely (Taylor, 1990). Despite the ecological significance of the group, research on E. tripartitais scarce and nearly limited to taxonomic and stratigraphic accounts. There are a few reasons for this lack of knowledge. First, it can not be cultivated in vitro and the second is relatively low cell concentrations in coastal water (Hoppenrath & Leander, 2006).

MATERIALS AND METHODS

The study area has located at southwestern coast of the Caspian Sea. Six stations were selected in Guilan province  including Chaboksar, Sefidrood estuary, Amirbekandeh , Dehkadeh saheli  and  Sefidkenar adjacent to Anzali and Talesh Cities at '33 ˚55, 49º 56´, '44˚49, '30˚49, '21˚49 and 48º 55´ latitudes respectively. Sampling was performed monthly in summer and autumn 2012 (from July to December).

Temperature, nitrate, phosphate and silicate were measured at each station.  Nitrate, phosphate and silicate concentrations were measured using spectrophotometer (BR500 made in PERKINELMER Company. Massachusetts. USA). Phytoplankton species were identified using light microscope (BX51 OLYMPUS) with 200X and 400X magnification. Phytoplankton samples were collected by bottles and were fixed in %2 formalin.

RESULTS

E. tripartite is unicellular, without pigment, and with two flagella. This species’ internal siliceous skeleton is surrounded by cytoplasmic structures. It was observed at all stations except Sefidrood estuary. The cell concentration of E. tripartita was 2×10 ³ Cells.l^-1 in the coastal waters of the Caspian Sea. The relative abundance of E. tripartita was 0.75%.  At the same time, Diatoms were dominant group; Chaetoceros sp. and Exvuiaella cordata were the species which had the highest abundance in coastal phytoplankton community.  In the present study, E. tripartite density showed no significant correlation with nitrate, phosphate and silicate concentrations, but was inversely correlated with temperature. Table 1 shows the water quality parameters associated with the presence and abundance of E. tripartita.

DISCUSSION

Southwestern coast of the Caspian Sea is located in the temperate zone and, this area has become more and more eutrophic since the early 1980s (Salmanov, 1999; CEP., 2006; Stolberg et al., 2006). E. tripartita was identified in this area for the first time. In the other studies, chrysophytes had not been reported from the southern part of the Caspian Sea (Bagheri et al., 2011, 2012a, 2012b; Ganjian et al., 2010; Tahami et al., 2012; Nasrollahzadeh et al., 2008)  but  reported  from central and northern part of the Sea (Kideys et al., 2005). The salinity range is 12 - 13.5 ppt in the southern part (Bagheri et al., 2012a)  where E. tripartita was observed .  It was also observed in 39 ppt in Izmir Gulf of Aegean Sea (Bizsel & Cirik, 2002) and in 14.4 - 23.2 ppt in Chesapeake Gulf of America (Rhodes & Gibson, 1981). Despite the wide temperature range (4 - 29.5ºC) stated by Rhodes and Gibson (1981), E. tripartitawas only observed at low temperature (10ºC) in the southwestern shore of the Caspian Sea. In a study on the variations of phytoplankton community in the northern part of the Baltic Sea, E. tripartita was observed when temperature and DIN concentration was low (Suikkanen et al., 2007). In Izmir Gulf this species was approximately observed all year except in January 1998 (Bizsel & Cirik, 2002). In the present study E. tripartita cell concentration was correlated with water temperature but it was not correlated with nitrate, phosphate and silicate concentrations. At the time of presence of E. tripartita, concentration ranges of nitrate, phosphate and silicate were 0.46 - 1.57 mg.l^-1, 0.001 - 0.2 mg.l^-1 and 0.001 - 5.51 mg.l^-1 respectively. 

Concentration ranges of nitrate and phosphate were 0.023 - 0.5 mg.l^-1 and 0.05 - 6.5 mg.l^-1 respectively in Gulf Izmir when this species was observed (Bizsel & Cirik, 2002). Based on the present study, concentration of nutrients has increased in comparison with previous studies in the study area (Bagheri et al. 2011, 2012a, 2012b). Following eutrophication, diatoms increased in the study area. Since they are main food source of this species, E. tripartita can be seen along with the increase in diatoms (Ellegaard et al., 2007; Korhola & Gronlund 1999).

Abundance of E. tripartita was very low. Low abundance of this species may be due to little competition (or no competition) to the other species in eutrophication condition (Ellegaard et al., 2007; Korhola & Gronlund 1999). In an investigation on the sediment of northern Baltic Sea, E. tripartita was  found  on the top of sediments (0.5 - 1 cm upper level) when there has been an increase in nutrients. This increase was exactly observed in the area where the agricultural, industrial and municipal wastes flow into the Sea (Puskaric et al., 1990).

On the one hand, E. tripartita was observed in low temperature and high nutrients concentration and on the other hand, they feed  on nanoplanktons (especially diatoms) which increase in eutrophic conditions, it is expected to be  found in eutrophic conditions. Since this is the first report on Iranian coast of the Caspian Sea, its presence could be related to increased nutrients.

Fig.1. A-E. Light micrographs of E. tripartita from plankton samples of English Bay, Vancover (from Hoppenrath & Leander, 2006). Note the nucleus (arrow) with its granular appearance. F.  E. tripartita flagellum. G. Silicaceous skeleton of Ebria (Rhodes & Gibson, 1981). H-I.  E. tripartitafossil(Korhola & Gronlund 1999). J-K. Light micrographs of E. tripartita isolated from the Caspian Sea plankton samples in the present study.

Table 1. Water quality parameters associated with the presence and abundance of E. tripartita in December 2012.