International Journal of Aquatic Biology (2015) 3(4): 245-257 ISSN: 2322-5270; P-ISSN: 2383-0956 Journal homepage: www.NPAJournals.com © 2015 NPAJournals. All rights reserved Original Article Monsoon effects on the copepod community structure in the Chabahar Bay, Oman Sea Neda Fazeli*1, Rasool Zare2, Seyed Mohammad Bagher Nabavi3, Saeed Sanjani3 1Guilan University, Department of Marine Biology, Rasht, Iran. 2Department of Fisheries, Faculty of Natural Resources University of Tarbiat Modarres, Noor, Iran. 3Khorramshahr University of Marine Science and Technology, Department of Biology, Khorramshahr, Iran. Article history: Received 6 July 2014 Accepted 24 January 2015 Available online 2 5 August 2015 Keywords: Abundance Copepods Diversity Monsoon Oman Sea Abstract: Calanoid, cyclopoid, harpacticoid and poecilostomatoid copepods were investigated over the year at five stations in the Chabahar Bay, Oman Sea. This area is under the influence of the Indian Ocean seasonal monsoons. The samples were collected using vertical plankton tows with 100 µm mesh nets. Copepods were identified into 20 genera and 59 species. Calanoid formed about 15% to 62% and cyclopoid 26% to 39% of total copepod abundance. Harpacticoid constituted about 6% in South West (SW)-monsoon and flourished well in pre (SW)-monsoon, formed 46% of copepod abundance. Poecilostomatoid accounted for approximately 5% to 13% of the total copepods. The most dominant species were Temora turbinata, Paracalanus elegans, Oithona nana and Euterpina acutifrons. The results showed that the species composition and distribution of copepods differed between the monsoon seasons, due to changes in hydrographic conditions. Furthermore, high abundance of small-sized copepods observed in offshore stations. Introduction The Chabahar Bay is a small semi-enclosed bay on the southeastern coasts of Iran (25°17'45"N, 60°37'45"E). This Bay is connected to the Indian Ocean via Oman Sea being influenced by Indian monsoonal winds (Fazeli and Zare, 2011). The Asian monsoon in the Oman Sea is characterized by two distinct seasons separated by two transitional (inter- monsoon) periods: the Southwest (SW) Monsoon from June through September, the Northeast Monsoon (NE) from December through March, the spring transition (pre-monsoon) in April and May and the fall transition (post-monsoon) in October and November (Caulfield, 1990). The Chabahar Bay is one of the five major regions of the Oman Sea providing an ideal breeding ground for many fishes and shell fishes (Wilson, 2000). The bay is located between Chabahar and Konarak. It has 14 km wide and a surface area of 290 km2. The average depth of the bay is 12 m (ranging from 8 to 22 m) (Fazeli and * Corresponding author: Neda Fazeli E-mail address: neda_fazeli200@yahoo.com Zare, 2011; Fazeli et al., 2013). The monsoon has remarkable effects in the region. A peak in chlorophyll-α biomass dominates in the Indian Ocean at SW Monsoon (Yoder et al., 1993). Lower salinity water reaches the sea surface in coastal upwelling that occurs during SW Monsoon along the coast of Oman (Morrison et al., 1998). Water temperatures decrease from 27-29°C at Oman Sea (Caulfield, 1990). During the fall transition, water temperatures cool slowly. Average sea temperatures cool from 28-29°C in October to 27°C in November and oligotrophic conditions slowly return (Caulfield, 1990). The cool, dry northeaster winds that characterize NE Monsoon result in a typical winter time convection/nutrient enrichment scenario in the northern Arabian Sea (Banse and McClain, 1986; Madhupratap et al., 1996). In this season, the monsoon results in a surface water mass with salinity between 35.5-36.5 and temperatures greater than 22°C as Arabian Sea. Water 246 International Journal of Aquatic Biology (2015) 3(4): 245-257 temperatures range from 25°C in April to 29°C in May (Caulfield, 1990). The responses of the zooplankton community structure to seasonal changes in the physical environment have not been analyzed fully yet during 1990s. There is one trend, however, which has been noted in every seasonal study so far: the NE Monsoon is characterized by increased abundance of cyclopoid copepods, such as the genera Oithona and Oncaea, compared with the SW Monsoon. Small calanoid copepods predominate during the SW Monsoon (Madhupratap et al., 1996). In coastal waters of the region, Undinula vulgaris and Paracalanus aculeatus were reproductive in both the NE and SW Monsoons, along with Cosmocalanus darwini and C. plumulosus in the SW Monsoon (Smith et al., 1998). Many studies have described copepod community structure in many parts of Indian Ocean, Arabian Sea and the Persian Gulf (Madhupratap, 1987; Smith, 1995; Savari et al., 2004) but little is known about the copepods of the Chabahar Bay (Fazeli et al., 2010; Fazeli and Zare, 2011; Fazeli et al., 2012; Fazeli and Zare, 2012; Fazeli et al., 2013). Therefore, the main objective of this study is to investigate the spatial and temporal variability in abundance and diversity of copepods and effect of monsoon on species composition of the Chabahar Bay. Materials and Methods Sampling was conducted during four oceanography cruises, including August 2007 (SW Monsoon), November 2007 (post-monsoon), February 2008 (NE Monsoon) and May 2008 (pre-monsoon). Five stations were investigated through the Bay that have been provided in detailed by Fazeli et al. (2013). Four plankton samples were collected vertically at each station twice for counting, using a simple net with a mouth diameter of 30 cm and a mesh size of 100 μm and with a Hydrobios flow meter mounted in the center of the net opening. Samples were preserved immediately in 4-5% formalin, buffered to a pH of 8 with sodium tetra borate (borax), and identified to the lowest taxa. Zooplankton abundance was expressed as ind. m-³ (Somoue et al., 2005). At each station, prior to sampling, the environmental parameters were recorded using a CTD profiler lowered from the sea surface to near the bottom. Seasonal changes of the environmental parameters viz. temperature, salinity and chlorophyll-α during studied period have been provided in detailed by Fazeli et al. (2013). Zooplankton was identified to species level using Chen and Zhang (1974), Nishida (1985) and Conway et al. (2003). A two-Way ANOVA was used to examine a significant of difference in abundance of zooplanktons amongst periods and locations. The Pearson correlation were performed to determine the significance between environmental parameters and copepod genera abundance. Species diversity was calculated using Shannon-Weaver diversity index (Shannon and Weaver, 1963) and species richness (Margalef, 1968). The data were further subjected to hierarchical clustering analyze to identify the similarity between the stations based on the composition. This was calculated as a Bray-Curtis similarity index with log10 (x+1) data using PRIMER version 5.2.8 (Clarke and Warwick, 1994). Results Abundance and composition: Sixty six copepod species belonged to calanoid, cyclopoid, harpacticoid and poecilostomatoid were identified. Copepod density was significantly higher during pre-monsoon (with a total abundance of 3276.81 ind. Figure 1. Total abundance of calanoid, cyclopoid, harpacticoid and poecilostomatoid by season in the Chabahar Bay. 247 Fazeli et al/ Monsoon effects on the copepod community structure in the Chabahar Bay SW M. Post-m. NE M. Pre-m. CALANOID Acartiidae Acartia sp. 0.24 0.37 0.15 0.30 A. longiremis 0.27 0.54 0.32 - Centropagidae Centropages tenuremis 0.91 0.52 12.81 1.14 Clausocalanidae Clausocalanus sp. 0.06 - 0.38 - Eucalanidae Eucalanus subcrassus 0.29 0.57 1.36 - E. sp. 0.11 0.00 0.04 - E. crassus 0.30 0.18 0.04 - E. attenuates 0.05 - 0.05 - E. monachus 0.11 0.07 - - Paracalanidae Acrocalanus longicornis 1.63 0.31 0.30 - A. gracilis 2.86 0.08 0.85 - A. gibber 3.29 0.25 0.33 - A. monachus 1.82 0.12 0.42 0.35 A. sp 1.62 0.73 0.71 0.56 Calocalanus plumulosus - 0.08 0.04 - Paracalanus crassirostris 1.49 2.81 0.34 0.79 P. elegans 4.70 5.60 2.11 0.85 P. aculeatus 2.23 2.29 0.21 0.57 P. denudatus 0.77 0.73 0.22 - P. parvus 0.25 0.19 0.16 0.67 P. sp 0.40 4.95 - 1.45 Pontellidae Labidocera sp. 36.60 0.07 0.50 - Pseudodiaptomidae Pseudodiptomus sp. 0.18 - 6.77 0.90 Temoridae Temora desicaudata 0.11 2.13 0.05 - T. turbinate 1.02 7.66 12.35 7.94 T. stylifera - 0.40 0.23 - CYCLOPOID Oithonidae Oithona aculata 2.59 3.34 2.11 2.21 O. attenuate 4.78 3.71 2.56 1.31 O. brevicornis 0.44 3.36 5.60 1.69 O. plumifera 0.06 1.42 1.80 1.22 O. rigida 4.63 2.65 1.74 1.51 O. simplex 1.61 7.56 1.42 1.04 O. nana 4.72 8.66 13.84 8.63 O. ssp. 7.01 8.95 7.78 9.78 POECILOSTOMATOID CORYCAEIDAE Corycaeidae Corycaeus andrewsi 1.33 0.89 2.07 7.01 C. asiaticus 0.42 0.38 0.32 2.61 C. erythraeus 0.11 0.42 0.36 - C. pacificus 0.96 0.52 - 0.39 C. affinis - 0.33 0.16 0.45 C. dalhi - 0.52 0.49 - C. speciosus - 0.09 0.29 - Table 1. Copepod relative abundance (%) in the Chabahar Bay. 248 International Journal of Aquatic Biology (2015) 3(4): 245-257 m-³) and SW Monsoon (with a mean of 2790.55 ind. m-³) than other seasons (Fig. 1). Among calanoids, the species belonged to the genera of Acartia, Acrocalanus, Calocalanus, Centropages, Clausocalanus, Eucalanus, Labidocera, Pseudodiaptomus, Paracalanus and Temora were the major components of copepod community during SW Monsoon with an average of 1604.13 ± 1318.53 ind. m-³. In post–monsoon, calanoid copepods represented 354.30 ± 43.15 ind. m-³ showing the lowest abundance. Thirty-four calanoid species representing 8 families and 12 genera were identified during four periods in the Chabahar Bay. Some species were observed only in one season in very low abundance (Table 1). Acartia pacifica, A. erythraea, Eucalanus pileatus and E. hyalinus were present only in SW Monsoon. Clausocalanus gracilis, E. miscanthus, Sapphirina gastrica, S. nigromaculata, Calocalanus styliremis, Lucicutia flavicormis and L. gaussae were observed during post-monsoon and disappeared in other seasons. Centropages furcatus, C. furcatus, Pseudodiptomus marinus and C. minor were observed only in NE Monsoon. The dominant calanoid throughout the year were Temora turbinate and Paracalanus elegans. Cyclopoids were presented all year in large numbers with a density of 701.30 ± 75.05 ind. m-³ during post- monsoon. All identified species of cyclopoid belonged to the genus Oithona. The lowest abundance was found during pre-monsoon with an average of 503.30 ± 293.95 ind. m-³. Oithona fallax appeared only in NE Monsoon. The dominant cyclopoid throughout the year was O. nana. Harpacticoids had four genera, including Clytemnestra, Microsetella, Macrosetella and Euterpina. The maximum abundance was observed in pre-monsoon (with an average of 2122.76 ± 994.42 ind. m-³) which comprised 45.81% of total copepod abundance. Harpacticoids had the lowest abundance in post-monsoon with an average of 352.80 ± 22.21 ind. m-³. Clytemnestra scutellata showed the lowest abundance through the year and disappeared in SW Monsoon. The dominant harpacticoids throughout the year were represented by E. acutifrons and Macrosetella gracilis. The species of Poecilostomatoid belonged to the genera Corycaeus, Oncaea and Sapphirina. The highest abundance was found in pre-monsoon with a density of 276.64 ± 75.87 ind. m-³. Corycaeus was present throughout the year but in large numbers in pre-monsoon. The next common poecilostomatoid was Oncaea which it showed maximum abundance during post-monsoon. A small abundance of Sapphirina was found during post-monsoon and NE Monsoon and disappeared entirely during SW Monsoon and pre-monsoon. The dominant SW M. Post-m. NE M. Pre-m. Oncaeidae Oncaea media 0.80 4.88 3.94 - O. venusta 0.93 2.50 0.86 0.35 O. clevei 0.55 1.58 0.21 - O. minuta 0.05 0.90 - 0.52 Sapphirinidae Sapphirina sp. - 0.06 0.44 - HARPACTICOID Clytemnestridae Clytemnestra scutellata - 0.17 1.66 0.96 Ectinostomatidae Microsetella rosea 0.23 0.38 0.49 11.08 Miraciidae Macrosetella gracilis 0.40 3.19 1.02 19.51 Euterpinidae Euterpina acutifrons 5.39 11.82 6.55 14.26 Table 1. Continued. 249 Fazeli et al/ Monsoon effects on the copepod community structure in the Chabahar Bay poecilostomatoid throughout the year were Corycaeus andrewsi and Oncaea media. Temporal and spatial variation of copepods: The variation of copepod genera showed a fluctuation Figure 2. Average copepod genera abundance in the Chabahar Bay during each sampling station. 250 International Journal of Aquatic Biology (2015) 3(4): 245-257 seasonally and spatially (Fig. 2). A significant increase in Acartia was found during SW Monsoon (with an average of 104.73 ± 62.83 ind. m-³) and post-monsoon (88.78 ± 52.33 ind. m-³) compared to other seasons. Acrocalanus (with an average of 355.83 ± 116.06 ind. m-³) and Labidocera (with an average of 5503.76 ± 5492.75 ind. m-³) also showed highest abundance during SW Monsoon. In post-monsoon, Paracalanus (499.01 ± 88.73 ind. m-³), Oncaea (366.55 ± 211.09 ind. m-³) and Eucalanus (65.64 ± 18.84 ind. m-³) showed the highest abundance. A significant increase of Euterpina was found during post-monsoon and NE Monsoon. NE Monsoon showed the maximum abundance of Temora (1866.26 ± 485.84 ind. m-³), Pseudodiaptomus (933.15 ± 292.28 ind. m-³), Clausocalanus (98.83 ± 40.20 ind. m-³) Calocalanus (86.09 ± 151.79 ind. m-³), Centropages (1888.40 ± 795.48 ind. m-³) and Sapphirina (66.27 ± 46.29 ind. m-³). Macrosetella gracilis and M. rosea showed a high abundance during NE Monsoon compared to other periods. In pre-monsoon, the maximum abundance of Corycaeus (382.64 ± 124.77 ind. m-³) was found. Clytemnestra scutellata showed a higher abundance during pre-monsoon and NE Monsoon. Spatial variations in abundance of copepod are shown in Figure 2. Among calanoids, we observed the maximum average abundance of Eucalanus and Paracalanus at station 1, Centropages and Clausocalanus at station 2, Pseudodiaptomus at station 3, Temora, Acartia and Acrocalanus at station 4. In Pontellidae, Labidocera showed a higher abundance in station 5. Calocalanus was observed only at stations 2 and 5. Among cyclopoids, the maximum abundance of Oithona was found at station 2. Among poecilostomatoids, Oncaea showed a higher abundance at stations 1 and 2, whereas Sapphira showed the maximum abundance at station 3. Corycaeus showed the highest abundance at stations 3 and 4. Among harpacticoids, a low abundance of E. acutifrons was found at station 2, while M. gracilis and M. rosea showed a higher average abundance at station 1. A higher abundance of C. scutellata was found in stations 3 and 4 (Fig. 3). Figure 4 shows cluster analysis for calanoid, cyclopoid, harpacticoid and poecilostomatoid to investigate similarities between stations based on density data. The results indicated the presence of two groups; station(s) in group I separated from other stations in group II. In calanoids, the highest similarity of stations was observed in stations 2 and 3. Stations 1 and 4 showed the maximum similarity of cyclopoids density. In harpacticoids, the highest similarity of stations was observed in stations 2 and 4. In poecilostomatoids, the highest similarity of stations was presented in stations 1 and 2. Species diversity and richness: In SW Monsoon, calanoid formed by the relatively high diversity Figure 3. Average density of dominate copepod species in the Chabahar Bay. 251 Fazeli et al/ Monsoon effects on the copepod community structure in the Chabahar Bay index and species richness (2.28/2.60), while a low value was observed in pre-monsoon (1.01/0.44) (Table 2). The highest and lowest cyclopoid species diversity and richness were observed in NE Monsoon and pre-monsoon, respectively. In poecilostomatoids, the highest and lowest species diversity and richness were observed during post- monsoon and pre-monsoon, respectively. Harpacticoid species diversity and richness were relatively low during four periods. The highest species diversity and richness of harpacticoid was recorded in pre-monsoon (0.97/0.28) and the lowest in SW Monsoon (0.36/0.15). Environmental parameters and zooplankton: A Pearson product correlation was calculated to examine whether any relationship existed between copepod genera and environmental parameters in the Chabahar Bay. The results are presented in Table 3. Discussion NE Monsoon consists of the moderate wind-driven mixing, a net flux of heat from the ocean to the Figure 4. Cluster analyses showing similarity of stations during monsoonal seasons based on calanoid, cyclopoid, harpacticoid and poecilostomatoid density in the Chabahar Bay. 252 International Journal of Aquatic Biology (2015) 3(4): 245-257 atmosphere, and elevated evaporation (Wiggert et al., 2000). Apparently, nutrients transported via this wintertime mixing fuel the subsequent spring phytoplankton bloom as defined by the appearance of the chlorophyll-α in the Chabahar Bay which confirmed the record of Kumar and Prasad (1999) in Arabian Sea. High temperature was observed in SW Monsoon result in high sunlight. In post-monsoon and NE Monsoon, temperature decreased throughout the Bay by decreasing sunlight. Salinity did not vary significantly during warm and cold season as evaporation is high during cold season (Wiggert et al., 2000). Water temperature, chlorophyll-α and salinity in the Chabahar Bay were similar to those of Caulfield (l990) in Oman Sea and Arabian Sea. The variation of species among the four sampling seasons is apparently influenced by monsoon (Chen, 1992). In summer, by the prevailing SW Monsoon some species e.g., A. gibber, A. gracilis, Labidocera sp., O. rigida and O. attenuate were dominant. Labidocera sp. was the most common species (36%) in this season but showed a low abundance during post-monsoon and NE Monsoon, and disappeared during pre-monsoon. Acrocalanus gibber and A. gracilis were abundant during SW Monsoon but decreased during other seasons which confirmed the record of Vengadesh et al. (2009). Trophic resources may play an important role in controlling of Acrocalanus in tropical environments (Gusma and Mckinnon, 2009). It seems that temperature play a major role in abundance of O. rigida and O. attenuate as they were positively related to temperature. In autumn, the prevailing post-monsoon declined, the copepod abundance was observed that it can be explained due to decrease in chlorophyll-α concentrations. The Chabahar Bay seems to have an SW M.(H/D) post- m.(H/D) NE M. (H/D) Pre-m.(H/D) CALANOID Station 1 2.73(3.83) 2.36(2.46) 2.51(2.61) 1.33(0.46) Station 2 2.68(3.01) 2.82(2.50) 1.60(0.97) 1.85(0.92) Station 3 2.22(1.89) 1.61(0.65) 1.56(0.56) - Station 4 2.66(2.66) 2.39(1.84) 1.66(1.04) 1.89(0.83) Station 5 1.13(1.63) 0.59(0.86) 1.71(1.23) - Mean 2.28(2.60) 1.95(1.66) 1.80(1.28) 1.01(0.44) CYCLOPOID Station 1 1.62(0.75) 1.70(0.83) 1.77(0.80) 0.83(0.22) Station 2 1.89(0.93) 2.02(0.77) 1.78(0.77) 1.89(0.74) Station 3 1.68(0.59) 1.59(0.69) 1.64(0.73) 1.38(0.50) Station 4 1.58(0.70) 1.62(0.70) 0.91(0.44) 0.69(0.14) Station 5 1.50(0.48) 1.26(0.49) 1.50(0.75) - Mean 1.64(0.69) 1.63(0.69) 1.52(0.69) 0.95(0.32) HARPACTICOID Station 1 0.84(0.29) 0.97(0.38) 0.35(0.12) 0.89(0.20) Station 2 0.86(0.34) 0.91(0.26) 1.20(0.37) 0.74(0.22) Station 3 - 0.10(0.12) - 1.18(0.37) Station 4 0.11(0.12) 0.47(0.25) 0.54(0.14) 1.21(0.36) Station 5 - 0.44(0.13) 1(0.37) 0.86(0.25) Mean 0.36(0.15) 0.57(0.22) 0.61(0.20) 0.97(0.28) POECILOSTOMATOID Station 1 1.67(0.85) 2.16(1.43) 1.80(0.99) 0.63(0.16) Station 2 1.39(0.58) 1.66(1.27) 0.69(0.19) 0.98(0.40) Station 3 - 2.07(1.15) 1.55(0.63) 0.91 (0.24) Station 4 1.37(0.58) 2.01(1.39) - 0.98(0.27) Station 5 0.18(0.28) 0.63(0.18) 0.91(0.63) 0.37(0.13) Mean 0.92(0.45) 1.70(1.08) 0.99(0.48) 0.77(0.24) Table 2. Diversity indices (H) and species richness (D) of calanoid, cyclopoid, harpacticoid and poecilostomatoid. 253 Fazeli et al/ Monsoon effects on the copepod community structure in the Chabahar Bay oligotrophic condition during this season similar to Arabian Sea (Baars et al., 1998). Temora turbinate, O. simplex, O. media and M. gracilis were the most common species in this season. Centropages tenuremis, T. turbinate, O. media and Pseudodiptomus sp. were dominant during winter by the prevailing NE Monsoon. Entrainment of nutrients into the upper layer by winter cooling was caused producing phytoplankton blooms in this season similar to those of the Gulf of Aden (Baars, 1998) and Arabian Sea (Kumar and Prasad, 1999). On the other hand, abundance of C. tenuremis, T. turbinate and Pseudodiaptomus sp. was negatively related to temperature. It was stated that there is a negative relationship between nutrients and temperatures below 22°C. High concentrations of the phosphates and low temperatures allow development of different plankton compartments (Roy, 1992). The joint effect of high nutrients and low temperature can result in high abundance of some opportunistic species such as T. turbinate (Madhupratap, 1987) which is the major species of Temora in the Chabahar Bay. They almost flourish in high chlorophyll-𝛼 concentration (Madhupratap, 1987). This observation confirmed those of Hsieh and Chiu (2002), Hwang and Wong (2005) and Shih and Chiu (1998) along coast of Taiwan. In spring, by the prevailing pre-monsoon C. andrewsi, Microsetella rosea and M. gracilis were dominant, while they decreased significantly during other seasons. A high abundance of harpacticoid was remarkable during this season. It can be explained by their adaptive strategy to overcome the harsh mechanical disturbances which occur in pre- monsoon. These copepods are always reproductively active, and tolerant to harsh climatic regime (Mantha et al., 2012). Paracalanus elegans, T. turbinate, O. nana, E. acutifrons were occurred in all sampling seasons. The high abundance of these species during a year might be due to high tolerance to temperature and salinity variation (e.g., O. nana, Nishida, 1985), reproductive adaptive natures (e.g. E. acutifrons, Mantha et al., 2012) and opportunistic behavior (e.g., T. turbinate, Madhupratap, 1987). Similar to the present result, Paracalanus spp. and T. turbinate were the most dominant copepods species in Mida Creek (Mwaluma et al., 2003). Also Paracalanus, Oithona, Microsetella and Oncaea were dominant in Malaysia (Nakajima et al., 2008). In this study, the high abundance of small-sized copepod such as O. media, P. elegans, T. turbinate and O. nana were observed in offshore samples which confirmed those of Rezai et al. (2004) in the Strait of Malacca. These species showed positive relationship with depth. The results showed a Chl(a) Salinity Temperatu re Depth P. elegans 0.15 -0.42* -0.14 0.49* A. gibber A.gracilis -0.27 -0.25 -0.23 -0.37 -0.46* 0.29 -0.01 0.51* T. turbinate 0.31 0.01 -0.62** 0.47* Pseudodiaptomus sp. 0.23 -0.19 -0.61** -0.22 Centropages tenuremis 0.19 -0.16 -0.46* -0.10 Labidocera sp. -0.13 -0.01 0.31 -0.21 O. nana 0.21 -0.31 -0.63** 0.65** O. attenuate 0.23 0.23 0.67** 0.23 O. rigida -0.28 0.23 0.53* 0.23 Corycaeus andrewsi 0.28 0.53* 0.29 -0.39 Oncaea media 0.05 -0.39 -0.32 0.55* Euterpina acutifrons -0.07 0.37 -0.28 -0.55* Macrosetella gracilis -0.05 -0.25 -0.52* 0.30 Microsetella rosea -0.17 -0.21 -0.46* 0.24 Table 3. Pearson correlation of major environmental parameters and major species density (‘*’ significant at 0.05 level; ‘**’ significant at 0.01 level) 254 International Journal of Aquatic Biology (2015) 3(4): 245-257 negative correlation between E. acutifrons and depth. This species is a near-shore species (Jitchum and Wongrat, 2009; Russell et al., 1996; Somoue et al., 2005) which showed higher abundances in the Chabahar Bay when salinity was the highest similar to those of Moreira (1975). From SW Monsoon to pre-monsoon, the calanoid and cyclopoid species diversity and richness tended to be lower, reflecting lower structured communities. The highest richness of harpacticoid was observed in pre-monsoon suggesting their high population density in this season. During post-monsoon, species richness of poecilostomatoid increased along with increasing population density. Spatially, copepods showed higher species diversity and richness in offshore stations. A higher diversity in offshore stations was due to stable environmental conditions prevailing which permitted plankton community to increase diversify which confirmed those of Sivasamy (1990) and Shanthi and Ramanibai (2011) in northern Arabian Sea. 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All rights reserved چکیده فارسی عمان دریایچابهار، خلیج پاروپایان جوامع ساختار بر مونسون اثرات 3سنجانی سعید ،3نبوی باقر محمد ،سید 2زارع رسول ،1فاضلی ندا .ایران رشت، گیالن، دانشگاه یا،شناسی درزیست گروه1 .ایران نور، مدرس، تربیت دانشگاه طبیعی، منابع دانشکده شیالت، گروه2 .ایران خرمشهر، خرمشهر، دریایی فنون و علوم دانشگاه ،شناسیزیست گروه3 چکیده: مدت طی عمان ریاید، چابهار خلیج ایستگاه پنج در هاپوسیلوستوماتوئید و هارپکتیکوئید سیکلوئید، کاالنوئید،شامل پاروپایان مطالعه، این در با النکتونیپ تور از استفاده با هانمونه. باشدمی هند اقیانوس مونسونفصلی بادهای تاثیر تحت منطقه این. گرفتند قرار بررسی مورد سال یک و درصد 22 تا 19 کاالنوئیدها. شدند شناسایی گونه 95 و جنس 21 از پاروپایان. شدند آوریجمع عمودی طور به و میکرون 111 چشمه فروانی. بود درصد 2 حدود تابستانه مونسون در هارپکتیکوئیدها فراوانی. دادندمی تشکیل را پاروپایان کل فراوانی درصد 35 تا 22 سیکلوئیدها درصد 13 تا 9 تقریباً پوسیلوستوماتوئیدها فراوانی. داد اختصاص خود به را پاروپایان کل فروانی درصد 62 و یافت افزایش بهاره مونسون در آنها Euterpina و Temora turbinata ، Paracalanus elegans ، Oithona nana شامل غالب هایگونه. بود پاروپایان کل acutifrons رایطش تغییر از ناشی که باشدمی متفاوت مونسون مختلف فصول در پاروپایان پراکنش و ترکیب که داد نشان نتایج. بودند .بود لساح نزدیک های ایستگاه از بیشتر ساحل از دور هایایستگاه در کوچک پاروپای هایگونه فراوانی این بر عالوه. باشدمی هیدروگرافیک .عمان دریای مونسون، تنوع، پاروپایان، فراوانی، :کلمات کلیدی