{'fraction_non_alphanumeric': 0.04303305249513934, 'fraction_numerical': 0.029941672067401167, 'mean_word_length': 4.953703703703703, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 1, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Surveying Caulerpa (Chlorophyta) species along the shores of the eastern Mediterranean

Caulerpa (Chlorophyta) species inhabiting intertidal and shallow subtidal areas along the Israeli Mediterranean shores (i.e., presence/absence) were surveyed on a seasonal basis from 2007 to 2009. We recorded the presence of three species: C. prolifera, C. mexicana, and C. scalpelliformis. These species were noticeable in autumn and inconspicuous during winter, thus revealing seasonality and population dynamics. There were no indications of well-known invasive species such as Caulerpa racemosa var. cylindracea and Caulerpa taxifolia. This study is the first of a kind that assesses the geographical distribution and seasonality of the genus Caulerpa along the Israeli shores.


Introduction
Caulerpa species are common in both shallow and deep waters of tropical and subtropical seas. They are multinucleated (coenocyte), colonial, modular, and lack cellulose in their cell walls (Silva, 1992). Caulerpa species produce branched axes and attaching rhizoids, and are capable of vegetative reproduction. The genus includes over 75 species worldwide (Famà et al., 2002), with only six described for the Mediterranean Sea, namely, C. prolifera, C. mexicana, C. scalpelliformis, C. ollivieri, C. racemosa [with C. racemosa var. lamourouxii f. requienii, C. racemosa var. turbinata and C. racemosa var. cylindracea -all recognized as separate taxonomical identities (see Verlaque et al., 2003)], and C. taxifolia (Guiry & Guiry, 2011;UNEP, 1999;Einav & Israel, 2007, Table 1). Two of these, C. racemosa var. cylindracea and C. taxifolia, are known to be invasive and have caused great environmental concern in Mediterranean countries during recent years (Boudouresque et al., 1995;Meinesz et al., 1998;Verlaque et al., 2000Verlaque et al., , 2003. The eastern and western basins of the Mediterranean Sea have different thermal regimes. In the eastern Mediterranean Sea, temperatures range from 17 to 30 o C in winter and summer, respectively, and are higher than those in the western basin by about 1.5 o C for both seasons (Kress & Herut, 2001). The eastern Mediterranean basin has a wide, shallow, and sandy continental shelf as well as prominent abrasion intertidal platforms made of limestone and biogenic rocks (Einav & Israel, 2007). In addition, salinities at the eastern basin are higher, with values of 3.9% and 3.6% for the eastern and western basins, respectively (Berman et al., 1984). The eastern Mediterranean Sea is especially susceptible to biological invasions through the Suez Canal. Indeed, most of the approximately 100 known aquatic macrophytes introduced into the Mediterranean Sea have originated from the Indo-Pacific Sea (Galil et al., 1990;Boudouresque & Verlaque, 2002Ribera, 2002;Zenetos et al., 2005;Rilov & Galil, 2009).
Studies conducted during 1922-1999 ( Fig. 1 and references therein) identified 4 species for the Israeli Mediterranean Sea (C. prolifera, C. mexicana, C. scalpelliformis and C. racemosa). From these and other investigations, the importance of seasonality on population dynamics in the Mediterranean Basin, in which high algal densities are apparent during autumn each year, has been underlined (www.algaebase.org; UNEP, 1999, Table 1). In the current study, we aimed to address the diversity and seasonal as well as longitudinal distribution of Caulerpa species along the shores of the Israeli Mediterranean Sea.

Materials and Methods
Caulerpa species were surveyed during the years 2007-2009 from the intertidal and subtidal zones by snorkeling and visually monitoring the rocky and sandy bottoms of 11 field sites. These locations cover ca. 135 km of exposed shoreline, from north to south. The sites were further divided into three geographical areas: northern stations (Akhziv, Haifa, Atlit, Dor, Habonim, Nahsholim, and Sdot yam), central stations (Michmoret, Herzliya, and Bat-yam), and a southern station (Palmahim). For comparison purposes, the sampling sites included those in which Caulerpa species were described in previous studies (see Figure 1 and references therein). Monitoring strips 150 m long and 3 m wide in the intertidal, as well as snorkeling down to 2-3 m depth in the subtidal, both served to verify the presence or absence of Caulerpa at each site. In addition, potholes and tide pools from the intertidal were surveyed for the possible presence of the species. Therefore, mapping of Caulerpa in this study was based on whether the algae were present or not in a defined sampling site. The survey was conducted on a seasonal basis with nearly monthly visits to the sites on days with low tides and calm seas.

Results and Discussions
The goal of our study was to follow the seasonal changes of Caulerpa species that could be related to their geographical distribution. The results showed that only C. mexicana grows at all sampling sites, with C. prolifera and C. scalpelliformis predominant in the northern locations (Fig. 1). All three Caulerpa species prevail during the entire year except for winter, when seaweeds were scarce and hard to find (Table 2). Seasonality was particularly noticeable when mapping during 2007 and 2009. C. racemosa was never observed during the course of this study ( Fig. 1 and Table 2).
Seawater flows from the Atlantic Ocean into the western basin of the Mediterranean Sea, thus buffering water characteristics such as salinity, temperature, nutrient concentrations, and currents (Lascaratos et al., 1999). The eastern basin is largely oligotrophic and exhibits exceptionally low primary productivity (Berman et al., 1984;yacobi et al., 1995) and low nutrient concentrations, particularly during summer (Salihoglu et al., 1990;Krom et al., 1991;Psarra et al., 2000). However, occasional nutrient-rich upwellings during this time of the year have been reported (yacobi et al., 1995). A warm-core eddy south of Cyprus and a cold-core eddy near Rhodes are localized sites with nutrient enrichment that might support high biological activity (yacobi et al., 1995). These eddies create a unique oceanographic condition along the Israeli coast, characterized by fast and strong current velocities in winter and summer, which get slower during spring and autumn, with a general counterclockwise movement of seawater masses in the eastern basin (Oren & Komarovsky, 1961;Pinardi et al., 2003). Therefore, such a unique natural barrier impedes seawater from the west to move and replace seawater masses in the east. Consequently, we argue that the quite different oceanographic conditions for the eastern and western basins may be among the reasons why the invasive C. taxifolia has not yet penetrated into this part of the Mediterranean. Similar temperature barriers may have prevented the spread of C. racemosa var. cylindracea. C. racemosa has not been observed on the Israeli Mediterranean shore for at least two decades, nor was it found during the course of this study.

Conclusions
This survey corroborated the presence of three out of the four Caulerpa species described in previous studies for the Israeli Mediterranean Sea. The invasive C. taxifolia and C. racemosa var. cylindracea were unaccounted for. This study also emphasizes the effect of seasonality on population dynamics, with high and visible biomasses in autumn and ephemeral presence during winter. The present survey should encourage long-term monitoring to assess climate-change effects and biodiversity of seaweeds in the Mediterranean Sea.  Rayss (1941); Edelstein (1960Edelstein ( , 1962; Rayss & Edelstein (1960); Lipkin (1962); Lipkin & Safriel (1971); Ramon (1985); Lundberg (1986Lundberg ( , 1996Einav (1993Einav ( , 1998Einav & Israel (2007).