Indian Journal of Geo-Marine Sciences Vol. 41(1), February 2012, pp. 61-69

Temporal and spatial variations in the species composition, distribution, and abundance of in mangrove creek area along the Karachi coast, Pakistan

Farah Naz1, Naureen Aziz Qureshi2, Noor Us Saher*1 1Centre of Excellence in Marine Biology, University of Karachi, Karachi 75270, Pakistan 2Department of Wildlife and Fisheries, Government College University Faisalabad, Allama Iqbal Road, Faisalabad 38000, Pakistan [E. mails: [email protected] , [email protected], *[email protected]]

Received 13 January 2011; revised 22 May 2011

Among different groups of zooplankton collected from Korangi-Phitti mangrove creek area, copepods contributed maximum numerical abundance up to 68% and 75% at S1 and S2, respectively. Twenty one species of , pertaining to fourteen genera and thirteen families were identified from the sample, Difference in diversity of copepod species among seasons with highest density in post monsoon at both stations was recorded. Acrocalanus longicornis, Paracalanus sp., Acartia sp., sp., Oncea sp. and Coryceaus sp. were observed as the dominant and abundantly found copepod species throughout the study period. The highest diversity and equitability was observed in pre monsoon at both stations followed by north east monsoon and south west monsoon. Biomass and species diversity are in inverse relationship.

[Keywords: Temporal, Spatial, Copepod, Seasons, Mangrove, Karachi coast].

Introduction Pakistan coastal waters are not many and primarily Copepods are the most numerous taxa (55%-95%) deals with taxonomic work from offshore waters of in most sea areas among various taxa Pakistan15. The review of previous detailed work occurring as metazooplankton in the marine illustrates Calanoid-copepods comprises of 5 super ecosystem1,2. Copepods are involved in the turnover families, 18 families, 30 genera and 55 species in the of nutrients and regulation of phytoplankton FAO area No.51, off shore and in shore bordering populations on which they feed. As part of the food Pakistani waters16. Species of the general groups web, they contribute to the transfer of energy and Calanoids, Harpacticoids, Cyclopoids and organic matter from the primary producers to the main Poecilostomatoids were collected during two short consumers of the aquatic system, including various cruise NASEER 1 1992, and NASEER 4 1994, 1995, fish species of commercial importance2-7. Copepods 1997a and b from the north Arabian Sea17. Previous are also known to consume large quantities of recorded species of copepods from inshore and bacteria8, phytoplanktons9 and organic detritus10. offshore waters of Pakistan have been reviewed18. From the larval stage to the adult stage; they Studies on copepods from inshore water of constitute a major component in the diet of numerous Karachi coast were rare. Present study investigates zooplanktophage fish11. Their abundance and the abundance, distribution, diversity, species distribution are known to be influenced by composition and recruitment source of copepods in hydrographic conditions and they have been mangrove creek area along the Karachi coast. suggested as good biological indicator species for water masses5,12,13. Few studies have been carried out Materials and Methods on the copepods of the Northern Arabian Sea. Nine Karachi coast in the southeast has Korangi and species of Calanoid copepods were identified and Phitti creeks, (24°68’N, 67°15’E) which represent described in the inshore creeks water of Karachi characters of the Indus delta. The Phitti-Jhari-Kadiro coast14. Published account of copepods from the creek acts as the main waterway connected with the ———————— open sea at the southwestern end. Two stations were *Corresponding author selected in the Phittti-Jhari creek (Fig. 1). The first 62 INDIAN J. MAR. SCI., VOL. 41, NO. 1, FEBRUARY 2012

Fig. 1—Map of the study area showing Korangi-Phitti creek and two sampling stations, Rato Kot (S1) and Phitti creek (S2). station (S1) was considered as the shallow station from each station were preserved on board with 4% with an average depth of 5-6 m near Rato Kot buffered formalin in large mouth polyethylene jars for mangroves and the second station (S2) was nearly later analyses. in the middle of Phitti-Jhari creek in the south west Surface water samples at each station were with an average depth of 11.3 m (Fig. 1). collected with a clean bucket and were analyzed for Sampling of mesozooplankton was regularly hydrographic data simultaneously at each sampling conducted at monthly intervals from both stations event. Temperature was measured by hand held during January 1998 to December 1998. The standard thermometer. The salinity was measured with an plankton net of 234 µm mesh size, with a mouth optical refractometer (with correction of 1 ppt). diameter of 0.5 m was used. A flow meter (General In the laboratory, plankton samples were checked Oceanic Model 2030R) was mounted at the center of to remove any debris like floating twigs, mangrove the net opening to measure the volume of water leaves, seaweeds small pieces of wood or plastic and filtered by the net. Sub-surface horizontal haul was other small garbage and any material exceeding 2 mm made and the net was towed for 5 minutes at a or greater dimensions from the samples prior to uniform speed of 2 knots in a circular path to ensure sample analysis. Sub samples were obtained to that the same water mass was sampled. The samples determine numerical density and biomass using a NAZ et al.: COPEPODS IN MANGROVE CREEK OF KARACHI 63

Folsom plankton splitter. Biomass was estimated by values were registered during September (30.9°C and the product of density (indviduals/1000 m3). 30.2°C) at S1 & S2, respectively and minimum Copepods were counted and identified up to temperature during January at both stations. High possible taxonomic level i.e. generic and species level variability was observed in salinity with peaks in under a stereoscopic microscope with the help of January-February and minimum in August at both available identification key16. stations (Table 1). The significant difference was All parameters studied and estimated were observed in temperature (F3,23 = 449.56, P<0.001) statistically analyzed (Minitab 11.12 version). The among seasons. word “significant” or “statistically significant” means Copepods were the most abundant group amongst that differences were detected at 0.05 percent level of the mesozooplankton in the collected sample. The probability. For statistical analyses and to observe the species composition and abundance of copepods seasonal shifts in distribution, abundance and varied between stations and among seasons in Phitti community structure, data were grouped into seasons creek (Table 2). The annual mean abundance, species following north east monsoon (December to number, and diversity of copepods were found to be February), pre-monsoon (March to May), south comparatively higher at S2 as compared to S1. The 6 west monsoon (June to August) and post-monsoon mean annual abundance of copepods was (1.55 × 10 (September to November)19. ± 1.04 × 106) and (4.52 × 106 ± 6.33 × 106)/1000.m3 at The species diversity was calculated using the S1 and S2, respectively. The annual average of information function (H) and evenness (J) with percent abundance or frequency of copepods was natural logs20,21. Simpson's index and Species richness 68.25% and 75.01% at S1 and S2, respectively. were also calculated19,22. Completely randomized Maximum numbers of copepods occurred in the design (CRD) analysis of variance (ANOVA) was month of January (97.35%) at S1 and (93.54%) at S2 used to test all parameters for differences at station in February and minimum numbers of copepod level and the levels of seasons. Density was log (x+1) occurred in the month of March 34.83% and 35.70% transformed after testing for heterogeneity of at S1 and S2, respectively. variances. Pearson correlation coefficient was used to The highest densities of copepods were in January 3 3 determine the relationship between total abundance (3287.34/1000 m ) at S1 and October (16907.84/1000 m ) of copepods with all ancillary environmental at S2 (Figure 2). The lowest densities of copepods 3 hydrographic parameters including temperature, were in July (206.91/1000 m ) at S1 and September 3 salinity and diversity indices. (396.48/1000 m ) at S2. The high seasonal density of copepods was found in north east monsoon and post Results monsoon at S1 and S2, respectively (Table 2). Seasonal variations were observed in water The diversity index of copepod species was 0.394 temperature and salinity as the water temperature ± 0.213 at S1 and 0.421 ± 0.259 at S2. The highest ranged between 19.5 and 30.9°C and the salinity diversity and equitability of copepod occurred during ranged between 32 and 47 ppt. Maximum temperature pre monsoon at both stations and the diversity was

Table 1—Annual mean and standard deviation of (mean ± SD) (F is the statistics and P is the probability level) of temperature, salinity, pH, Eh, suspended sediments, transparency, dissolved oxygen collected from Korangi and Phitti creek mangrove areas during January to December 1998. Variables Mean±SD Mean±SD F P Temp. Air (°C) 31.008 ± 3.092 30.7 ± 3.336 3.73* 0.033 Temp. Water (°C) 27.02 ± 3.53 27.2 ± 3.334 49.56*** 0.000 pH 7.565 ± 0.454 7.662±.351 5.04** 0.012 Eh (mv) 65.57 ± 4 .72 59.43 ± 0.351 9.74*** 0.007 -1 DO (mg O2 l ) 4.79 ± 0.3286 4.431 ± 0.438 4.68** 0.016 Salinity (ppt) 35.83 ± 4.53 35 ± 2.045 2.98 0.063 Suspended Sediments (mg l-) 0.6689 ± 0.0534 0.0575 ± 0.0412 6.97** 0.003 Transparency (m) 0.9883 ± 0.2983 1.145 ± 0.365 3.06 0.059 *=Significant at P<0.05 **=Significant at P<0.005 ***=Significant at P<0.001 64 INDIAN J. MAR. SCI., VOL. 41, NO. 1, FEBRUARY 2012

Table 2—Seasonal variation (mean ± SD) of Diversity, Equitability, Species richness, Dominance, Abundance and number of observations (N) of the copepods collected from Korangi and Phitti creek mangrove areas during January to December 1998. Seasons Diversity Equitability Species richness Dominance Abundance (106) / 1000m3 N Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD Station 1 North east monsoon 0.46 ±0.1301 0.53± 0.132 7.183 ± 0.586 0.433 ± 0.197 2.29 ± 8.223 3 (0.33-0.59) (0.39-0.65) (6.84-7.86) (0.3-0.66) (1493155-3136364) Pre monsoon 0.61 ± 0.1709 0.63 ± 0.13 9.17 ± 2.30 0.37 ± 0.1249 1.66 ± 1.37 3 (0.43-0.77) (0.48-0.71) (7.83-11.83) (0.27-0.51) (84851-3242517) South West monsoon 0.37 ± 0.1114 0.46 ± 0.0503 6.50 ± 2.48 0.443 ± 0.217 4.18 ± 2.07 3 (0.27-0.49) (0.41-0.51) (3.87-8.81) (0.21-0.640) (240288-645524) Post monsoon 0.13 ± 0.1097 0.17 ± 0.1418 7.51 ± 2.90 0.84 ± 0.043 1.90 ± 7.09 3 (0.01-0.22) (0.01-0.28) (5.83-10.85) (0.81-0.89) (1202536-2594545) Station 2 North east monsoon 0.370 ± 0.252 0.437 ± 0.303 6.8467 ± 0.0058 5.1 ± 0.286 3.34 ± 1.91 3 (0.14-0.640) (0.16-0.760) (6.84-6.85) (0.280-0.830) (1592040-5384925) Pre monsoon 0.743 ± 0.076 0.77 ± 0.0964 9.183 ± 1.163 0.237 ± 0.066 3.66 ± 2.01 3 (0.66-0.81) (0.66-0.84) (7.840-9.86) (0.18-0.31) (1349152-4958363) South West monsoon 0.3267 ± 0.125 0.0413 ± 0.13 6.5 ± 2.30 0.663 ± 0.1701 1.39 ± 1.11 3 (0.24-0.47) (0.27-0.52) (3.84-7.83) (0.43-0.77) (506302-2645673) Post monsoon 0.243 ± 0.254 0.310 ± 0.331 5.8467 ± 0.0153 0.667 ± 0.276 9.66 ± 1.24 3 (0.020-0.520) (0.02-0.670) (5.83-5.86) (0.36-0.87) (648576-23831851) A total of twenty one species of copepods pertaining to fourteen genera were identified (Table 4). The most relatively abundant genera in order of dominance were Acrocalanus longicornis and Paracalanus aculeatus and other species observed were Temora discaudata, Temora turbinita, Acartia amboinensis, Oithona plumifera, Centrophages dorsispinatus, C. furcatus, C, orsinii, Labidocera acuta, L. minuta, Oncaea media, Eucalanus crassuss, E. pileatus, E. subtenuis, Corycaeus acuta, C. minuta, Scottolana longipes and Pleuromamma indica (Fig. 5). Fig. 2—Variations in density of copepods community collected Two species of genus Temora were collected in each from Rato Kot (S1) and Phitti creek (S2) mangrove area during month from both stations with the exception of January to December 1998. October at S1 and September at S2. Acrocalanus found to be the lowest during post monsoon (Table 2). longicornis and Paracalanus aculeatus alternately Diversity index showed no significant difference dominated in certain months forming 20 % to 90 % in between stations but was significant among seasons abundance and were absent in others (Fig. 5). At S1, (F3,23 = 9.01, P<0.005). The mean equitability was Acrocalanus longicornis was abundant from January 0.448 ± 0.206 and 0.480 ± 0.271 at S1 and S2, to March, nearly disappeared in April, reappeared in respectively. There were no significant differences May and increased in number during August, where in equitability and dominance between stations they contributed nearly 100% and 90% in September but the difference was significant among seasons (Fig. 5). In October this species was completely (F3,23 = 6.04, P<0.05), (F3,23 = 5.74, P<0.05), replaced by Paracalanus aculeatus (95% in October) respectively (Table 3, Fig. 3). The highest dominance and the percent abundance decreased till Paracalanus was observed in post monsoon season and there aculeatus composition become 20% in December appears an inverse relationship between diversity and (Fig. 5). Paracalanus aculeatus formed nearly 30% in dominance (Table 2). Diversity were high (positively (April and May) of the total copepods collected when correlated) with equitability and species richness and the percent abundance of Acrocalanus longicornis negatively correlated with dominance and abundance was quite low or absent. At S2, nearly similar of copepods (Fig. 4). distribution of these two species was observed, with NAZ et al.: COPEPODS IN MANGROVE CREEK OF KARACHI 65

Table 3—Seasonal variation (mean ± SD) of Diversity, Equitability, Species richness, Dominance, Abundance (Individuals / 1000cm3) and no of observations (N) of the copepods collected from Korangi and Phitti creek mangrove areas during January to December 1998. Parameters Sum of square df Mean square F Significance Diversity Station 0.00427 1 0.06720 0.15 0.699 Seasons 1.74442 0.5643 3 0.24814 9.01* 0.001 Station*Season 0.4473 3 0.1881 0.68 0.575 16 0.44073 Total 1.24585 23 Equitability Station 0.00735 1 0.00735 0.21 0.655 Seasons 0.64290 3 0.21430 6.04* 0.006 Station*Season 0.06828 3 0.02276 0.64 0.599 0.56767 16 0.03548 Total 1.28620 23 Dominance Station 0.00135 1 0.00135 0.04 0.851 Seasons 0.63575 3 0.21192 5.74** 0.007 Station*Season 0.11255 3 0.03752 1.02 0.411 0.59033 16 0.03690 Total 1.33998 23 Species richness Station 1.475 1 1.475 0.44 0.517 Seasons 27.781 3 9.260 2.76 0.076 Station*Season 2.829 3 0.943 0.28 0.383 53.711 16 3.357 Total 85.795 23 Abundance Station 451398 1 451398 0.31 0.585 Seasons 1260552 3 420148 0.29 0.832 Station*Season 5290132 3 1763377 1.21 0.337 23237998 16 1452375 Total 30240080 23 *=Significant at P<0.05 **=Significant at P<0.005 ***=Significant at P<0.001 slight variations in percent abundance (Fig. 5). All other species of copepods were observed occasionally in different months. The average percent abundance of copepod species showed that Acrocalanus longicornis was by far the most abundant species collected (77% to 45% at S1 and S2, respectively). This corresponded with high densities of Acrocalanus longicornis found at both stations. Paracalanus aculeatus, Acartia spp., Temora spp., and Eucalanus spp. were the other most commonly occurring species at both stations (Fig. 3). Temora spp. Acartia spp., and Lebidocera sp. showed positive correlation with temperature and salinity (P<0.05).

Discussion Spatial and temporal variations were observed in the distribution and abundance of copepods during the general descriptive studies on zooplankton from the two mangrove creek areas. Many environmental factors may influence the abundance and distribution Fig. 3—Seasonal variations in Diversity (H), Equitability (H), of 23 23,24 copepods community collected from Rato Kot (S1) and Phitti of copepods like temperature , salinity , dissolved 25,26 25,27 23,28 creek (S2) mangrove area during January to December 1998. oxygen , food , water circulation, tides and 66 INDIAN J. MAR. SCI., VOL. 41, NO. 1, FEBRUARY 2012

predation23. It is also known that the vertical high seasonal density of copepods found in north east distribution of copepods may be limited by low monsoon and post-monsoon at both stations may be oxygen26. However, in present study no significant attributed to the enrichment of the coastal waters with relationship was observed between the environmental nutrients caused by heavy rainfall, and river runoff, parameters i.e. temperature, salinity, pH and distance from the shore, and sediments discharge abundance of the copepod species, which may have (land drainage). In this investigation, we found that been due to the well-mixed water at both stations. the copepods were affected by the seasonal changes Variations were observed in copepods species as drop in zooplankton biomass was observed from composition and distribution in creek system; June to September in Phitti creek. Differences in however, abundance of copepods between station and mean population abundance at both stations may have among seasons was not significantly different. The been a result of tidal influences due to south west monsoon related changes in hydrographic parameters; increased turbidity and repeated changes in water masses or it could be the result of predation. The predation is another factor that may complicate the interpretation of population dynamics of copepods. The size of a population depends not only on availability of food and abundance of predators but also upon the dynamics of its physical environment, which influence the feeding efficiency, susceptibility to predation, transport and recruitment success29. Diversity was positively correlated with the equitability and species richness and negatively correlated with dominance and abundance of

Fig. 4—Linear correlation between diversity and equitability of copepods. Equitability and species richness were the copepods collected from Korangi and Phitti creek mangrove negatively correlated with dominance and abundance areas during January. to December 1998. of copepods. Similar type of results was obtained with

Table 4—Copepod species and their relative abundance in Korangi and Phitti creek area near the Karachi coast during January to December 1998. No. Family Species Percent relative Percent relative abundance S1 abundance S2 1 Paracalanidae a. Paracalanus aculeatus 65.65 71.56 b. Acrocalanus longicornis 2 Euchaetidae a. Euchaeta marina 0.86 0.26 b. Euchaeta rimana 3 a. Temora turbinata 13 5.26 b. Temora discaudata 4 Metridinidae a. Pleuromamma indica 0 0.28 5 Centropagidae a. Centropages furcatus 0.97 0.93 b.Centropages dorsipinatus c. Centropages orsinii 6 Acartiidae a. Acartia amboinensis 8.70 10.38 7 Oithonidae a Oithona plumefera 1.96 2.4 8 Oncaeidae a. Oncaea media 1.07 3.60 9 Corycaeidae a. Corycaeus acuta 4.59 3.28 b. Corycaeus minuta 10 Ponellidae a. Labidocera acuta 0.47 0.12 b. Labidocera minuta 11 Calusocalanidae a. Calusocalanus furcatus 0.70 0.7 12 Eucalanidae a. Eucalanus crassuss 0.01 1.76 b. Eucalanus pileatus c. Eucalanus subtenuis 13 Canuellidae Scottolana longipes 1.46 1.74 NAZ et al.: COPEPODS IN MANGROVE CREEK OF KARACHI 67

Fig. 5—Percent composition of copepod community collected from Rato Kot (S1) and Phitti creek (S2) mangrove area during January to December 1998. regard to ecological indices22. Species diversity is along the Karachi coast has been studied31. Bimodal reported to be influenced by the functional relationship distribution and the highest biomass values were between the tropic levels. The amount of predation observed in creek area between August and greatly affects the diversity of prey population22. December33. The plausible reasoning with reference The representatives of fourteen genera were to this seasonal pattern observed in the distribution of identified during the present study and these copepod copepods species does not discuss if they were of species showed seasonal distribution. During the pre local origin or some of these species have moved and post monsoon period 16 species of copepods that inshore due to advection30,31. Observed changes in the contributed 63 to 90% of total zooplankton were species dominance support the effect of climatic identified along the coast of Pakistan and classify as factors on the distribution and abundance but would an epipelagic and oceanic species15. Seasonal pattern not control the absolute density that is very likely and species distribution from the coastal waters controlled by inter specific competition32. off Saurashtra with 12 species were identified30. The copepod community in the Phitti creek Distribution of copepod species was with the season system is mainly characterized by the numerical 68 INDIAN J. MAR. SCI., VOL. 41, NO. 1, FEBRUARY 2012

predominance of the representative of family 6 Parsons T R, Takahashi M & Hargrave B, Biological Paracalanidae (Paracalanus aculeatus, Acrocalanus Oceanographic processes. 3rd ed., Pergamon press (Oxford), New York, 1984, 332 pp. longicornis), Temoridae (Temora turbinata, Temora 7 Uye, S I, & Sano, K, Seasonal variations in biomass, growth discaudata), and Acartiidae (Acartia amboinensis). rate and production rate of the small cyclopoid copepod The average percent abundance of copepod species Oithona davisae in a temperate eutrophic inlet, Mar. Ecol. showed that Acrocalanus longicornis was by far the Prog. Ser., 163: 1998, 37-44. 8 Wroblewski, J S, A simulation of the distribution of Acartia most abundant species collected (77% to 45% at S1 clausi during the Oregon upwelling, August 1973, J. Plank. and S2, respectively). Paracalanus aculeatus, Acartia Res., 2: 1980, 43-68. amboinensis, Temora discaudata and Eucalanus 9 Calbet, A, Landry, M R, & Scheinberg, R.D, Copepod were the other most commonly occurring species at grazing in a subtropical bay: species-specific responses to a both stations. midsummer increase in nanoplankton standing stock, Mar. Ecol. Prog. Ser., 193: 2000, 75-84. The Paracalanus aculeatus and Acrocalanus 10 Steinberg, D K, Pilskain, C H, Silver, M W, Contribution of longicornis are the phytophagus genera and are zooplankton associated with detritus to sediment trap common in the estuaries, creek and productive coastal swimmer carbon in Monterey Bay, California, U.S.A, Mar. water,6,24,27,34. The genus Acartia comprises over Ecol. Prog. Ser., 164: 1998, 157-166.

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